The family Ursidae has eight species of omnivorous bears that have large claws and teeth; small eyes and ears; short tails; and long, rough fur. They range in weight from 55 pounds for the sun bear of Asia to 1,700 pounds for the polar bear of the Arctic region.
Most species of Ursidae are large, robust animals. They are mammals and generally socialize only during mating season. Males monitor females for estrus in their range, which is large because they eat a lot of diverse foods, and stay with the females for a few days while they are receptive. Mothers give birth to one to four young at intervals of one to four years. In the wild bears may live for 25 years; in captivity some have lived for 50 years. Bears may seem awkward because of their shuffling gait but can run fast, climb and swim.
Bears are on all continents except Australia and Antarctica. They live in diverse habitats, but access to water is important. They are most abundant in temperate and forest regions but can be found in most habitats throughout their distribution, including deserts, mountains, grasslands, Arctic tundra and ice floes.
Their distribution is mostly in the Northern Hemisphere, but they once had ranged as far south as the Andes Mountains of South America, the Atlas Mountains of northwestern Africa and the Sunda Shelf region of Sumatra, Borneo and Java. Their southerly distribution is now reduced because of hunting and loss of habitat.