"An animal that does not begin to shiver until temperatures reach -70 C, the arctic fox is one of the most superbly cold-adapted mammals. Its dense, multi-layered coat, which is several inches thick during winter, provides excellent heat insulation. Short ears, a short muzzle, and short limbs reduce heat loss by minimizing the amount of body surface area exposed to the cold. Even the pads on the soles of the feet are covered with fur to insulate them. Arctic foxes change color seasonally. Most populations are grayish-brown in summer and white in the winter. Others are dark brown or blush-gray in summer and ""blue,"" a steely blue-gray, in the winter. Like other foxes, arctic foxes tend to be solitary and mostly nocturnal. They hunt for lemmings, voles, birds, and other prey in the summer, but scavenge for carrion during the harsh winter, sometimes following polar bears or wolves to feed on the remains of caribou or seals the larger predators have killed."

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Mammal Species of the World