Phipps, 1774 - Polar bear
The polar bear is not substantially different from other bears in body form. It is similar in size to brown and grizzly bears (Ursus arctos), but is more slender, and has a long neck and elongated head. The ears are small, an adaptation to the cold. Large partially webbed paws on the front limbs are used for swimming. There are 5 digits on each foot, each with a non-retractable claw. Polar bears are covered with fur on all but the nose and the pads on the bottoms of the feet. The guard hairs overlaying the underfur are up to 15 cm long.
Generally, the pelage of polar bears is white, but (depending on lighting and condition) it can appear yellow, light brown, or light grey. The nose and skin are black.
The dental formula is I 3/3, C 1/1, PM 2-4/2-4, M 2/3.
Can be confused with
There should be no problem recognizing polar bears. In the few areas where grizzly, brown, or American black (Ursus americanus) bears are found within the polar bear's range, the much lighter colour of the polar bear's fur will make it unmistakable. It should be noted that grizzly, brown, and black bears can be seen swimming, with only their heads up. Careful attention to coloration and head shape should eliminate any confusion. Also note, at a distance a bear's head could be confused with that of a pinniped, especially if conditions are sub-optimal for viewing.
Males may be up to 250 cm long and weigh 800 kg. Females reach lengths and weights of 200 cm and 300 kg, respectively. At birth, the tiny cubs weigh only about 0.6 kg.
Polar bears have a circumpolar distribution in the Northern Hemisphere. Their southern limits fluctuate with the ice cover (they have been recorded as far south as the Pribilof Islands in the Pacific and Newfoundland in the Atlantic). The northernmost record is from around 88°N. Polar bears are generally associated with sea ice, but they have been seen swimming at sea many kilometres away from the nearest land.
Biology and Behaviour
Polar bears tend to be solitary, but breeding pairs and females with up to 3 cubs may be seen together. They also aggregate in areas of great food concentrations. These bears can swim rather well, using their large webbed paws. They sometimes spend significant periods of time on land.
Mating occurs from April to June. Each male may mate with 1 or several females. In November to December, the pregnant female excavates a den, where the 1 to 3 cubs are born in December and January.
The primary diet of polar bears consists of ringed seals, but they also take bearded, harp, and hooded seals, and rarely walruses and white whales. These bears sometimes eat arctic cod and other forms of animal and vegetable matter.
There is a long history of hunting, both commercial and subsistence, of the polar bear, mostly for meat and hides. There is active management in several areas, and most stocks are stable or increasing.