Polar Bear (Ursus maritimus): Facts, Habitat and Diet

What does a polar bear look like?

A polar bear has a long neck, a fairly narrow head and a straight or slightly “Roman-nosed” profile, which make it look more streamlined than its close relative the brown bear. It lacks the brown bear’s big shoulder hump, and its ears are small and rounded to reduce heat loss.

The coat looks white, cream or yellowish, but each guard hair is actually transparent and hollow. Underneath is black skin and a layer of fat up to about 10 cm (4 in) thick. The paws are huge, up to about 30 cm (12 in) across, with furred soles and small bumps that grip the ice. The front paws are broad and act like paddles in the water. The short, strongly curved claws are made for holding prey rather than digging. The full story of the fur is in are polar bears really white?

How big is a polar bear?

Polar bears show a big difference between the sexes. Adult males are often twice as heavy as females, and all bears change weight through the year, gaining fat in spring when seal pups are plentiful and losing it during summer fasts.

A pregnant female fattened for her winter den can weigh up to about 500 kg (1,100 lb). A large male standing on his hind legs can reach roughly 3 m (10 ft). The heaviest polar bear on record, reportedly about 1,000 kg (2,200 lb), was a male killed in northwestern Alaska in 1960, but this figure has never been independently verified. Size records and the comparison with Kodiak bears are covered in how big are polar bears?

Where do polar bears live?

Polar bears live only in the Arctic, around the North Pole, in five countries: Canada, the United States (Alaska), Greenland, Norway (Svalbard) and Russia. Canada holds roughly two-thirds of the world’s polar bears. The southernmost bears live around James Bay and Hudson Bay in Canada, below 55° north, where the sea freezes every winter even though the summers are warm.

Their real home is sea ice rather than land. Polar bears prefer annual ice over shallow continental shelves and between islands, where cracks (leads) and open patches of water (polynyas) let seals breathe. These productive waters are sometimes called the “Arctic ring of life”. Bears follow the ice as it grows and shrinks, and individual home ranges can cover from a few thousand to tens of thousands of square kilometers a year. When the ice melts, some bears follow it north while others, such as those in Hudson Bay, wait on land until it refreezes.

Scientists divide the world’s polar bears into about 19 subpopulations, such as Western Hudson Bay, the Southern Beaufort Sea and the Barents Sea. Polar bears do not live in Antarctica, where penguins live instead

What do polar bears eat?

The polar bear is the most carnivorous of all bears. Its main prey is the ringed seal, the most common seal in the Arctic, followed by the larger bearded seal. In some areas bears also take harp, hooded and spotted seals, young walruses, and occasionally beluga whales or narwhals trapped in small openings in the ice.

The most common hunting method is still-hunting: a bear waits motionless beside a seal’s breathing hole, sometimes for hours, then grabs the seal when it surfaces. In spring, bears sniff out ringed seal pups in snow lairs on the ice and break through the roof with their front paws. They also stalk seals resting on the ice, creeping forward low to the ground before a final rush.

Polar bears eat mostly the blubber and skin, which give the most energy, and leave the rest for Arctic foxes, ravens, gulls and younger bears. They also scavenge whale carcasses and, during summer on land, eat birds, eggs, kelp, berries and carrion, although these foods cannot replace seals. See what do polar bears eat? for the full diet.

Swimming and life on the ice

Polar bears are powerful swimmers. They paddle with their broad front paws, steer with their hind legs and can stay underwater for up to about three minutes. Satellite-collared females in the Beaufort and Chukchi seas made dozens of swims longer than 50 km (31 mi), and one swam about 687 km (427 mi) over nine days in 2008. More in how far can polar bears swim?

On land and ice, polar bears usually walk slowly, at about 5.5 km/h (3.4 mph), to save energy and avoid overheating. They can sprint at roughly 40 km/h (25 mph) for a short distance. Most bears are active all year, and they sleep around seven to eight hours a day, often in a pit dug in the snow on the sheltered side of a pressure ridge.

Behavior and social life

Adult polar bears are mostly solitary. The main exceptions are mothers with cubs and pairs during the mating season. On land in late summer and autumn, though, bears can be surprisingly tolerant of each other. Near Churchill, Manitoba, adult males gather along the coast and often play-fight, rearing up and pushing each other in slow-motion wrestling matches.

Bears are ranked by size, with big adult males at the top. They communicate with body posture, huffs, jaw pops, growls and chuffing, a soft pulsing call a mother uses to keep in touch with her cubs. They also leave scent from their footpads in their tracks. Their sense of smell is excellent and helps them find seals under snow and ice.

Reproduction and life cycle

Polar bears mate on the sea ice from about March to May. A male may follow a female’s tracks for many kilometers and then guard her for a week or more. As in other bears, the fertilized egg does not implant in the womb until autumn, a process called delayed implantation.

In October or November the pregnant female digs a maternity den in a snowdrift, usually on land near the coast and sometimes on sea ice. There she gives birth between about November and January, usually to two cubs (one to three). Newborn cubs weigh only about 600 g (21 oz) and are blind and lightly furred. They nurse on milk that is around 30% fat and leave the den in March or April weighing about 10–15 kg (22–33 lb). By then the mother may have gone eight months without eating.

Cubs stay with their mother for about two and a half years, learning to hunt seals. Females usually have their first litter at about five or six years old and breed only every three years or so, which makes polar bears one of the slowest-breeding mammals.

Lifespan, predators and threats

Wild polar bears can live 25–30 years, although most die younger, and the oldest known wild bears were in their early 30s. In captivity they have lived past 40. Adults have no natural predators apart from other polar bears; big males sometimes kill cubs, and walruses can injure bears that attack them. The greatest natural danger is starvation, especially for young bears that have just left their mothers.

The main threat today is climate change. Polar bears need sea ice to hunt seals, and as the Arctic warms, the ice breaks up earlier in summer and forms later in autumn. Bears must then spend longer on land with little food, and long-term studies in Western Hudson Bay and the Southern Beaufort Sea link shorter ice seasons with thinner bears, lower cub survival and population declines. Other threats include pollution, as long-lived chemicals such as PCBs build up in the bears’ fatty tissue, oil and gas development, and conflict with people in Arctic towns.

Conservation status

The IUCN Red List classifies the polar bear as Vulnerable (2015 assessment), with an estimated total population of about 22,000–31,000 bears and an unknown overall trend. The listing is based on the projected loss of sea ice habitat. In the United States the species has been listed as threatened under the Endangered Species Act since 2008, and Canada lists it as a species of special concern.

In 1973, the five polar bear countries signed the Agreement on the Conservation of Polar Bears, which ended unregulated commercial hunting and committed them to protecting habitat. Inuit and other Indigenous peoples continue a regulated subsistence harvest in some areas. Population trends and estimates are explained in how many polar bears are left?

Polar bears and people

Polar bears are central to the cultures of Arctic peoples. The Inuit name is nanuq, and the bear features in stories, art and traditions across the Arctic. For people in Arctic towns, polar bears are also a real safety concern. Attacks are rare but can be serious, and most are by hungry young bears.

Churchill, Manitoba, calls itself the polar bear capital of the world. Each October and November hundreds of bears gather nearby to wait for Hudson Bay to freeze, and visitors watch them from special tundra vehicles.

Myths and facts

• Myth: polar bears cover their black noses with a paw when hunting. Fact: this story goes back centuries, but biologists who have spent decades watching polar bears hunt have found no reliable evidence for it.
• Myth: polar bears and penguins live together. Fact: polar bears live only in the Arctic and wild penguins only in the Southern Hemisphere, apart from the Galápagos penguin at the equator.
• Myth: polar bear hairs carry sunlight to the skin like optical fibers. Fact: measurements in the late 1990s showed the hairs absorb most ultraviolet light instead of channeling it to the skin.