The Biogeography of Channel Island Fox (Urocyon littoralis)
 

by Virginia Chao, student in Geography 316

Thank you for visiting our site. This web pages was written by a student in Geography 316: Biogeography and edited by the instructor, Barbara Holzman, PhD.  All photos and maps are posted with specific copyright permission for the express use of education on these web pages. The students have tried to be as accurate as possible with the information provided and sources and references are cited at the end of each page.

Species Name:Urocyon littoralis

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora                               
Family: Canidae
Genus: Urocyon
Species: Urocyon littoralis
                                                                                            

                                                                                                                                                                                                                                                                                                                                                                                                         Fig. 1. Channel Island Fox                                                  

                                                                                   Source: National Park Service, 1999.

Description of Species:

                                                                                                                                                                                                                                                                                The Latin word for littoralis means "situated or growing on or near a shore" (National Park Service, 1999).

          In 1971 the Channel Island fox was listed as a California Endangered Species (Fig. 1). The Channel Island fox is the largest of the native terrestrial mammals found on any of the six larger Channel Islands (National Park Service, 1999). The Channel Island fox is smaller than the average house cat but is built to be sturdier and weighs around 2-5 pounds (Baird, 1974). Its small body resembles the dwarf version of the grey fox, Urocyon cineroargenteus, and is only two-thirds of the size of their mainland relative (Fig. 2). The average height is about 12-13 inches and about 23-31 inches long not including its tail which adds another 4.5-11.5 inches (National Park Service, 1999). The Channel Island fox is one of the smallest fox found in the US, with the smallest found in San Clemente, which weighing approximately 1.8 kg.                                                          [FrontPage Image Map Component]     

         The Channel Island foxes are separated into six different subspecies, one on each of the six larger islands. The island foxes can still interbreed together but there are enough differences in physical and genetic makeup to distinguish the population as subspecies (National Park Service, 1999). The smaller size can be contributed to the environment, such as drought and scarcity of food which can limit the growth of the species (National Park Service, 1999).

          The island species is distinctive from the mainland species. Even though both species are known for their large ears and bushy tail, the island species has distinctly different types of fur. Comparatively the island fox's fur is more faded compared to the                           Fig. 2. Channel Island Fox                     grey fox. The Channel Island fox has fur that is grayish white with cinnamon or buff                          Source: National Park Service, 1999.                  under fur covering the back, ears and side limbs. The foxes lower face and throat is                                                                                            white, and has a contrasting narrow black stripe from head to tail. The areas surrounding the eyes, lip, nose and chin are lined in black. All these color markings gives the island gray fox the salt and pepper look. Depending on the islands subspecies, there are variation to the shades of fur; ranging from grayish to brownish-red. Hence another similarity to its common ancestor with the mainland gray fox. Once a year, the island fox will molt and the result is a faded fur color. Younger foxes have thicker but darker fur coats (National Park Service, 1999) (Fig. 3).

          The Channel Island fox is smaller than the mainland gray fox and with a shorter tail. The average tail vertebrae of an island fox ranges from 15 to 22, unlike the gray fox with 21 to 22 (Moore & Collins, 1995). Another difference between the two species is that the ears of the island fox are bushy and hairy, just like the tail and unlike the gray fox with rusty hairs, the Channel Island fox fur is usually softer and fuller looking (Baird, 1974).
 

Fig. 3. Channel Island Fox (Baby)   
Source: National Park Service, 1999.                                                               

Natural History:                                                                                                                                                                                                 

            The California Islands are found along the west coast of California, from approximately 38 to 27.5 degrees north latitude (Power, 1989).  Since the islands are distributed along the edge of the continent, they are classified as "fringing islands" (Power, 1989). All islands that contain Channel Island foxes are made up of submarine canyons and ridges. The California Islands are diverse in the distance from the mainland, topography and size (Power, 1989).

            These islands are separated by water barriers that are 5 to 40 km wide. Within eight of the islands, the six subspecies (Urocyon littoralis) of the island gray fox are restricted to the six larger islands. The six islands are San Miguel, Santa Rosa, Santa Cruz, Santa Catalina, San Nicholas and San Clemente. Santa Cruz, Santa Rosa and San Miguel are located farther north, while the other three islands -- Santa Catalina, San Nicholas and San Clemente-- are located farther south.

             The colonization of the island species happened in stages, the first to be colonized were the three northern islands, about 20,000-14,000 years ago (Wayne et al. 1991). It was during the Last Ice Age when the islands were connected as one large mass and the bodies of water separating the mainland from the northern California Island were only 6-10 km apart (Wayne and Koepfli, 1996). The colonization of the grey fox from the mainland probably occurred by sweepstakes dispersal, probably by floating on logs and other debris (Wenner & Johnson, 1980). The first arrival of the island foxes probably occurred at Santa Cruz Island. Since the island foxes show little divergence from each other, the island foxes must have been isolated on one island for a time (Wenner & Johnson, 1980). This single island were the parent stock for all the other island foxes. And from there, the island fox radiated outward to the other two islands (Fig. 4). 

              When the sea level rose around 11,500 years ago, Santa Cruz Island was the first to be separated from the original landmass. Following the separating of Santa Cruz Island, in around 9,500 years ago, the separation of Santa Rosa and San Miguel also occurred . The island foxes are found in the fossil record prior to the colonization of the islands by Native Americans. Fossil records of the Island foxes were present on the northern islands around 10,000-9,000 years ago but they do not appear in the fossil record in the southern islands.

            Throughout the Pleistocene, the southern islands were separated. The colonization of the island fox in the three southern islands was probably due to Native Americans who colonized the surrounding area by canoes (Wayne and Koepfli, 1996). The colonization of the island fox was about 2,200 years ago on Santa Nicolas Island, 3,400 years ago on San Clemente Island and around 3,400 to 800 years ago on Santa Catalina Island (Collins, 1991).

           The California Islands were colonized by two distinct groups of Native Americans-- the Chumash and the Gabrielino Indian tribes. Around 7,500 to        3,500 BP, all the islands were inhabited by a single group of people,                              Fig. 4. Map of the colonization of the island fox.          the round-headed people who were probably the earlier Chumash Indians.                             Source: Wayne and Koepfli, 1996.

            By 1500 BP, the "round headed people" were replaced by the "long-headed people," the Gabrielino Indians on San Clemente Island (Collins, 1991). Gabrielino Indians were originally settled in the areas around the Los Angeles Basin and during the last two or three thousand years they had settled in the Southern California Islands. By 3,500 to 800 BP, the islands were separated into two territories (Fig. 5). The northern islands-- San Miguel, Santa Rosa and Santa Cruz were under the Chumash territory, while in the southern islands-- San Nicolas, Santa Catalina and San Clemente were under the Gabrielino Indians (Collins, 1991). The colonization of the southern islands by the island fox were probably brought by the earlier Chumash Indians and not by the later group, the Gabrielino Indians. 

                Fig. 5. Map of tribal territories in southern California Islands. Source: Collins, 1991.

        Native Americans harvested the island fox for their pelts. Pelts were used to make capes, blankets, arrow quivers, costumes and ceremonial headdresses (Collins,1991). They were also kept as pets or were semi-domesticated and played an important role in the religious and ceremonial practices of the Chumash Indians. The Chumash Indians were using the hides for their Fox  (Zorra) solstice dance ceremony (Wenner & Johnson, 1980). The island fox was not an important staple to the Chumash Indians, but served as totems, dream- helpers and legendary spirits (Collin, 1991). Pelts were also used for trading with the mainland and the island other tribes.

Distribution
 

   The Channel Islands are comprised of eight islands about 30 to 98 kilometers off the southern coast of California (Moore & Collins, 1995) (Fig.6).

Fig. 6. Graph of the Island Fox Subspecies, the islands distance from mainland and the square miles of the island land.

Islands	Subspecies	Statute miles	km from the mainland	Sq. miles of Land Area	Sq. km of Land Area
San Nicolas	Urocyon l. dickeyi	61	98	22	58
San Clemente	Urocyon l. clementae	49	79	56	145
Santa Rosa	Urocyon l. santarosae	27	44	84	217
San Miguel	Urocyon l. littoralis	26	42	14	37
Santa Catalina	Urocyon l. catalinae	20	32	75	194
Santa Cruz	Urocyon l. santacruzae	19	30	96	249

Source: Philbrick, 1967, National Park Service, 1999.                                                                                                                                   

  Fig. 7. Distribution map of the Channel Island Fox. Source: California Dept. of Fish and Game, 1980.

Evolution:     

The evolution of the island fox was brought into place with the extinction of the dinosaurs and many other Mesozoic species. With the extinction of the larger predators, it opened a wide array of ecological and diverse niches for mammals. Before the extinction of dinosaurs, Mesozoic mammals were small and rodent-like. As the mammalian species expanded, they diversified into three different subgroups -- the placental, the marsupials (pouch), and the egg laying mammals. The island fox belongs to the placental subgroup.

            The earliest carnivores were the Mesonychidae; the first mammal group to fill the carnivore niche (Werdelin, 1996). Mesonychidae were soon replaced by the Creodonta by the late Eocene. Creodonta were the first placental mammals, but they were not true carnivorans (Hunt, 1996). Placental mammals later radiated into true carnivores in the middle and late Cenozoic, and are confined to the northern continents. Creodonts were soon replaced by the Miacoidea by the end of the Miocene (Fig. 8).

             The family Miacoidea began to diversify by late Eocene, and by Miocene they had successfully undergone radiation. Previously, the order Carnivora were small, arboreal and in many cases omnivores/insectivores mammals.The suborder Canoidea are one of the successful radiation that occurred in the late Miocene. In Canoidea there are four families -- Canidae (Canids), Ursidae, Procyonidae and Mustelidae (Gotch, 1979).

            The radiation of the canids is the major feature of the post-Miocene carnivorans (Weredelin, 1996). Canids had evolved in the Nearctic region during the middle and late Cenozoic (Hunt, 1996). Most of the living canids we have today is from the subfamily Caninae. Canines evolve from a unbroken line from a earlier cynoid, the small fox sized Leptocyon, who lived in North America in the late Oligocene and early to middle Miocene. The diversification of canine canids didn't occur until late Miocene, when the first appearance of the Canis and Vulpus occurred (Hunt, 1996). It wasn't until the Pleistocene, when the Genus Urocyon first appeared as the gray fox (Stains, 1975).                                                                                                                                                          

Fig. 8. Evolution of the island fox. Source: Ewer, 1973.

Tracks:

       The island fox is unique among the canids. Like the mainland gray fox, the island fox have semi-retractile nails (De la Rosa & Nocke, 2000). Probably an adaptation to their semi-arboreal life. Tracks are similar to the gray fox, common house cats and small dogs, except the marks of claws are usually clearly visible (Fig.9a). The tracks are also smaller in size. The hind foot is about 29 mm wide and 38 mm long (Moore & Collins, 1995) (Fig 9b). Tracks of the front foot are usually larger than the tracks of the hind foot and the distance between the two is around 18 to 23 cm apart, with the overlapping of the hind foot with the front foot (Moore & Collins,1995) (Fig. 9c). 

Fig. 9a:  (below) The tracks of a island fox.                                                    Fig. 9c: (below) Trail of a island fox.

                                                         Fig. 9b. (above) The feet of island fox.

Source: Marie, 1975, Moore & Collins, 1995.

Breeding:

           Channel Island foxes are based on a single family unit. They are found either alone or in pairs throughout the year, except during the weaning seasons, when the pups are with them (Laughrin ,1973). Most breeding is done by the adults even though a pup can mate and start breeding in the second year. Pups reach sexual maturity approximately 10 months old. While island foxes are usually solitary in the non-breeding seasons, mates come together in January. Mating takes place in late February to early March. Kits are born in late April and early May and weigh approximately 100 grams (Nowak & Paradiso, 1983). Island kit foxes reach adult weight by the first winter.

            The gestation period is thought to be similar to gray fox, with the average of 50-53 days (Moore & Collins, 1995). Litter sizes range from one to five, but on the average the size is two to three. Kits are born blind and helpless, and depend entirely on the parents for survival. Like most wild canids, male foxes play an important role in raising the young. In late August or early September, parents begins to force their young to become independent (Laughrin, 1973).

Behavior:

           Channel island foxes are docile, playful, affectionate and curious by nature and have a general lack of fear of humans (Baird, 1974, Moore & Collins, 1995). Island foxes are diurnal     but they can be active at night and early morning (National Park Service, 1999). Island foxes       are easily tamed and their docile behavior and diurnal habits are probably the results of the    absence of large predators and the harassment of humans (Fig. 10).

            They communicate to each other through various body language, vocalizations, visual       and olfactory signals (Moore & Collins, 1995). Island foxes bark resemble barks from a      common dog (Grinnel et al, 1937). Occasionally, barking from the island foxes can be heard at night. Vocalizations are used by both sexes to show dominance between sexes. Visual signals can  show dominating behavior as well submissive behavior. Submissive behavior can be expressed the through lowering of the head, the flattening and down turning of the ears, the lack of eye contact, whining, nibbling and licking. The showing of dominance and submissive behavior is similar to the gray fox. Also mutual grooming between mates and occasionally between kits and an adult occurs (Moore & Collins, 1995). Olfactory signals such as the leavings of urine and feces along trails, road edges and prominent places is just another form of communication.

            The Channel Island fox is one of two species of Canidea that lives in California that either climbs trees to escape from predators or to gain entrance to a breeding den (Grinnel et al. 1973). Breeding dens are usually any available sheltered sites. Sheltered dens are found in burrows, hollow logs or trees, shrubs, caves and under rocks. Dens are usually found intact, and also serve the purpose of a hiding place from predators, protection against harsh weather and other dangers (Laughrin, 1973). If no suitable sheltered sites are found, island foxes are known to dig their own, usually a simple tunnel below ground.        

            Dens are only used for breeding and when the kits are in need of protection while they are young. Dens are abandoned when the young begin to forage with their parents, around mid-June to late summer (Moore & Collins ,1995). A young island fox is usually 3-4 weeks old when it emerges from the den and by two months, island foxes are spending most of their time outside their shelter. In late September, the parents are dispersed away from the dens, while the kits are known to forage around it until December. Occasionally the siblings of the litter can be seen foraging together. Some dens are used seasonally during the breeding seasons while others are used only once (Moore & Collins, 1995).

        Activity patterns of the Channel Island fox vary diurnally with the seasons. Daily foraging occurs early morning, late afternoon to early evening. However, Channel Island foxes are also seen around any hour of the day or night. Early morning hours, such as 2 am to 5 am, and mid-day are the times that Channel Island foxes are seen the least (Laughrin, 1973). Both foxes--the mainland Gray fox and the Channel Island fox-- are derived from the same nocturnal ancestor. Over time changes occurred due to the insular habitat, the lack of predation and competition, the Channel Island fox had adapted to a diurnal behavior system compared to the mainland gray fox (Laughrin, 1973).

Habitat:

            Island foxes are highly diverse in their habitat. Island habitat found on the southern California Islands includes valley and foothill grasslands, coastal bluff, coastal dunes, maritime cactus scrub, coastal sage, oak and island chaparral woodlands, island and riparian woodlands, Bishop and Torrey pine forests and coastal marsh (Moore & Collins, 1995).

            The Channel Island foxes daily movement is contained to the foxes home range. Home ranges vary in size due to the season, age and the sex of the fox. Male island foxes are slightly larger than the female fox (Crooks & Van Vuren, 1996). Home ranges for the male fox are larger during autumn and winter, while in the spring and summer home ranges are smaller. Female home ranges are the same throughout the year (Moore & Collins, 1995). Home ranges overlap with other neighboring island foxes and home territories are marked by urine and feces left on conspicuous land features.                                                                                                                                                   

Diet:                                                                                                

            The Channel Island foxes diet is omnivorous. Diet depends on the abundance of food resources available in their home range, but primarily consists of insects and fruits. Fruits include manzanita, elderberries,  toyon berries, saltbush, prickly pear cactus, ice plant, and sea figs (Laughrin, 1973, Moore & Collins, 1995, Von Bloeker, 1967). Insects include beetles, grasshoppers and Jerusalem crickets (Laughrin, 1973, Von Bloeker, 1967). Channel island fox also feeds on land snails, ground birds (chicks and eggs), reptiles and rodents such as the deer mouse, crabs and other marine invertebrates (Von Bloeker, 1967). Occasionally, Channel Island foxes are known to climb trees to find food, hence how the island fox got its other common name, the tree fox. Carcasses of pigs, sheep, cattle, seals and other marine mammals are also food resource for the island fox, especially during lean times when the normal food resources are unavailable (Moore and Collins,1995, Von Bloeker, 1967).

Problems:

            In the past four years the fox population has declined due to many reasons. The degrading and loss of habitat due to overgrazing, urban development, military activities, fires, competition for food with feral and domesticated cats, predation by the golden eagles, invasion from non-native plant and animal species, vehicles on islands that have extended roads and introduced diseases such as canine distemper, brought to the island fox population by human visitors with their dogs (National Park Service, 1999, Department of Fish and Game, 2000).         

Conservation:

            The Channel Island fox is the predator to another listed endangered species, the federally list San Clemente loggerhead shrike. Due to this, there are controversies on how to save one particular species without destroying the other. In 1997, the Department of Fish and Game, the Navy and the United States Fish and Wildlife Service began to develop a program to help control the overall predation of the San Clemente loggerhead shrike. The plan was to euthanize thirty-two San Clemente Island foxes, and the capturing of the other island foxes in cages. In 1999, the plan was implemented, and they found that the plan had helped temporarily to lessen the threat of  island foxes, and the captivated island foxes were released at the site of their capture (Department of Fish and Game, 2000).

            In April of 1999, the National Park Service's concern of the declining of island foxes, got together an Advisory Board to help identify the reasons why the population was declining. The Board, called the Fox Recovery Team, identified the decline of the island fox was mainly due to the predation of the golden eagle, which were first attracted to the sheep and the cattle, introduced through ranching, and parasites/diseases by pets. The National Park Service is now trying to implement programs to help stabilized the fox population. The program starts with building sanctuaries to protect them from eagle predation, the starting of a captive breeding program to re-introduce the island fox population to the channel islands, re-introducing the bald eagles to help displace the golden eagles while relocating the non-native golden eagles to the mainland. Attempts to have the island fox listed as a federal endangered species are underway (National Park Service, 1999).

Other interesting facts:
    

Dental formula of the grey fox and the channel island fox is 3-1-4-2 for the upper jaw and 3-1-4-3 for the lower jaw (Moore & Collins, 1995).

Channel Island foxes are commonly mistaken for the red fox, because of the reddish coloration on it's under parts, even though the red fox is a distinctly different fox genus (Grinnel et al. 1937).

Originally named Vulpes littoralis in 1857 by Spencer Fullerton Baird but later changed to Urocyon littoralis in 1888 by Merriam.

The island fox has a misspelled species name. Even though in English it is spelled correctly, in Latin there should only be one 't', but since the name has been internationally accepted, the misspelled name is still used today (Gotch, 1979).

Other common names include coast fox, short-tailed fox, channel island fox, California channel island fox, beach fox, tree fox and insular gray fox.

Links:

California Threatened and Endangered Species

www.dfg.ca.gov/te_species/index/classification/mammalslist/islandfox.html

California Coast and Ocean

http://ceres.ca.gov/coastalconservancy/coast&ocean/autumn99/pages/ptwo.htm

The Biogeography of the San Joaquin Kit Fox (Vulpes macrotis)

http://bss.sfsu.edu/geog/bholzman/courses/Fall00Projects/kfox.html

Animal Diversity- The University of Michigan

http://animaldiversity.ummz.umich.edu/accounts/urocyon/u._littoralis$narrative.html

Utah's Hogle Zoo

http://www.xmission.com/~hoglezoo/mammals/fox.htm

Bibliography
 

Baird, Spencer F. 1974. Mammals of North America. New York, NY. Arno Press.

California Department of Fish and Game. 1980. "Island Fox." pp. 137-138. In: At the crossroads: a report on the status of California's endangered and rare fish and wildlife. Sacramento, CA.

California Dept. of Fish and Game. 2000. Habitat Conservation Planning Branch (California's Plants and Animals): The Status of Rare, Threatened, and Endangered Animals and Plants of California, Island Fox. [Online]. Available: http://www.dfg.ca.gov/hcpb/species/jsp/ssc_result.jsp?specy=mammals&query=Urocyon%20littoralis [November 1, 2002]

Collins, Paul W. 1991. "Interactions between island foxes (Urocyon-littoralis) and Native Americans on islands off the coast of Southern California." Journal of Ethnobiology 11(2): 205-229.

De la Rosa, Carlos and Claudia C. Nocke. 2000. A Guide to the Carnivores of Central America. Austin, Texas. University of Texas Press.

Ewer, R.F. 1973. The Carnivores. Ithaca, NY. Cornell University Press.

Gotch, A.F. 1979. Mammals-Their Latin Names Explained: A Guide to Animal Classification. Poole, Dorse, UK. Blandford Press Ltd.

Grinnel, J. J. Dixon and J.M. Linsdale. 1937. Fur-bearing Mammals of California, vol. 2. Berkeley, CA. University of California Press.

Hunt, Jr., Robert M. 1996. “Biogeography of the Order Carnivora.” pp. 485-541. In John L. Gittleman, ed. Carnivore Behavior, Ecology and Evolution, vol. 2. Ithaca, NY. Cornell University Press.

Laughrin, Lyndal L. 1973. California Island Fox Survey. Sacramento, CA. California Dept. of Fish and Games.

Moore, Claybourne M. and Paul W. Collins. 1995. "Urocyon littoralis." Mammalian species 489:1-7.

Murie, Olaus J. 1975. A Field Guide to Animal Tracks. Boston, Massachuset. Houghton Mifflin Company.

National Park Service. 1999. Channel Islands National Park: Saving the Island Fox. [Online]. Available: http://nps.gov/chis/naturalresources/IslandFox/fox3.htm [Oct. 21, 2002]

Nowak, Ronald M. 1999. Walker’s Mammals of the World.  Baltimore, Maryland. John Hopkins University Press.

Philbrick, Ralph N., ed. 1967. Proceedings of the Symposium on the Biology of the California islands. Santa Barbara, CA. Santa Barbara Botanic Garden.

Power, D.M., ed. 1980. The California Islands. Santa Barbara, CA. Santa Barbara Musuem of Natural History.

Stains, Howard J. 1975. “Distribution and Taxonomy of the Canidae.” pp. 3- 26. In: M. W. Fox (ed). The Wild Canids: Their Systematics, Behavioral Ecology and Evolution. New York, NY. Van Nostrand Reinhold Company.

Valentine, James W. and Jere H. Lipps. 1967. “Late Cenozoic History of the Southern California Islands.” pp. 22. In Ralph N. Philbrick, ed. Proceedings of the Symposium on the Biology of the California islands. Santa Barbara, CA. Santa Barbara Botanic Garden.

Von Bloeker, Jr., Jack C. 1967. “The Land Mammals of the Southern California Islands.” pp. 245-263.  In Ralph N. Philbrick, ed. Proceedings of the Symposium on the Biology of the California islands. Santa Barbara, CA. Santa Barbara Botanic Garden.

Wayne, Robert K. and Klaus-Peter Koepfli. 1996. “Demographic and Historical Effects on Genetic Variation of Carnivores.” pp. 453-484. In John L. Gittleman, ed. Carnivore Behavior, Ecology and Evolution, vol. 2. Ithaca, NY. Cornell University Press.

Wayne, R.K., S.B. George, D. Gilbert, P.W. Collins, D. Girman, etc. 1991. “A morphologic and genetic study of the Island Fox Urocyon-littoralis.” Evolution 45(8): 1849-1868.

Wenner, A.M. and D.L. Johnson. 1980. "Land Vertebrates:Sweepatakes or Bridges." pp. 497-530. In D.M. Powers, ed. The California Islands. Santa Barbara, CA. Santa Barbara Musuem of Natural History.

Werdelin, Lars. 1996. "Carnivoran Ecomorphology: A Phylogenic Perspective." pp. 583-624. In John L. Gittleman,ed. Carnivore Behavior, Ecology and Evolution, vol. 2. Ithaca, NY. Cornell University Press.

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