Basic Facts About Polar Bears

Polar bears are among the largest carnivores in the world, rivaled only by the Kodiak brown bears of southern Alaska. As its scientific name, Ursus maritimus, suggests, the polar bear is primarily a marine bear.

© Paul Nicklen / National Geographic Stock

Numerous adaptations uniquely suit polar bears to life in icy habitats. Their fur is thicker than any other bears’ and covers even their feet, for warmth and traction on ice. A thick layer of blubber beneath their fur provides buoyancy and insulation.

The long neck and narrow skull of the polar bear probably aid in streamlining the animal in the water, and the front feet are large, flat and oarlike. The polar bear is an excellent swimmer and individuals have been seen in open Arctic waters as far as 200 mi (320 km) from land.

Diet

Staples: Polar bears feed almost exclusively on ringed seals and, to a lesser extent, bearded seals.
Polar bears travel great distances in search of prey.  They are also known to eat walrus, beluga whale and bowhead whale carcasses, birds, vegetation and kelp. 

Population

The World Conservation Union (IUCN) estimates that there are between 20,000-25,000 polar bears in the world.

Range

Polar bears are only found in the Arctic region and are highly dependant on the pack ice there since they spend much of their time hundreds of miles from land. The most important habitats for polar bears are the edges of pack ice, where currents and wind interact with the ice, forming a continually melting and refreezing matrix of ice patches. These are the areas of greatest seal abundance and accessibility.

Individual polar bears can travel thousands of miles per year following the seasonal advance and retreat of sea ice. Polar bears are distributed throughout the Arctic region in 19 subpopulations. Alaska, Canada, Russia, Greenland and Norway have polar bear populations.

Behavior

Polar bears are highly dependant on older stable pack ice in the arctic region, where they spend much of their time on the ice hunting, mating, and denning. They are generally solitary as adults, except during breeding and cub rearing.

Unlike brown bears, non-breeding polar bear females and males do not hibernate or den in the winter. Pregnant polar bears need to eat a lot in the summer and fall in order to build up sufficient fat reserves for surviving the denning period, during which time they give birth to one-pound cubs and then nurse them to about 20-30 pounds before emerging from the den in March or April.

Reproduction

Mating Season: Late March through May
Gestation: About 8 months with delayed implantation
Litter size: 1-4 cubs; 2 cubs most common
Female polar bears locate denning sites in October on thick stable pack ice or on land. The young are born from November through January while the mothers are hibernating. Cubs will remain with their mothers for at least 2 ½ years. Female polar bears can produce five litters in their lifetime, which is one of the lowest reproductive rates of any mammal.