The
polar bear () is a
carnivorous bear whose native range lies largely within the
Arctic Circle, encompassing the Arctic Ocean, its surrounding seas and surrounding land masses. It is a large bear, approximately the same size as the
omnivorous Kodiak bear (
Ursus arctos middendorffi). A boar (adult male) weighs around , while a sow (adult female) is about half that size. Although it is the
sister species of 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
seals, which make up most of its diet. Although most polar bears are born on land, they spend most of their time on the sea ice. 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. Because of their dependence on the sea ice, polar bears are classified as
marine mammals.