Lifespan, longevity, and ageing

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Observations: Longevity has not been studied in detail in these animals. Nonetheless, one captive animal lived for 10.5 years (Richard Weigl 2005).
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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)

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Liu, S. 2002. "Urocyon littoralis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Urocyon_littoralis.html
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Sonia Liu, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Behavior

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Perception Channels: tactile ; chemical

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Liu, S. 2002. "Urocyon littoralis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Urocyon_littoralis.html
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Sonia Liu, University of Michigan-Ann Arbor
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Conservation Status

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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)

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: critically endangered

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Liu, S. 2002. "Urocyon littoralis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Urocyon_littoralis.html
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Benefits

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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)

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Liu, S. 2002. "Urocyon littoralis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Urocyon_littoralis.html
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Trophic Strategy

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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

Primary Diet: omnivore

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Liu, S. 2002. "Urocyon littoralis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Urocyon_littoralis.html
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Sonia Liu, University of Michigan-Ann Arbor
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Distribution

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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)

Biogeographic Regions: nearctic (Native )

Other Geographic Terms: island endemic

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Liu, S. 2002. "Urocyon littoralis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Urocyon_littoralis.html
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Habitat

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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)

Terrestrial Biomes: savanna or grassland ; chaparral ; forest

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Liu, S. 2002. "Urocyon littoralis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Urocyon_littoralis.html
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Sonia Liu, University of Michigan-Ann Arbor
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Morphology

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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)

Range mass: 1 to 2 kg.

Other Physical Features: endothermic ; homoiothermic; bilateral symmetry

Sexual Dimorphism: male larger

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Liu, S. 2002. "Urocyon littoralis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Urocyon_littoralis.html
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Sonia Liu, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Reproduction

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

Mating System: monogamous

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)

Range number of offspring: 1 to 5.

Average number of offspring: 2.5.

Range gestation period: 50 to 63 days.

Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual

Average number of offspring: 2.6.

Average age at sexual or reproductive maturity (female)
Sex: female:
365 days.

Parental Investment: altricial ; extended period of juvenile learning

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Liu, S. 2002. "Urocyon littoralis" (On-line), Animal Diversity Web. Accessed April 27, 2013 at http://animaldiversity.ummz.umich.edu/site/accounts/information/Urocyon_littoralis.html
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Sonia Liu, University of Michigan-Ann Arbor
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Phil Myers, Museum of Zoology, University of Michigan-Ann Arbor
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Biology

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Island foxes are primarily monogamous and mate for life, with a pair sharing a territory until one member of the pair dies. However, while they are socially monogamous, both members of the pair may mate with other adults (7). Most breeding occurs in late February and early March, and 50 to 53 days after mating, the female, or vixen, gives birth to a litter of one to five (usually two to three) kits. Born in the protection of a den, the pups are blind and helpless at birth. The kits emerge from the den at three to four weeks of age and soon begin foraging for food with their parents (4). By late September the kits are independent, and before long, they disperse to their own territory, provided there is a vacant territory and an available mate (7). At around one year of age the young foxes begin to breed. Island foxes have an average life span of four to six years (4). Island foxes communicate through sight, sound and smell. Vocal communication involves barking and sometimes growling, and signs of dominance or submission are frequently made through facial expressions and body posture. A keen sense of smell plays an important role in the marking of territories, which are scent-marked by urine and faeces, conspicuously positioned on well-traveled paths (4). This species of fox forages primarily at night, but is also active during the day (2). The island fox feeds on an incredibly wide variety of insects, vertebrates, fruits, and terrestrial molluscs, with the proportions of the diet depending on where the fox lives and the time of year (2) (4).
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Conservation

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The island fox is listed by the state of California as a threatened species (1), and the islands themselves also receive protection. Santa Rosa, San Miguel and Santa Cruz are part of the Channel Islands National Park, which is protected by the U.S National Park Service, and the western portion of Santa Cruz Island is also protected by The Nature Conservancy. Dogs and cats are prohibited from being brought into the Channel Islands National Park, in order to prevent infections from being transmitted to the foxes (6). Santa Catalina Island is owned and managed by the Catalina Island Conservancy (14), and the remaining two islands, San Nicolas and San Clemente, are owned and managed by the U.S. Navy (1). Captive breeding and reintroduction programmes on San Miguel, Santa Rosa and Santa Cruz Islands, along with programmes to remove and relocate golden eagles and reintroduce bald eagles, have been a remarkable success. The San Miguel population, which was once the most endangered, made such a strong recovery through the captive breeding program, and the wild population was doing so well, that all releasable individuals were returned to the wild in July 2007. On Santa Cruz, many captive bred foxes have also been returned to the wild. Unfortunately, a number of these have been the victims of continued golden eagle predation, but with January 2007 seeing the removal of all the feral pigs, it is hoped that there will be less motivation for any golden eagles to remain on the island (11). On Santa Catalina, less than one year after the CDV-caused decline in the fox population, the Institute for Wildlife Studies began an island-wide vaccination program against this disease. In addition, a captive breeding program was initiated to aid in repopulating the island. The program has been a resounding success (12), and the population continues to recover from its near-catastrophic decline (11). With the continuation of such determined conservation efforts, hopefully the island fox will one day serve as an example of how critically endangered species can be pulled back from the brink of extinction.
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Description

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The island fox is the smallest North American canid, found only on the California Channel Islands. A descendent of the mainland gray fox (Urocyon cinereoargenteus) (2), the island fox evolved into a unique species over 10,000 years ago, retaining similar markings to its ancestor but evolving to be just two-thirds of the size (3). The dorsal coat of the island fox is a grizzled mix of greyish-white and black, while the underside is a dull white. The ears, neck and the sides of the legs are usually cinnamon-coloured, and the chin, borders of the lips and the area between the eyes and nose are black. The tail has a well-defined, black, narrow stripe along the top, greyish sides and is rusty-coloured underneath (4). Males are significantly heavier than females (2), while young foxes normally have a paler and thicker fur coat than adults, and their ears are a darker colour (4). Island foxes moult twice a year, gaining a winter pelage in October to November, which is replaced with a less dense summer pelage during March to May (5).
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Habitat

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The Channel Islands have a Mediterranean-type climate, which is hot and dry in the summer, and cool and wet in the winter (6). The foxes occur in all habitats on the islands, including valley and foothill grasslands, coastal sage scrub, sand dunes, island chaparral, coastal oak and pine forests, and marshes. Dens include ground holes, hollow trees, rock piles, shrubs, caves, and man-made structures (4).
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Range

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Restricted to six of the largest Channel Islands, 19 to 60 miles off the coast of southern California, USA (1). These include the islands of Santa Catalina (U. l. catalinae), San Clemente (U. l. clementae), San Nicolas (U. l. dickeyi), San Miguel (U. l. littoralis), Santa Cruz (U. l. santacruzae), and Santa Rosa (U. l. santarosae) (2).
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Status

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Classified as Critically Endangered (CR) on the IUCN Red List (1). Six subspecies are recognised: Urocyon littoralis littoralis, U. l. catalinae, U. l. clementae, U. l. dickeyi, U. l. santacruzae and U. l. santarosae (2).
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Threats

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Numbers of island foxes declined at alarming rates since 1994, with four of the six subspecies declining by as much as 95 percent. The primary threats causing these devastating declines were predation by golden eagles (Aquila chrysaetos) on the northern Channel Islands, canine distemper virus (CDV) on Santa Catalina Island, and collision with vehicles on San Clemente and San Nicolas Islands (2) (8). Golden eagles had not always lived on the Channel Islands, but were attracted there by the introduction of wild pigs (Sus scrofa) (9). These impressive birds-of-prey colonized the northern Channel Islands in 1994 and began to prey heavily on foxes, quickly bringing the island fox to the brink of extinction (10). By 1999, only 14 individuals of the San Miguel subspecies remained (11). On Santa Catalina Island, the introduction of CDV, (believed to be brought to the island by a domestic dog), caused the deaths of about 90 percent of the fox population in just one year, (1999 to 2000) (12). The introduction and spread of CDV, and other canine diseases, remains a potential threat to all the island fox subspecies (8). In 1999, 32 foxes on San Clemente Island were either culled or permanently removed from the island to zoological institutions, as part of a programme to protect the endangered bird, the loggerhead shrike (Lanius ludovicianus). Another 49 were temporarily held in small pens while the shrikes were nesting, and in 2000, a further 71 foxes were held again. This practice has since been stopped, but the disruption this caused to reproduction and social systems is believed to have significantly affected the San Clemente Island fox population and contributed to its current Critically Endangered status (13). Like any small, isolated island populations, the island fox remains extremely vulnerable to any catastrophic mortality source, be it predation, canine disease, or environmental extremes (1).
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One Species at a Time Podcast

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In this episode, reporter Molly Samuel journeys to Santa Cruz Island, off the coast of California, to look into the mystery of the island’s tiny foxes, descendants of gray foxes who rafted over from the mainland more than ten thousand years ago and branched off to form a new, smaller species. Despite weighing a mere three pounds, these diminutive grey foxes thrived and for millennia they reigned as the island’s top predator.

But twenty years ago, their numbers began to plummet, from three thousand in the early 1990s to fewer than one hundred by 2000. Samuel tells how conservationists solved the puzzle of the vanishing foxes and helped them stage a comeback.

Listen to the podcast, meet the featured scientist and find extra multimedia on the Learning + Education section of EOL.

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Island fox

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The island fox (Urocyon littoralis) is a small fox that is endemic to six of the eight Channel Islands of California. There are six subspecies, each unique to the island it lives on, reflecting its evolutionary history. They are generally docile, show little fear of humans, and are easily tamed. Island foxes played an important role in the spiritual lives of native Channel Islanders. They have been likely semi-domesticated as pets, used as pelts, or for other functions, like pest control.[3]

Taxonomy and evolution

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The skull of an island fox (right) compared with a skull of the related gray fox (left).

The island fox shares the genus Urocyon with the mainland gray fox (U. cinereoargenteus), the species from which it is descended. Its small size is a result of insular dwarfism, a form of allopatric speciation. Because the island fox is geographically isolated, it has no immunity to parasites and diseases brought in from the mainland and is especially vulnerable to those that the domestic dog may carry. In addition, predation by the golden eagle (Aquila chrysaetos) and human activities devastated fox numbers on several of the Channel Islands in the 1990s. Four island fox subspecies were federally protected as an endangered species in 2004, and efforts to rebuild fox populations and restore the ecosystems of the Channel Islands are being undertaken. Radio collars are being attached to foxes in an effort to track and locate the young foxes. To date these efforts have been largely successful.[4]

There are six subspecies of the island fox,[1] each of which is native to a specific Channel Island, and which evolved there independently of the others. The subspecies are:[1]

Foxes from each island are capable of interbreeding, but have genetic and phenotypic distinctions that make them unique; for example, the subspecies have differing numbers of tail vertebrae.

The small size of the island fox is an adaptation to the limited resources available in the island environment. The foxes are believed to have "rafted" to the northern islands between 10,400 and 16,000 years ago.[5][6] Initially, fox populations were located on the three northern islands, which were likely easier to access during the last ice age — when lowered sea levels united four of the northernmost islands into a single mega-island (Santa Rosae) and the distance between the islands and the mainland was reduced — it is likely that Native Americans brought the foxes to the southern islands of the archipelago, perhaps as pets, or hunting dogs.[7][8]

 src=
Engraving of the island fox from the Pacific Railroad survey of 1855

Other names for the island fox include coast fox, short-tailed fox, island gray fox, Channel Islands fox, Channel Islands gray fox, California Channel Islands fox and insular gray fox.

Description

The island fox is significantly smaller than the related gray fox, and is the smallest fox in North America, averaging slightly smaller than the swift (Vulpes velox) and kit foxes (Vulpes macrotis). Typically, the head-and-body length is 48–50 cm (19–19.5 in), shoulder height 12–15 cm (4.5–6 in), and the tail is 11–29 cm (4.5–11.5 in) long, which is notably shorter than the 27–44 cm (10.5–17.5 in) tail of the gray fox. This is due to the fact that the island fox generally has two fewer tail vertebrae than the gray fox.[9] The island fox weighs between 1 and 2.8 kg (2.2 and 6.2 lb). The male is always larger than the female.[10] The largest of the subspecies occurs on Santa Catalina Island and the smallest on Santa Cruz Island.[10]

The island fox has gray fur on its head, a ruddy red coloring on its sides, white fur on its belly, throat and the lower half of its face, and a black stripe on the dorsal surface of its tail.[10] In general the coat is darker and duller hued than that of the gray fox. The island fox molts once a year between August and November. Before the first molt pups are woolly and have a generally darker coat than adult foxes. A brown phase, with the grey and black fur of the body replaced by a sandy brown and a deeper brown, may occur in the San Clemente Island and San Nicolas Island populations. It is unclear if this is a true color phase, a change that occurs with age, or possibly a change that occurs because of interactions with Opuntia cactus spines that become embedded in the pelt.[11]

 src=
An island fox kit nestled in the brush

Reproduction

The island fox typically forms monogamous breeding pairs, which are frequently seen together beginning in January and through the breeding season, from late February to early March. The gestation period is 50–63 days. The female island fox gives birth in a den, a typical litter having one to five pups, with an average of two or three. Pups are born in the spring and emerge from the den in early summer; the mother lactates for 7–9 weeks. Sexual maturity is reached at 10 months, and the females usually breed within the first year. Island foxes live for 4–6 years in the wild and for up to 8 years in captivity.[10]

Ecology and behavior

 src=
A nighttime shot of an island fox with three mice in its jaws.

Its preferred habitat is complex layer vegetation with a high density of woody, perennially fruiting shrubs. The fox lives in all of the island biomes including temperate forest, temperate grassland and chaparral, with no island supporting more than 1,000 foxes. The island fox eats fruits, insects, birds, eggs, crabs, lizards, and small mammals, including deer mice. The fox tends to move around by itself, rather than in packs. It is generally nocturnal, although with peaks of activity at dawn and dusk. Activity also fluctuates with the season: It is more active during the day in summer than it is in winter.[10]

The island fox is not intimidated by humans, although at first may show aggression. It is quite easy to tame and is generally docile.[10] The island fox communicates using auditory, olfactory and visual signals. A dominant fox uses vocalizations, staring, and ear flattening to cause another fox to submit. Signs of dominance and submission are visual, such as facial expression and body posture.[12] Its main vocalizations are barking and growling.[12] The island fox marks territory with urine and feces.

Conservation status and federal protection

 src=
The golden eagle is four times the size of the island fox and can easily prey on it.

In March 2004, four subspecies of the island fox were classified as a federally protected endangered species: the Santa Cruz island fox, Santa Rosa island fox, San Miguel island fox and the Santa Catalina island fox.[13] As of 2013, the IUCN lists the entire species as near threatened, an improvement from its previous status of "critically endangered".[2] A decline in island fox populations was identified in the 1990s. On San Miguel Island, the decline began in 1994, with the population falling from 450 adults to 15 by 1999. Similar population declines were discovered on Santa Cruz Island. On the Santa Cruz Island the population decreased from 2,000 adults in 1994 to less than 135 in 2000, and on Santa Rosa Island where foxes may have numbered more than 1,500 in 1994, but were reduced to 14 animals by 2000.[14][15] In 2004, there were 38 San Miguel island foxes, all in captivity; 46 foxes in captivity on Santa Rosa Island and seven in the wild (golden eagle predation prevented the release of captive foxes into the wild); Santa Cruz Island had 25 captive foxes and a stable wild population of around 100 foxes.[15]

Golden eagle predation, discovered when foxes were radio-collared and monitored, proved to be the cause of the high mortality rates.[16] The golden eagle was an uncommon visitor to the Channel Islands before the 1990s according to data gathered by Dr. Lyndal Laughrin of the University of California Santa Cruz Island Reserve, and the first golden eagle nest was recorded on Santa Cruz Island in 1999.[17] Biologists propose that the eagle may have been attracted to the islands in the 1960s after the decline of the bald eagle. The golden eagle replaced the bald eagle and began to feed on feral pigs following the devastation of the local bald eagle population due to DDT exposure in the 1950s—the bald eagle would have deterred the golden eagle from settling on the islands while it subsisted on fish.[16]

The feral pigs on Santa Rosa were exterminated by the National Park Service in the early 1990s, which removed one of the golden eagle's food sources. The golden eagle then began to prey on the island fox population. Feral pigs on Santa Cruz Island and deer and elk on Santa Rosa Island were introduced almost 70 years prior to island fox decline, therefore, the golden eagle most likely did not seek these animals as alternative prey.[18] This has occurred most likely as a result of a process known as apparent competition: in this process, a predator, like the golden eagle, feeds on at least two prey, for example, the island fox and feral pigs. One prey item is adapted to high predation pressure and supports the predator population (i.e. pigs), whereas the other prey item (i.e. the island fox) is poorly adapted to predation and declines as a consequence of the predation pressure. It has also been proposed that the complete removal of golden eagles may be the only action that could save three subspecies of the island fox from extinction.[19] However, the pigs on Santa Cruz Island were killed by the Nature Conservancy on the idea that they drew the eagles to the foxes.[20]

Introduced diseases or parasites can devastate island fox populations. Because the island fox is isolated, it has no immunity to parasites and diseases brought in from the mainland and are especially vulnerable to those the domestic dog may carry. A canine distemper outbreak in 1998 killed approximately 90% of Santa Catalina Island's foxes, reducing the population from 1,300 to 103 in 2000.[17] A vaccination program has been initiated to protect Catalina Island foxes from canine distemper.[21] After several years of carefully trapping the foxes and vaccinating them against distemper and rabies, their population has reached 1,717 in 2015, surpassing the pre-disease population of about 1,300.[22] Scientists believe the distemper virus was introduced by a pet dog or a raccoon from the mainland that hitched a ride on a boat or a barge.[23] To eliminate the risk of disease, pets are not permitted in Channel Islands National Park.

Diminished food supply and general degradation of the habitat due to introduced mammal species, including feral cats, pigs, sheep, goats, and American bison, the last having been introduced to Catalina Island in the 1920s by a Hollywood film crew shooting a Western,[24] also has had a negative effect on fox populations.

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San Clemente Island Fox at Santa Barbara Zoo as part of a Species Survival Plan

The foxes threaten a population of the severely endangered San Clemente Island loggerhead shrike in residence on San Clemente Island. The island fox population has been negatively affected by trapping and removal or euthanasia of foxes by the United States Navy. Since 2000, the Navy has employed different management strategies: trapping and holding foxes during the shrike breeding season, the installation of an electric fence system around shrike habitats, and the use of shock collar systems.[25] With the gradual recovery of the shrike population on San Clemente Island, the Navy no longer controls the foxes.

The populations of Santa Cruz island foxes, San Miguel island foxes, and Santa Rosa island foxes have dramatically rebounded from lows in 2000 of 70 for the Santa Cruz foxes and 15 each on San Miguel and Santa Rosa Islands.[26] The Catalina Island Conservancy runs a captive breeding program on Catalina Island.[27] On September 14, 2012, the US Fish and Wildlife Service released a draft recovery plan for the San Miguel island fox, Santa Rosa island fox, Santa Cruz island fox, and the Santa Catalina island fox.[28] By 2012, the Catalina Island Conservancy determined that there were 1,500 Santa Catalina island foxes and the population was stable.[29] As of 2015, there were 520 native foxes on San Miguel and 874 on Santa Rosa, according to the group Friends of the Island Fox. The number of foxes on Santa Cruz Island had risen to 1,750. The US Fish and Wildlife Service recommended delisting Santa Cruz, San Miguel and Santa Rosa island foxes in a major success of the Endangered Species Act. However, they are recommending that the Santa Catalina island be reclassified from endangered to threatened, because of the threat of diseases on this heavily visited island.[22]

Two other subspecies on San Nicolas and San Clemente are not endangered. There were 263 foxes on San Nicolas and 1,230 on San Clemente.

Because the Channel Islands are almost entirely owned and controlled by either the Catalina Island Conservancy, The Nature Conservancy, or the federal government, the fox has a chance to receive the protection it needs, including constant supervision by interested officials without the ongoing threat of human encroachment on its habitat.

The fox did not persist on Anacapa Island because it has no reliable source of fresh water; Santa Barbara Island is too small to support the food needs of a viable fox population.

Rene Vellanoweth, an archaeologist, believes that inbreeding depression can be managed by mixing the different island fox subspecies populations much as the indigenous peoples did, by moving them from island to island, creating a higher genetic diversity and assisting them in recovery.[30]

See also

References

  1. ^ a b c Wozencraft, W.C. (2005). "Order Carnivora". In Wilson, D.E.; Reeder, D.M (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. p. 583. ISBN 978-0-8018-8221-0. OCLC 62265494.
  2. ^ a b Coonan, T.; Ralls, K.; Hudgens, B.; Cypher, B. & Boser, C. (2013). "Urocyon littoralis". The IUCN Red List of Threatened Species. 2013: e.T22781A13985603. doi:10.2305/IUCN.UK.2013-2.RLTS.T22781A13985603.en.
  3. ^ Booth, Derek; Allan Gillespie (1971). "Quaternary Research and Education". Quaternary Research. Editorial. 1 (3): 283–284. Bibcode:1971QuRes...1..283.. doi:10.1016/0033-5894(71)90066-4.
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  5. ^ Wayne, R.K.; et al. (1991). "A morphological and genetic-study of the Island fox, Urocyon littoralis". Evolution. 45 (8): 1849–1868. doi:10.2307/2409836. JSTOR 2409836. PMID 28563958.
  6. ^ Gilbert, D.A.; et al. (1991). "Genetic fingerprinting reflects population differentiation in the California Channel Island fox". Nature. 344 (6268): 764–767. doi:10.1038/344764a0. PMID 1970419. S2CID 4303549.
  7. ^ Collins, P.W. (1991). "Interaction between the island foxes (Urocyon littoralis) and Indians on islands off the coast of southern California. I Morphologic and archaeological evidence of human assisted dispersal" (PDF). Journal of Ethnobiology. 11: 51–82.
  8. ^ Hofman, Courtney A.; Rick, Torben C.; Hawkins, Melissa T.R.; Funk, W. Chris; Ralls, Katherine; Boser, Christina L.; et al. (2015). "Mitochondrial Genomes Suggest Rapid Evolution of Dwarf California Channel Islands Foxes (Urocyon littoralis)". PLOS ONE. 10 (2): e0118240. Bibcode:2015PLoSO..1018240H. doi:10.1371/journal.pone.0118240. PMC 4340941. PMID 25714775.
  9. ^ Grambo, Rebecca L. (1995). The World of the Fox. Vancouver: Greystone Books. p. 102. ISBN 978-0-87156-377-4.
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  11. ^ Sillero-Zubiri, Claudio; Hoffman, Michael & MacDonald David W. (2004). Canids: Foxes, Wolves, Jackals, and Dogs (PDF) (Report). Status Survey and Conservation Action Plan. Gland, Switzerland; Cambridge, UK: IUCN. p. 98.
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  13. ^ Proposed Designation of Critical Habitat for the San Miguel Island Fox, Santa Rosa Island Fox, Santa Cruz Island Fox, and Santa Catalina Island Fox (Report). Endangered and Threatened Wildlife and Plants. U.S. Environmental Protection Agency. 2004.
  14. ^ Roemer, G. W.; Garcelon, D. K.; Coonan, T. J. & Schwemm, C. (1994). "The use of capture–recapture methods for estimating, monitoring, and conserving island fox populations". In Halvorsen, W. L. & Maender, G. J. (eds.). The Fourth California Islands Symposium: Update on the Status of Resources. Santa Barbara, California: Santa Barbara Museum of Natural History. pp. 387–400.
  15. ^ a b Coonan, T. J.; et al. (2004). 2003 Annual Report (Report). Island fox recovery program. Channel Islands National Park, California: National Park Service.
  16. ^ a b Roemer, G. W.; Donlan, C. J. & Courchamp, F. (2002). "Golden eagles, feral pigs, and insular carnivores: How exotic species turn native predators into prey". Proceedings of the National Academy of Sciences, USA. 99 (2): 791–796. doi:10.1073/pnas.012422499. PMC 117384. PMID 11752396.
  17. ^ a b "Home Page". Nps.gov. Channel Islands National Park's Island Fox. 13 August 2010. Retrieved 16 September 2011.
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  19. ^ Courchamp, F.; Woodroffe, R. & Roemer, G. (2003). "Removing protected populations to save endangered species". Science. 302 (5650): 1532. CiteSeerX 10.1.1.607.4608. doi:10.1126/science.1089492. PMID 14645839. S2CID 12119293.
  20. ^ Dawn, Karen (2008). Thanking the Monkey: Rethinking the way we treat animals (1st ed.). HarperCollins. p. 300.
  21. ^ Recovery of the Catalina Island Fox (Report). Avalon, California: Catalina Island Conservancy.
  22. ^ a b Armario, Christine (12 February 2016). "Feds: Remove 3 California Foxes from Endangered Species List". Los Angeles, CA. Associated Press. Retrieved 15 February 2016.
  23. ^ Sahagun, Louis (19 January 2012). "Catalina Island fox makes astounding comeback". Los Angeles Times. Retrieved 21 January 2012.
  24. ^ Chang, Alicia (21 September 2007). "Study: Catalina bison aren't purebred". USA Today. Associated Press. Retrieved 14 March 2008.
  25. ^ San Clemente Island Range Complex Environmental Impact Study (PDF) (Report). United States Navy. 2000. Archived from the original (PDF) on 6 February 2007. San Clemente Loggerhead numbers on the increase
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  27. ^ Kohlmann, S. G.; et al. (2003). Island fox recovery efforts on Santa Catalina Island, California, October 2001 – October 2002. Ecological Restoration Department (Report). Annual Report. Avalon, California: Santa Catalina Island Conservancy.
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Island fox: Brief Summary

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The island fox (Urocyon littoralis) is a small fox that is endemic to six of the eight Channel Islands of California. There are six subspecies, each unique to the island it lives on, reflecting its evolutionary history. They are generally docile, show little fear of humans, and are easily tamed. Island foxes played an important role in the spiritual lives of native Channel Islanders. They have been likely semi-domesticated as pets, used as pelts, or for other functions, like pest control.

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