Although sometimes portrayed in the media as voracious predators, grizzly bears are normally reclusive creatures. Grizzly bears are intelligent, curious, and have excellent memory, particularly regarding where food sources are located.
They have good eyesight and excellent senses of hearing and smell. Grizzly bears are active during the day and night, but will often alter their habits to avoid humans in areas of high human use.
In the heat of the day, grizzly bears will rest in day beds in dense vegetation, including willows, alders, dense forest, and tall grass. Most grizzly bears spend their time alone except when breeding or raising cubs.
Grizzly bears often live to be around 20 to 25 years of age Mating occurs from May through July with a peak in mid-June. Female grizzlies begin bearing young at 3 to 8 years of age, and litter size varies from one to four cubs, with an average litter of two.
Grizzly bears are opportunistic omnivores. In Washington and Idaho, a typical grizzly bear diet is less than 10% fish or meat, and much of the meat is carrion from winter-killed deer and elk. In areas where animal matter is less available, grasses, roots, bulbs, tubers, and fungi are important parts of the grizzly diet.
Grizzly bears visit wetlands in the spring for succulent plants that are easy to digest and are high in nutrients. Summer foods include thistle, cow parsnip, mushrooms, roots, spawning fish, wild berries, and insects (including clusters of adult moths at high-elevations). Fall foods include berries very important, plants, and ants.
During years when there are shortages of natural food sources, conflicts between humans and grizzly bears are more frequent, resulting in higher numbers of human- caused grizzly bear mortalities due to defense of life or property, and management removals of nuisance bears.
A bear’s body language can help reveal its mood. Bears may stand on their hind legs or approach to get a better view, but these actions are not necessarily signs of aggression. In general, bears show agitation by swaying their heads, huffing, popping their jaws, blowing and snorting, or clacking their teeth. Lowered head and laid-back ears also indicate aggression.