Thursday, April 19, 2012

Polar Bear - Alterations In Sea Ice Threatens The Species



Polar Bear - Alterations In Sea Ice Threatens The Species


Polar Bear adaptation to the cold and unforgiving Northern climate is one of nature's marvels. The dynamic sea ice, where polar bear live, is one of the harshest and most unforgiving climates on the globe.

It's only in modern evolutionary cycle that bears accommodated to arctic sea life. It started about the time of the Ice Age, in the northern seas, when the seals needed to breathe and reproduce at the water's surface. From this, the seals placed a rich year-round food source within reach of a population of brown bears, who then set out to live on the ice, changing into something similar to the polar bear of today, around 100,000 years ago.

Weighing about 330 to 1,760 pounds, the length of the polar bear's body is around 6.6 to 10 feet. The male body is usually heavier than the female. The polar bear, similar to the brown bear, is big and heavyset. It has an long neck and small head. Its fur, typically white, sometimes appears yellow, due to oxidation.

A polar bear has black skin, which aids it's adjustment to the Arctic temperature, absorbing and holding heat from the sunlight. It is decidedly well attired for the weather with a layer of fat more than 4 inches thick, providing good insulation. The thick fur on its feet (its foot is about 9 inches wide and 12 inches long) offers warmth and traction. As each foot is so huge, it acts as a handy snowshoe.

It adjusts well to swimming with its broad feet that serve as paddles and when swimming underwater it lays the little ears flat for protection, and its nostrils close under water. It paddles at about 6 and one-half miles per hour --forepaws only, hind feet trailing--and can stay submerged for about 2 minutes. The hairs of its waterproof coat are hollow which is a good insulator and increases the bear's buoyancy while swimming.

A polar bear has an excellent sense of smell, sensing prey at a distance of about 20 miles. While little is known about its sense of touch (its eyesight and hearing is acute), a polar bear is able to manipulate various objects with great dexterity.

With canine teeth larger and malariform teeth sharper than those of other bears, the polar bear is the most carnivorous North American bear.

A polar bear inhabits Arctic islands, sea ice, and water and continental coastlines. It favors the sea ice habitat, with water channels or cracks through the ice, next to continental coastlines or islands. A lot of polar bears spend part of the year on land, although in warmer climates a bear might become isolated. Most pregnant females spend the autumn and winter on land in maternity dens.

A polar bear moves throughout the year within single home ranges, which tend to be larger than for other mammal species because of the changes in sea ice from year to year and even season to season. Small home ranges (19,000 to 23,000 miles) can be observed near Canadian Arctic Islands, while bigger home ranges can be found in the Bering or Chukchi Sea regions. The polar bear stays in the same area during the same time of year. A polar bear can travel 19 miles or more per day for several days, although some are capable of much more than that. One can only hope that polar bear adaptation will continue, as their habitat area becomes increasingly smaller and the pressures of civilization continue to encroach on the the natural homes where the polar bear dwell.




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