Bears: Ursidae

Physical characteristics: Polar bears, the largest land carnivores, have a thick white or yellowish coat, a long body and neck, black nose, and small eyes and ears. The front paws, webbed like a duck's feet, function as paddles for swimming. The long, sharp claws are used for grasping and killing prey. On average, adult males weigh about 900 to 1,300 pounds (400 to 590 kilograms) and stand 8 to 9 feet (2.4 to 2.7 meters). Adult females weigh about 450 to 600 pounds (200 to 270 kilograms) and stand 6 to 7 feet (1.8 to 2.1 meter).

Geographic range: Polar bears live in the icy Arctic Ocean and in the countries that extend into the ocean: United States (Alaska), Canada, Russia, Norway, and Greenland (a territory of Denmark).

Habitat: Polar bears prefer the Arctic pack ice, formed when big pieces of thick ice are frozen together. In summer, when the ice melts, they live on land, staying close to the water.

Diet: Polar bears eat mainly ringed seals and occasionally bearded seals. They also prey on walruses and belugas. In warmer months, they hunt ducks and rabbits, as well as feed on mussels, berries, and kelp, a brown seaweed.

Polar bears give birth to one or two cubs at a time. The cubs stay with their mothers for at least two and a half years. (John Swedberg/Bruce Coleman Inc. Reproduced by permission.)

Behavior and reproduction: Polar bears mostly keep to themselves but do not defend a particular home territory. They gather on shore to share beached whales and walruses. A bear may share its food with another if the latter begs submissively through body language, such as nodding its head. Polar bears are very tidy, washing themselves in the ocean after meals.

Polar bears mate in the spring. In the fall, after stuffing herself with food, the pregnant sow digs a den in deep snow and hibernates while awaiting childbirth. Cubs that are born in winter nurse until spring, with the mother living off the fat storage in her body. Cubs stay with their mothers for at least two and a half years.

Polar bears and people: Once hunted as trophies and for their fur and meat, polar bears are now protected by the laws of the five countries where they live.

Conservation status: Some scientists believe that, within a hundred years, polar bears may become extinct if Earth's temperature continues to rise. Warmer temperatures cause more arctic ice to melt, preventing the bears from hunting their primary food source, the ringed seals, on the sea ice. ∎