Home range. Scientists believe polar bears have distinct territories, or home ranges. [PB7 Maps & Trackers.doc: Population and Distribution}
A polar bear’s home range can be enormous, far greater than that of any other species of bear. One Alaskan polar bear’s home range was found to be 45 times the size of Great Smoky Mountains National Park, which supports some 400 black bears.
The size of a bear's range depends on how much food is available there. Polar bears in food-rich areas have smaller home ranges, which often overlap those of other bears.
- Subpopulations occur in areas where many home ranges overlap. Scientists have identified 18 subpopulations of polar bears in the circumpolar region.
Polar bears respond to seasonal changes in the distribution of seals. Cubs learn about these patterns during the time they spend with their mother. Young polar bears may travel more than 600 miles (1,000 Km) to set up a home range apart from their mother's.
- Scientists believe that most bears limit travel to home ranges of a few hundred miles. But they know one satellite-tracked female trekked 3,000 miles (4,800 Km)—from Alaska's Prudhoe Bay to Greenland to Canada's Ellesmere Island and back to Greenland.
Cold Climate. Polar bears are well-adapted to the Arctic's night skies and fiercely cold weather.
In the High Arctic, the sun sets in October and doesn’t rise again until late February. Winter temperatures often plunge to -40º or
-50º F and stay that way for days or weeks. The average January and February temperature is -29º F.
Insulation. A thick layer of blubber (up to 4.5 inches thick) provides polar bears with such excellent insulation that their body temperature and metabolic rate won’t change even when temperatures reach -34º F. Two layers of fur, compact ears, and small tail also help prevent heat loss. A polar bear's body temperature is 98.6º F—average for mammals.
On bitterly cold days with fierce winds, polar bears dig shelters in snow banks and curl up in a tight ball. Sometimes they cover their muzzles, which radiate heat, with their thickly furred paws.
Polar bears have more problems with overheating than they do with cold. That’s why they walk at a leisurely pace. They quickly overheat when they run.
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