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 The polar bear inhabits the tundra and seacoast of Russia, Norway, Greenland, Canada, and Alaska. At 11-1/2 feet from nose to tail and weighing over 2,000 pounds, a large male may be the biggest land carnivore on the planet today. The current population is estimated at 20,000 to 40,000. They have been a species of "special concern" since 1965, and are protected over most of their range. Indigenous people of Greenland and Alaska are allowed to hunt a few for subsistence and to carry on their traditions.
Closely related to brown and grizzly bears, polar bears evolved after they were isolated by glaciers during the mid-Pleistocene some 100,000 to 250,000 years ago. They are superbly adapted to the environment suggested by their scientific name, Ursus maritimus, which means "sea-going bear." They have long necks with small heads, plus long front legs with huge forepaws, for better swimming. Even their hollow, air-filled hairs help improve their buoyancy, while also insulating them from the Arctic cold.
 Tremendous swimmers, they can cover up to 60 miles without rest, and remain submerged for two minutes. These abilities are used to hunt their prey, primarily seals, plus fish and birds. When the ice melts in the summer, land-locked bears supplement their diet with carrion, crabs, rodents, bird eggs, even berries. Females especially need to keep up their body weight. They den in the fall and bear their cubs while hibernating. By spring, the mothers may lose up to 40% of their body weight.
 Cubs are born in litters of one to four, averaging two. Blind, hairless, and toothless at birth, they are about the size of a chipmunk. They grow rapidly on their mother's high-calorie milk, which contains over 40% fat.Weaned during their first year, cubs stay with their mother for about 2-1/2 years. Adolescent mortality is high in the harsh environment, with starvation, disease, injury, and predation by male bears being the chief dangers. If they survive to adulthood, their lifespan in the wild can be 25 years or more.
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