Polar Bear
Physical Description
Polar bear (Ursus maritimus) standing on the summer tundra. Polar bears are threatened by climate change. Churchill, Canada
© Steve Morello/WWF-US
Polar bears are the top predator in the arctic marine ecosystem and the largest terrestrial carnivore. They evolved from brown bears during the Pleistocene, the time period that spanned from 1.8 million to 11,000 years ago.
The polar bear's coat, covering it completely except for the nose and foot pads, is superbly adapted to Arctic environments. Along with a thick layer of body fat, the water-repellent coat insulates the bear from cold air and water. It also serves as camouflage; in fact, polar bears can sometimes pass as snow drifts. Surprisingly, the fur has no white pigment.
Polar bears are excellent swimmers and can sustain a pace of 10 km/h by using their front paws like oars while their hind legs are held flat like a rudder. Adult males typically measure 6.5 - 9.8 feet from the tip of the nose to the tip of the tail and weigh 780 - 1,500 lbs. Females are usually half the size of males, unless pregnant. The bear's body and neck are elongated, and the head is narrow and long with small, rounded ears.
They spend much of their time at or near the edge of the pack ice. This is where they are most likely to find food. As the southern edge of the arctic ice cap melts in summer, some bears will follow the retreating ice north to stay close to seals and other prey. Other bears spend their summers on land, living off body fat stored from successful hunting in the spring and winter. When the ice returns in the fall, the bears leave land to resume life on the sea ice.
