Tuesday, April 7, 2009
Polar Bear Quick Facts
By Anna Spencer
He is the only Ursus maritimus, meaning marine bear. Along with his bear cousins, he is the largest of the land mammals and is at the top of the food chain. Because he lives on the sea ice of the Arctic Polar Basin and regions around the northern Arctic, including the northern coasts of Russia, Greenland and arctic islands, he will seldom cross paths with humans. When he does, he will generally ignore them, and there are only a few recorded instances of aggression.
Polar bears have an elongated neck that helps them to be better swimmers. Also, their front paws are broader and partially webbed. They have long hairs between their foot pads to protect them from the cold and help them grip the ice. Their five sharp, curved claws on each foot also help them grip the ice and clutch their prey.
Males will typically weigh around 1,000 pounds (454 kg) and stand about 10 to 12 feet high. Females tend to be smaller and usually weigh about 550 pounds (250 kg) and grow to about 6 feet. Baby cubs will weigh 2 pounds or less at birth and are blind for about 40 days.
Polar bears have two types of fur. One is a thick, woolly fur close to their skin. The other is actually a clear, hollow tube that can channel the sun's energy directly to their skin to help keep them warm. This gives them their white appearance, but they may have a yellow cast during summer. Another heat source is the layer of fat under their skin which can be four inches thick.
Polar bears start breeding at the age of five, during the summer months of May to June. Males will fight over the females but both will mate with others. Only the females have a den, which they will dig on a slope.
The female will hibernate from November until about March during which time she will give birth to one to four cubs, but more often twins. As with other bears, mother bears form a close bond with their cubs. Polar bear milk is extremely rich in fat compared to humans (40% versus 4%). The mother will nurse newborns every two hours and then wean them after about six months, although they will remain a family unit for about two years.
These bears are nomadic, and travel an average of 5,500 miles a year! Since their territories are so scattered, many of their ranges will overlap. Male bears are solitary except for the mating season and an occasional extra-large feeding opportunity such as a beached whale.
Polar bears are primarily Carnivora, or meat eaters. Their first choice is the ringed seal, but have been known to eat bearded seals, walruses, white whales and some sea birds. Less often, they will eat berries, mussels and some types of grasses.
They are called "still hunters" for the way that they will surprise their prey by waiting until the seal comes up for air at an ice hole or lunging at them while they are on an ice floe. Nighttime is their usual feeding time as that is when the seals are most active.
Polar bears' large stomachs can hold up to 150 pounds of meat at a time, and they may go a week or more between feedings. That also means that they will often nap during the day for up to eight hours - it's time to digest that food! Their keen sense of smell will help them find food from miles away (up to ten miles!) and find a seal den buried under ice and snow.
Although polar bears are not on the endangered list, their lives are still threatened by mankind and global warming.
Off-shore drilling will often cause their food sources to retain chemicals in their systems, thereby slowly poisoning them after eating the prey. Six out of ten cubs born will die in their first year due to accidents, attacks, or starvation.
A recent study also found that some polar bears are drowning due to global warming. They are forced to swim very long distances since the arctic ice shelf is melting. Polar bears can easily swim 10-15 miles, but since the ice floes have become smaller, they now have to swim up to 60 miles in search for food, especially during the summer months. This can lead to exhaustion or hypothermia. The rough sea can cause problems, too.
In 1973, the five "polar bear nations"- Norway, Canada, Russia, Greenland, and the United States - signed a conservation agreement which protects the bears from being hunted from aircraft and powerboats for their skins and as hunting trophies. It permits hunting by local people with traditional methods (such as Inuit peoples). Their numbers are estimated to be 21,000 to 25,000 in the wild.
Under all the fur, polar bear skin is actually black! They are such good swimmers that they can swim sixty miles without stopping, and have been found 100 miles from land.
They once captured a male that was 18 feet tall, and the largest recorded weight was a whopping 2,200 pounds!
Churchill, Manitoba in Canada is known as the Polar Bear Capital of the World because polar bears gather there every year between October and December to wait for the ice to re-freeze so they can start hunting seals again. It is a big tourist attraction with thousands of people coming to take pictures - the bears will even come into town looking for food.
Species: U. maritimus
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