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Polar Bear's Status
About the Polar Bear
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More Facts
   Adaptions to Cold
   Communication
   Polar Bear Prey
   Home Range
Bears in Motion
Inuit & Polar Bears
Bear Attacks
Polar Bears in Zoos
Myths & Misconceptions
Hunting Seals
Hibernation Facts
Bathing Habits
Sleepy Bears
Name That Bear!
Walking and Running
Feasting Bears
Polar Bear Evolution


US Fish & Wildlife Report on Polar Bears.

Prepared in 1995, this report presents a thorough description of what is known about polar bear populations.

 

Adaptation to Cold

Polar bears are well-adapted to severe cold. Winter temperatures in the far north often plunge to -40° F or -50° F and can stay that way for days or even weeks.

In January and February, the average temperature in the high Arctic is -29° F.

The Arctic stays black and fiercely cold for months on end. In the High Arctic, the sun sets in October and does not rise again until late February.

The word "Arctic" comes from the ancient Greek Arktikos, or "country of the great bear." Though the Greeks had no knowledge of the polar bear, they named the region after the constellation Ursus Major, the Great Bear, found in the Northern Sky.

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 remain the same even at -34°F.

A polar bear's body temperature is 98.6°, which is average for mammals.

On bitterly cold days with fierce winds, polar bears dig out a shelter in a snow bank and curl up in a tight ball to wait out the storm.

When curled up in a ball, polar bears sometimes cover their muzzles -- which radiate heat -- with one of their thickly furred paws.

Polar bears know how to pack on the fat: A single bear can consume 100 pounds of blubber at one sitting.

The polar bear's compact ears and small tail also help prevent heat loss.

Polar bears have two layers of fur for further protection from the cold.

Polar bears have more problems with overheating than they do with cold. Even in very cold weather, they quickly overheat when they try to run.

Polar bears generally walk at a leisurely pace to keep from overheating. When a Norwegian scientist, Nils Oritsland, studied a polar bear on a treadmill, he found that his subject would move off for short periods of time at higher speeds and would sometimes lie down and refuse to walk at all!

Sources: Arctic Animals by Fred Bruemmer (McClelland and Stewart Limited, Toronto, 1986); Polar Bears by Ian Stirling (University of Michigan Press, Ann Arbor, 1988); Biochemistry by Reginald H. Garrett and Charles M. Grisham (Saunders College Publishing).


Communication

Polar bears communicate with each other through a combination of body language and vocalizations.

A deep growl serves as a warning to other bears. Growls are frequently employed to defend a food source.

To beg food from another bear, a polar bear will approach slowly, circle around the carcass, and then meekly offer a nose-to-nose greeting.

Bears who observe proper manners are frequently allowed to share a kill.

When a polar bear wants to play, he communicates this to another bear by wagging his head from side to side.

An adult bear may also initiate a play session by standing on his hind legs, with chin lowered to his chest and front paws hanging by his side.

In adult bears such play sessions involve ritualized fighting or mock battles.

Among polar bears, hissing and snorting signify aggression, as does a lowered head. An attacking polar bear will charge forward with head down and ears laid back.

Submissive polar bears always move downwind of dominant bears.

When a male approaches a female with cubs, she defends her young by rushing at him with a lowered head.

Angry polar bears communicate their displeasure with loud roars and growls.

A "chuffing" sound is a response to stress.

Mother bears scold their cubs with a low growl or a soft cuff.

Sources: Lords of the Arctic by Richard C. Davids (Macmillan Publishing, 1982); Polar Bear by Downs Matthews (Chronicle Books, 1993); Polar Bears by Nikita Ovsyanikov (Voyageur Press, 1996); Polar Dance by Thomas D. Mangelsen and Fred Bruemmer (Images of Nature, 1997).


Polar Bear Prey

The polar bear's main prey is the ringed seal, the most numerous seal in the Arctic.

Ringed seals live in the circumpolar region north to the Pole. Though most commonly found on land-fast or solid ice, they are sometimes seen on ice floes.

Adult ringed seals reach an average length of 4.1 feet and weigh about 150 pounds. They are padded with a thick layer of blubber.

Adult seals are dark on top and spotted with cream-colored rings that are dark in the center. Underneath, their coats are white to creamy yellow.

Ringed seal pups are born in snow dens on land-fast ice in mid-March or Mid-April. They remain with their mother to nurse for about two months, but learn to swim and hunt as the ice breaks up in early summer.

In winter, polar bears capture ringed seals by lying in wait by one of their breathing holes. When the seal rises for air, the polar bear yanks it from the water.

Though Inuit hunters report that the polar bear covers its black nose when waiting for a seal, scientists have never observed this behavior.

In early summer, polar bears stalk ringed seals when they're basking on the ice by taking advantage of the animal's sleep-wake rhythms. The bear crawls slowly forward when the seal sleeps and freezes in place when the animal raises its head.

At about 20 feet from its prey, the polar bear pounces, killing the seal before it can escape back into the sea.

When hunting is good, polar bears eat only the seal's blubber and skin. Younger, less experienced bears devour the remains, as do arctic foxes.

Interestingly, scientists have found that when polar bears dine exclusively on seal fat, their cholesterol levels drop lower than those of fasting bears because of the protective quality of the omega-3 fatty acids found in the seals.

Traditionally, the ringed seal was important not just to the polar bear, but to the coastal Inuit. In addition to eating the seal's meat and blubber, the Inuit made the intestines into igloo windows or containers They fashioned tents, mats and clothing from the skin, made tools from the bones, and burned the fat for warmth and light.

Sources: Arctic Animals by Jonquil Graves and Ed Hall (Northwest Territories Renewable Resources, Yellowknife, N.W.T., 1985); Arctic Animals by Fred Bruemmer, McClelland and Stewart Limited, Toronto, 1986); The Polar Marine Food Chain, Fat Metabolism and the Ozone Hole by G. Edgar Folk, Jr. (Proc. Conference on Biometeorology, 1994).


Home Range

Polar bears were once thought to be aimless wanderers, continually on the move across the sea ice. Scientists now believe that polar bears, like other members of the bear family, have distinct territories, or home ranges.

A polar bear's home range can be enormous, far greater than that of any other species of bear. A single polar bear may rove across an area twice as big as the country of Iceland.

One Alaskan polar bear was found to have a home range 45 times the size of Tennessee's Great Smoky Mountains National Park, which supports some 400 black bears.

Scientists note that the size of a bear's range is determined by the amount of available food. Polar bears living in areas with an abundance of ice and seals have smaller home ranges.

A polar bear's home range often overlaps those of other polar bears. This is particularly true in food-rich areas.

An area where many home ranges overlap is called a subpopulation. Scientists have identified 12 subpopulations of polar bears in the circumpolar region. Polar bears learn to respond to seasonal changes in the distribution of seals. Cubs develop a knowledge of these patterns during the two or three years they spend with their mother.

Young polar bears may travel more than 1,000 kilometers (600 miles) to set up a home range apart from their mother's.

While scientists believe that most polar bears limit their travels to a home range of a few hundred miles, one satellite-tracked female surprised researchers by setting off on a trek of some 3,000 miles. The power-walking bear began her journey at Alaska's Prudhoe Bay. From there she traveled across the top of the world to Greenland, where she spent the winter before moving on to Canada's Ellesmere Island and back to Greenland again.

Sources: Bears, Bears, Bears by Wayne Lynch (Firefly Books, Willowdale, Ontario, 1995); Polar Bears by Ian Stirling (University of Michigan Press, 1988); Anchorage Daily News (February 1996).



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