Earth Stories: Polar Bears

The Polar Bear is on the World Conservation Union (IUCN) Red List of Threatened Species. Estimates range from a 30% decline in population in the next 45 years to extinction in 50 years. It is believed that the polar ice cap will disappear almost entirely during the summer in the next 100 years. There have been significant reductions in the extent and thickness of the arctic sea ice. There are 20,000 to 25,000 bears, with 60% of polar bears living n Canada. Polar Bears are found only in the Northern Hemisphere, in the Arctic. Polar Bears hunt, feed, mate, and den on the sea ice.

Male Polar Bears grow 8-10 feet tall and weigh 550 to 1700 lbs; females are 6-8 feet tall and weigh 200-700 lbs. They can withstand the -500F winter with a 4.5 inch thick layer of blubber. Polar Bears live to an average of 15-18 years in the wild. They have a nose powerful enough to detect prey miles away. Their preferred prey is the ringed seal, but other seals are also hunted. Polar Bears wait at the breathing holes in the ice for the seals to emerge, and attack then. They help to prevent an overpopulation of seals. Polar Bears will also eat walrus and beluga whales. Polar Bears, if prey is sufficient, provide food for other species, such as the arctic fox, as the Bears only consume the seal fat, and leave the carcass for scavengers.

Polar Bears can swim more than 60 miles without resting using their webbed forepaws which measure up to 12 inches in diameter. Polar Bears stay clean by washing off after feasting either in the surf, or by 'washing' their face in pawfuls of snow. Clean unmated fur better protects them against the cold. They dry off after a swim by shaking like a dog, and then rubbing their bellies on the ice.

Polar Bears have the slowest reproductive rates of any mammal with females producing only five litters in a lifetime. Polar Bears do not give birth until their 5-8th year of life. Cubs are born weighing 1 pound, and stay with their mothers until they are about 3 years old. Six out of ten cubs will die in their first year of life-victims of starvation, predation, or accidents. Longer ice-free periods resulting from earlier break-up of sea ice in the spring and later formation in the fall is already impacting Polar Bears. The time Polar Bears have on the ice to hunt and feed is cut short when the ice melts early. Studies in Hudson Bay, Canada, already show that bears will come ashore 22 lbs lighter and in poorer condition. As the time for ice-free seas increase the Polar Bears hunting season shortens, which decreases their ability to have fat reserves on hand during the winter when they naturally fast. Their ability to survive longer ice-free seasons is diminished. Female bears are in poorer condition gong into the denning period. Polar Bears are at the apex of the food chain in the Arctic, and therefore will consume more pollutants, especially those which are deposited in fat. Polar Bears consume the fat of the ringed seals. These factors contribute to the low reproductive potential for Polar Bears.