Appendix X 

Status and Life History of the San Joaquin Kit Fox (Vulpes macrotis mutica) 

1.1 Species Listing Status (ok) 

The San Joaquin kit fox (Vulpes macrotis mutica) was listed as endangered on March 11, 

1967 (32 FR 4001) by the U.S. Fish and Wildlife Service (USFWS) (USFWS, 1967). A 

recovery plan for upland species of the San Joaquin Valley was approved by the USFWS 

on September 30, 1998 (USFWS, 1998). 

1.2 Description and Taxonomy (ok) 

Generally, kit foxes are characterized by “a small, slim body, relatively large ears set 

close together, narrow nose, and a long bushy tail tapering slightly toward the tip. The 

tail is typically carried low and straight” (USFWS, 1998). The kit fox is the smallest 

species in North America in the “Canidae family, which includes dogs, wolves and 

foxes” (USFWS, 1998 and 2008). San Joaquin kit foxes (SJKF) have “an average body 

length of 20 inches and weight of about 5 pounds” (USFWS, 2008). However, 

differences between males and females exist. “Males averaged 80.5 centimeters (31.7 

inches) in total length, and 29.5 centimeters (11.6 inches) in tail length; females averaged 

76.9 centimeters (30.3 inches) in total length, and 28.4 centimeters (11.2 inches) in tail 

length” (USFWS, 1998). Kit foxes are about “30 centimeters (12 inches) high at the 

shoulder” (USFWS, 1998). “The average weight of adult males is 2.3 kilograms (5 

pounds), and of adult females at 2.1 kilograms (4.6 pounds)” (USFWS, 1998). The 

“color and texture of the fur coat of kit foxes varies geographically and seasonally” 

(USFWS, 1998). “Two distinctive coats develop each year: a tan summer coat and a 

sliver-gray winter coat. The undersides vary from light buff to white, with the shoulders, 

lower sides, flanks and chest varying from buff to a rust color. The ear pinna (external 

ear flap) is dark on the back side, with a thick border of white hairs on the forward-inner 

edge and inner base. The tail is distinctly black-tipped” (USFWS, 1998). 

Historically, eight subspecies of kit fox (V. macrotis) were recognized (USFWS, 1998). 

However, “several different taxonomies for the species and subspecies of small, North 

American foxes have been proposed over the last 110 years” (USFWS, 1998). A study 

published in 1990 “concluded that all North American arid-land foxes belonged to the 

species V. velox (swift fox)” (USFWS, 1998). This study also challenged the 

“subspecific statuses of the taxa historically regarded as subspecies of V. macrotis” and 

“recommended that all be synonymized under V. velox macrotis” (USFWS, 1998). A 

genetic study published in 1993 suggested that “though there was evidence of 

hybridization between kit and swift foxes over a limited geographic area, they should be 

considered separate species” (USFWS, 1998). This study also determined that “of the 

traditional subspecies of the kit fox, the San Joaquin Valley population is the most 

distinct and should be considered a subspecies” (USFWS, 1998). The data from this 

study recognize “two subspecies of kit foxes: V. macrotis macrotis, found throughout the 

remaining habitat within the historical range of the species, except the San Joaquin kit 

fox range; and V. macrotis mutica, the San Joaquin kit fox” (USFWS, 1998). “The San 

1
Joaquin kit fox is the largest subspecies in skeletal measurements, body size, and weight” 

(USFWS, 1998). “The type locality is near Tracy, San Joaquin County, California” 

(USFWS, 1998). 

1.3 Distribution and Status 

Historical Range: (ok) 

“Although the San Joaquin kit fox has been listed as endangered for over 30 years, there 

has never been a comprehensive survey of its entire historical range. And, despite the 

loss of habitat and apparent decline in numbers since the early 1970s, there has been no 

new survey of habitat that was then thought to be occupied” (USFWS, 1998). 

 

“As early as 1925,” kit foxes were reported “from the Panoche Creek area in the foothills 

of western Fresno County, and east of Rose Station (Fort Tejon) in southern Kern County 

at an elevation of 363 meters (1,200 feet)” (USFWS, 1998). It is likely that kit foxes 

“have always occurred in these areas” just at low densities (USFWS, 1998). “Prior to 

1930, kit foxes inhabited most of the San Joaquin Valley from southern Kern County 

north to Tracy, San Joaquin County, on the west side, and near La Grange, Stanislaus 

County, on the east side” (USFWS, 1998 and 2008). Another USFWS source stated that 

the range extended farther west to Contra Costa County on the west side (USFWS, 1998). 

“Tracy was the farthest northwest record” until the 1990s; however, records now exist 

“from the Antioch area of Contra Costa County” (USFWS, 2008). “By 1930, the kit fox 

range had been reduced by more than half, with the largest portion remaining in the 

southern and western parts of the Valley” (USFWS, 1998 and 2008). However, no 

indication was provided for why it was believed that the foxes “had been eliminated from 

most of the east side and Valley floor” (USFWS, 1998). 

Current Range: (ok) 

“The San Joaquin kit fox is found only in the Central Valley area of California” (East 

Contra Costa County HCP/NCCP, 2006). “The distribution of kit foxes in California 

includes all or portions of Alameda, Contra Costa, Fresno, Kern, Kings, Merced, 

Monterey, San Benito, San Joaquin, San Luis Obispo, Santa Barbara and Tulare 

counties” (SJCOG). Stanislaus, Madera, Santa Clara, and Ventura counties should also 

be included in the list above. The counties are divided into the three regions (northern, 

central, and southern) which consist of the following counties: northern (Alameda, 

Contra Costa, San Joaquin, and Santa Clara), central (Fresno, Kings, Madera, Merced, 

San Benito, Stanislaus, and Tulare), and southern (Monterey, Kern, San Luis Obispo, and 

Santa Barbara) (Cal. EPA. Dept of Pesticide Regulation, 2002). 

“Despite the lack of a comprehensive survey, local surveys, research projects and 

incidental sightings indicate that kit foxes currently inhabit some areas of suitable habitat 

on the San Joaquin Valley floor and in the surrounding foothills of the coastal ranges, 

Sierra Nevada, and Tehachapi Mountains, from southern Kern County north to Contra 

Costa, Alameda, and San Joaquin Counties on the west, and near La Grange, Stanislaus 

County on the east side of the Valley, and some of the larger scattered islands of natural 

land on the Valley floor in Kern, Tulare, Kings, Fresno, Madera, and Merced Counties. 

2
Kit foxes also occur westward into the interior coastal ranges in Monterey, San Benito, 

and Santa Clara Counties (Pajaro River watershed), in the Salinas River watershed, 

Monterey and San Luis Obispo, and in the upper Cuyama River watershed in northern 

Ventura and Santa Barbara Counties and southeastern San Luis Obispo County. Kit 

foxes are also known to live within the city limits of the city of Bakersfield in Kern 

County” (USFWS, 1998). 

“The largest extant populations of kit foxes are in western Kern County on and around 

the Elk Hills and Buena Vista Valley, Kern County, and in the Carrizo Plain Natural 

Area, San Luis Obispo County. The kit fox populations of Elk Hills and the City of 

Bakersfield, Kern County, Carrizo Plain Natural Area, San Luis Obispo County, CiervoPanoche Natural Area, Fresno and San Benito Counties, Fort Hunter Liggett, Monterey 

County, and Camp Roberts, Monterey and San Luis Obispo Counties have been recently, 

or are currently, the focus of various research projects. Though monitoring has not been 

continuous in the central and northern portions of the range, populations were recorded in 

the late 1980s at San Luis Reservoir, Merced County, North Grasslands and Kesterson 

National Wildlife Refuge area on the Valley floor, Merced County, and in the Los 

Vaqueros watershed, Contra Costa County in the early 1990s. Smaller populations and 

isolated sightings of kit foxes are also known from other parts of the San Joaquin Valley 

floor, including Madera County and eastern Stanislaus County” (USFWS, 1998). 

“The kit fox population is fragmented, particularly in the northern part of the range” 

(USFWS, 2008). The habitat is in the northern part of the range “is not as good as it is to 

the south because there’s not as much of it” and “it’s pinched between heavy agricultural 

land and coastal mountains” as a result there are “not as many kit foxes there” (Ridgley, 

2007). “A recent survey of Contra Costa County and Alameda Counties within the 

known range of the San Joaquin kit fox found no evidence of recent occupancy” (East 

Contra Costa County HCP/NCCP, 2006). “Despite a total of 139.4 km surveyed” “in 

2002 in Contra Costa and Alameda Counties (81.0 km in Contra Costa County), no sign 

of San Joaquin kit fox was found” (East Contra Costa County HCP/NCCP, 2006). 

“These results do not prove absence of kit fox from the inventory area (e.g., no private 

land was surveyed with detection dogs), but do suggest that kit fox density is low or their 

occurrence is periodic in the inventory area” (East Contra Costa County HCP/NCCP, 

2006). 

Status: (ok) 

The estimated range-wide population “of adult kit foxes prior to 1930 may have been 

between 8,667 and 12,134 assuming an occupied range of 22,447 square kilometers 

(8,667 square miles)” (USFWS, 1998). A study published in 1970 “reported an estimated 

total population size of 1,000 to 3,000 foxes in 1969” (USFWS, 1998). In the early 

1970s, the “kit fox population in San Luis Obispo, Santa Barbara, Kings, Tulare and Kern 

Counties was estimated to be about 11,000 animals” (USFWS, 1998). However, this 

number was “based on limited aerial surveys of pupping dens and amount of historic 

habitat, but without correction for cultivated and urbanized lands” (USFWS, 1998). A 

study published in 1975 “conducted a more thorough investigation of kit fox abundance 

in 14 counties in which kit foxes were known to occur and estimated the total population 

3
at 14,832” (USFWS, 1998). These data were adjusted in the 1983 recovery plan for the 

kit fox and “a corrected estimate of 6,961 foxes in 1975 was obtained” (USFWS, 1998). 

“When compared to the pre-1930 estimate, this represents a possible population decline 

of 20 to 43 percent. Approximately 85 percent of the fox population in 1975 was found 

in only six counties (Kern, Tulare, Kings, San Luis Obispo, Fresno, and Monterey), and 

over half the population occurred in two of those counties: Kern (41 percent) and San 

Luis Obispo (10 percent)” (USFWS, 1998). 

1.3.1 Critical Habitat (ok) 

No critical habitat for the SJKF has been designated by the USFWS to date. 

1.4 Habitat 

“Historically, San Joaquin kit foxes occurred in several San Joaquin Valley native plant 

communities” (USFWS, 1998 and 2008). However, due to “extensive land conversion 

and intensive land use, some of these communities” “are represented by small, degraded 

remnants today” (USFWS, 1998). “San Joaquin kit foxes occur in 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” (East Contra Costa County HCP/NCCP, 2006). The recovery plan 

states that the plant communities associated with the San Joaquin Kit Fox are grasslands, 

chenopod scrub, alkali sink, subshrub scrub, oak woodland, and agriculture (USFWS, 

1998). “Other plant communities in the San Joaquin Valley providing kit fox habitat 

include Northern Hardpan Vernal Pool, Northern Claypan Vernal Pool, Alkali Meadow, 

and Alkali Playa. These are found as relatively small patches in scattered locations. In 

general, they do not provide good denning habitat for kit foxes because all have moist or 

waterlogged clay or clay-like soils. However, where they are interspersed with more 

suitable kit fox habitats they provide food and cover” (USFWS, 1998). “Kit foxes use 

some types of agricultural land where uncultivated land is maintained, allowing for 

denning sites and a suitable prey base. Kit foxes also den on small parcels of native 

habitat surrounded by intensively maintained agricultural lands and adjacent to dryland 

farms” (USFWS, 1998). “Other habitats in which kit foxes are currently found have been 

extensively modified by humans” (USFWS, 1998). Kit foxes are “found in grassland and 

scrubland communities with active oil fields, wind turbines, and an agricultural matrix of 

row crops, irrigated pasture, orchards, vineyards, and grazed annual grasslands 

(nonirrigated pasture)” (USFWS, 1998 and 2008). 

“In the southernmost portion of the range, the kit fox is commonly associated with Valley 

Sink Scrub, Valley Saltbush Scrub, Upper Sonoran Subshrub Scrub, and Annual 

Grassland” (USFWS, 1998 and 2008). “Kit foxes also inhabit grazed grasslands, 

petroleum fields, urban areas, and survive adjacent to tilled or fallow fields. In the 

central portion of the range, the kit fox is associated with Valley Sink Scrub, Interior 

Coast Range Saltbush Scrub, Upper Sonoran Subshrub Scrub, Annual Grassland and the 

remaining native grasslands. Agriculture dominates this region where kit foxes mostly 

inhabit grazed, nonirrigated grasslands, but also live next to and forage in tilled or fallow 

4
fields, irrigated row crops, orchards, and vineyards. In the northern portion of their 

range, kit foxes commonly are associated with annual grassland and Valley Oak 

Woodland. Kit foxes inhabit grazed grasslands, grasslands with wind turbines, and also 

live adjacent to and forage in tilled and fallow fields, and irrigated row crops” (USFWS, 

1998). 

“San Joaquin kit foxes use dens for temperature regulation, shelter from adverse 

environmental conditions, reproduction, and escape from predators” (USFWS, 1998 and 

2008). “Kit foxes prefer loose textured soils, but are found on virtually every soil type. 

Dens appear to be scarce in areas with shallow soils because of the proximity to bedrock, 

high water tables, or impenetrable hardpan layers. However, kit foxes will occupy soils 

with a high clay content, such as in the Altamont Pass area in Alameda County, where 

they modify burrows dug by other animals” (USFWS, 1998). Kit foxes dig their own 

dens, modify and use those already constructed by other animals (ground squirrels, 

badgers, and coyotes), or use human-made structures (culverts, abandoned pipelines, or 

banks in sumps or roadbeds) (USFWS, 1998 and 2008). “Though kit foxes are reputed to 

be poor diggers, the complexity and depth of their dens do not support this assessment” 

(USFWS, 1998). 

“The majority of their dens lie in relatively flat terrain or gently sloping hills, in washes, 

drainages, and roadside berms” (Cal. EPA. Dept of Pesticide Regulation, 2002). “Dens 

are generally located in open areas with grass or grass and scattered brush, and seldom 

occur in areas with thick brush. Preferred sites are relatively flat, well-drained terrain” 

(East Contra Costa County HCP/NCCP, 2006). “Most hillsides where kit fox dens are 

found (95 percent) have a slope of less than 40 degrees. Natal and pupping dens are 

found on flatter ground with slopes of about 6 degrees” (USFWS, 1998). However, “den 

characteristics vary across the San Joaquin kit fox’s geographic range” (USFWS, 1998). 

“In western Merced County, most dens are found on slopes of less than 10 degrees, but a 

few are found on slopes of up to 55 degrees. In the northern portion of the kit fox range, 

dens appeared to be placed higher than most surrounding ground compared to areas 

farther south, perhaps reflecting the topography of the area. Dens most often are located 

on the lower section of the slope, yet foxes are sometimes seen entering dens on the 

upper part of a slope” (USFWS, 1998). “Kit foxes in the northern range are found in 

higher elevations than those in the southern range” (SJCOG). 

Kit foxes “often change dens and many dens may be used throughout the year” (USFWS, 

1998 and 2008). “Foxes change dens four or five times during the summer months, and 

change natal dens one or two times per month” (USFWS, 1998). “Radiotelemetry studies 

indicate that foxes use individual dens for a median of 2 days (mean of 3.5 days) before 

moving to a different den” (USFWS, 1998). It has been determined that “den use does 

not differentiate between sexes” (East Contra Costa County HCP/NCCP, 2006). 

However, “the number of dens used varied among seasons, with more dens used during 

the dispersal season than during the breeding or pup-rearing seasons” (East Contra Costa 

County HCP/NCCP, 2006). “Den changes have been attributed to depletion of prey in 

the vicinity of the den or to increases in external parasites such as fleas. Avoidance of 

coyotes is a more probably reason for frequently changing dens because kit foxes can 

5
easily search their home range in one night for prey, and parasites are unlikely to build to 

intolerable levels in 2 or 3 days” (USFWS, 1998). 

Core Areas: (ok) 

“Three core populations are: 

1) Carrizo Plain Natural Area in San Luis Obispo County; 

2) Natural lands of western Kern County (i.e., Elk Hills, Buena Vista Hill, and the 

Buena Vista Valley, Lokern Natural Area and adjacent natural land) inhabited by 

kit foxes; and 

3) The Ciervo-Panoche Natural Area of western Fresno and eastern San Benito 

Counties” (USFWS, 1998). 

The Carrizo Plain Natural Area when “combined with land owned by The Nature 

Conservancy, provides more than 200,000 acres of relatively pristine kit fox habitat about 

55 miles west of Bakersfield” (Ridgley, 2007). The second area is “a mosaic of 

disjointed parcels totaling an estimated 300,000 to 500,000 acres” “scattered throughout 

public and private land in western Kern County about 30 miles west of Bakersfield” 

(Ridgley, 2007). This area is “perfect kit fox territory – except for the two hazardous 

waste sites nearby and the miles of oil pipeline that run below the sand” (Ridgley, 2007). 

Kern County is “the third-largest crude oil production area in the country after Alaska 

and Texas” (Ridgley, 2007). However, this area “still supports more foxes than that of 

less-developed land in the county” (Ridgley, 2007). “The Ciervo-Panoche Natural Area 

population is located more than 160 kilometers (100 miles) northwest of the other two 

core populations. As with the other core populations, it has significant numbers of foxes, 

at least it had historically and it still may from time to time” (USFWS, 1998). “Foxes do 

subsist here, but it’s uncertain whether they are really a core population or just a 

‘satellite’ group” (Ridgley, 2007). “Lands farther north, where foxes have also been 

intermittently observed, are even more marginal” (Ridgley, 2007). 

These three core populations are geographically distinct even though they are “more or 

less connected to each other by grazing lands, although they are steep and rugged in 

many places” (USFWS, 1998). “The western Kern County and Carrizo Plain 

populations, although geographically close, are separated by the Temblor Range” 

(USFWS, 1998). “Kit foxes occur at varying densities in the areas between the core 

populations (e.g., Kettleman Hills), providing linkages between the core populations, and 

also probably with smaller, more isolated populations in adjacent valleys” (USFWS, 

1998). “Preliminary population viability analyses indicate that extinction probabilities 

increase dramatically if either it Carrizo Plain or western Kern County population is 

eliminated” (USFWS, 1998). 

“Important kit fox populations in the Salinas-Pajaro Region (herein defined as the area of 

the Salinas River and Pajaro River watersheds with habitat for kit foxes); are located at 

Camp Roberts and Fort Hunter Liggett in the Salinas River Watershed. Though there are 

natural connections between the Salinas-Pajaro Region, the Carrizo Plain Natural Area, 

and the San Joaquin Valley, the amount of movement of kit foxes between the SalinasPajaro Region and these areas is unknown, though one fox is known to have moved from 

6
Camp Roberts to the Carrizo Plain” (USFWS, 1998). Kit foxes can also be found on the 

Lemoore Naval Air Station, as well as on “private lands in western Madera County, 

central, western, and eastern Merced County, eastern Stanislaus County, northern Kings 

County, around Pixley National Wildlife Refuge and Allensworth Ecological Reserve in 

Tulare County, Semitropic Ridge Natural Area and around the Bakersfield metropolitan 

area of Kern County” (USFWS, 1998). In addition, the “California Department of Water 

Resources’s Kern Fan Element provides an important linkage between kit foxes along the 

Kern River Parkway in Bakersfield and the western Kern County core population” 

(USFWS, 1998). 

Activity, Movement, and Behavior: (ok) 

Kit foxes are predominantly nocturnal and “most above-ground activities begin near 

sunset and continue sporadically throughout the night” (USFWS, 1998). However, some 

populations of kit foxes prey on “ground squirrels, which are active during the day” 

indicating that kit foxes are not strictly nocturnal and that they have adapted to the 

activities of their available prey (USFWS, 1998). In addition, kit foxes are “commonly 

seen during the day during late spring and early summer” (USFWS, 1998). They are also 

“active throughout the year” (USFWS, 1998). 

Based on observations at the Elk Hills Naval Petroleum Reserves in California, kit foxes 

move an average of 15.4 kilometers (9.6 miles) nightly during the breeding season which 

is “significantly longer than the average nightly movements of 10.2 kilometers (6.3 

miles) during the pup-rearing season. Movements during the breeding season also were 

significantly longer than those made during the pup-dispersal season (10.4 kilometers, 6.5 

miles)” (USFWS, 1998). 

Kit foxes are a “wide ranging species with established home ranges generally between 1-

3 square miles, but they can be as large as 12 square miles” (SJCOG and USFWS, 1998). 

“Foxes in nonurban areas had larger home ranges than those in urban areas” (Ralls, 

2007). “The maintenance of large and relatively non-overlapping home ranges, as noted 

on the Carrizo Plain, may be an adaptation to drought-induced periods of prey scarcity 

that are episodic and temporary on the Carrizo Plain. Differences in home range size 

among study sites tend to be related to prey abundance” (USFWS, 1998). 

Life History and Ecology (ok) 

Life history and ecology information about the SJKF, including diet, reproduction, and 

disease, competition, and predation are provided in the sections below (1.5.1 through 

1.5.3). 

1.5.1. Diet (ok) 

The diet of the SJKF “varies geographically, seasonally and annually, based on variation 

in abundance of potential prey” (USFWS, 1998). “In the southern part of the range, onethird of the kit fox diet consists of kangaroo rats (Dipodomys spp.), pocket mice 

(Perognathus spp.), white-footed mice (Peromyscus spp.) and other nocturnal rodents. 

Kit foxes in this area also prey on California ground squirrels (Spermophilus beecheyi), 

7
black-tailed hares (Lepus californicus), San Joaquin antelope squirrels 

(Ammospermophilus nelsoni), desert cottontails (Sylvilagus audubonii), ground-nesting 

birds and insects” (USFWS, 1998). “Vegetation and insects occur frequently in feces. 

Grass is the most commonly ingested plant material” (USFWS, 1998). “In the central 

portion of their geographic range, defined here as Kings, Tulare, Fresno, Madera, San 

Benito, Merced, Stanislaus, and Monterey Counties, known prey species include whitefooted mice, insects, California ground squirrels, kangaroo rats, San Joaquin antelope 

squirrels, black-tailed hares, and chukar (Alectoris chukar), listed in approximate 

proportion of occurrence in fecal samples” (USFWS, 1998). “In the northern part of their 

range, defined here as San Joaquin, Alameda and Contra Costa Counties, kit foxes most 

frequently consume California ground squirrels” (USFWS, 1998). Cottontails, blacktailed hares, pocket mice, and kangaroo rats are also eaten” (USFWS, 1998). 

1.5.2. Reproduction (ok) 

Kit foxes can breed when they are one year old, but they may not breed during their first 

year of adulthood (USFWS, 1998 and 2008). “Adult pairs remain together all year, 

sharing the home range but not necessarily the same den. During September and 

October, adult females begin to clean and enlarge natal or pupping dens (they select dens 

with multiple openings). Mating and conception take place between late December and 

March. The median gestation period is estimated to range from 48 to 52 days. Litters of 

from two to six pups are born sometime between February and late March” (USFWS, 

1998 and 2008). “The female is rarely seen hunting during the time she is lactating. 

During this period the male provides most of the food for her and the pups. The pups 

emerge above ground at slightly more than one month of age” (USFWS, 1998 and 2008). 

“After 4 to 5 months, usually in August or September,” the young begin to disperse 

(USFWS, 1998). “Occasionally a juvenile female will remain with the adult female for 

several more months” and “offspring of both sexes sometimes remain with their parents 

through the following year and help raise a subsequent litter” (USFWS, 1998). 

A study of 209 dispersing juveniles published in 2000 found that “33% dispersed from 

their natal territory,” and “significantly more males (49%) than females (24%)” dispersed 

(East Contra Costa County HCP/NCCP, 2006). “Most of the dispersing juveniles (65%) 

died within 10 days of leaving their natal range. However, survival tended to be higher 

for dispersing males than for males that remained within their natal area. There was no 

difference in survival for dispersing and philopatric females” (East Contra Costa County 

HCP/NCCP, 2006). Dispersal distances can vary substantially. “During a 6-year study at 

the Elk Hills Naval Petroleum Reserves in California, pups dispersed an average of 8±1.4 

kilometers (5±0.9 miles)” (USFWS, 1998). “One individual traveled a minimum of 40 

kilometers (25 miles) from its whelping den, and a prime adult male dispersed from 

Camp Roberts to the Carrizo Plan in 1989” (USFWS, 1998). Both adults and juveniles at 

the Elk Hills Naval Petroleum Reserves “dispersed through disturbed habitats, including 

agricultural fields, oil fields, rangelands, and across highways and aqueducts. One pup 

crossed the Temblor Range into the Carrizo Plain” (USFWS, 1998). 

“The annual reproductive success for adults can range between 20 and 100% (mean: 

61%) and 0 and 100% for juveniles (mean: 18%). Population growth rates generally vary 

8
positively with reproductive success and kit fox density is often positively related to both 

current and the previous year’s prey availability. Prey abundance is generally strongly 

related to the previous year’s effective (October to May) precipitation” (East Contra 

Costa County HCP/NCCP, 2006). “The density of prey species drops because of 

drought, too much rainfall, or other circumstances” (USFWS, 1998). “Adults can 

maintain weight and body condition and females can give birth, but pairs apparently 

cannot catch enough prey to support the pups” (USFWS, 1998). Typically the “pups are 

born but do not survive to weaning” (USFWS, 1998). Biologists studying foxes on the 

Naval Petroleum Reserve in Kern County have determined that “the population size of 

these foxes can fluctuate greatly” (Bell, 1995). 

Longevity: (ok) 

In captivity, kit foxes have lived up to 10 years” (USFWS, 1998). “Kit foxes on Naval 

Petroleum Reserve-1 in California are known to live as long as 8 years” and “kit foxes at 

Camp Roberts are reported to be over 8 years old” (USFWS, 1998). However, “such 

longevity is rare” and “animals less than 1 year old outnumber older foxes by 2.8:1” 

(USFWS, 1998). 

The annual adult kit fox mortality rate is approximately 50 percent in nonurban 

populations and “the annual mortality rate for juvenile kit foxes may be close to 70 

percent” (USFWS, 1998 and Ralls, 2007). “In contrast, annual mortality in urban 

Bakersfield, California, is lower (about 30%)” (Ralls, 2007). “Annual survival rates of 

juvenile foxes have ranged from 0.26 on Naval Petroleum Reserve-1 in California to 0.21 

to 0.41 on the Carrizo Plain” (USFWS, 1998). 

1.5.3. Disease, Competition, and Predation (ok)

“The effects of disease, parasites and accidental death are largely unknown, but were 

thought to account for only a small portion of mortality” (USFWS, 1998). Although 

“disease does not appear to be a significant source of mortality,” “rabies could have 

contributed to a decline in one population of the San Joaquin kit fox” (List and Cypher, 

2004). Numbers of SJKF caught during “annual livetrapping sessions at the California 

Army National Guard Training Site, Camp Roberts, decreased from 103 to 20 individuals 

from 1988 to 1991. This decrease continued through 1997 when only three kit foxes 

were captured” (White et al., 2000). “An outbreak of rabies virus may have contributed 

to this catastrophic decrease in abundance because two foxes were found dead due to 

rabies in 1990” (White et al., 2000). The recovery plan also states that “at Camp Roberts 

rabies accounted for 6.3 percent of deaths of radio-collared kit foxes and there is concern 

that rabies may be a contributing factor in the recent decline of kit foxes at Camp 

Roberts” (USFWS, 1998). “Interference competition by coyotes (Canis latrans) also 

may have contributed to this catastrophic decrease because relative abundances of foxes 

and coyotes were negatively correlated from 1988 to 1997, and coyotes were responsible 

for 59% of fox deaths during a 4-year telemetry study (1988 to 1991)” (White et al., 

2000). 

“Kit foxes are subject to competitive exclusion or predation by other species, such as the 

nonnative red fox (Vulpes vulpes), coyote (Canis latrans), domestic dog (Canis 

9
familiaris), bobcat (Felis rufus), and large raptors” (USFWS, 1998 and 2008). “Predation 

by larger carnivores (e.g., coyotes) accounts for the majority of San Joaquin kit fox 

mortality” particularly in nonurban areas (USFWS, 1998 and Ralls, 2007). In urban 

Bakersfield, California “motor vehicles are the major cause of death. No sex or seasonal 

differences in vulnerability to predation are known” (Ralls, 2007). However, higher 

proportions of juvenile kit foxes are typically killed by coyotes at higher fox densities 

(East Contra Costa County HCP/NCCP, 2006). “The mortality rates of adult foxes are 

apparently independent of population density” (East Contra Costa County HCP/NCCP, 

2006). “Coyotes are known to kill kit foxes, though an experimental coyote-control 

program at the Elk Hills Naval Petroleum Reserves in California did not result in an 

increase in survival rates for kit foxes, nor did coyote-induced mortality decrease” 

(USFWS, 1998). 

Nonnative red foxes and kit foxes are likely to be in direct competition with each other 

for similar den sites and prey species (USFWS, 1998). “Nonnative red foxes are 

expanding their geographic range in central California, 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” (USFWS, 1998). 

“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 on red foxes into kit fox 

habitats are unknown” (USFWS, 1998). 

1.6 References 

Bell, H. 1995. San Joaquin Kit Fox. Tideline. Vol. 15 No. 3 1-3. Available online at: 

http://www.fws.gov/desfbay/Archives/Fox/KitFox.htm (Accessed on October 3, 2007). 

Cal EPA. Dept. of Pesticide Regulation. 2002. San Joaquin Kit Fox (Vulpes macrotis 

mutica). Available online at: http://www.cdpr.ca.gov/docs/endspec/espdfs/sjkfall.pdf

(Accessed on April 4, 2008). 

East Contra Costa County HCP/NCCP. 2006. San Joaquin Kit Fox (Vulpes macrotus 

mutica). Available online at: http://www.co.contracosta.ca.us/depart/cd/water/HCP/archive/hcp_nccp_content/hcp_nccp/app_figs/App%20

D%20components/App_D-02a_San_Joaquin_kit_fox_profile_1-18-05.pdf (Accessed on 

April 3, 2008). 

List, R. and B.L. Cypher. 2004. Kit fox (Vulpes macrotis). Pages 105-109 in C. SilleroZubiri, M. Hoffmann, D. W. Mac Donald, editors. Canids: Foxes, Wolves, Jackals and 

Dogs. Status Survey and Conservation Action Plan. Cambridge, UK: IUCN/SSC Canid 

Specialist Group. Available online at: http://www.canids.org/species/Kit_fox.pdf

(Accessed on April 4, 2008). 

Ralls, K. B. Cypher, and L.K. Spiegel. 2007. Social monogamy in kit foxes: formation, 

association, duration, and dissolution of mated pairs. Journal of Mammalogy 88(6):1439-

10
11

1446. Available online at: http://www.bioone.org/archive/1545-1542/88/6/pdf/i1545-

1542-88-6-1439.pdf (Accessed on April 3, 2008). 

Ridgley, H. 2007. Foxy City. Defenders Magazine. Defenders of Wildlife. Available 

online at: 

http://www.defenders.org/newsroom/defenders_magazine/fall_2007/foxy_city.php

(Accessed on April 3, 2008). 

San Joaquin County Multi-Species Habitat Conservation and Open Space Plan (SJCOG) 

Available online at: 

http://www.sjcog.org/Programs%20&%20Projects/Habitat_files/Species/San%20Joaquin

%20Kit%20Fox.pdf (Accessed on April 3, 2008) 

U.S. Fish and Wildlife Service (USFWS). 1967. Native Fish and Wildlife, Endangered 

Species. Washington, D.C. Available online at: 

http://ecos.fws.gov/docs/federal_register/fr18.pdf (Accessed on April 16, 2008). 

U.S. Fish and Wildlife Service (USFWS). 1998. Recovery Plan for Upland Species of 

the San Joaquin Valley, California. U.S. Fish and Wildlife Service, Portland, Oregon. 319 

pages. Available online at: http://ecos.fws.gov/docs/recovery_plans/1998/980930a.pdf

(Accessed on March 31, 2008). 

U.S. Fish and Wildlife Service (USFWS). 2008. Species Account: San Joaquin Kit Fox 

(Vulpes macrotis mutica). Sacramento Fish and Wildlife Office. Available online at: 

http://www.fws.gov/sacramento/es/animal_spp_acct/sj_kit_fox.htm

(Accessed on March 31, 2008). 

White, P. J., W. H. Berry, J. J. Eliason, and M. T. Hanson. 2000. Catastrophic decrease 

in an isolated population of kit foxes. Southwestern Naturalist 45(2):204–211. (Only the 

abstract was viewed and used). Available online at: http://www.jstor.org/pss/3672462

(Accessed on April 3, 2008).