Polar Bear

The polar bear (Ursus maritimus, Latin for 'sea bear') is the largest living species of bear and land carnivore. Adult males typically measure 200-250 cm in length and weigh 300-800 kg, while females are considerably smaller at 180-200 cm and 150-300 kg. The fur appears white or yellowish, the skin beneath is black, and a thick layer of fat - up to 10 cm deep - sits under the skin for warmth and energy.

Polar bears live across the Arctic, with their range covering Greenland, Canada, Alaska, Russia and the Svalbard Archipelago of Norway. They live both on sea ice and on land, preferring the annual sea ice, and are considered marine mammals because of their dependence on marine ecosystems. Polar bears have been kept in captivity in zoos and circuses, and in earlier centuries by royals and elites.

The polar bear lineage diverged from brown bears somewhere between 600,000 and over one million years ago, shaped by glaciation events over hundreds of thousands of years. The two species remain closely related and can still interbreed, though large-scale hybridisation appears to have stopped around 200,000 years ago. The oldest known polar bear fossil - a jaw bone - dates to between 110,000 and 130,000 years ago and was found in Norway.

Humans have hunted polar bears for at least 8,000 years, as shown by archaeological remains at Zhokhov Island in the East Siberian Sea. Indigenous Arctic peoples harvested them for fur, meat, fat, bones and teeth, and killing one was considered a rite of passage in some cultures. Polar bear furs were traded in Europe from the Middle Ages, large-scale hunting at Svalbard took place from at least the 18th century, and over 150,000 polar bears were killed or captured in Russia and Svalbard between the 18th and 20th centuries. In the mid-20th century, countries began to regulate polar bear hunting, culminating in a five-nation agreement in 1973 that banned most harvesting.

Polar bears are mostly solitary animals, though they gather more closely on land and can form loose groups around food sources. A dominance hierarchy exists, with the largest adult males at the top. Adult males can be surprisingly tolerant of one another outside the breeding season and have been recorded forming stable alliances, travelling and resting together.

They are generally quiet animals but do communicate through a range of sounds. Mothers make soft chuffing calls, presumably to stay in contact with cubs, while cubs cry for attention and hum while nursing. More hostile encounters produce growls, roars, jaw pops and huffs. Polar bears also communicate chemically, secreting scent from their foot pads into their tracks.

Most polar bears are active year-round - only pregnant females hibernate. They are generally diurnal, most active early in the day, and sleep around eight hours on average. They are powerful swimmers, capable of sustaining swims averaging over 150 km, and can run at up to 40 km/h on land, though they usually move at a gentle 5.5 km/h.

Polar bears can live up to 30 years in the wild. Adult bears have a high survival rate once fully grown, though adult males frequently carry scars from fights over mates.

Polar bears are especially susceptible to Trichinella, a parasitic roundworm contracted through cannibalism. They also accumulate high levels of persistent organic pollutants such as polychlorinated biphenyls (PCBs) and chlorinated pesticides, due to their position at the top of the food chain. Many of these chemicals have been internationally banned, and their traces have slowly declined in polar bears, though they persist and have even increased in some populations.

Climate change poses a growing health threat. Shrinking sea ice reduces access to seals, leading to malnutrition and starvation, particularly in cubs, juveniles and subadults. Insufficient nourishment also lowers reproductive rates in adult females. Subadult bears face a particularly difficult period, as they are less successful hunters and frequently have their kills stolen by larger bears.

This is general awareness only, not veterinary advice. If you find an injured or unwell wild animal, contact a vet or a wildlife rescue.

How big do polar bears get?

Polar bears are the largest land carnivores on Earth. Adult males weigh between 300 and 800 kg and can reach 200-250 cm in length, while females are much smaller at 150-300 kg. The largest polar bear on record, a male shot in Alaska in 1960, reportedly weighed 1,002 kg.

How long do polar bears live?

Polar bears can live up to 30 years in the wild. Their long lifespan and ability to keep producing young helps offset cub deaths within a population.

Are polar bears dangerous to humans?

Between 1870 and 2014 there were an estimated 73 attacks on humans, leading to 20 deaths. Most attacks involved hungry males, often subadults, rather than females. Despite a popular reputation as the most dangerous bear, polar bears are not considered more aggressive towards humans than other bear species.

Do polar bears really have hollow fur?

Yes - the outer guard hairs are hollow, which helps trap heat and also allows polar bears to float in water. The fur appears white due to the way it scatters light, not because it contains white pigment. Bears can take on a yellowish tint with sun exposure, which reverses after moulting.

Are polar bears endangered?

Polar bears are currently classified as vulnerable by the IUCN, with an estimated total population of 22,000 to 31,000 individuals. The biggest threats are climate change, pollution and energy development. The decline in sea ice gives polar bears less access to their favoured prey and increases the risk of starvation. Some subpopulations are thought to be declining, though others appear stable or have increased.

Do polar bears eat anything other than seals?

Seals - especially ringed seals - make up the bulk of a polar bear's diet, but they also hunt walruses, beluga whales, narwhals, reindeer, birds and fish. They rarely eat plant material as their digestive system is highly specialised for animal matter, though they have been recorded eating berries, moss, grass and seaweed.

The polar bear's scientific name, Ursus maritimus, is Latin for 'sea bear' - a fitting title for an animal that one study found swims for an average of 3.4 days at a time, covering an average of over 150 km.

A polar bear's guard hairs are transparent, and its fur appears white because of the way it scatters light and its lack of pigment. Underneath all that fur, the skin is completely black, which helps absorb heat from the sun.

Polar bears have been recorded as close as 25 km from the North Pole.

The Inuit name for the polar bear is nanook, and the Netsilik peoples have separate words for bears depending on their sex, age and behaviour - including specific terms for dormant bears, gestating females and newborns.

A polar bear's weight can fluctuate by as much as 50 percent across the year as it builds up fat reserves. A fattened pregnant female can weigh as much as 500 kg.