Grizzly bears are specially adapted to survive the changing seasons. During warmer months, they eat a massive amount of food so they can live off body fat during the winter, when food is scarce. They may intake 40 kg (90 lbs.) of food each day, gaining over 1 kg (2.2 lbs.) of body weight a day. As omnivores, grizzlies will eat anything nutritious they can find, gorging on nuts, fruit, leaves, roots, fungi, insects, and a variety of animals including salmon and other fish, rodents, sheep, and elk. Their diet varies depending on what foods are available for the season.
In the fall, as temperatures cool and food becomes scarcer, grizzlies dig dens in the sides of hills. They have long rounded claws (the size of human fingers) and a large mass of muscles on their backs that help them dig. These characteristics, along with small rounded ears and white-tipped (or “grizzled”) fur, distinguish grizzly bears from black bears.
The bears settle in their dens to sleep for the winter. While it is not classified as a true hibernation (since the bears can wake up during this time), the deep sleep allows the grizzlies to conserve energy. Their heart rate slows down from 40 beats per minute to 8, and they do not go to the bathroom at all during these months of slumber.
Pregnant grizzly bears even give birth in their sleep! Midwinter, grizzly bear cubs (usually born in pairs) arrive into the world blind, hairless, and toothless. They use what little strength they have to nestle into their mother and nurse. For a month, the cubs feed on their mother’s milk and gain strength. By the time spring comes, the cubs have opened their eyes and grown teeth and fur; the new family is ready to venture outside the den.
The cubs stay under their mother’s care for 2-3 years. While mother grizzlies are fiercely protective of their cubs, nearly half the cubs do not survive past the first year, falling to disease, starvation, and predators like wolves, mountain lions, and adult male grizzlies.
Grizzly bears have a multitude of strengths. They are highly intelligent and have excellent memories. Detecting food from great distances away, grizzlies have an astute sense of smell, even better than that of a hound dog. They are good swimmers and fast runners, reaching speeds as high as 50 km/h (35 mph) over land. Young grizzlies also have the ability to climb trees to evade danger, but this skill fades as they become bigger.
In the United States, 50,000 grizzly bears once roamed the land from the Pacific Ocean to the Great Plains, but when pioneers came in the 1800s they wiped out much of the continental U.S. grizzly bear population. Now only about 1200 – 1400 grizzly bears live in five separate populations in the northwest U.S., including areas in Montana, Idaho, Wyoming, and Washington, and the grizzly bear is a protected species under the Endangered Species Act.
In Canada and Alaska, grizzly bear numbers are much higher, with about 30,000 grizzlies in the wild.
Grizzly bears are threatened by habitat loss due to logging, development, and mining. Human interaction also poses a threat to grizzlies. When bears are drawn close to humans, attracted by livestock, garbage, and other food, they are often exterminated. Furthermore, in Canada, people hunt grizzlies for trophy (where it is legal to do so). In the U.S., sometimes grizzlies are shot by people mistaking them for black bears, which are not protected.
What You Can Do to Help
If you would like to help grizzlies, you can donate to organizations such as Defender of Wildlife and National Wildlife Federation, which help preserve grizzly habitat and work toward minimizing human-bear conflicts (with measures like bear-resistant dumpsters and electric fences).
When living in or visiting grizzly bear habitat, do not feed the bears, and keep all garbage securely contained.
Grizzly Bear Distribution
Grizzly Bear Resources
- National Geographic’s Grizzly Bear Page
- National Wildlife Federation’s Grizzly Bear Page
- Defenders of Wildlife’s Grizzly Bear Page
- “Getting to Know the Grizzly Bear” PDF, U.S. Fish and Wildlife Service, Mountain-Prairie Region
- National Geographic Kids Creature Feature: Brown Bear
- San Diego Zoo Animal Bytes: Brown Bear
Blog Posts about the Grizzly Bear
- Grizzly Bear Cam at Washington Zoo - August 2, 2011