Brown Bear

SUBFAMILY URSINAE
Ursus arctos

APPEARANCE The brown bear (sometimes called a grizzly in North America) is a large animal, usually dark brown in color, though it can vary from a light creamy shade through to black. The long guard hairs over the shoulders and back are often light colored at the tips which, from a distance, give a grizzled appearance. The brown bear is characterized by a distinctive hump on the shoulders, a slightly dished profile to the face, and long claws on the front paws.

SIZE There is considerable variability in the size of brown bears from different populations, depending on the food available. Determining representative weights of specific populations is also difficult as there are seasonal considerations to take into account-for instance, some bears can weigh almost twice as much in the fall as they might weigh in spring. Adult males may weigh 135 to 390 kilograms (300 to 860 pounds) compared with 95 to 205 kilograms (205 to 455 pounds) for female s. At birth, cubs weigh 340 to 680 grams (11 ounces to 1 pound 6 ounces). The largest bears are found on the west coast of British Columbia and Alaska, and on offshore islands along coastal Alaska, such as Kodiak and Admiralty. There, males average over 300 kilograms (660 pounds) and females over 200 kilograms (440 pounds). Brown bears from the interior ranges of North America, Europe, and the sub Arctic are roughly two-thirds the size of their Alaskan and Kamchatkan cousins.

HABITAT Brown bears occupy the widest range of habitats of any bear species including dense coastal forests, boreal forests, sub alpine mountain areas, tundra, deciduous forests, and desert and semi-desert areas. They were once abundant on the central plains of North America and throughout much of Europe, but have since been exterminated from most of these areas.  

DISTRIBUTION The range of the brown bear is the widest of any species of bear in the world. They are found in localized populations in eastern and Western Europe, across northern Asia, portions of the Himalayan Mountains, and on the island of Hokkaido in Japan. In North America, brown bears are found in western Canada, Alaska, and in the states of Wyoming, Montana, Idaho, and Washington.

REPRODUCTION
Female brown bears reach sexual maturity at three-and-a-half to seven years of age. Males may become sexually mature at a similar age but are probably not large enough to be able to enter the breeding population until they a re eight to ten years old. Mating takes place from early May to the middle of July but implantation does not occur until about October or November. The young are born from about January to March. The litter size ranges from one to four, but two is most common. Cubs remain with their mothers usually for at least two-and-a-half years, so the most frequently a female can breed is every three years. In some areas, such as near the Arctic coast, the breeding interval is considerably longer. Longevity in the wild is 20 to 25 years although rarely animals in excess of 35 years of age have been reported.

SOCIAL SYSTEM
Under most circumstances, brown bears live as lone individuals, except for females accompanied by their cubs. During the breeding season, a male may attend a female for up to two weeks for mating. Brown bears are distributed in overlapping home ranges and male home ranges are larger than those occupied by females. Despite their propensity for a solitary existence, brown bears congregate at high densities where food is abundant, such as at salmon streams or garbage dumps. In such circumstances, adult males are the most dominant individuals.

DIET Brown bears mainly eat vegetation such as grasses, sedges, bulbs, and roots. They also eat insects such as ants, fish, and small mammals. In some areas they have become significant predators of large hoofed mammals such as moose calves, caribou, and elk calves.

Image by David Kirshner
From Ian Stirling, ed. Bears, Majestic Creatures of the Wild.
Emmaus, Pennsylvania: Rodale Press, 1993. 240 pages.