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Black bears are the smallest of the three species of North American bears, and also the most abundant and widely distributed. The color of this bear varies from jet black to white, which is very rare. Three colors are common in Alaska: Black, brown and cinnamon. The rare blue (glacier) phase has also been noted in Alaska, with silver-tipped hairs that give a bluish tint in sunlight.
Black Bear or Brown Bear?
Black bears are most easily distinguished from brown bears by their straight facial profile and claws which are sharply curved and seldom over 1 ½ inches in length. Color is not a reliable key in differentiating these bears because both black bears and brown bears have many color phases.
Black bears are generally crepuscular (active at dawn and dusk), although breeding and feeding activities may alter this pattern seasonally. They spend the winter months in a state of hibernation, where their body temperatures drop, their metabolic rate is reduced and they sleep for long periods. Bears enter this dormancy period in the fall, after most food items become hard to find. They emerge in the spring when food is again available. Occasionally, in more southern ranges, bears will emerge from their dens during winter. Females with cubs usually emerge later than lone bears. These dens may located in rock cavities, hollow trees, self-made excavations, even on the ground.
Black bears are omnivorous and creatures of opportunity when it comes to food. There are, however, certain patterns of food-seeking which they follow. Upon emergence in the spring, freshly sprouted green vegetation is their main food item, but they will eat nearly anything they encounter. Winter-killed animals are readily eaten, and in some areas they have been found to be effective predators on newborn moose calves. As summer progresses, feeding shifts to salmon if they are available. In areas without salmon, bears rely primarily on vegetation throughout the year. Berries, especially blueberries, are an important late summer-fall food items. Ants, grubs and other insects help to round out their diet.
Mating takes place from June to July, however, the fertilized egg does not implant in the uterus until the fall (called delayed implantation). Apart from mating season, black bears are solitary, except for sows (females) with cubs. Cubs are born in dens following a seven month gestation. Cubs are born blind, nearly hairless and weigh under a pound. Upon emerging from dens in May, they may weigh about 5 pounds and are covered with fine, wooly hair. One to four cubs are born, but two is most common. Cubs remain with their mothers through the first winter following birth.
Population Status, Threats & Conservation
Black bears once lived throughout most of North America, but hunting and agriculture drove them into heavily forested areas. Residual populations occur over much of the former range in sparsely populated wooded regions and under protection in national parks. They are numerous and thriving, but continue to face threats regionally due to habitat destruction and hunting in the Lower 48 states. Black bear populations in Canada and Alaska are thriving due to the vast expanses of remote forests.
Notebook series, ADFG
Dewey, T. and C. Kronk. 2007. "Ursus americanus" (On-line), Animal Diversity Web