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Vulpes macrotiskit fox

By Allen Patton

Geographic Range

Kit foxes are primarily found in the southwestern part of the United States and northern and central Mexico. They are found as far north as the arid interior of Oregon, east to southwestern Colorado, south through Nevada, Utah, southeastern California, Arizona, New Mexico, and into western Texas. In Mexico they are found mainly in the states of Coahuila, Chihuahua, and Nuevo Leon, and throughout Baja California. ("Kit Fox (Vulpes macrotis): A Technical Conservation Assessment", 2006; List and Cypher, 2005)

Habitat

Kit foxes are primarily found in arid regions, such as desert scrub, chaparral, and grasslands. Vegetation communities vary with the regional aridland fauna, but some examples of common habitats are saltbrush Atriplex polycarpa and sagebrush Artemisia tridentata. Kit foxes may also occur in agricultural areas and urban environments. They occur at elevations of 400 to 1900 meters. Kit foxes prefer areas with loose soils for constructing dens. They spend most of their time in dens that they dig themselves or take over from prairie dogs (Cynomys), other rodents, and American badgers (Taxidea taxus). Kit foxes occupy dens year-round and have several dens in their territory that they rotate among. Dens could have one or many entrances and are usually covered by thick brush. They usually stay in their dens during the daytime, exiting to hunt for food at night. ("Kit Fox (Vulpes macrotis)", 1993; "Kit Fox (Vulpes macrotis): A Technical Conservation Assessment", 2006; List and Cypher, 2005)

  • Range elevation
    400 to 1900 m
    1312.34 to 6233.60 ft

Physical Description

Kit foxes are the smallest member of the family Canidae in North America. Their most distinctive feature is their exceptionally large ears placed close together on the head. The ears are from 71 to 95 mm in height and they play a role in dissipating heat and the excellent hearing of kit foxes. ("Kit Fox (Vulpes macrotis)", 1993; List and Cypher, 2005)

Kit foxes range in color from yellowish to gray. They usually have a dark-colored back, light-colored undersides and inner ears, and distinct dark patches on each side of the nose and at the end of the tail. Males average slightly larger than females. Head and body length is from 485 to 520 mm in males (average 537) and from 455 to 535 mm in females (average 501). The tail is from 250 to 340 mm long. Males average 2.29 kg and females 1.9 kg, ranging from 1.6 to 2.7 kg. ("Kit Fox (Vulpes macrotis)", 1993; List and Cypher, 2005)

  • Sexual Dimorphism
  • male larger
  • Range mass
    1.6 to 2.7 kg
    3.52 to 5.95 lb
  • Range length
    455 to 535 mm
    17.91 to 21.06 in

Reproduction

Most studies have shown kit foxes to be monogamous, with pairs mating for life. Occasional polygyny has also been reported. When the female is ready to reproduce, she goes out on her own in search of a den. This usually happens around the month of September. In October, the male kit fox will join her and remain with her until the end of the breeding season. Female young will sometimes delay dispersal and stay an additional year beyond their independence to help raise their siblings. ("Kit Fox (Vulpes macrotis): A Technical Conservation Assessment", 2006; List and Cypher, 2005)

Kit foxes mate once per year from mid-December to February. The typical gestation period is 49 to 55 days, and they can produce a litter of 1 to 7 pups, with an average of 4. Births occus from February to mid-March. Although females are able to breed 10 months after birth, many females do not reproduce that first year. Young females are much lower reproductive success than do older females. ("Kit Fox (Vulpes macrotis)", 1993; "Kit Fox (Vulpes macrotis): A Technical Conservation Assessment", 2006; List and Cypher, 2005)

  • Breeding interval
    Kit foxes breed once yearly.
  • Breeding season
    Breeding occurs from December to February.
  • Range number of offspring
    1 to 7
  • Range gestation period
    49 to 55 days
  • Average weaning age
    8 weeks
  • Range time to independence
    5 to 6 months
  • Range age at sexual or reproductive maturity (female)
    10 (low) months
  • Range age at sexual or reproductive maturity (male)
    10 (low) months

Young stay in their birth den until they are 4 weeks old and are weaned at 8 weeks old. The young begin to hunt with their parents at 3 to 4 months old and are independent at 5 to 6 months old. Most young disperse by 8 months old. Both male and female parents care for and protect their young. ("Kit Fox (Vulpes macrotis): A Technical Conservation Assessment", 2006; List and Cypher, 2005)

  • Parental Investment
  • altricial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • male
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • male
      • female
  • post-independence association with parents
  • extended period of juvenile learning

Lifespan/Longevity

Vulpes macrotis survival rates are dependent on food availability, reproduction, and local predators. Different studies have estimated different life expectancies for kit foxes. Some report lifespans of 3 to 4 years, while others reported 7 to 12 years. In California a study of 144 kit fox pups showed a 74% mortality rate in pups within the first year. ("Kit Fox (Vulpes macrotis): A Technical Conservation Assessment", 2006)

  • Range lifespan
    Status: wild
    7 (high) years
  • Range lifespan
    Status: captivity
    12 (high) years
  • Average lifespan
    Status: wild
    5.5 years

Behavior

Kit foxes remain relatively inactive during hot desert days, remaining in their dens. They are primarily nocturnal but occasionally are crepuscular as well. Kit foxes forage alone. Kit foxes are not exceptionally territorial, preferring to live in underground burrows in pairs or small family groups. Territories of neighboring family groups can overlap. Females are thought to be relatively sedentary, males seem to disperse more widely. ("Kit Fox (Vulpes macrotis)", 1993; Arjo, et al., 2003; List and Cypher, 2005)

  • Range territory size
    2.5 to 11.6 km^2
  • Average territory size
    3.22 km^2

Home Range

Home range size of Vulpes macrotis is typically 3.22 square kilometers, in which up to 3 individuals may inhabit. Home range sizes vary from 2.4 to 11.6 square kilometers. ("Kit Fox (Vulpes macrotis)", 1993; Koopman, et al., 2000; List and Cypher, 2005; McCue and O'Farrell, 1992)

Communication and Perception

Kit foxes have very large ears and excellent hearing. Kit foxes sometimes bark at perceived threats or use a "hacking growl" in intraspecific encounters. ("Kit Fox (Vulpes macrotis)", 1993; "Kit Fox (Vulpes macrotis): A Technical Conservation Assessment", 2006; Ralls and White, 2003)

Food Habits

Kit foxes eat primarily rodents and rabbits. Species preyed on varies regionally, but the most common prey are prairie dogs (Cynomys species), kangaroo rats (Dipodomys species), black-tailed jackrabbits (Lepus californicus), and cottontail rabbits (Sylvilagus species). Kit foxes are primarily carnivores, but if food is scarce, they have been reported to eat tomatoes (Lycopersicon esculentum), cactus fruits (Carnegiea gigantea), and other available fruits. They also will scavenge carrion and eat large insects, lizards, snakes, and ground-dwelling birds. ("Kit Fox (Vulpes macrotis): A Technical Conservation Assessment", 2006; George Jr., 1990; Couper, et al., 1989; List and Cypher, 2005)

Kit foxes may compete for food and dens with coyotes (Canis latrans), bobcats (Lynx rufus), red foxes (Vulpes vulpes), and American badgers (Taxidea taxus). (List and Cypher, 2005)

  • Primary Diet
  • carnivore
    • eats terrestrial vertebrates
  • Animal Foods
  • birds
  • mammals
  • reptiles
  • carrion
  • insects
  • Plant Foods
  • fruit

Predation

Predation by coyotes (Canis latrans) accounts for over 75% of kit fox predation. Other predators include bobcats (Lynx rufus), red foxes (Vulpes vulpes), American badgers (Taxidea taxus), feral dogs (Canis lupus familiaris), and large raptors (Accipitridae). Also kit fox deaths have been due to interactions with humans, such as illegal hunting and trapping for fur. Kit foxes are also hit by cars. Kit foxes are wary and nocturnal, with cryptic coloration, reducing their risk of predation. ("Mortality of San Joquin Kit Fox (Vulpes velox macrotis) at Camp Roberts Army National Guard Training Site, California", 1992)

  • Anti-predator Adaptations
  • cryptic

Ecosystem Roles

Kit foxes are prey for other carnivores such as coyotes (Canis latrans) and bobcats (Lynx rufus). Also kit foxes are predators of rodents or other small animals, including black-tailed jackrabbits (Lepus californicus), kangaroo rats (Dipodomys), and prairie dogs (Cynomys). Because kit foxes move from den to den in search of a mate and food, their old dens are taken over by other kit foxes or other animals. As scavengers, kit foxes also play a major role in biodegradation. ("Kit Fox (Vulpes macrotis)", 1993; "Kit Fox (Vulpes macrotis): A Technical Conservation Assessment", 2006; "Mortality of San Joquin Kit Fox (Vulpes velox macrotis) at Camp Roberts Army National Guard Training Site, California", 1992; Egoscue, 1956; Harrison, et al., 2002; Voge, 1955; Wilson and Bishop, 1966)

Fleas, such as Pulex irritans and Pulex simulans, are common parasites of this species. Ticks are also common and include Ixodes texanus and Dermacentor perumapertus. Other cestode parasites include Mesocestoides corti, Mesogyna hypatica, and Dipylidium caninum. Unidentified roundworms and tapeworms have been noted from scat collections.

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Kit foxes are important members of native ecosystems, helping to control rodent populations through predation. ("Kit Fox (Vulpes macrotis): A Technical Conservation Assessment", 2006)

  • Positive Impacts
  • research and education
  • controls pest population

Economic Importance for Humans: Negative

Kit foxes can have a negative impact on humans by carrying diseases. The main disease of concern is plague, which foxes contract from fleas. (Harrison, et al., 2002)

Conservation Status

Kit foxes are listed as "Least Concern" on the IUCN red list of threatened species. Populations throughout most of the United States are estimated to be stable. San Joaquin kit foxes, V. macrotis mutica, are considered endangered in the United States, as their habitat continues to be fragmented and lost to agriculture. Kit foxes are listed as species of concern in some states, including Colorado and Utah, where programs exist that are designed to protect kit fox populations. They are considered state threatened in California and state endangered in Oregon. In Mexico it is likely that kit fox populations are in decline as 40% of prairie dog populations have been converted to agriculture since 1994. Kit foxes are considered "vulnerable" in Mexico. ("Kit Fox (Vulpes macrotis)", 1993)

Other Comments

Biologists sometimes gather information on the overall health of kit foxes Vulpes macrotis by gathering serum chemistry values. (Koopman, et al., 2000; McCue and O'Farrell, 1992)

Other common names include: desert fox, zorra del desierto, zorra norteña (Spanish), and wüstenfuchs (German). (List and Cypher, 2005)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Allen Patton (author), Radford University, Karen Powers (editor, instructor), Radford University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

acoustic

uses sound to communicate

agricultural

living in landscapes dominated by human agriculture.

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

biodegradation

helps break down and decompose dead plants and/or animals

carnivore

an animal that mainly eats meat

carrion

flesh of dead animals.

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal

chaparral

Found in coastal areas between 30 and 40 degrees latitude, in areas with a Mediterranean climate. Vegetation is dominated by stands of dense, spiny shrubs with tough (hard or waxy) evergreen leaves. May be maintained by periodic fire. In South America it includes the scrub ecotone between forest and paramo.

chemical

uses smells or other chemicals to communicate

cooperative breeder

helpers provide assistance in raising young that are not their own

crepuscular

active at dawn and dusk

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

fertilization

union of egg and spermatozoan

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

polygynous

having more than one female as a mate at one time

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

solitary

lives alone

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

urban

living in cities and large towns, landscapes dominated by human structures and activity.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

References

Utah State University Wildlife Management: Jensen E., Poulsen C., Rogers M., Messmer Dr. T.. Kit Fox (Vulpes macrotis). Wildlife Notebook Series No. 9. Logan, Utah: Department of Fisheries and Wildlife. 1993.

Denver Museum of Nature and Science and Meaney & Company, Bear Canyon Consulting, Wyoming Natural Diversity Database: Meaney Dr. C. A., Reed-Eckert M., Beauvais Dr. G. P.. Kit Fox (Vulpes macrotis): A Technical Conservation Assessment. DE-AC08-88NV10617. Rocky Mountain Region: USDA Forest Service, Rocky Mountain Region, Species Conservation Project. 2006.

U.S. Departments of the Army and Air Force National Guard Bureau. Mortality of San Joquin Kit Fox (Vulpes velox macrotis) at Camp Roberts Army National Guard Training Site, California. DE-AC08-88NV10617. Nevada Field Office: U.S. Department of Energy. 1992.

Arjo, W., T. Bennett, A. Kozlowski. 2003. Characteristics of current and historical kit fox (Vulpes macrotis) dens in the Great Basin Desert. Canadian Journal of Zoology, 81: 96-102.

Couper, H., D. Dixon, D. Fuller, J. Garlick, J. Griffiths, N. Henbest, B. Jones, R. Kerrod, A. Lyons, R. Matthews, R. Mills, Z. Vrbova. 1989. Deserts. Pp. "98" in R Kerrod, ed. The Plant World, Vol. 5, First Edition. Chicago: Bull Publishing.

Egoscue, H. 1956. Preliminary Studies of the Kit Fox in Utah. Journal of Mammalogy, 37/3: 351-357.

George Jr., W. 1990. Tomato. Pp. "325-326" in S Fetzer Company, ed. The World Book Encyclopedia, Vol. 19, First Edition. Chicago London Sydney Toronto: Scott Fetzer Company.

Haight, R., B. Cypher, P. Kelly, S. Phillips, K. Ralls, H. Possingham. 2004. Optimizing Reserve Expansion for Disjunct Populations of San Joaquin Kit Fox. Biological Conservation, 117: "61-72".

Harrison, R., M. Patrick, C. Schmitt. 2002. Foxes, Fleas, and Plague in New Mexico. The Southwestern Naturalist, 48/4: "720-728".

Koopman, M., B. Cypher, J. Scrivner. 2000. Dispersal Patterns of San Joaquin Kit Foxes (Vulpes macrotis mutica). Journal of Mammalogy, 81/1: "213-222".

List, R., B. Cypher. 2005. "Vulpes macrotis (kit fox)" (On-line). IUCN Canid Specialist Group. Accessed April 05, 2008 at http://www.canids.org/species/Vulpes_macrotis.htm.

McCue, P., T. O'Farrell. 1992. Serum Chemistry Values of the Endangered San Joaquin Kit Fox (Vulpes macrotis mutica). Journal of Wildlife Diseases, 28/3: 414-418.

Ralls, K., P. White. 2003. Diurnal Spacing Patterns in Kit Foxes, a Monogamous Canid. The Southwestern Naturalist, 48/3: "432-436".

Smith, D., K. Ralls, B. Cypher, H. Clark, Jr., P. Kelly, D. Williams, J. Maldonado. 2006. Relative Abundance of Endangered San Joaquin Kit Foxes (Vulpes macrotis mutica) Based on Scat-Detection Dog Surveys. The Southwestern Naturalist, 51/2: "210-219".

Voge, M. 1955. A List of Cestode Parasites From California Mammals. American Midland Naturalist, 54/2: 413-417.

Wilson, N., P. Bishop. 1966. A New Host and Range Extensino for Pulex simulans Baker with a Summary of Published Records (Siphonaptera: Pulicidae). American Midland Naturalist, 75/1: 245-248.

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