(Ursus maritimus)

Habitat: discrete circumpolar areas of seasonal ice formation and favorable habitat for denning; 19 populations ranging across Wrangel Island and western Alaska, northern Alaska, the Canadian Arctic and Hudson Bay, Greenland, Svalbard-Franz Josef Land, and central Siberia

Behavior/Rhythm: solitary except when scavenging or at play; inactive two-thirds of the time, either sleeping, lying, or awaiting a kill; females hibernate prior to giving birth; others hibernate only during periods of extreme weather

Feeding: carnivorous; seals are its primary prey, especially ringed seals; eats smaller mammals and fish, and scavenges carrion of walruses and whales; prefers high-caloric blubber to meat; though polar bears eat summer vegetation while on land, they derive little nutrition from it

Breeding: after mating season from March to June, females retire in late fall to dens dug out of snow, on the pack ice, or on permafrost a few miles from the coast; delayed implantation can extend gestation up to 300 days; litters of one to three cubs stay in dens with their mother until March or April

Size: largest land carnivore; weighs 900 to 1,600 pounds (410 to 726 kilograms); average weight 1,000 pounds (454 kilograms); largest on record 2,050 pounds (930 kilograms); can lose half of its body weight while living off body fat during summer migration; six to seven feet (two meters) in length

Lifespan: 25 to 30 years in the wild

Status: populations now stable, though warmer polar winters and earlier ice melts could threaten this status