Polar bear

Classification and size

The polar bear (Ursus maritimus) is a mammal in the bear family Ursidae. A long neck and relatively narrow head give it a different profile from a brown bear. The United States Fish and Wildlife Service describes adult males as generally larger and heavier than females. The coat traps insulating air, and layers of fat help conserve heat and store energy. Broad paws distribute weight on ice and give the bear a large surface to push against the water when swimming.

Habitat and distribution

Polar bears live across the Arctic, including waters off Alaska, Canada, Greenland, Norway and Russia. Much of their hunting happens on sea ice, especially over shallow waters where seals are available. The ice changes through the year, and bears move as it forms, drifts and breaks up. In places with seasonal ice, bears may spend part of the year ashore. Pregnant females also use maternity dens, often in snow on land.

Diet and hunting

Polar bears depend heavily on seals, particularly ringed seals and bearded seals. A bear can wait beside a breathing hole for a seal to surface or approach one resting on the ice. Seal fat provides much of the energy a bear can store for a period when food is harder to find. How long the bear can hunt each season depends on when ice becomes available in its part of the Arctic.

Conservation

The IUCN lists the polar bear as Vulnerable globally. Loss of sea ice can shorten access to hunting habitat and lengthen the time bears must spend ashore or swimming between ice. Local conditions differ across the Arctic, so monitoring looks at separate populations. The U.S. Endangered Species Act lists the polar bear as Threatened, a designation under a different system from the global IUCN Red List.

Sources

• U.S. Fish & Wildlife Service — Polar Bear
• Alaska Department of Fish and Game — Polar Bear