The polar bear (Ursus maritimus) is a bear native to the Arctic Ocean and its surrounding seas. The world's largest carnivore found on land, an adult male weighs around 400–680 kg (880–1,500 lb), while an adult female is about half that size. Although it is closely related to the brown bear, it has evolved to occupy a narrow ecological niche, with many body characteristics adapted for cold temperatures, for moving across snow, ice, and open water, and for hunting the seals which make up most of its diet. Although most polar bears are born on land, it spends most of its time at sea, hence its name meaning "maritime bear", and can hunt consistently only from sea ice, spending much of the year on the frozen sea.
The polar bear is classified as a vulnerable species. For decades, unrestricted hunting raised international concern for the future of the species; populations have rebounded after controls and quotas began to take effect. For thousands of years, the polar bear has been a key figure in the material, spiritual, and cultural life of Arctic indigenous peoples, and the hunting of polar bears remains important in their cultures.
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.
On May 14, 2008, the United States Department of the Interior listed the polar bear as a threatened species under the Endangered Species Act. 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.