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Bears: Ursidae

Behavior And Reproduction

Bears maintain a solitary lifestyle, living alone, except when mating and rearing their young. When food is plentiful, they share but keep their personal space. Bears are usually crepuscular (active at dawn and dusk). Their excellent memory enables them return to past food sources. They are agile tree climbers and fast runners, reaching speeds of up to 30 miles per hour (48 kilometers per hour). Polar bears and Asiatic black bears are expert swimmers.

Most bears mate during spring or summer, but the fertilized egg undergoes delayed implantation, during which it takes up to six months to attach to the uterus and start developing. As a result, cubs are born tiny, ranging in weight from about 11 ounces (325 grams) in sun bears to 21 ounces (600 grams) in polar and brown bears. Most sows have two cubs, although some have as many as five. Depending on the species, cubs may stay with their mothers for one to more than four years.

SURVIVING IN THE ARCTIC

The polar bear has a dense underfur next to its skin and a water-repellent outer fur, called guard hairs. The hairs are clear, hollow tubes that conduct sunlight to the black skin, where heat is absorbed. The clear tubes reflect sunlight, making the outer coat appear white. Blending in with the whiteness of the ice and snow, the polar bear can easily sneak up on its prey. The hollow hairs also keep the bear afloat when swimming. A thick layer of blubber, or fat, further insulates the body from the cold. Compact ears also prevent heat loss. Fur-covered feet serve as snowshoes, while thickly padded soles provide traction against slippage on ice.

Additional topics

Animal Life ResourceMammalsBears: Ursidae - Physical Characteristics, Behavior And Reproduction, American Black Bear (ursus Americanus;): Species Accounts, Giant Panda (ailuropoda Melanoleuca): Species Accounts - GEOGRAPHIC RANGE, HABITAT, DIET, BEARS AND PEOPLE, CONSERVATION STATU