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Grizzly bears are majestic symbols of the wild. Bears live in and use a variety of habitat types, playing important roles in each one. This makes them an “umbrella species,” meaning that when we protect them and their habitat we also protect many species. Grizzly bears can also help ecosystems by distributing seeds and nutrients through their scat, and occasionally regulating ungulate populations.
Grizzly bears (Ursus arctos horribilis) have concave faces, a distinctive hump on their shoulders, and long claws about two to four inches long. Both the hump and the claws are traits associated with a grizzly bear’s exceptional digging ability. Grizzlies are often dark brown, but can vary from very light cream to black. The long guard hairs on their backs and shoulders frequently have white tips and give the bears a "grizzled" appearance, hence the name "grizzly." The correct scientific name for the species is “brown bear,” but only coastal bears in Alaska and Canada are referred to as such, while inland bears and those found in the lower 48 states are called grizzly bears.
Diet
Grizzly bears are omnivores, and their diet can vary widely. They may eat seeds, berries, roots, grasses, fungi, deer, elk, fish, dead animals and insects. In the late summer and early fall, grizzlies enter hyperphagia, a period of 2-4 months when they intensify their calorie intake to put on weight for winter denning. During this time period they can gain more than three pounds a day!
Population
Historically, there were around 50,000 grizzly bears in North America. Today, there are an estimated 1,800 grizzly bears remaining in five populations in the lower 48 states. Most of these bears are located in the Northern Continental Divide Population (including Glacier National Park) and the Yellowstone Population. Alaska is home to a healthy grizzly (sometimes called brown bear) population.
Habitat & Range
Grizzly bears are found many different habitats, from dense forests to subalpine meadows, open plains and arctic tundra. In North America, grizzly bears are found in western Canada, Alaska, Wyoming, Montana, Idaho and a potentially a small population in Washington. Historically, they could be found from Alaska to Mexico and from California to Ohio.
Behavior
Grizzly bears are normally solitary animals. However, they are not very territorial and they may be seen feeding together where food is abundant, such as at salmon streams and whitebark pine sites. Females will rear their cubs for 2-3 years. When a female grizzly bear leaves her mother, they often set up their home range quite close to their mother’s home range. Males will typically range further, but may also remain close by.
Grizzly bears need to eat a lot in the summer and fall in order to build up sufficient fat reserves to survive the winter denning period. This is particularly true for pregnant females, who must have sufficient fat reserves to give birth to approximately one-pound cubs in January or February and then nurse them to about 20 pounds before emerging from the den in April or May.
Reproduction
Grizzly bears are one of the slowest reproducing land mammals. Females do not typically reproduce until they are four or five years old. Grizzly bears mate between May and July, but the female’s body delays implantation of their eggs in the uterus until October or November. If the female has not gained enough fat over the summer to survive and raise cubs, implantation may not occur. A grizzly’s ability to garner enough quality calories through the summer is not just crucial for her survival, but also for her reproductive ability.
Mother bears rear cubs for two to three years. Males do not help raise the cubs. In fact, males can be a danger to the cubs, so females often avoid male grizzly bears while rearing their cubs.
Mating Season: Early May through mid-July
Gestation: Anywhere from 180-270 days, including delayed implantation.
Litter Size: 1-4 cubs, but average is 2-3