BIO 203


Grizzly bears use the process of sexual reproduction to expand their species.  During the mating season for grizzly bears, usually between June and July, grizzly bears will seek one another out to mate.  Once mating happens, the bears will go their separate ways.  Unlike most animals whose embryos begin to develop right away, a grizzly bear embryo will not begin to develop for until around six months after mating.  The reason for this is because if the female grizzly bear has not accumulated enough winter fat to sustain herself, and also the potential cubs she would have, the embryo doesn't develop.  If the embryo does develop, the cubs are usually born in January, during hibernation.  A female bear usually has between one to three cubs that weigh around one pound (U.S. Department of the Interior, 1995).  The cubs stay alive by drinking milk from the mother and staying warm from her body heat.  By the time the mother bear and cubs come out of the den, the cubs weigh around twenty pounds.  The cubs survive on the mother’s milk for about one year.  After that, they begin to feed on what adult grizzly bears feed on, such as plants, animals, and fish.  They stay with the mother until they are three to four years old.  After they leave the mother, they begin their own life and try to find a mate to breed with.  Only about fifty percent of all bear cubs reach breeding age, which is around 4.5 to 5.5 years old (U.S. Department of the Interior, 1995).  The mortality rate is so high because of a multiple of factors.  Some of these include predation from other bears and wolves, traffic accidents, lack of food, and abandonment by the mother.

A female grizzly and her cubs

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