The grizzly bear is a type of brown bear. Some experts say the grizzly is a subspecies of brown bear, while others say the two bears are the same animal, and "grizzly bear" refers to brown bears that live in the interior of North America.
Brown bears are found all over the world; grizzlies live in a smaller, specific area: the Pacific Northwest. According to the National Wildlife Federation, a distinction is made based on size, color and diet. People in North America use "grizzly bear" to refer to smaller and lighter-colored bears that live in interior areas where there is not a lot of salmon to eat. "Brown bear" refers to larger and darker bears in coastal areas where there are salmon.
Size & appearance
Grizzlies are among the largest living carnivores, according to the Animal Diversity Web (ADW). They are 3.3 to 9 feet (1 to 2.8 meters) in length and weigh 800 lbs. (363 kilograms). Grizzly bear tails are usually 2.6 to 8 inches (65 to 210 millimeters) long. When they stand upright on their hind legs, they can reach 8 feet (2.4 meters) tall.
Grizzly bears have a "dished" or concave face; short, round ears; and a large shoulder hump. They range in color from very light tan — almost white — to dark brown, according to the National Wildlife Federation. The word "grizzly” means "sprinkled or streaked with gray," much like the grizzly bear’s fur, according to the San Diego Zoo. However, the bear's scientific name describes its supposed demeanor: Ursus arctos horribilis.
Habitat & habits
Grizzlies tend to like open areas like tundra, alpine meadows and coastlines. For the most part, grizzly bears live alone. Every now and then, they will meet up with other grizzlies outside of mating season and stand next to each other, but not much socialization will occur.
Grizzlies have a habit of rubbing their backs against trees, but they're not trying to scratch an unbearable itch. Rather, they are communicating with one another by leaving their scent. One scientist who studied bears rubbing their backs in the woods says that by marking trees, male bears get to know one another better, thus reducing fighting among themselves over females.
The biggest gathering of grizzlies is during the salmon run in Alaska. When the salmon migrate upstream for the summer, grizzlies gather to catch their fill of these bountiful fish, according to National Geographic. The largest bears get the first catch.
The fat in salmon help grizzlies bulk up for hibernation in the winter. Before hibernation, these bears will dig dens in hillsides and may line the floor with a bed of leaves. Hibernation lasts four to six months, which can add up to one-third to one-half of their life, according to the San Diego Zoo.
Grizzlies like to spend their days awake and hunting, but if humans are around they have been known to switch to a nightly schedule. Most brown bears are most active during early morning and dusk.
Grizzlies are omnivores, which means they eat vegetation and meat. A grizzly’s diet can consist of fruit, nuts, leaves, berries, roots and other animals. Animal meals can be as small as rodents or as large as moose since these bears are at the top of the food chain. During hibernation, grizzlies don’t need to eat. They live off of the fat stored in their bodies.
Mating season for grizzly bears is from May to July, according to ADW. Fertilized eggs start to develop but implantation in the uterus is usually delayed until November, when the female is hibernating. After a gestation period of six to eight weeks, two or three babies, called cubs, are born.
Cubs are naked, blind and helpless and weigh only 12 to 24 ounces (340 to 680 grams). While the mother continues to hibernate, her cubs will nurse and play, even though their eyelids are sealed shut. After six weeks the cubs' eyes open. By spring they have fur and teeth, as well.
At 18 to 30 months, cubs are weaned, and by the age of 2 or 3, they are ready to leave their mothers. At 4 to 6 years of age the cubs are mature enough start mating, according to ADW. Grizzlies tend to live around 25 years, on average.
Traditional classification of bears relied on data based on bones and body structure. At one time, over 90 subspecies were proposed based on geographical differences, according to the authors of a chapter on grizzly bears in in the book "Wild Mammals of North America" (John Hopkins, 2003). However, DNA analysis has cast doubt on the historic taxonomic classification of bears. The authors say that DNA does not support calling the grizzly bear a subspecies of brown bear. Nevertheless, the authors state that additional research is needed before drastically changing the current taxonomy.
With that in mind, here is the current taxonomy of grizzly bears, according to the Integrated Taxonomic Information System (ITIS):
Kingdom: Animalia Subkingdom: Bilateria Infrakingdom: Deuterostomia Phylum: Chordata Subphylum: Vertebrata Infraphylum: Gnathostomata Superclass: Tetrapoda Class: Mammalia Subclass: Theria Infraclass: Eutheria Order: Carnivora Suborder: Caniformia Family: Ursidae Genus: Ursus Species: Ursus arctos Subspecies: Ursus arctos horribilis
According to the International Union for Conservation of Nature (IUCN), brown bears are not threatened or at risk of becoming endangered; however, the organization does not have separate numbers for grizzlies.
According to the Defenders of Wildlife, there were once about 50,000 grizzly bears in North America. Today, fewer than 1,500 grizzlies remain in the lower 48 states. There are about 31,000 in Alaska. According the San Diego Zoo, there once were 86 different kinds of grizzlies and brown bears in North America. Many of them have been killed off by the European colonization.
The U.S. Endangered Species Act has protected grizzlies from being hunted and has helped them be reintroduced to some of their former habitats.