Channel Island Fox Background and Recovery

On four islands off the coast of California one can find the only carnivore which is unique to the state. This is the Channel Island fox, a cat-sized carnivore that colonized the islands approximately 10,000 years ago.

Even given its relatively small stature, the Channel Island fox is still the island group's largest native carnivore. Its diverse diet is well adapted to the varied terrains it inhabits.

Unfortunately a variety of manmade threats have left thefox's populationdrastically reduced.

General History

The island fox (Urocyon littoralis) once lived in large numbers on six of southern California's eight Channel Islands. However, years of livestock grazing replaced native brush with open grassland, exposing the fox to new predators such as golden eagles, which had moved onto the islands after DDT had eliminated the bald eagle population.

Due to precipitous declines in the island foxes that began in the 1990s, intensive recovery efforts including a captive breeding program began on several of the islands in 1999. The populations on the northern Channel Islands are poised at the brink of extinction due to predation by golden eagles. After a recent population crash, Defenders of Wildlife has devoted more energy to protecting this endangered animal.

The island fox is a habitat generalist, occurring in valley and foothill grasslands, southern coastal dunes, coastal bluff, coastal sage scrub, maritime cactus scrub, island chaparral, southern coastal oak woodland, southern riparian woodland, Bishop (Pinus muricata) and Torrey pine (Pinu torreyana) forests, and coastal marsh habitats.

Island specifics

Each subspecies of island fox inhabits a separate island. The subspecies are: Santa Cruz Island Fox (U.I. santacruzae), San Miguel Island Fox (U.I. littoralis), Santa Rosa Island Fox (U.I. santarosae) and Santa Catalina Island Fox (U.I. catalinae) (USFWS, 2004).

Status

In 2004, the U.S. Fish and Wildlife Service officially listed four subspecies of the island fox – the Santa Cruz Island fox, San Miguel Island fox, Santa Catalina Island fox, and Santa Rosa Island fox – as endangered under the Endangered Species Act.

The listing is based on a finding that the subspecies are likely to become extinct in the foreseeable future throughout all or a significant portion of their ranges. The primary reason for listing the San Miguel, Santa Rosa, and Santa Cruz foxes is the decline due to predation by golden eagles, which were initially drawn to the islands by the presence of non-native pigs. The Santa Catalina Island foxes were listed due to population decline following the rapid spread of canine distemper, which is transmitted by pet dogs.

Arrival onto the Islands

Island foxes are found on the six largest islands off the coast of southern California. Genetic evidence suggests that all island foxes are descended from one colonization event (Gilbert et al. 1990). One theory is that island colonization came about through chance over water dispersal when foxes rafted over on floating debris (Moore and Collins 1995).

The island fox is relatively docile and shows little fear of humans. Although primarily nocturnal, it is more diurnal than the mainland gray fox (Collins and Laughrin 1979; Fausett 1993). Federal Register Listing Channel island Fox.

Genetic implications of island species

In general, island forms of species generally have less genetic variability than their mainland counterparts (Gill 1980). The smaller the island size the lower the island fox population size and genetic variability seems to be. The smallest island fox populations, San Miguel and San Nicolas, show the least genetic variability. San Nicolas has virtually no genetic variability, which is highly unusual among mammal populations