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Urocyon littoralisisland gray fox

By Sonia Liu

Geographic Range

Urocyon littoralis, the island grey fox, can be found on the six largest Channel islands, about 30 to 98 kilometers off of the southern California coast in North America. These islands are Santa Catalina, San Clemente, San Nicholas, San Miguel, Santa Cruz, and Santa Rosa Islands.

(Claybourne & Collins 1995, Wayne et al. 1991, Chapman 1999, Schmeckpepper 1999)

Habitat

Channel island foxes can be found in all types on habitats of the Channel islands. This includes valley and foothill grasslands, coastal sage/scrub, coastal bluff, sand dune areas, island chapparral, southern coastal oak woodland, island woodland, southern riparian woodland, pine forests, and coastal marshes.

(Claybourne & Collins 1995, Fritzell et al. 1999)

Physical Description

Island grey foxes resemble dwarf versions of the grey fox (Urocyon cinereoargenteus). This is the smallest fox species known from the United States. Adult males weigh 2.00 kilograms on average, while adult females weigh 1.88 kilograms. Body length, including head and tail, ranges from 59 to 79 centimeters. Tail length alone ranges from 11 to 29 centimeters. Height at the shoulder is from 12 to 15 centimeters.

Fur is greyish-white and black with cinnamon underfur on the dorsal side, and with pale white, yellow, and rusty-brown on the ventral surface. The chin, lips, nose, and areas around the eyes are lined in black while the sides of the rostrum are grey. The ears, neck, and sides of the limbs are cinnamon-colored. The tail has a contrasting thin black stripe on the dorsal side with a mane of stiff hairs. The underside of the tail is a rusty color. Fur color may differ among islands and be highly variable among individuals, ranging from overall greyish to honey brown and red. Island grey foxes molt once a year during the fall months from August to November. At that time, the fur coat fades in color and the fur tips curl at the ends.

Young foxes tend to have a paler but thicker dorsal fur coat compared to adults. In addition, the ears are darker in color compared to adult foxes.

(Claybourne & Collins 1995, Crooks 1994, Chapman 1999, Schmeckpepper 1999, Weston date unknown, Fritzell et al. 1999)

  • Sexual Dimorphism
  • male larger
  • Range mass
    1 to 2 kg
    2.20 to 4.41 lb

Reproduction

Since there is little sexual dimorphism and relatively equal sex ratios in population, it is suggested that this species forms monogamous bonds.

Mating season of island grey foxes occurs from January to April, depending on latitude.

After mating, female foxes give birth to a litter of kits in 50 to 63 days. Although average litter size is 2 to 3 kits, it can range from 1 to 5 kits.

These kits are born in dens. Dens include ground holes, hollow trees, rock piles, shrubs, caves, and man-made structures. These dens are usually found, not made by the fox. However, if the fox is unable to find an appropriate den, she will dig a hole in the ground. The den serves to protect the kits from harsh weather, predators, and other dangers.

Kits are born blind, weighing approximately 100 grams. They reach adult weight by their first winter. They depend on their mother for milk during the first 7 to 9 weeks. Around May to June, after being weaned, they emerge from their dens and forage for food with their parents. Both parents take care of the kits. An interesting observation is that when both parents and kits are caught in traps while foraging, the parents still care for the kits and provide food to them.

Fox kits remain with their parents during the summer but become independent by September. Young foxes usually stay around the den area while the parents disperse from it. They reach sexual maturity at about 10 months old. Island foxes are able to breed after one year of age.

(Claybourne & Collins 1995, Crooks 1994, Crooks & Van Vuren 1996, Garcelon et al. 1999, Nowak 1999, Chapman 1999, Schmeckpepper 1999, Weston date unknown, Fritzell et al. 1999)

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Range number of offspring
    1 to 5
  • Average number of offspring
    2.5
  • Average number of offspring
    2.6
    AnAge
  • Range gestation period
    50 to 63 days
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    365 days
    AnAge
  • Parental Investment
  • altricial
  • extended period of juvenile learning

Behavior

Urocyon littoralis live a solitary diurnal lifestyle. The range of male Channel Island foxes varies throughout the seasons more so than that of the females. The range covered by a fox overlaps somewhat with that of neighboring foxes and has an area of 0.5 to 1 square mile. Their territories are marked by urine and feces left on conspicuous land features. They are known to be good tree climbers. Neighboring foxes usually include the mate. Mates share mutual grooming at times.

Channel Island foxes are mostly nocturnal, but are also seen during the daytime. During the night, they can be heard barking. They communicate with each other through various vocalizations, body language, olfactory signals, and visual signals. These signs can express dominance as well as submissiveness. Submissiveness can be expressed through lowering the head, flattening of the ears, whining, licking, and lack of eye contact.

This species is known to be docile, affectionate, playful, and curious. They do not fear humans since they have not suffered from human activities. They may show aggressive behavior when first approached by a human, but soon after capture they are submissive.

(Claybourne & Collins 1995, Crooks & Van Vuren 1996, Nowak 1999, Chapman 1999, Schmeckpepper 1999, Weston date unknown)

Communication and Perception

Food Habits

Island grey foxes are omnivorous, with a diet consisting mostly of insects and fruits. Their diet depends on seasonal and regional abundance of food items. Fruits and berries include manzanita, toyon, saltbush, prickly pear cactus, ice plant, and the fruits of sea-figs. They also feed on deer mice and birds. Sometimes these foxes feed on reptiles such as lizards, amphibians, land snails, and human refuse, but not as frequently since these items are not as abundant on the islands. In addition, they are known to scavenge for food on beaches along the coastline.

(Claybourne & Collins 1995, Garcelon et al. 1999, Chapman 1999, Schmeckpepper 1999, Weston date unknown)

  • Animal Foods
  • birds
  • mammals
  • amphibians
  • reptiles
  • insects
  • mollusks
  • Plant Foods
  • fruit

Economic Importance for Humans: Positive

Native Americans used the Channel island fox for many purposes. Their fur was used for arrow-quivers, capes, blankets, and headdresses for ceremonial dances. Since they are docile in nature, they were also kept as pets. Native Americans used the island fox in their religious and ceremonial practices. They served as totems, dream-helpers, and legendary characters. Native Americans also had burials for these foxes, suggesting they were of religious importance.

Today, Urocyon littoralis are sometimes hunted.

(Collins 1991, Nowak 1999)

Conservation Status

Urocyon littoralis is classified as "rare/lower risk" by the IUCN and "threatened" by the State of California and is protected by the California state law. There are no more than 1,000 foxes on each island and as few as 40 foxes on the smaller islands. Since their genetic variation is low, they are susceptible to disease and the consequences of environmental changes caused by man.

In 1993, their population was monitored by park biologists on San Miguel Island. This research revealed that this population of island foxes dropped from 450 in 1994 to less than 40 today. Similar outcomes are shown on the other islands. Populations on some islands have dropped as much as 90% in the past four years. This has sparked the park biologists to start a conservation team consisting of island fox researchers, captive breeding experts, canid genetics, wildlife disease experts, veterinarians, other canid biologists, and golden eagle researchers.

Threats to the island fox include loss of habitat, habitat changes resulting from the introduction of new herbivores, competition with feral cats, diseases brought by domestic dogs, and car accidents.

Measures and programs taken into effect to protect the island fox include disease investigations, elimination of feral cats, and potential captive breeding programs. The U.S. Navy and U.S. Park Service occupy their islands in order to help protect them. This species is currently a candidate for the U.S. ESA to be classified as threatened or endangered. It is already considered endangered by the State of California. Enforcing such protection is difficult, however, because they live on small remote islands.

(Nowak 1999, Chapman 1999, Schmeckpepper 1999, Weston date unknown, Fritzell et al. 1999, IUCN 1999, Wilson and Reeder 1993, National Park Service 1999)

Other Comments

Urocyon littoralis was originally named Vulpes littoralis in 1857. Other common names for the island fox include coast fox, short-tailed fox, island gray fox, channel island fox, channel islands gray fox, California channel island fox, and insular gray fox. Some researchers considered Urocyon littoralis to be a conspecific or even a subspecies of Urocyon cinereoargenteus. However, full biological and historical analysis and genetic reports indicate that this species is distinct.

Predators of the island fox include man, common ravens, golden eagles, and bald eagles. Its average life span is 4 to 6 years, but some individuals may live to be 15 years old.

How these foxes came to inhabit these islands still remains in question. The island fox arrived at the northern islands (San Miguel, Santa Rosa, and Santa Cruz) about 10,400-16,000 years ago and then later spread out to the southern islands (San Nicholas, Santa Catalina, and San Clemente) about 2,200-4,300 years ago. It may have migrated to the northern island of Santa Rosa from mainland California by either rafting on natural debris or by swimming. The island was only 5.5 miles away from the coastline during a time of high glaciers and low sea levels. However, it is still unknown whether these ancestors were strong enough to swim this distance. This island later formed the present day northern Channel Islands as the rising sea level had flood the island into three smaller islands.

The history of the island fox inhabiting the southern Channel Islands is another mystery. It is theorized that they were brought over by Native Americans for the purpose of fur, pets, and religious ceremonies

(Claybourne & Collins 1995, Nowak 1999, Chapman 1999, Schmeckpepper 1999, Weston date unknown, Wilson and Reeder 1993)

Contributors

Sonia Liu (author), University of Michigan-Ann Arbor, Phil Myers (editor), Museum of Zoology, University of Michigan-Ann Arbor.

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

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.

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

diurnal
  1. active during the day, 2. lasting for one day.
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.

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

island endemic

animals that live only on an island or set of islands.

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

omnivore

an animal that mainly eats all kinds of things, including plants and animals

sexual

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

solitary

lives alone

tactile

uses touch to communicate

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

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.

References

1999. "IUCN- The World Conservation Union" (On-line). Accessed November 28, 1999 at http://www.iucn.org/.

1999. "National Park Service to Convene Island Fox Recovery Team" (On-line). Accessed November 28, 1999 at http://www.nps.gov/chis/press3.htm.

Chapman, J. 1999. "Santa Catalina Island Fox- Jeff Chapman" (On-line). Accessed November 28, 1999 at http://www.catalinaconservancy.org/animals/mammals/foxjchap.htm.

Collins, P. 1991. Interaction between island foxes (Urocyon-littoralis) and Native Americans on islands off the coast of southern California. Journal of Ethnobiology, 11(2): 205-229.

Crooks, K., D. Van Vuren. 1996. Spatial organization of the island fox (Urocyon littoralis) on Santa Crus Island, California. Journal of Mammalogy, 77(3): 801-806.

Crooks, K. 1994. Demography and status of the island fox and the island spotted skunk on Santa Cruz Island, California. Southwestern Naturalist, 39(3): 257-262.

Fritzell, E., T. Fuller, D. Garcelon. 1999. "Island Grey Fox (Urocyon littoralis)" (On-line). Accessed November 28, 1999 at http://users.ox.ac.uk/~wcruinfo/csgweb/sppaccts/ulittoral.htm.

Garcelon, D., G. Roemer, R. Philips, T. Coonan. 1999. Food provisioning by island foxes, Urocyon littoralis, to conspecifics caught in traps. Southwestern Naturalist, 44(1): 83-86.

Moore, C., P. Collins. 1995. Urocyon Littoralis. Mammalian Species (489: 1-7). The American Society of Mammalogists.

Nowak, R. 1999. Walker's Mammals of the World. Baltimore: Johns Hopkins University Press.

Schmeckpepper, D. 1999. "Native Mammals- Catalina Island Fox" (On-line). Accessed November 28, 1999 at http://www.catalinaconservancy.org/animals/mammals/uroclitt.htm.

Wayne, R., S. George, D. Gilbert, P. Collins, D. Girman. 1991. A Morphologic and Genetic Study of the Island Fox Urocyon-littoralis. Evolution, 8: 1849-1868.

Weston, J. "Island Fox- Utah's Hogle Zoo" (On-line). Accessed November 28, 1999 at http://www.hoglezoo.org/mammals/fox.htm.

Wilson, D., D. Reeder. 1993. "Mammals Species of the World" (On-line). Accessed November 28, 1999 at http://nmnhwww.si.edu/cgi-bin/wdb/msw/names/query/12057.

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