Island Fox

The **island fox** (*Urocyon littoralis*) is a small fox that is native 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.

## Taxonomy and Evolution

The island fox shares the *Urocyon* genus with the mainland gray fox, 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 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.

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. 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.

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

## Description

The island fox is significantly smaller than the gray fox and is probably the smallest fox in North America, averaging slightly smaller than the swift and kit foxes. 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.[8] The island fox weighs between 1 and 2.8 kg (2.2 and 6.2 lb). The male is always larger than the female.[9] The largest of the subspecies occurs on Santa Catalina Island and the smallest on Santa Cruz Island.

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. 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 Islandpopulations. 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.

## 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.

## Ecology and Behavior

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, albeit 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.

The island fox is not intimidated by humans, although at first may show aggression. It is quite easy to tame and is generally docile. 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. Its main vocalizations are barking and growling. The island fox marks territory with urine and feces.

## Conservation Status and Federal Protection

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. As of 2013, the IUCN lists the entire species as near threatened, an improvement from its previous status of "critically endangered". A decline in island fox populations was identified in the 1990s. On San Miguel Island, the decline began in 1994, with the adult population falling from 450 to 15 in 1999. Similar population declines were discovered on Santa Cruz Island, where 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. In 2004, there were 38 San Miguel island foxes, all in captivity; 46 foxes in captivity on Santa Rosa Island and 7 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.

Golden eagle predation, discovered when foxes were radio-collared and monitored, proved to be the cause of the high mortality rates. 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. 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 decimation 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.