Vulpes lagopus

The Arctic fox (Vulpes lagopus), 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. It has a deep thick fur which is brown in summer and white in winter. Its body length ranges from 46 to 68 cm (18 to 27 in), with a generally rounded body shape to minimize the escape of body heat.

The Arctic fox preys on any small creatures it can find, including lemmings, voles, ringed seal pups, fish, and seabirds. It will also eat carrion, berries, and seaweed. Arctic foxes form monogamous pairs during the breeding season and usually stay together in family groups of multiple generations in complex underground dens.

http://en.wikipedia.org/wiki/Arctic_fox