Introductionbear, large mammal of the family Ursidae in the order Carnivora, found almost exclusively in the Northern Hemisphere. Bears have large heads, bulky bodies, massive hindquarters, short, powerful limbs, very short tails, and coarse, thick fur. They walk on the entire sole of the foot and normally move with a slow, ambling gait. However, they are capable of moving with great speed when necessary and some achieve bursts of 35 mi (56 km) per hour. Most bears can climb trees and swim well. They stand on the hind feet to reach objects with their paws. They have large, strong, non-retractile claws, used for catching prey and for digging. Their teeth are adapted to grinding as well as tearing. Nearly all species are omnivorous, feeding on fruits, roots and other plant matter, honey, carrion, insects, fish, and small mammals.
Adult bears are solitary except during the mating season. Groups may feed together where quantities of food are available, but there is little social contact. In cold climates bears sleep through most of the winter in individual dens made in caves or holes in the ground. This sleep is not a true hibernation, as the bear's metabolism remains in a normal state and it may wake and emerge during warm spells. The young, usually twins, are born during winter in a very immature state. Cubs stay with their mothers for about a year, and females usually mate only every other year. Bears are not generally subject to predation, unless they are in a weakened condition. A bear is a formidable adversary and may attack a human if it is injured or startled.