The Grizzly Bear (Ursus arctos horribilis) is a large bear from North America sometimes referred to as the Brown Bear or Silvertip Bear. The current range of the grizzly bear extends from Alaska, south through much of western Canada and into parts of the northwestern United States extending as far south as Yellowstone and Grand Teton National Parks, however, is most commonly found in Canada.
There are currently about 60,000 wild grizzly bears located throughout North America.
Grizzly Bear Description
Male grizzly bears can grow to be a height of 8 feet tall (2.44 metres) when they are standing on their hind legs and they weigh between 400 and 600 pounds. Grizzly bears have very powerful muscles in their legs which enables them to stand and walk short distances on their hind legs. Their coat colours vary from region to region from dark brown to reddish brown, they can also be black or very light beige in colour.
Grizzly bears have long white-tipped hairs along the shoulders and back, which give the bear a grizzled appearance. The grizzly bear has a large hump over the shoulder, which is a muscle mass used to power the forelimbs in digging.
A grizzly bears head is large and round and they have a concave face (curved like a segment of the interior of a circle or hollow sphere). Grizzly bears are very fast runners, despite their huge size, and can run at speeds of 25 miles per hour (40 kilometres per hour). However, they are slower running downhill rather than uphill because of the large hump of muscle over the shoulders.
Grizzly bears have very long, curved claws that distinguishes them from other bear species. Their claws are about the length of an adult human finger. They have large plantigrade feet (heel and sole touch the floor).
Grizzly Bear Habitat
Grizzly bears prefer dense boreal forest areas, alpine tundra regions and river valleys.
Grizzly Bear Diet
Although grizzly bears are thought of to be carnivores, they are actually omnivores as their diet consists of both animals and plants. Their prey includes large mammals such as moose, deer, sheep, elk, bison, caribou and even black bears.
During early spring, as the bears emerge from their dens, elk and bison calves are actively preyed upon. The bear will move in a zig-zag pattern, nose to the ground, hoping to find unsuspecting animals to feed on. In coastal areas grizzly bears also feed up on fish such as salmon, bass and trout. Coastal grizzly bears tend to grow larger than inland bears because of their protein enriched fish diets. Grizzly bears also support their diet with pine nuts, sedges, bulbs, roots, berries, grasses and various rodents.
When winter is approaching, grizzly bears will gain hundreds of pounds of fat to help them survive the winter when hibernating. This is particularly true for pregnant females who give birth to cubs that weigh only one pound and then nurse them to about 20 pounds before emerging from the den in April to May. Some bears do not hibernate if food sources are abundant throughout the year.
Grizzly Bear Behaviour
Grizzly bears are solitary, except for mothers with cubs, however, they do not appear to be territorial. In coastal areas the grizzly bear congregates alongside streams, lakes and rivers during the salmon spawn.
Grizzly bears hibernate during the winter for 5 – 8 months and usually dig their dens on north-facing slopes to ensure good snow cover.
Grizzly bears make a loud roar if they are injured, however, they will normally warn other bears of danger by huffing or making chomping sounds with their teeth.
Grizzly Bear Reproduction
The grizzly bear breeding season is from May to June. Females (sows) produce 1 to 3 cubs after a gestation period of 63 – 70 days. Cubs are small and weigh only about 500 grams (one pound). A sow is very protective of her offspring and will attack if she thinks her cubs or herself are being threatened. The cubs stay with their mother for 2 – 4 years. Male and female grizzly bears are only together during the breeding season. Females have their first young at around 7 years old and will leave 3 – 4 years between litters. Female grizzly bears can reproduce up to the age of 30 years old if they live that long.
Grizzly bears can live up to 30 years in the wild, though 20 to 25 is normally the average age.
Grizzly Bear Conservation Status
The grizzly bear is listed as threatened in the contiguous United States and endangered in parts of Canada. Threats include hunting and habitat encroachment, such as logging and road construction.
The protection of key habitat surrounding the grizzly bears core home in Yellowstone and Glacier National Parks is essential to their survival.