Largest Carnivore on Land - Polar Bear
Polar Bears are Cool
The average adult male weighs between 850-900 lbs/380-400 kgs, but one killed in 1960 weighed 2,210 lbs/995 kgs! He was 12 feet long. That's the size of a family car! Polar bears live only in northern climates, in the Arctic circle and can be found in Canada, Alaska, Norway and northern Russia.
Polar bears spend a lot of time moving great distances in search of their favorite food - seals. The range of these bears can vary from 20,000 to as many as 135,000 square miles. They hunt for seals through the winter ice that forms over the ocean, where the seals spend most of their time (to get away from the bears). When the ice over the sea melts in summer the polar bears can't hunt for the seals as easily, so they fast all summer long. In order to survive an entire summer without food they eat a LOT of seals in winter building up fat stores until half of their body mass is pure fat. That enormously thick layer of fat also helps to keep
During the summer months when the sea ice melts they will roam as far south as Hudson Bay, where they hang out and "chill" until the sea ice forms again in the fall. The warmest areas in summer are inland regions of Siberia, Alaska, and Canada where temperatures can reach as high as 90°F/32°C, which is pretty comfortable for folks without fur coats (you and me).
The coat of fur on an average polar bear is about 1-2 in./2.5 to 5 cm thick. A dense, wooly, insulating layer of underhair is covered by a relatively thin layer of stiff, shiny, guard hairs. Believe it or not, their fur isn't actually white. If you got up real close to a polar bear and plucked one of his hairs you would see that the polar bear's coat is made of clear, colorless hairs (and you would probably find out how powerful the bear is). The hairs scatter light, making it appear white (or sometimes yellow, depending upon the angle of the sun). If you were to pull out all of the polar bear's hairs (which would really be stupid) you would see black skin underneath all that white fur. In the photo (below, at left) where the bear's fur is thinnest on the snout you can see the black skin beneath.
The bears' black skin absorbs the heat from the sun and the six-inch layer of fat under their skin insulates them from the extreme cold of the Arctic circle. You and I would be miserably cold living outside all the time above the Arctic circle, but polar bears are quite comfortable. In fact, polar bears are so well insulated against the brutal cold of their environment that they have a tendency to get overheated. How do they cool off? Usually by going for a swim.
Polar bears are excellent swimmers. Researchers have tracked polar bears swimming for several hours straight, as much as 100 kilometers in a single stretch. They can only hold their breath for about two minutes, but they can close their nostrils (without having to pinch their noses,
Another physical adaptation of the polar bear to its icy habitat is its enormous paws. Polar bears' paws are massive compared to their body size if you compare them with other bears. Their large, rounded paws give the bears increased surface area for walking over snow and ice - kind of like built-in snowshoes.
A male polar bear can weigh two to three times as much as a female bear. Male polar bears are called boars and female bears are called sows, while their babies are called cubs. Males and females only get together during mating season. When female polar bears are pregnant they go into a modified hibernation state - it's not a deep hibernation because their body temperatures remain high. They have to in order to facilitate the growth and nourishment of their developing cubs.
When pregnant a female polar bear will dig a den in a southward-facing snowbank and crawl inside to rest for up to eight months or more. She will give birth to one or two, two-pound cubs while she is hibernating. Polar bear cubs are too tiny at first to tolerate the extreme cold of their native habitat. She and her babies will stay holed up inside the den alternating between sleeping and nursing. Mama bear will not eat while caring for her tiny babies. She will devote herself exclusively to nursing her cubs, her body providing nourishment for them by drawing from her fat stores. It takes a tremendous amount of energy for a female polar bear to bear, give birth to, and nourish cubs for the better part of a year. In the spring she will emerge from her den and begin to hunt for seals to provide meat for her growing cubs. Polar bear cubs will stay with their mother for as long as 30 months before she, or a prospective mate, will drive them away to fend for themselves.
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