The polar bear rivals the Alaska brown bear as the world’s largest land predator. A large male polar bear may weigh up to 1,500 pounds and grow to nearly 10 feet tall, standing on its hide legs; however, a record male shot in 1960 in Alaska weighed 2,210 pounds and stood 12 feet tall. The petite females stand only up to about 8 feet tall and tip the scales at a svelte 550 pounds or less.
Polar bears are closely related to brown bears and probably evolved from a brown population that become isolated from others of their kind perhaps 150,000 years ago during the most recent ice age—making polar bears a newer, or more “modern,” species than the modern human, which dates back at least 200,000 years.
Brown and polar bears can interbreed and produce fertile young, which by some definitions suggests they are the same species. However, they are adapted to different habitats and behaviors and, under the climate conditions that have prevailed since the last ice age, cannot survive very long in each other’s habitat, a factor that keeps them isolated and continuing to evolve away from one another.
You can sometimes tell male polar bears from female by the hair on the males’ front legs. Once mature, males tend to have much longer hair on their forelimbs.
Polar bear hair is transparent; the way it reflects light makes it look white. It can turn yellowish with age.
Polar bears are so adapted to cold that they can’t take temperatures above 50 degrees.
Wild polar bears probablylive more than 25 yearsonly rarely, but in captivity they have lasted up to 43 years.
Despite the harsh winter conditions that batter the polar bear’s Arctic home, only females about to give birth hibernate. Males remain active year round. However, when food is scarce during warm seasons, polar bears can go a few months without eating.
Most land animals are too fast for the bear to catch. Polar bears prey mostly on marine mammals, including seals and the occasional beluga whale. Lying by breathing holes in the ice, the bears snatch prey from the water when the animals come up for air.
Although polar bears eat everything from crabs to kelp to muskoxen, they are adapted to feeding on calorie-rich blubber. When dining on seals, adults favor the fat and the skin exclusively, while younger bears may sup on seal meat.
Found in Arctic reaches in both hemispheres, the polar bear maintains a foothold on more of its native range than any other large meat-eating animal, but only because its habitat is so inhospitable to humans that the bear has never had to contend with much human encroachment.
The polar bear has been protected for many years. Russia outlawed hunting in 1956, and Greenland began regulating it in 1994. The United States began protecting the species under the Marine Mammal Protection Act in 1972 and under the Endangered Species Act in 2008, when the bear was listed as threatened. Tightly regulated hunting is allowed in Canada, where about 500 bears are killed yearly.
About 25,000 polar bears survive worldwide, but the population apparently is declining from a variety of causes, including pollution and poaching. The most severe threat in the long run is likely to be global warming, which is destroying the sea ice that the bear needs to continue its nomadic existence in search of Arctic seals for food.