This is especially important for the pregnant female, whose cubs will be born during the winter sleep. All bears, however, eat heavily during summer and autumn to store fat for winter. A bear's winter sleep is not true hibernation, since the body temperature remains high and the animal emerges from the den to walk about on mild winter days. The female gives birth to from 1 to 4 cubs at a time, with a litter every 2 years. The cubs stay with their mother for a year or two, and she defends them against all intruders, including humans and sometimes cannibalistic male bears.
Most animals walk on their toes.
Many are powerful swimmers, and most can climb trees. Of all bears, the polar bear is the strictest carnivore. It eats seals, walrus, fish, caribou, and beached whales, and has been known to graze on grass and seaweed. The Alaska brown bear will eat almost anything, including deer, cattle, and fish. Other bears tend to be omnivorous, eating fruits, roots, berries, and other plant matter, either by choice or when meat and grubs are unavailable.