A bear native to the Arctic ice pack and surrounding seas (Thalarctos maritimus); white with long neck and small head; swims well; eats mainly seals, also small mammals, birds, reindeer (can outrun reindeer over short distances), fish, vegetation.
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?Polar Bear Conservation status: Vulnerable |
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Ursus maritimus Phipps, 1774 |
The polar bear (Ursus maritimus), also known as the white bear, northern bear, or sea bear, is a large bear native to the Arctic. The polar bear hunts well on land and on the sea ice, as well as in the water.
Natural range
The polar bear is a circumpolar species found in and around the Arctic Ocean whose southern range limits are determined by pack ice (their southernmost point is James Bay in Canada).
Size and weight
It shares the title of the largest extant species of land carnivore with the larger subspecies of its close relative the Brown Bear. The largest polar bear ever on record was a bear shot in Kotzebue Sound, Alaska in 1960.
A 2004 National Geographic study showed that polar bears that year weighed, on average, fifteen per cent less than they had in the 1970s.
Subspecies
It is generally believed that there are no living polar bear subspecies. In fact, because polar bears bred with brown bears have produced fertile hybrids, it can be argued that polar bears are a subspecies of Brown Bear. The IUCN/SSC Polar Bear Specialist Group ("PBSG"), the preeminent international scientific body for research and management relating to polar bears, currently recognizes twenty populations, or stocks, worldwide. Other scientists recognize six distinct populations, but no (living) subspecies:
Chukchi Sea population on Wrangel Island and western Alaska Northern and northwestern Alaska and northwestern Canada (the Beaufort Sea population) Canadian Arctic archipelago Greenland Spitzbergen-Franz Josef Land Central SiberiaOther sources list these subspecies:
Ursus maritimus maritimus Ursus maritimus marinusFur and skin
A polar bear's nose and skin are black and the fur is translucent despite its apparent white hue.
Unlike other arctic mammals, polar bears never shed their coat for a darker shade in the summer.
In July 2005, several polar bears in the Brookfield Zoo turned green as a result of algae growing in their hollow guard hair tubes. A similar algae grew in the hair of three polar bears at San Diego Zoo in the summer of 1980.
Hunting, diet and feeding
The polar bear is the most carnivorous member of the bear family, and the one that is most likely to prey on humans as food. It feeds mainly on seals, especially ringed seals that poke holes in the ice to breathe, but will eat anything it can kill: birds, rodents, shellfish, crabs, beluga whales, walruses, occasionally musk oxen, and very occasionally other polar bears. Orcas, humans, and larger bears of their own species are the only predators of polar bears, although walruses may occasionally kill a polar bear during a struggle to defend themselves.
Polar bears are excellent swimmers and can often be seen in open waters miles from land. Recently, polar bears in the arctic have undertaken longer than usual swims to find prey, resulting in four recorded drownings in the unusually large ice pack regression of 2005. Still, caribou and musk oxen can easily outrun a polar bear, and polar bears overheat quickly: thus the polar bear subsists almost entirely on seals and on walrus calves or adult carcasses.
As a carnivore which feeds largely upon fish-eating carnivores, the polar bear ingests large amounts of Vitamin A, which is stored in its liver;
Polar bears are enormous, aggressive, curious, and extremely dangerous to humans. It is best to remember that wild polar bears, unlike most other bears, are often barely habituated to people and will quickly size up any animal they encounter as potential prey.
Regrettably, like other bear species, they have developed a liking for garbage;
Breeding
Polar bears mate in the spring; Adult polar bears are known to live over 30 years. Polar bears do not hibernate, though lactating females will not emerge from their cave while the cubs are very young;
Evolutionary relationships
The raccoon and bear families are believed to have diverged about 30 million years ago and around 13 million years ago the spectacled bear split from the other bears. According to both fossil and DNA evidence, the polar bear diverged from the brown bear around 200 thousand years ago, and crosses between the two species have produced fertile grizzly-polar bear hybrids.
In a widely-cited paper published in 1996 by Sheilds and Talbot of the University of Alaska Fairbanks, a comparison of the DNA of various brown bear populations showed that the brown bears of Alaska's ABC islands actually shared a more recent common ancestor with polar bears than with any other brown bear population in the world.
Entertainment and commerce
Polar bears have been made both controversial and famous for their distinctive white fur and their habitat.
The hit TV series Lost has featured polar bears on a mysterious (and, strangely, tropical) island.
Gallery
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Three Polar Bears investigate the submarine USS Honolulu 280 miles from the North Pole. |
Two Polar Bears sparring near Churchill, Manitoba, Canada. |
Polar Bear tracks at Svalbard |
Tourists watching Polar Bears from a "tundra buggy" near Churchill, Manitoba |
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Polar Bear cubs |
Polar Bear at Cape Churchill (Wapusk-Nationalpark, Manitoba, Canada) |
Two Polar Bears at Cape Churchill (Wapusk-Nationalpark, Manitoba, Canada) |
A Polar Bear floating at the Henry Doorly Zoo |
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