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Posted By Elena Bajo, Wednesday, June 25, 2008

Polar Bear

Ursus maritimus

Polar bears are among the largest predators in the world. They range in color from pure white after a molt to a yellowish shade resulting from solar oxidation or staining by oil from seal blubber. Their skin, nose and lips are black in color. Polar bears’ long neck and narrow skull aid in streamlining the animal in water, and their large, flat and oar-like front feet make them strong swimmers. Their fur is thicker than any other bears’ even covering their feet, for warmth and traction on ice. Polar bears also have a thick layer of blubber which provides buoyancy and insulation.

Height 8 to 10 feet
Weight Adult males 550-1700 lbs; females 200 - 700 lbs
Lifespan 20 - 25 years


Staples Almost exclusively feed on ringed seals and to a lesser extent bearded seals
Also eat walrus, beluga whale and bowhead whale carcasses, birds, vegetation and kelp


The World Conservation Union (IUCN) estimates that there are between 20,000-25,000 polar bears in the world.


Polar bears are distributed throughout the arctic region in 19 subpopulations. Alaska, Canada, Russia, Greenland and Norway have polar bear populations.


Highly dependant on older stable pack ice in the arctic region, polar bears spend much of their time on the ice hunting, mating and denning. They are generally solitary as adults, except during breeding and cub rearing.

Unlike brown bears, non breeding females and males do not hibernate or den in the winter. Pregnant polar bears need to eat a lot in the summer and fall in order to build up sufficient fat reserves for surviving the denning period, during which time they give birth to one-pound cubs and then nurse them to about 20-30 pounds before emerging from the den in March or April.

Mating Season Late March through May
Gestation About 8 months with delayed implantation
Litter size 1-4 cubs; 2 cubs most common 
Female bears locate denning sites in October on thick stable pack ice or on land. The young are born from November through January while the mothers are hibernating. Cubs will remain with their mothers for at least 2 ½ years. Female polar bears can produce five litters in their lifetime, which is one of the lowest reproductive rates of any mammal.


Climate change, which is causing the loss of older stable sea ice and the  thinning, disappearance and moving offshore of older sea ice, is reducing essential polar bear habitats and is the great threat to their survival. Loss of sea ice leads to higher energy requirements to locate prey and a shortage of food. This causes higher mortality among cubs and reduction in size among first year cubs and adult males. For example, in Alaska 42% of cubs now reach 12 months of age, down from 65% 15 years ago. Another threat is human-caused mortality. Some bears are attracted by unsecured garbage and animal carcasses. This can eventually lead to conflicts between people and bears and lethal removal of the bear. Illegal killing (poaching) of bears also remains another factor causing their decline.

Legal Status/Protection

The polar bear was listed as threatened under the federal Endangered Species Act* on May 14, 2008. This move officially recognizes that polar bears are threatened with extinction from global warming, which is melting the Arctic sea ice where polar bears hunt for ringed and bearded seals, their primary food source.

In May 2006, the International Union for the Conservation of Nature added the polar bear to its "Red List" of the world’s most imperiled animals, predicting a 30% reduction in the polar bear population in the next 45 years.

*The Endangered Species Act requires the US federal government to identify species threatened with extinction, identify habitat they need to survive, and help protect both. In doing so, the Act works to ensure the basic health of our natural ecosystems and protect the legacy of conservation we leave to our children and grandchildren.

The polar bear is the youngest and largest of the world’s bear species, only matched in mass by the largest of Alaska’s Kodiak grizzlies. It’s also the only completely carnivorous bear, feeding primarily on ringed seals rather than leaves, berries, or bark, and it may be the most hardy mammal in its ability to survive long periods deprived of food and water. Yet this mighty hunter and fierce defender of its young is also among the world’s most vulnerable animals — the polar bear’s might is no match for the greenhouse gas-fueled global warming that’s rapidly melting its sea-ice habitat.


May 14, 2008 - Defenders of Wildlife welcomes decision to list polar bears as threatened under the Endangered Species Act, points out Bush administration still unwilling to address global warming.

Read the Press Release





RANGE: In and around the Arctic Ocean with southernmost occurrence at Canada’s James Bay; populations occur within jurisdictions of the United States ( Alaska), Canada, Denmark (Greenland), Norway, and Russia

THREATS: Primarily melting of sea-ice habitat due to intensifying global warming, in combination with other threats including oil and gas development, environmental contaminants such as PCBs, industrial noise and harassment from increased Arctic shipping and other activities, and overhunting in some areas

POPULATION TREND: Polar bear numbers increased following the establishment of hunting regulations in the 1970s and today stand at 20,000 to 25,000. The rapid decline of Arctic sea-ice due to global warming has reversed this trend, and currently at least five of the 19 polar bear populations including those in Western Hudson Bay are declining. Scientists estimate that if the Arctic continues its melting trend, the worldwide polar bear population will decline by two-thirds by 2050 and will be near extinction by the end of the century. As actual sea-ice melting has proceeded much faster than predicted by scientific models, population declines may occur much faster as well.

Tags:  endangered  Polar bear 

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