The polar bear is arguably the most impressive and iconic mammals of the arctic tundra. Unfortunately, due to a combination of hunting, loss of habitat, increased pressure from an expanding local human population, global warming and the associated melting of the ice caps and accidental poisoning, polar bear numbers are now in decline.
This problem is exacerbated as polar bears have low reproduction rates, but before we can address, and hopefully arrest the decline in polar bear numbers we need to know as much as we can about their behaviour and habitats.
What do polar bears eat?
The polar bear is the most carnivorous member of the bear family, and most of its diet consists of ringed and bearded seals. The Arctic is home to millions of seals, which become prey when they surface in holes in the ice in order to breathe, or when they haul out on the ice to rest Polar bears hunt primarily at the interface between ice, water, and air; they only rarely catch seals on land or in open water.
The polar bear kills the seal by biting its head to crush its skull. The polar bear also hunts by stalking seals resting on the ice. Upon spotting a seal, it walks to within 100 yd (91 m), and then crouches. If the seal does not notice, the bear creeps to within 30 to 40 feet (9.1 to 12 m) of the seal and then suddenly rushes forth to attack. A third hunting method is to raid the birth lairs that female seals create in the snow.
A widespread legend tells that polar bears cover their black noses with their paws when hunting. This behaviour, if it happens, is rare — although the story exists in native oral history and in accounts by early Arctic explorers, there is no record of an eyewitness account of the behaviour in recent decades.
For sub-adult bears which are independent of their mother but have not yet gained enough experience and body size to successfully hunt seals, scavenging the carcasses from other bears' kills is an important source of nutrition. Sub-adults may also be forced to accept a half-eaten carcass if they kill a seal but cannot defend it from larger polar bears. After feeding, polar bears wash themselves with water or snow.
The polar bear is an enormously powerful predator. It can kill a full grown adult walrus, although this is rarely attempted as a walrus can be more than twice the bear's weight, and has up to three feet long ivory tusks that can be used as formidable weapons.
Most attacks on walruses occur when the bear charges a group and either targets the slower moving walruses, usually either young or infirm ones, or a walrus that's injured in the rush of walruses trying to escape. They will also attack adult walruses when their diving holes have frozen over or intercept them before they can get back to the diving hole in the ice. Since attacks on walruses tend to be an extremely protracted and exhausting venture, bears have been known to abandon the hunt after making the initial injury.
Most terrestrial animals in the Arctic can outrun the polar bear on land as polar bears overheat quickly, and most marine animals the bear encounters can out swim it.
In some areas, the polar bear's diet is supplemented by walrus calves and by the carcasses of dead adult walruses or whales, whose blubber is readily devoured even when rotten.
With the exception of pregnant females, polar bears are active year-round, although they have a vestigial hibernation induction trigger in their blood. Unlike brown and black bears, polar bears are capable of fasting for up to several months during late summer and early fall, when they cannot hunt for seals because the sea is unfrozen.
When sea ice is unavailable during summer and early autumn, some populations live off fat reserves for months at a time. Polar bears have also been observed to eat a wide variety of other wild foods, including musk ox, reindeer, birds, eggs, rodents, shellfish, crabs, and other polar bears. They may also eat plants, including berries, roots, and kelp, however none of these are a significant part of their diet. The polar bear's biology is specialised to require large amounts of fat from marine mammals, and it cannot derive sufficient caloric intake from terrestrial food.
This means that Polar bears may attempt to consume almost anything they can find, including hazardous substances such as styrofoam plastic, car batteries, ethylene glycol, hydraulic fluid, and motor oil.
To reduce the incidence of poisoning, the municipal dump in Churchill, Manitoba was closed in 2006 to protect bears, and waste is now recycled or transported to Thompson, Manitoba. The polar bear - Ursus maritimus, is a bear native mainly found within the Arctic Circle encompassing the Arctic Ocean, and adjacent land masses as far south as Newfoundland Island.
Where do polar bears live?
Polar bears spend most of their time along the southern edge of the Arctic pack ice – a combination of pack ice, open water and coastal land.
Thankfully, due to the absence of human development in its remote habitat, it is able to retain more of its original range than any other carnivore living today.
The range includes the territory of five nations: Denmark (Greenland), Norway (Svalbard), Russia, the United States (Alaska) and Canada. These five nations are the signatories of the International Agreement on the Conservation of Polar Bears, which mandates cooperation on research and conservations efforts throughout the polar Bear's range.
There are 19 generally recognised, discrete sub populations, and these sub populations display seasonal fidelity to particular areas. However, DNA studies show that they are not reproductively isolated.
Of the 19 recognised polar bear sub populations, eight are declining, three are stable, one is increasing, and seven have insufficient data, as of 2009.
It is difficult to estimate a global population of polar bears as much of the range has been poorly studied; however, biologists use a working estimate of about 20,000–25,000 polar bears worldwide.
Polar bear facts
1. The polar bear is only found in the Arctic region of the northern hemisphere, and NOT AT ALL in the Antarctic region of the southern hemisphere.
2. The polar bear is not only the world's largest land carnivore, it is also the worlds largest bear! An adult male weighs around 350–680 kg (770–1,500 lb), while an adult female is about half that size. This make a large male twice as big as the Siberian tiger!
3. The polar bear is classified as a vulnerable species, with eight of the nineteen polar bear sub populations in decline.
4. The scientific name Ursus maritimus, the Latin for 'maritime bear', due to the animal's native habitat.
5. Polar bears can breed with brown bears to produce fertile grizzly–polar bear hybrids. This indicates that they have only recently diverged and are genetically similar.
6. Research on fossilised bones has shown that there is a giant form of the polar bear once roamed the arctic. Known as Ursus maritimus tyrannus it became extinct during the Pleistocene, and was significantly larger than any living subspecies.
7. Polar bears overheat at temperatures above 10 °C (50 °F), and are nearly invisible under infrared photography.
8. Polar bears are superbly insulated by up to 10 cm (3.9 in) of blubber!
9. The polar bear is an excellent swimmer. In fact they have been seen in open Arctic waters as far as 200 miles from land. It swims in a dog paddle fashion using its large forepaws for propulsion. Polar bears can swim 6 mph.
10. The skin of a polar bear is black while the hair of a polar bear is not white! It is in fact transparent and hollow!
11. When sprinting, a polar bear can reach up to 25 mph!
12. The polar bear has an extremely well developed sense of smell, and is able to detect seals up to 1 mile away and buried under 3 ft of snow.
14. A polar bear can kill an adult walrus, although this is rarely attempted. Why? Because a walrus can be more than twice the bear's weight and has up to three feet long ivory tusks that can be used as formidable weapons.
15. Unlike brown and black bears, polar bears are capable of fasting for up to several months during late summer and early autumn.
16. As of 2008, the World Conservation Union (IUCN) reports that the global population of polar bears is 20,000 to 25,000, and is declining.
17. The Inuit (Eskimo) people of North America and Greenland hunt the polar bear for its meat and fur. However, they cannot eat its liver. Why? Because its holds such a high content of vitamin A, polar bear liver is poisonous to humans!
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Based on an article from http://en.wikipedia.org/wiki/Polar_bear
Images care of http://www.pitara.com/discover/earth/online.asp?story=140 and http://www.theworldwidetraveler.com/destinations/americas-caribbean/canada/manitoba-activities/ and http://www.amnh.org/exhibitions/climatechange/?section=ice&page=life_disrupted and http://www.nationalgeographicstock.com/ngsimages/explore/explore.jsf?p=TUlDSEVMTEUgVkFMQkVSRw==