The conversion of natural lands to agriculture continues to be a threat, as blocks of suitable habitat continue to be converted to irrigated agriculture (Kelly et al. 2005, p. 65, Figure 2). Although analyzed at a broader scale, one study estimated a 37% loss of remaining grassland habitat across the Central Valley by 2100 (Byrd et al. 2015, p. 748).
3.3.1.2 Urbanization
The increasing human population of California, with the concomitant high demand for limited supplies of land, water, and other resources, contributes to many other stressors that impact natural communities (Gonzales and Hoshi 2015). A report by Fresno County in 2012 estimated that the valley-wide population may increase from 3,970,000 in 2010 to 6,740,000 by 2050 (The Planning Center 2012, p. 19). Within the counties that make up the core of the kit fox range (Kern, Kings, Tulare, Fresno, and Merced) the population is projected to nearly double by 2050 (Table 3).
Table 3. Projected population growth in the southern San Joaquin Valley (The Planning Center 2012 p. 18, Table 5).
County Year
2010 2050
Kern 840,000 1,540,000
Kings 153,000 266,000
Tulare 442,000 710,000
Merced 256,000 461,000
Fresno 930,000 1,521,000
TOTAL 2,621,000 4,498,000
This continued increase in the human population has resulted in increased urban development throughout the San Joaquin Valley. Urbanization occurs throughout much of the range of the San Joaquin kit fox, but is particularly concentrated around existing urban development.
Bakersfield is currently the largest city within the range of the kit fox with a population of 380,000.
The urban and suburban Bakersfield area has expanded to comprise approximately 70 percent of the Metropolitan Bakersfield satellite area for the kit fox. 35 3.3.1.3 Energy Development
At the time that the San Joaquin kit fox was federally listed, extraction of petroleum products (including crude oil, propane, natural gas, etc.) was not considered to be a threat to the kit fox, as most of the petroleum-producing land was still relatively undisturbed (Jensen 1972, p.7). Since that time, oil and gas extraction has expanded throughout the southern and western portion of the kit fox range; primarily in western Kern, Kings, and Fresno Counties.
Oilfields in the southwestern portion of the San Joaquin Valley include the Midway-Sunset Oilfield which is the highest-producing BLM lease in the United States (BLM 2008) and the 74 mi2 Elk Hills Oilfield (the 7th largest in the United States). Oil and gas development is made up of both privately owned and federal (BLM) mineral estate. Most oil and gas leasing and development activities on public lands occur in the San Joaquin Valley on lands managed by the BLM’s Bakersfield Field Office.
Development of oil fields likely impacts the prey species for the kit fox both through direct loss of the species as well as alteration of the small mammal community. A study of an oil spill found a decrease in abundance of Heermann’s kangaroo rat (Dipodomys heermanni) between spill areas and control areas (Warrick et al. 1997, p. 22). High density oil field disturbances in western Kern County have been found to shift the composition of the small mammal community toward more generalist species (Fiehler et al. 2017, p. 139). Specialist species such as Nelson’s antelope squirrel (Ammospermophilus nelsoni) and short-nosed kangaroo rat (Dipodomys nitratoides) were not found in high density oil fields (Fiehler et al. 2017, p. 139). Although, kit fox have a varied diet, (Cypher et al. 2000, p. 21; White et al. 1996, p. 364), during drought conditions, they did not appear to significantly shift their diet away from preferred species during periods of prey scarcity (White et al. 1996, p. 374).
Instead, the kit foxes showed a pattern of decreased reproduction and may have contributed to poorer nutritional condition of the foxes (White et al. 1996, p. 375). Small mammal populations at NPRC showed strong responses to precipitation (Cypher et al. 2000, p. 31) and did not significantly differ between developed and undeveloped sites (Zoellick et al. 2002, p. 156). Impacts to prey species and small mammal communities within oil and gas development may be less important than year-to-year precipitation variation and direct loss of habitat. San Joaquin kit foxes appear to be tolerant of human disturbance as evidenced by their occupation of active oil and gas fields, solar facilities, and urban areas such as Bakersfield. In oil and gas fields they can be found denning in manmade structures such as pipes and culverts (Berry et al. 1987b, p. 12, Table 1). Oil and gas development impacts may impact kit fox through habitat loss and an associated reduction in overall carrying capacity (Cypher et al. 2000, p. 37). However, this relationship may not be linear and kit foxes continue to persist in areas of oil development (Cypher et al. 2000, p. 37).
Permanent modification to habitat due to oil and gas activities can reduce the species’ ability to disperse and find new habitat. As more land is affected by extraction of natural resources, there could be population level responses associated with habitat degradation and habitat modification.
The full extent of the effect to the San Joaquin kit fox from current or future oil and gas development is not fully understood at this time.
As of 2015, there were 48 utility-scale (> 20 MW) solar development projects planned, under construction, or operating within the range of the San Joaquin kit fox (Hernandez et al. 2015, p. 5).
The largest of these are found in the Carrizo Plain where two solar firms have installed panels on approximately on 5,250 acres on the northern end of the Carrizo Plain in San Luis Obispo County (Cypher et al. 2019, p. 1). Another utility-scale solar facility covering 1,688 acres has been installed in 36 the Cholame Valley in Monterey County. The most recently installed solar farm is a 2,154-acre facility in the Panoche Valley in San Benito County. Although these facilities have likely had impacts to San Joaquin kit foxes and their habitat, monitoring has shown that that solar development is not incompatible with kit fox presence (Cypher et al. 2019, entire). In addition, development of the solar facilities resulted in thousands of acres of land set aside under permanent conservation as mitigation.
The Service expects that additional solar projects will be proposed on lands important to the kit fox at the southern extent of its range.
3.3.1.4 Land Protection
Central Valley Project Conservation Program (CVPCP) and Habitat Restoration Program (HRP) The Central Valley Project (CVP) is a large multi-purpose water conveyance network designed to supply water and provide flood protection throughout a 400 mile (644 km) section of central California (Interior Region 10 2019). The Conservation Program (CVPCP) and CVP Improvement Act Habitat Restoration Program (HRP) are dual projects designed to protect and restore habitats impacted by the CVP. The San Joaquin kit fox is listed as a high priority species for these projects, with emphasis on efforts to: determine habitat management and compatible land uses, conduct presence/absence surveys, and protect key habitat areas (Bureau of Reclamation 2017, p. 2). Notable projects under the two programs include land acquisition and habitat restoration. The history of the CVPCP and HRP is discussed in detail in the blunt-nosed leopard lizard 2010 5-year Review (USFWS 2010a, pp. 24–33), including discussion of the Land Retirement Program and a list of lands acquired through the Bureau of Reclamation. Much of this land is mapped in the California Protected Areas Database (CPAD) and California Conservation Easement Database (CCED) (see next section).
Other Protected Land
Other entities including Federal and State agencies, non-governmental organizations (NGOs), Counties, and others protect land within the range of the kit fox. This land is subject to a wide variety of uses and land management, including areas with no mandate for wildlife protection.
However, areas without a specific management plan in place can provide suitable habitat for the kit fox under certain conditions and are candidates for actions that could enhance their value for the species. Habitat Conservation Plans (HCP) developed under section 10 of the ESA are a critical component of land protection for the kit fox. To date, HCPs covering the San Joaquin kit fox have committed to protecting over 90,000 acres. While not all this acreage is comprised of kit fox habitat, a significant proportion of the land acquisition for these HCPs protects annual grassland and shrubland habitats. Large plans such as the East Contra Costa County HCP/NCCP and Metro Bakersfield HCP have been instrumental at preserving relatively large parcels of land under permanent easement for the benefit of the kit fox. We compared land protection within species historical range and within the identified analysis units to assess the proportion of land within the range of the species that may provide some long-term protections from land conversion. We note that some of these areas do not currently (or may never) provide habitat for the kit fox due to land management, public access issues, or generally unsuitable terrain or landcover. For example, Mendota Wildlife Area is 11,800 acres but is mostly floodplain or flatlands, with limited alkali scrub (CDFW 2020).
The CPAD and CCED map existing land protections in California, and are a useful visual tools to assess contiguous blocks of land that support San Joaquin kit fox populations, as well as potential 37 land acquisitions that could help promote corridors between populations. We mapped CPAD and CCED relative to the San Joaquin kit fox historic range and analysis units (Figure 11). Because large blocks of contiguous land are important for the resilience of San Joaquin kit fox populations, conserving connected parcels of land is important for the health of the species.
Summary of impacts to the 3Rs
Reduction in habitat quality and quantity due to human induced land use change can alter the local habitat composition of an area making populations of San Joaquin kit fox less resilient and more vulnerable to stochastic events. Habitat fragmentation can also reduce connectivity and prevent gene flow among populations, leading to a reduction in population resiliency and species redundancy. In some areas, land protections have been put in place to prevent further alterations to native habitat.
In other areas, mitigation and restoration is being done to restore lands that were once habitat back to their native state. Protected lands may help offset effects to the 3R’s that arise from land use changes.
3.3.2 Climate Variability
Drought is defined as a deficiency in precipitation over an extended period, which reduces water supply, water quality, and range productivity, and impacts social and economic activities. Although drought is a relatively normal process throughout southern California, under climate change scenarios natural, historical stressors (i.e., drought, wildfires, flooding, etc.) have the potential to become exacerbated and extreme, due to anthropogenic factors. Small, fragmented populations of San Joaquin kit fox are at a higher risk of local extinction during extreme climatic events than are large populations on contiguous habitat. Drought specifically impacts the San Joaquin kit fox through alteration to the prey species. Giant kangaroo rat populations are greatly affected by changes in precipitation and herbaceous plant growth (Germano and Saslaw 2017, p. 1616). An extreme drought in California which lasted approximately from 2013 – 2016 saw precipitous declines in giant kangaroo rat numbers (Prugh et al. 2018, p. 2). Data suggest that kit foxes show decreases in reproduction and overall population decline in response to alterations in prey resulting from a drought period (Cypher et al. 2000, p. 33).
San Joaquin kit foxes are well adapted to annual cycles of drought and rainfall that are characteristic of the San Joaquin Valley. However, under current climate change scenarios climatic variability in the San Joaquin Valley is likely to increase. The Valley will likely see prolonged periods of drought (5 years or longer) punctuated by uncharacteristically heavy rainfall events. Individual San Joaquin kit fox will need to move throughout the environment to find enough mates and resources to survive and reproduce during times of drought and increased temperatures. Therefore, large areas of contiguous habitat are needed to ensure the species can survive harsh conditions (Figure 7). Data from the Carrizo Plain and Elk Hills show significant population changes in response to drought. In the Carrizo Plain, this variation appears to correspond to change in availability of the main prey species, the giant kangaroo rat (Dipodomys ingens).
Under current reasonable climate change scenarios, the San Joaquin Valley is likely to see changes in current ecosystem processes (Stewart et al. 2019, p. 6). Currently, the western slopes of the San Joaquin Valley are a climatic desert with low annual rainfall (Germano et al. 2011, p. 6). Precipitation typically occurs in the winter months, primarily between October and April. Historically there has always been inter-annual variation in precipitation and temperature; to which native species have adapted. These historical processes are projected to change and become more variable under 38 predicted future climate scenarios, and extreme droughts punctuated by heavy, episodic rainfall are both reasonable climate predictions. San Joaquin kit foxes are well adapted to variable climate conditions. However, drought has been linked to population declines in kit foxes and increasing frequency and severity of drought conditions may have an effect. Increasing variability in interannual precipitation (Single et al. 1996, pp. 36, 38–39) is already affecting portions of southern California, including the San Joaquin Valley. Weather patterns altered from historical norms are likely to affect annual rainfall; variation in annual rainfall can affect food availability for San Joaquin kit fox, causing population level responses.
39 Figure 11. Land protection across the historic range of the San Joaquin kit fox. 40 Summary of Impacts to the 3Rs
Kit fox populations affected by drought exhibit lower abundance, reproduction, and survival due to the impacts of drought on prey availability. This makes kit fox populations less resilient and more vulnerable to other stochastic events. San Joaquin kit foxes are well-adapted to xeric habitats (Morrell 1972, p. 4); however, if drought-induced decreases in population size could limit immigration and gene flow. This could lead to the loss of populations across the range and decrease the redundancy of the species, making it more susceptible to a wide scale, catastrophic event. The effects of drought may be amplified if it occurs in concert with other stressors.
3.3.3 Pesticide Use
Pesticides, and specifically rodenticides, pose a threat to kit foxes through direct or secondary poisoning. For example, kit foxes may be killed if they ingest rodenticide in a bait application, or if they consume rodents that have consumed bait (Orloff et al. 1986, p. 66; Berry et al. 1992, p. 11; Huffman and Murphy 1992, p. 378; Standley et al. 1992, p.16; Hosea 2000, p. 242). From the 1960s into the early 1980s rodenticides were often broadcast over large areas by airplane (USFWS 1998, p. 92). It is difficult to assess the magnitude of current impacts from rodenticides to San Joaquin kit fox populations. The state of California no longer broadcasts rodenticides over large areas of habitat (USFWS 2010a, p. 33). However, anticoagulant rodenticides are still used in agriculture to prevent damage to plants by wild rodent species (Franklin et al. 2018, p. 1). Anticoagulant rodenticide exposure and poisoning has emerged as a conservation concern for non-target wildlife on public lands (Gabriel et al. 2012. p. 1). Kit foxes may also be threatened by loss of prey if rodent prey populations decline due to rodent control programs. This is surmised as a cause for declines in the kit fox population in Contra Costa County (Orloff et al. 1986, p. 66).
Rodenticides are also used in urban, suburban, and rural areas to control a variety of rodents, including house mice, voles, pocket gophers, ground squirrels, and Norway rats (USEPA 2008, p. 2), animals that may comprise prey for the kit fox to varying degrees, depending on the prey community available in each locality. Predatory mammals (particularly the kit fox) from the urban-suburban environment surrounding Bakersfield experience high levels of exposure to anticoagulant rodenticides (McMillin et al 2008, p. 165). Use of these rodenticides by the untrained public is thought to be the likely source of exposure for these animals. Schitoskey (1975, p. 417) found that captive kit foxes consistently preferred dead kangaroo rats over anthropogenic food sources indicating that if dead rodents were present on the landscape, they would likely be consumed by the kit fox. Exposure modelling estimated that 36% of kit foxes were exposed to rodenticides and that 70% of this exposure resulted from low-density development (Nogiere et al. 2015, p. 7). A study in Bakersfield found that 73.5% of sample foxes showed evidence of rodenticide residue and 42.6% showed evidence of more than one rodenticide (Cypher et al. 2014, p. 7). Mortalities from rodenticides have been documented by Hosea (2000, p. 239, Table 2), Standley et al. (1992, p. 16), and McMillin et al. (2008, p. 165).
While regulations and procedures have been implemented to reduce non-target exposure, the effectiveness of these new regulations is not clear at this time. Kit foxes continue to be exposed to products used legally and illegally, or even to products whose use has been discontinued but have ongoing residual effect. However, given the potential for secondary exposure of kit foxes throughout its range, particularly in agricultural areas, along canals, and in urban areas, the Service expects rodenticide exposure could have effects to some kit fox populations, particularly where these populations are small or where they rely on target species, such as ground squirrels and murid 41 rodents, for prey.
Summary of Impacts to the 3Rs
Kit fox populations affected by pesticide use may exhibit lower abundance, reproduction, and survival. Although precise effects of non-target exposure are unknown, studies of kit fox and other non-target wildlife have shown effects ranging from a reduction in fecundity to mortality. Exposure across the range of the species may depress reproduction and lower survival rates for juvenile kit foxes. This in turn, reduces population sizes and may make exposed populations less resilient and more vulnerable to other stochastic events. The effects of pesticide exposure are likely amplified by the effects from other stressors such as drought or habitat fragmentation.
3.3.4 Predation
Predation has been identified as a leading cause of kit fox mortality (Ralls and White 1995, p. 727).
Most predator-related deaths are attributable to coyotes (Ralls and White 1995, p. 727; Cypher et al. 2000, p. 27), but bobcats also may contribute to much of the predator-caused mortality (Spiegel and Disney 1996, pp. 75 –76, Table 2; Cypher et al. 2000, p. 27). In addition to mortality caused by wild canids, kit foxes have also been killed by badgers, golden eagles, and free-ranging dogs (Briden et al. 1992, p. 87; Standley et al. 1992, p. 15; Ralls and White 1995, p. 727; Spiegel and Disney 1996, pp. 81, 85; Clark et al. 2005, p. 158). The lack of available dens for shelter in altered landscapes may increase the predation risk to kit fox from canids in these areas (Cypher et al. 2005, p. 10). Mortality due to interactions with predators, primarily coyotes, has ranged between 57 percent and 89 percent in the southern San Joaquin Valley (Standley et al. 1992, p. 15; Ralls and White 1995, p. 727; Spiegel and Disney 1996, p. 75; Cypher et al. 2000, p. 16, Tables 4 and 5). An experimental coyote-control program at the Elk Hills Naval Petroleum Reserves in California did not result in an increase in survival rate for kit foxes, nor did coyote-induced mortality decrease (Cypher and Scrivner 1992, p. 45). Often canid predators do not consume the kit foxes they kill indicating that canid predators do not always consume their prey, so kit fox mortality from coyotes may be due to interference competition (Cypher and Spencer 1998, p. 211; Cypher et al. 2000, p. 34; Nelson et al. 2007, p. 1473).
Interference competition occurs when individuals of one species behave in a manner that suppresses individuals of another species, effectively reducing the second species’ use of shared resources.
Although this is generally not defined as predation, for the purposes of this discussion we lumped this type of mortality under the umbrella of “predation”.
Other canids such as gray foxes and red foxes may compete with kit fox, though the degree of competition is unknown. The need for similar den sites and prey species probably place nonnative red foxes in direct competition with the much smaller kit fox. Nonnative red foxes are expanding their geographic range in central California (Orloff et al. 1986, p. 67; Lewis et al. 1993, p. 14), and competition with or predation on kit foxes may be a factor in the apparent decline of kit foxes in the Santa Clara Valley, and perhaps elsewhere in the northwestern segment of their range. Coyotes aggressively dominate encounters with red foxes and will pursue and kill both red and gray foxes (Sargeant and Allen 1989, entire), as well as kit foxes. Coyotes may reduce the negative impacts of red foxes on kit foxes by limiting red fox abundance and distribution, but details of interactions between the two species and the extent to which coyotes might slow or prevent the invasion of red foxes into kit fox habitats are unknown (White et al. 1994, p. 1835; Ralls and White 1995, pp. 727– 728).
42 Summary of Impacts to the 3Rs
Kit fox populations affected by increased predation may exhibit lower abundance and survival, particularly of juvenile foxes. This would have a long-term effect of reducing the size of the population which may make populations less resilient and more vulnerable to other stochastic events. Because increased predation may occur in areas where human development, both urban and agriculture, is occurring the effects of increased predation are likely increased by concurrent effects from land conversion.
3.3.5 Disease
Wildlife diseases (rabies, canine parvovirus, canine distemper virus, etc.) could cause substantial mortality or contribute to reduced fertility in female kit foxes (White et al. 2000, p. 205; Miller et al. 2000, p. 802). Diseases may threaten long-term viability of small populations of wildlife (Thorne and Williams 1988, pp. 67–69). Overall, disease was thought not to be a leading cause of mortality in kit foxes (McCue and O'Farrell 1988, pp. 278–279; Standley and McCue 1992, p. 12). However, two recent incidents at Camp Roberts and in Bakersfield have demonstrated that in certain instances, disease outbreaks may have population-level effects. Rabies has been implicated in the loss of a population at Camp Roberts (White et al. 2000, p. 209) and currently an outbreak of sarcoptic mange (Sarcoptes scabei) is causing steep population declines in the Bakersfield kit fox population (Deatherage 2020, p. 70). The mange epidemic in Bakersfield was first observed in 2013, and, although mortality from this outbreak is high (70% overall and 100% without veterinary intervention), thus far it appears to be largely limited to Bakersfield (Cypher et al. 2017, pp. 48–49, 51, Table 1). A few kit foxes with sarcoptic mange have been documented from Taft, but the outbreak does not appear to have spread into natural lands (Cypher pers. comm. 2020). Disease and predation may have both contributed to the catastrophic decline in the isolated population of San Joaquin kit fox at Camp Roberts, in San Luis Obispo County. Kit fox captures decreased from 103 in 1988 to 20 in 1991, and further to only 3 in 1997 (White et al. 2000, p. 207, 209, Table 1). During this same period, captures of striped skunks (Mephitis mephitis) also decreased, but the proportion of skunks that were found to be rabid increased. This correlation led biologists to propose that rabies was a factor in the kit fox decline (White et al. 2000, pp. 208, 209, Table 3).
3.3.6 Road Mortality
Vehicle strikes are a consistent, but small source of kit fox mortality on natural lands (Cypher et al. 2000, pp. 14–16, Tables 4 and 5; Bjurlin and Cypher 2003, p. 398, Table 1), with vehicle strikes accounting for <10 percent of mortality at the NPRC (Cypher et al. 2000, p. 27). On natural lands, kit foxes are sometimes killed by vehicle strikes, but impacts of roads on kit fox ecology are generally thought to be low (Cypher et al. 2005, p. 16). Although vehicle strikes may not have population-level effects in natural lands where traffic volume is low, vehicle strikes appear to be a more substantial source of mortality in human-altered landscapes, including urban environments (Bjurlin et al. 2005, p. 20; Cypher et al. 2003, as cited in Cypher and Brown 2006, p. 10). In urban settings such as Bakersfield, vehicle strikes can be the largest source of kit fox mortality and may impact urban kit fox populations (Bjurlin et al. 2005, p. 20). 43 Figure 12. Core conceptual model showing the stressors and needs for the San Joaquin kit fox.
Based on survey data at Camp Roberts, the population of San Joaquin kit fox in the Salinas Valley appears to have significantly dwindled and may no longer be present. Similarly, the population at Fort Hunter-Liggett has not been documented in several decades. Continuing records in the Paso Robles area suggest that kit foxes may still be present, but at low densities in this area (Dave Hacker pers com). Currently the only verified extant population in Monterey County occurs in the Cholame Valley. Finally, there are no current verified records within the last 10 years of kit fox north of Porterville on the east side of the San Joaquin Valley.
Although kit foxes have been documented in this area on occasion, historic data suggest that the fox has always been rare in this area (California Department of Fish and Wildlife 2020). In particular, large portions of the landscape north of Fresno are designated critical habitat for a wide variety of vernal pool species and the landscape is dominated by more mesic species. The characteristics that provide a premier vernal pool landscape such as clay soils and significant ponding likely reduce the suitability of the habitat for the kit fox by restricting the available areas for denning (Cypher et al. 2013, p. 29).
Throughout much of the kit fox range, individual populations are fragmented into smaller islands of suitable habitat that are isolated by topographic and manmade barriers. Currently the largest, most robust populations exist on the western periphery of the southern San Joaquin Valley and in the 44 Carrizo Plain. Habitats in this area are primarily comprised of sparse annual grassland and shrubland, and in some areas, there are large blocks of intact habitat. This area was mapped as having the most “high” habitat suitability by Cypher et al. (2013, p. 27). North of Santa Nella, habitats are primarily comprised of Aveena sp. grassland and the topography is generally steeper. Cypher et al. (2013, p. 27) modeled this as “moderate” habitat suitability.
Genetic studies have supported division into three distinct genetic clusters: Ciervo-Panoche, Bakersfield, and western Kern County/Carrizo Plain/Camp Roberts (Wilbert 2013, p. 80). In particular, Wilbert (2013, p. 85) indicated that the population in Bakersfield shows a unique genetic signature that is rarely found in the other genetic clusters. Both landscape level genetic studies indicate that gene flow is continuing through the sampled kit fox populations (Schwartz et al. 2005, p. 33; Wilbert 2013, p. 83) and that none of the sample populations were showing evidence of robust levels of genetic diversity and heterozygosity (Wilbert 2013, p. 80).
3.3.7 Existing Regulation
3.3.7.1 California Endangered Species Act (CESA)
The CESA (California Fish and Game Code, section 2080 et seq.) prohibits the unauthorized take of State-listed threatened or endangered species, The CESA requires State agencies to consult with the California Department of Fish and Wildlife that might affect a State-listed species and mitigate for any adverse impacts to the species or its habitat. Pursuant to CESA, it is unlawful to import or export, take, possess, purchase or sell any species or part or product of any species listed as endangered or threatened. The State may authorize permits for scientific, educational, or management purposes, and to allow take that is incidental to otherwise lawful activities.
3.3.7.2 Endangered Species Act (ESA)
The Endangered Species Act of 1973, as amended (ESA), is the primary Federal law providing protection for the San Joaquin kit fox. The Service has responsibility for administering the Act, including sections 7, 9, and 10 that address take. Section 9 prohibits the taking of any federally listed endangered or threatened species. Take is defined in section 3 as to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture or collect, or to attempt to engage in any such conduct. Harass is defined by Service regulations at 50 CFR 17.3 as an intentional or negligent act or omission which creates the likelihood of injury to wildlife by annoying it to such an extent as to significantly disrupt normal behavior patterns which include, but are not limited to, breeding, feeding, or sheltering.
Harm is defined by the same regulations as an act which actually kills or injures wildlife. Harm is further defined to include significant habitat modification or degradation that results in death or injury to listed species by significantly impairing essential behavior patterns, including breeding, feeding, or sheltering. The ESA provides for civil and criminal penalties for the unlawful taking of listed species.
Since listing, the Service has analyzed the potential effects of Federal projects under section 7(a)(2), which requires Federal agencies to consult with the Service prior to authorizing, funding, or carrying out activities that may affect listed species. For projects without a Federal nexus that would likely result in incidental take of listed species, the Service may issue incidental take permits to non-Federal applicants pursuant to section 10(a)(1)(B). Incidental take is defined as take that is incidental to, and not the purpose of, the carrying out of an otherwise lawful activity (50 CFR 402.02). To qualify for an incidental take permit, applicants must develop, fund, and implement a Service-approved Habitat 45 Conservation Plan that details measures to minimize and mitigate the project’s adverse impacts to listed species. Many of these Habitat Conservation Plans are coordinated with the State of California’s related Natural Community Conservation Planning program.
The status of the kit fox as a species listed under the ESA can reduce the severity of the effects of habitat loss due to urban and energy development, and, in some case, agricultural development.
Development projects that are subject to section 7 consultation or result in the issuance of an incidental take permit under section 10 typically include habitat compensation, which can reduce the severity of overall habitat loss typically associated with these projects. Habitat compensation can occur via a variety of mechanisms, including the purchase of credits at approved conservation banks, through permittee responsible mitigation, and through the development of habitat conservation plans (HCPs). In addition to reducing the amount of overall habitat loss for the species, section 10(a)(1)(A) of the ESA allows for permits to be issued for recovery activities that result in take.
Recovery activities are those activities that are specifically implemented for scientific purposes or to enhance the propagation or survival of the affected species, including interstate commerce activities.
Conservation Banks
A conservation bank is a site, or suite of sites (i.e., umbrella bank), that is conserved and managed in perpetuity, and provides ecological functions and services for specified listed species or resources.
Conservation banks function to offset adverse impacts to these species that occurred elsewhere; therefore, the Service approves a specified number of credits that the bank owner may sell to developers or other project proponents for use as compensation for adverse impacts their projects have on those species. The bank owner then uses the money from the credit purchases to permanently protect and manage the land for those species and resources. More information about conservation banks within the Sacramento Fish and Wildlife Office’s Service area can be found at:
https://www.fws.gov/sacramento/es/Conservation-Banking/Banks/In-Area/.
Currently, there are 16 banks covering 23,681 acres that conserve habitat for the kit fox.
Conservation banks are found throughout the range of the species. Four banks totaling 9,953 acres have sold out of credits. The remaining 12 banks are currently active. Not all the land within each bank provides suitable habitat for the species. However, conservation banks provide permanent protection that can secure suitable habitat and link movement corridors.
Permittee Responsible Mitigation
Permittee-responsible mitigation includes activities or projects undertaken by a permittee (or authorized agent) to provide compensatory mitigation for which the permittee retains full responsibility. Permittee-responsible mitigation projects are typically not established in advance of the impacts they are offsetting and they do not have credits that can be used at a later time to offset different impacts, like conservation banks.
Habitat compensation through permittee responsible mitigation for the San Joaquin kit fox occurs throughout the species range for a number of projects. The primary agencies implementing permittee responsible mitigation for the San Joaquin kit fox include the Bureau of Reclamation, Caltrans, oil and gas companies, and several solar facilities. 46 HCPs
Habitat Conservation Plans (HCPs) are planning documents required as part of an application for an incidental take permit. They describe the anticipated effects of the proposed taking; how those impacts will be minimized, or mitigated; and how the HCP is to be funded. HCPs can apply to both listed and non-listed species, including those that are candidates or have been proposed for listing.
Regional HCPs develop large-scale conservation strategies within a specific region that are designed to conserve functional ecological systems and the covered species that depend on them. Such HCPs aim to avoid a fragmented conservation landscape by working with local land use authorities and a designated implementing entity to conserve, enhance, and manage a preserve system. Project-level HCPs are designed to fully offset the impacts associated with the permitted activity by contributing to a larger conservation design.
Being included as a covered species under an HCP can result in habitat being set aside and managed for the species as mitigation for impacts associated with covered activities, such as planned urban development, within the HCP permit area. In addition to mitigation, avoidance, minimization, and other conservation measures (e.g. monitoring, seasonal work windows, habitat management, etc.) are implemented. HCPs can also utilize banks, in-lieu fee programs, or other mechanisms to preserve habitat in perpetuity and contribute to a regional conservation strategy.
There are 27 HCPs that include the San Joaquin kit fox as a covered species. The majority (10) of HCPs are in or cover portions of Kern County. More information about HCPs that include the San Joaquin kit fox as a covered species can be found at:
https://ecos.fws.gov/ecp0/profile/speciesProfile?spcode=A006.
Recovery Permits
Recovery permits, also referred to as 10(a)1(A) permits, allow scientists to take listed species to ultimately contribute to the recovery of the listed species. The data acquired from some actions covered under recovery permits (e.g., occurrence, abundance, distribution, etc.) allow the Service to make informed decisions for the species that will enhance their survival and recovery. Recovery permits can be issued for activities that directly aid the recovery of a species, such as captive breeding, reintroductions, habitat restoration, removal or reduction of threats, and educational programs. The Service’s recovery permitting program aids in the conservation of listed species by ensuring permittees have adequate field experience and qualifications for conducting activities with the target listed species and, for most species, ensures that permittees are following standardized protocols while surveying. The recovery permitting application process ensures that scientific proposals are crafted using the recommended actions laid out in the Recovery Plan for the target species. There is currently no protocol survey guidance for the San Joaquin kit fox; however, there are minimum qualifications to obtain a recovery permit for the species. Minimum qualifications and species specific protocols can be found at: https://www.fws.gov/sacramento/es/Permits/ Safe Harbor Agreements
Safe Harbor Agreements are also permitted under the Service’s recovery permitting program. The Safe Harbor Policy provides incentives for property owners to restore, enhance and maintain habitats for listed species. Because many endangered and threatened species occur exclusively, or to a large extent, on non-Federally owned property, the involvement of non-Federal property owners 47 in the conservation and recovery of listed species is critical to the eventual success of these efforts.
Under the policy, the Service will provide participating property owners with technical assistance to develop Safe Harbor Agreements that manage habitat for listed species, and provide assurances that additional land, water, and/or natural resource use restrictions will not be imposed as a result of their voluntary conservation actions to benefit covered species. When the property owner meets all the terms of the Agreement, the Service will authorize incidental take of the covered species at a level that enables the property owner to return the enrolled property back to an agreed upon baseline condition. There has been one Safe Harbor Agreement covering the San Joaquin kit fox for a project to install escape dens. The permit was issued in April 2003.
3.4 Analysis of Current Condition
In this section, we analyze the current conditions of the geographic analysis units of the San Joaquin kit fox as a way of assessing population resiliency. We then use our resiliency results to assess the redundancy and representation across the species. Assessing current condition as part of the SSA analysis is associated with, but independent from, assessing habitat suitability. Habitat suitability analyses use a suite of habitat predictor variables known or hypothesized to be important to the ecology and distribution of the species to create models that assess habitat and classify it according to suitability. Thus, different habitat sites that are modeled as “suitable” may be based on varying combinations of predictor variables. Models can be tested using historical or current occurrence data, but habitat modeled as suitable may or may not actually be occupied by, or accessible to, the species. Therefore, while habitat suitability can be an important component of understanding population resiliency and can inform future conservation efforts, habitat suitability alone may not accurately reflect the current condition of a specific population or of the species. When assessing population condition in the SSA framework, we identify specific habitat and demographic variables thought to be the main drivers of viability of the species.
Table 4. Stressors used to analyze the current and future condition of the San Joaquin kit fox.
Stressor
Effect to
Individuals or
populations is
known
Negative
Response has
been Quantified
Species or
Population Level
Response
Stressor Carried
Forward in
Analysis
Habitat
Modification or
Destruction Yes Yes Yes Yes
Stochastic
Precipitation
Patterns Yes Yes Yes Yes
Drought Yes Yes Yes Yes
Rodenticides Yes Yes Unknown No
Disease Yes Yes Yes Yes
Predation Yes Yes No No
48 In doing so, we address the individual and population needs of the species, as well as the main factors influencing viability (Table 4). We use quantitative or qualitative assessments to classify these categories into high, moderate, and low conditions in a Condition Category Table (CCT) and analyze the overall condition of each analysis unit across all the categories. Using the same table to assess the current and future condition of our analysis units allows for comparison between how the species is doing now and, in the future, (described in Chapter 4 of this document). We refer to “suitable habitat” when analyzing current and future condition of the populations, using modeled or otherwise projected habitat suitability in relation to current and future habitat factors and threats.
We analyzed the current condition of San Joaquin kit fox within the sixteen, geographic analysis units, as described above (Figure 9). These areas continue to encompass the known extant locations for San Joaquin kit fox thought to be important for the viability and recovery of the species. After consulting with experts and taking into account the data available to us, we identified average slope within the unit, natural land extent, connectivity, land protection, prey occurrence, population trends, and frequency of occupancy as the most important variables to include in our resiliency analysis for the reasons described below.
Average slope was included in our analysis because studies show San Joaquin kit fox tend to avoid areas of steep terrain. High slope areas may be used for foraging and dispersal, but steep habitat is not used routinely by breeding foxes. Therefore, in our analysis it was assumed that areas of high slope within the geographic units restricted the movement of the species and kit foxes were not likely to occupy these high slope areas in a significant way.
Because it is not possible to attain range-wide habitat quality data, we used available landcover data to assess the available potential habitat for the San Joaquin kit fox. Although certain habitat types are preferred by kit foxes, we presume much of the undeveloped land in the San Joaquin Valley may be used by the kit fox. The suitability of individual parcels may vary widely from year to year based on precipitation and land management factors (fire and grazing), but overall kit foxes are likely able to use most of the natural land within their range.
There is agreement among experts that habitat loss and fragmentation are the main stressors to the San Joaquin kit fox. We assess the connectivity across and between each analysis unit to capture the ability of an individual to move across the landscape. In order to measure connectivity, we qualitatively assessed the average natural land parcel size within the analysis unit, and fragmentation of natural lands and barriers such as incompatible land uses (urban and agricultural development), infrastructure, and topography both within and surrounding the analysis unit.
At the species and population level, San Joaquin kit fox need space and suitable habitat in order for populations to be viable over time. Land protection is important to ensure the long-term viability of the species. The percentage of land within each unit was assessed to determine how much protected land was available to the species. This analysis is consistent with the down- and delisting criteria outlined in the Recovery plan for the species (USFWS 1998, p. 186).
The availability of prey impacts adult survival and recruitment. Although we do not have range-wide data on prey availability, we assumed that where natural land extent was higher, there was likely more abundant natural prey. Kit fox will take a wide variety of prey items. However, for our analysis we focused on small mammals and considered areas where kangaroo rats were most prevalent to be in the highest condition for the species.
49 The demographic needs of the species are presented in two categories in our analysis of current condition: population trend and population persistence. Survival is not directly assessed in the table but is strongly correlated with the habitat components described above. Fecundity is captured through the assessment of persistence over time. It is assumed that analysis units that show a pattern of long-term occupancy also have relatively high fecundity. Because San Joaquin kit fox reproductive rates and population sizes can vary widely from year to year, long-term trends are likely a more accurate indicator of the health of a population. We used a timeframe of 30 years as our indicator for long-term persistence.
The criteria are defined in Table 5 and the analysis is presented in Table 6. We separated our overall metrics into demographic and habitat characteristics to avoid overweighting any one factor in either category.
Each geographic analysis unit was given a numeric score for each factor based on the condition category table (0.5 for very low condition, 1 for low condition, 2 for moderate condition, and 3 for high condition). Each geographic analysis unit’s overall condition was then calculated across all the factors. Categories with unknown conditions were conservatively given a score of 0.5, or very low.
Analysis of the current data indicate that demographic factors are likely more important to the overall condition of an analysis unit than the habitat factors. As such we weighted the overall demographic condition as twice as important as the overall habitat condition. We then translated the overall condition score into a current condition category of very low, low, moderate or high (Table 6; Figure 13). Low condition suggests that the population has a low probability of persistence (high extirpation risk), medium condition suggests a moderate probability of persistence, and high condition suggests high probability of persistence.
Table 5. Definitions for demographic and habitat conditions for the analysis of the San Joaquin kit fox.
Demographic
Factors
Habitat
Factors
Condition Population
Trend
Population
Persistence
% of sloped
terrain
within unit1
Undeveloped
Land1
Habitat
Connectivity
Habitat
Protection
Prey
Availability
High Population
Stable or
Increasing
Evidence of
persistence
over the last
30 years and
multiple
positive
records
results within
the last year
Greater than
75% of the
unit has a
slope < 10%
Majority of
unit (>50%) is
undeveloped
with natural
land cover or
non-irrigated
pasture.
Natural land
exists in larger
contiguous
blocks.
There are many
large (>1,100
acres) patches of
habitat within
the unit that well
connected both
within and
outside the unit
A large
proportion of
the natural
lands are
protected
within unit
Abundant
natural prey,
mostly
kangaroo rats.
50 Moderate Population
showing a slight
decline
Evidence of
persistence
over the last
30 years, but
less than 10
positive
records
within the
last 5 years.
Greater than
75% of the
unit has a
slope < 30%
Unit is
comprised of
< 50% natural
land cover or
non-irrigated
pastures.
Natural land
exists in few
or no large,
contiguous
blocks.
There are many
large (>1,100
acres) patches of
habitat within
the unit, but the
unit is highly
fragmented both
within and
outside the unit
by topographic
and
anthropogenic
barriers
Some of the
natural lands
protected
within the unit
Relatively
abundant
natural or
anthropogenic
prey, a wide
variety of small
mammals
available.
Low Population
showing longterm consistent
decline
Only
sporadic
records and
no positive
records
within the
last 5 years
More than
25% of the
unit has a
slope > 30%
Natural land
cover makes
up < 25% of
the unit and
there are no
large
contiguous
blocks of
habitat.
There are few or
no large patches
of habitat within
the unit, and the
patches and
highly
fragmented.
Little of the
natural lands
protected
within the unit
Natural prey
under threats
and not
consistently
available.
Very Low2 No evidence of
a current
population
Only records
are 10 years
old or
greater.
--- --- --- --- ---
1These two habitat factors are included in “Habitat Extent” in the Core Conceptual Model (Figure 7). 2We did not categorize any habitat factors as “very low” as all the units had some measurable habitat. 51 Table 6. Current condition of the San Joaquin kit fox across 16 geographic analysis units.
Analysis Unit
Population
Trend
Population
Persistence
Overall
Demogra
phy
% of sloped
terrain within
unit
Undeveloped
Land
Habitat
Connectivity
Habitat
Protection Prey Base Habitat Overall Total Overall
Livermore Very Low Very Low Very Low Low High Moderate Moderate Low Moderate Very Low Santa Nella Very Low Very Low Very Low Moderate High Moderate Low Low Moderate Very Low Kesterson NWR Very Low Very Low Very Low High Very Low Low High Low Moderate Very Low Western Madera Very Low Very Low Very Low High Low Low Low Low Low Very Low Pleasant Valley Low Moderate Low Moderate Moderate Moderate Low Moderate Moderate Low Porterville Low Moderate Low Moderate Moderate Moderate Low Low Moderate Low Allensworth/Pixley
NWR Low Low Low High Low Low Moderate Moderate Moderate Low Kettleman Hills Moderate High Moderate Moderate Moderate Moderate Low Moderate Moderate Moderate Semitropic/Kern
NWR Moderate High Moderate High Moderate Low Moderate Moderate Moderate Moderate Eastern Kern
County Moderate Moderate Moderate Moderate High Moderate Low Low Moderate Moderate Carrizo Plain High High High Moderate High High High High High High Bakersfield Moderate High Moderate High Low Moderate Low Moderate Moderate Moderate Western Kern
County High High High High High High Moderate High High High Cuyama Valley Low Moderate Low High Low Low Low Moderate Moderate Low Panoche/Western
Merced High High High Moderate Moderate Moderate Moderate High Moderate High Salinas Valley Very Low Very Low Very Low Moderate Moderate Moderate Low Low Moderate Very Low 52 Figure 13. Current condition of the San Joaquin kit fox in 16 geographic analysis units. 53 3.4.1 Uncertainty of Current Condition Analysis
As discussed in our analysis of current condition, we had to make many assumptions, both in defining condition categories and in assessing the condition of each geographic analysis unit relative to these categories (Table 7). These assumptions were informed by a thorough literature review and discussions with species experts.
Table 7. Uncertainty Assumptions
Analysis Factors Assumption
Population Trend There are no current or past studies that examine population trends at either a range wide or analysis
unit level. As such we used the frequency of
observations in CNDDB to estimate trends. We
assumed a pattern of continuous observation
indicated a stable trend and declining observation
indicated a declining trend.
Population Persistence We used records from CNDDB over time to estimate population persistence. While not
comprehensive, the long-term nature of the dataset
provides information on both historical and current
observations.
% of sloped terrain within unit We assumed that habitat with lower slopes provided more habitat value for the kit fox.
Natural Land We used the NLCD to quantify land that could be utilized by kit fox for any part of their lifecycle. We assumed that all of the identified landcover types
had some value to the kit fox.
Habitat Connectivity Connected habitat and larger patches support viable kit fox populations
Habitat Protection We used the CCED and CPAD to estimate the habitat protection within each unit. The assumption
was that lands included in these databases would
not be subject to either urban or agricultural
development. Although the level of protection on
the land varies widely, and may not all meet
recovery criteria, these lands may protect suitable
habitat and linkages critical for the kit fox.
Prey Base We assumed that the prey base was directly
correlated with natural land extent. That is, the
greater the amount of natural land present, the
more abundant and resilient the prey base would
be. Because kit fox are somewhat flexible in their
diet, certain situations (e.g. Bakersfield) do not
follow this assumption.
54 Summary of Current Condition Relative to the 3Rs
Currently, 5 of the analysis units are in very low condition and 4 are in low condition. Three of the analysis units are in high condition and 3 are in moderate condition. The high and moderate condition units are all restricted to the southern end of the San Joaquin Valley, except for the Ciervo-Panoche unit. All the units in the northern portion of the range were in very low condition, as was the disjunct Salinas Valley analysis unit.
Chapter 4. Future Condition
In this chapter, we predict the future viability of the 16 San Joaquin kit fox populations under three, plausible future scenarios. These scenarios use different combinations of climate change impacts, land-use change, and conservation measures to assess overall condition within each unit. This analysis will help predict how viability of the San Joaquin kit fox might change in the future and can help guide future conservation efforts.
4.1 Factors Influencing Future Viability
In this section, we discuss factors that might influence San Joaquin kit fox viability in the future. All of the factors that influence viability which were discussed previously are still applicable to the future condition of the species. However, they are not expanded on here, unless interactions and species responses are expected to change, which are then discussed in the context of emerging threats, or when trends or models can predict changes to these factors.
4.1.1 Climate Change
There is consensus that increases in greenhouse gas (GHG) emissions during the 20th century have resulted in global climate change characterized by: warming atmospheric and ocean temperatures, diminishing snow and ice, and rising sea levels (Intergovernmental Panel on Climate Change (IPCC) 2014, pp. 2–3). Climate change might affect San Joaquin kit fox through changes in precipitation and temperature, which can drive associated changes to vegetative communities as well alterations to prey species abundance and composition. Climate change is also associated with increased risk of catastrophic events, including floods and wildfires.
Climate models for California under different emission scenarios predict an overall warming effect somewhere between 1.7 and 5.8 degrees Celsius (3.0 to 10.4 degrees Fahrenheit) before 2100 (Cayan et al. 2008, p. 7). San Joaquin kit fox are adapted for arid survival and can withstand periods of high temperature. However, the thermal limits of San Joaquin kit fox survival have never been tested, and it is unclear how higher average annual temperatures might affect individuals.
Climate change is also associated with changes in precipitation cycles. Extremes in precipitation are expected to increase; current climate models predict a higher frequency of both extremely wet and extremely dry years (Swain et al. 2018, pp. 427–433). Some future climate projections suggest drought will be more intense; both longer, and dryer than in previous centuries (Trenberth et al. 2014, p. 17). San Joaquin kit fox survival and reproduction has been documented to decline during prolonged periods of drought (droughts lasting longer than two years) due to a decrease in prey availability and possibly in extremely wet years. Extremely wet years can cause over-abundance of dense, non-native grasses that may hinder the fox’s ability to evade predators and successfully find prey. Stochastic flooding events could also occur, which could negatively affect populations, especially in areas with high slope and topography, such as the Panoche geographic region or in low lying areas susceptible to ponding such as the Kern NWR/Semitropic Area. 55 Small, isolated populations are likely at higher risk from long-term intensive drought as are populations that persist in areas with highly fragmented and small habitat patches. Decreases in prey species leading to a decline in reproduction and abundance in these areas could have irreversible consequences on the population. As such, within-patch heterogeneity, between patch connectivity, and habitat patch-size, will be important to mitigate population declines from both dry and wet years.
4.1.2 Habitat Modification and Destruction
Habitat modification and destruction caused by land use changes (e.g., agricultural development, and urbanization) are expected to continue, and most likely to affect habitat on privately held lands. San Joaquin kit foxes rarely use irrigated agriculture and have only adapted to urban environments in a few locations.
Agricultural development will be influenced by changes to the climate. Some climate models predict increases in retired croplands in response to increased aridity. Land retirement of agricultural fields across the San Joaquin Valley could result in significant changes to overall land cover; as many as 500,000 acres may be retired by 2040 to meet requirement of existing groundwater regulations, and would have the potential to be restored to natural habitat (Hanak et al. 2017, p. 29). Strategic restoration of retired agricultural land has the potential to aid the recovery of endangered species, including the San Joaquin kit fox. The Land Retirement Demonstration Project included a Habitat Restoration Study to investigate the efficacy of restoration techniques on vegetation and wildlife (Uptain et al. 2005, pp. 107–175).
Solar photovoltaic development is a key renewable energy source that is expected to contribute to California’s commitment to meet half of the state’s energy demand from renewable resources by 2030 (de León 2015, p. 93). Phillips and Cypher (2015, pp. 15–16) identified approximately 4,145 km2 (1,601 mi2) of habitat with moderate to high potential for both solar energy development and listed species, including the San Joaquin kit fox. They recommend siting solar facilities in areas with low habitat value for listed species but high potential for solar projects, identifying 8,436 km2 (3,257 mi2) in the southern San Joaquin Valley, especially in western Fresno County, southern Kings County, and southern Kern County. Butterfield et al. (2013, entire) summarizes a process for identifying least-conflict lands for solar development.
Habitat modification and destruction via housing or commercial development is expected to continue in the future. As the population in the San Joaquin Valley increases, housing/commercial development continues to threaten San Joaquin kit fox habitat, albeit at a lower level than the threat posed by other types of development. The total number of households in the San Joaquin Valley is projected to increase by just over 1 percent per year from 2010 to 2050, with the highest annual growth rates in Merced and Madera Counties (The Planning Center 2012, pp. 13–14). The population is projected to increase on average by an annual rate of 1.27 percent, increasing from approximately 4 million people in 2010 to over 6.5 million in 2050, with the highest expected increase in Merced County and the lowest increases predicted for Tulare and Fresno Counties (The Planning Center 2012, pp. 17–18). Direct or indirect impacts to the species due to energy or development projects is expected to be somewhat offset through mitigation or other measures. 56 4.1.3 Strategic Land Retirement and Restoration
Agricultural development will be influenced by changes to the climate, with crop conversion, continued farming, or retirement depending on water availability. Retirement of agricultural lands across the San Joaquin Valley may be as great as 500,000 acres (over 202,000 hectares) by 2040 if retirement is used as the sole strategy to meet recent groundwater regulations (i.e., the Strategic Groundwater Management Act of 2014) (Hanak et al. 2017, p. 29). Strategic fallowing or restoration of retired agricultural land has the potential to aid in recovery of endangered species including the San Joaquin kit fox (Lortie et al. 2018, entire). Fallowed agricultural land has the potential to provide habitat for the San Joaquin kit fox under some conditions, particularly if there is adjacent nearby natural land. Additionally, active restoration can enhance the suitability of fallowed agricultural land for wildlife. The Land Retirement Demonstration Project included a Habitat Restoration Study to experimentally investigate the efficacy of restoration techniques on vegetation and wildlife, which is detailed in Uptain et al. (2005, pp. 107–175). Importantly, for retired land to be used by the species, it must be within the dispersal distance of an extant population of San Joaquin kit fox. Parcels that are too far away from known kit fox populations may provide suitable habitat but are unlikely to be occupied. While it is unlikely that the entirety of the retired land will be available for restoration, our projection anticipates a concerted effort to use the land for conservation. Some of the retired land will likely be put to alternate economic uses that have varying utility for kit foxes. In addition, much of the land to be retired is of poor quality (e.g. drainage impaired lands) and may not have historically provided much habitat for upland species. Some experts believe that in the event these lands are retired, the poor quality of these lands may make them difficult to restore (Cypher pers. comm. 2020).
4.1.4 High Speed Rail
The high-speed rail (HSR) is a publicly funded rail system currently under construction. Currently, the HSR is projected to route between Merced and Bakersfield. The project originally included extensions to San Francisco and Los Angeles, but these were indefinitely postponed due to costs and timing. Although we include a discussion of the HSR here to highlight it as a future threat to the species, the threat is likely limited to 3 populations along the proposed alignment and could result in reduced connectivity for within these populations. The HSR is currently projected to cross areas that have extant San Joaquin kit fox populations along the eastern and central portions of the San Joaquin Valley. We note, however, that much of the area within the proposed footprint is currently highly fragmented.
4.2 Future Scenarios
For our analysis of the San Joaquin kit fox’s future condition, we constructed three future scenarios focused on changes in stressors, climate change projections, and levels of conservation efforts (Table 8). While there are an infinite number of potential future scenarios we could have considered, these scenarios are meant to cover a large breadth of future conditions that could occur in the San Joaquin kit fox’s range, and all scenarios might not be equally plausible. To analyze future condition under these scenarios, we projected each scenario 60 years into the future, corresponding to our climate models and projections of future development and population growth.
These scenarios are based on two general circulation models (GCMs) and two Representative Concentration Pathway greenhouse gas trajectories that were selected from among 12 considered to represent a range of future conditions for California by the end of the 21st century. In comparison 57 to current conditions, the GCMs chosen are hotter and drier (MIROC-ESM), or warmer and wetter (CNRM-CM5). The RCPs (4.5 and 8.5) represent lower and higher levels of greenhouse gas concentrations; RCP 8.5 is in line with the current trend in greenhouse gas emissions. Taken together, the GCMs and RCPs represent a range of warming statewide from 1.99 to 4.56 degrees Celsius and between a 24.8 percent decrease in precipitation and a 22.9 percent increase, respectively. These two climate projections are both used in California Department of Fish and Wildlife (CDFW) reports on terrestrial vegetation (Thorne et al. 2016, p, 17-18) and mammals, including the San Joaquin kit fox (Stewart et al. 2019, entire). They are also used in an assessment of habitat restoration opportunities for blunt-nosed leopard lizards in the San Joaquin Desert (Stewart et al. 2019, entire). More information about the climate projections are available in those documents.
Table 8. Plausible future scenarios used to evaluate future condition of San Joaquin kit fox populations.
Scenario 1 Scenario 2 Scenario 3
Warm and wet (CNRM-CM5) Hot and dry (MIROC-ESM) Hot and dry (MIROC-ESM) Low emissions (RCP 4.5) High emissions (RCP 8.5) High emissions (RCP 8.5) Increased precipitation and resultant
change to vegetation and prey base
leads to range contraction
Potential northern expansion of
suitable habitat
Potential northern expansion of suitable
habitat
Increase in precipitation extremes
increases the number of drought years
Increase in precipitation extremes
increases the number of drought years
Increase in precipitation extremes
increases the number of drought years
Development continues on
unprotected areas, and management
continues on protected lands, at
current rates
Development continues on
unprotected areas, and management
continues on protected lands, at
current rates
Restoration of fallowed croplands in the
Central Valley and increased land
protections in some areas, but continued
development in some areas
4.2.1 Scenario 1
In Scenario 1, we assume conditions will be warm and wet (CNRM-CM5, RCP 4.5). We assume that under warm and wet conditions there will be increased annual precipitation that will result in increased amounts of herbaceous vegetation. Under this scenario, wetter portions of the kit fox’s range will likely become less suitable without increasing management actions. We assume that development continues at current rates on unprotected lands, with the potential to decrease habitat size for San Joaquin kit fox populations and connectivity between them. We also assume that management and restoration continues at current levels. 58 4.2.2 Scenario 2
In Scenario 2, we assume conditions will be hot and dry (MIROC-ESM, RCP 8.5). In this scenario, hot and dry conditions will result in an overall decrease in precipitation, which may lead to more potentially suitable habitat in areas that are currently wetter and require more management to maintain optimal vegetation. However, because these areas may not currently be occupied by San Joaquin kit fox and are separated by significant barriers from the extant populations, without active restoration or translocation, we do not anticipate that this habitat will necessarily be occupied by the species. We assume that under hotter and drier conditions there will be an increase in fallowed croplands, especially in the Central Valley. We also assume that development continues at current rates on unprotected lands, with the potential to decrease habitat size for San Joaquin kit fox populations and connectivity between them. We assume that management and restoration continues at current levels.
4.2.3 Scenario 3
In Scenario 3, we again assume that conditions will be hot and dry, using the same climatic conditions as in the second scenario. We assume that there is strategic restoration of retired agricultural land in the central part of the species range such that habitat size and connectivity will not be reduced (in comparison to Scenarios 1 and 2) and may increase in some areas assuming that these activities are conducted within dispersal distance of extant San Joaquin kit fox populations.
In all scenarios, we assume that there will be increased precipitation extremes, meaning that drought years and years with above-average precipitation are likely to become more frequent. We also assume that the High Speed Rail will be completed according to the projected route. Although the HSR is expected to reduce connectivity between populations and will reduce habitat connectivity across the route, we do not project that it will affect the specific habitat or demographic conditions in our condition analysis.
4.3 Analysis of Future Scenarios
Future conditions were projected for each geographic unit based on the variations in precipitation, climate, extent of suitable habitat, and restoration as specified in our scenarios (Table 9). We predicted changes in two of the three habitat needs, and two demographic factors described in our current condition analysis. The habitat factor of slope was held constant under future scenarios, as it is not expected to substantially change under any scenario. We assessed changes related to habitat factors by making qualitative assumptions about habitat suitability and land protections and made changes to demographic factors in accordance with related changes in habitat in the various scenarios.
Winter precipitation is difficult to predict in future scenarios, so assumptions were made under all future conditions. In scenario 1, we expected that warm and wet conditions would increase winter rains, leading to increased primary productivity and vegetative growth. This would increase the growth of both native and non-native plant growth. An increase in vegetation growth may benefit prey species for the San Joaquin kit fox, but in increase in vegetation growth may also impact the San Joaquin kit fox negatively if the vegetation hinders the ability of the kit fox to evade predators or successfully find prey. Under this scenario, higher winter precipitation would provide a moderate benefit to the species, particularly in areas where adequate habitat management is occurring.
However, this is not expected to significantly alter the overall condition of individual populations.
Under scenarios 2 and 3, intense droughts are projected to increase in both duration and intensity. 59 This would decrease overall survival and reproduction, and the species would be assumed to respond negatively.
Summer precipitation is also difficult to predict, and similar assumptions were necessary. Under scenario 1, all summer precipitation is likely to increase, which may decrease the overall suitability of habitat during the summer largely due to negative impacts to prey species such as giant kangaroo rats or other small mammal species. This reduction in prey base may negatively affect San Joaquin kit fox survival (particularly the pups) and could depress reproduction. Under future scenarios 2 and 3, summer precipitation would decrease, meaning summers would be hotter and dryer. Because San Joaquin kit fox are already adapted for hot, dry summers, it is not likely that they would be severely, negatively impacted by these changes during the summer months. Habitat suitability models confirm, that under RCP 8.5 emission scenarios, the suitable range of the giant kangaroo rat is expected to remain similar or even expand (Widick and Bean 2019, pp. 7–9). Based on this data, it is expected that the San Joaquin kit fox may experience increased population growth under scenarios where a primary prey species does well. This positive effect of increasing suitable habitat for the fox (and its prey), may help offset the effects of more frequent or longer droughts. As a result, we predicted no overall change in demographic or prey base factors under this scenario.
Habitat connectivity among San Joaquin kit fox populations has been decreasing throughout recent history. This trend is projected to continue into the foreseeable future. Under scenarios 1 and 2, we assumed if trends stayed the same, connectivity would continue to decrease in all analysis units, for areas that are not already under protection. Under scenario 3, we assumed that aggressive land retirement under SGMA and efforts from conservation organization could increase habitat connectivity by one level. SGMA is likely to have the most affect in areas that are under extreme overdraft. This particularly will affect recovery units that are in the southern end of the San Joaquin Valley (Western Kern, Ciervo-Panoche, Semitropic/Kern NWR, and Allensworth/Pixley NWR).
Land protection was changed only for Scenario 3, where we assumed protections would increase under aggressive restoration and protection efforts.
We made changes to demographic factors in relation to expected changes to habitat factors. We assumed that under scenarios 1 and 2, frequency of occupancy would decrease across much of the range in response to continued habitat fragmentation and land conversion. These land use changes would also impact survival and reproduction by reducing the available prey base and increasing exposure to rodenticides. Conversely, under scenario 3, the long-term effects of changes in climate are likely to be offset by increasing land protection and habitat availability. In this scenario, the combined effects of increases in habitat suitability (with presumed increased prey abundance) and land protection would lead to increases in kit fox populations despite potential negative effects from increased drought frequency.
As with the current condition analysis, if the overall demographic condition was “Very Low”, the condition of the geographic analysis unit could never be greater than “Very Low”. This is intended to minimize the bias toward unoccupied but “suitable” suitable habitat. 60 Table 9. Future condition of the San Joaquin kit fox across 16 geographic analysis units under 3 different climate change, land development, and restoration scenarios.
Scenario 1 Scenario 2 Scenario 3 Current Condition
Livermore Very Low Very Low Very Low Very Low
Santa Nella Very Low Very Low Very Low Very Low
Kesterson NWR Very Low Very Low Very Low Very Low
Western Madera Very Low Very Low Low Very Low
Pleasant Valley Low Low Moderate Low
Porterville Low Low Moderate Low
Allensworth Very Low Low Moderate Low
Kettleman Hills Moderate Moderate High Moderate
Semitropic Moderate Moderate High Moderate
E Kern Moderate Moderate High Moderate
Carrizo Plain Moderate High High High
Bakersfield Moderate Moderate Moderate Moderate
W Kern Moderate High High High
Cuyama Valley Low Low Moderate Moderate
Ciervo-Panoche Moderate High High High
Salinas Valley Very Low Very Low Very Low Very Low
4.3.1 Future Condition Uncertainty
There is a lot of uncertainty regarding climate models and the way in which San Joaquin kit fox might respond to changing climate. Models have great utility because they allow us to make predictions of how climate may change in the future, but their results should be interpreted cautiously. The models that we used in our future condition analysis are ones that are relatively much drier or wetter than most of the climate models and were chosen to present a possible range of future conditions. Models are mathematical representations of what can happen, but they do not always accurately predict future events. One key assumption in our analysis was that effects from drought would occur uniformly across the species range, and we acknowledge that drought impacts will be more nuanced than we have projected. However, based on the best available science regarding climate predictions, it seems likely that the species will face increased climate stress in the future, thus supporting the general decrease in habitat conditions in our future condition analysis.
Maintenance of environmentally diverse habitats will be important towards maintaining resilient populations. There is also some uncertainty regarding the efficacy of conservation efforts in the future. There has been a big push towards preserving natural lands in the San Joaquin Valley, which is demonstrated in our future condition analysis of habitat and demographic factors related to 61 habitat size and connectivity. Pilot studies on strategic restoration of land will be important in directing future recovery actions.
We used the best available science to forecast the future condition of San Joaquin kit fox under three plausible scenarios. Under the two most likely scenarios, conditions either remain constant or slightly decrease (Table 8). Decreases in population resiliency are expected because changes to climate are expected to put increased stress on populations, including reducing reproductive opportunities during droughts and changes to vegetation. Habitat development and agricultural conversion continue to threaten the species on unprotected lands, which can directly influence populations or restrict gene flow between them. Continued management on protected lands is essential towards maintaining resilient populations across the species range.
A handful of populations that are currently in very low condition are unlikely to positively respond to changes in habitat suitability or conservation without active efforts to restore these populations.
Loss of these populations, which tend to be on the boundaries of the species range or isolated from other populations, would result in losses for species representation. These populations are not in the areas that we projected targeted restoration efforts based on models for strategic restoration in the San Joaquin Valley. Indeed, the magnitude of restoration efforts will likely be one of the biggest factors driving differences between the outcomes in our projected scenarios.
The continued presence of moderately resilient populations in the western and southwestern units across all three scenarios suggests that the species will maintain moderate levels of redundancy and representation, although both measures are likely to be lower in the future.
Chapter 5. Species Viability
We have considered what the San Joaquin kit fox needs for viability (Chapter 2) and evaluated the species’ current condition in relation to those needs (Chapter 3). We also forecast how the species’ condition might change in the future under three different scenarios (Chapter 4). In this chapter, we synthesize the results from our historical, current, and future analyses and discuss the potential consequences for the future viability of the San Joaquin kit fox. We assess the viability of the species by evaluating the ability of the species to maintain a sufficient number and distribution of healthy populations to withstand environmental stochasticity (resiliency), catastrophes (redundancy), and changes in its environment (representation) into the future.
5.1 Resiliency
Resiliency is the ability of populations to tolerate natural, annual variation (stochasticity) in their environment and to recovery from periodic disturbance.
Throughout the latter half of the 20th century, large portions of the San Joaquin kit fox’s habitat were converted to agriculture and urban areas. Populations decreased rapidly in response to habitat loss and fragmentation. While there are few data on habitat condition and population trends prior to land conversion, evidence suggests historical populations had high resiliency, and foxes were likely widespread throughout their historical range.
Because there is no accurate, historical baseline to which we can compare, our analysis of the San Joaquin kit fox’s current condition and resiliency is limited to current geographic analysis units 62 which are fragmented, isolated, and increasingly small habitat patches throughout the range. Based on the relevant factors evaluated in our analysis, three of the current geographic analysis units are in overall high condition. These units have the highest probability of persistence. Demographically, three geographic analysis units currently are in high condition (Table 6; Panoche/Western Merced, Carrizo Plain, and Western Kern County), but none of the units are in high condition based on habitat factors. It is important to note that populations of San Joaquin kit fox on the Carrizo Plain are likely in the best current condition, being found on the largest continuous patch of habitat within the range of the species that has species-specific management. Once habitat is protected, connectivity can be increased, and populations might no longer be isolated from one another. In this case, the many of the negative effects of demographic and environmental stochasticity can be mitigated and populations are more likely to be stable. Currently, only two geographic units (the Carrizo Plain and western Kern County) are well equipped to withstand stochastic variation, leaving the remaining analysis units vulnerable to the effects of continued land conversion and climate change. This reduces the overall resiliency of the species.
Our predictions of future condition varied under our three condition scenarios. Under climate change scenarios and current land management trends, resiliency is likely to decrease in the future for two of our scenarios within all geographic units (Table 9). However, if land is converted and managed for the species, it is possible future conditions could improve for the species (Scenario 3).
5.2 Redundancy
Redundancy is the ability of a species to withstand catastrophic events. Redundancy is measured by the duplication and distribution of populations across the range of the species.
Historically, populations of San Joaquin kit fox were distributed throughout the San Joaquin Valley.
Although the current distribution of kit fox populations is like that known historically, the size of the populations has decreased. In addition, one population (Salinas Valley) may be extirpated and is in very low condition. Four additional populations in the northern portion of the range are currently in very low condition and three more populations are in low condition. Only three populations persist in high condition and two of these are adjacent to each other in the southwestern San Joaquin Valley. A catastrophic range-wide event, such as a long-term drought, has the potential to severely reduce viability of several units and lower the probability of persistence for several analysis units. In the most severe instance of a long-term drought, the three analysis units currently in high condition might be the only populations remaining.
Under two of the future scenarios, many of the geographic units could exist in low condition.
Should this happen, or should populations become locally extirpated, redundant variation throughout the range might no longer be possible. Land protections and restorations can mitigate the effects to populations from climatic change, and in Scenario 3, many of the populations are in higher condition then they are currently. This means persistence of many of the populations is more likely, even under climate change scenarios with an increase in adverse stochastic events.
5.3 Representation
Representation is the ability of a species to adapt catastrophic events, or to changing physical (climate, habitat) and biological (diseases, predators) conditions.
A species’ representation is measured by assessing the genetic, morphological, behavioral, and ecological diversity within and among populations across its range. The more representation, or 63 diversity, a species has, the more likely it is to persist in changing environments. Historically, the San Joaquin kit fox was distributed throughout the southern end of the San Joaquin Valley and foothills of the Sierra Nevada and Coast Range. Within the range, San Joaquin kit fox occupied a variety of grassland, desert, scrub and upland habitats. Precipitation varies among these habitats, being more mesic in the northern, and western (coastal) portions of the range. All the northern and western portions of the range are in very low condition. This region represents a different ecological setting and possibly uniquely adapted kit foxes. The loss of these populations is a loss of representation and adaptive capacity from historic conditions. Additional loss of resiliency and extirpations forecast in the future are likely to further reduce this representation and adaptive capacity. Genetic diversity appears to remain high throughout the range of the San Joaquin kit fox. It is uncertain how much genetic diversity has already been lost, however.
Gene flow appears to continue to occur across the southern portion of the range in spite of the increase in habitat fragmentation. However, San Joaquin kit fox do not likely occur in the densities or numbers they once did, and populations continue to fluctuate throughout climatic events.
However, populations still exist in a variety of habitats throughout the range, showing a moderate amount of representation. Under future scenarios, representation is likely to decrease under scenario 1 and 2, due to declining conditions across the range. As conditions decline, extirpation becomes more likely, reducing the ability of a species to withstand stochastic events. Under scenario 3, representation is likely to increase across the range, should land protection be increased.
5.4 Synopsis of Viability
Viability is the ability of a species to sustain populations over time. Species which exhibit high resiliency, redundancy, and representation are more viable than those which do not.
The San Joaquin kit fox is currently endangered. Habitat loss was the main stressors responsible for the decline of the species. Since the time of listing, populations have continued to decrease across much of the range. Abundances have fluctuated annually, and with climatic events. Currently, five of the geographic units are in “very low” condition, six are in “low” condition, and five are in “moderate” condition. Populations are still distributed throughout a variety of habitats, and show high genetic diversity and ability to rebound from climatic extremes, demonstrating redundancy and representation.
We forecast the future viability of the species by predicting the responses of our geographic unit conditions under three future scenarios 60 years into the future. Under two scenarios, most of the units are at risk of existing in “low” or “very low” condition and those in “very low” condition would be at high risk of extirpation. This would represent a significant range contraction of the species, and viability would be drastically reduced. Land protection and management in scenario 3 improves the condition of the species and increases viability.
The current persistence of the San Joaquin kit fox within the remaining habitat is evidence of the species’ resiliency and is largely due to large-scale habitat protections. Species-specific land management has been demonstrated to improve the habitat and abundance of the species locally.
Habitat restoration in areas affected by agriculture or invasive grasses, could additionally help buffer the effects of climate change and historical habitat loss. This could mitigate the effect of increased drought and possible heavy precipitation.
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Shaffer, M. L., and B. A. Stein. 2000. Safeguarding our precious heritage. In Precious Heritage: the status of biodiversity in the United States. Eds. B. A. Stein, L.S. Kutner, and J. S. Adams.
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Single, J.R., D.J. Germano, and M.H. Wolfe. 1996. Decline of kangaroo rats during a wet winter in the southern San Joaquin Valley, California. Transactions of the Western Section of the Wildlife Society 32:34-41.
Smith, D.A., K. Ralls, B.L. Cypher, H.O. Clark, Jr., P.A. Kelly, D.F. Williams, and J.E. Maldonado. 71 2006. Relative abundance of endangered San Joaquin Kit Foxes (Vulpes macrotis mutica) based on scat-detection dog surveys. The Southwestern Naturalist 51:210–219.
Spencer, K.A., W.H. Berry, W.G. Standley, and T.P. O’Farrell. 1992. Reproduction of the San Joaquin kit fox (Vulpes velox macrotis) (sic) on Camp Roberts Army National Guard Training Site, California. U.S. Department of Energy. EG&G/EM Santa Barbara Operations. Report No. EGG 10617-2154. 18 pages.
Spiegel, L.K., and M. Bradbury. 1992. Home range characteristics of the San Joaquin Kit Fox in western Kern County, California. Transactions of the Western Section of the Wildlife Society 28:83–92.
Spiegel, L.K., B.L. Cypher, and T. Dao. 1996. Diet of the San Joaquin kit fox at three sites in western Kern County. Pages 39-50 in L.K. Spiegel (editor), Studies of the San Joaquin kit fox in undeveloped and oil-developed areas. California Energy Commission, Sacramento, California.
Spiegel, L.K., and M. Disney. 1996. Mortality sources and survival rates of San Joaquin kit foxes in oil-developed and undeveloped lands of southwestern Kern County, California. Pages 71-92 in L.K. Spiegel (editor), Studies of the San Joaquin kit fox in undeveloped and oil-developed areas. California Energy Commission, Sacramento, California.
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1 Appendix 1. Tables for the three future condition scenarios Scenario 1: Climate change results in warm and wet conditions. Development, conservation, and land use changes occur at rates similar to 2020 Population
Trend
Population
Persistence
Overall
Demography
% of sloped
terrain within
unit
Undeveloped
Land
Habitat
Connectivity
Habitat
Protection Prey Base
Habitat
Overall Total Overall
Livermore Very Low Very Low Very Low Low Moderate Low Moderate Very Low Low Very Low Santa Nella Very Low Very Low Very Low Moderate Moderate Low Low Very Low Low Very Low Kesterson NWR Very Low Very Low Very Low High Very Low Very Low High Very Low Low Very Low Western Madera Very Low Very Low Very Low High Very Low Very Low Low Very Low Low Very Low Pleasant Valley Very Low Moderate Low Moderate Low Low Low Low Low Low Porterville Very Low Moderate Low Moderate Low Low Low Very Low Low Low Allensworth/Pixley
NWR Very Low Low Very Low High Very Low Very Low Moderate Low Low Very Low Kettleman Hills Low High Moderate Moderate Low Low Low Low Low Moderate Semitropic/Kern
NWR Low High Moderate High Low Very Low Moderate Low Low Moderate Eastern Kern
County Low Moderate Low Moderate Moderate Low Low Very Low Low Moderate Carrizo Plain Moderate High Moderate Moderate Moderate Moderate High Moderate Moderate Moderate Bakersfield Low High Moderate High Very Low Low Low Low Low Moderate Western Kern
County Moderate High Moderate High Moderate Moderate Moderate Moderate Moderate Moderate Cuyama Valley Very Low Moderate Low High Very Low Very Low Low Low Low Low Panoche/Western
Merced Moderate High Moderate Moderate Low Low Moderate Moderate Low Moderate Salinas Valley Very Low Very Low Very Low Moderate Low Low Low Very Low Low Very Low 2 Scenario 2: Climate change results in hot and dry conditions. Development, conservation, and land use changes occur at rates similar to 2020.
Population
Trend
Population
Persistence
Overall
Demography
% of sloped
terrain within
unit
Undeveloped
Land
Habitat
Connectivity
Habitat
Protection
Prey
Base
Habitat
Overall Total Overall
Livermore Very Low Very Low Very Low Low High Moderate Moderate Moderate Moderate Very Low Santa Nella Very Low Very Low Very Low Moderate High Moderate Low Moderate Moderate Very Low Kesterson NWR Very Low Very Low Very Low High Low Low High Moderate Moderate Very Low Western Madera Very Low Very Low Very Low High Moderate Low Low Moderate Low Very Low Pleasant Valley Low Moderate Low Moderate High Moderate Low High Moderate Low Porterville Low Moderate Low Moderate High Moderate Low Moderate Moderate Low Allensworth/Pixley
NWR Low Low Low High Moderate Low Moderate High Moderate Low Kettleman Hills Moderate High Moderate Moderate High Moderate Low High Moderate Moderate Semitropic/Kern
NWR Moderate High Moderate High High Low Moderate High Moderate Moderate Eastern Kern
County Moderate Moderate Moderate Moderate High Moderate Low Moderate Moderate Moderate Carrizo Plain High High High Moderate High High High High High High Bakersfield Moderate High Moderate High Moderate Moderate Low High Moderate Moderate Western Kern
County High High High High High High Moderate High High High Cuyama Valley Low Moderate Low High Moderate Low Low High Moderate Low Panoche/Western
Merced High High High Moderate High Moderate Moderate High Moderate High Salinas Valley Very Low Very Low Very Low Moderate High Moderate Low Moderate Moderate Very Low 3 Scenario 3: Climate change results in hot and dry conditions. Development and land use changes occur at rates similar to 2020, but conservation initiatives take advantage of aggressive land retirement goals to increase upland habitat.
Population
Trend
Population
Persistence
Demo
Overall
% of sloped
terrain within
unit
Undeveloped
Land
Habitat
Connectivity
Habitat
Protection Prey Base
Habitat
Overall Total Overall
Livermore Very Low Very Low Very Low Low High High High Moderate Moderate Very Low Santa Nella Very Low Very Low Very Low Moderate High High Moderate Moderate Moderate Very Low Kesterson NWR Very Low Very Low Very Low High Low Moderate High Moderate Moderate Very Low Western Madera Low Low Low High Moderate Moderate Moderate Moderate Moderate Low Pleasant Valley Moderate High Moderate Moderate High High Moderate High Moderate Moderate Porterville Moderate High Moderate Moderate High High Moderate Moderate Moderate Moderate Allensworth/Pixley
NWR Moderate Moderate Moderate High Moderate Moderate High High Moderate Moderate Kettleman Hills High High High Moderate High High Moderate High Moderate High Semitropic/Kern
NWR High High High High High Moderate High High High High Eastern Kern
County High High High Moderate High High Moderate Moderate Moderate High Carrizo Plain High High High Moderate High High High High High High Bakersfield Moderate High Moderate High Moderate High Moderate High Moderate Moderate Western Kern
County High High High High High High High High High High Cuyama Valley Moderate High Moderate High Moderate Moderate Moderate High Moderate Moderate Panoche/Western
Merced High High High Moderate High High High High High High Salinas Valley Very Low Very Low Very Low Moderate High High Moderate Moderate Moderate Very Low
STANDARD RECOMMENDATIONS 1
U.S. FISH AND WILDLIFE SERVICE
STANDARDIZED RECOMMENDATIONS
FOR PROTECTION OF THE ENDANGERED SAN JOAQUIN KIT FOX
PRIOR TO OR DURING GROUND DISTURBANCE
Prepared by the Sacramento Fish and Wildlife Office
January 2011
INTRODUCTION
The following document includes many of the San Joaquin kit fox (Vulpes macrotis mutica) protection measures typically recommended by the U. S. Fish and Wildlife Service (Service), prior to and during ground disturbance activities. However, incorporating relevant sections of these guidelines into the proposed project is not the only action required under the Endangered Species Act of 1973, as amended (Act) and does not preclude the need for section 7 consultation or a section 10 incidental take permit for the proposed project.
Project applicants should contact the Service in Sacramento to determine the full range of requirements that apply to your project; the address and telephone number are given at the end of this document. Implementation of the measures presented in this document may be necessary to avoid violating the provisions of the Act, including the prohibition against "take" (defined as killing, harming, or harassing a listed species, including actions that damage or destroy its habitat). These protection measures may also be required under the terms of a biological opinion pursuant to section 7 of the Act resulting in incidental take authorization (authorization), or an incidental take permit (permit) pursuant to section 10 of the Act. The specific measures implemented to protect kit fox for any given project shall be determined by the Service based upon the applicant's consultation with the Service.
The purpose of this document is to make information on kit fox protection strategies readily available and to help standardize the methods and definitions currently employed to achieve kit fox protection. The measures outlined in this document are subject to modification or revision at the discretion of the Service.
IS A PERMIT NECESSARY?
Certain acts need a permit from the Service which includes destruction of any known (occupied or unoccupied) or natal/pupping kit fox dens. Determination of the presence or absence of kit foxes and /or their dens should be made during the environmental review process.
All surveys and monitoring described in this document must be conducted by a qualified biologist and these activities do not require a permit. A qualified biologist (biologist) means any person who has completed at least four years of university training in wildlife biology or a related science and/or has demonstrated field experience in the identification and life history of the San Joaquin kit fox. In addition, the biologist(s) must be able to identify coyote, red fox, STANDARD RECOMMENDATIONS 2
gray fox, and kit fox tracks, and to have seen a kit fox in the wild, at a zoo, or as a museum mount. Resumes of biologists should be submitted to the Service for review and approval prior to an6y survey or monitoring work occurring.
SMALL PROJECTS
Small projects are considered to be those projects with small foot prints, of approximately one acre or less, such as an individual in-fill oil well, communication tower, or bridge repairs. These projects must stand alone and not be part of, or in any way connected to larger projects (i.e., bridge repair or improvement to serve a future urban development). The Service recommends that on these small projects, the biologist survey the proposed project boundary and a 200-foot area outside of the project footprint to identify habitat features and utilize this information as guidance to situate the project to minimize or avoid impacts. If habitat features cannot be completely avoided, then surveys should be conducted and the Service should be contacted for technical assistance to determine the extent of possible take.
Preconstruction/preactivity surveys shall be conducted no less than 14 days and no more than 30 days prior to the beginning of ground disturbance and/or construction activities or any project activity likely to impact the San Joaquin kit fox. Kit foxes change dens four or five times during the summer months, and change natal dens one or two times per month (Morrell 1972). Surveys should identify kit fox habitat features on the project site and evaluate use by kit fox and, if possible, assess the potential impacts to the kit fox by the proposed activity. The status of all dens should be determined and mapped (see Survey Protocol). Written results of preconstruction/preactivity surveys must be received by the Service within five days after survey completion and prior to the start of ground disturbance and/or construction activities.
If a natal/pupping den is discovered within the project area or within 200-feet of the project boundary, the Service shall be immediately notified and under no circumstances should the den be disturbed or destroyed without prior authorization. If the preconstruction/preactivity survey reveals an active natal pupping or new information, the project applicant should contact the Service immediately to obtain the necessary take authorization/permit.
If the take authorization/permit has already been issued, then the biologist may proceed with den destruction within the project boundary, except natal/pupping den which may not be destroyed while occupied. A take authorization/permit is required to destroy these dens even after they are vacated. Protective exclusion zones can be placed around all known and potential dens which occur outside the project footprint (conversely, the project boundary can be demarcated, see den destruction section).
STANDARD RECOMMENDATIONS 3
OTHER PROJECTS
It is likely that all other projects occurring within kit fox habitat will require a take authorization/permit from the Service. This determination would be made by the Service during the early evaluation process (see Survey Protocol). These other projects would include, but are not limited to: Linear projects; projects with large footprints such as urban development; and projects which in themselves may be small but have far reaching impacts (i.e., water storage or conveyance facilities that promote urban growth or agriculture, etc.).
The take authorization/permit issued by the Service may incorporate some or all of the protection measures presented in this document. The take authorization/permit may include measures specific to the needs of the project and those requirements supersede any requirements found in this document.
EXCLUSION ZONES
In order to avoid impacts, construction activities must avoid their dens. The configuration of exclusion zones around the kit fox dens should have a radius measured outward from the entrance or cluster of entrances due to the length of dens underground. The following distances are minimums, and if they cannot be followed the Service must be contacted. Adult and pup kit foxes are known to sometimes rest and play near the den entrance in the afternoon, but most above-ground activities begin near sunset and continue sporadically throughout the night. Den definitions are attached as Exhibit A.
Potential den** 50 feet
Atypical den** 50 feet
Known den* 100 feet
Natal/pupping den
(occupied and unoccupied)
Service must be contacted
*Known den: To ensure protection, the exclusion zone should be demarcated by fencing that encircles each den at the appropriate distance and does not prevent access to the den by kit foxes.
Acceptable fencing includes untreated wood particle-board, silt fencing, orange construction fencing or other fencing as approved by the Service as long as it has openings for kit fox ingress/egress and keeps humans and equipment out. Exclusion zone fencing should be maintained until all construction related or operational disturbances have been terminated. At that time, all fencing shall be removed to avoid attracting subsequent attention to the dens.
STANDARD RECOMMENDATIONS 4
**Potential and Atypical dens: Placement of 4-5 flagged stakes 50 feet from the den entrance(s) will suffice to identify the den location; fencing will not be required, but the exclusion zone must be observed.
Only essential vehicle operation on existing roads and foot traffic should be permitted.
Otherwise, all construction, vehicle operation, material storage, or any other type of surfacedisturbing activity should be prohibited or greatly restricted within the exclusion zones.
DESTRUCTION OF DENS
Limited destruction of kit fox dens may be allowed, if avoidance is not a reasonable alternative, provided the following procedures are observed. The value to kit foxes of potential, known, and natal/pupping dens differ and therefore, each den type needs a different level of protection.
Destruction of any known or natal/pupping kit fox den requires take authorization/permit from the Service.
Destruction of the den should be accomplished by careful excavation until it is certain that no kit foxes are inside. The den should be fully excavated, filled with dirt and compacted to ensure that kit foxes cannot reenter or use the den during the construction period. If at any point during excavation, a kit fox is discovered inside the den, the excavation activity shall cease immediately and monitoring of the den as described above should be resumed. Destruction of the den may be completed when in the judgment of the biologist, the animal has escaped, without further disturbance, from the partially destroyed den.
Natal/pupping dens: Natal or pupping dens which are occupied will not be destroyed until the pups and adults have vacated and then only after consultation with the Service. Therefore, project activities at some den sites may have to be postponed.
Known Dens: Known dens occurring within the footprint of the activity must be monitored for three days with tracking medium or an infra-red beam camera to determine the current use. If no kit fox activity is observed during this period, the den should be destroyed immediately to preclude subsequent use.
If kit fox activity is observed at the den during this period, the den should be monitored for at least five consecutive days from the time of the observation to allow any resident animal to move to another den during its normal activity. Use of the den can be discouraged during this period by partially plugging its entrances(s) with soil in such a manner that any resident animal can escape easily. Only when the den is determined to be unoccupied may the den be excavated under the direction of the biologist. If the animal is still present after five or more consecutive days of plugging and monitoring, the den may have to be excavated when, in the judgment of a biologist, it is temporarily vacant, for example during the animal's normal foraging activities.
STANDARD RECOMMENDATIONS 5
The Service encourages hand excavation, but realizes that soil conditions may necessitate the use of excavating equipment. However, extreme caution must be exercised.
Potential Dens: If a take authorization/permit has been obtained from the Service, den destruction may proceed without monitoring, unless other restrictions were issued with the take authorization/permit. If no take authorization/permit has been issued, then potential dens should be monitored as if they were known dens. If any den was considered to be a potential den, but is later determined during monitoring or destruction to be currently, or previously used by kit fox (e.g., if kit fox sign is found inside), then all construction activities shall cease and the Service shall be notified immediately.
CONSTRUCTION AND ON-GOING OPERATIONAL REQUIREMENTS
Habitat subject to permanent and temporary construction disturbances and other types of ongoing project-related disturbance activities should be minimized by adhering to the following activities. Project designs should limit or cluster permanent project features to the smallest area possible while still permitting achievement of project goals. To minimize temporary disturbances, all project-related vehicle traffic should be restricted to established roads, construction areas, and other designated areas. These areas should also be included in preconstruction surveys and, to the extent possible, should be established in locations disturbed by previous activities to prevent further impacts.
1. Project-related vehicles should observe a daytime speed limit of 20-mph throughout the site in all project areas, except on county roads and State and Federal highways; this is particularly important at night when kit foxes are most active. Night-time construction should be minimized to the extent possible. However if it does occur, then the speed limit should be reduced to 10-mph. Off-road traffic outside of designated project areas should be prohibited.
2. To prevent inadvertent entrapment of kit foxes or other animals during the construction phase of a project, all excavated, steep-walled holes or trenches more than 2-feet deep should be covered at the close of each working day by plywood or similar materials. If the trenches cannot be closed, one or more escape ramps constructed of earthen-fill or wooden planks shall be installed. Before such holes or trenches are filled, they should be thoroughly inspected for trapped animals. If at any time a trapped or injured kit fox is discovered, the Service and the California Department of Fish and Game (CDFG) shall be contacted as noted under measure 13 referenced below.
3. Kit foxes are attracted to den-like structures such as pipes and may enter stored pipes and become trapped or injured. All construction pipes, culverts, or similar structures with a diameter of 4-inches or greater that are stored at a construction site for one or more overnight periods should be thoroughly inspected for kit foxes before the pipe is subsequently buried, capped, or otherwise used or moved in any way. If a kit fox is STANDARD RECOMMENDATIONS 6
discovered inside a pipe, that section of pipe should not be moved until the Service has been consulted. If necessary, and under the direct supervision of the biologist, the pipe may be moved only once to remove it from the path of construction activity, until the fox has escaped.
4. All food-related trash items such as wrappers, cans, bottles, and food scraps should be disposed of in securely closed containers and removed at least once a week from a construction or project site.
5. No firearms shall be allowed on the project site.
6. No pets, such as dogs or cats, should be permitted on the project site to prevent harassment, mortality of kit foxes, or destruction of dens.
7. Use of rodenticides and herbicides in project areas should be restricted. This is necessary to prevent primary or secondary poisoning of kit foxes and the depletion of prey populations on which they depend. All uses of such compounds should observe label and other restrictions mandated by the U.S. Environmental Protection Agency, California Department of Food and Agriculture, and other State and Federal legislation, as well as additional project-related restrictions deemed necessary by the Service. If rodent control must be conducted, zinc phosphide should be used because of a proven lower risk to kit fox.
8. A representative shall be appointed by the project proponent who will be the contact source for any employee or contractor who might inadvertently kill or injure a kit fox or who finds a dead, injured or entrapped kit fox. The representative will be identified during the employee education program and their name and telephone number shall be provided to the Service.
9. An employee education program should be conducted for any project that has anticipated impacts to kit fox or other endangered species. The program should consist of a brief presentation by persons knowledgeable in kit fox biology and legislative protection to explain endangered species concerns to contractors, their employees, and military and/or agency personnel involved in the project. The program should include the following: A description of the San Joaquin kit fox and its habitat needs; a report of the occurrence of kit fox in the project area; an explanation of the status of the species and its protection under the Endangered Species Act; and a list of measures being taken to reduce impacts to the species during project construction and implementation. A fact sheet conveying this information should be prepared for distribution to the previously referenced people and anyone else who may enter the project site.
10. Upon completion of the project, all areas subject to temporary ground disturbances, including storage and staging areas, temporary roads, pipeline corridors, etc. should be STANDARD RECOMMENDATIONS 7
re-contoured if necessary, and revegetated to promote restoration of the area to preproject conditions. An area subject to "temporary" disturbance means any area that is disturbed during the project, but after project completion will not be subject to further disturbance and has the potential to be revegetated. Appropriate methods and plant species used to revegetate such areas should be determined on a site-specific basis in consultation with the Service, California Department of Fish and Game (CDFG), and revegetation experts.
11. In the case of trapped animals, escape ramps or structures should be installed immediately to allow the animal(s) to escape, or the Service should be contacted for guidance.
12. Any contractor, employee, or military or agency personnel who are responsible for inadvertently killing or injuring a San Joaquin kit fox shall immediately report the incident to their representative. This representative shall contact the CDFG immediately in the case of a dead, injured or entrapped kit fox. The CDFG contact for immediate assistance is State Dispatch at (916)445-0045. They will contact the local warden or Mr. Paul Hoffman, the wildlife biologist, at (530)934-9309. The Service should be contacted at the numbers below.
13. The Sacramento Fish and Wildlife Office and CDFG shall be notified in writing within three working days of the accidental death or injury to a San Joaquin kit fox during project related activities. Notification must include the date, time, and location of the incident or of the finding of a dead or injured animal and any other pertinent information.
The Service contact is the Chief of the Division of Endangered Species, at the addresses and telephone numbers below. The CDFG contact is Mr. Paul Hoffman at 1701 Nimbus Road, Suite A, Rancho Cordova, California 95670, (530) 934-9309.
14. New sightings of kit fox shall be reported to the California Natural Diversity Database (CNDDB). A copy of the reporting form and a topographic map clearly marked with the location of where the kit fox was observed should also be provided to the Service at the address below.
Any project-related information required by the Service or questions concerning the above conditions or their implementation may be directed in writing to the U.S. Fish and Wildlife Service at: Endangered Species Division
2800 Cottage Way, Suite W2605
Sacramento, California 95825-1846
(916) 414-6620 or (916) 414-6600
STANDARD RECOMMENDATIONS 8
EXHIBIT “A” - DEFINITIONS
"Take" - Section 9 of the Endangered Species Act of 1973, as amended (Act) prohibits the "take" of any federally listed endangered species by any person (an individual, corporation, partnership, trust, association, etc.) subject to the jurisdiction of the United States. As defined in the Act, take means " . . . to harass, harm, pursue, hunt, shoot, wound, kill, trap, capture, or collect, or attempt to engage in any such conduct". Thus, not only is a listed animal protected from activities such as hunting, but also from actions that damage or destroy its habitat. "Dens" - San Joaquin kit fox dens may be located in areas of low, moderate, or steep topography.
Den characteristics are listed below, however, the specific characteristics of individual dens may vary and occupied dens may lack some or all of these features. Therefore, caution must be exercised in determining the status of any den. Typical dens may include the following: (1) one or more entrances that are approximately 5 to 8 inches in diameter; (2) dirt berms adjacent to the entrances; (3) kit fox tracks, scat, or prey remains in the vicinity of the den; (4) matted vegetation adjacent to the den entrances; and (5) manmade features such as culverts, pipes, and canal banks.
"Known den" - Any existing natural den or manmade structure that is used or has been used at any time in the past by a San Joaquin kit fox. Evidence of use may include historical records, past or current radiotelemetry or spotlighting data, kit fox sign such as tracks, scat, and/or prey remains, or other reasonable proof that a given den is being or has been used by a kit fox. The Service discourages use of the terms ”active” and “inactive” when referring to any kit fox den because a great percentage of occupied dens show no evidence of use, and because kit foxes change dens often, with the result that the status of a given den may change frequently and abruptly.
"Potential Den" - Any subterranean hole within the species’ range that has entrances of appropriate dimensions for which available evidence is insufficient to conclude that it is being used or has been used by a kit fox. Potential dens shall include the following: (1) any suitable subterranean hole; or (2) any den or burrow of another species (e.g., coyote, badger, red fox, or ground squirrel) that otherwise has appropriate characteristics for kit fox use. "Natal or Pupping Den" - Any den used by kit foxes to whelp and/or rear their pups.
Natal/pupping dens may be larger with more numerous entrances than dens occupied exclusively by adults. These dens typically have more kit fox tracks, scat, and prey remains in the vicinity of the den, and may have a broader apron of matted dirt and/or vegetation at one or more entrances.
A natal den, defined as a den in which kit fox pups are actually whelped but not necessarily reared, is a more restrictive version of the pupping den. In practice, however, it is difficult to distinguish between the two, therefore, for purposes of this definition either term applies.
STANDARD RECOMMENDATIONS 9
"Atypical Den" - Any manmade structure which has been or is being occupied by a San Joaquin kit fox. Atypical dens may include pipes, culverts, and diggings beneath concrete slabs and buildings.
UC Davis
Recent Work
Title
Effects of roads on San Joaquin kit foxes: a review and synthesis of existing data Permalink
https://escholarship.org/uc/item/0qd5t2p9
Author
Bjurlin, Curtis D.
Publication Date
2003-08-24
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ICOET 2003 Proceedings 397 Making Connections
EFFECTS OF ROADS ON SAN JOAQUIN KIT FOXES:
A REVIEW AND SYNTHESIS OF EXISTING DATA
Curtis D. Bjurlin (Email: [email protected]) and Brian L. Cypher, Endangered Species Recovery Program, P.O. Box 9622, Bakersfield, CA 93389
Abstract: Roads have a variety of adverse impacts on wildlife populations and can seriously impact rare species.
Numerous roads are present throughout the range of the endangered San Joaquin kit fox (Vulpes macrotis mutica), and many more are planned. We review existing literature and data to assess potential impacts from roads on kit fox conservation and recovery. In addition, we discuss mitigation strategies with their potential benefits.
Introduction
In the United States, over 200 million vehicles are in use on approximately 6.2 million kilometers of public roads (Natural Research Council 1997). Roads result in a number of environmental impacts, including endangerment of wildlife populations. The direct impacts of vehicle-related mortality and habitat loss have long been recognized. Lalo (1987) estimated that about one million vertebrates are killed by vehicles each day in the United States, and Forman (2000) calculated that approximately 1 percent of the land area, roughly the size of South Carolina, is paved. Additional direct effects include habitat fragmentation, disturbance and stress, contaminants, and destruction of shelter (Hourdequin 2000). Roads also may indirectly impact wildlife by altering ecosystem processes, such as changes in prey availability, competition, non-native species colonization, fire regime, and human access and associated development. Direct and indirect impacts may be detectable over one kilometer (0.6 mi) from roads resulting in a “road-effect zone” (Forman and Deblinger 1998), and leading one author to estimate that approximately 19 percent of the total area of the conterminous United States is affected (Forman 2000). Not surprisingly, road effects have been detected for a number of rare species including gray wolves (Canis lupus; e.g., Thiel 1985), Florida panthers (Felis concolor coryi; e.g., Maehr et al. 1991), desert tortoises (Gopherus agassizii; e.g., Boarman 1996), and Sonoran pronghorn (Antilocapra Americana sonoriensis; e.g., Castillo-Sáchez 1999). While impacts on common species are undesirable, road-related depletion of threatened and endangered species is particularly troubling and warrants careful evaluation and management.
A diversity of threatened and endangered animal species occur in the San Joaquin Valley of California (U.S.
Fish and Wildlife Service 1998). Most are rare due to habitat loss from agricultural, industrial, and urban development. Among them is the endangered San Joaquin kit fox (Vulpes macrotis mutica), a small, nocturnal canid that has undergone an estimated 95 percent reduction in habitat (Grinnell et al. 1937, Hall 1981, Mercure et al. 1993, U.S. Fish and Wildlife Service 1998). While the effects of roads on San Joaquin kit foxes have not been directly evaluated, the relatively large space requirements and high mobility of this species makes road crossings likely throughout much of their current range. Furthermore, the human population in the San Joaquin Valley is expected to nearly triple in the next 40 years (Great Valley Center 2000), with associated construction of new roads, expansion of existing roads, and increased traffic volumes.
Some of the potential impacts on San Joaquin kit foxes are obvious and direct, such as vehicle strikes, habitat loss associated with road construction, habitat loss associated with concomitant industrial and urban development, landscape fragmentation, disturbance, and environmental contamination. Others are more subtle and indirect, such as invasions by non-native species, changes in prey availability, predator abundance, or fire regime. The aforementioned could have a variety of detrimental effects on kit foxes, including mortality, morbidity, disrupted social ecology, reduced productivity, displacement, altered space use, inhibited dispersal, reduced genetic exchange, and decreased carrying capacity.
Our objectives are to (1) summarize available data on the direct and indirect effects of roads on populations of San Joaquin kit foxes, (2) identify factors that exert the greatest influence on kit fox conservation and recovery efforts, and (3) identify critical information needs for future research and mitigation.
Direct Effects
Vehicle Strikes
The majority of vehicle strikes occurs at night when many species are more active and driver visibility is at its lowest. For an animal the size of a kit fox, such strikes are typically fatal. If vehicle strikes were sufficiently frequent in a given locality, they could result in reduced fox abundance. Furthermore, the death of adult foxes during the breeding and pup-rearing seasons (Dec-May) negatively affects reproductive success and could result in the litter failure.
ICOET 2003 Proceedings 398 Making Connections
The proportion of deaths attributable to vehicle strikes rarely exceeds 10 percent for adult foxes (table 1).
Clearly, the number and type of roads passing through fox habitat play an important role in determining impact.
In the city of Bakersfield where roads were abundant, 23 percent of 35 adult kit fox mortalities and 17 percent of 25 juvenile mortalities were confirmed vehicle strikes. Furthermore, an additional 9 percent of adult and 8 percent of juvenile mortalities were suspected strikes. At this urban site where coyotes and bobcats were rare, vehicles were the most commonly attributable source of mortality. In natural lands, predators remain the primary cause of mortality for both adult and juvenile foxes (Briden et al. 1992, Standley et al. 1992, Ralls and White 1995, Spiegel and Disney 1996, Cypher et al. 2000).
Habitat Loss and Fragmentation
Paved roads are essentially permanent structures, and any habitat in the occupied area is therefore lost. The placement of a road also can fragment habitat into smaller blocks. This fragmentation effect is more likely with certain road configurations, such as multi-lane divided highways, or those with median barriers and adjacent fencing. Habitat loss and fragmentation can cause decreases in fox abundance through changes is social ecology, productivity, space use, dispersal, and survival.
Table 1
Proportion of mortalities attributable to vehicle strikes for kit and swift foxes.
While the historic and current habitat loss directly attributable to roads is unknown, estimates of the converted area under the jurisdiction of Caltrans include 239ha for Kings County, 431ha for Merced County, 817ha for Fresno County, and 1,485ha for Kern County (K. Hau, California Department of Transportation, personal communication). These estimates are based on a standard lane width of 3.6 m, and not all of this area is in kit fox habitat. However, the estimates are limited to state roads and do not include road shoulders, medians, or associated developments (e.g., interchanges, signs), which significantly increase the affected area. Of equal or greater significance is the habitat loss from urban and industrial development that has been induced by road construction.
Habitat fragmentation likely has two profound effects: (1) reduction in suitability of habitat and (2) disruption of movements, dispersal, and gene flow. Roads reduce habitat suitability by creating patches that are too small for effective use by foxes and that increase the probability of local extirpation due to stochastic events.
Estimates of the average home range size of a kit fox vary from 4.3km2 (Koopman et al. 2001) to 11.6 km2 (White and Ralls 1993), making it difficult to estimate patch size necessary to support a small population.
The probability of patch recolonization will depend upon the fragmenting artifacts (e.g., roads, canals, development). Large roads with high traffic volume can be impermeable to kit foxes. Knapp (1978) monitored movements of radio-collared foxes in Kern County in the vicinity of Interstate 5, a high volume four-lane highway. Numerous individuals used areas within 3km of the interstate, and most exhibited parallel movement and home range patterns. However, only on two occasions were foxes located on the opposite side of the highway from their primary areas of use.
Species Location Landuse Period Age # Mortalities % Vehicle Strike Citations Kit Fox Kern County, CA Oilfield 1980-95 Adult 225 9% Cypher et al. 2000 Kit Fox Kern County, CA Oilfield 1980-95 Juvenile 142 8% Cypher et al. 2000 Kit Fox Kern County, CA Natural Land 1989-93 Combined 31 3% Spiegel and Disney 1996
Kit Fox Kern County, CA Oilfield 1989-93 Combined 29 0% Spiegel and Disney 1996
Kit Fox Kern County, CA Natural Land 2001-03 Adult 14 7% Cypher unpub. data Kit Fox Kern County, CA Natural Land 1989-91 Combined 22 5% Ralls and White 1995 Kit Fox Monterey and San Luis
Obispo Counties, CA
Military
Reservation 1988-92 Adult 35 6% Standley et al. 1992
Kit Fox Monterey and San Luis
Obispo Counties, CA
Military
Reservation 1988-92 Juvenile 14 0% Standley et al. 1992 Kit Fox Merced County, CA Natural Land 1985-87 Combined 17 12% Briden et al. 1992 Kit Fox Bakersfield, CA Urban 1997-2003 Adult 35 23% Cypher unpub. data Kit Fox Bakersfield, CA Urban 1997-2003 Juvenile 25 17% Cypher unpub. data Swift Fox Alberta, Canada Natural Land 1987-91 Combined 89 6% Carbyn 1998 Swift Fox Western Kansas unknown 1996-97 Adult 18 0% Sovada et al. 1998 Swift Fox Western Kansas unknown 1996-97 Juvenile 14 28% Sovada et al. 1998 ICOET 2003 Proceedings 399 Making Connections
Movement and dispersal corridors are critical to kit fox population dynamics, particularly because this species currently exists as a metapopulation consisting of multiple disjunct population centers. Movement and dispersal linkages are important for alleviating over-crowding and intraspecific competition during years when fox abundance is high and are essential for recolonization. Movement between population centers also maintains gene flow, reducing the probability of inbreeding, genetic drift, and founder effects.
Disturbance
Construction, maintenance, and operational activities associated with roads may result in a disturbance effect on nearby kit foxes. Disturbance can result from noise, vibration, odors, or human activity and can range from subtle to profound. Potential impacts include: (1) disrupted sensory perception leading to decreased ability to locate prey or detect predators, (2) induced stress leading to physiological or behavior changes, and (3) resultant changes in natural history including, energetic requirements, reproductive output, immunological function, productivity, space use patterns, displacement, and even death.
Kit foxes may not be significantly impacted by disturbance, even when the source is continuous. Kit foxes appear to acclimate quickly to disturbances and exhibit a high degree of tolerance. At the Naval Petroleum Reserves in California, foxes frequently used areas near petroleum production facilities (e.g., well pads, gas plants, offices) where noise, vibrations, odors, and human activity were common (Cypher et al. 2000).
Similarly, Spiegel and Small (1996) found that kit foxes continued using a highly developed oil field where sulfurous gases were ubiquitous. Kit foxes at Camp Roberts frequently foraged and denned in areas that were subject to high human and vehicular traffic (Berry et al. 1992). Most notably, populations are known to inhabit the cities of Bakersfield and Taft, and in Bakersfield individuals likely number in the hundreds (Cypher submitted). Kit foxes in urban environments are continuously subjected to high levels of vehicular traffic, human activity, noise, and vibrations. Yet, these foxes successfully forage, locate mates, breed, rear young, and disperse.
Den Loss
Unlike most other canids, kit foxes use dens year-round on a daily basis (Koopman et al. 1998). Earth moving or vehicular traffic during road work jeopardizes kit fox dens. Because dens are of critical importance to avoid temperature extremes, rear young, and escape from predators (Seton 1925, Grinnell et al. 1937), den loss can result in displacement and altered space use patterns, leading to changes in social ecology and survival.
Individual kit foxes use numerous dens in the course of a year (Koopman et al. 1998). Therefore, the loss of one or even several dens within an individual’s home range may not constitute a significant impact.
However, foxes appear to have moderate fidelity to natal dens, the loss of which could be more detrimental.
Finally, earth moving and off-road traffic typically occurs during the day, a time when foxes are resting within dens. This could result in fox entombment and death.
Although the construction of roads may result in the loss of some dens, earth moving can create new denning opportunities. In Bakersfield, numerous kit fox dens have been located in the embankment of Highway 99, and several of these have served as natal dens. This is not surprising because kit foxes favor sloped locations for denning (Berry et al. 1987a, Reese et al. 1992). However, den sites along roads increase the risk of vehicle strikes, particularly when used to rear young. Egoscue (1962) reported that many of the kit foxes killed by vehicles on a study area in Utah were using dens near roads, and most of these were juveniles. This increased risk likely offsets any beneficial effect of increased den-site availability.
Contaminants
Roads contaminate natural lands in a variety of ways (see Forman et al. 2003 for a review). Substances used in road building or reconditioning can leach into adjacent habitat. Heavy metals (lead, aluminum, iron, cadmium, copper, manganese, titanium, nickel, zinc, and boron) and organic pollutants (dioxins, polychlorinated biphenyls) are all emitted in vehicle exhaust and may be higher in adjacent soils (Benfenati et al. 1992, Trombulak and Frissell 2000). Ozone levels are higher in the air near roads (Trombulak and Frissell 2000), and vehicles also leak hazardous substances (lubricants, antifreeze). Furthermore, a wide variety of pollutants could be introduced during small spills or catastrophic accidents.
Kit foxes using areas adjacent to roads could be exposed to contaminants through inhalation, dermal contact, direct ingestion, and ingestion of contaminated flora or fauna. Exposure to contaminants could cause short- or long-term morbidity, possibly resulting in reduced productivity or even mortality. Carcinogenic substances could cause genetic damage, sterility, reduced productivity, or reduced fitness among progeny in foxes or their prey.
Little information is available on the effects of contaminants on fox demographics. Morbidity or mortality likely would occur after animals have left the contaminated site, and more subtle effects such as genetic damage could only be detected through intense study and monitoring. However, at the Naval Petroleum Reserves in ICOET 2003 Proceedings 400 Making Connections
California, three kit foxes are known to have died by drowning in spills of crude oil (Cypher et al. 2000). Also, Spiegel and Disney (1996) reported a fox that was covered with crude oil and later died, despite treatment.
Indirect Effects
Reduced Prey Availability
Road construction, maintenance, and operation could result in a local reduction in prey availability, indirectly affecting kit fox populations. Potential causes include direct mortality associated with construction activities or vehicle strikes, habitat loss or degradation, disturbance, contaminants, or alteration of adjacent vegetation communities. Reduced prey availability could cause fox avoidance of adjacent lands, reduced productivity, and in extreme cases morbidity or mortality.
Little information is available on the effects of roads on kit fox prey. Foxes primarily prey upon rodents, leporids, and insects, but will opportunistically eat a variety of natural and anthropogenic foods (Knapp 1978, Spiegel et al. 1996, White et al. 1996, Cypher et al. 2000). Disturbed habitats adjacent to roads may provide conditions favorable to colonization by California ground squirrels (e.g., Balestreri 1981, Hall 1983). California ground squirrels can displace giant kangaroo rats (Dipodomys ingens) as well as other kangaroo rats and San Joaquin antelope squirrels (Ammospermophilus nelsoni) that are commonly consumed by foxes (D. Williams, Endangered Species Recovery Program, pers. comm., Taylor 1916; Harris and Stearns 1991).
Increased Competition
Habitat modification associated with road construction and operation may create conditions more favorable for native species that compete for resources or kill kit foxes. Increased predation risk or decreased prey availability could reduce fox habitat quality and local carrying capacity, or exclude kit foxes altogether. At the Naval Petroleum Reserves in California, shrub density increased along roads, possibly due to increased moisture from precipitation runoff (pers. obs). Dense shrubs are known to provide cover for coyotes (Canis latrans) and bobcats (Lynx rufus) (Ralls and White 1995, White et al. 1995, Cypher and Spencer 1998, Warrick and Cypher 1998). Also, utility lines frequently are installed along roads and dramatically increase perching and nesting sites for raptors (Knight et al. 1995, 1999). Golden eagles occasionally kill kit foxes (Briden et al. 1992) and raptors and owls compete with foxes for food resources. Roads also may serve as travel corridors for other kit fox competitors, such as red foxes.
Invasive Species
Construction and maintenance of roads can sometimes facilitate the invasion of non-native species that flourish in disturbed environments. Roads also enable invasive species to hitchhike on vehicles and livestock into otherwise remote landscapes. Non-native plants and animals may reduce habitat quality for kit foxes or their prey. A particularly problematic species within the range of the San Joaquin kit fox is yellow star thistle (Centaurea melitensis), dense stands of which form along roadsides and then spread into adjacent habitat.
Yellow star thistle competes with native plants for resources, does not appear to be used by kit fox prey, and may be difficult for foxes to move through due to its large size (up to 1m tall), dense growth habit, and numerous sharp spines. Other species of invasive flora include mustards (Brassica spp.) and Russian thistle (Salsola tragus) (Tellman 1997), but the effects of these plants on kit foxes or their prey species have not been assessed.
Nitrogen deposition from vehicle exhaust is another important factor that appears to promote growth of nonnative flora, particularly exotic grasses (Weiss 1999). These grasses, such as red brome (Bromus madritensis rubens), create dense ground cover in the San Joaquin Valley, and may reduce habitat quality for certain rodents (e.g., kangaroo rats) that are important prey for kit foxes (Goldingay et al. 1997, Cypher 2000).
Roads also may serve as travel corridors for non-native red foxes, as has been reported in Australia (Bennett 1991). Red foxes kill and exclude kit foxes (Ralls and White 1995, Clark 2001) and likely compete for food and dens (Cypher et al. 2001). However, red foxes are only infrequently observed in large blocks of undisturbed habitat within the range of the San Joaquin kit fox, possibly due to the absence of anthropogenic water sources or the presence of coyotes.
Increased Public Access
Roads are established to facilitate human travel and commerce. Although posting adjacent lands or installing fences may reduce human use, they do not prevent it completely. While recreating on natural lands, people engage in a variety of activities that are detrimental to kit foxes, including illegal shooting or trapping, legal and illegal hunting of prey species, habitat destruction and degradation (e.g., off-road vehicle use), den destruction, and illegal dumping.
ICOET 2003 Proceedings 401 Making Connections
Most effects from increased public access have not been quantified, and can only be inferred. However, illegal fox hunting has been reported on several occasions and typically occurs near roads. While only one fox was found shot at the Naval Petroleum Reserves in California during 1980-95 (Cypher et al. 2000), Morrell (1972) reported that during a one-year period at NPRC, five of six fox deaths were caused by gunshot wounds. Four kit foxes were found shot at the Lokern Natural Area in western Kern County (Spiegel and Disney 1996), two at the California Aqueduct in Kern County (K. Brown, California Department of Water Resources, personal communication), and one in the Santa Nella area (S. Clifton, Endangered Species Recovery Program, personal communication). Most illegal kills are likely never discovered; therefore, the effect of this source of mortality on kit foxes is difficult to assess.
Associated Development
While human population and economic growth precipitates road construction, roads also can have a growthinducing effect by increasing access to lands desirable for development. Development along roads commonly begins as transportation services, and later urban and industrial centers. Associated developments range from very small (1-2ha) to extensive (1km2), ultimately producing entire cities in some cases.
Associated development produces all of the negative effects to kit foxes discussed above, the most significant of which are habitat loss, fragmentation, and degradation. Because associated development cannot always be accurately predicted, the long-term cumulative effects are likely underestimated in environmental reviews of road construction projects.
Changes in Fire Regime
Roads often are a source of wildfire in arid lands, with dramatic effects on ecosystem processes. Vehicle sparks, overheating engines and brakes, arson, and accidental ignition all contribute to increased fire frequency. In some landscapes where lightning strikes traditionally were rare, anthropogenic wildfires have dramatically altered vegetation, reducing vertical structure and creating conditions that are suitable for invasive species.
Because foxes maintain well-insulated dens throughout their home ranges, it is unlikely that they frequently die in wildfire. However, much of the kit fox’s geographic range is dominated by shrubs and grasses, and frequent burns will make grasslands more common. Furthermore, changes in vegetation affect abundance of fox prey and predators. For example, both coyotes and leporids (desert cottontail and black-tailed jackrabbit) are known to favor shrublands in the southern San Joaquin Valley. The effect of fire upon kit fox ecology and life history is currently unknown, but significant impacts are to be expected as these relationships are investigated.
Potential Mitigation Strategies
Compensation for Loss of Habitat
Compensating for habitat loss is a mitigation strategy commonly implemented for kit foxes. This strategy involves protecting habitat of like or better quality in return for authorization to alter, disturb, or destroy habitat in another location. The amount of compensatory habitat required typically exceeds 1:1. This strategy has several shortcomings. First, new habitat is rarely created as a result of mitigation, so compensation results in a net loss of available lands. Second, there is an implicit assumption that the carrying capacity on compensatory habitat can be increased through habitat management such that the total carrying capacity across all lands remains unaffected. This assumption has never been validated and is questionable. Third, compensation is only required for the amount of habitat physically disturbed during road construction. Roads precipitate a slew of associated impacts described above for which compensation is rarely requested.
Avoidance of Important Habitats
Impacts to kit foxes can be reduced during the planning process by selecting project sites that avoid areas that are required for recovery of the species. Such areas include core and satellite populations and movement corridors. Understandably, there may be limited options in selecting the route for a proposed road. However, avoiding routes that transect large blocks of habitat would reduce detrimental effects significantly. A clear drawback to this strategy is increased project costs and decreased efficiency resulting from alternate routes. Rerouting of roads was identified as a key strategy to avoid fragmenting wildlife habitats in the Rocky Mountains (Reed et al. 1996) and also to avoid increased mortality to Florida scrub-jays (Mumme et al. 1999).
Den Avoidance
Den avoidance is a common mitigation strategy employed on projects in kit fox habitat. Typically, work sites are prescreened for fox dens, and care is taken during construction to avoid sensitive areas. Den avoidance may be difficult when a kit fox den lies within the path of a proposed road. From a cost-benefit perspective, rerouting a road around a den is rarely feasible. If the den is currently active and the occupants do not leave ICOET 2003 Proceedings 402 Making Connections
voluntarily, relocation may be necessary. As mentioned previously, dens in the vicinity of roads may increase the risk of vehicle strikes, and this potential impact should be considered when deciding whether to protect dens or relocate occupants.
Relocation
Foxes are rarely relocated because of well-documented negative impacts, including low survival probability (Scrivner et al. 1993), injury, and attempted return to the area of origin. The release can either be “hard”, whereby foxes are immediately released, or “soft”, whereby foxes are released after a period (of days to months) of acclimation in a holding pen. A number of conditions must be met prior to relocation. First, the release site must be of suitable condition and size to support the number of transplanted individuals. Second, relocation must not negatively impact resident foxes at the release site. Third, if ongoing genetic studies identify distinct subpopulations, then foxes should only be moved within subpopulations and not between them. An optimal release site would be one that is occupied by kit foxes, but where the fox population currently is below carrying capacity. To be considered successful, relocated foxes should remain in the release area and exhibit survival rates similar to that of resident foxes. Several attempted relocation efforts were insufficiently monitored (Jensen 1972, Knapp 1978, Hansen 1988, Paveglio and Clifton 1988) or deemed unsuccessful (Scrivner et al. 1993).
Relocation may be appropriate when a small, isolated block of habitat occupied by kit foxes will be unavoidably fragmented by a road project. Additionally, persistent endangerment may be cause for relocation. For example, individuals occasionally return to denning and foraging sites that have recently been destroyed.
Kit foxes continued to forage in the median of Highway 99 in Bakersfield after all vegetation had been removed (Perry Coy, California Department of Transportation, Fresno), while others were entombed after excavating and occupying a den on a construction site in Bakersfield (Endangered Species Recovery Program unpublished data).
Artificial Dens
Construction of artificial dens may be appropriate where den destruction is unavoidable or road construction has resulted in increased risk of predation. A variety of artificial den designs have been built or proposed.
These designs range from a simple length of pipe placed above ground, to complex buried chambers and tunnels with multiple entrances. Use by kit foxes or other species rarely has been monitored and optimal den designs have not been identified. However, dens should be of appropriate size to exclude predators, provide additional burrowing options, and provide sufficient thermal protection.
Exclusionary Fencing
While exclusionary fencing likely would reduce vehicle strikes it is not appropriate for all roads. Unless crossing structures are available, fencing will increase negative impacts associated with habitat fragmentation. Along smaller roads (e.g., 2-lane roads) or larger roads with lower traffic volumes where the risk of vehicle strikes is not high, it would be better to allow kit foxes to cross roads to maintain movement corridors and facilitate local space use patterns.
Wildlife Overpasses and Underpasses
Overpasses and underpasses are being created with greater frequency for wildlife. Designs range from small culverts under roads to 200-m-wide overpasses that are planted with natural vegetation. The creation of crossing structures could benefit kit foxes. Individuals have been observed to use bridges in order to cross roads and canals (pers obs.). Foxes also regularly enter pipes and culverts, although their use for road crossing has not been documented. Underpasses likely would be the most appropriate structures, particularly because many roads within the range of the kit fox are on raised beds. The dimensions of underpasses probably would need to be at least 0.5m high and 0.5m wide to be used by kit foxes. To maintain normal daily movement patterns in occupied habitat, underpasses probably should be spaced at least every 0.5 km. Exclusionary fencing along roads with underpasses would be necessary to encourage foxes to use the structures.
Reduced Speed Limits
Reduced vehicle speeds through kit fox habitat is a simple and effective strategy to avoid incidental mortality.
Reduced speed limits along one - or two-lane roads were credited with reducing the number of kit foxes killed by vehicles at the Naval Petroleum Reserves in California (Cypher et al. 2000) and at the Midway-Sunset oilfield (Spiegel and Disney 1996). This strategy will be more difficult to implement and enforce on larger roads with high traffic volumes. A related strategy is the use of signs along roads to warn drivers of the possible presence of kit foxes. Such signs are commonly used for other wildlife species (e.g., deer crossing signs), but their efficacy is debated.
ICOET 2003 Proceedings 403 Making Connections
Summary and Conclusions
The construction, operation, and maintenance of roads can have a variety of potential impacts on endangered San Joaquin kit foxes. While vehicle strikes have received the most attention, other negative effects may exert greater force on fox population dynamics. In natural lands, vehicle strikes rarely exceed ten percent of known mortality. When populations are robust, this may not significantly impact abundance, but where small populations are susceptible to local extirpation, roadkills may be of greater concern.
Habitat loss, fragmentation, and degradation associated with road activities likely has the greatest affect on fox populations. The long and narrow configuration of roads results in a considerable disturbance perimeter.
Perimeter effects on wildlife are well documented and with the San Joaquin kit fox result in increased probability of road crossings, exposure to contaminants, and access to habitat by people. Furthermore, high traffic volume roads with no crossing structures can effectively stop fox dispersal, resulting in local extirpation and genetic damage. Fragmentation of remaining habitat poses one of the largest obstacles to kit fox recovery.
The growth-inducing effect of roads also presents a serious concern. Development that occurs along linear rights-of-way causes habitat loss, fragmentation, and degradation that can be orders of magnitude greater than that caused by road work. The potential impacts from associated development sometimes are recognized in assessments of project-specific “cumulative effects,” but no additional compensation or mitigation is required.
Other impacts associated with roads likely affect San Joaquin kit foxes on a relatively local scale. Although these local effects do not threaten the range-wide kit fox population, the cumulative effect of localized impacts could be substantial. Over time, these cumulative effects could affect kit fox conservation and recovery efforts.
A variety of potential mitigation strategies exist. Relatively few have been implemented for San Joaquin kit foxes, and virtually no data are available on mitigation efficacy. Many of the strategies that reduce detrimental impacts to habitat also help reduce kit fox mortality from vehicles. The following should be considered where roads and critical habitat or linkages coexist: (1) careful site selection for proposed projects, routing through non-habitat where possible, (2) habitat compensation, (3) road overpass and underpass structures, (4) exclusionary fencing, and (5) den avoidance or supplementation. Fox relocation is rarely successful or advisable. Future research needs include (1) quantifying factors that contribute to vehicle strikes of kit foxes, (2) assessing the effects of roads on fire ecology, (3) assessing invasions by non-native species along roads, and (4) evaluating the efficacy of mitigation strategies.
Acknowledgements: This manuscript was prepared with support from California Department of Transportation (Caltrans) and U.S.
Department of Energy. Cheryl Johnson of Caltrans was instrumental in funding this work. We thank Carie Wingert and Scott Phillips for providing data summaries.
Biographical Sketches: Curtis Bjurlin is a wildlife biologist with the Endangered Species Recovery Program. He has been working with mammals and reptiles in arid lands for six years.
Brian Cypher is a research ecologist with the Endangered Species Recovery Program and has been working on kit fox ecology and conservation since 1990.
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URBAN ROADS AND THE ENDANGERED SAN
JOAQUIN KIT FOX
FINAL REPORT SUBMITTED TO THE
CALIFORNIA DEPARTMENT OF TRANSPORTATION
CONTRACT NUMBER 65A0136
Prepared by:
Curtis D. Bjurlin, Brian L. Cypher, Carie M. Wingert, and Christine L. Van Horn Job California State University, Stanislaus
Endangered Species Recovery Program
1900 Gateway Blvd.
Fresno, CA 93727
Prepared for:
The California Department of Transportation
July 10, 2005
esrp_urbanroad_sjkf.doc
STATE OF CALIFORNIA DEPARTMENT OF TRANSPORTATION
TECHNICAL REPORT DOCUMENTATION PAGE
TR0003 (REV. 10/98)
1. REPORT NUMBER
FHWA/CA/IR-2006/01
2. GOVERNMENT ASSOCIATION NUMBER 3. RECIPIENT’S CATALOG NUMBER
5. REPORT DATE
July 2005
4. TITLE AND SUBTITLE
Urban Roads and the Endangered San Joaquin Kit Fox 6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Curtis D. Bjurlin, Brian L. Cypher, Carie M. Wingert, and Christine L. Van Horn Job
8. PERFORMING ORGANIZATION REPORT NO.
None
10. WORK UNIT NUMBER
9. PERFORMING ORGANIZATION NAME AND ADDRESS
California State University-Stanislaus
Endangered Species Recovery Program
1900 N. Gateway Blvd., Suite 101
Fresno, CA 93727
11. CONTRACT OR GRANT NUMBER
65A0136
13. TYPE OF REPORT AND PERIOD COVERED
Final, July 2001-June 2004
12. SPONSORING AGENCY AND ADDRESS
California Department of Transportation
Sacramento, CA 95819 14. SPONSORING AGENCY CODE
15. SUPPLEMENTAL NOTES
16. ABSTRACT
The San Joaquin kit fox (Vulpes macrotis mutica) is at risk of extinction primarily due to profound habitat degradation, fragmentation, and loss. However, kit foxes inhabit some urban areas, and roads present a potential threat to kit foxes in these areas. From 1998-2004, we investigated the effects of roads on urban kit foxes in Bakersfield, California. Vehicles were the primary cause of mortality for urban kit foxes, and most strikes occurred on arterial roads, which had higher traffic volumes and speed limits. Also, foxes were more frequently struck near intersections between major roads and other linear rights-of-way (e.g., railroads, canals, other roads), which likely were used as travel corridors by kit foxes. Males appeared to be particularly vulnerable to vehicle strikes during the winter mating season. Kit foxes did not appear to avoid roads when selecting den sites.
During nocturnal activity periods, kit foxes commonly crossed local roads, but less frequently crossed arterial or collector roads. Roads impact urban kit foxes through reduced survival, occasional den loss, inhibited movements, and habitat loss.
When conducting road projects (e.g., construction, maintenance), Caltrans implements standard measures to minimize impacts to kit foxes. We recommend the implementation of additional measures, specifically the installation of artificial dens and road crossing structures, to further minimize impacts. Implementation of these measures will facilitate conservation of urban kit foxes and contribute to range-wide recovery.
17. KEY WORDS
Artificial den, Bakersfield, conservation measures,
crossing structure, endangered species, road, San
Joaquin kit fox, urban environment, vehicle, Vulpes
macrotis mutica
18. DISTRIBUTION STATEMENT
No restrictions. This document is available to the public through the National Technical Information Service,
Springfield, VA 22161
19. SECURITY CLASSIFICATION (of this report)
Unclassified
20. NUMBER OF PAGES
47 21. PRICE
i
URBAN ROADS AND THE ENDANGERED
SAN JOAQUIN KIT FOX
Curtis D. Bjurlin, Brian L. Cypher, Carie M. Wingert, and Christine L. Van Horn Job California State University, Stanislaus
Endangered Species Recovery Program
1900 Gateway Blvd.
Fresno, CA 93727
TABLE OF CONTENTS
Technical Report Documentation Page ........................................................................... i Table of Contents.............................................................................................................. ii Table of Tables.................................................................................................................iv List of Figures................................................................................................................... iv Disclosure.......................................................................................................................... vi Disclaimer ......................................................................................................................... vi Executive Summary........................................................................................................ vii Acknowledgments..........................................................................................................viii Introduction....................................................................................................................... 1 Information Need...................................................................................................................... 1 Goal ............................................................................................................................................ 3 Study Area ................................................................................................................................. 3 Methods.............................................................................................................................. 4 Kit Fox Capture and Monitoring ............................................................................................ 4 Mortality .................................................................................................................................... 5 Dens............................................................................................................................................ 7 Movements................................................................................................................................. 7 Spatial and Statistical Analysis................................................................................................8 Results................................................................................................................................ 8 Results................................................................................................................................ 9 Urban Kit Fox Ecology............................................................................................................. 9 Mortality .................................................................................................................................... 9 Dens.......................................................................................................................................... 17 Movements............................................................................................................................... 19 Discussion......................................................................................................................... 20 ii
Mortality .................................................................................................................................. 20 Dens.......................................................................................................................................... 21 Movements............................................................................................................................... 22 Conclusions...................................................................................................................... 23 Future Research.............................................................................................................. 24 Literature Cited .............................................................................................................. 25 Appendix. Supplemental recommendations for protection of San Joaquin kit fox during road projects in urban environments............................................................... 26 Introduction............................................................................................................................. 26 Den Disturbance...................................................................................................................... 26 Summary............................................................................................................................................. 26 Urban Kit Fox Den Description.......................................................................................................... 27 Artificial Den Description................................................................................................................... 28 Artificial Den Installation Criteria ...................................................................................................... 29 Kit Fox Road Crossing Structures ........................................................................................ 29 Summary............................................................................................................................................. 29 Road Crossing Structure Attributes .................................................................................................... 29 Profiled Crossing Structures............................................................................................................... 34 Literature Cited ...................................................................................................................... 47 iii
TABLE OF TABLES
Table 1. Cause of death for all foxes (1985-2004) and foxes with transmitting radio signals at time of death (1997-2004), Bakersfield, CA............................................................................................................. 11 Table 2. Frequency of fox-vehicle collisions by road type for all foxes and those with transmitting radio signals at time of death, Bakersfield, CA, 1998-2004......................................................................... 11 Table 3. Fox-vehicle collisions by posted speed limit, Bakersfield, CA, 1998-2004.................................. 12 Table 4. Observed versus random generated fox-vehicle collisions on arterial and collector roads that were within one road width (26m) of an intersection with a linear right-of-way, Bakersfield, CA, 1998- 2004. ................................................................................................................................................... 16
LIST OF FIGURES
Figure 1. Urbanized San Joaquin kit fox study area, Bakersfield, CA. ......................................................... 4 Figure 2. Minimum convex polygon of fox-vehicle collisions for individuals that had transmitting radio collars, Bakersfield, CA, 1998-2004..................................................................................................... 6 Figure 3. Nocturnal (a) and Diurnal (b) locations of San Joaquin kit fox in Bakersfield, CA, 1998-2004. 10 Figure 4. Fox-vehicle collisions by traffic volume for all mortalities and mortalities of individuals with transmitting radio collars at time of death, Bakersfield, CA, 1998-2004............................................ 12 Figure 5. Fox-vehicle collisions by gender and month, Bakersfield, CA, 1998-2004................................. 13 Figure 6. Fox-vehicle collisions (1998-2004) versus scent marking rates (Murdoch 2004) for male foxes, Bakersfield, CA................................................................................................................................... 14 Figure 7. Fox-vehicle collisions (1998-2004) versus interactions with foxes that were not within the immediate social group (Murdoch), Bakersfield, CA. ........................................................................ 14 Figure 8. Mean (Std. Dev.) traffic volume by month at six control stations, Bakersfield, CA, 2003.......... 15 Figure 9. Fox-vehicle collisions and road segments where mortality occurred, Bakersfield, CA, 1998-2004. ............................................................................................................................................................ 16 Figure 10. Number of known dens by distance to nearest centerline of major road, Bakersfield, CA, 2001- 2004. ................................................................................................................................................... 17 Figure 11. Drainage culvert under Highway 99 in Bakersfield, CA that was used as a den by San Joaquin kit fox.................................................................................................................................................. 18 Figure 12. Kit fox dens at varying distances from collector and arterial roads in Bakersfield, CA, 2001- 2004. ................................................................................................................................................... 18 Figure 13. Kit fox dens at varying distances from collector and arterial roads, Bakersfield, CA, 2001-2004.
A barrier wall, indicated with dashed line, isolated dens from one roadway with relatively high traffic volume. ............................................................................................................................................... 19 Figure 14. Earthen kit fox dens in urban Bakersfield, CA. a) Single entrance den under building foundation. b) Natal den complex on canal bank. c) Multi-entrance den in drainage basin bordering intersection of two arterial roads. d) Single entrance den in vacant lot............................................... 36 Figure 15. Non-earthen den locations for kit foxes in Bakersfield, CA. a) Fox emerging from stacked pipe. b) Narrow entrances to a kit fox den under a storage container. c) Fox resting beside stacked lumber at a construction site. d) Fox returning to a den within a modular housing unit. ............................... 37 Figure 16. Camouflaged earthen kit fox dens in urban Bakersfield, CA. a) Entrance to den in landscaping at parking lot. b) Thatch covered den entrance in a golf course fairway. c) Dirt mound from den in shrub-island at park............................................................................................................................. 38 Figure 17. Artificial subterranean dens for San Joaquin kit fox at Bakersfield, CA. a) Artificial den schematic. b) PVC two-entrance chamber den under construction. c) High-density polyethylene twoentrance den. d) PVC tunnel with floor removed longitudinally. ...................................................... 39 Figure 18. Artificial escape dens for San Joaquin kit fox at Bakersfield, CA. a) Escape den schematic. b) High-density polyethylene escape den under construction. c) Completed den. d) Kit fox entering escape den. .......................................................................................................................................... 40 Figure 19. Kit fox pups at artificial subterranean dens at a golf course (a) and drainage basin (b) in Bakersfield, CA................................................................................................................................... 41 Figure 20. Railroad underpass on highway 99 in Bakersfield, CA. a) Habitat view. b) Kit fox natal den at the top of the underpass embankment................................................................................................. 41 iv
Figure 21. Barrier wall to encourage use of road crossing structures for the San Joaquin kit fox in urban environments. The roadside embankment allows foxes that are trapped on the roadway to clear the barrier wall. a) Cross-section view. B. Three-dimensional rendering............................................... 42 Figure 22. Buena Vista Road golf cart crossing structure, Bakersfield, CA. a) Aerial view of roadkill and radio-tagged kit fox locations at crossing structure. b) Habitat view from east entrance of crossing structure. c) Approach view to east entrance. d) Passage interior...................................................... 43 Figure 23. Truxtun Extension horse culvert, Bakersfield, CA. a) Aerial view of radio-tagged kit fox locations at horse culvert. b) View from pedestrian trail at south culvert entrance (canal in background). c) North culvert entrance. Yellow line depicts extent of fencing on north side of road. d) Culvert interior................................................................................................................................ 44 Figure 24. Coffee Road overpass at Kern River bicycle trail, Bakersfield, CA. a) Aerial view of kit fox roadkill and radio-tagged night locations at crossing structure. b) Habitat view from west entrance. c) East entrance to bicycle path on southern embankment of Kern River. d) View of roadway from East with location of kit fox roadkill in red. No fences prevent fox access to roadway on eastern side. ............................................................................................................................................................ 45 Figure 25. Highway 58/Fruitvale Avenue canal bridge, Bakersfield, CA. a) Aerial view of radio-tagged kit fox night locations at crossing structure. b) East entrance to Fruitvale Bridge obstructed by water. c) South entrance to highway 58 bridge. d) Dirt embankment under Highway 58 Bridge. .................... 46 v
Urban Roads and the Endangered San Joaquin Kit Fox
DISCLOSURE
This research was done under contract 65A0136. The contract total was $170,700.
DISCLAIMER
The contents of this report reflect the views of the authors who are responsible for the facts and accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the State of California or the Federal Highway Administration. This report does not constitute a standard, specification, or regulation. vi
Urban Roads and the Endangered San Joaquin Kit Fox
EXECUTIVE SUMMARY
The San Joaquin kit fox (Vulpes macrotis mutica) is at risk of extinction primarily due to profound habitat degradation, fragmentation, and loss. Industrial and urban developments are contributing factors to habitat destruction. Based on recent research, however, kit foxes appear to have persistent populations in some urban and industrial lands. While many factors regulate urban fox populations, roads are a dominant feature of these areas, and a potential threat to kit fox populations. Roads may affect fox survival, den use, movements, and other essential functions. Furthermore, the potential for negative impact is proportional to road width, traffic volume, and speed limit.
Projections for the San Joaquin Valley indicate that the human population and associated urbanization and transportation networks will increase for the foreseeable future. Roads will grow wider, carry higher traffic volumes, and become more inhospitable to wildlife.
As urban lands spread and natural lands diminish, urbanized fox populations also may become more valuable to species recovery. Consequently, the influence of transportation networks on the persistence of urban fox populations will grow simultaneously to the importance of those populations. Identifying ways to reduce the impact of urban roads on the kit fox is therefore important to species recovery.
The goal of this project was to examine effects of transportation networks (particularly roads) on urbanized San Joaquin kit foxes. Fox-vehicle collision was the primary cause of mortality for urban kit foxes and most strikes occurred on arterial roads that had relatively higher traffic volumes and posted speed limits. Fox-vehicle collision also showed temporal and spatial variability. Foxes more frequently were struck near intersections between major roads and other linear rights-of-way, including railroads, golf courses, canals, rivers, and other roads of all sizes. Furthermore, male kit foxes died disproportionately on roads during winter when mating, territory defense, and exploratory movements were common.
Kit foxes did not show preference for or avoidance of dens with respect to proximity to major roads (arterial, collector, highway, and highway ramp). A 100ft buffer (Fish and Wildlife Service exclusion zone) from the centerline of major roads included 9.5% of known kit fox dens at the study site. Proximity of dens (especially natal sites) to major roads, however, may increase risk of vehicle strike. Furthermore, earth moving associated with road construction and improvement may endanger kit foxes that inhabit roadside dens. Finaly, land that is converted to roadway is permanently lost as kit fox habitat. Therefore, while the selection of den sites by kit fox did not appear influenced by road proximity, there were several impacts of roads on the availability and suitability of habitat for dens.
We report on 21 sessions of vehicle-based intensive monitoring with 15 different focal kit foxes. In all, we recorded 4,633 minutes of observation over 44,121m of minimum straight line distance (MSLD) between consecutive points. Using MSLD and observation time, we calculated that foxes traveled at an average rate of 0.5958 km/hr during intensive monitoring. We directly observed foxes crossing local roads on 10 occasions and arterial and collector roads on one occasion, each. MSLD predicted that foxes made vii
Urban Roads and the Endangered San Joaquin Kit Fox
108 road crossings during monitoring. The majority (79 crossings) occurred on local roads, while 12 and 17 crossings occurred on arterial and collector roads, respectively.
Rate of road crossing per road type was in direct contrast to frequency of fox-vehicle collision per road type. Foxes most frequently crossed local roads, but most frequently died on arterial roads.
In addition to analyzing the effects of roads on kit foxes, we provide detailed recommendations on protection and compensation measures for urban road projects.
Specifically, we discuss the criteria for and construction of artificial dens and road crossing structures. These measures, when judiciously applied, may increase fox survival, habitat connectivity, and likelihood of persistence of urban fox populations.
ACKNOWLEDGMENTS
In addition to California Department of Transportation funding, the U.S. Bureau of Reclamation, California Department of Fish and Game, Great Valley Center, ARCO Western Energy, and Chevron USA provided valuable financial support for the urbanized kit fox ecology research project. Additional support was provided by the Smithsonian Institute, U.S. Department of Energy, U.S. Fish and Wildlife Service, and City of Bakersfield. J. Storlie was integral to the early development of this project. We thank S.
Bremner-Harrison, A. Brown, J. Murdoch, and E. Tennant for ongoing field assistance.
All schematics in this report came from the pen of S. Harrison. S. Phillips’ expertise with GIS and report preparation were invaluable. Finaly, we thank H. Hunt (Caltrans), S.
Jones (USFWS), and T. Marshall (Caltrans) for reviewing draft versions of this report. viii
Urban Roads and the Endangered San Joaquin Kit Fox
INTRODUCTION
INFORMATION NEED
The San Joaquin kit fox historically occupied arid upland habitats throughout the San Joaquin Valley. Former and current conversion of these lands to agriculture, urban, and industrial uses has resulted in profound habitat degradation, fragmentation, and loss. As a result, the San Joaquin kit fox was listed as Federally Endangered in 1967 and California Threatened in 1973 (U.S. Fish and Wildlife Service 1998).
Kit foxes currently persist in a metapopulation consisting of 3 large “core” populations (Carrizo Plain National Monument, LoKern Natural Area, Panoche Hills region) and a number of smaller “satellite” populations. Movement of foxes between these populations is important for maintaining gene flow and avoiding inbreeding effects. Furthermore, kit fox populations exhibit marked fluctuations in the number of individuals as a result of natural and anthropogenic processes (e.g., Cypher et al. 2000). Risk of extinction due to catastrophic or random demographic events is increased for small populations in general and kit foxes specifically (White et al 2000). Thus, dispersal between populations may be necessary to prevent local extinctions or to recolonize lands where foxes are extirpated. The probability of long-term persistence of this species will increase with the number and stability of populations and the ability of animals to move between these areas.
Bjurlin and Cypher (2003) identified numerous potential impacts of roads on kit fox populations. While vehicle strike is the most obvious and documented, roads also may degrade or fragment habitat, increase chemical or noise pollution, alter prey or predator abundance, introduce invasive species, cause changes to fire regime, and increase human presence and development. The aforementioned have a variety of potential impacts on foxes, including mortality or morbidity, disrupted social ecology, reduced productivity, displacement, altered space use, inhibited dispersal, reduced genetic exchange, and decreased carrying capacity.
One study (Cypher et al., in prep) found few impacts of two-lane highways on kit fox ecology in natural lands. Probability of fox-vehicle collision was low, perhaps as a result of low traffic volumes (approximately 8,000 vehicles per day) and few vehicles during periods of peak fox activity. Similarly, there was no evidence that foxes avoided territories that bordered or crossed the roads, had decreased reproductive output along roadsides, encountered changes in availability or utilization of prey, or were more at risk from predation. Road presence, and associated human activity did significantly alter fire regime, increasing the frequency of wildfire, and changing native Atriplex spp. shrubland to non-native grassland. This change appeared to alter relative abundance of several Dipodomys spp., the primary prey of resident foxes. Furthermore, distribution (and perhaps abundance) of the coyote (Canis latrans) also was altered, with coyotes preferentially utilizing shrub remnants (Nelson et al., in prep). Clearly, potential impacts by roads are diverse, and perhaps mediated by other ecosystem processes (i.e., fire).
Furthermore, as road width, traffic volume, and speeds increase, the potential for direct impacts, such as vehicle strike will increase. Roads throughout the range of the San 1 Urban Roads and the Endangered San Joaquin Kit Fox
Joaquin kit fox are increasing in traffic volume. Therefore, lack of direct impact on San Joaquin kit fox as reported above is not necessarily indicative of future relationships between the kit fox and human transportation networks. For a synthesis of the literature on road impacts on San Joaquin kit fox refer to Cypher (2000) and Bjurlin and Cypher (2003).
The highest density of roads, peak traffic volume, and greatest potential for impact to foxes occurs in urban areas. Urban kit fox populations in California minimally occur in Bakersfield, Taft, Santa Nella, and Coalinga. Reports from the public and carcasses collected opportunistically indicate that kit foxes are dying by vehicle strike in the human developments of the Southern San Joaquin Valley. Urbanized foxes may encounter roads while foraging, looking for mates, defending territories, and dispersing. Little is known, however, about the factors that influence where, when, and how vehicle strikes occur.
Furthermore, it is unknown whether there are changes to kit fox use or placement of dens, patterns of movement, susceptibility to predation, prey selection, or other elements of fox ecology as a consequence of proximity to roads in urban areas.
Why is the impact of urban roads on kit fox populations important? First, urban areas have rapidly grown throughout the range of the kit fox. In some cases, development has occurred in agricultural lands that long have been devoid of kit foxes. But in many other cases, urbanization has displaced or altered fox populations occurring in natural lands.
Conversion of natural lands permanently decreases availability of habitat, which is a major obstacle to species recovery. Second, the network of three core- and several satellite-populations identified in the recovery plan for this species is vulnerable to fragmentation associated with transportation networks. For this metapopulation to remain functional, individuals must be able to move between sub-populations. The potential for negative impact of roads on the ability of foxes to utilize corridors may be proportional to road width, traffic volume, and speed limit. Projections for the San Joaquin Valley indicate that the human population and associated urbanization and transportation networks will increase for the foreseeable future. The highest potential for fragmentation will occur in urbanized areas where roads are most prevalent. Third, as urban lands spread and natural lands diminish, urbanized fox populations may become more valuable to species recovery. Urban fox populations are relatively less susceptible to meteorological stochasticity, and may prove useful as a repository for genetic diversity and/or individuals for reintroduction efforts. Consequently, the influence of transportation networks on San Joaquin kit fox recovery is likely to grow simultaneously to the importance of urbanized fox populations where transportation networks are most prevalent. Identifying ways to reduce the impact of urban roads on the kit fox is therefore a conservation priority.
A less tangible, but still important, reason to reduce the impact of roads on urban fox populations is the interaction between urbanized kit foxes and the public. Standardized surveying shows that the citizens of Bakersfield (where the largest population of urbanized foxes occurs) generally have seen a kit fox on one or more occasions and support protection of the urban population (Bjurlin and Cypher, in press). Furthermore, respondents expressed widespread appreciation of urbanized foxes (in some cases becoming strongly protective). The greatest concern identified by respondents was that kit foxes would be killed by vehicle strike. Furthermore, fox-vehicle collision, or the 2 Urban Roads and the Endangered San Joaquin Kit Fox
attempt to avoid it, may in some cases contribute to traffic accidents (unconfirmed citizen report) or unsafe road conditions. Measures designed to minimize kit fox crossing of busy roads at grade are likely to receive strong public support. To the extent that pedestrian and fox crossing structures can be combined for multiple use, the perceived benefits of this investment in infrastructure are likely to increase.
GOAL
Our goal was to determine whether roads affect the ecology of the urbanized San Joaquin kit fox. From 1997-2004, we outfitted kit foxes with radio transmitters and monitored survival, den use patterns, and movements. We examined these data for statistical and spatial associations to urban road networks. Based upon these results we provide detailed recommendations for the protection of San Joaquin kit foxes in urban environments during and after road projects. If implemented, these recommendations are likely to contribute to the long-term viability of urban fox populations and species recovery, receive strong public support, and may even increase public safety.
STUDY AREA
The study site is located in the southwestern quarter of the Bakersfield metropolitan area (Figure 1). Bakersfield lies at the southern end of the San Joaquin Valley in central California and is the Kern County seat of government. The metropolitan area as of January 2003 was approximately 580 km2
(224 mi
2 ) with 394,234 residents
(http://www.bakersfieldchamber.org/pdf/community-profile.pdf). The urbanized area of Bakersfield grew by 23.6% from 1990-2000 and continued growth is expected (http://factfinder.census.gov/home/saff).
Hot, dry summers, and cool, wet winters characterize the climate of the southern San Joaquin Valley. Average daily maximum temperatures range from 14°C in December to 37°C in July and average daily minimum temperatures range from 4°C in December to 21°C in July (Meadows Field Airport weather station). Annual precipitation averages
14.3 cm, but varies greatly between years.
3 Urban Roads and the Endangered San Joaquin Kit Fox
METHODS
KIT FOX CAPTURE AND MONITORING
From May 1997 to July 2004 we captured kit foxes in live traps, outfitted them with radio transmitters, and monitored them for sources of mortality, nightly movements, daily resting places, and reproductive output. We captured foxes with wire-mesh box traps (38 x 38 x 107 cm) baited with assorted meats. Traps were covered with cloth tarps to protect animals from inclement weather and direct sun. Captured foxes were examined for injury and parasites, ear-tagged, sexed, aged, and fitted with a radio collar (40g, Advanced Telemetry Systems, Isanti, Minnesota) containing a mortality sensor that altered signal pulse rate if the animal was motionless for four hours. We released foxes at site of capture after 0.5-1 hour of handling. Capture and handling protocols were in accordance with permits TE023496-1 and TE825573-2 from the U.S. Fish and Wildlife Service and a Memorandum of Understanding from the California Department of Fish and Game.
Figure 1. Urbanized San Joaquin kit fox study area, Bakersfield, CA. 4 Urban Roads and the Endangered San Joaquin Kit Fox
At a minimum, we attempted to record one day-resting location and two night-activity locations for each animal with a functioning radio collar during each week. In some cases fewer locations were recorded because of collar failure, fox dispersal from typical home ranges, use of resting sites that attenuated radio signal, or other factors. Radio collar transition to mortality signal allowed us to promptly retrieve deceased foxes and increased the likelihood of confirming cause of mortality. Fox carcasses also were collected opportunistically during the study when spotted on roads, reported by citizenry, or collected by other organizations. Each spring, we conducted natal den observations to estimate litter size for all radio-tagged females. Finally, we collected kit fox feces for dietary analysis throughout the study duration. Locations of activity, mortality, resting, and pup whelping and rearing were recorded with GPS and entered in a GIS for spatial analysis.
MORTALITY
We conducted necropsy for all recovered fox carcasses. We limited our analysis of cause of death to animals that were actively being monitored with radio telemetry in order to decrease bias caused by differences in visibility of carcasses. We also report, however, on all carcasses retrieved during the study. Cause of death was determined using the pattern of injury, including external abrasion, broken bones, internal hemorrhaging, and bite wounds. The location that the carcass was retrieved from also was used in determining cause of death (e.g., within road right-of-way, buried at construction site, in carnivore scrape, etc.).
For all animals (transmitting or not) that died by vehicle strike, we assigned road type (local, collector, arterial, highway), traffic volume, and posted speed limit. Local roads had the primary purpose of providing access to abutting residential property, did not exceed 12.2m (40ft) in width, had no more than one traffic lane in each direction, and were not longer than 0.8km (0.5mile) without interruption. Speed limit was 25mph on all local roads, but was not always posted. Collector roads generally conducted local road traffic to the arterial road network, but sometimes were residential in nature. Speed limits (generally 30-45 mph) for collector roads were based upon speed surveys and were posted. Arterial roads had 1-3 lanes of traffic in each direction (typically more than one), carried the majority of city traffic, and connected the local and collector road networks to the State highway system. Arterial road speed limits (35-55mph) were always based on speed surveys and posted. Lastly, highways were State numbered roads with the primary purpose of conducting traffic into and away from the urban area. They included highways 58, 99, 178, and 119 and in some cases passed through residential, commercial, and industrial areas. Vehicle access to highway 99 and portions of 178 was by ramp only.
We compared road type where foxes died to an expected distribution based on road availability using contingency table analysis. Road availability was calculated by summing the length of three road types (local, collector, arterial) within the minimum convex polygon of the locations of vehicle strike (Figure 2). Vehicle strikes also were examined for temporal patterns. For this analysis we limited the time period to 6 complete years, 07/01/1998-06/30/2004 so that months wouldn’t be disproportionately represented. Strikes were separated by fox age (adult, juvenile) and gender (male, 5 Urban Roads and the Endangered San Joaquin Kit Fox
female) and compared with other sources of morality by month. Temporal distribution in strikes was compared with frequency of fox scent marking, interaction with foxes outside of social group (Murdoch 2004), and traffic volume by month.
Finally, we examined spatial patterns of kit fox vehicle strikes that occurred on arterial or collector roads. We had insufficient sample size to conduct similar analyses for local and highway strikes. We limited the extent of this analysis to southwest Bakersfield where we had the greatest knowledge of roads and fox habits. Strikes were examined for association with intersections of the road where the mortality occurred and other linear rights-of-way. Linear rights-of-way for this analysis were defined as other roads (local, collector, arterial, highway), canals, railroads, rivers, or golf course crossings.
Figure 2. Minimum convex polygon of fox-vehicle collisions for individuals that had transmitting radio collars, Bakersfield, CA, 1998-2004. 6 Urban Roads and the Endangered San Joaquin Kit Fox
In order to conduct this spatial analysis, we defined vehicle strike road segments. These segments were the shortest sections of road that were bounded by intersection with other arterial or collector roads and contained the vehicle strike location. This rule was modified when the mortality occurred at an intersection with arterial or collector road. In these cases, the segment was extended in both directions to the next, nearest intersection with a major road. We then assigned 100 randomly distributed points to the road segment for each vehicle strike. For example, if three strikes occurred on the segment, 300 randomly distributed points were assigned. We calculated the distance to nearest intersection with linear right-of-way for all points (confirmed strike and random).
Distance was coded into three categories, near (x <= 26m), intermediate (26m < x <= 52m), and far (52m < x) based on a mean road width of 26m. Therefore, strikes assigned as “near” occurred within one road width of the intersection, as “intermediate” within two road widths, and as “far” greater than two road widths.
Observed strikes versus random locations were examined with this coding scheme in a contingency table analysis for a departure from what would be expected by chance.
Lastly, we evaluated the type of intersections where vehicle strikes occurred for strikes coded as “near”. We then compared the frequency of observed mortalities and random points among intersection types.
DENS
Association between confirmed kit fox dens and major roads (highway, highway ramp, arterial, and collector) was examined for dens used by radio-collared foxes from 1 July 2001 to 30 June 2004. Distance to nearest road centerline was calculated for each known den and compared across distance categories (34.5m, 69m, etc.). Distance categories corresponded with Fish and Wildlife exclusion zone distances for known kit fox dens (34.5m = 100ft).
MOVEMENTS
Kit fox space use was studied using vehicle-based monitoring of focal animals during 2003. Focal sessions typically began 1 or more hours after nightfall (full dark) and lasted for approximately four hours. Every 15 minutes we attempted to collect a new location for the focal animal. We described fox locations as accurately as possible using a combination of triangulation and spotlighting. With these data we calculated minimum straight-line distance (MSLD) between consecutive locations. We also calculated rate of travel (MSLD km/hour). Finally, we estimated number of road crossings (arterial, collector, local) using MSLD and visual sightings. We then adjusted these data for crossing rate per hour of observation and MSLD of movement. We used shapefile coverages of city roads and geo-referenced aerial photography to assign road crossings for this analysis.
7 Urban Roads and the Endangered San Joaquin Kit Fox
SPATIAL AND STATISTICAL ANALYSIS
Spatial analysis was conducted using ArcView version 3.2 (ESRI 1996). Data for roads and traffic volumes were generated with shapefile coverages from City of Bakersfield GIS and Traffic Engineering Departments, respectively (City of Bakersfield 2000-2004).
All spatial data were projected in Lambert Conformal Conic, California State Plane, NAD27. In some cases data on road location, size, or posted speed limit was unavailable for the year in which the kit fox feature was described (i.e., vehicle strike, den, movements). In these instances data from the closest available time period were used (usually less than one year distant). Geo-referenced aerial photography (AirPhoto USA) was used to assign the location of road intersections with other linear rights-of-way. All statistical analyses were performed using SPSS version 11.5 (SPSS Inc. 2002) and results were considered significant at P <= 0.05.
San Joaquin Kit Fox
8 Urban Roads and the Endangered San Joaquin Kit Fox
RESULTS
URBAN KIT FOX ECOLOGY
From May 1997 to July 2004 we captured a total of 358 individual foxes (109 adults, 206 juveniles, and 43 juveniles that were captured again as adults). Of these, we outfitted 229 individuals with radio collars (84 adults, 79 juveniles, and 66 juveniles that continued to be monitored as adults). We monitored radio-tagged animals until they died, transmitters failed, or they were lost. We collected 8,115 night activity locations and 6,647 daytime resting locations during the study (Figure 3a-b). Kit foxes primarily rested diurnally within dens, of which we described 471 over the study period. We located kit fox litters on 54 separate occasions. With these data we will conduct additional analyses on survival rates, reproductive rates, den site selection, space requirements, preferred habitats, and foraging patterns. We will present these data in a comprehensive monograph of kit fox demographics and ecology in urban environments. California Department of Transportation (Caltrans) will be supplied with a copy of the monograph and associated recommendations for the conservation of urban fox populations.
MORTALITY
We collected 156 kit fox carcasses from September 1985 to August 2004. Carcasses collected prior to 1997 were stored by California State University, Bakersfield. A near majority of mortalities were attributed to vehicle strike (48.1%, Table 1). These data, however, include animals that were received from a variety of opportunistic sources. By limiting analysis to animals that were actively being monitored with radio telemetry at time of death (N = 78) we reduce bias (e.g., differential reporting and accessibility to carcasses). Of this subset, confirmed vehicle strike accounted for 26.9% of mortality.
An additional 7.7% of foxes may have died from vehicle strike, but evidence, while suggestive, was not conclusive. Predation (16.7%) was the second most common cause of death for transmitting animals. Other sources of mortality included entombment, poison, drowning, gunshot, complications during parturition, and entanglement.
Due to advanced state of decay or lack of gross injury, we were unable to determine cause of death for 28.2% of carcasses. However, 73% of the 22 individuals with unknown cause of death were retrieved from fox dens. Pertinent to this report, animals retrieved from dens were unlikely to have died of vehicle strike (they lacked broken bones or contusions), and therefore the percentages calculated for vehicle strike are considered accurate when unknown cause of death is included. Overall, 30.8% of the 78 mortalities of foxes with operational radio collars were retrieved from dens. In natural lands where most research has been conducted and mortality generally is attributed to predation, carcasses are rarely retrieved from dens. There may be sources of mortality in urban environments (e.g., disease or poisoning) that have yet to be identified, but that do not leave clearly diagnostic evidence with our necropsy techniques. 9 Urban Roads and the Endangered San Joaquin Kit Fox
Figure 3. Nocturnal (a) and Diurnal (b) locations of San Joaquin kit fox in Bakersfield, CA, 1998-2004.
10 Urban Roads and the Endangered San Joaquin Kit Fox
Table 1. Cause of death for all foxes (1985-2004) and foxes with transmitting radio signals at time of death (1997-2004), Bakersfield, CA.
Cause of Death All Foxes Transmitting Foxes
N % N %
Entombed - construction 5 3.2 3 3.8
Entombed - natural 1 0.6 1 1.3
Poison 3 1.9 0 0.0
Possible poison 5 3.2 4 5.1
Predation 16 10.3 13 16.7
Possible predation 5 3.2 4 5.1
Vehicle 75 48.1 21 26.9
Possible vehicle 8 5.1 6 7.7
Other 6 3.8 4 5.1
Unknown 32 20.5 22 28.2
Total 156 100.0 78 100.0
Table 2. Frequency of fox-vehicle collisions by road type for all foxes and those with transmitting radio signals at time of death, Bakersfield, CA, 1998-2004.
Road Type All Strikes Transmitting Strikes
N % N %
2-lane local 2 4.2 1 5.6
2-lane collector 8 16.7 1 5.6
2-lane arterial 2 4.2 1 5.6
4-lane arterial 17 35.4 7 38.9
6-lane arterial 16 33.3 7 38.9
6-lane highway 1 2.1 0 0.0
Not on road 2 4.2 1 5.6
Total 48 100.0 18 100.0
From January 1998 to August 2004, we had the necessary information on road status to describe association between road types and vehicle strikes. We retrieved 48 vehicle strike kit foxes in Bakersfield during this period. Of these, 18 were actively being monitored with radio telemetry at the time of death. Arterial roads accounted for 72.9% and 83.3% of strikes for all animals and actively monitored animals, respectively (Table 2). Collector roads, local roads, and highways were less significant sources of mortality. Within the 100% MCP of actively monitored animals (Figure 2), we identified 327.4 km of local roads, 49.9 km of collector roads, and 50.9 km of arterial roads. There was a significant difference between the observed frequency of roadkill by road type, and that which would be expected based on availability (χ
2 2 = 82.127, P < 0.001). Arterial
roads were far more often a source of vehicle strike than can be explained by chance occurrence.
11 Urban Roads and the Endangered San Joaquin Kit Fox
Roads with four or more lanes accounted for 70.8% and 77.8% of roadkill for all animals and actively monitored animals, respectively (Table 2). Approximately 90% of roadkill were retrieved from roads with posted speed limits of greater than 45 mph, irrespective of whether the animal was transmitting at time or death or was collected opportunistically (Table 3). Roads with a 55 mph posted speed limit accounted for over half of all vehicle strikes. Mean traffic volume at vehicle strike was 21,861 and 23,426 vehicles per day for all strikes and actively monitored strikes, respectively (Figure 4).
Table 3. Fox-vehicle collisions by posted speed limit, Bakersfield, CA, 1998-2004.
Speed Limit All Strikes Transmitting Strikes
N % N %
25 mph 1 2.1 0 0
35 mph 1 2.1 0 0
40 mph 1 2.1 1 5.6
45 mph 9 18.8 2 11.1
50 mph 6 12.5 5 27.8
55 mph 27 56.3 9 50.0
65 mph 1 2.1 0 0.0
Not on road 2 4.2 1 5.6
Total 48 100.0 18 100.0
Figure 4. Fox-vehicle collisions by traffic volume for all mortalities and mortalities of individuals with transmitting radio collars at time of death, Bakersfield, CA, 1998-2004. 12 Urban Roads and the Endangered San Joaquin Kit Fox
There was no overall interaction between vehicle strike as cause of death (Coded Yes/No) and gender (χ
2 1 = 0.057, P = 0.812) or age (χ
2 1 = 0.709, P = 0.400) for 78 foxes
that were actively being monitored at time of death. Of 47 adult mortalities, 38.3% were either confirmed or possible vehicle strikes. Confirmed or possible vehicle strike accounted for 29.0% of 31 juvenile mortalities. Mortalities were evenly distributed between the genders (male = 39, female = 39), and approximately one third of each sex died of confirmed or possible vehicle collision. While all mortalities were distributed throughout the year, vehicle strikes showed a distinct peak in December during the sixyear period beginning 1 July 1998 (Figure 5). Further examination showed an association between gender, age, and vehicle strikes when the data were examined temporally. Of nine foxes that died of vehicle collision in December, seven were adult males. The winter (December/January) spike in male fox-vehicle collision corresponded with male rate of scent marking (Figure 6) and overall rate of interaction between focal foxes and conspecifics that were not within the social group (Figure 7). Both scent marking and interaction frequency may be indicators of reproductive behavior and territoriality (Murdoch 2004). There also appeared to be a smaller increase in vehicle strike from May to September. Many of these animals were pups that were at the age typical of increasing independence from the natal group, solitary foraging, and dispersal.
Vehicle traffic volume did not differ by month at six control stations spread across the urban area (Figure 8).
Figure 5. Fox-vehicle collisions by gender and month, Bakersfield, CA, 1998-2004. 13 Urban Roads and the Endangered San Joaquin Kit Fox
Figure 6. Fox-vehicle collisions (1998-2004) versus scent marking rates (Murdoch 2004) for male foxes, Bakersfield, CA.
Figure 7. Fox-vehicle collisions (1998-2004) versus interactions with foxes that were not within the immediate social group (Murdoch), Bakersfield, CA. 14 Urban Roads and the Endangered San Joaquin Kit Fox
We identified 23 segments of arterial or collector roads where strikes occurred. Number of strikes per segment ranged from 1 to 5 and accounted for 38 strikes in all (Figure 9).
Along these segments we identified 136 intersections. Kit foxes died more often than expected by chance at intersections with a linear right-of-way (χ 2 2 = 15.75, P < 0.001).
Strikes within one road width (<=26m) of an intersection accounted for 47.3% of all roadkill. In contrast, only 22.5% of random points occurred within one road width of an intersection. Following a similar, but weaker, trend 21.1% of observed roadkill were between one and two road widths (26 < x <= 52m) of an intersection, versus 17.8% of random locations in the category. There did not appear to be a higher risk of strike at any one type of intersection. Across intersection types, frequency of vehicle strikes that occurred in the category nearest to intersections mirrored the frequency of random points (Table 4). For example, 38.9% of all strikes within one road width occurred at intersection with local roads, while 37.1% of corresponding random points occurred at local road intersections.
Figure 8. Mean (Std. Dev.) traffic volume by month at six control stations, Bakersfield, CA, 2003.
15 Urban Roads and the Endangered San Joaquin Kit Fox
Table 4. Observed versus random generated fox-vehicle collisions on arterial and collector roads that were within one road width (26m) of an intersection with a linear rightof-way, Bakersfield, CA, 1998-2004.
Intersecting Linear Feature Observed Strikes Random Points N % N %
Arterial road 1 5.6 99 11.6
Canal 4 22.2 191 22.4
Collector road 3 16.7 69 8.1
Golf course 1 5.6 59 6.9
Highway 1 5.6 58 6.8
Local road 7 38.9 317 37.1
Railroad 0 0.0 17 2.0
River 1 5.6 44 5.2
Total 18 100 854 100.0
Figure 9. Fox-vehicle collisions and road segments where mortality occurred, Bakersfield, CA, 1998-2004.
16 Urban Roads and the Endangered San Joaquin Kit Fox
DENS
Kit foxes did not appear to avoid using dens or building dens at sites that were adjacent to major roads. We calculated nearest major road (arterial, collector, highway, or highway ramp) to each of 327 fox dens used from 1 July 2001 to 30 June 2004. Of these, 9.5% occurred within 30.4m (100ft) of the nearest road centerline. A similar trend occurred for each subsequent 30.4m distance from road (Figure 10). Some foxes utilized features of a major road for den construction. One individual was known to den within a culvert beneath highway 99 (Figure 11). Other dens occurred in the embankments or underpasses of a raised portion of highway 99 (Figure 20b, Appendix), and at drainage basins (e.g., Figure 14c, Appendix) or canals directly adjacent to roads.
In some cases dens were directly adjacent to the roadway (Figure 12), but in other cases roadside dens were behind by a cement block wall or other barrier that increased isolation, decreased noise pollution, and may have made the site less likely to be impacted by human activity (Figure 13). Dens directly adjacent to roads are at risk of disturbance during road maintenance or construction. Four dens within a drainage basin at the intersection of two arterial roads (Figure 14c) were destroyed during earth moving associated with road widening and improvement. In fact, the entire drainage basin was removed in this instance. Four frequently occupied fox dens were destroyed when a local road, Kroll Way, was extended through a previously un-roaded area.
Figure 10. Number of known dens by distance to nearest centerline of major road, Bakersfield, CA, 2001-2004.
17 Urban Roads and the Endangered San Joaquin Kit Fox
Figure 11. Drainage culvert under Highway 99 in Bakersfield, CA that was used as a den by San Joaquin kit fox.
Figure 12. Kit fox dens at varying distances from collector and arterial roads in Bakersfield, CA, 2001-2004.
18 Urban Roads and the Endangered San Joaquin Kit Fox
Figure 13. Kit fox dens at varying distances from collector and arterial roads, Bakersfield, CA, 2001-2004. A barrier wall, indicated with dashed line, isolated dens from one roadway with relatively high traffic volume.
MOVEMENTS
We conducted 21 sessions of vehicle-based intensive monitoring on 15 different focal kit foxes, for a total of 4,633 minutes of observation. We collected an average of 16.2 unique locations per session. Mean interval between locations was 15.14 minutes. By connecting these locations sequentially, we were able to calculate minimum straight-line distance (MSLD) moved and minimum rate of travel. We recorded a total of 44,121m of MSLD, for an average of 2,101m per monitoring session. Using MSLD and observation time, we calculated that foxes traveled at an average rate of 0.5958 km/hr during monitoring. Of course, focal foxes were inactive during much of the focal period and minimum distances between points do not account for the more complex travel patterns that were likely to exist. Therefore, foxes traveled a greater distance in shorter time and actual rate of travel likely was considerably higher.
MSLD movements also allowed us to estimate number of road crossings during focal sessions. We directly observed foxes crossing local roads on 10 occasions and arterial and collector roads on one occasion, each. MSLD predicted that foxes made 108 road crossings during focal monitoring. The majority (79 crossings) occurred on local roads, while 12 and 17 crossings occurred on arterial and collector roads, respectively. On average, foxes made 2.43 road crossings per km MSLD and 1.46 crossings per hour during intensive monitoring. Crossing rate for arterial roads (the primary location of roadkill) dropped to just 0.32 and 0.16 crossings per km MSLD and hour, respectively.
Intersection of arterial roads with MSLD occurred in only six monitoring sessions (five individual foxes).
19 Urban Roads and the Endangered San Joaquin Kit Fox
DISCUSSION
MORTALITY
As the single largest source of mortality for the Bakersfield fox population, vehicle strike clearly is an important factor for urbanized foxes. These data are in marked contrast with all other studies on kit fox in which vehicle strike rarely exceeded 10% of mortalities and was not considered a significant influence on fox demographics or population ecology (Bjurlin and Cypher 2003). In the largest study to date on the San Joaquin kit fox in natural habitats, Cypher et al. (2000) found that predation accounted for 57.2% of 222 fox deaths while vehicle strike was identified as cause of death in only 9% of occurrences. In contrast, predation during this urban study accounted for 16.7% of mortality, while vehicle strike, at 26.9%, was a more important cause of death. The coyote is the primary predator and competitor of the San Joaquin kit fox (Ralls and White 1995, Cypher and Spencer 1998) and is not abundant in Bakersfield (Cypher unpubl. data). Coyote distribution appeared limited to the Kern River corridor in the urban area included in this study. Therefore, it is possible that vehicle strike simply replaces mortality that would otherwise have been caused by depredation, had predators been more abundant. Indeed, some urban fox populations have persisted for decades and appear relatively stable given the dynamic alteration of urban environments that occurs during development and land conversion. Analyses of urban fox population viability and the impact of vehicle strike on viability are pending.
Arterial roads accounted for most strikes, a relationship that was significantly different from expected based on availability of this road type in the urban environment. Arterial roads typically have multiple lanes, relatively higher traffic volumes, and relatively higher posted speed limits. The San Joaquin kit fox is capable of rapid travel over short distances. The swiftness of this species may enable it to safely navigate two-lane roads where vehicle speeds and traffic volumes are lower. Indeed, only 10% of strikes occurred on roads that had posted speed limits that were lower than 45 mph. Low volume and speeds on local roads make it less likely that a fox crossing the road will need to avoid more than one vehicle. In contrast, a fox crossing four- or six-lane roads may have to evade multiple vehicles, which may travel in different directions and at different rates. Average traffic volume for urban roads with fox-vehicle collisions was nearly three times the volume of two-lane highways that transverse the LoKern Natural Area, one of three core areas for the San Joaquin kit fox (Cypher et al. in prep).
The incidence of vehicle strike was not evenly distributed. Foxes died more frequently within one road width of intersections between major roads and other linear rights-of-way then expected by chance. In fact, 68.4% of strikes on major roads occurred within two road widths of an intersection. The association between intersections and vehicle strike likely was the result of kit fox movement patterns. Species of the family Canidae (dogs, wolves, coyotes, foxes) utilize linear features for travel (Trewhella and Harris 1990), and we observed urban kit foxes on linear corridors between habitat patches (C. Bjurlin, pers. obs.). Additionally, increased traffic at intersections and regular changes in vehicle speed or direction (particularly where two roads come together) could make navigating intersections confusing for foxes. Finally, roadways typically are wider at road/road 20 Urban Roads and the Endangered San Joaquin Kit Fox
intersections to accommodate turning lanes. Greater distance to traverse equals greater time on the road and greater exposure to fox-vehicle collision. The lack of association of fox-vehicle collision with a specific type of intersection suggests that this relationship is broadly applicable.
Fox gender also was linked with vehicle strike when time of year was added as a variable. Males appeared particularly vulnerable during the breeding season (Dec-Jan).
Increases in male strikes closely mirrored rate of scent marking and interaction with animals outside of the social group (Murdoch 2004). During the reproductive season, male foxes are more active, travel greater distances, are more aggressive, and spend more time chasing females in courtship and males in territory defense (C.Bjurlin, pers. obs).
Furthermore, male foxes travel outside of the home territory in search of mating opportunities during December and January (Cypher et al., unpubl. data). One male in particular made these movements nightly for a period of a week and was observed successfully mating with a female in these new territories. While this example stands out in its detail, many males were observed in extra-pair copulation and outside of the typical home range during this study. On one occasion we witnessed four foxes in rapid and aggressive chase make their way through traffic on a collector road where several mortalities were known to have occurred. As interloper, transient foxes have to contend with similar agonistic interactions with resident males. It is likely that animals occupied with mating, aggressive interactions, or in unfamiliar territory are less aware of roads and traffic.
Vehicle strike during winter months also may be affected by shorter days and daylight savings time. Peak traffic volume occurs during morning and evening commutes. In the winter, the evening commute occurs up to two hours after sunset when male foxes are likely active and seeking mates. Fox activity and peak traffic volume have the greatest likelihood of overlap on the winter solstice (the shortest day of the year). Male vehicle strikes also appeared to be centered on the solstice. In contrast, traffic volume was constant throughout the year, so it is unlikely that monthly changes in traffic (e.g., holiday travel) contributed to patterns of fox mortality.
DENS
Kit foxes did not appear to prefer or avoid dens with respect to roads in urban environments. Urban land use is non-random and areas of similar zoning often are clumped. Kit foxes have shown preference for den sites with respect to some land uses.
Of the 471 dens described from 1997-2004, 36.3% were located along the banks of canals or water detention basins. These areas, however, accounted for only a small percentage of available land area in Bakersfield. It appears that open spaces, or lightly and infrequently disturbed areas (such as canals and basins) are more influential on kit fox den site selection than the proximity or size of adjacent roadways. It is possible that a positive or negative association with roads may occur as a result of a relationship between roads and other, desirable den sites. For example, many of the water transport canals in Bakersfield are adjacent to major roadways. This pattern may reflect a planned strategy, simple convenience, or historical artifact of past development. There is no current strategy for land planning in urban areas with regards to the San Joaquin kit fox. 21 Urban Roads and the Endangered San Joaquin Kit Fox
Therefore, future development practices may increase or decrease the likelihood that foxes will select den sites near roadways.
Den proximity to major roads may elevate the risk of mortality in some cases. One family group along a collector road in Bakersfield lost two of nine juveniles to vehicle strike in 2004. The natal dens in this instance were less than 20m from the road. Kit fox pups are active and relatively naïve to external dangers, particularly in the first six months of life. Urban foxes also quickly habituate to human and vehicle presence.
While the process by which juvenile foxes learn how to successfully cross roads is unknown, there likely is a period of learning and perhaps elevated risk during youth, particularly when juveniles increase in independence and begin to venture farther from the natal site in search of prey and territory.
Fox dens are destroyed during road construction or modification. Because dens are an essential resource for the kit fox (see Appendix), development projects should avoid dens whenever possible, compensate for den destruction, and secure the necessary permissions from State and Federal authorities when altering lands upon which kit fox exist. In particular, kit foxes can be entombed within dens during earth moving. Road construction projects in Bakersfield have the potential to affect 9.5% or more of dens that occur within 100 ft of major road centerlines. The percentage of affected dens would have been far greater had local roads been included in this analysis. The Fish and Wildlife Service requires that an exclusion zone be created around these dens unless permission is given for den disturbance or destruction. The loss of den sites also decreases the general suitability of habitat, both for resident and for transient animals.
Whenever dens are potentially affected by transportation projects, we strongly encourage the supplemental protection and compensation strategies that are described in the appendix to this document.
MOVEMENTS
Our data on the movements of radio-collared animals show that kit foxes frequently cross roads. The majority of crossings occurred on local roads, mirroring their relative abundance in urban areas, but the majority of mortalities occured on arterial and collector roads. Clearly, the low traffic volumes and speeds associated with local roads decreases the danger to kit fox. While these road types, cover extensive area with the range of the fox (thereby decreasing habitat availability), loss of habitat in urban areas may be unavoidable. We do not proposal specific conservation measures for local road construction to decrease fragmentation of urban landscapes.
Arterial and collector roads offer a greater challenge. These roads accommodate an everincreasing volume of traffic in Bakersfield and other southern San Joaquin Valley human population centers. Kit foxes have shown that they can successfully cross major roads, but many animals maintained territories that did not bring them into frequent contact. It is unclear how increases in traffic volume affect the ability of animals to disperse in urban environments, which is a critical function for healthy kit fox populations.
Crossings appear to be habitual in some cases – with individual foxes repeatedly using a few locations to navigate the roadway. That and the association between fox crossings, fox-vehicle collisions, and linear rights-of-way suggest that these intersections would be 22 Urban Roads and the Endangered San Joaquin Kit Fox
likely candidates for conservation measures. While reducing speed limits and road sizes would not be practical, it may be possible to reduce the likelihood of vehicle strike on arterial and collector roads by providing safe passage for foxes. Specifically, we propose that road modification projects include wildlife crossing structures where appropriate.
Criteria for selecting locations for crossing structures and instructions for building structures and associated infrastructure are provided in the appendix to this document.
CONCLUSIONS
Roads impact urban kit foxes. Fox-vehicle collision was the primary cause of mortality over a six-year intensive study of urban fox ecology. Because of the absence of predators in the urban environment, it is unclear whether vehicle strike was a limited factor for fox population growth, or simply a compensatory source of mortality for animals that would have been depredated had predator populations been robust. Analyses of survival and population viability are pending. Fox-vehicle collision spiked during the December reproductive season for male kit foxes. This spike in mortality may disrupt kit fox reproductive ecology by destabilizing pair bonds directly prior to whelping and rearing of young. Fox-vehicle collisions occurred more frequently than expected within one road width of an intersection with a linear right-of-way. Rights-of-way may be natural crossing locations for foxes due to habitual travel patterns. They also may be difficult to navigate safely due to wider roadways and irregular traffic speeds and directions. Kit foxes denned on roadsides at similar densities to more remote locations. Likewise, fox movements did not appear overtly affected by roads. Our study, however, was not specifically designed to test for an impact of roads on fox home range and dispersal patterns. An impact on either of these aspects of kit fox ecology is therefore unknown.
The effects of road construction and modification may be reduced by the installation of artificial dens and wildlife crossing structures as outlined in the appendix to this document. Efforts to conserve urban fox populations will contribute to the recovery of this endangered species. Because fox-vehicle collision is the primary source of mortality for urbanized foxes, changes to roads that decrease fox death should command a central role in future conservation programs.
23 Urban Roads and the Endangered San Joaquin Kit Fox
FUTURE RESEARCH
Based on the studies conducted to date by ESRP, further research and conservation efforts will benefit urban kit foxes. We have identified five topics for future investigation.
1) The factors that affect the suitability of urban habitats for kit fox are currently unknown. These factors may include road density, landuse (e.g., zoning), building density, and presence of refugia and/or corridors between habitat patches. A systematic census of kit fox in urban habitats (e.g., Bakersfield, Taft, Coalinga) using camera or hair traps is required to focus conservation and mitigation efforts in the areas that are of highest value. Previous urban fox research, while critical to identifying vital rates (births, deaths, migration), was not designed to rigorously test the variables that affect fox presence. Therefore, there is a significant data gap in this area.
2) Cause of death could not be determined for a number of foxes, and poisoning was strongly suspected in many of these cases. This question warrants further investigation to identify the types and sources of poisoning. 3) A recent pilot study has indicated that striped skunks, which are a host to rabies in the San Joaquin Valley, may present a future epidemiological threat to kit foxes in urban environments. Further research is required to quantify this threat and develop strategies to ameliorate it.
4) Conservation strategies have been identified that could potentially benefit urban kit foxes, such as road crossing structures, artificial dens, passages through walls and fences, and the construction of refugia and corridors in urban landscapes.
Further research on the efficacy of these strategies, and information packages detailing these strategies, would benefit urban kit foxes, city planners, and developers.
5) A recent survey indicated that Bakersfield residents harbored misconceptions regarding kit foxes and their population status (Bjurlin and Cypher, in press).
Resources directed toward developing and evaluating a coordinated outreach effort will benefit kit fox conservation in both urban and natural environments. 24 Urban Roads and the Endangered San Joaquin Kit Fox
LITERATURE CITED
Bjurlin, C.D., and B. L. Cypher. 2003. Effects of roads on San Joaquin Kit Foxes: A review and synthesis of existing data. Pages 397-406 in C.L. Irwin, P.Garrett, and K.P.McDermott, editors. 2003 Proceedings of the International Conference on Ecology and Transportation. Center for Transportation and the Environment, North Carolina State University, Raleigh, NC.
Bjurlin, C.D., and B. L. Cypher. In Press. Encounter frequency with the urbanized San Joaquin kit fox correlates with public beliefs and attitudes toward the species.
Endangered Species Update.
City of Bakersfield. 2000-2004. Geospatial data on roads and traffic volumes from Department of GIS and Traffic Engineering. http://www.bakersfieldcity.us/ Cypher, B. L., and K. A. Spencer. 1998. Competitive interactions between coyotes and San Joaquin kit foxes. Journal of Mammalogy 79:204-214.
Cypher, B.L. 2000. Effects of roads on San Joaquin kit foxes: a review and synthesis of existing data. Report for California Department of Transportation, Sacramento, California.
Cypher, B. L., G. D. Warrick, M. R. M. Otten, T. P. O’Farrell, W. H. Berry, C. E. Harris, T. T. Kato, P. M. McCue, J. H. Scrivner, and B. W. Zoellick. 2000. Population dynamics of San Joaquin kit foxes at the Naval Petroleum Reserves in California.
Wildlife Monographs 145. 43pp.
ESRI Inc. 1996. Arcview 3.2 for Windows. ESRI Inc., Redlands, CA.
Murdoch, J. D. 2004. Scent marking behavior of the San Joaquin kit fox (Vulpes macrotis mutica). M. S. Thesis. University of Denver, CO.
Ralls, K, and P. J. White. 1995. Predation on San Joaquin kit foxes by larger canids.
Journal of Mammalogy 76:723-729.
SPSS Inc. 2002. SPSS Base 10.0 for Windows User's Guide. SPSS Inc., Chicago IL.
Trewhella, W.J., and S. Harris. 1990. The effect of railway lines on urban fox (Vulpes vulpes) numbers and dispersal movements. J. Zool., Lond. 221:321-326 United States Fish and Wildlife Service. 1998. Recovery plan for upland species of the San Joaquin Valley, California. United States Fish and Wildlife Service, Region 1, Portland, Oregon. 319 pp.
White, P. J., W. H. Berry, J. J. Eliason, and M. T. Hanson. 2000. Catastrophic decrease in an isolated population of kit foxes. The Southwestern Naturalist 45:204-211. 25 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox APPENDIX. SUPPLEMENTAL RECOMMENDATIONS
FOR PROTECTION OF SAN JOAQUIN KIT FOX DURING
ROAD PROJECTS IN URBAN ENVIRONMENTS
Prepared by: Endangered Species Recovery Program
in cooperation with: U.S. Fish and Wildlife Service, Sacramento Field Office and the California Department of Transportation
July 2005
INTRODUCTION
The San Joaquin kit fox (Vulpes macrotis mutica) was listed as Federally Endangered in 1967 and California Threatened in 1973. Specific measures implemented to protect the kit fox for any given project shall be determined by the U.S. Fish and Wildlife Service (Service) based upon applicant consultation with the Service. The purpose of this document is to provide an introduction to measures that may reduce impacts of road construction or modification in urban environments. Specifically, we discuss the criteria for and construction of artificial dens and road crossing structures. The measures outlined in this document are supplemental to standard Service and Caltrans guidelines, which will not be repeated here. Furthermore, these procedures are subject to modification or revision at the discretion of Service. The recommendations made in this appendix are those of the authors and are based on the findings of this research project and other current knowledge of the San Joaquin kit fox. These procedures are applicable to all urban environments where kit foxes are present or will be present in the future. Kit fox presence has been confirmed in Bakersfield, Taft, Santa Nella, and Coalinga, but surveys have yet to be conducted elsewhere. Kit foxes are likely to be found now or in the future in other urban or urbanizing areas.
DEN DISTURBANCE
Summary
Dens are a vital resource to the kit fox in urban environments (Koopman et al. 1998).
Dens provide refuge from predators and climatic extremes, and a location to whelp and rear young. Urban kit foxes typically occupy dens diurnally, but may spend considerable time within dens during the night, especially immediately preceding parturition and in the months post-parturition when young are nursing and vulnerable to predation. In the following text we describe kit fox dens in urban environments and make recommendations for the treatment of dens when they are encountered at a work site. In addition, we provide criteria and instructions for the creation of fox-specific artificial 26 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox dens. The construction of artificial dens may in some cases offset the destruction or disturbance of dens or fox habitat during road projects.
Urban Kit Fox Den Description
Many Federal guidelines pertain to the “known den” (U.S. Fish and Wildlife Service 1999). A known den is defined as any existing earthen den or manmade structure that is used or has been used at any time in the past by a San Joaquin kit fox. Evidence of use may include historic records, past or current radio telemetry or spotlighting data, kit fox sign such as tracks, scat, and/or prey remains, or other reasonable proof that a den or structure is being or has been used by a kit fox. The U.S. Fish and Wildlife Service discourages use of the terms ”active” and “inactive” when referring to a kit fox den because occupied dens may show no evidence of use, and because kit foxes change dens often, with the result that the status of a given den may change frequently and abruptly.
Known dens in urban environments take a variety of forms. Most dens are earthen and have multiple entrances, occur in vacant or undeveloped lots, and appear similar to dens found in natural lands. Many earthen dens in urban environments, however, occur at atypical locations, such as dense landscaping, maintained lawns, building foundations, stacked materials, and canal, drainage basin, road or railroad embankments (Figure 14a-d).
Kit fox use of manmade structures presents a further complication when assessing fox presence in urban environments. Kit foxes regularly den within pipes, under storage containers, buildings with raised foundations, stacked materials, vehicles, or any other structure or object that offers shelter and is large enough for a fox to enter (Figure 15a-d).
Manmade structures may be permanent or temporary and may be occupied by kit fox for a single night or habitually. There may be little or no indication that a fox is present at the site. Because these features often are large and provide shelter without digging, typical sign of fox presence, such as dirt mounds, prey remains, or tracks, may be absent or obscured.
Detection and evaluation of kit fox dens in urban environments is challenging. Access to affected or adjacent properties may be restricted at the time of surveying. Irrigation associated with landscaping may degrade dirt mounds, prey remains, and tracks. In some cases dense thatch entirely obscures den entrances (Figure 16a-c). All potential earthen and manmade structures should be thoroughly inspected for sign of kit fox occupancy. In addition to standard procedures, the use of track plates and/or fiber-optic burrow probes may be necessary. Lastly, it is recommended that the surveying biologist interview local landowners, employees, and passersby about kit fox presence, den occupancy, and historic use of a potential project site. Local citizens often will have useful information on kit fox activity and habits that can focus survey efforts.
Natal dens, or dens where whelping and rearing of young occur, present a special circumstance that warrants increased protection. If a natal den is detected within or adjacent to the project site, all activities should immediately stop and the appropriate authorities should be notified. Natal dens typically have more entrances, tracks, scat, prey remains, and human garbage, and may have a broader apron of matted dirt and/or vegetation at one or more entrances (Figure 14b). As with non-natal dens, they may occur 27 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox in a wide range of circumstances, from earthen dens more typical of natural lands to manmade structures where presence of the family group is difficult to confirm without direct observation of young. If interviewed, local citizens often will provide detailed information on the whereabouts and historic use of natal dens.
Artificial Den Description
Every effort should be made to avoid destroying or damaging known dens during project activities, as per standardized recommendations by U.S. Fish and Wildlife Service (e.g., surveys, monitoring, and exclusion zones; U.S. Fish and Wildlife Service 1999). Den destruction may at times be unavoidable. Consultation must occur prior to disturbance or destruction of den sites. While careful excavation may reduce the potential for direct mortality, loss of den sites has long-term negative effects that reduce the quality and viability of urban environments for kit fox.
The construction of artificial dens is a recommended mitigation for the disturbance or destruction of earthen or manmade kit fox dens during project activities. Artificial dens are of two types: subterranean and escape. Subterranean dens consist of two entrance tunnels (3-m length of 20-cm diameter polyvinyl chloride or high-density polyethylene pipe) leading down at no more than a 30-degree angle to a subterranean chamber (0.5 m in diameter, 0.3 m tall). Entrance tunnels should be oriented such that water does not flood the chamber. It is also recommended that a longitudinal section of the tunnel floor be removed to increase drainage and provide better footing for foxes that are exiting the chamber. The floor of the chamber should be located approximately one meter below ground. The chamber may be either box- or dome-shaped, but must have an earthen floor that allows kit foxes to enlarge the den over time (Figure 17a-d).
Escape dens consist of 3- to 6-m lengths of 20-cm diameter pipe (polyvinyl chloride or high density polyethylene) placed on the surface of the ground and covered with 1-2 m of soil (Figure 18a-d).
Both subterranean and escape dens can be modified to exclude entrance by larger predators, particularly red foxes (Vulpes vulpes) and coyotes (Canis latrans). These predators could be excluded by narrowing the den entrances to a width of 10-15 cm. This can be accomplished in a variety of ways, such as driving stakes in front of the entrances, or installing prefabricated diameter-reduction couplings.
Artificial subterranean and escape dens are regularly used by kit foxes in urban environments for resting, predator avoidance, avoiding temperature extremes, moisture conservation, and rearing of young. From June 2001 to June 2004, 22 subterranean and 9 escape dens in urban Bakersfield, CA were monitored using tracking media, remotelytriggered cameras, and radio telemetry (Cypher et al., unpublished data). Kit foxes used 29 of the 31 dens during the study period. These dens were checked with tracking media 8548 times, and fox tracks were detected on 1198 occasions (14%). This rate of visitation was a minimum estimate because precipitation, irrigation, and visitation by other animals at times made detecting kit fox tracks difficult. In spring 2003, and again in spring 2004, two different family groups raised young in artificial subterranean dens (Figure 19a-b).
28 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox Artificial Den Installation Criteria
The following criteria should be met when selecting locations to construct artificial dens. 1) Artificial dens should be as close as possible to the destroyed or disturbed fox den. 2) The location should have a high likelihood of kit fox visitation. 3) Den entrances should be oriented to avoid flooding.
4) The den complex should have reduced likelihood of future disturbance, including development, regular maintenance, and human tampering.
Permanent cautionary devices that alert maintenance personnel to the presence of the artificial den may allow construction in regularly maintained areas. If a suitable site is unavailable along the road corridor it may be necessary to arrange for cooperative agreements with adjacent landowners to install artificial dens on their properties.
Suitable properties may include railway, canal, or utility corridors, drainage basins, golf courses, parks, and industrial sites. Throughout the site selection and construction process, the suitability for kit fox, the expected longevity, and the impacts on regular maintenance activities should be carefully evaluated.
KIT FOX ROAD CROSSING STRUCTURES
Summary
Vehicle strike is the leading cause of mortality for urbanized kit foxes. The likelihood of strike increases with increasing road width, speed limits, and traffic volume. Strikes often occur at the intersection of roads with linear rights-of-way. Linear rights-of-way include other roads (of all sizes), railroads, canals, utility corridors, golf course crossings, and riparian areas. Kit foxes appear to use linear corridors for movement, potentially accounting for the increase in strikes at these locations.
Major roads and associated features may restrict fox movements and consequently reduce gene flow, dispersal, colonization of habitat patches, and the resilience of fox populations to disturbance. This is especially likely in urban environments where road density, width, and traffic volume are increased and habitat is fragmented and susceptible to change.
Maintaining connectivity is identified as a primary recovery action for kit fox in section II.L.6.a. of the Recovery Plan for Upland Species of the San Joaquin Valley, California (U.S. Fish and Wildlife Service 1998).
The construction of fox-specific road crossing structures is a recommended conservation strategy for new high-volume roads, the widening of existing roads, or the rebuilding of existing structures that have the potential to facilitate kit fox road crossings. Potential crossing structures include underpasses, overpasses, and culverts. In the following text we describe crossing structures for urbanized kit foxes and provide criteria for site selection and instructions for building or modifying structures.
Road Crossing Structure Attributes
Little is known about the attributes that make crossing structures appealing to the San Joaquin kit fox. Clevenger (2005) conducted a comprehensive literature review on the 29 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox subject, but his conclusions suffered from a lack of data specific to kit fox. To fill this gap, Cypher et al. (Interagency Agreement No. 43A0068) have initiated a 2005-2006 study for California Department of Transportation to evaluate non-engineered crossing structures along 4-lane highways within the range of the San Joaquin kit fox and the ecologically similar desert kit fox of the Mojave eco-region. While these data will be useful when they become available, they will have limited applicability to kit fox crossing structures in urban environments.
Urban habitats are highly fragmented, and urban kit foxes develop habitual travel behaviors, often utilizing linear corridors for movement through the complex of human polygonal and linear development. In contrast, the Cypher et al. 2005-2006 study will examine crossing structures on roads that transect native habitat. There is no evidence that kit foxes in natural lands concentrate road crossings at specific features, such as drainage culverts, bridges, or road intersections when medians, fencing, or other impediments are absent.
In a recent study of the effects of two-lane highways on San Joaquin kit fox in natural lands (LoKern), Cypher et al (Interagency Agreement No. 06A0814, 55004872) found no evidence of fox avoidance of highways or of favored crossing locations. It should be noted, however, that traffic volumes on the highways in the LoKern study (approximately 8500 vehicles per day) were similar to volumes found on local roads in the city of Bakersfield (this study). Neither highways at LoKern nor local roads at Bakersfield significantly contributed to kit fox mortality. In other words, there may be little benefit to utilizing crossing structures or other habitual crossing locations when there is little risk of strike.
The following recommendations are based on knowledge of kit fox behavior, movements, territory use, and locations of mortality. We have combined these data with general recommendations on structure design and site selection for similar species.
Ideally, crossing structures in urban environments shall be institutionally linked with long-term monitoring programs and clear criteria for determining efficacy.
On the most basic level a crossing structure should satisfy two conditions. First, it should reduce mortality for the target species. Because vehicle strike is the primary cause of death for kit foxes in urban lands, and strikes occur disproportionately on major roads at identifiable geographic features (i.e., intersections with linear rights-of-way), we conclude that crossing structures have a high probability of reducing mortality.
Consequently crossing structures are an appropriate and necessary mitigation for urban road projects.
Second, crossing structures should increase habitat connectivity. This is a more difficult condition to evaluate. As noted, urban habitats are highly fragmented. To the extent that roads, and especially high-volume roads, contribute to fragmentation, we conclude that successful crossing structures will increase connectivity. As demonstrated (this study), kit foxes have seasonally influenced behaviors and susceptibility to vehicle strike.
During the month of December, male kit foxes increase scent marking frequency (an indicator of territory defense) and movements in search of mating opportunities. Not surprising, there is an increase in vehicle strike for male kit foxes during this period of instability in social dynamics. Furthermore, kit fox juveniles disperse during summer months, sometimes several miles from the maternal range, again encountering many 30 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox roads. Finally, urban kit foxes are displaced by new development and other human activities, resulting in range instability and dispersal to new territories. It is not known, however, whether the presence and types of roads in the urban environment influence the direction and length of movements and dispersal.
We take a hierarchical approach, from landscape to individual behavior, in describing requirements of fox-specific crossing structures. Criteria include: 1) road type; 2) kit fox presence and adjacent habitat suitability; 3) presence of natural crossing locations; 4) embankments, walls, or fencing that funnel individuals toward the crossing zone; and 5) passage design that meets kit fox behavioral requirements. We stress that these criteria are generated with expert opinion and data from ongoing observational studies of urban foxes. Hypothesis driven experiments will be necessary to evaluate the relative importance of these variables.
Criterion 1: Road type
We examined the distribution of fox-vehicle collisions on four types of urban roads - highway, arterial, collector, and local. Of these, kit foxes disproportionately died on arterial roads. Arterial roads typically were wider and had higher posted speed limits and traffic volumes than collector and local roads. Foxes also died on collector roads in Bakersfield from 1985-2004. In some cases, collector roads had similar traffic volumes and widths to arterial roads. Highways, which had the highest traffic volumes and speed limits, weren’t a marked source of fox mortality during this study. The absence of foxvehicle collision on highways can be explained by a barrier effect –animals that do not attempt to cross, will not be struck. Dispersal of individuals between habitat fragments, however, is an essential function of kit fox populations (U.S. Fish and Wildlife Service 1998) and a reduction in dispersal due to roads has been shown to strongly impact the demographics and extinction probability of small populations (Jaeger and Fahrig 2004).
Therefore it is likely that highways posed a significant road effect (if not direct mortality) on urbanized foxes. Lastly, there was little evidence for an association between local roads and fox-vehicle collision or altered kit fox movements.
Based on these findings, we recommend that crossing structures be considered on all highway, arterial, and collector roads. We do not recommend crossing structures as a protection or compensation measure for local roads.
Criterion 2: Kit fox presence and adjacent habitat suitability Presence of kit foxes may be evaluated by spotlighting, surveillance or track stations, surveying for scat, tracks, and dens, or interviewing citizenry. Presence/absence data, however, may be fallible to some degree. Kit foxes may be absent not because the site is unsuitable, but because of localized extirpation. In fact, fox populations throughout the species’ range undergo cycles of extirpation and recolonization, known as metapopulation dynamics (U.S. Fish and Wildlife Service 1998). Metapopulation dynamics influence kit fox demographics and extinction probability, and increase in strength with increasing fragmentation. Furthermore, it has been shown that with growing isolation of habitat fragments, it is less likely that fragments will be recolonized in the event of local extinction. Nowhere is kit fox habitat more fragmented and more 31 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox frequently altered than in urban environments. Therefore, it is likely that at any given time a subset of suitable habitat in urban environments will be unoccupied by kit fox.
A conservative alternative to presence/absence surveys is to concentrate crossing mitigation at locations that have suitable adjacent habitats. As a general rule urban kit foxes occupy industrial and commercial lands, parks, golf courses, and schools. Within these lands, occupancy appears linked to the extent of contiguous habitat, the quantity of undeveloped or lightly developed lots, the presence of drainage basins (favored den sites), and the presence of linear features that provide den building and movement opportunities such as canals, utility corridors, railroads, and riparian areas. Kit foxes do not typically occupy residential zones unless a golf course or other large open space is present (in which case occupancy is highly likely).
Criterion 3: Areas of increased road crossing
Clevenger (2005) reports that animal use of a crossing structure is linked to placement near natural crossing points. This assessment is supported by crossing studies (e.g., Foster and Humphrey 1995, Yanes 1995). Urban kit foxes more often are killed in vehicle strikes at the intersection of major roads with linear rights-of-way including other roads (of all types), canals, railroads, utility corridors, and riparian areas (this study). The concentration of mortalities at these intersections increases the likelihood of successful mitigation. First it narrows the selection of sites for crossing structures to easily identifiable landscape features. Second, it decreases the need to inhibit crossing at other locations. Third, intersections with linear rights-of-way often have pre-existing crossing structures. For example, a bridge over a canal or river may only require a design modification to be suitable for kit fox. When implemented early in the planning process these modifications may have little additional cost.
Because of the concentration of road crossings and vehicle mortalities at linear rights-ofway, we recommend that mitigation efforts prioritize these locations. For practical reasons, it will not be possible to install crossing structures at most road-road intersections. Instead, we recommend placing highest priority on installing or modifying structures at intersections of roads with highways, railroads, canals, rivers, or utility corridors and other locations where an underpass, overpass, or culvert is required.
Criterion 4: Embankments, walls, and fences
Another important predictor of use of crossing structures and decrease in vehicle strikes is the construction of manmade barriers that funnel animals toward the passageway (e.g., Haas 2000, Clevenger 2005, Mata et al. 2005). Barriers may include embankments, walls, and fences.
Embankments appear to discourage road crossing. Cypher et al. (in prep.) observed regular use by kit foxes of a railway underpass on a raised portion of highway 99 in Bakersfield (Figure 20a). The embankment was approximately eight meters tall and the underpass span was approximately 50 meters wide. Radio-tagged foxes were never known to climb the embankment to travel across the highway surface. Kit foxes constructed dens in the earthen slopes within the underpass and even whelped and reared young at the site for multiple seasons (Figure 20b). Embankments on raised highways 32 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox may fragment the landscape in the absence of underpasses or other crossing opportunities. Crossing structures should always be considered when building or modifying raised roadways.
Most urban roads are at grade with the surrounding environment. Cement walls may border highways, arterial, and collector roads, but this is typical only of residential areas, which may not be suitable for kit fox. Other roads are bordered by vegetation, low walls, and metal or wood fencing, all of which may be permeable to kit foxes. Small, skilled at digging, and agile, the kit fox is adept at passing through barriers designed for humans or other large mammals.
We recommend the installation of walls at potential crossing sites that encourage use of the passage and discourage crossing the road above grade. Studies on other species suggest that barriers are more effective when they are shaped as a funnel that directs animals toward the structure. It also is recommended that there be a method of exit for animals that get onto the roadway within the barrier zone. The complexity of urban environments makes meeting these recommendations difficult. Nevertheless, barriers are an integral part of successful crossing structures and should be implemented with all crossing projects.
We make the following specific recommendations. Barriers should be approximately 1.5 meters in height and of a solid material, such as cement block, that discourages climbing.
Walls should be impermeable to kit foxes that approach from adjacent habitat, but permeable to foxes that are on the roadway. One method to achieve one-way permeability is to install a dirt embankment next to the wall on the side nearest the road that allows a fox to run to the top of the wall from roadside (Figure 21a-b). The wall should remain 1.5 meters above grade on the side that borders habitat to prevent entrance to the roadway. Based on behavioral observations of radio-collared kit foxes and location of kit fox mortalities (this study), barriers should lead directly from the passage and run parallel to the road for a distance of at least 50 meters. In some cases, barriers will best be implemented as part of and in addition to existing natural or manmade features, including embankments, walls, and buildings. Finally, landscaping is recommended between the barrier and roadside (i.e., on the embankment). Urban kit foxes are known to use landscaping for cover while traveling along arterial roadways that are bordered by cement block walls (C. Bjurlin, pers. obs.).
Criterion 5: Behaviorally suitable passage design
We have identified four characteristics that affect behavioral suitability of crossing structures for kit foxes. First, a clear line of sight should be maintained through the passage for the entire breadth of the roadway, with the exit visible from the entrance.
Second, approach to the entrances should be level or gently sloped and free from vegetation or obstacles. Third, the passage should be minimally one meter square, with passage dimensions proportional to the roadway (i.e., as road width increases, passage width and height increases). Fourth, one escape den (see above) should be installed within the passage and one escape den installed on the approach to each entrance to give kit foxes protection from predators. In the following text, we profile existing structures to illustrate the aforementioned criteria. We provide recommended modifications where appropriate.
33 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox Profiled Crossing Structures
Seven Oaks Golf Course underpass
The Seven Oaks Golf Course in Bakersfield, CA was bisected by Buena Vista road, a four-lane, divided arterial road (Criterion 1). The road segment of interest (980 m) was bounded to the north by intersection with Ming Avenue and to the south by intersection with Chamber Blvd. Traffic volumes were estimated in 2002 at 13,750 vehicles per day (vpd). To maintain connectivity for golfers, an underpass structure was installed. This underpass met nearly all of the criteria for a successful crossing structure. The golf course was occupied by kit foxes and extended on both sides of the passage (Figure 22, Criterion 2). The greens narrowed where they approached the crossing site, creating a natural transverse point (Criterion 3). Two-meter high walls bordered the road (Criterion 4). The passage was greater than two meters square and had flanged and unobstructed entrances (Figure 22b-c, Criterion 5). One confirmed vehicle strike occurred at the site after construction of the barrier wall (Figure 22a). There were gates in the walls at a maintenance yard directly southeast of the passage and at a road access point to the southwest of the passage. A kit fox may have used one of these gates to gain access to the roadway.
Analysis - This design was suitable for locations with pedestrian or bicycle routes, utility corridors, golf courses, or other linear rights-of-way that are not associated with water transport. It would be improved by the installation of escape dens and the modification of the nearby gates to prevent kit foxes from entering the roadway.
Truxtun Extension horse culvert
Truxtun Extension was a 4-lane, divided collector road in Bakersfield, CA (Criterion 1).
Traffic volumes in 2002 were estimated at 35,000 vpd. The road segment of interest (5.3 km) occured between the intersection with Wible Road to the east and Coffee Road to the west. The segment was bordered to the north by the Kern River and to the south by a canal and mixed residential and commercial zones. Kit foxes occupied the surrounding lands. Radio-tagged animals repeatedly crossed the road and five confirmed vehicle strikes occurred along the road segment (this study). An underpass culvert was built 270 m east of the junction with Coffee Road. The passage location had suitable habitat to the north (Criterion 2). A pedestrian trail connected the passage to a canal on the southern side of the roadway (Figure 23a-b, Criterion 3). There was a chain link fence that may have impeded access to the road on the southern side, but it was broken by a pedestrian trail 15 m to the west of the southern entrance. The northern entrance had a 20-m chain link fence directly over the culvert (Figure 23c). The road was easily accessible from the north along the remainder of the segment. The culvert was approximately 2.5 meters in diameter with an earthen bottom that was seasonally flooded (Figure 23d, Criterion 5). On one occasion a kit fox was seen running north across the road directly over the crossing structure.
Analysis – This was a suitable passage at an appropriate location that required fencing and escape dens to become fully operational.
34 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox Coffee Road bicycle path underpass
Coffee Road was a six-lane, divided, arterial road in Bakersfield, CA (Criterion 1).
Traffic volumes in 2002 were estimated at 45,100 vpd. The road segment of interest (1600 m) was bounded to the north by intersection with Brimhall Road and to the south by intersection with Stockdale Highway. Surrounding lands were a mixture of commercial and undeveloped properties and were suitable for kit fox (Figure 24a, Criterion 2). Several canals and the Kern River corridor intersected the road. A bridge that spaned the Kern River also provided passage for a bicycle path on the southern embankment. The river corridor, proximity to road and canal intersections, and presence of a bicycle path made the passage a natural crossing point (Criterion 3). The west side of Coffee Road was bounded by chain link fence, but the east side had open access to the roadway (Figure 24b-c, Criterion 4). The passage was greater than 3m in height and width, and free from obstruction (Figure 24d, Criterion 5). Five confirmed vehicle strikes occurred on the road segment, including one that was 60 m south of the passage (Figure 24a & d).
Analysis – This was a suitable passage under a road with high traffic volume that required fencing and escape dens to become fully functional.
Highway 58 canal bridge
Highway 58 was a four-lane, divided roadway (Criterion 1). The road segment (2200 m) was bounded to the east by intersection with Landco Drive and to the west by intersection with Patton Way. Traffic volumes in 2004 were estimated at 47,000 vpd. Surrounding lands were a mixture of commercial, industrial, and undeveloped properties. A canal and arterial road (Fruitvale Ave) formed a six-way intersection with Highway 58. Kit foxes and their habitat were abundant along the road segment (Figure 25a, Criterion 2). The confluence of canal, arterial road, and highway made it a natural kit fox crossing location (Criterion 3). Chain link fence occured sporadically along the canal, but gaps in the fence and at gates allowed foxes to gain access to the roadway. The road was not walled or fenced. This underpass complex was composed of two separate bridges, one on Fruitvale Ave, the other on Highway 58. The Fruitvale Ave. bridge was impassable at the time photos were taken. The canal was transporting water and there was no embankment along its margin beneath the bridge (Figure 25b). In contrast, the Highway 58 bridge remained passable while transporting water. There were dirt embankments on both margins of the canal beneath the bridge, along with unobstructed entrance and exit locations (Figure 25c-d, Criterion 5). No fox-vehicle collisions were recorded at the location, but kit foxes frequently crossed the road during a telemetry study (Figure 25a).
A radio-tagged kit fox was repeatedly tracked to the canal and twice tracked to the canal underpass when there was no water present.
Analysis - The confluence of multiple linear rights-of-way along with presence of kit foxes and frequent road crossings made this an appropriate location for a crossing structure. The fencing at the site was insufficient for keeping foxes off the roadway.
When transporting water, one of the bridges did not accommodate fox movement beneath the roadway. This location would require extensive modification to be fully functional. 35 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox Figure 14. Earthen kit fox dens in urban Bakersfield, CA. a) Single entrance den under building foundation. b) Natal den complex on canal bank. c) Multi-entrance den in drainage basin bordering intersection of two arterial roads. d) Single entrance den in vacant lot. 36 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox Figure 15. Non-earthen den locations for kit foxes in Bakersfield, CA. a) Fox emerging from stacked pipe. b) Narrow entrances to a kit fox den under a storage container. c) Fox resting beside stacked lumber at a construction site. d) Fox returning to a den within a modular housing unit.
37 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox Figure 16. Camouflaged earthen kit fox dens in urban Bakersfield, CA. a) Entrance to den in landscaping at parking lot. b) Thatch covered den entrance in a golf course fairway. c) Dirt mound from den in shrub-island at park. 38 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox Figure 17. Artificial subterranean dens for San Joaquin kit fox at Bakersfield, CA. a) Artificial den schematic. b) PVC two-entrance chamber den under construction. c) High-density polyethylene two-entrance den. d) PVC tunnel with floor removed longitudinally. 39 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox Figure 18. Artificial escape dens for San Joaquin kit fox at Bakersfield, CA. a) Escape den schematic. b) High-density polyethylene escape den under construction. c) Completed den. d) Kit fox entering escape den. 40 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox Figure 19. Kit fox pups at artificial subterranean dens at a golf course (a) and drainage basin (b) in Bakersfield, CA. Figure 20. Railroad underpass on highway 99 in Bakersfield, CA. a) Habitat view. b) Kit fox natal den at the top of the underpass embankment.
41 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox Figure 21. Barrier wall to encourage use of road crossing structures for the San Joaquin kit fox in urban environments. The roadside embankment allows foxes that are trapped on the roadway to clear the barrier wall. a) Cross-section view. B. Three-dimensional rendering.
42 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox Figure 22. Buena Vista Road golf cart crossing structure, Bakersfield, CA. a) Aerial view of roadkill and radio-tagged kit fox locations at crossing structure. b) Habitat view from east entrance of crossing structure. c) Approach view to east entrance. d) Passage interior. 43 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox Figure 23. Truxtun Extension horse culvert, Bakersfield, CA. a) Aerial view of radio-tagged kit fox locations at horse culvert. b) View from pedestrian trail at south culvert entrance (canal in background). c) North culvert entrance. Yellow line depicts extent of fencing on north side of road. d) Culvert interior. 44 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox Figure 24. Coffee Road overpass at Kern River bicycle trail, Bakersfield, CA. a) Aerial view of kit fox roadkill and radio-tagged night locations at crossing structure. b) Habitat view from west entrance. c) East entrance to bicycle path on southern embankment of Kern River. d) View of roadway from East with location of kit fox roadkill in red. No fences prevent fox access to roadway on eastern side. 45 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox Figure 25. Highway 58/Fruitvale Avenue canal bridge, Bakersfield, CA. a) Aerial view of radio-tagged kit fox night locations at crossing structure. b) East entrance to Fruitvale Bridge obstructed by water. c) South entrance to highway 58 bridge. d) Dirtembankment under Highway 58 Bridge. 46 Appendix A. Supplemental Recommendations for Protection of San Joaquin Kit Fox
LITERATURE CITED
Clevenger, A.P. 2005. Design and performance of wildlife crossings for kit foxes and ecologically similar small carnivores: A literature review and semi-annotated bibliography. California Department of Transportation, San Luis Obispo, California.
Foster, M.L., and S.R. Humphrey. 1995. Use of highway underpasses by Florida panthers and other wildlife. Wildlife Society Bulletin 23, 95-100.
Haas, C.D. 2000. Distribution, relative abundance, and roadway underpass responses of carnivores throughout the Puente-Chino Hills. MSc thesis, California State Polytechnic University, Pomona.
Jaeger, J.A., and L. Fahrig. 2004. Effects of road fencing on population persistence. Conservation Biology 1651-1657.
Koopman, M. E., J. H. Scrivner, and T. T. Kato. 1998. Patterns of den use by San Joaquin kit foxes.
Journal of Wildlife Management 62:373-379.
Mata, C., I. Hervás, J. Herranz, F. Suárez, and J.E. Malo. 2005. Complementary use by vertebrates of crossing structures along a fenced Spanish motorway. Biological Conservation 124, 397-405.
U.S. Fish and Wildlife Service. 1998. Recovery plan for arid upland species of the San Joaquin Valley, California. U.S. Fish and Wildlife Service, Portland, Oregon.
U.S. Fish and Wildlife Service. 1999. Standardized recommendations for protection of the San Joaquin kit fox prior to or during ground disturbance. U.S. Fish and Wildlife Service, Sacramento, California.
Yanes, M., J.M. Velasco, and F. Suárez. 1995. Permeability of roads and railways to vertebrates: the importance of culverts. Biological Conservation 71:217-222. 47 View publication stats
SAN JOAQUIN KIT FOX HOME RANGE, HABITAT USE,
AND MOVEMENTS IN URBAN BAKERSFIELD
by
Nancy Frost
A Thesis
Presented to
The Faculty of Humboldt State University
In Partial Fulfillment
Of the Requirements for the Degree
Master of Science
In Natural Resources: Wildlife
December 2005
iii
ABSTRACT
San Joaquin kit fox home range, habitat use, and movements in urban Bakersfield Nancy Frost
Habitat destruction and fragmentation has led to the decline of the federally endangered and state threatened San Joaquin kit fox (Vulpes macrotis mutica). Kit foxes in the San Joaquin Valley occur in and adjacent to several urban areas. The urban kit fox population in Bakersfield has the potential to contribute to recovery efforts, however, little is known about habitat use in the urban environment. Habitat use in the urban landscape was examined in 28 radiocollared adult kit foxes between 1 May 1997 and 15 January 1998.
The area of the urban environment needed to meet kit foxes’ ecological requirements varied among the sexes and fluctuated throughout the year. Mean home range size was 1.72 km2 (100% minimum convex polygon estimate) and mean concentrated use area (core area; 50% fixed kernel estimate) size was 0.16 km2. Females had a greater median number of core areas than did males, but core area size did not differ between the sexes. Mean home range size was significantly larger during the dispersal season than during the pair formation and breeding seasons. Home range size was greater for males than females during the breeding season.
To assess the extent to which kit foxes were concentrated around limited resources, the percentage of overlap between adjacent kit foxes’ home ranges and core areas was determined.
Mean home range overlap was greater than 71% for family group members and less than 16% for unrelated individuals, which was less than that reported for the nearby rural population. Overlap of adjacent kit foxes’ core areas indicated that kit foxes were concentrated around key urban habitat patches. Core area overlap was greater for members of the same family group than core area overlap of neighboring males and females or neighboring males. iv
To determine which attributes of the urban environment were used by kit foxes and may support the population over time, habitats used disproportionately were compared to what was available in home ranges and the urban landscape. Kit foxes used open and sump (water catchment basins) habitats more than their availability in both the home range area and study area. There was more open and sump habitat in home ranges than in the study area. Kit fox core areas contained a disproportionately high amount of sumps that had food and den sites and restricted public access.
Sump and open habitats were more suitable for denning and consequently, were used more than their availability in the study area. Kit foxes primarily used subterranean dens but also used pipes and other man-made structures. Dens were located farther from roads than expected and in habitat patches that were larger than the median habitat patch in the study area.
To identify which urban habitats kit foxes used for resting, foraging, and traveling, kit fox movements and travel paths through adjacent habitat patches were examined. Kit foxes moved an average speed of 1.33 km/h. Minimum speed for females was greatest from approximately 0330 - 0730 h and for males was greatest from approximately 1830 - 2230 h. Kit foxes used sump and open habitats for resting. Kit foxes also foraged in these habitats, as well as in transition and commercial habitats. Habitats used for traveling included manicured open and open habitats, in which total distance traveled per movement session was longest. Overall median speed was greatest in residential habitat. Kit foxes were observed crossing roads and using culverts and bridges to move under roads.
Demographic characteristics and weights of the kit foxes that were captured were used to assess habitat quality. Two of the 28 radiocollared kit foxes died during 6,036 days of active radiotransmitters. Radiocollared kit foxes had 15 litters, comprised of 2.8 + 0.45 (range = 1 – 7) pups. Urban kit fox weight was similar to that for rural kit foxes. v
The availability of sump and open habitats appeared to shape the distribution and abundance of the urban population. Therefore, retaining sump and open habitats throughout Bakersfield may promote the continued existence of the urban kit fox population. vi
ACKNOWLEDGEMENTS
I would like to thank all those who contributed to the successful completion of this research project, especially my advisor, Dr. R. T. Golightly, for sharing with me both his advice and expertise. In addition, I thank my other committee members, Drs. T. L. George and D. W.
Kitchen for their support and constructive comments that greatly improved the quality of this thesis. My thanks go out to my professors and fellow students at Humboldt State University who contributed greatly to my educational growth. I would like to thank the San Joaquin chapter of The Wildlife Society for the research grant and the Eureka Rotary Club and the Stockton Sportsmen's Club for scholarships.
I would like to thank the California Department of Fish and Game, especially M. Potter and R. Reed, for assisting with this project by providing a vehicle and hiring three scientific aids, T. Chilton, J. Storlie, and R. Siebdrath, whose hard work, dedication, and willingness to learn contributed immensely to this project. I appreciate the volunteer efforts of M. Otten, G. Warrick, B. Vanherweg, B. Cypher, J. Hinshaw, and K. Brown. I thank the Department of Energy, Chevron USA, and Enterprise Advisory Services, Inc., especially J. Killen and B. Cypher, for the loan of telemetry equipment, radio collars, kit fox handling equipment, and traps. I would also like to thank P. Hoffman from the City of Bakersfield Water Resources Department and A. Abe from the City of Bakersfield Recreation and Parks Department for arranging access to city sumps and parks, respectively. Furthermore, I wish to thank J. Tobar, with the City of Bakersfield's Management Information Services Department, for the City of Bakerfield geographic information system coverages. I thank Dr. C. Hammans of the Coffee Road Animal Hospital and D. Kroger from the California Living Museum for their generous participation in the successful rehabilitation of an injured kit fox pup. I wish to acknowledge the Bakersfield SPCA for vii
"rescuing" one of my study animals that made its way to the third story of a parking garage and could not find the exit. My thanks go to A. Sullivan, J. Redmond, and M. Cantrell of the Sundale golf course, D. E. Keith Trucking, and K. S. Fabrication for allowing access to their property for implementation of the study. I wish to acknowledge Kelly Pipe Company for their cooperative efforts in helping me retrieve a kit fox pup that went for an unexpected "ride" in one of their pipes that was delivered from Bakersfield to Santa Fe Springs, California.
Special thanks go to my husband, S. Telthorst, for his tremendous support, encouragement, and participation in this research project. Finally, I dedicate this thesis to S.
Telthorst and my late mother, S. Castle, whose support and lifelong example of patience, perseverance, and persistence imparted me with the skills necessary to pursue and fulfill my dreams.
The United States Fish and Wildlife Service, California Department of Fish and Game, California Department of Transportation, and Humboldt State University Institutional Animal Care and Use Committee (protocol #96/97.W.62) issued the necessary permits and memorandum of understanding for this project.
viii
TABLE OF CONTENTS
Page
ABSTRACT .........................................................................................................................iii ACKNOWLEDGEMENTS....................................................................................................vi LIST OF TABLES .................................................................................................................x LIST OF FIGURES...............................................................................................................xi LIST OF APPENDICES.......................................................................................................xii INTRODUCTION..................................................................................................................1 STUDY AREA ......................................................................................................................5 METHODS............................................................................................................................9 Trapping ....................................................................................................................9 Locations...................................................................................................................9 Home Range ............................................................................................................12 Habitat Use ..............................................................................................................15 Movements ..............................................................................................................17 Demographics..........................................................................................................19 RESULTS............................................................................................................................21 Trapping ..................................................................................................................21 Locations.................................................................................................................21 Home Range ............................................................................................................21 Habitat Use ..............................................................................................................23 Movements ..............................................................................................................30 Demographics..........................................................................................................42 ix
TABLE OF CONTENTS (CONTINUED)
DISCUSSION......................................................................................................................43 Demographics..........................................................................................................43 Locations.................................................................................................................45 Home range..............................................................................................................46 Habitat use ...............................................................................................................50 Movements ..............................................................................................................53 MANAGEMENT RECOMMENDATIONS...........................................................................57 REFERENCES.....................................................................................................................59 x
LIST OF TABLES
Table Page
1 Habitat types and their descriptions used to typify the urban setting and kit fox habitat use in Bakersfield, California from May 1997 to January 1998. ....................... 7 2 Home range (100% minimum convex polygon) and core area (50% fixed kernel) size for radiocollared kit foxes in Bakersfield, California from May 1997 to January 1998. .........................................................................................................24 3 Seasonal home range (100% minimum convex polygon) size for radiocollared kit foxes in Bakersfield, California from May 1997 to January 1998. ..............................25 4 Ranked radiocollared kit fox habitat use based on habitat availability at the study area and home range area scale, in Bakersfield, California between May 1997 to January 1998. Habitat types used similarly (p > 0.05) are grouped by column............28 5 Mean difference between the mean proportion of habitat available in the study area and kit fox home ranges (e.g., there was 16.7% less open habitat in the study area than within home ranges), and kit fox home ranges and core areas in Bakersfield, California between May 1997 to January 1998.......................................29 6 Influence of sex, movement session time, and their interaction on minimum, maximum, and mean speed and total adjusted distance moved for 10 radiocollared kit foxes in Bakersfield, California from May 1997 to January 1998. .....................................................................................................................36 7 Movement session time, type of movement, and habitat associations for radiocollared kit foxes in Bakersfield, California from September 1997 to January 1998. .........................................................................................................39 8 Rural kit fox and swift fox cause-specific mortality rates reported within their geographic range for comparison to that for urban kit foxes in Bakersfield, California from May 1997 to January 1998...............................................................44 9 Kit fox home range size reported within various habitats within their geographic range for comparison to home range size of urban kit foxes in Bakersfield, California from May 1997 to January 1998...............................................................47 xi
LIST OF FIGURES
Figure Page
1 The study area in Bakersfield, Kern County, California for investigations of kit fox habitat use from May 1997 to January 1998......................................................... 6 2 Behavior exhibited by directly observed kit foxes at independent daily locations (n = 2,087) in Bakersfield, California from May 1997 to January 1998.......................22 3 Percentage of home range overlap and core area overlap for pairs of radiocollared kit foxes in Bakersfield, California from May 1997 to January 1998. Vertical bars represent + 1 SE. .............................................................................................26 4 Mean percentage of each habitat type in the study area, which bounded the available habitat, and radiocollared kit fox home ranges (n = 27) and core areas (n = 58) in Bakersfield, California from May 1997 to January 1998. Different letters above the bars indicate a significant difference in habitat use versus availability. ............................................................................................................27 5 Mean number of passing vehicles, passing pedestrians, and people in the same habitat patch as radiocollared kit foxes at all daily locations (n = 4,824) in Bakersfield, California from May 1997 to January 1998. Vertical bars represent + 1 SE....................................................................................................................31 6 Number of dens used by radiocollared kit foxes in each habitat type in Bakersfield, California from May 1997 to January 1998............................................32 7 Percentage of available habitat in the study area compared to percentage of habitat used by radiocollared kit foxes for denning in Bakersfield, California from May 1997 to January 1998. .............................................................................33 8 Minimum speed per movement session for male and female radiocollared kit foxes in Bakersfield, California from September 1997 to January 1998. .....................35 9 Mean distance radiocollared kit foxes traveled in each habitat type in Bakersfield, California from September 1997 to January 1998. Vertical bars represent + 1 SE.......37 10 Mean speed radiocollared kit foxes traveled in each habitat type in Bakersfield, California from September 1997 to January 1998. Vertical bars represent + 1 SE.......38 xii
LIST OF APPENDICES
Appendix Page
A Sites of live-captured kit foxes, domestic cats, and opossums between May 1997 and January 1998 in Bakersfield, California..............................................................69 B Kit fox location data and estimates for home range size, core area size, and time to independence for 28 radiocollared kit foxes that were monitored between May 1997 and January 1998 in Bakersfield, California. ....................................................70 C Weight, hind foot, and ear measurements for captured adult, subadult, and pup kit foxes in Bakersfield, California between May 1997 and January 1998...................73 D Area-observation curves using the 100% minimum convex polygon home range for 27 kit foxes in Bakersfield, California from May 1997 to January 1998.................74 E The percentage of all radiocollared kit fox daily locations (n = 4,824) and passing vehicles documented in linear habitats during each hour in Bakersfield, California from September 1997 to January 1998......................................................75 1 INTRODUCTION
The kit fox (Vulpes macrotis) is the smallest North American member of the family Canidae, with an average weight of 2.1 kg for adult females and 2.3 kg for adult males in California (Morrell 1972). Kit foxes range throughout the western United States in shortgrass prairies and other arid areas (Whitaker 1998). The San Joaquin kit fox (Vulpes macrotis mutica; hereafter kit fox) was described by C. H. Merriam in 1902 (McGrew 1979) and is the largest California subspecies in skeletal measurements, body size, and weight (Grinnell et al. 1937). Kit foxes inhabit arid habitats with flat to sloping terrain (Morrell 1971).
The kit fox historically ranged in the San Joaquin Valley of California, north of Tracy, west to San Joaquin County, east to La Grange, Stanislaus County, and south to Kern County (Grinnell et al. 1937, Morrell 1975). In the early 1900’s, the kit fox population started to decline (United States Fish and Wildlife Service 1983), and by 1930, its range had been reduced by more than half, with the largest portion remaining in the southern and western parts of the San Joaquin Valley (Grinnell et al. 1937). In 1969, the kit fox was known to range from Los Banos, Merced County, east to White River, Tulare County, south to Kern County, and west to San Luis Obispo County (Morrell 1975). Currently, the largest remaining populations of kit foxes occur in western Kern County and in the Carrizo Plain Natural Area, San Luis Obispo County (United States Fish and Wildlife Service 1998).
In 1967, the San Joaquin kit fox was listed as a federally endangered subspecies (United States Department of the Interior 1967), and in 1971, it was designated a State threatened species (United States Fish and Wildlife Service 1998). The destruction and fragmentation of its native habitat has been a limiting factor that has led to the decline of the kit fox population (Knapp 1978, Spiegel 1996, United States Fish and Wildlife Service 1998). This habitat fragmentation 2 has been due mainly to agriculture, urban development, and oil production (Morrell 1975, Spiegel 1996, United States Fish and Wildlife Service 1998). In 1993, the San Joaquin Valley Biological Technical Committee estimated that only about 1 - 5% of the original habitat of the kit fox remained.
Kit foxes in the San Joaquin Valley occur in and adjacent to several urban areas including the cities of Taft (Zoellick et al. 2002), Tulare, Visalia, and Porterville (United States Fish and Wildlife Service 1998), and Bakersfield, where kit foxes have been observed throughout the city (Morrell 1975, Murphy 1992, Cypher and Warrick 1993, Bjurlin and Cypher 2003). Kit foxes are known to use the Kern River Parkway in Bakersfield (Murphy 1992, Beedy et al. 1992) for denning, foraging, and traveling, despite the fact that it is bounded on the north and south by urban and industrial development and receives intensive public recreation use (Beedy et al. 1992).
Additionally, urban kit foxes have been found to den close to human activities and structures (Murphy 1992), including water sumps (catchment basins) in and adjacent to urban development in Bakersfield (Stafford and Murphy 1992).
Urban habitats may be marginal for kit foxes, because the urban environment has a high level of disturbance and consists of a patchy mosaic of habitats (Morrell 1975). While urban developments negatively impact kit fox habitat, kit foxes may still survive in or near them if there are adequate den sites and prey base (United States Fish and Wildlife Service 1998). Positive attributes of urban habitats may include a constant source of water from sumps, canals, and lawn sprinklers (Murphy 1992) that could lead to a more stable prey population. While fewer natural predators, such as coyotes (Canis latrans) and bobcats (Lynx rufus), are found in the urban environment, domestic dogs (Canis familiaris) occur in greater abundance. Food may be available on a more consistent basis due to the presence of refuse, which constitutes part of the kit fox diet in Bakersfield (Murphy 1992, Cypher and Warrick 1993). Such use of human-derived foods suggests that kit foxes may be able to adapt to the urban setting. 3 Smaller canid species, such as coyotes and foxes, often do well in human-altered environments because they scavenge and forage individually on a variety of small food items and are able to utilize new food sources (Kleiman and Brady 1978). If kit foxes are adaptable enough to persist in urban environments, as are coyotes (Quinn 1995, Romsos 1998, Grinder and Krausman 2001) and red foxes (Vulpes vulpes; Harris 1977, Kolb 1984, 1986, Harris and Rayner 1986, Doncaster et al. 1990, Lewis et al. 1993, Sallee 1998, Kamler and Ballard 2002), the urban kit fox population could contribute to recovery efforts (Cypher and Warrick 1993). Urban kit fox populations could protect against extirpations in rural areas, and serve as a source of animals for reintroduction efforts (Cypher and Frost 1999). Favorable habitat features in urban areas also could serve as linkages or corridors between natural lands, which may minimize local extinction and genetic isolation of fox populations in fragmented habitats (United States Fish and Wildlife Service 1998, Wandeler et al. 2003).
It is important to understand how kit foxes use landscapes in all areas where they exist, including urban settings. Unfortunately, little is known about the urban kit fox population.
Morrell (1975) noted that a study should be conducted to gain a better understanding of kit fox ecology in areas other than natural habitat. As part of the recovery strategy in the San Joaquin Valley Multispecies Recovery Plan (United States Fish and Wildlife Service 1998), it was recommended that better demographic information be collected for kit foxes living in residential and industrial areas. The San Joaquin Valley Biological Technical Committee (1993) expressed concern that urbanization threatens the remaining kit fox habitat and listed several kit fox research needs including further studies of mortality rates and causes, diet, distribution, home range requirements, and movements. Due to the continual loss of natural habitat, more information on urban kit fox space use, movements, survival, and reproduction may contribute to their recovery (Cypher and Warrick 1993).
4 Canid home range size is influenced primarily by food abundance, and also food distribution and availability of adequate denning sites (Kleiman and Brady 1978). In order to understand the ecological factors that facilitate habitat use, it is important to identify the areas of concentrated use (hereafter core areas) within the home range (Samuel et al. 1985). Optimal habitat conditions for a species may be identified by evaluating if and how core areas are used disproportionately (Ables 1969). Core areas likely have dependable food sources and rest sites (Samuel et al. 1985) such as dens, the availability of which limits the presence of kit foxes (Golightly 1981, Spiegel et al. 1996). If kit foxes are concentrated around limited resources, the home ranges and core areas of adjacent kit foxes may have substantial overlap (Golightly 1981).
If sufficient food and den sites are available, mortality is minimal, and reproduction occurs at reasonable rates, then urban habitat should support viable kit fox populations. The goal of my project was to determine which attributes of the urban environment were successfully used by kit foxes and may support the population over time. To identify the attributes of the urban environment that kit foxes used most, areas and habitats used disproportionately were compared to what was available in the urban landscape. The quantity and type of urban habitat needed to meet the ecological requirements of urban kit foxes (i.e., that used for denning, foraging, and traveling) was identified. To understand habitat use, kit fox home range size, core area size, spatial distribution of kit foxes in the urban landscape, habitat and den use, and movements were evaluated in relation to habitat type, time of night, and human activity. Assessment of habitat quality should be based on the survival, reproduction, and density of the species occupying the habitat (Van Horne 1983). Therefore, I also reported the demographic characteristics of captured urban kit foxes.
5 STUDY AREA
The study was conducted within the city limits of Bakersfield (Figure 1), at the southern end of the San Joaquin Valley, California. The average elevation of Bakersfield was 124 m (United States Geological Survey 1981) and in 1997, had a human population of 221,700 (State of California, Department of Finance 2002).
Bakersfield has an arid climate with an average annual precipitation of 14.5 cm (National Oceanic and Atmospheric Administration 1997) that occurs mainly between October and April.
Total precipitation during the study was 10.9 cm, 3.0 cm higher than normal (Meadows Field Weather Station; National Oceanic and Atmospheric Administration 1997, National Oceanic and Atmospheric Administration 1998). Summers are hot and dry, while winters are cool and moist.
During the study, average temperatures ranged from 7.9° C in December to 27.2° C in July and annual mean temperature was 19.6° C, which was -14.3° C lower than normal (Meadows Field Weather Station; National Oceanic and Atmospheric Administration 1997, National Oceanic and Atmospheric Administration 1998).
Vegetation in the study area varied by land use and was composed mostly of introduced and exotic species. Manicured open, commercial, and residential habitats were planted mainly with non-native grasses and shrubs (Table 1). Conversely, open, industrial, and some linear habitats, such as the Kern River Parkway, had a mix of introduced and endemic grasses, forbs, and shrubs. Sumps were primarily barren on the sides, often contained standing water, and had scattered native and non-native vegetation near the upper edges. In addition, sumps were distributed throughout the city, fenced, and closed to the public. Sumps had sloping sides and ranged from 0.01 to 0.03 km2 in area.
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C alifo rn ia
Kern C ounty
S t o c k d a l e H i g h w a y
In te rsta te 5 Fre ew a y
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9 9
G o sf o rd Ro a d
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S T U D Y A R E A
B a k e rsfi e ld
Ke rn Riv er
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Figure 1. The study area in Bakersfield, Kern County, California for investigations of kit fox habitat use from May 1997 to January 1998. 6 7
Table 1. Habitat types and their descriptions used to typify the urban setting and kit fox habitat use in Bakersfield, California from May 1997 to January 1998.
Habitat type Description
Commercial Office buildings, hotels, medical facilities, and their associated parking areas.
Transition Areas in which residential, commercial, or industrial construction is in progress or has recently been completed.
Industrial Areas of industrial use not generally open to the public, such as manufacturing plants and shipping yards.
Linear Kern River Parkway, canals, roads, railroads, and highway and power line right-of-ways.
Manicured Open Parks, schools, and golf courses.
Open Vacant lots and fallow agricultural fields.
Residential Apartments and single-family housing developments.
Sumps Water catchment basins used to contain urban run-off and rainwater. 8 Kit fox predators, including bobcat, coyote, and domestic dog (Cypher et al. 2000), were observed at the study site. Bobcats and coyotes were only observed in the Kern River Parkway (personal observation). California ground squirrel (Spermophilus beecheyi), Botta's pocket gopher (Thomomys bottae), and desert cottontail (Sylvilagus audubonii) (all urban kit fox prey; Cypher and Warrick 1993), were observed at the study site. Domestic cats (Felis catus) and opossums (Didelphis virginiana), which utilize some of the same food resources as urban kit foxes and red foxes, were observed in the study area (Catling 1988, Golightly et al. 1994, Read and Bowen 2001) (Appendix A).
9 METHODS
Trapping
Between 3 May and 18 July 1997, wire-mesh live-traps (38 x 38 x 107 cm; Model 208, Tomahawk Live Trap Company, Tomahawk, WI) were set in sumps, parks, the Kern River Parkway, and privately-owned land in Bakersfield. Traps were covered with canvas tarps to protect captured animals from sun and inclement weather, and baited with canned mackerel.
Trapping frequency and trap placement was opportunistic. The trapping was limited to areas in southwest Bakersfield where kit foxes or their sign (i.e., tracks, scat, and dens) were observed.
Captured kit foxes were transferred from traps to heavy cloth bags for handling. Each animal was sexed, eartagged, weighed (+ 3%), measured (+ 1 mm; right ear and hind foot length), and released at the capture location. Uniquely-numbered metal eartags (Model 1005-4, National Band and Tag Company, Newport, KY) were affixed to the right ear for females and left ear for males. Kit foxes were aged based tooth eruption and wear (Harris 1978). Individuals with partially erupted teeth were classified as juvenile, and those with permanent teeth were classified as adults. Young of the year were classified as puppies until 14 July, and subadults from 15 July to 30 November, after which they were considered to be adults.
Locations
I attached 50-g collar-mounted radiotransmitters (Model 80, Telonics, Mesa, AZ) to captured adults. Radiocollars were equipped with mortality sensors that pulsed approximately twice the normal rate if there was no movement for four hours. Between 14 December 1997 and 15 January 1998, all but four study animals were captured and had their radiocollars removed. 10 Radiocollared kit foxes were located using portable receivers (Model TR-4, Telonics, Mesa, AZ), an omni-directional antenna affixed to a car, and a hand-held 2-element yagi antenna.
Kit foxes were located between 1630 and 0900 h because they were primarily active at night (Egoscue 1956, Golightly 1981, White et al. 2000). At the onset of the study in May 1997, nine study animals were randomly monitored to verify that they were not active during daylight hours.
With the exception of delineating the study area, only locations obtained between one hour before sunset and one hour after sunrise were used in analyses. Each kit fox was systematically located approximately once per night (hereafter referred to as daily locations) but rotated in the schedule each night. Although sampling effort for each study animal was equal at study end, every kit fox could not be found during each sampling period. When a kit fox could not be found, the area where it was previously located was searched for at least 30 min and then, if not located, it was searched for elsewhere in the study area concurrent with searches for other kit foxes.
The transmitted signal was followed until the kit fox was observed (sometimes with the aid of a flashlight) or tracked to a den, or the habitat patch from which the signal was emitted was encircled (White and Garrott 1990). This technique ensured that the location of and habitat used by each kit fox was classified without error (Samuel and Kenow 1992). I tried to stay at least 100 m from the study animals, so as to not alter their behavior (i.e., cause them to move from one habitat patch to another). To assess if this technique created a sampling bias by altering their behavior, each animal was classified as resting/walking, trotting, or running at the time of observation. When this technique was not feasible (e.g., the habitat patch was not accessible), kit fox locations were determined with triangulation, based on three bearings taken as close as possible (< 300 m) from the loudest signal source (Springer 1979). Immediately after a kit fox was located, the observer plotted the location on a 1996 City of Bakersfield street map (scale 1:29,000, Compass Maps, Inc., Modesto, CA) and recorded the number of people that were visible (i.e., not in buildings or large habitat patches) in the same habitat patch as the kit fox. 11 Mapped kit fox locations were digitized into a geographic information system (GIS; ArcView 3.2 with Spatial Analyst 2.0, ESRI, Redlands, CA), and displayed over the City of Bakersfield's 1997 GIS file titled “Land Status Land Condition Land-use,” as a background for guidance during digitizing. This GIS file was developed through the input of bearing and distance measurements (taken by land surveyors) to define parcel boundaries (i.e., the coordinate geometry method; Amos, R. 2005. Personal communication. City of Bakersfield, GIS Department, 1501 Truxtun Avenue, Bakersfield, CA 93301). Using methods in Romsos (1998), I characterized the urban landscape and described urban kit fox habitat use by collapsing similar urban landscapes into eight categories (Table 1).
To verify the accuracy of the habitat types and boundaries depicted in the GIS, maps generated from the GIS were compared to the actual location of habitat patches throughout the study area. When habitat was not correctly represented in the GIS, a global positioning system (GPS Pathfinder Pro XR, Trimble, Sunnyvale, CA) was used to obtain the geographic coordinates of the edges of each habitat patch. These coordinate data were differentially corrected using the GPS Pathfinder Office program to improve accuracy to within + 1 m, imported into the GIS, and used to digitize polygons representing the correct habitat patches.
The accuracy of the habitat types and boundaries depicted in the GIS was further verified by comparison to aerial photographs (Farm Services Agency, USDA, Bakersfield, CA) of the study area that were photographed in June 1997, at the beginning of the study, and in June 1998, after the study concluded. This comparison was done primarily to identify habitats that were classified as open in 1997 but were in transition or residential in 1998. In these instances, the date each house was built was determined by consulting Kern County public records data. Any habitat patch that was open in the June 1997 aerial photograph, on which a house was built prior to the end of the study, was classified as transition habitat. 12 Home Range
Home range estimates were obtained using the GIS to generate the 100% minimum convex polygon, which defined the bounds of the area used (Mohr 1947, Hooge and Eichenlaub 1997). Use of kernel-based estimators may be important to identify disjunct areas of activity in urban landscapes where habitat may be fragmented (Grinder and Krausman 2001). For comparison to other urban canid studies (Romsos 1998, Grinder and Krausman 2001), home range was also estimated using the 95% fixed kernel, a probabilistic model that identified the most probable area of utilization (Worton 1989, Seaman and Powell 1996). To represent the core area for each study animal, I used the 50% fixed kernel, which identified the areas that encompassed 50% of the animal’s locations (Calhoun and Casby 1958, Jennrich and Turner 1969, Anderson 1982). Large bodies of water (e.g., Lake Truxtun) were removed from the estimates of home range area and available habitat (White and Garrott 1990).
Probabilistic home range techniques (e.g., fixed kernel) are sensitive to serial autocorrelation (Anderson 1982, Hooge et al. 1999). The minimum convex polygon home range estimator assumes that location data are not time correlated (Anderson 1982, White and Garrott 1990), but are robust to violation of this assumption. Only statistically independent data (i.e., the data point provided no indication of the category for the next data point) were used to estimate home range and core area size. Time to statistical independence between successive locations was based on the time it took each kit fox to cross its home range (White and Garrott 1990, Lucherini et al. 1995, Harrison 1997). To derive this estimate, I divided the mean speed for each of 10 kit foxes that were located approximately every 15 - 30 min during two to six 3 - 5 h movement sessions (hereafter referred to as sequential locations), by the longest axis of their 100% minimum convex polygon home range (Jenness 2003).
Area-observation curves were used to determine the minimum number of kit fox locations necessary for home range estimation (Odum and Kuenzler 1955). To do so, I iteratively 13 estimated the 100% minimum convex polygon home range for each kit fox, beginning with the first 10 locations and adding one consecutive location at a time. The area of each 100% minimum convex polygon was plotted against the number of locations from which it was estimated. The point on the curve at which each 10 additional locations did not increase the home range estimate by 10% was the minimum number of locations needed to estimate home range.
Because home range size may vary with sex (Burt 1943), a 2-sample t-test was used to determine if home range size differed between males and females (Hintze 1999). For comparison to rural kit fox studies in Arizona (Golightly 1981) and California (Zoellick et al. 1987, White and Ralls 1993, Koopman 1995), the 100% minimum convex polygon home range estimate was used for this analysis. All data were checked for normality and equal variance, and data that could not be normalized by transformation were analyzed with non-parametric tests. Significance level (α) was 0.05.
Home range size may also vary by season (Burt 1943). To assess if the area of the urban environment needed to meet kit foxes’ ecological requirements fluctuated throughout the year, I determined if home range size varied with biological season for urban kit foxes, as it did for rural kit foxes (Zoellick et al. 1987). Because kernel-based estimates from small sample sizes (e.g., from subsetting the data by season) tend to overestimate home range sizes (Seaman and Powell 1996), seasonal home ranges were estimated using 100% minimum convex polygons, which is more robust than other techniques when sample size is small (Harris et al. 1990). Data were normalized with a square-root transformation and analyzed with a 2-way analysis of variance (Winer et al. 1991, Hintze 1999) to compare mean home range size for male and female kit foxes during three biological seasons: dispersal (1 June to 30 September); pair formation (1 October to 30 November); and breeding (1 December to 15 February; Zoellick et al. 1987, Reese et al. 1992, Koopman et al. 1998). A Fisher's least significant difference multiple comparison test (Hintze 1999) was used to determine what factors (i.e., season and sex) in the analysis of variance were 14 significantly different. Study animals were located too seldom to estimate home range during the pup rearing season (16 February to 31 May).
The presence of food-rich habitat patches within territories may allow additional group members. Macdonald (1983) predicted that the home range of a mated pair of red foxes may overlap and support other foxes if there were sufficient resources. However, if food is evenlydispersed among habitat patches, a larger home range would be required and the tolerance of additional adults in the territory of a pair would be predicted to be less. I predicted that if kit foxes were concentrated around limited resources, home ranges and core areas of adjacent kit foxes would have a high percentage of overlap. The GIS was used to identify the percentage of overlap between a) adjacent 100% minimum convex polygon home ranges and b) adjacent core area polygons between kit fox pairs comprised of a) mated pairs or family groups, b) adjacent females, c) adjacent males, and d) adjacent but unpaired males and females.
It was assumed that habitats that were used disproportionately more than available contained key resources. To assess if habitats with key resources (i.e., denning and foraging sites) were equally-dispersed or conversely, concentrated, the mean percentage of area of each 100% minimum convex polygon that the core area represented was determined. If areas of habitat use were concentrated, then the 50% fixed kernel should encompass less than 50% of the area used by each kit fox. If areas of use were uniform rather than concentrated, the 50% fixed kernel would comprise half of the area within the 100% minimum convex polygon. To assess if use of key resources differed among the sexes, the median number of core areas for females and males was compared with a Mann-Whitney U-test, and the mean core area size for males and females was compared with a 2-sample t-test.
15 Habitat Use
For those kit fox locations determined from triangulation, the likelihood for habitat misclassification increased with animal proximity to habitat edge and decreased as habitat-patch size increased (Samuel and Kenow 1992). To assess the probability of habitat misclassification, the GIS was used to determine the distance between each triangulated location and the nearest habitat-patch edge (Jenness 2004a). I reasoned that triangulated kit fox locations less than 100 m from the nearest habitat-patch edge may have had misclassification of habitat type. The 100 m value was selected because urban coyote studies that used similar methods to study habitat use, had average telemetry errors of 46 m (Grinder and Krausman 2001) and 102 m (Romsos 1998).
Use of habitat is considered selective if it is exploited disproportional to its availability (Johnson 1980). Habitat selection can occur at a variety of scales (Wiens 1973, Orians and Wittenberger 1991, Litvaitis et al. 1996, Apps et al. 2001). I analyzed habitat use within the individual kit fox home range and core area and for the kit fox population in the study area. To determine if kit foxes used urban habitat types (Table 1) with a frequency proportional to their availability, the independent locations that fell within a) the study area and b) each home range were selected. To delineate the study area, a 100% minimum convex polygon was generated using all daily, sequential, and trapping locations for all study animals (Litvaitis et al. 1996, Romsos 1998, Kamler et al. 2003). For comparison to other urban canid habitat use studies (Romsos 1998, Grinder and Krausman 2001), the 95% fixed kernel was used to represent the home range of each kit fox. The area of each habitat type in the study area and each home range was summed, and use of habitat types in each was compared with a Friedman's test (Alldredge and Ratti 1986, Hintze 1999; individual kit fox was the blocking factor, habitat type was the treatment factor, and the ranked numerical difference between the proportion of habitat used and the proportion of habitat available was the response variable). To determine which habitat types 16 were used significantly more than their availability, a Fisher's least significant difference procedure (Alldredge and Ratti 1986, Hintze 1999) was used.
How kit foxes used urban habitats was determined at two scales: within each home range in proportion to what was available in the study area; and within each core area in proportion to what was available in the corresponding home range. For each habitat type, I compared the proportion a) within each home range and the study area and b) within each core area and corresponding home range. Prior to analysis, the proportion data were arcsine transformed (Winer et al. 1991) and analyzed with a matched-pair t-test, or a Wilcoxon signed-rank test if data could not be normalized (Hintze 1999).
Fox habitat use may also be influenced by human presence (Lucherini et al. 1995); therefore, I treated human activity as an attribute of habitat. After each kit fox was located, an index of human activity was gained by counting the number of vehicles and pedestrians that passed by an imaginary line that was perpendicular to the nearest road in a 15 second period. The number of people that were visible (i.e., not in buildings or large habitat patches) in the same habitat patch as the kit fox was also recorded. To determine if human activity (i.e., the number of passing vehicles, passing pedestrians, and people in the same habitat patch as the kit fox) varied among the habitat types, a Kruskal-Wallis 1-way analysis of variance was used, followed by a Kruskal-Wallis multiple comparison test to determine what factors in the analysis of variance were significantly different.
Relative to some rural landscapes that have uniformly-distributed resources (Koopman 1995, Kamler et al. 2004), urban landscapes are highly fragmented, have isolated, clumped resources (Grinder and Krausman 2001), and consist of a patchy mosaic of habitats (Morrell 1975). Some urban habitats may be more suitable for denning and consequently, are used more than their availability in the study area. If certain habitats were selected for denning, the spatial 17 arrangement of home ranges would be influenced by the availability of the selected habitat types (Golightly 1981, Hardenbrook 1987).
The geographic coordinates of each den (i.e., refugia receiving repeated use by the study animals) were determined using a GPS and imported into the GIS. Dens were categorized as subterranean, culvert (or pipe), or man-made structure. To understand if den sites influenced habitat use, a 1-proportion z-test (Winer et al. 1991, Hintze 1999) was used to determine if habitats were used for denning in proportion to their availability in the study area.
Using the GIS, I generated random points (with a uniform distribution) equivalent to the number of dens in the study area (Hooge and Eichenlaub 1997). To assess if road proximity influenced den locations, the GIS was used to determine the distance of each den and random point to the centerline of the nearest road (Jenness 2004a). A Mann-Whitney U-test was used to determine if den sites and random points differed with regard to distance to the nearest road. A Wilcoxon signed-rank test was used to determine if the median size of habitat patches within which dens were located differed from the median habitat-patch size in the study area.
Movements
Canid movement behavior may indicate use of habitat for resting, foraging, and traveling (Ozoga and Harger 1966, Laundré and Keller 1981, Romsos 1998). Between 8 September 1997 and 7 January 1998, a randomly-selected subsample (five females and five males) of radiocollared kit foxes was examined for movements and travel paths through adjacent habitat patches in order to identify which behaviors were associated with each habitat type. Based on behavior-specific movement types for canids in Ozoga and Harger (1966) and Laundré and Keller (1981), I categorized kit fox movement as resting/walking (i.e., inactivity at low speeds between 0 - 0.8 km/h), trotting (i.e., potentially searching for food at intermediate speeds between 0.8 - 1.8 km/h), and running (i.e., traveling from one point to another at high speeds greater than 1.8 18 km/h). Movements were assessed during three nocturnal sampling periods, approximately 1830 - 2230 h, 2230 - 0330 h, and 0330 - 0730 h. Each kit fox was followed two to six times during each of the three sampling periods.
While following kit foxes, sequential locations were determined approximately every 15 - 30 min during the sampling period. Movement sessions with more than one hour between any two successive locations were deemed incomplete and repeated on another day. The locations identified during each movement session were plotted on a 1996 City of Bakersfield street map (scale 1:29,000, Compass Maps, Inc., Modesto, CA). Time, habitat type, kit fox activity (e.g., resting/walking, trotting, running), and number of passing vehicles, passing pedestrians, and people in the same habitat patch as the kit fox were recorded.
GIS was used to digitize kit fox locations and generate a line from the set of sequential location points for each movement session. Each line was then intersected with the habitat types through which it passed (Jenness 2004b). Kit fox speed (the distance between two sequential locations divided by the time elapsed) was regressed against the number of passing vehicles, passing pedestrians, and people in the same habitat patch to examine the influence of humans on kit fox habitat use. A multivariate analysis of variance was used to determine if sex and movement session time influenced minimum travel speed, maximum speed, mean speed (using all speed estimates except when the kit fox was at a den or resting), and total distance moved per movement session (Woodruff and Keller 1982). Because movement session length varied, total distance moved was standardized by multiplying the distance measure by the ratio of 1) the length of time elapsed during the shortest movement session to 2) the length of time elapsed during the movement session with which the distance measure was associated.
To determine if total distance moved per movement session varied by habitat type, I used a Kruskal-Wallis 1-way analysis of variance (Zoellick et al. 1989). A Kruskal-Wallis 1-way analysis of variance was used to determine if overall median speed was influenced by habitat 19 type. Kruskal-Wallis multiple comparison tests were used to determine what factors in these analysis of variance tests were significantly different.
A loglinear model was used to examine correlations between type of movement, frequency of relocations per habitat type, and time of movement session. To identify the habitat type and movement session (i.e., evening, middle of the night, and early morning) within which kit foxes rested/walked, trotted, and ran, standardized residuals were used to identify the greatest deviations from expected for kit fox movements.
Demographics
Reproduction and mortality in radiocollared kit foxes were measured to determine if demographic parameters of urban kit fox populations were similar to those for rural kit fox populations, and assess habitat quality in the urban landscape (Van Horne 1983). Kit foxes with a radiocollar in a mortality mode were immediately located and necropsied to assess cause of death.
This information was used to determine sources and rates of kit fox mortality, which were compared to data for rural kit fox populations. I determined the number of radio-days since each kit fox was radiocollared and the survival rate for that time interval, described by Heisey and Fuller (1985) as the interval survival rate. Paired tooth puncture wounds associated with subcutaneous hematomas on the carcass were indicative of a predator kill, and if the carcass exhibited massive trauma and was located near a road, the cause of death was determined to be vehicular impact (Spiegel and Disney 1996).
The number of pups incidentally trapped or observed with radiocollared adult kit foxes and their mates were identified. Additionally, as part of a concurrent study (Storlie 1998) of juvenile kit fox dispersal and mortality, trapping effort was conducted in areas where pups were captured or observed. Capture data from both studies were used to estimate litter size for kit 20 foxes in the study area. The annual reproductive success rate was based on the percentage of radiocollared females that produced pups.
21 RESULTS
Trapping
Between 1 May 1997 and 15 January 1998, 107 (30 adult males, 31 adult females, and 46 juveniles) kit foxes were captured in all habitat types in which traps were placed (Appendix A).
Mean adult kit fox weight was 2.47 + 0.05 (x¯ + 1 SE) kg for males and 2.16 + 0.03 kg for females.
Locations
Radiocollars were attached to 28 adults (13 males, 15 females). Each radiocollared kit fox was located 5.1 + 0.3 days each week. Of the 35 kit foxes located between 0900 and 1600 h, 34 were stationary (e.g., resting) or in a den. In 252 study days, a total of 1,882 sequential locations (during 111 movement sessions) and 4,824 daily locations were determined for the 28 study animals. Of these locations, 4,249 were independent, of which 2,898 (68%) were considered to be exact and the habitat types in which they occurred were correctly classified, based on being tracked to a den (n = 811) or directly observed (n = 2,087). Directly observed kit foxes were classified as stationary for 52% of the observations (Figure 2). Of the 1,351 triangulated locations, 66 were > 100 m from the nearest habitat-patch edge. The remaining locations were on average 31.3 + 0.6 m from the nearest habitat-patch edge.
Home Range
Based on the area-observation curves (Odum and Kuenzler 1955; Appendix D), the average number of locations needed to estimate a 100% minimum convex polygon home range was 27 + 1.7. All sequentially-located kit foxes could cross the longest axis of their 100% 22 0
10 20
30 40
50 60
Resting/Walking Trotting Running Other
Behavior Type
Observations (%)
Figure 2. Behavior exhibited by directly observed kit foxes at independent daily locations (n = 2,087) in Bakersfield, California from May 1997 to January 1998. 23 minimum convex polygon home range in less than four hours (range = 1.23 - 3.89 h; Appendix B). Therefore, four hours was used as the time to independence between kit fox locations.
The 100% minimum convex polygon home range size for all study animals combined was 1.72 + 0.19 km2 and was larger for males than females (Table 2). Average 95% fixed kernel home range size for all study animals combined (excluding one outlier) was 1.2 + 0.19 km2 (range = 0.04 – 2.78). Excluding one outlier, core areas comprised 9.1 + 1.2% (range = 1.9 –
19.6) of the 100% minimum convex polygon home range. Kit foxes had an average of 2.15 +
0.23 distinct core areas, and females had more than males. Mean 100% minimum convex polygon home range size was significantly larger during the dispersal season than during the pair formation and breeding seasons (F = 7.79, df = 2, p < 0.001) and for males than females during the breeding season (F = 4.47, df = 1, p = 0.04), and there was no interaction between season and sex (F = 2.38, df = 2, p = 0.1) (Table 3). The percentage of home range and core area overlap between kit foxes was highest for family group members (Figure 3).
Habitat Use
The study area was 76 km2, and had 3,908 habitat patches that averaged 0.01 + 0.001 km2 (range was < 0.01 - 2.03, except for a 17.88 km2 patch that comprised all interconnecting linear features that was excluded from this calculation). Kit foxes used urban habitats disproportionate to their availability in the study area (Q = 103.5, df = 7, p < 0.001) and within home ranges (Q =
91.36, df = 7, p < 0.001; Figure 4). Open and sump habitats were used more than their availability in both the study area and in home ranges (Table 4). There was less area of residential habitat but more area of open and sump habitats in home ranges than in the study area.
Area of transition, commercial, manicured open, linear, and residential habitats were less, but area of sump habitat was greater, in core areas than in home ranges (Table 5).
Table 2. Home range (100% minimum convex polygon) and core area (50% fixed kernel) size for radiocollared kit foxes in Bakersfield, California from May 1997 to January 1998.
All Males Females Males vs. Females
Measurement x¯ SE Range x¯ SE Range x¯ SE Range Statistic df p Home range size (km2) 1.72 0.19 0.31 - 4.49 2.12 0.31 0.31 - 4.49 1.36 0.21 0.36 - 2.71 t = -2.08 25 0.02 Core area size (km2) 0.16a 0.03 0.01 - 0.5 0.18 0.05 0.01 - 0.5 0.15 0.04 0.02 - 0.43 t = -0.57 24 0.57 Core areas per kit fox 2.15 0.23 1 – 6 1.85 0.37 1 - 6 2.43 0.27 1 - 4 z = -1.98 25 0.02 a Excluding one outlier (the male with two distinct home ranges). 24 25
Table 3. Seasonal home range (100% minimum convex polygon) size for radiocollared kit foxes in Bakersfield, California from May 1997 to January 1998.
Home range (km2)
All Males Females
Season x¯ SE x¯ SE x¯ SE
Dispersal 1.24 0.11 1.32 0.16 1.17 0.15
Pair formation 0.77 0.11 0.79 0.16 0.74 0.16
Breeding 0.66 0.12 0.95 0.16 0.38 0.16
26 0
20 40
60 80
Family Group Male-Female Male-Male Female-Female
Pair Type
Overlap (%)
Home Range
Core Area
Figure 3. Percentage of home range overlap and core area overlap for pairs of radiocollared kit foxes in Bakersfield, California from May 1997 to January 1998. Vertical bars represent + 1 SE.
0 5
10 15
20 25
30 35
40 Residential Linear Commercial Open Manicured
Open
Industrial Sump Transition
Habitat Type
Area (%)
Study Area
Home Range
Core Area
a
c
b
b
a
a
b
a
b
c
a b
a
b
a
b
Figure 4. Mean percentage of each habitat type in the study area, which bounded the available habitat, and radiocollared kit fox home ranges (n = 27) and core areas (n = 58) in Bakersfield, California from May 1997 to January 1998. Different letters above the bars indicate a significant difference in habitat use versus availability.
27 Table 4. Ranked radiocollared kit fox habitat use based on habitat availability at the study area and home range area scale, in Bakersfield, California between May 1997 to January 1998. Habitat types used similarly (p > 0.05) are grouped by column.
Study Area Home Range
Habitat Types
Statistically Similar in Use
Mean
Rank
Habitat Types
Statistically Similar in Use
Mean
Rank
Rank
of
Use
Open 2.1 Sump 2.3 Most
Sump 2.6 Open 2.5
Transition 4.0 Transition 3.5
Industrial 4.0 Industrial 3.9
Manicured Open 4.4 Manicured Open 5.3
Commercial 5.4 Commercial Commercial 5.8
Linear 5.6 Linear Linear 6.2
Residential 7.8 Residential 6.6 Least28
29 Table 5. Mean difference between the mean proportion of habitat available in the study area and kit fox home ranges (e.g., there was 16.7% less open habitat in the study area than within home ranges), and kit fox home ranges and core areas in Bakersfield, California between May 1997 to January 1998.
Study Area and Home Range Home Range and Core Area
Habitat Type Percent
Difference Statistic p
a Percent
Difference Statistic p
b
Commercial -1.3 t = 0.89 0.38 2.8 t = -2.79 <0.01
Industrial -1.2 z = 1.43 0.15 -2.2 z = 0.05 0.47
Linear 2.5 t = 1.47 0.15 4.3 z = -2.25 0.01
Manicured Open -6.2 t = -0.59 0.56 3.7 z = -1.77 0.02
Open -16.7 t = -3.83 <0.01 -7.5 t = 1.46 0.16
Residential 25.8 z = 4.52 <0.01 6.4 t = -5.5 <0.01
Sump -1.9 z = -2.88 <0.01 -7.6 z = 2.19 0.01
Transition -1.0 t = -0.66 0.51 0.2 t = -2.30 0.01
a,b Because the analysis used multiple t-tests, the probability of at least one false rejection of the null hypothesis was 1 – 0.958 = 0.34 (Winer et al. 1991). 30 Number of people in the same habitat patch as the kit fox varied between habitat types and was greatest in manicured open habitat (H = 285.7, df = 7, p < 0.001; Figure 5). Industrial and linear habitats had a higher incidence of passing vehicles than all other habitats (H = 355.1, df = 7, p < 0.001; Figure 5). A greater number of pedestrians were observed along roads near sumps than all other habitats (H = 136.8, df = 7, p < 0.001; Figure 5).
The study animals used 190 dens, comprised of 159 subterranean dens, 17 culvert or pipe dens, and 14 man-made structure dens (e.g., metal storage containers, modular office buildings, junkyard debris, a shed, and a garbage dumpster), most of which were located in open, sump, and linear habitats (Figure 6). Sump (z = 45.74, df = 1, p < 0.001) and open (z = 11.47, df = 1, p <
0.001) habitats were used for denning more than their availability in the study area (Figure 7).
Residential (z = -10.5, df = 1, p < 0.001) and commercial (z = -3.67, df = 1, p < 0.001) habitats were used for denning less than their availability in the study area. Linear (z = -1.24, df = 1, p =
0.19), manicured open (z = -0.53, df = 1, p = 0.59), industrial (z = -0.3, df = 1, p = 0.76), and transition (z = -0.45, df = 1, p = 1.0) habitats were used for denning in proportion to their availability in the study area.
Dens were located farther from roads (0.10 + 0.01 km, range = 0.01 - 0.5) than randomlygenerated points (0.06 + 0.01 km, range = 0.0001 - 0.55; z = 8.17, df = 378, p < 0.001). The median size of habitat patches within which dens were located (0.03 km2) was significantly larger than the median habitat-patch size in the study area (0.004 km2; z = 10.56, df = 1, p <
0.001).
Movements
Movement sessions (n = 100) lasted from 184 to 315 min long. Kit foxes moved at an average rate of 1.33 + 0.02 km/h. Minimum speed during each movement session was influenced Vehicles Passing on Nearest Road
0 0.5
1 1.5
2 2.5
1 2 3 4 5 6 7 8 Vehicles/15 s
Pedestrians Passing Along Nearest Road
0 0.1
0.2 0.3
0.4 1 2 3 4 5 6 7 8 Pedestrians/15 s
People in Habitat Patch
0 0.2
0.4 0.6
0.8 Linear Industrial Residential Sump Commercial Open Manicured Open
Transition
Habitat Type
People/15 s
Figure 5. Mean number of passing vehicles, passing pedestrians, and people in the same habitat patch as radiocollared kit foxes at all daily locations (n = 4,824) in Bakersfield, California from May 1997 to January 1998. Vertical bars represent + 1 SE. 31 0
10 20
30 40
50 60
70 Open Sump Linear Manicured
Open
Industrial Commercial Residential Transition
Habitat Type Number of Dens
Man-made Structures
Culvert/Pipe
Subterranean
Figure 6. Number of dens used by radiocollared kit foxes in each habitat type in Bakersfield, California from May 1997 to January 1998. 32 0 5
10 15
20 25
30 35
40 Residential Linear Commercial Open Manicured
Open
Industrial Sump Transition
Habitat Type
Habitat (%)
Study Area Available
Used for Denning
Figure 7. Percentage of available habitat in the study area compared to percentage of habitat used by radiocollared kit foxes for denning in Bakersfield, California from May 1997 to January 1998.
33 34
by the interaction of sex and time of night (Figure 8, Table 6). The regressions of kit fox speed and the number of passing vehicles (r2 = 0.0077), passing pedestrians (r2 = 0.0016), and people in the same habitat patch as the kit fox (r2 = 0.0002), respectively, indicated that these variables (all of which could not be normalized through transformation) were not related to kit fox speed. The distance traveled during each movement session was longer in manicured open and open habitats than all other habitats (H = 125, df = 7, p < 0.001; Figure 9). Overall speed was faster in residential habitat than all other habitats (H = 111.6, df = 7, p < 0.001; Figure 10).
There was a significant interaction between kit fox movements, movement session time, and habitat type (c
2 = 61.48, df = 28, p < 0.001). Kit fox resting/walking movements deviated most from expected from 1830 – 2230 h, during which linear habitat was used more than expected and from 2230 – 0330 h, during which residential habitat was used less than expected (Table 7). Kit fox trotting movements deviated most from expected from 2230 – 0330 h during which open habitat was used more than expected, and from 2230 – 0730 h during which sump habitat was used less than expected. The greatest deviations from expected kit fox running movements were from 2230 – 0330 h during which open habitat was used more than expected, and from 0330 – 0730 h during which industrial habitat was used less than expected.
Between 27 September and 4 October 1997, a male kit fox moved > 5.9 km from his previouslyestablished home range to another part of the study area, where he remained until the end of the study. Kit foxes were observed crossing roads (up to four lanes), but also used culverts to move under roads. One study animal was observed to use a 0.46-m in diameter culvert to cross under a State Route 99 offramp and a 4.26 m wide by 3.66 m high vehicle access road to cross under State Route 99. Other kit foxes were observed to cross under the State Route 99 bridge over the Kern River and use a foot bridge to cross a canal.
35 0
0.05 0.1
0.15 0.2
0.25 0.3
0.35 0.4
1830 - 2230 2230 - 0330 0330 - 0730
Time Period
Minimum Speed of Travel (km/hr)
Males
Females
Figure 8. Minimum speed per movement session for male and female radiocollared kit foxes in Bakersfield, California from September 1997 to January 1998.
Table 6. Influence of sex, movement session time, and their interaction on minimum, maximum, and mean speed and total adjusted distance moved for 10 radiocollared kit foxes in Bakersfield, California from May 1997 to January 1998.
Males Females Males vs. Females
Movement Session
Time Interaction
Measurement x¯ SE Range x¯ SE Range F-Ratio df p F-Ratio df p F-Ratio df p Minimum
Speed (km/hr2) 0.26 0.03 0.02 - 0.75 0.27 0.03 <0.01 - 1.16 0.05 1 0.82 0.58 2 0.56 3.17 2 0.047 Maximum
Speed (km/hr2) 2.19 0.13 0.26 - 4.65 2.17 0.22 0.32 - 9.06 0.1 1 0.75 2.5 2 0.09 0.21 2 0.81 Mean Speed
(km/hr2) 1.39 0.03 0.02 - 4.65 1.25 0.03 <0.01 - 9.06 1.32 1 0.25 1.08 2 0.34 0.15 2 0.86 Total Adjusted
Distance
Moved (km) 1.76 0.11 0.12 - 3.34 1.62 0.15 0.13 - 4.77 0.88 2 0.35 1.81 2 0.17 1.16 2 0.32 36 0
0.2 0.4
0.6 0.8
1 1.2
Manicured
Open
Open Residential Linear Industrial Commercial Transition Sump Habitat Type
Mean Distance Traveled (km)
Figure 9. Mean distance radiocollared kit foxes traveled in each habitat type in Bakersfield, California from September 1997 to January 1998.
Vertical bars represent + 1 SE.
37 0
0.2 0.4
0.6 0.8
1 1.2
1.4 1.6
1.8 2
Residential Manicured
Open
Commercial Sump Industrial Open Linear Transition
Habitat Type
Mean Speed (km/hr)
Figure 10. Mean speed radiocollared kit foxes traveled in each habitat type in Bakersfield, California from September 1997 to January 1998.
Vertical bars represent + 1 SE.
38 Table 7. Movement session time, type of movement, and habitat associations for radiocollared kit foxes in Bakersfield, California from September 1997 to January 1998.
Movement Type Movement Session Time (h) Habitat Type Observed Frequencya Standardized Residualb Resting/Walking 1830 - 2230 Sump 11 -5.19
Transition 18 -4.16
Residential 19 -4.02
Commercial 30 -2.40
Industrial 58 1.71
Manicured Open 107 8.91
Open 185 20.37
Linear 205 23.30
2230 - 0330 Residential 6 -5.93
Transition 12 -5.05
Sump 13 -4.90
Commercial 28 -2.69
Manicured Open 76 4.36
Industrial 78 4.65
Linear 89 6.27
Open 194 21.69
0330 - 0730 Commercial 15 -4.60
Residential 15 -4.60
Transition 26 -2.99
Sump 35 -1.67
Industrial 38 -1.23
Manicured Open 57 1.56
Open 164 17.28
Linear 174 18.75
39 Table 7. Movement session time, type of movement, and habitat associations for radiocollared kit foxes in Bakersfield, California from September 1997 to January 1998 (continued).
Movement Type Movement Session Time (h) Habitat Type Observed Frequencya Standardized Residualb Trotting 1830 - 2230 Sump 12 -5.05
Transition 12 -5.05
Residential 25 -3.14
Industrial 29 -2.55
Commercial 33 -1.96
Manicured Open 45 -0.20
Open 96 7.29
Linear 105 8.62
2230 - 0330 Sump 6 -5.93
Transition 13 -4.90
Residential 14 -4.75
Industrial 25 -3.14
Manicured Open 30 -2.40
Commercial 41 -0.79
Linear 94 7.00
Open 115 10.08
0330 - 0730 Sump 6 -5.93
Transition 20 -3.87
Industrial 25 -3.14
Commercial 28 -2.69
Manicured Open 29 -2.55
Residential 46 -0.05
Linear 72 3.77
Open 97 7.44
40 Table 7. Movement session time, type of movement, and habitat associations for radiocollared kit foxes in Bakersfield, California from September 1997 to January 1998 (continued).
Movement Type Movement Session Time (h) Habitat Type Observed Frequencya Standardized Residualb Running 1830 - 2230 Sump 6 -5.93
Industrial 14 -4.75
Transition 16 -4.46
Commercial 19 -4.02
Linear 50 0.54
Manicured Open 54 1.12
Residential 61 2.15
Open 64 2.59
2230 - 0330 Transition 6 -5.93
Sump 7 -5.78
Industrial 25 -3.14
Residential 27 -2.84
Commercial 35 -1.67
Manicured Open 38 -1.23
Linear 53 0.98
Open 66 2.89
0330 - 0730 Industrial 2 -6.51
Sump 4 -6.22
Transition 6 -5.93
Commercial 8 -5.63
Linear 21 -3.72
Manicured Open 24 -3.28
Open 30 -2.40
Residential 30 -2.40
a Number of times a kit fox movement path intersected each habitat type, separated by movement type and movement session time. b Negative values indicate that a habitat was used less than expected and positive values indicate that a habitat was used more than expected.
If the value is > + 2.00 (2 standard deviations), it is significant. 41 42
Demographics
During 6,036 days of active radiotransmitters, two of the 28 radiocollared kit foxes died and the interval survival rate was 0.92. One female was hit by a vehicle and another female was likely killed by a coyote or domestic dog, based on 30 to 35-mm paired puncture wounds on the torso of the intact, unburied carcass (Spiegel and Disney 1996). It was unknown if another female that could not be located after 3 September 1997, died, dispersed, or had a malfunctioning radiocollar.
Pups were detected with 15 family groups, comprised of 22 radiocollared adult kit foxes.
Eleven of the 15 radiocollared females reproduced during one breeding season. Four of these 11 females had radiocollared mates. An additional four radiocollared males had uncollared mates that also reproduced in the same breeding season. Kit fox litters averaged 2.8 + 0.45 (range = 1 – 7) pups. The litter of 7 pups was observed denning with two radiocollared females, of which one exhibited reproductive condition and one did not.
43 DISCUSSION
Demographics
The urban kit foxes had lower mortality and similar reproduction and body weight compared to rural populations (Morrell 1972). Conversely, Cypher and Frost (1999) found that kit foxes in Bakersfield (i.e., females in winter and juveniles) were heavier than their counterparts in a nearby rural population. Urban kit foxes’ normal weights may be attributed to good nutrition. The constant source of water from sumps, canals, and lawn sprinklers in Bakersfield (Murphy 1992) may provide a more stable prey population. Like urban red foxes in Orange County, California (Lewis et al. 1993) and Toronto, Canada (Rosatte et al. 1991), urban kit foxes were supplementally fed (i.e., anthropogenic sources of food, including bread and burritos) by people and observed opportunistically foraging on both anthropogenic and natural food items (personal observation).
Urban kit foxes in Bakersfield may have lower mortality rates than rural foxes (Table 8).
Of 22 adult kit foxes from a nearby rural population that were radiocollared prior to or during late November and December 1995 through September 1996, 15 (68.2%) died and two were lost (Enterprise Advisory Services, Inc. 1997). Of 35 adult kit fox mortalities (including the two from this study) in the Bakersfield area from 1997 to 2003, 23% were due to vehicular impact (Bjurlin and Cypher 2003). The interval survival rate for urban kit foxes (0.92) was much greater than that for rural kit foxes (0.58; Ralls and White 1995; 0.44; Cypher et al. 2000).
Coyote predation may be more likely if a fox is far from its den (Kitchen et al. 1999) or in the peripheral areas of its home range (Sovada et al. 1998, Olson and Lindzey 2002). The majority of swift fox (Vulpes velox) deaths were due to coyotes and occurred outside the 85% Table 8. Rural kit fox and swift fox cause-specific mortality rates reported within their geographic range for comparison to that for urban kit foxes in Bakersfield, California from May 1997 to January 1998.
Cause-Specific Mortality Rate (%)
Reference Species Location Predation Vehicular Impact
Cypher et al. 2000 Kit Fox Kern County, CA 48.5 5.0
Ralls and White 1995 Kit Fox Carrizo Plain, CA 78.0 4.0 Hardenbrook 1987 Kit Fox Churchill County, NV 60.0 10.0 Spiegel and Disney 1996 Kit Fox Kern County, CA 66.7 1.7 Standley et al. 1992 Kit Fox Monterey and San Luis Obispo Counties, CA 75.0 6.3 Kamler et al. 2003 Swift Fox Dallam County, TX 33.0 42.0 Matlack et al. 2000 Swift Fox Sherman and Wallace Counties, KS 45.0 36.0 44 45
(Kitchen et al. 1999) or 95% (Sovada et al. 1998, Olson and Lindzey 2002) isopleth of the fox’s home range and more than 1 km from the den that the fox most recently occupied. Likewise, the urban kit fox that died as a result of coyote or dog predation was located outside the 85% isopleth of her range.
Production of young exceeded the number of kit foxes that died, which may have indicated that the urban kit fox population was demographically healthy during the period of study and habitat was of sufficient quality to support a source population (Van Horne 1983, Pulliam 1988, Noss et al. 1997). Seventy-three percent of radiocollared females produced pups, more than that observed for rural kit foxes in southwestern Kern County (64%; Spiegel and Tom 1996; 61%; Cypher et al. 2000). The mean number of pups per litter was within the range of that for rural populations: 2 (White and Ralls 1993) to 4 (Morrell 1971, Cypher et al. 2000).
Kit fox reproduction has been positively correlated with prey availability (White and Ralls 1993). Raccoons and skunks in Toronto, Canada weighed more and had higher reproductive success than their rural counterparts, which Rosatte et al. (1991) attributed to abundant and varied natural and human-derived food sources in the urban setting. The results of a supplemental feeding study indicated that kit fox survival and reproductive success were influenced by food availability (EG&G Energy Measurements 1993). Supplemental feeding by humans and the availability of refuse may contribute to the demographic health of urban kit foxes.
Locations
During daylight hours, urban kit foxes were found to be resting or in dens on all but one occasion. Like rural kit foxes in California (Morrell 1971, Morrell 1972, White et al. 2000), Utah (Egoscue 1956, O’Neal et al. 1987, Arjo et al. 2003), and Arizona (Golightly 1981, Golightly and Ohmart 1983) and urban red foxes in Orange County, California (Sallee 1998), urban kit foxes 46 were almost entirely nocturnal. Similarly, urban coyotes in Orange County, California (Romsos 1998), Seattle, Washington (Quinn 1995), and Tucson, Arizona (Grinder and Krausman 2001) were less active during daylight than at night. Urban kit foxes were primarily nocturnal and limited their daytime activity to the immediate vicinity of the den, similar to rural kit foxes (Morrell 1971, Morrell 1972), rural swift foxes (Kilgore 1969, Kitchen et al. 1999, Kamler et al. 2004), and urban red foxes (Voight and Macdonald 1984). Urban canids may benefit from being active only at night when interactions with humans are less likely.
Home range
Knowledge of home range size and spatial distribution can be used to manage urban habitat for the benefit of kit foxes. Home range estimates were much smaller than those for rural kit foxes (Table 9), but consistent with observations that foxes (Voight and Macdonald 1984, Murphy 1992) and raccoons and skunks in urban areas have smaller ranges than their rural counterparts (Rosatte et al. 1991).
Macdonald (1983) and Doncaster et al. (1990) attributed the tendency for red fox home ranges to be smaller in cities (e.g., Oxford) than in rural areas, to the spatial and temporal patchiness of food dispersion. Red foxes in Orange County, California had smaller home ranges where they were supplementally fed (Sallee 1998). Ables (1969) noted that the smaller home ranges for red foxes in south-central Wisconsin may have been due to habitat richness (i.e., a high interspersion of habitat types and abundant wild fruits and berries). Artificial food sources associated with urban and oilfield development may have led to decreases in the home range size of kit foxes in southwestern Kern County (Zoellick et al. 1987, Spiegel and Bradbury 1992).
Conversely, kit fox home ranges increased in size during times of low prey availability (White and Ralls 1993) and were negatively correlated with prey density (Morrell 1971, White and Garrott 1997). Thus, the small size of urban kit fox home ranges indicated that abundant food Table 9. Kit fox home range size reported within various habitats within their geographic range for comparison to home range size of urban kit foxes in Bakersfield, California from May 1997 to January 1998.
Reference Location Habitat Estimator Range Type Area km2 Knapp 1978 Kern County, CA Agriculture 100% Minimum convex polygona Home Range 2.52 Koopman 1995 Kern County, CA Saltbush scrub 100% Minimum convex polygon Home Range 3.52 Zoellick et al. 1987 Kern County, CA Saltbush scrub 100% Minimum convex polygon Home Range 4.63 White and Ralls 1993 Carrizo Plain, CA Grassland 100% Minimum convex polygon Home Range 11.60 O’Neal et al. 1987 Great Basin, UT Saltbush scrub 100% Minimum convex polygon Home Range 3.11 Spiegel and Bradbury 1992 Kern County, CA Saltbush scrub 97% Minimum convex polygonb Home Range 6.13 Spiegel and Bradbury 1992 Kern County, CA Saltbush scrub 95% Minimum convex polygonb Nocturnal Range 5.82 Hardenbrook 1987 Churchill County, NV Greasewood Modified Minimum Area Method Home Range 9.74 Arjo et al. 2003 Tooele County, UT Salt playa 95% Adaptive Kernel Home Range 43.09 Arjo et al. 2003 Tooele County, UT Greasewood 95% Adaptive Kernel Home Range 13.29 Arjo et al. 2003 Tooele County, UT Sagebrush 95% Adaptive Kernel Home Range 11.51 Koopman 1995 Kern County, CA Saltbush scrub 75% Harmonic Mean Core area 0.73 Spiegel and Bradbury 1992 Kern County, CA Saltbush scrub 50% Hamonic Meanb Core area 1.18 Zoellick et al. (2002) Kern County, CA Saltbush scrub 50% Hamonic Mean Core area 1.2 a May have been underestimated due to small sample size. b Estimates using non-independent data may have been inflated, as demonstrated in Koopman (1995). 47 48
resources were concentrated in key urban habitats around which home ranges were configured.
Further evidence of this was that urban kit foxes’ core area size constituted only 9% of the home range size, whereas that for rural kit foxes constituted 17% of the home range (Spiegel and Bradbury 1992). This may be because suitable denning habitat for urban kit foxes was concentrated around sumps and undeveloped lots.
Female urban kit foxes had a greater median number of core areas than did males, indicating that females had a higher number of distinct denning sites. Female kit foxes in Arizona (Golightly 1981) and Nevada (Hardenbrook 1987) spent more time near their dens than males. Fenced sumps in core areas provide denning habitat that may ensure safe reproduction in the urban population.
The home ranges and core areas of adjacent kit foxes may have substantial overlap if kit foxes are concentrated around limited resources (Golightly 1981), such as food-rich habitat patches (Macdonald 1983). Mean home range overlap was greater than 71% for family group members and less than 16% for unrelated individuals, which was less than that for the nearby rural population (Zoellick et al. 2002, Spiegel and Bradbury 1992).
Core area overlap was greater for members of the same family group (61%) than core area overlap of neighboring males and females (29%) or neighboring males (11%), similar to that for rural kit foxes (Spiegel and Bradbury 1992). Unpaired male and female urban kit foxes had a higher percentage of core area overlap than home range overlap. Because core areas were centered around denning sites, male and female kit foxes’ home ranges may have overlapped in a central denning area, as was the case for kit foxes in Arizona (Golightly 1981) and Nevada (Hardenbrook 1987). Kitchen et al.’s (2005) findings that male swift foxes spent more time on the boundary of the home range, while females spent more time in the group core area, may explain why female urban kit foxes had the least home range overlap and no core area overlap. 49 Overlap of home ranges and core areas indicated that kit foxes were concentrated around key urban habitat patches and food resources were not evenly-distributed. It was likely that urban kit foxes were able to find foraging and denning habitat in close proximity because of uniformlydistributed sumps, which may be important to the success of the urban kit fox population.
Due to refuse and human-derived foods, urban kit foxes may be able to meet their resource needs in a smaller area than rural kit foxes. The presence of these food resources distributed among disjunct habitat patches may explain why urban kit foxes had smaller and less overlapping home ranges than their rural counterparts. Given the constant and widespread availability of human-derived food in the urban landscape, suitable denning habitat may be a limiting factor for the urban kit fox population. This is consistent with Golightly’s (1981) conclusion that kit fox den sites in rural Arizona were limited by soils suitable for denning.
Estimates of 100% minimum convex polygon home range size were greater for males than females, perhaps due to fewer seasonal movements by females and increased foraging requirements for males during pup-rearing (Spiegel and Bradbury 1992). While Golightly (1981) found that male kit foxes in Arizona had much larger home ranges than females, home range size for other rural kit fox (Zoellick et al. 1987, Spiegel and Bradbury 1992, White and Ralls 1993, Koopman 1995), swift fox (Kitchen et al. 1999, Kamler et al. 2003), and Blanford’s fox (Vulpes cana; Geffen and Macdonald 1992) populations did not differ among the sexes.
Because home range size may vary with season (Burt 1943), the quantity of urban habitat needed to meet kit foxes’ ecological requirements may fluctuate over time. Home range size was greater for males than females during the breeding season, but did not differ between the seasons for kit foxes in Utah (Arjo et al. 2003), swift foxes (Kitchen et al. 1999), Blanford’s foxes (Geffen and Macdonald 1992), and culpeo foxes (Pseudalopex culpaeus; Salvatori et al. 1999).
In order to search for a mate during the breeding season, male foxes may increase their number of exploratory movements, which may be especially pronounced in the urban environment where 50 patches of habitat suitable to support kit foxes are small and disjunct. Home range size may have been underestimated during the pair formation and breeding seasons, because fewer kit foxes were located during this time. This may explain why mean home range size was significantly larger during the dispersal season than the pair formation and breeding seasons.
Habitat use
Habitats were known to be correctly classified for 68% of all independent locations, which were obtained by following the transmitted signal until the animal was observed or tracked to a den. It was unlikely that visually observed kit foxes were behaviorally pushed from one habitat to another, because kit foxes were resting or walking 67% of the time. However, distance between the animal and the radio-receiver, as well as broken topography, can increase telemetry error (Harris et al. 1990). Telemetry error was a concern because correct assignment of habitat use required accurate locations. Based on average telemetry error in urban coyote studies (Romsos 1998, Grinder and Krausman 2001), triangulated kit fox locations less than 100 m from the nearest habitat-patch edge may have been misclassified. The remaining 32% of locations were determined by triangulation or encircling the habitat patch. These locations averaged 31 m from the nearest habitat-patch edge and may have included some misclassification.
Like urban kit foxes, rural kit foxes do not use habitat within their home range in a uniform manner (Golightly 1981, Hardenbrook 1987) and have distinct core areas of concentrated activity (Koopman 1995). Kit foxes used open and sump habitats more than their availability in both the study area and in home ranges, and there was significantly more open and sump habitat in home ranges than in the study area. Likewise, urban red foxes (Sallee 1998) and coyotes (Romsos 1998) in Orange County, California used vacant field habitats more than expected. The higher vegetative cover in vacant fields may facilitate predator avoidance and support a more abundant prey base (Adams and Dove 1989) than the other less used urban habitats. Likewise, 51 sumps had marsh vegetation, which provides food and cover for wildlife and facilitates use by terrestrial wildlife (Adams and Dove 1989). Therefore, sumps may serve as artificial urban wetlands that provide denning habitat with their sloping sides, foraging opportunities based on the abundance of active small mammal burrows (personal observation), and a constant source of water, which I observed an urban kit fox drinking. In hot environments, such as Arizona, rural kit foxes meet their water needs through prey consumption (Golightly and Ohmart 1984). With the availability of free-standing water in the urban environment, kit foxes may require less food.
The number of people in the same habitat patch as the kit fox was lowest in open and sump habitats. While the greatest number of pedestrians observed along roads were near sumps, the fencing around sumps provided a physical and visual barrier between kit foxes and passing pedestrians. The shelter and security that the fenced perimeters provided may also explain why Stafford and Murphy (1992) found kit fox dens in 10 of the 95 sumps that they surveyed in Bakersfield. Likewise, urban red foxes disproportionate use of industrial habitats may be attributed to security personnel and perimeter fencing, which limited intrusion by humans and their pets (Sallee 1998).
There was significantly less residential habitat in urban kit fox home ranges than in the study area; the opposite was true for urban coyotes in Tucson, Arizona (Grinder and Krausman 2001). Harrison (1997) found that gray foxes (Urocyon cinereoargenteus) in New Mexico avoided high-density residential subdivisions. Urban coyotes (Romsos 1998) and red foxes (Sallee 1998) in Orange County, California avoided high-density residential and commercial habitats, perhaps due to a greater possibility for human and domestic animal interactions.
Likewise, Lucherini et al. (1995) found that red foxes used habitats with less human access and disturbance.
Industrial and linear habitats had a higher incidence of passing vehicles than all other habitats. This may be because industrial habitats tend to occur along major roads. In linear 52 habitat, from 1800 to 1859 h and 0700 to 0759 h, both the number of kit fox locations and number of passing vehicles peaked (Appendix E). However, during these times, 84% of the kit foxes using the linear habitat were located in dens that sheltered them from the disturbance of the passing vehicles.
The kit fox is one of the few canids that utilizes an underground den throughout the year (Berry et al. 1987, Koopman et al. 1998). Because dens are used for whelping and rearing pups, for escape cover from predators (Grinnell et al. 1937), and to minimize water loss and heat stress in summer and metabolic costs in winter (Golightly 1981, Golightly and Ohmart 1983), kit fox presence is limited by the availability of (Spiegel et al. 1996) or their ability to build dens. Like rural kit foxes in California (Knapp 1978, Berry et al. 1987, Reese et al. 1992) and Utah (Egoscue 1956, Arjo et al. 2003) and swift foxes (Kilgore 1969), urban kit foxes primarily used subterranean dens. However, they also used alternative dens, including pipes. Use of pipes that are known to interfere with radio signals, may have caused an underestimation of the number of alternative dens used in this study (Berry et al. 1987, Spiegel et al. 1996, Koopman et al. 1998).
Like Golightly (1981), I found that kit foxes did not randomly select den sites. Because kit foxes selected sump habitats for denning, there was more area of sump habitat in core areas than in home ranges. Sumps may also be used for denning because they are fenced and not accessible to the public. Likewise, most urban red fox dens occurred within fenced areas that may have isolated dens from human disturbance (Sallee 1998). Stafford and Murphy (1992) found that the majority of sumps used by urban kit foxes for denning were adjacent to undisturbed habitat, which likely has a low human presence.
Furthermore, I found that urban kit foxes denned in open habitats more than their availability in the study area. Likewise, rural kit foxes in California (Morrell 1971, Morrell 1972), Utah (Egoscue 1956, Egoscue 1962), and Arizona (Zoellick et al. 1989) and urban red 53 foxes (Lewis et al. 1993) frequently denned in flat, open areas. Kit foxes may be less vulnerable to coyote and bobcat predation on flat or rolling grasslands (Warrick and Cypher 1998).
Linear habitats (i.e., along canals, railroads, freeway embankments, and powerline rightof-ways) were used in proportion to their availability for denning. Like swift foxes, urban kit foxes utilized dens in road right-of-ways (Matlack et al. 2000). However, urban kit foxes denned near roads less than expected and in larger habitat patches than expected. Similarly, red foxes used habitats with less human access and disturbance for resting (Lucherini et al. 1995).
Movements
Kit foxes moved at an average rate of 1.33 km/h, nearly identical to that for kit foxes in southwestern Kern County (1.35 km/h; Koopman 1995) but slower than that for kit foxes in Arizona (males: 2.73 km/h; females: 1.49 km/h; Golightly 1981) and faster than that for swift foxes (males: 0.68 km/h; females: 0.59 km/h; Kitchen et al. 1999). Between dusk and dawn (i.e., approximately 10 to 14 h, depending on time of year), rural kit foxes in Arizona moved an average distance of 14.3 km for males and 11.8 km for females (Zoellick et al. 1989) and in southwestern Kern County, moved an average distance of 9.8 km for males and 10.9 km for females (Zoellick et al. 1987), yielding average movement rates similar to that for urban kit foxes.
The average distance that captured urban red foxes, raccoons, and skunks in Toronto, Canada moved from the point of release was less than that for their rural counterparts, which indicated that food and habitat in the urban environment were not limited in availability (Rosatte et al. 1991).
Males, which had larger 100% minimum convex polygon home ranges than females, may travel at higher rates of speed during the early part of the evening to cover their larger territory.
In Arizona, kit fox activity peaked in the early evening and a few hours before sunset, and males spent twice as much time out of the den, traveled 3.6 times farther, and maintained home ranges 54 2.6 times larger than females (Golightly 1981). However, in the urban setting, I did not detect a difference between sexes, movement session times, or their interaction with regard to maximum speed, mean speed, or total adjusted distance moved during each movement session. Similarly, lengths of nightly movements did not differ among sexes for rural kit foxes (Zoellick et al. 2002) and Blanford’s foxes (Geffen and Macdonald 1992). Compared to Arizona, where male kit foxes spent much time by the boundaries of their territory to defend a non-uniformly distributed resource base (Golightly 1981), urban kit foxes were able to meet their resource needs within small home ranges and did not need to travel far due to the concentration of resources within distinct habitat patches in the urban landscape.
Kit fox movement speed was not correlated with the number of passing vehicles, passing pedestrians, or people in the same habitat patch. This is consistent with the findings in Lewis et al. (1993), which indicated that urban red foxes were tolerant of humans. Nevertheless, kit foxes may have attempted to avoid human interactions by traveling at a high rate through residential, manicured open, and commercial habitats, all which had a high incidence of people.
Sump and transition habitats were typically small patches that were free of people at night when kit foxes were active. Kit foxes were observed foraging in and caching food scavenged from construction sites. Furthermore, the remains of several species that live in sumps, including bullfrog (Rana catesbeiana), burrowing owl (Athene cunicularia), duck (unidentified species), pocket gopher, squirrel, and opossum, were observed on kit fox dens in sumps (personal observation). Use of sump and transition habitats for hunting or scavenging refuse may explain why kit foxes traveled short distances at low speeds in these habitats.
Kit foxes used linear habitats (i.e., the Kern River Parkway, canals, and right-of-ways for highways, railroads, and powerlines) as corridors to move throughout their home range. Because highway, railroad, and powerline right-of-ways were fenced to prohibit public access, kit foxes may not have been compelled to move quickly through this habitat type. Kit foxes moved long 55 distances quickly through manicured open habitats, perhaps because this habitat had a high occurrence of humans and was used mostly as a corridor for traveling, similar to urban red foxes’ use of golf courses in Toronto, Canada (Rosatte et al. 1991).
Kit foxes in urban areas may have shorter nightly movements due to anthropogenic food sources (Zoellick et al. 1987). Consequently, movement distance may be influenced by foraging efficiency. Movement distance was less in commercial habitats (where kit foxes were observed foraging in parking lots and trash dumpsters) and transition habitats, both which tend to have an abundance of discarded food items (personal observation). Conversely, kit foxes moved longer distances in open, grassland habitat. This may have been because small, insectivorous prey of kit foxes and swift foxes tend to be evenly distributed in grassland habitats (Kamler et al. 2004).
Similarly, Koopman (1995) noted that food resources were uniformly distributed in rural kit fox home ranges.
Movements of kit foxes differed with regard to habitat type and time of night. From 1830 – 2230 h, linear habitat was used more than expected for kit fox resting/walking movements. This was probably because 23% of kit fox dens were in linear habitat. From 2230 – 0330 h, kit fox trotting and running movements were higher than expected in open habitat, which was likely used for foraging and traveling. From 2230 – 0330 h, kit fox resting/walking movements were less than expected in residential habitat, in which only one den was located. Kit foxes’ high rate of speed through residential habitat indicates that they used this habitat type as a means to get to a more used habitat. From 2230 – 0730 h, kit fox trotting movements were less than expected in sump habitat, which may be used primarily for denning rather than foraging.
From 0330 – 0730 h, industrial habitat was used less than expected for kit fox running movements. Kit fox speed may have been lower in industrial habitats during these hours due to the absence of humans or the presence of refuse.
56 Urban habitat was of sufficiently high quality to support kit foxes with low mortality and normal weight and offspring production. This was likely due to the widespread availability of natural and human-derived food sources and protected (i.e., fenced) areas with cover. Kit fox core areas contained a disproportionately high amount of sumps, which had food and den sites and restricted public access. The availability of sump and open habitats, which kit foxes selected for denning, may shape the distribution and abundance of the urban population. Portions of the urban landscape without these prime denning habitats may not be able to support kit foxes. 57 MANAGEMENT RECOMMENDATIONS
The kit foxes in Bakersfield had low mortality, similar weight and mean litter size, and high reproductive success, compared to that for rural kit foxes. Urban kit foxes appeared to have adapted to urban conditions and resources, and may contribute to the San Joaquin Valley metapopulation.
Urban kit foxes were observed crossing roads (up to four lanes), but also used culverts and a bridge to move under them, which may help explain the relatively low mortality. Vehicular mortality should be monitored around sump and open habitats. If increased mortality is observed, additional culverts may need to be placed and maintained under roads, along with animal-proof fencing to direct kit foxes to the culverts (Ng et al. 2004). Mid-sized mammals’ (i.e., raccoons and skunks) use of culverts is positively correlated to culvert length and negatively correlated to culvert area (Ng et al. 2004). Small diameter culverts (i.e., 0.5 m) may serve a dual purpose by providing a place for urban kit foxes to hide from larger predators and facilitating kit fox movement in a fragmented landscape.
To promote the continued existence of kit foxes in urban settings, such as Bakersfield, habitat will need to be retained and managed to meet their needs. Urban kit foxes denned farther from roads than expected in habitat patches that were larger than expected, and thus, may benefit from the retention of larger open and sump habitat patches for denning. Urban kit foxes had less spatial overlap and smaller home ranges and core areas than their rural counterparts. The greater presence of anthropogenic food sources in cities may enable urban kit foxes to meet their energetic needs in a smaller area than kit foxes in rural, grassland habitats, where food resources may be more dispersed (Kamler et al. 2004). Kit foxes utilized open lots and sumps more than all other urban habitat types.
58 Golightly (1981) concluded that dens were important to kit fox energetics and a consideration in the management of this species. If kit foxes are to be retained in Bakersfield, open lots, to provide foraging and denning habitat, and uniformly-distributed, sumps that are fenced and closed to the public, to provide kit fox denning habitat, will need to be maintained throughout the city. Sump maintenance (e.g., grading or paving) may be a potential hazard to kit foxes (Murphy 1992) and should be avoided. With sensitivity to kit fox presence in the urban environment, much protection can be afforded at a low cost.
The kit fox recovery strategy identified that “connections need to be established, maintained, and promoted between populations to counteract negative consequences of inbreeding, random catastrophic events (e.g., droughts) and demographic factors” (United States Fish and Wildlife Service 1998). Urban kit foxes used the Kern River Parkway to move throughout their home range. The Kern River Parkway should be maintained and managed to facilitate kit fox movement. In addition, dog management may be required because dogs may pose a threat to urban kit foxes as they have for rural kit foxes (Ralls and White 1995, Cypher et al. 2000).
Like urban red foxes in Great Britain (Kolb 1984) and Toronto, Canada (Rosatte et al. 1991) that use railroad corridors to move throughout their home range, urban coyotes (Romsos 1998), red foxes (Lewis et al. 1993, Sallee 1998), and kit foxes used canals (including foot bridges over canals) and railroad, highway, and powerline right-of-ways for moving and denning.
The continued existence of these right-of-ways, which are fenced to prohibit public access, will facilitate kit fox movement throughout the city. Kit foxes can persist in urban areas if an adequate mosaic of habitat is conserved and managed appropriately. 59 REFERENCES
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Species captured
Habitat type Trap-nights Kit foxes Domestic cats Opossums Residential 5 1 0 0
Commercial 11 6 2 0
Industrial 41 13 5 0
Linear 84 19 3 1
Manicured open 53 21 0 0
Open 54 23 3 0
Sump 327 128 33 2
Total 575 211a 46 3
a Includes recaptures but excludes 32 captures which occurred when the number of traps in use was not recorded.
Appendix B. Kit fox location data and estimates for home range size, core area size, and time to independence for 28 radiocollared kit foxes that were monitored between May 1997 and January 1998 in Bakersfield, California.
Kit Fox Locations Home Range (km2)
Eartag Sex Sequential Daily Independent 100% MCP a 95% Fixed Kernel 50% Fixed Kernel
Core Area (km2) Time to Independence (h)
3468 F - 166 149 1.17 0.41 0.05 -
5468 F 190 193 166 1.36 0.94 0.08 1.69
5702 F 190 196 184 0.72 0.40 0.06 2.29
5703b F - 8 7 - - - -
5705 F - 183 163 2.71 2.70 0.20 -
5708 F 133 164 151 1.89 1.67 0.32 1.70
5713 F - 162 131 2.19 1.59 0.28 -
5723 F - 190 161 0.93 0.41 0.02 -
5741 F 166 181 174 1.32 0.66 0.08 3.89
5742 F - 213 177 2.69 2.78 0.43 -
5747 F 165 187 173 0.38 0.28 0.04 1.23
5752 F - 182 155 0.59 0.52 0.03 -
70 Appendix B. Kit fox location data and estimates for home range size, core area size, and time to independence for 28 radiocollared kit foxes that were monitored between May 1997 and January 1998 in Bakersfield, California (continued).
Kit Fox Locations Home Range (km2)
Eartag Sex Sequential Daily Independent 100% MCP a 95% Fixed Kernel 50% Fixed Kernel
Core Area (km2) Time to Independence (h)
5753 F - 198 162 1.07 0.67 0.06 -
5754 F - 79 64 1.63 2.75 0.32 -
5756 F - 189 164 0.36 0.35 0.07 -
5674 M 167 181 168 3.33 2.69 0.46 2.61
5701 M - 206 178 0.86 0.22 0.02 -
5704 M 230 203 193 2.16 2.40 0.39 1.80
5707 M - 179 160 2.70 2.50 0.50 -
5710 M 187 153 145 1.21 0.37 0.05 2.67
5711 M - 180 164 2.60 0.15 0.05 -
5712 M - 167 137 1.90 1.30 0.11 -
5721 M - 185 158 2.02 1.70 0.27 -
71 Appendix B. Kit fox location data and estimates for home range size, core area size, and time to independence for 28 radiocollared kit foxes that were monitored between May 1997 and January 1998 in Bakersfield, California (continued).
Kit Fox Locations Home Range (km2)
Eartag Sex Sequential Daily Independent 100% MCP a 95% Fixed Kernel 50% Fixed Kernel
Core Area (km2) Time to Independence (h)
5743 M 219 186 165 2.13 1.14 0.09 1.90
5744 M - 190 156 2.72 2.27 0.22 -
5746 M - 176 147 0.31 0.04 0.01 -
5755 M 163 168 154 1.11 0.30 0.03 1.74
5757 M - 159 143 4.49c 15.58d 4.00d-
Total 1810 4824 4249 - - - -
Mean 181 172.3 151.75 1.72 1.2 0.16 2.15
SE 9.04 7.62 6.89 0.19 0.19 0.03 0.24
a Minimum convex polygon.
b
Located too few times to be included in the home range and habitat use analyses. c Sum of two distinct home ranges in the southeastern (3.19 km2 ) and northwestern (1.31 km2) parts of the study area, approximately 3.1 km apart.
d Outlier that was excluded from calculation of x¯ + 1 SE. 72 Appendix C. Weight, hind foot, and ear measurements for captured adult, subadult, and pup kit foxes in Bakersfield, California between May 1997 and January 1998.
Male Female
Body Measurement Age n x¯ SE n x¯ SE Statistica p
Weight (kg) Adult 29 2.47 0.05 32 2.16 0.03 t = -5.53 <0.001 Subadult 7 2.09 0.11 6 1.87 0.14 t = -1.29 0.22
Pup 20 1.73 0.04 13 1.44 0.05 t = -4.25 <0.001
Hind foot (mm) Adult 27 125.5 1.0 31 119.8 0.8 t = -4.4 <0.001 Subadult 6 121 1.2 5 118.4 0.9 t = -1.67 0.13
Pup 18 121 1.2 9 112.2 1.4 t = -4.36 <0.001
Ear from notchb (mm) Adult 28 81.4 0.6 31 78.6 0.7 z = 3.28 <0.001 Subadult 6 82.5 0.6 5 78.4 1.3 t = -3.04 0.007
Pup 19 80.1 0.8 10 75.3 1.1 t = -3.65 <0.001
Ear from rearc (mm) Adult 28 84.4 0.7 31 81.5 0.7 t = -2.81 0.002 Subadult 6 84.8 1.1 5 81.2 2.2 t = -1.56 0.15
Pup 19 80.8 0.8 10 77.1 1.1 t = -2.6 0.007
a
I used a 2-sample t-test to determine if means differed between the sexes. For data that was not normally distributed, I used a Mann-Whitney U-test to determine if medians differed between the sexes. b Tip of ear to notch at anterior base.
c Tip of ear to posterior base.
73 74
Appendix D. Area-observation curves using the 100% minimum convex polygon home range for 27 kit foxes in Bakersfield, California from May 1997 to January 1998.
Females
0 0.5
1 1.5
2 2.5
3 3.5
4 0 20 40 60 80 100 120 140 160 180
Home Range Area (km
2)
3468 5468 5702 5705
5708 5713 5723 5741
5742 5747 5752 5753
5754 5756
Males
0 2
4 6
8 10
12 14
16 0 20 40 60 80 100 120 140 160 180 200
Number of Locations
Home Range Area (km
2)
5674 5701 5704
5707 5710 5711
5712 5721 5743
5744 5746 5755
5757
Appendix E. The percentage of all radiocollared kit fox daily locations (n = 4,824) and passing vehicles documented in linear habitats during each hour in Bakersfield, California from September 1997 to January 1998. 0 2
4 6
8 10
12 14
16 1500-1559 1600-1659 1700-1759 1800-1859 1900-1959 2000-2059 2100-2159 2200-2259 2300-2359 0000-0059 0100-0159 0200-0259 0300-0359 0400-0459 0500-0559 0600-0659 0700-0759 0800-0859 0900-0959 Time Percent
Kit Fox Locations in Linear Habitat
Vehicles Passing on Nearest Road
75 EXHIBIT E
April 15, 2026
Via email: [email protected]
City Council of the City of Bakersfield
City Hall
1501 Truxtun Avenue
Bakersfield, CA 93301
Re: Applicant’s response to appeal of Vesting Tentative Tract Map 7500 Dear Honorable Councilmembers:
On behalf of the applicant for Vesting Tentative Tract Map 7500 (the “project”), McIntosh & Associates, we submit this response to the appeal filed by Supporters Alliance for Environmental Responsibility (“SAFER”), challenging the August 21, 2025, approval of the project by the City Planning Commission.
SAFER demands that a new environmental impact report (EIR) or mitigated negative declaration (MND) be prepared for the project, alleging that additional analysis is required to consider potential impacts to biological resources and air quality. SAFER is wrong—no further environmental review is required, because the previously adopted MND on which the City relies remains applicable and relevant, and there are no substantial changes to the original project, no substantial changes in circumstances under which the project will be undertaken, and no new environmental impacts have been identified which would trigger the need for additional environmental review under CEQA.
Background
The project proposes a vesting tentative tract map for 208 single-family residential lots on
39.92 acres in the City of Bakersfield. In 2007, the City began the process of authorizing residential development at the site, and in 2008, the City Council approved a General Plan Amendment and Zone Change and an associated MND.
On August 21, 2025, the Planning Commission unanimously approved the project, finding that no further environmental documentation was necessary because no new, or substantially more severe, significant impacts will result from the proposed project compared to those previously Sabrina V. Teller
[email protected]
Applicant’s Response to Appeal re: VTTM 7500
April 15, 2026