The polar bear (Ursus maritimus) is a carnivorous bear native largely within the Arctic Circle encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. It is the world's largest bear, together with the omnivorous Kodiak bear (Ursus arctos middendorffi), which is approximately the same size. A boar (adult male) weighs around 350-700 kg (770-1,500 lb), while a sow (adult female) is about half that size.
Although it is closely related to the brown bear, it has evolved to occupy a narrower 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, they spend most of their time at sea. Their scientific name means "maritime bear", and derives from this fact.
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. The polar bear is classified as a vulnerable species, with eight of the nineteen polar bear subpopulations in decline. For decades, large scale hunting raised international concern for the future of the species but populations 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 polar bears remain important in their cultures. Constantine John Phipps was the first to describe the polar bear as a distinct species in 1774. He chose the scientific name Ursus maritimus, the Latin for 'maritime bear', due to the animal's native habitat.
The polar bear was previously considered to be in its own genus, Thalarctos. However, evidence of hybrids between polar bears and brown bears, and of the recent evolutionary divergence of the two species, does not support the establishment of this separate genus, and the accepted scientific name is now therefore Ursus maritimus, as Phipps originally proposed.