While grizzly bears are powerful and fearsome predators, human activities have caused a significant drop in their numbers over the past 200 years. Brown bears and grizzly bears are actually the same species. Grizzly bears were named as such because of the unique "grizzled" coloration of their fur.
1. Scientific & Common Names
4. Present Status
Scientific & Common Names
Kingdom - Animalia
Phylum - Chordata
Class - Mammalia
Order - Carnivora
Family - Ursidae
Genus - Ursus
Species - U. arctus
Subspecies - U. a. horribilis, U. a. middendorffi, U. a. gyas
Common Names - Grizzly, North American Brown Bear, Silvertip Bear, Kodiak Bear (U. a. middendorffi), Pensinsular Grizzly (U. a. gyas)
Grizzly bears received their name because their brown fur is often tipped with white, lending them a grizzled appearance. Female grizzly bears often weigh between 700 and 800 pounds, but males can weigh up to 1,700 pounds. Grizzly bears have powerful bodies with large shoulder humps, long claws on their forepaws, and excellent hearing. Their faces are dished with long snouts, rounded, short ears, and keen, dark eyes.
Of all North American mammals, the grizzly bear has the second slowest reproduction rate after that of the musk ox. Females cannot reproduce until they are at least 4 years old, but sometimes a female will be 9 years of age before she has her first set of cubs. Grizzlies, like most bears, mate in late spring or early summer. However, the embryo does not implant in the female's uterus or develop until she enters her den for the winter. She will give birth in her den in January or February. The average litter size is 2 cubs, and they will stay with their mother for 2 or 3 years. Female grizzlies only have a litter of cubs every 3 years.
Grizzlies eat both plant matter and animal flesh. In areas where salmon are common, they fish frequently and grow to larger sizes than inland grizzlies. They also hunt the young of hoofed animals like deer and elk. Although they appear large and ungainly, grizzlies are surprisingly fast runners, having been clocked at speeds of up to 30 miles per hour. Grizzly bears are usually solitary animals, but sometimes the ranges of several bears will overlap.
The historic range of grizzly bears at one time extended from the Mississippi River all the way to the Pacific Ocean. They were also found as far south as northern Mexico and north through Canada and into Alaska. However, because of farming, development, and other human activities, grizzlies have lost over 98 percent of their historic habitat.
Biologists believe that only about 1,000 grizzlies live protected by law in the continental United States. They also roam in Canada and Alaska, but there they are often pursued by big game hunters. Two subspecies, the California grizzly (U. a. californicus) and the Mexian grizzly (U. a. nelsoni) have gone extinct in the 20th century.