The Polar Bear (Ursus maritimus) 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 350–700 kg (770–1,540 lb), 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 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 the largest living species of terrestrial predator. The only other bear of a similar size is the Kodiak bear, which is a subspecies of brown bear. Adult male polar bears weigh 350–700 kg (770–1,540 lb) and measure 2.4–3 metres (7 ft 10 in–9 ft 10 in) in total length. The Guinness Book of World Records listed the average male as having a body mass of 385 to 410 kg (849 to 904 lb) and a shoulder height of 133 cm (4 ft 4 in), slightly smaller than the average cited for male Kodiak bears. Around the Beaufort Sea, however, mature males reportedly average 450 kg (1,000 lb). Adult females are roughly half the size of males and normally weigh 150–250 kg (330–550 lb), measuring 1.8–2.4 metres (5 ft 11 in–7 ft 10 in) in length. Elsewhere, a slightly larger estimated average weight of 260 kg (570 lb) was claimed for adult females. When pregnant, however, females can weigh as much as 500 kg (1,100 lb). The polar bear is among the most sexually dimorphic of mammals, surpassed only by the pinnipeds such as elephant seals. The largest polar bear on record, reportedly weighing 1,002 kg (2,209 lb), was a male shot at Kotzebue Sound in northwestern Alaska in 1960. This specimen, when mounted, stood 3.39 m (11 ft 1 in) tall on its hindlegs. The shoulder height of an adult polar bear is 122 to 160 cm (4 ft 0 in to 5 ft 3 in). While all bears are short-tailed, the polar bear's tail is relatively the shortest amongst living bears, ranging from 7 to 13 cm (2.8 to 5.1 in) in length.
The polar bear is found in the Arctic Circle and adjacent land masses as far south as Newfoundland Island. Due to the absence of human development in its remote habitat, it retains more of its original range than any other extant carnivore. 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. They can occasionally drift widely with the sea ice, and there have been anecdotal sightings as far south as Berlevåg on the Norwegian mainland and the Kuril Islands in the Sea of Okhotsk. It is difficult to estimate a global population of polar bears as much of the range has been poorly studied; however, biologists use a working estimate of about 20,000 to 25,000 polar bears worldwide.
Unlike grizzly bears, polar bears are not territorial. Although stereotyped as being voraciously aggressive, they are normally cautious in confrontations, and often choose to escape rather than fight. Satiated polar bears rarely attack humans unless severely provoked. However, due to their lack of prior human interaction, hungry polar bears are extremely unpredictable, fearless towards people and are known to kill and sometimes eat humans. Many attacks by brown bears are the result of surprising the animal, which is not the case with the polar bear. Polar bears are stealth hunters, and the victim is often unaware of the bear's presence until the attack is underway. Whereas brown bears often maul a person and then leave, polar bear attacks are more likely to be predatory and are almost always fatal. However, due to the very small human population around the Arctic, such attacks are rare.
- Shelter: Big Cat Cave, Snow Cave
- Enrichment: Cardboard Box, Horse Dummy, Ice Block, Live Prey, Scratching Post
- Animal Food: Fish, Meat