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!
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.
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.
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.