The polar bear (Ursus maritimus) is the largest bear species and land carnivore, with males weighing up to 800 kg (1,760 lb), and is uniquely adapted to the Arctic with white fur, black skin, and large paws for walking on ice and swimming. First classified as a brown bear by Carl Linnaeus in 1758, it was formally described as a distinct species by Constantine John Phipps in 1774, and given its common name by Thomas Pennant in 1771, though it is closely related enough to brown bears to interbreed. As a marine mammal that depends on sea ice, it is a specialized predator of seals—particularly ringed seals—which it ambushes from breathing holes or the ice edge, while also hunting walruses and beluga whales. Classified as vulnerable by the IUCN with an estimated population of 22,000–31,000, its primary threat is climate change, which reduces sea ice and forces bears onto land, leading to malnutrition, starvation, and increased conflicts with humans. These solitary animals give birth in winter dens, and they hold deep cultural significance for Inuit peoples, who call them nanook, appearing prominently in art, folklore, and modern culture.