The polar bear is the largest living land carnivore in the world today, with adult males growing up to 2.6 meters in length. The most well known of all bears, the polar bear is immediately recognisable from the distinctive white colour of its thick fur. A polar bear is so well insulated that its body heat is virtually invisible to a heat sensor. The only unfurred parts of the body are the foot pads and the tip of its nose, which are black, revealing the dark colour of the skin underneath the pelt. The neck of the polar bear is longer than in other species of bears, and the elongated head has small ears. Polar bears have large strong limbs and huge forepaws which are used as paddles for swimming. The toes are not webbed, but are excellent for walking on snow as they bear non-retractable claws which dig into the snow like ice-picks. The soles of the feet also have small projections and indents which act like suction cups and help this bear to walk on ice without slipping. Females are about half the size of males.
Polar bears feed primarily on ringed seals. Bearded seals are taken less often than ringed seals, but are important prey items. Polar bears also eat harp seals and hooded seals, and they scavenge on carcasses of caribou, musk-oxen, whale, walrus (usually pups) and seal. They occasionally eat mammals such as Svalbard reindeer and lemmings, as well as birds, eggs, lichens, moss, berries, grass and kelp.
Population size & trend
|Estimated population size:||Estimated population size: 20,000 — 25,000|
Geographical range & habitat
The polar bear is found throughout the Arctic on ice-covered waters. There are no reports of polar bears in the vicinity of the North Pole itself. The northernmost location where they have been seen is about 160 km south of the North Pole, at 88°N latitude. The farthest south that polar bears live on a year-round basis is in James Bay (which is at about the same latitude as London) in Canada, where bears den at about 53°N latitude on Akimiski Island. They have also been recorded as far south as St. Mathew Island and the Pribilof Islands in the Bering Sea and Newfoundland in Canada, and they have occasionally been seen in the Gulf of St. Lawrence, Canada in years when heavy pack ice has been drifting farther to the south than normal (50°N latitude).
The favoured habitat of the polar bear is on the annual ice that lies adjacent to the continental arctic coastlines or island archipelagoes. They tend to avoid areas of multiyear ice such as that which characterizes much of the northerly portion of the polar basin, probably because the density of seals is very low there. On the ice, the bears are found near the edges of the ice or in areas where the ice regularly cracks open because of the wind and currents and then refreezes. Seals are more abundant in these areas, and they are accessible to the bears when the seals surface to breathe in narrow cracks or at breathing holes in patches of thin ice that have just frozen over.
|Female head-body length:||1.9 — 2.1 m|
|Male head-body length:||2.4 — 2.6 m|
|Female weight:||200 — 300 kg (when pregnant up to 500 kg)|
|Male weight:||400 — 600 kg|
|Cub weight:||up to 0.7 kg at birth|
|Age to maturity:||Age of first reproduction is normally 5 — 6 years for females. Most of the mating is probably done by males 8 — 10 years old and older.|
|Gestation period:||Relatively long (195−265 days) because of delayed implantation of the dividing fertilised ovum in the uterus.|
|Birth season:||Breeding from March to May; birth from late November to mid-January|
|Birth rate||The average litter size is less than two. Twins are most common in polar bears and account for about 2⁄3 of the litters.|
|Life span:||About 25 years for males and 30 years for females|
Changes in Polar bear productivity