Moving easily over ice and snow, and even capable of swimming when necessary, the Arctic fox is known for its far ranging movements, which exceed those of any terrestrial mammal except man. During the seasonal movements that occur in many populations during the autumn and winter, individuals have been recorded travelling over 800 kilometres from shore out over the pack ice (2), with a total of up to 4,500 kilometres over a winter season (5). In order to survive in the harsh Arctic environment, the Arctic fox hunts and scavenges a wide variety of prey according to location, including sea birds and ptarmigan, fish, marine invertebrates, and mammals, such as adult seal carcasses, as well as live ringed seal pups located in chambers beneath the snow (1) (2). The majority of this species’ diet, however, consists of lemmings, and its population can fluctuate greatly in response to annual changes in lemming abundance (1). While the basic social unit for the Arctic fox is the breeding pair, this species usually hunts alone, and may cache food for later use (3). It is also possible that additional adults stay within the den, with several breeding females nursing the offspring together (5). When food is not available, the arctic fox is able to reduce its metabolic rate by half, while remaining active, thereby conserving energy and allowing more time to find food before starvation occurs (2). While starvation is a significant cause of mortality for this species, both adults and young are preyed upon by the wolverine (Gulo gulo), the red fox (Vulpes vulpes) and golden eagle (Aquila chrysaetos) (3).
The Arctic fox breeds between February and May, with births taking place from April to July, following a gestation period of 51 to 54 days (2) (3). Litter size is dependent on food availability, with 5 to 10 young produced on average (1), but as many as 19 young in areas where food is particularly abundant (3). The young are born and nursed inside complex dens, which provide shelter and protection against predators (3). Some den sites are centuries old, used by numerous generations of foxes, and can become very large (2), with up to 150 entrances (3). Both parents contribute to the rearing of the young, with the female providing milk for the first three weeks and rarely leaving the den, while the male brings food. As the cubs begin to take more meat, the female also starts hunting, and in some cases, the pair is assisted by ‘helper’ individuals, which are usually the offspring from the previous year. The young become independent of the den at eight to ten weeks old and reach sexual maturity at ten months (3). During the breeding season Arctic fox pairs are strongly territorial, marking territory boundaries with urine, and employing vocalisations and postures, such as holding the tail erect, during disputes with conspecifics (3).