Polar bears are huge, whitish or yellowish, marine bears that are well adapted to life in and around the icy Arctic Ocean. They are relatively slender bears, with a longer neck and head than brown bears. The individual hairs of their thick fur are transparent; it is reflected sunlight that makes their coat appear white. Oddly, their skin is black. Any sunlight that gets through its fur is absorbed by the black skin, helping to keep the animal warm. Polar bears swim by paddling their furry, slightly webbed front feet and steering with the back feet.
Polar bears hunt by wandering extensively over the sea ice, often moving from ice floe to floe, and sometimes swimming for hours in the cold water. They do this to find good places for hunting their favorite food, the ringed seal (Phoca hispida). Their claws are longer than those of other bears, and are used to grasp their seal prey as it rises out of the water at a breathing hole or along the edge of an ice floe. During the spring, polar bears break into the snowy dens where female seals have given birth to their young.
Polar bears may congregate in areas where ice floes move freely in the wind, because seals are more easily obtained in that habitat. Polar bears will tolerate each other if they find a stranded whale carcass, or if a walrus has been killed. During the summer, when the ice is gone from the mainland coast, polar bears may move onto the land and feed on berries, or they may fast. They may also be attracted to garbage dumps near towns, where there can be dangerous encounters with people.
Polar bears are usually solitary animals, coming together only to mate in late spring (March-June). One to three cubs are born in December or January in a snow den constructed by the mother. The cubs average about
23 oz (650 g) at birth, but weigh 20 lb (9 kg) or more when they emerge from the den in April. This rapid weight gain is possible because the milk of the sow contains more than 30% fat. The cubs stay with their mother for at least two years, learning to hunt and defend themselves. At that time the mother will mate again. Young females become sexually mature at five years of age. Polar bears live to be 20 or more years old.
Five countries have populations of polar bears: the United States (Alaska), Canada, Denmark (in Greenland), Norway, and Russia. These nations are cooperating in the management of their polar bears, allowing only a tightly controlled hunt. The hunt is mostly carried out by aboriginal people, who eat the bear meat and sell the valuable hides.