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Ursus arctos (Grizzly Bear)
The largest of all living carnivores, an adult brown bear may be up to 9 feet long and weigh up to 1,650 pounds. Fur is usually dark brown, but varies from cream to almost black.
Each broad, flat foot bears five toes armed with non-retractible claws. Brown bears have poor eyesight but acute senses of smell and hearing.
Distribution and Habitat
Brown bears are found in extremely small numbers from western Europe to eastern Siberia, as well as in the Middle East, the Himalayas, and on the Japanese island of Hokkaido. They are more numerous in North America, where they range from Alaska and western Canada, south through the Sierra Nevada and Rockies into northern Mexico. They occupy a variety of habitats, from desert edges to high mountain forests and ice fields, as long as there is some area with dense cover in which to shelter.
Although brown bears are classified as carnivores the majority of their diet actually consists of plant matter. In spring, grasses, sedges, roots, moss and bulbs make up most of the diet. During summer and early autumn, berries are important, with bulbs and tubers also eaten. Fungi and roots are taken at all times of the year. The amount and type of animals taken varies by region. Those in the Canadian Rockies, for example, are quite carnivorous, hunting moose, elk, mountain sheep and goats. In Alaska they have been observed eating carrion and occasionally capturing young calves of caribou and moose. Grizzlies are also well known for feeding on salmon during the summer spawning runs. Individual bears tend to have specific food preferences, with some eating far more meat than others, and some are also picky about what plants and animal parts they will and will not eat.
Breeding takes place from May to July, but the fertilized eggs are not implanted until October or November. Births occur from January to March after a total gestation ranging from 180 to 266 days. Two cubs are generally born per litter. They are weaned at 5 months of age but remain with the mother until at least their second spring of life. Sexual maturity is reached at 4 to 6 years of age, but growth continues until the 10th or 11th year. Brown bears in the wild may live 25 years or more.
Other Habits and Behaviors
Brown bears may be active at any time of the day, but generally forage in the morning and evening and rest in dense cover by day.
Individual bears maintain home ranges averaging about 20 square miles. Home ranges overlap extensively, but territorial defense is rare.
Grizzlies are generally solitary, but they may gather in large numbers at major food sources.
Young brown bears climb trees well, though slowly and deliberately, but adults rarely do so.
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This page was last updated on March 22, 2018.