THE BERING ISLANDS ARCTIC FOX

A small fox, with a relatively compact body, short legs, round ears and a short snout. A large subspecies of Arctic Fox, similar to Pribilof Arctic Fox (pribilofensis), with more luxuriant fur than mainland subspecies. Individuals from Mednyi Island are larger than those from Bering Islands. Coat is thick and dense in winter, with a majority of this fur being fine underfur. Summer coat is thinner. Blue morph predominates, and white individuals are extremely rare. Coat is a uniformly diffuse brownish gray tinged with a blue sheen in winter, changing to brownish dusky in summer, usually darkest on top of head and rump, with face and legs mixed with white hairs, and ears strongly edged with white. Yellow eyes, with elongated pupils. Thickly haired feet. Tail is long and bushy. Females are slightly smaller than males, with 6 to 7 pairs of mammae.

About the species

Reproduction and behavior

Gestation: 52-54 days.
Young per birth: 1-13, usually smaller litter than mainland subspecies.
Weaning: 28-35 days.
Sexual maturity: 12 months.
Life span: Around 10 years.
Breeding season: Early September to early May.

Dens are located under stones, in scree, and in crevices, mainly on elevated points, attached to the coastline and less frequently situated deep in the tundra. Dens are used for many years and have many entrance holes, and numerous paths connect breeding burrows with dens and shelters, and stretch to rich feeding areas within each home range. Conspicuous mounds, resulting from the accumulated scent posts, concentrate in the tundra around breeding burrows. Young disperse over shorter distances than mainland subspecies, with male dispersing farther than female.

Families comprised of 1 male and up to 4 female; a single male may have a home range encompassing 2 breeding dens, each with a female group including 1 or 2 lactating female and 1 female helper. In most families, there is 1 helper, a non-reproductive female. Polygyny is more common than in mainland subspecies.

Diet and interaction with the environment

On both islands, in summer, they feed on colonies of sea birds the most intensively; they also turn to abundant and easily accessible sources of food, such as corpses of whales and other sea mammals beached by the sea or food dumps near human settlements. Main predators: None. They show a system of territorial defense, which is seen also in other subspecies, characterized by display, mobbing and direct aggression against an intruder, combined with territorial barks, expressive postures and urine and feces markings, performed many times a day during the breeding season and if provoked by meetings with foxes or human intruders. Home ranges along the seashore average 2.0 km2, much smaller than in mainland subspecies. Owing to the small home ranges, neighboring families are at short distances and barking is used frequently as communication within and between family groups. They display little fear of people.

Habitat:

Native to Russia, restricted to the Commander Islands (Bering and Mednyi Islands) in the Bering Sea. On Mednyi Island, they are largely restricted to a narrow strip along the coastline where food sources are concentrated. The habitat conditions of this island subspecies differ sharply from the continental ones: there are no other native land predators on the islands, the climatic conditions are quite mild, and food resources are stable and highly productive.

Conservation status: Concern. Until the mid-20th century, the population on Mednyi Island remained stable at about 1,000 foxes but crashed in the late 1970s due to epizootic mange. Currently the population consists of less than 100 individuals. In contrast, the Bering Island population has not suffered serious declines, and population remains stable, at about 600 adult foxes.