Brown Bears

Quick Facts

Height: About 3–5 feet at the shoulder and 5–7 feet in length. Very large brown bears can measure almost 9 feet tall when standing on their hind legs.
Weight: Ranges from 200 to 1000 pounds depending on sex, location, and season
Average Life Span: 15–25 years
Did You Know? When laying down to rest, Alaskan brown bears dig “belly holes” to accommodate their food-filled bellies—the bigger the belly, the bigger the hole!

Brown bears (Ursus arctos) can be distinguished from American black and polar bears by their distinct shoulder hump, dish-shaped face, and long claws. They can vary in color from black to blonde.

Brown bears, also known as grizzly bears, can be found in many of our national parks. The name grizzly usually refers to bears living inland, away from the coast. While bears of the same species might look similar, everything from their size, coloring, diet, and sleeping patterns depend on the bear’s location. For example, a bear’s diet varies depending on what foods are available during a specific season in a specific region.

Let’s take a look at two different brown bears, a grizzly bear in Yellowstone National Park and an Alaskan brown bear, to see how they differ in diet, winter dens, and life cycle. For more information about bears and bear behavior in a specific national park, please contact that park.
Brown bear eating salmon
As this Alaskan brown bear at Katmai National Park is doing, bears eat the most fat-rich parts of a salmon (skin, brain, and roe) first.

NPS Photo

What Do Brown Bears Eat?
Brown bears are omnivorous, eating a mixed diet of plants, berries, fish, and small mammals. Unlike black bears, brown bears have long, strong claws that they use to dig for food, pick fruits, and catch prey.
Brown bears are very intelligent, curious, and skilled at finding food. Bears who are fed by humans may begin to associate people with food, and this can become dangerous. So please remember: No matter where you are, don’t feed the bears! Help keep them wild by following these tips on food storage and bear safety.
Grizzly Bear in Yellowstone
Grizzly bears in Yellowstone eat a wide variety of foods. They are effective predators and prey on vulnerable animals such as elk calves and spawning trout, or small mammals and insects. Their long claws and strong shoulders allow them dig efficiently for food. They eat a variety of plants, including pine nuts, berries, grasses, glacier lilies, roots, bulbs, tubers, and dandelions. In the fall, whitebark pine seeds are a preferred food for grizzly bears; the reduction of whitebark pine due to white pine blister rust and other factors may influence grizzly cub production and survival. (Read more about grizzly bear recovery and conservation in Yellowstone.) Grizzlies will also scavenge meat, when available, from elk and bison carcasses or road kill. Grizzly bears spend most of their time feeding, eating up to 30 pounds of food per day to store fat for the winter.
Alaskan Brown Bear
Alaskan brown bears are the largest brown bears and require a very high caloric intake of food. Brown bears in Alaska can eat 80 to 90 pounds of food per day in the summer and fall, gaining around three to six pounds of fat each day, in order to store fat for the winter.
Alaskan brown bears are opportunistic eaters and will eat almost anything. Their diet consists of berries, flowers, grasses, herbs, and roots. They get their protein from beavers, deer, caribou, salmon, carcasses, and other small mammals.
Brown bear's den in Katmai National Park
Brown bear den in Katmai National Park and Preserve

NPS Photo / Mike Fitz

Winter Dens
Most brown bears spend the winter hibernating in dens to avoid the cold weather and lack of abundant food sources. During their winter slumber, bears’ bodies drop in body temperature, pulse rate, and respiration. Their bodies use the fat they stored in the summer as energy.
Grizzly Bear in Yellowstone
Yellowstone grizzlies enter their winter dens between mid-October and early December, when the weather gets cooler. Most grizzly bears, especially mothers with cubs, will sleep through the winter. Some bears may wake up and leave their dens to search for food.
Pregnant female grizzlies give birth during the winter in their dens, usually in late January or February. Mother and cubs remain in their dens for the duration of winter while the mother sleeps and the cubs nurse and grow.
Alaskan Brown Bear
Brown bears in the coldest parts of Alaska hibernate through the winter. Hibernation can last from five to eight months. Most bears hibernate, but bears in warmer areas, like Kodiak Island off Kenai Fjords National Park, may remain active throughout winter.
During the winter denning period, pregnant Alaskan brown bears give birth. Like the Yellowstone grizzly, Alaskan brown bear cubs spend the rest of winter nursing and gaining weight to prepare to leave the den in the spring. Bears emerge from their dens in April or May.
Grizzly bear with three cubs along river bank
Mother grizzly bear with three cubs in Yellowstone National Park

NPS Photo

Life Cycle
Adult brown bears lead fairly solitary lives but will be found together when there is abundant food or during mating season. The life cycle of brown bears in Yellowstone is very similar to that of a brown bear in Alaska.
Female brown bears do not mate until they are at least four or six years of age. Mating season occurs from mid-May to mid-July and bears will mate with multiple partners during the season.
When the female enters her den in the fall, the embryo will start to develop. After about eight weeks, or in January or February, the cubs are born.
Typically a female will have a litter of one to three cubs, although litters of four occur occasionally. They are born tiny and hairless, sometimes weighing less than half a pound. They spend the winter sleeping and nursing, warm in their dens with their mother.
By the time spring arrives, the cubs will have grown and weigh anywhere between four and eight pounds. Mother and cubs emerge from their dens in search of food. Male grizzlies have no part in raising cubs. In fact, male grizzlies may pose a threat to cubs, and mother bears are very protective of her young. Cubs will stay with their mother for about two years learning survival skills. After two or three years, a female bear is ready to mate again.

Last updated: March 23, 2017

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