Polar Bear

About the polar bear

The polar bear is a large bear native to the Arctic and the areas around it, closely related to the brown bear — closely enough that the two species can interbreed. It is the largest living species of bear and the largest living land carnivore by body mass. Males typically weigh 300–800 kg (660–1,760 lb) and measure 200–250 cm (6.6–8.2 ft) long; females run smaller, at 150–300 kg (330–660 lb) and 180–200 cm (5.9–6.6 ft). A fattened, pregnant female can weigh as much as 500 kg (1,100 lb), and the largest polar bear on record, shot in northwestern Alaska in 1960, reportedly weighed 1,002 kg (2,209 lb).

Compared with the brown bear, the polar bear has a more slender build: a narrower, flatter skull, a longer neck, a lower shoulder hump, and a curved, "Roman nose" snout profile. Its 34 to 42 teeth are adapted for a carnivorous diet, with longer, sharper, more spaced-out canines and smaller, more pointed cheek teeth than a brown bear has. The coat looks white but has no white pigment; it appears that color because of how light scatters off dense underfur about 5 cm (2.0 in) long and guard hairs about 15 cm (5.9 in) long, which are hollow and help the bear both trap heat and float. Underneath, the skin is black and absorbs heat, and a 5–10 cm (2.0–3.9 in) layer of fat provides both insulation and an energy reserve. Large, well-furred paws let the bear walk on ice and paddle through water, and small, hooked claws help it snatch prey and climb onto ice.

Polar bears range across the Arctic and nearby areas, including Greenland, Canada, Alaska, Russia, and Norway's Svalbard Archipelago, with individuals recorded as close as 25 km (16 mi) from the North Pole. Because there has been little human encroachment on this remote habitat, polar bears still occupy more of their original range than any other large land carnivore. Researchers divide the species into at least 18 subpopulations and, more broadly, into four genetic clusters spanning the Southern Canadian, Canadian Archipelago, Western Basin, and Eastern Basin regions.

Behavior and diet

Polar bears are considered marine mammals because of how dependent they are on the sea ice and the ocean beneath it. They prefer the annual sea ice, hunting there for seals — particularly ringed seals — which they typically ambush, either stalking prey across the ice or in the water, or waiting motionless at a breathing hole or the edge of the ice for a seal to surface. The bear feeds mainly on the seal's energy-rich blubber. Beyond seals, it also preys on walruses, beluga whales, and some land animals. A polar bear's weight fluctuates over the course of a year, as it bulks up on fat and can increase its mass by as much as 50 percent.

Polar bears are usually solitary, though they can be found in groups when they're on land. They travel widely to find food and mates: home ranges run from about 3,500 km2 (1,400 sq mi) to as large as 38,000 km2 (15,000 sq mi) a year, with drifting ice carrying them even farther. A bear typically covers around 12 km (7.5 mi) a day, walking at roughly 5.5 km/h (3.4 mph) on average, though it can run at estimated speeds up to 40 km/h (25 mph).

During the breeding season, males guard females and defend them against rival males. Mothers give birth to cubs in maternity dens over the winter, and the young stay with their mother for up to two and a half years.

Range and habitat

Polar bears live throughout the Arctic and immediately adjacent areas: Greenland, Canada, Alaska, Russia, and Svalbard. The southern edge of their range reaches James Bay and Newfoundland and Labrador in Canada, and St. Matthew Island and the Pribilof Islands in Alaska; they are not permanent residents of Iceland but do turn up there when sea ice lets them cross.

As a pagophilic, or ice-loving, species, the polar bear mainly inhabits annual sea ice over continental shelves and between islands, an environment researchers call the "Arctic Ring of Life" for its high biological productivity. Bears concentrate where sea ice meets open water, at polynyas and leads, to hunt the seals that make up most of their diet, and they shift their movements through the year as ice cover changes. When the summer ice disappears, they're forced onto land, where they use forests, mountains, rocky areas, lakeshores, and creeks. In the Chukchi and Beaufort seas, most bears still follow the retreating ice north each summer, though a growing share — 15 to 40 percent, a trend seen since the 1980s — now stays on land instead.

Conservation status

The polar bear is classified as Vulnerable (VU) by the IUCN, with an estimated total population of 22,000 to 31,000 individuals. Its biggest threats are climate change, pollution, and energy development. Climate change is shrinking the sea ice the species depends on for hunting, which cuts bears off from their preferred prey and raises the risk of malnutrition and starvation; it also pushes bears to spend more time on land, which increases conflict with people. Polar bears have also long been hunted, by both Indigenous and non-Indigenous people, for their coats, meat, and other products.