Most Black Bears hibernate for up to seven months, and do not eat, drink, urinate, or exercise the entire time. In the South, where plant food is available all year, not all bears hibernate—but pregnant females do. The female gives birth to 1-6 cubs (usually 2 or 3) in January, while she is deep asleep in her den. The newborn cubs snuggle next to her for warmth and nurse while she fasts. They grow from a birth weight of 200-450 g each (about 7-16 pounds) to the 2-5 kg they will weigh when the family leaves the den in the spring. Black Bears eat a little meat, and some insects, but they rely on fruit, nuts, and vegetation for the bulk of their nutritional needs. They are not all black. Most are, with brown muzzles, but in some western forests they are brown, cinnamon, or blond, and a few, in southern Alaska and British Columbia, are creamy white or bluish-gray.

Adaptation: In the Black Bear, Ursus americanus, the evolution of typically carnivorous, sharp shearing molars into the flat crushing teeth, typical of bears, is evident.

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Mammal Species of the World