Polar bears are one of the most recognizable animals on Earth, and they are also among the most specialized. They live across the Arctic and depend heavily on sea ice, which they use to travel, hunt, rest, mate, and in some regions, build dens for their young.

The scientific name of the polar bear is *Ursus maritimus*, which means sea bear, and that name fits well because life for this species is tied to the ocean and frozen sea ice. Adult males are much larger than females. Males can weigh about 800 to 1,300 pounds, while females usually weigh about 300 to 700 pounds. They are the largest bear species and one of the largest carnivores on land.

Polar bears are built for cold conditions. They have thick fur, a layer of fat called blubber, black skin beneath their coat, and large paws that help them move across ice and swim through frigid water. Their fur can look white, but it helps them blend into snow and ice, while their dark skin helps absorb heat from the sun. Their paws are broad and act a bit like snowshoes, which helps distribute their weight on ice.

Their diet is dominated by seals, which they hunt on sea ice. Polar bears are powerful hunters and depend on the ice edge and openings in the ice to find prey. They can swim long distances and spend much of their lives moving between ice floes as conditions change. In winter, they may sleep in shallow pits dug into snow, and in summer they sometimes rest on sea ice or shorelines when ice is limited. 

Reproduction is closely linked to Arctic conditions. Females give birth in snow dens, usually in late autumn or early winter, where the cubs stay protected from the harsh environment. The young remain with their mother for about two years as they learn how to survive in the Arctic.

Polar bears are currently listed as vulnerable, with an estimated population of about 22,000 to 31,000. The biggest threat is the loss of sea ice caused by climate change, since the ice is essential to nearly every part of their life. As the Arctic warms, polar bears are spending longer periods on land, where food is harder to find and encounters with people can become more common.