General Distribution
The historic range of San Joaquin kit fox included most of the San Joaquin Valley as well as low-elevation
basins and ranges along the eastern side of the central Coast Ranges. By 1930 this range was
reduced by more than half, with the largest populations occurring in the southern and western portions of
the San Joaquin Valley. Today, San Joaquin kit fox occurs in the remaining native valley and foothill
grasslands and chenopod scrub communities of the valley floor and surrounding foothills from southern
Kern County north to Los Ba๑os, Merced County. Smaller, less dense populations may be found farther
north and in the narrow corridor between Interstate 5 and the Interior Coast Ranges from Los Ba๑os to
Contra Costa County. The taxon's range also includes portions of Monterey, Santa Clara, and San
Benito Counties and the upper Cuyama River watershed in northern Ventura and Santa Barbara and
southeastern San Luis Obispo Counties (Brown and others 1997, U.S. Fish and Wildlife Service 2001).
San Joaquin kit fox potentially occurs on the Los Padres National Forest in the upper Cuyama Valley
watershed and along the eastern slope of the La Panza Range. There are currently no known denning
sites on National Forest System lands in southern California. Further, no reliable estimate exists for
numbers of San Joaquin kit fox using National Forest System lands for foraging. The taxon is most
likely a transient visitor on National Forest System lands in southern California because little high-quality
denning habitat is available (U.S. Fish and Wildlife Service 2001). Systematics
The genus Vulpes contains 1013 species, depending on the authority consulted (McGrew 1979). San
Joaquin kit fox is one of eight recognized subspecies of kit fox (Vulpes macrotis). Two other
subspecies, V. m. macrotis and V. m. arsipus, occur in southern California (Samuel and Davis 1982).
However, Waithman and Roest (1977) synonymized arsipus with mactotis. Habitat Requirements
San Joaquin kit fox inhabits a variety of habitats, including grasslands, scrublands, vernal pool areas,
alkali meadows and playas, and an agricultural matrix of row crops, irrigated pastures, orchards,
vineyards, and grazed annual grasslands (Williams and others 1998). They prefer habitats with loose-textured
soils and are primarily found in arid grasslands and open scrublands that are suitable for
digging, but they occur on virtually every soil type (Egoscue 1962, Grinnell and others 1937, Hall 1946,
McGrew 1979, Morrell 1972).
Dens are generally located in open areas with grass or grass and scattered brush, and seldom occur in
areas with thick brush (Morrell 1972). Preferred sites are relatively flat, well-drained terrain (Roderick
and Mathews 1999, Williams and others 1998). They are seldom found in areas with shallow soils
resulting from high water tables (McCue and others 1981) or impenetrable bedrock or hardpan layers
(Morrell 1972, O'Farrell and Gilbertson 1979, O'Farrell and others 1980). However, kit fox may occupy
soils with high clay content where they can modify burrows dug by other animals, such as ground
squirrels (Spermophilus beecheyi) (Orloff and others 1986). These foxes will den within small parcels
of native habitat that is surrounded by intensively maintained agricultural lands (Knapp 1978) and
adjacent to dryland farms (Orloff and others 1986, Williams and others 1998). Reproduction
Kit fox can, but do not necessarily, breed in their first year of adulthood (Morrell 1972). Sometime
between February and late March, two to six pups are born per litter (Cypher and others 2000, Egoscue
1956, Morrell 1972, Zoellick and others 1987). Reproductive success in kit fox is correlated with prey
abundance (Egoscue 1975). Population growth rates generally vary positively with reproductive
success, and kit fox density is often positively related to both the current and previous years' prey
availability (Cypher and others 2000). Prey abundance is generally strongly related to the previous
year's effective (OctoberMay) precipitation. Daily/Seasonal Activity
Kit fox are primarily nocturnal and is active year-round. However, they are commonly seen during the
day in the late spring and early summer.
Kit fox in the wild can live as long as 8 years, but such longevity is rare (Williams and others 1998). In
captivity, kit fox can live up to 10 years (McGrew 1979). Annual survival rates of juvenile kit foxes in
the wild generally range from 21 percent to 41 percent (Berry and others 1987, Ralls and White 1995),
while that of adults is approximately 50 percent (Berry and others 1987, Egoscue 1975, Morrell 1972,
Ralls and White 1995). Coyotes (Canis latrans) and other predators (red fox [Vulpes vulpes], domestic
dogs, bobcats [Felis rufus], and large raptors) constitute the primary cause of mortality for adult and
juvenile foxes (Cypher and others 2000, Berry and others 1987, Hall 1983, O'Farrell and others 1987,
Ralls and White 1995, White and others 2000), and vehicles are usually the secondary cause (Cypher
and others 2000). Diet and Foraging
The diet of San Joaquin kit fox varies with season and geographic area, depending on local availability
of prey. In the southern portion of the range, approximately one-third of the diet consists of kangaroo
rats, pocket mice, white-footed mice, and other nocturnal rodents. Kit fox also feed on ground squirrels,
black-tailed hares, San Joaquin antelope squirrels, cottontails, ground-nesting birds, insects, and
vegetation (grasses) (Egoscue 1963, Laughrin 1970, Morrell 1972). Territoriality/Home Range
Home ranges vary from less than 1 square mile (2.59 square kilometers) to approximately 12 square
miles (31.08 square kilometers) (Knapp 1978, Morrell 1972, Spiegel and Bradbury 1992, White and
Ralls 1993, Zoellick and others 1987). The home ranges of pairs or family groups of kit foxes generally
do not overlap (White and Ralls 1993). Predator-Prey Relations
San Joaquin kit fox are preyed upon by coyotes, nonnative red foxes, domestic dogs, eagles, and large
hawks (Berry and others 1987, Hall 1983, O'Farrell and others 1987, Ralls and White 1995). Literature Cited
Berry, W.H.; Scrivner, J.H.; O'Farrell, T.P.; Harris, C.E.; Kato, R.T.; McCue, P.M. 1987. Sources and
rates of mortality of the San Joaquin kit fox, naval petroleum reserve #1, Kern County, California, 1980
1986. Report No. EGG 10282-2145. U.S. Department of Energy Topical Report, EG&G/EM Santa
Barbara Operations
Brown, N.L.; Johnson, C.D.; Kelly, P.A.; Williams, D.F. 1997. San Joaquin kit fox, Vulpes macrotis
mutica. [Online]. Available: http://arnica.csustan.edu/esrpp/sjkfprof.htm.
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McCue, P.M.; Scrivner, J.H.; Zoellick, B.W. 2000. Population dynamics of San Joaquin kit foxes at the
naval petroleum reserves in California. Wildlife Monographs 145: 143.
Egoscue, H.J. 1956. Preliminary studies of the kit fox in Utah. Journal of Mammalogy 37: 351357.
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Turbine Generating Project site, Alameda County, California. California Department of Fish and Game.
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proposed as Phase II, Kesterson Reservoir, Merced County, California. Topical Report EGG 1183-
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Land Management lands in southern and southwestern San Joaquin Valley. Final Report. ECC 1183-
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the northern extreme of their range. Transactions of the Western Section Wildlife Society 22: 6070.
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California. Portland, OR.
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Kit Fox prior to or during ground disturbance. Prepared by the Sacramento Fish and Wildlife Office,
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implementation of land and resource management plans for the four southern California national
forests, as modified by new interim management direction and conservation measures (1-6-00-F-773.2).
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58: 157164.
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population of kit foxes. Southwestern Naturalist 45(2): 204211.
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Information gathered from California DFG - California Interagency Wildlife Task Group
