While they mainly eat vegetation, bears will eat carrion, and small or weak animals. Bears living near the coast will consume fish in season. Grizzlies will forage over a range as large as 1000 square miles, according to the Official World Wildlife Federation Guide to Endangered Species. This depends largely upon the availability of food and where food is abundant. A grizzly will have a much smaller range.
Grizzlies are solitary animals except when mating or rearing cubs.
Mating takes place in late spring. By the time the female bear has hibernated, fertilization will have taken place. Cubs are born in late January or early February and weigh about one pound. When they leave the den in early spring, cubs weigh between five and ten pounds. In preparation for hibernation grizzlies must consume enough food to gain a layer of fat, which can be up to eight inches thick in some places.