The polar bear (Ursus maritimus) is a carnivorous bear whose native range lies largely within the Arctic Circle, encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. It is a large bear, approximately the same size as the omnivorous Kodiak bear (Ursus arctos middendorffi). A boar (adult male) weighs around 350–700 kg (770–1,540 lb),while a sow (adult female) is about half that size.
Although it is the sister species of the brown bear, it has evolved to occupy a narrower ecological niche, with many body characteristics adapted for cold temperatures, for moving across snow, ice, and open water, and for hunting the seals which make up most of its diet.Although most polar bears are born on land, they spend most of their time at sea. Their scientific name means “maritime bear”, and derives from this fact. Polar bears hunt their preferred food of seals from the edge of sea ice, often living off fat reserves when no sea ice is present.
Polar bears roam the Arctic ice sheets and swim in that region’s coastal waters. They are very strong swimmers, and their large front paws, which they use to paddle, are slightly webbed. Some polar bears have been seen swimming hundreds of miles from land—though they probably cover most of that distance by floating on sheets of ice.
Polar bears live in one of the planet’s coldest environments and depend on a thick coat of insulated fur, which covers a warming layer of fat. Fur even grows on the bottom of their paws, which protects against cold surfaces and provides a good grip on ice. The bear’s stark white coat provides camouflage in surrounding snow and ice. But under their fur, polar bears have black skin—the better to soak in the sun’s warming rays.
These powerful predators typically prey on seals. In search of this quarry they frequent areas of shifting, cracking ice where seals may surface to breathe air. They also stalk ice edges and breathing holes. If the opportunity presents itself, polar bears will also consume carcasses, such as those of dead whales. These Arctic giants are the masters of their environment and have no natural enemies.
Females den by digging into deep snow drifts, which provide protection and insulation from the Arctic elements. They give birth in winter, usually to twins. Young cubs live with their mothers for some 28 months to learn the survival skills of the far north. Females aggressively protect their young, but receive no help from their solitary male mates. In fact, male polar bears may even kill young of their species.
Polar bears are attractive and appealing, but they are powerful predators that do not typically fear humans, which can make them dangerous. Near human settlements, they often acquire a taste for garbage, bringing bears and humans into perilous proximity.
Polar Bear Status Report
Biologists estimate there are 20,000 to 25,000 polar bears. About 60% of those live in Canada. Polar bears are also found in the U.S. (Alaska), Russia, Greenland, and Norway (Svalbard).
In May 2008, the U.S listed the polar bear as a threatened species under the Endangered Species Act, citing sea ice losses in the Arctic from global warming as the single biggest threat to polar bears. Polar bears depend on sea ice for hunting, breeding, and in some cases, denning. In recent years, summer sea ice losses in the Arctic have been accelerating.
The IUCN Polar Bear Specialist Group also lists sea ice losses from a warming Arctic as the biggest threat to polar bear survival. At their 2013 meeting, scientists reported that of the 19 subpopulations of polar bears:
4 are declining
5 are stable
1 is increasing
9 have insufficient data
Polar bear distribution map world wide.
“Global warming is no longer a philosophical threat, no longer a future threat, no longer a threat at all. It’s our reality” ~ Bill McKibben