“Polar bear fur is hollow and looks white, but the skin underneath is black.”
Polar bears are the largest land carnivores on Earth and live on Arctic sea ice. They hunt seals, swim long distances, and depend on cold ocean ice to survive.
By An Nguyen · Published · Updated
Ursus maritimusCarnivoraUrsidae
Browse images of polar bear across habitat, behavior, anatomy, and life stages, including a circumpolar range map.
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Core article
A closer look at habitat, diet, behavior, reproduction, and conservation.
The polar bear (Ursus maritimus) is the largest living land carnivore, but it is really a creature of the sea ice. The frozen surface of the Arctic Ocean is where it hunts the seals its whole body is built to catch — so when the ice retreats, the bear's way of life retreats with it. It is closely related to the brown bear yet differs sharply in diet, shape, and habitat; see polar bear vs. grizzly bear, and why polar bears need sea ice for how ice, seals, and fasting fit together.
The polar bear is a hypercarnivore — its diet is more strictly meat than any other bear's — and it runs on fat. Ringed seals are the mainstay, with bearded seals, the odd harp seal, and walrus calves added when available. Catching them takes patience and an extraordinary nose: a polar bear can smell a seal's breathing hole under three feet of snow from nearly a mile away.
Its main method is "still-hunting" — waiting motionless beside a breathing hole, sometimes for hours, then hauling the surfacing seal out with a forepaw. It also uses its pale coat to stalk seals resting on the ice, creeping forward and freezing whenever the seal lifts its head. Seal blubber is so energy-dense that the land foods bears fall back on in summer — carcasses, eggs, small mammals, kelp — cannot replace it for long.
Polar bears are circumpolar, ranging across the Arctic in five nations: Canada (most of the world's bears), the United States (Alaska), Greenland, Norway (Svalbard), and Russia. Sea ice is the defining feature of their world — a hunting platform, a travel highway, and a place to find mates. They favour the dynamic zones where ice meets open water or fractures into leads and polynyas, because that is where seals concentrate. As the ice grows and shrinks with the seasons, bears migrate to stay over the best hunting.
A polar bear's fur is not white. The guard hairs are pigment-free and hollow, scattering light so the coat looks white and camouflages the bear against snow, while the skin beneath is black to absorb heat. Under that double coat lies a blubber layer up to 4.5 inches thick that both insulates against frigid water and stores energy for fasts. Boars (males) run 6 to 9 feet long and 550 to 1,700 pounds; sows (females) are smaller. The build is made for power and swimming: an elongated neck and narrow skull to reach into breathing holes, and paws up to 12 inches across that spread weight like snowshoes and paddle like oars, their soles textured for grip on wet ice.
Polar bears are solitary and nomadic, ranging alone across huge, ice-dictated territories except when breeding or raising cubs. They are not strongly territorial, and when a big food source such as a whale carcass appears, bears will tolerate one another in tense aggregations ordered by size, with the largest males dominating.
They are powerful swimmers, holding about 6 mph and documented crossing hundreds of miles of open water between floes. On land they can sprint up to 25 mph in short bursts, but their heavy insulation makes them overheat fast, so they avoid sustained exertion.
Mating happens on the spring ice. The fertilized egg then pauses — delayed implantation — while the female spends summer building fat. In autumn a pregnant female digs a maternity den in a snowdrift, the embryo implants, and she gives birth mid-winter while living entirely on her reserves; total gestation including the delay is about eight months.
Cubs, usually 1 to 3, are born blind and barely a pound, nursing on rich milk in the den. The family emerges in spring after the mother has fasted for up to eight months. Cubs stay with her about two and a half years, learning to hunt seals and read the ice, while she guards them — including from adult males, which sometimes kill cubs. Wild polar bears typically live 20 to 25 years.
Polar bears split from brown bears only about 400,000 to 500,000 years ago, when a group became isolated in the cooling north and traded omnivory for a fat-and-meat diet on the ice.
| Polar bear | Brown bear | |
|---|---|---|
| Diet | hypercarnivore (mostly seals) | omnivore (plants, fish, meat) |
| Habitat | Arctic sea ice and coasts | forests, tundra, mountains |
| Coat | hollow, light-scattering | brown, various shades |
Because the split is so recent, the two can still interbreed where their ranges now overlap, producing fertile "pizzly" or "grolar" hybrids.
The polar bear is listed as Vulnerable with a declining trend, and its overriding threat is climate change. The Arctic is warming faster than the rest of the planet, and the longer open-water summers force bears into extended fasts on land. Poorer body condition means lower reproduction and higher cub mortality, and scientists project that many regional populations could disappear this century if warming continues.
Retreating ice brings secondary threats as it opens the Arctic to shipping and to offshore oil and gas, raising the risk of spills and noise. Persistent pollutants carried north on air and ocean currents also build up in the fatty tissues of top predators like the polar bear.
Kingdom
Animalia
Phylum
Chordata
Class
Mammalia
Order
Carnivora
Family
Ursidae
Genus
Ursus
Species
U. maritimus
Polar bear fur is hollow and looks white, but the skin underneath is black.
Polar bears are strong swimmers and may cross miles of open ocean.
A polar bear's sense of smell can detect a seal nearly a mile away.
Polar bears mainly hunt on sea ice, not on open land.
Cubs are born tiny in a snow den during the Arctic winter.
Polar bears are the largest bears in the world.
Select a question to reveal the answer.
A polar bear is a huge Arctic bear that hunts seals on sea ice. It is the largest land carnivore alive today.
Polar bears live in the Arctic around Canada, Alaska, Greenland, Norway, and Russia. They travel on sea ice and coastal tundra.
Polar bears are carnivores that mainly eat seals. They catch seals at breathing holes or break into snow dens.
Polar bears are listed as Vulnerable because climate change is melting the sea ice they need to hunt.
Yes. Polar bears are excellent swimmers and use their large front paws like paddles in the ocean.
Sea ice lets polar bears reach seal hunting areas far from shore. Less ice means less time and space to find food.
A baby polar bear is called a cub. Cubs stay with their mother for about two and a half years.
Polar bears typically live 20 to 25 years in the wild. Their survival depends heavily on access to sea ice and enough seals to build fat reserves.
The guard hairs are pigment-free and appear white because they scatter visible light. Beneath the fur, a polar bear's skin is black.
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