Brown Bear

Description

The brown bear is one of the largest land carnivores on Earth and among the most widely distributed. The term “brown bear” is generally used for the large, dark-furred bears of the coast, where “grizzly bear” refers specifically to the smaller, often lighter-colored subspecies of brown bear, Ursus arctos horribilis which roams the continent’s interior. A second North American subspecies, the Kodiak bear, lives only on the islands of the Kodiak Archipelago in the Gulf of Alaska.

A brown bear’s coat ranges in color from white to pale, almost blond or tan to dark brown or nearly black. Long guard hairs are often tipped with white, giving the animal a “grizzled” look. The species is almost unmistakable at close range: a large muscular hump rises over the shoulders, the face is dished in profile between the eyes and nose, and the ears are short and rounded. That shoulder hump is a mass of muscle anchored to the backbone that powers the front legs. Paired with long, slightly curved front claws, this makes the brown bear a formidable digger able to excavate roots, burrow for prey, and excavate hibernation dens.

The size of a brown bear varies throughout the year, closely tracking the richness and length of the local feeding season. Interior grizzlies in the lower forty-wight are generally the smallest, with males averaging around 400 to 600 pounds (200 to 300 kilograms) and females 250 to 350 pounds (110 to 160 kilograms) at their heaviest. The salmon-fed brown bears of coastal Alaska are far larger, with big males weighing 800 to 1,400 pounds (360 to 365 kilograms) and occasionally exceeding 1,500 pounds (680 kilograms). A large bear standing upright on its hind legs can tower up to ten feet (3 meters) tall. Brown bears can be identified from their black bear cousins by the large shoulder hump, dished face, longer and straighter claws, and a rump that sits lower than the shoulder. Color alone is never a reliable guide since both species come in many shades.

Range and Habitat

The brown bear is the most widely distributed bear in the world, ranging across the northern reaches of three continents. Historically in North America it roamed from Alaska south into Mexico and from the Pacific Coast east to the Great Plains. That range has contracted sharply in the contiguous United States, where brown bears have been eliminated from roughly 98% of their historical range and now persist in fragmented populations in parts of Montana, Wyoming, Idaho, and Washington. Farther north the species remains abundant: Alaska is home to an estimated 30,000 brown bears, and large populations endure across Canada, Russia, and northern Europe.

Brown bears are habitat generalists and are at home in tundra, alpine meadows, forests, prairies, and coastlands alike. They often favor riparian zones along rivers and streams, where food is concentrated and reliable. Because the species lives at densities set almost entirely by the amount of food the land provides, brown bears can be spread thinly across the dry interior or packed remarkably close together where prey is plentiful. Kodiak Island sees some of the highest densities on Earth, with up to 270 bears occupying about 380 square miles (1000 square kilometers). Individual bears roam over large home areas that overlap freely with those of their neighbors.

Diet and Foraging

Brown bears are omnivores whose diet changes dramatically with season, region, and available resources. Despite their formidable strength and reputation as powerful predators, most of a brown bear’s diet is plant-based; in many inland areas, vegetation makes up as much as 80 to 90 percent of what they eat. They forage widely for roots, tubers, grasses, sedges, and forbs, especially in spring when new shoots are abundant. Summer brings a feast of berries such as huckleberries and buffaloberries, which bears consume in enormous quantities to build fat for winter.

They are opportunistic hunters and scavengers as well. When it comes to animal prey, brown bears feed on everything from ants and army cutworm moths to small mammals like ground squirrels, marmots, and voles. Brown bears are expert anglers where fish are available, and coastal populations often depend on the great seasonal runs of spawning salmon. In these cases, bears can consume up to 90 fish in a single day. Large mammals also provide an important source of seasonal protein, especially for interior bears: they will hunt or scavenge moose, elk, caribou, and even bison when calves are plentiful or when weakened adults are around. Brown bears will also readily consume carrion, including winter-killed animals and the leftovers of wolf, mountain lion, or human hunter kills. As autumn approaches, feeding builds to a frenzy known as hyperphagia, when bears can consume upwards of 20,000 calories per day and may gain hundreds of pounds in a matter of weeks in preparation for hibernation. During this time, bears are more likely to seek easy meals from human sources such as trash cans, campsites, and cars.

Behavior and Adaptations

Brown bears are generally solitary animals, keeping to overlapping home ranges rather than strongly defending exclusive territories. Apart from a mother with her cubs, they come together mainly where food is concentrated enough to draw many bears at once, such as salmon streams, berry fields, or high mountain slopes where cutworm moths shelter in the millions. A loose hierarchy takes shape at these locations, with the largest males generally claiming the best foraging spots while smaller bears wait their turn.

Senses and Communication

A brown bear’s sense of smell is sharp enough to lead it to food from miles away and is the sense on which they most depend, as its hearing and eyesight are roughly comparable to our own. Bears communicate through vocalizations, body language, and scent, marking their presence by rubbing their backs and necks against trees along well-used bear trails. Rubbing in this way deposits chemical signals about identity and readiness to breed, and those bears that mark most often tend to be the most successful at finding mates. Intelligent and curious, brown bears have excellent memories for the locations of good feedings sites and return to them faithfully each year.

Hibernation

To survive the lean months when food disappears, brown bears hibernate through the winter by denning for as long as seven months. Inside the den the bear lowers its heart rate and metabolism and subsists entirely on fat stored during hyperphagia, the intense eating period of summer and autumn. This is not the deep, near-lifeless ‘true hibernation’ of small animals like ground squirrels and bats, as bears do not experience a dramatic drop in body temperature during this time, and will rouse quickly if disturbed. Most remarkable of all, a denning bear loses very little muscle and bone density despite months of near-total inactivity, a feat that has drawn keen interest from medical researchers looking to understand how humans might retain strength if forced into inactivity.

Ecological Role

As a large omnivore, the brown bear shapes any landscape it moves through. In digging for roots, insects, or small mammals it turns and aerates the soil; in gorging on berries it carries and scatters seeds across the countryside; and along salmon rivers it provides the quiet service of hauling fish carcasses into the forest which enrich soil with nutrients carried from the sea. Studies in Alaska have found that a substantial share of the nitrogen in riparian trees originates in salmon left by bears. The growth of some spruce forests, for example, may be linked directly to the appetites of the animals that fish beneath it.

Life History

Brown bears begin looking for mates in the spring and early summer, and a female may not mate with more than one male during the breeding season. When a female becomes pregnant, the development of the embryo does not start for several months, a process called “delayed implantation.” This process occurs in all bears. If the female can’t gain enough weight over the summer and fall to produce a healthy cub, her body will end the pregnancy and reabsorb the embryo. This allows her to spare her energy and gain a head start for trying again next year. Only when a well-fed female enters her winter den does the embryo implant and true gestation begins.

The rhythm of denning follows a predictable order. Pregnant females are the first to enter winter dens, followed by mothers with cubs, while solitary males are the last to retire. In spring the sequence reverses: lone males and females emerge first, mothers with older cubs a little later, and then finally females with newborns.

In January or February, pregnant females give birth to a litter of one to four cubs, but usually two. The female rouses from hibernation during birth to clean and nurse her cubs, which are born blind and helpless, and only weigh about a pound. They will nurse in the warmth and safety of the den until spring, when the mother finally leads them out into a world of melting snow and returning food. She cares for her young for roughly two and a half years, feeding and fiercely protecting them, and in lean county cubs may stay with her for even longer. Separation usually comes when the female re-enters breeding condition and again attracts males, who’s presence can pose a danger to cubs. Males may sometimes kill a female’s trailing cubs to force her back into breeding readiness. Brown bears reach breeding age at around five years and may live up to thirty in the wild, though most perish well before then.

Conservation History

The brown bear’s retreat from the American West as among the most deliberate declines in the nation’s wildlife history. As settlement spread, the grizzly was pushed out of its range not only by habitat destruction but by sustained anti-predator campaigns, conflicts with livestock, unregulated hunting, and general persecution rooted in fear. Grizzlies that had once numbered in the tens of thousands across western states were reduced to a small fraction of their former population, eliminating roughly 98% of their range south of Canada. In the lower forty-eight states, brown bears are now confined to a few rugged strongholds in and around the Northern Rockies.

Protections came as the species neared its low point, when only about 800 grizzly bears were left south of Canada. The grizzly bear of the lower forty-eight was listed as threatened under the Endangered Species Act in 1975, and recovery has since been coordinated across a network of designated ecosystems in the Norther Rockies, Greater Yellowstone region, and North Cascades. In the decades that followed, the bears of Greater Yellowstone and the Northern Continental Divide rebuilt their numbers substantially and the animal’s legal status became the subject of repeated proposals, court decisions, and revisions depending on the specific populations in question.

For more information on the status of brown bears, please visit NatureServe Explorer.

Cultural Significance

Few animals loom as large in the human imagination as the brown bear, a creature that has stood for wilderness and raw strength across the Northern Hemisphere for as long as people have shared the land with it. In the United States that symbolism runs especially deep in California, where the grizzly endures as the official state animal, even though the last wild California grizzly vanished a century ago, in the 1920s.

In recent years the brown bears of Alaska have found an unlikely new kind of fame through an event called “Fat Bear Week,” an annual online contest run by Katmai National Park and Preserve. Each fall, as the bears of the Brooks River gorge on salmon to prepare for winter, the park invites the public to vote in a March Madness-style bracket for the bear that has most impressively bulked up for the winter. What began in 2014 as a single “Fat Bear Tuesday” has grown into a phenomenon drawing more than a million votes from around the world and has spurred public, humorous wonder for the process of hyperphagia, salmon ecosystems, and the survival of bears. For all the fearsome reputation that folklore has given the brown bear, serious encounters with people are in fact rare, and a bear’s usual response to a human is to keep its distance.

Fun Facts About Brown Bears

1. Brown bears can run as fast as 35 miles per hour in short sprints, and are strong swimmers, too.
2. Brown bear cubs can climb trees to escape danger, but unlike black bears they lose this ability as their front claws grow long.
3. During an autumn feeding frenzy called hyperphagia, a brown bear can gain as much as 400 pounds within a few months.
4. A grizzly bear in in the Yellowstone region may eat more than 40,000 army cutworm moths in a single day.

How to Help Brown Bears

• If you live in bear country, keep garbage and compost in bear-resistant containers or indoors so they aren't drawn into neighborhoods by an easy meal.
• If a bear has been seen around your neighborhood, remove bird feeders, squirrel feeders, etc. for a couple of weeks to avoid conditioning the animal to expect food where you live.
• While in bear country, keep ‘smellables’ out of areas you don’t want bears to get into, such as your tent or car, and place them in smell-proof bags or bear-resistant cannisters. This applies to anything scented, including deodorant, toothpaste, lip balm, candles, and empty drink bottles or food wrappers.
• Participate in or host a Bear Aware event. These events teach communities how to prevent conflicts, what to do in an encounter, and how to keep both people and bears safe.

Resources and More Information

Return of the Grizzly, National Wildlife magazine, 2025

Bringing Back the Grizzly Bear to the North Cascades, National Wildlife Federation, 2019

Two Decades, 1.6 Million Acres: West Fork Grazing Permit Agreement, National Wildlife Federation, 2022

ESA 50th Anniversary Video: Grizzly Bear, National Wildlife Federation, 2025

For Kids:

Bear Paw Cookies, Ranger Rick Magazine

How to Draw a Bear, Ranger Rick Magazine

Quiz: Bear Necessities, Ranger Rick Kahoot!

Grizzlies Gone Fishing, Ranger Rick YouTube

Select Sources

French, French & Knight (1994), “Grizzly bear use of army cutworm moths in the Yellowstone Ecosystem,” Bears: Their Biology and Management

Friebe et al. (2014), “Factors Affecting Date of Implantation, Parturition, and Den Entry in Free-Ranging Brown Bears,” PLOS ONE

Harlow et al. (2001), “Muscle strength in overwintering bears,” Nature

Helfield & Naiman (2006), “Keystone interactions: salmon and bear in riparian forests of Alaska,” Ecosystems

Morehouse et al. (2021), “The smell of success: reproductive success related to rub behavior in brown bears,” PLOS ONE

Last updated: October 29, 2026