THE ARCTIC FOX

ABOUT THE ARCTIC SPECIES

The Arctic fox, also known as the white fox, polar fox, or snow fox, is a small fox native to the Arctic regions of the Northern Hemisphere and common throughout the Arctic tundra biome. It is well adapted to living in cold environments, and is best known for its thick, warm fur that is also used as camouflage. The Arctic fox preys on many small creatures such as lemmings, voles, ringed seal pups, fish, waterfowl, and seabirds.

Arctic foxes must endure a temperature difference of up to 90–100 °C between the external environment and their internal core temperature. To prevent heat loss, the Arctic fox curls up tightly tucking its legs and head under its body and behind its furry tail. Although the Arctic foxes are active year-round and do not hibernate, they attempt to preserve fat by reducing their locomotor activity.

Reproduction and behavior

Arctic foxes tend to select dens that are easily accessible with many entrances, and that are clear from snow and ice making it easier to burrow in. The Arctic fox builds and chooses dens that face southward towards the sun, which makes the den warmer. Arctic foxes prefer large, maze-like dens for predator evasion and a quick escape especially when red foxes are in the area. Natal dens are typically found in rugged terrain, which may provide more protection for the pups.

When red foxes are not in the region, Arctic foxes will use dens that the red fox previously occupied. Shelter quality is more important to the Arctic fox than the proximity of spring prey to a den. The main prey in the tundra are lemmings, which is why the white fox is often called the «lemming fox». When lemmings are abundant, the white fox can give birth to 18 pups, but they often do not reproduce when food is scarce.

The "coastal fox" or blue fox lives in an environment where food availability is relatively consistent, and they will have up to 5 pups every year. Arctic foxes are primarily monogamous and both parents will care for the offspring. When predators and prey are abundant, Arctic foxes are more likely to be promiscuous and display more complex social structures. On the coasts of Svalbard, the frequency of complex social structures is larger than inland foxes that remain monogamous due to food availability.

Diet and interaction with the environment

Arctic foxes generally eat any small animal they can find, including lemmings, voles, other rodents, hares, birds, eggs, fish, and carrion. In areas where they are present, lemmings are their most common prey, and a family of foxes can eat dozens of lemmings each day. In some locations in northern Canada, a high seasonal abundance of migrating birds that breed in the area may provide an important food source. Arctic foxes survive harsh winters and food scarcity by either hoarding food or storing body fat subcutaneously and viscerally.

Extreme adaptation

The Arctic fox lives in some of the most frigid extremes on the planet, but they do not start to shiver until the temperature drops to −70 °C . Among its adaptations for survival in the cold is its dense, multilayered pelage, which provides excellent insulation. Additionally, the Arctic fox is the only canid whose foot pads are covered in fur. The fur of the Arctic fox provides the best insulation of any mammal. Since less of its surface area is exposed to the Arctic cold, less heat escapes from its body.

One way that Arctic foxes regulate their body temperature is by utilizing a countercurrent heat exchange in the blood of their legs. Arctic foxes can constantly keep their feet above the tissue freezing point −1 °C when standing on cold substrates without losing mobility or feeling pain. Arctic foxes maintain the temperature in their paws independently from the core temperature. If the core temperature drops, the pad of the foot will remain constantly above the tissue freezing point.

ABOUT THE COMMON ARCTIC FOX

Reproduction and behavior

Gestation: 52 days.
Young per birth: 6-12, exceptionally up to 25.
Weaning: 28-42 days.
Sexual maturity: 10- 12 months.
Life span: 10 years.
Breeding season: April and May.

Newborns of both color phases are covered with short velvety dark brown fur, which becomes lighter and longer after the pups reach 2 weeks of age. Blue-phase pups acquire their characteristic dark color by the time they are 2 months old. They prefer to den in light, sandy soil along riverbanks, on small hillocks, and occasionally in talus. On the open tundra, dens are usually a mound 1-4m high. Social behavior: Monogamous pairs in the breeding season.

Diet and interaction with the environment

Lemming Foxes, typical of inland locations, have mostly white coats, migrate further and feed on lemmings and other small rodents; coastal Foxes live along the coasts of the Arctic, have mostly blue coats and feed on migratory birds, eggs, fish, seal carcasses and marine invertebrates. Main predators: Red Fox, wolverine, golden eagle, brown bear, wolf.

Mainly nocturnal, but their activity patterns are flexible depending on their prey. They may travel great distances during winter and traverse extensive pack ice fields. They may follow polar bears to scavenge kill remains. Territories are defended directly by chasing and mobbing and indirectly via scent marking and vocalizations, especially during the denning season. They scent mark by defecating on visually conspicuous or elevated landmarks such as rocks and eskers. Good swimmers. Common vocalizations include growls, barks and coughs, but also employ visual signs for communication.

Habitat

Arctic and alpine tundra, often near coasts. Native to Canada, Finland, Norway, Russia, Sweden, United States. Circumpolar distribution, including the Arctic and tundra zones of North America and Eurasia, parts of the alpine zones of Fennoscandia, and islands of the Arctic, North Atlantic and North Pacific Oceans. In North America, Arctic Foxes also occur on several Aleutian Islands in Alaska, where they were introduced for fur farming.

Conservation status: Least Concern. Regional status: Critically Endangered (Norway), protected by law in Finland, Sweden and Norway. It is fairly abundant in North America. The release of many Arctic Foxes to over 450 islands in Alaska had catastrophic effects on island avifauna populations.