Polar bears are completely covered by fur—except for the tips of their noses. Even the pads of their feet may be furry for better traction in late winter. Their fur and its dense undercoat are actually without pigment but appear white. Their skin, noses, eyes, and claws are black.
Newborns may weigh as little as 1.3 pounds at birth. They are nearly hairless and can’t see, but they grow very fast. By the time cubs leave the den in the spring, they will weigh as much as 45 pounds and, at one year, they will weigh in at about 220 pounds.
Some full-grown males have been estimated at nearly 1800 pounds; these bears may stand five feet at the shoulder and more than 13 feet tall when they rise on their hind legs.
Polar bears (Ursus maritimus) live only in the Northern Hemisphere, in areas where the seas are ice-covered for much of the year. They are common in:
Chukchi and Beaufort Seas north of Alaska
East Siberian, Laptev, and Kara Seas of Russia
Barent's Sea of northern Europe
The northern part of the Greenland Sea Baffin Bay, which separates Canada and Greenland and through most of the Canadian Arctic Archipelago
The bears remain on the sea ice year-round or visit land only for short periods. Throughout the hemisphere, the bears spend their summers concentrated along the edge of the persistent pack ice. Significant northerly and southerly movements depend on seasonal melting and refreezing of the ice near shore.
Polar bears usually dine on seals but they have also been known to kill much larger animals such as walruses and belugas. Only the pregnant females enter dens for the entire winter. Other members of the population continue to hunt on the sea-ice throughout the winter.
Human activities and habitat alterations associated with industrial development can interfere with the movement, feeding, and breeding patterns of polar bears and may result in exposure to contaminants.
Larger concerns loom on the horizon, however. Evidence that the average temperatures of the globe are increasing continues to mount and the extent of the sea-ice in the Northern Hemisphere has declined from 4.8 million to 4.4 million square miles during the past 25 years.
Reductions in the amount of time polar bears can spend hunting on the sea-ice are beginning to show in their southern habitat. As the ice of Hudson Bay, for example, melts earlier in summer, the body weights of female polar bears and numbers of independent yearlings have declined.
Polar bears are so closely tied to the presence of the sea-ice platform from which they hunt, mate, and carry on other life functions that continuing extensive declines in ice coverage will restrict their productivity and could ultimately threaten their survival.