The Arctic fox is related to wolves, dogs and other foxes because they are all members of the Canidae family. The Arctic fox's average weight of 3.5 kg (8 lb.) is comparable to that of a large domestic cat. Its total length (including its tail) ranges from 80 to 110 cm (2.5 to 3.5 ft.). Arctic foxes are the only canine species that changes its coat colour with the season. The very dense, white winter fur is superbly insulating and thickly covers almost all of the body including the pads of the feet. Arctic foxes wont even shiver until temperatures reach -70°C. Their summer coat is shorter and in shades of brown and tan to help them blend with the landscape. Lemmings, which are small rodents, are their main prey. Lemming populations fluctuate depending on the weather, and when their numbers crash so to do the fox numbers. When lemmings are scarce, Arctic foxes are forced to travel great distances to find enough alternative food such as birds, bird eggs, fish and carrion (animals that died or were killed by other predators). Arctic foxes will even cache food during times of abundance for use when food is in short supply. Pups are born in late spring, deep in a burrow dug by both parents. Both parents care for the young but the female is the main caregiver. Males spend most of their summer hunting diligently to supply the growing pups. Arctic foxes are good swimmers. Their main enemies are wolves, polar bears and humans. If they can avoid these predators and find enough food, they may live 8 to 10 years. The Arctic fox was once one of the most important natural resources in Canadas Arctic region: their valuable fur was a major source of revenue for northern native peoples. The Arctic fox is found in northern Canada, as well as in Northern Europe, Asia and Greenland.