The polar bear is the largest land carnivore and has a reputation as the only animal that actively hunts humans.

Subspecies
None.

Life span
Up to 25 years.

Statistics
Body length: male: 240-260cm, female: 190-210cm. Weight: male: 400-600kg (rarely up to 800kg), female: 200-300kg. They are the largest species of bear and the largest land carnivore.

Physical description
Polar bears are large and stocky with hind limbs that are longer than the forelimbs, and a long neck. They have large, furry feet that act as snowshoes. Their creamy-white fur is dense and water-repellent, enabling them to shake dry after swimming.

Distribution
Polar bears are found throughout the circumpolar Arctic, south to Canada. They are the most northerly distributed species of bear.

Habitat
They spend most of their time on Arctic ice floes, and when they are on the shore they remain near the water.

Diet
Polar bears are predominantly carnivorous, and mainly feed on ringed seals and less so on bearded seals. A small part of their diet includes beluga, narwhal, walrus, fish, seabirds, reindeer and carrion. They also eat berries and various other vegetation in the summer months.

The main technique employed by polar bears when hunting seals is known as still-hunting. The bear waits at a breathing hole until a seal surfaces. It will then break through the snow and seize the seal with its jaws. Polar bears must spend over 50 per cent of their time hunting, and less than two per cent of attempts to catch seals are successful. Even in good hunting areas, a bear may catch only one seal every four or five days.

They have a remarkable sense of smell and can detect a carcass from 32km away.

Behaviour
They are usually solitary, except during the breeding season (midsummer), although they will sometimes aggregate to feed on large whale carcasses.

Polar bears are most active at night.
They are strong swimmers and have many adaptations for an aquatic environment - they are well insulated with fat, their nostrils close and their ears are held close to their head when underwater, plus their feet are partially webbed.

Annual home ranges vary from 5,180-300,400 square km. The variation depends on their location - bears that live in areas where the pack ice changes considerably need larger ranges than those in relatively stable habitats.

Only pregnant females enter dens over the winter, so that their cubs can be born in safety. Other polar bears remain active.

Reproduction
Polar bears mate between March and June and give birth to 1-3 cubs (very rarely 4) from November to January. The cubs are born blind and helpless with a thin layer of fur.

Conservation status
They are classified as Lower Risk - Conservation Dependent by the IUCN and are on CITES: Appendix II. They are hunted for meat and fur. Oil spills from drilling platforms or tankers are a potential threat.

Notes
Polar bears evolved from brown bears about three million years ago. Fossil remains of a large extinct subspecies (U.m.tyrannicus) were excavated at a site near London in 1964.

Polar bears are the most likely species to kill humans for food, as they assume anything they encounter is potential prey. Attacks by other bear species are usually due to the bear being startled, and they will rarely eat the body.