Sedating a shark in the wild
Modern methods of tracking polar bear populations have been implemented only since the mid-1980s, and are expensive to perform consistently over a large area.
In Nunavut, some Inuit have reported increases in bear sightings around human settlements in recent years, leading to a belief that populations are increasing.
Elsewhere, a slightly larger estimated average weight of 260 kg (573 lb) was claimed for adult females.
The claws are deeply scooped on the underside to assist in digging in the ice of the natural habitat.
rather than indicating that they have only recently diverged, the new evidence suggests more frequent mating has continued over a longer period of time, and thus the two bears remain genetically similar.
However, because neither species can survive long in the other's ecological niche, and because they have different morphology, metabolism, social and feeding behaviours, and other phenotypic characteristics, the two bears are generally classified as separate species.
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 conservation efforts throughout the polar bear's range.
Polar bears hunt their preferred food of seals from the edge of sea ice, often living off fat reserves when no sea ice is present.
One bear swam continuously for 9 days in the frigid Bering Sea for 700 km (400 mi) to reach ice far from land. During the swim, the bear lost 22% of her body mass and her yearling cub died.
Many attacks by brown bears are the result of surprising the animal, which is not the case with the polar bear.
While they are rare north of 88°, there is evidence that they range all the way across the Arctic, and as far south as James Bay in Canada.
Their southernmost range is near the boundary between the subarctic and humid continental climate zones.