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.