Grizzly Bear
The grizzly bear (Ursus arctos horribilis) is the North American brown bear of the interior, the same species as the brown bears of Europe and Asia. It lives in Alaska, western and northern Canada and a few areas of the northern Rocky Mountains and the Northwest in the lower 48 states, such as Yellowstone and Glacier National Park. It is easy to recognize by the big hump of muscle over the shoulders, a dished face, short round ears and front claws up to about 10 cm long, built for digging. Its fur goes from blond to almost black, and the pale tips of the hairs give it the grizzled look behind its name. Males usually weigh about 180 to 360 kg and females about 110 to 180 kg, and a big male standing up reaches more than 2 meters. Grizzlies are omnivores: most of their food is grass, roots, berries and nuts, along with insects, salmon, carrion and young elk or moose. They spend five to seven months of the year in a den, where females give birth to their cubs. About 55,000 live in North America, most of them in Alaska and Canada, while the roughly 2,000 in the lower 48 are protected as threatened under the Endangered Species Act.
What is a grizzly bear?
The grizzly bear is a brown bear. It belongs to Ursus arctos, the same species as the brown bears of Europe, Russia and Asia, and it is usually treated as the North American subspecies Ursus arctos horribilis. The scientific name was given in 1815 by the naturalist George Ord, after the bears met by the Lewis and Clark expedition, and horribilis means terrible or frightful in Latin. The common name comes from the fur: many grizzlies have brown hair with pale, silvery tips that make them look grizzled, or streaked with gray. In North America the two names are used in a practical way. Bears of the coasts of Alaska and British Columbia, which eat a lot of salmon and grow very large, are usually called brown bears, while those of the interior, from the Alaska tundra to the Rocky Mountains, are called grizzlies. The bears of the Kodiak archipelago in Alaska are a separate subspecies, the Kodiak bear, and are the biggest of all. Grizzlies are often confused with American black bears, which share much of their range. A grizzly has a shoulder hump, a dished face, short round ears and long, straight front claws, while a black bear has no hump, a straight face, taller ears and short curved claws. Color is not a good clue, since both species can be brown or black.
How much does a grizzly bear weigh?
A grizzly's weight depends on its sex, where it lives and the time of year. Adult males usually weigh about 180 to 360 kg (400 to 800 pounds), and adult females about 110 to 180 kg (250 to 400 pounds), so a large male can be twice as heavy as a female. Inland grizzlies, such as those of Yellowstone and the Rocky Mountains, are on the lighter side: in Yellowstone a male of about 200 kg is already a big bear. Brown bears of the Alaska coast, which feast on salmon, are much heavier, and big coastal males can pass 450 kg, while the largest Kodiak bears have been weighed at over 600 kg. Weight also changes a lot during the year. Grizzlies gain fat very fast in late summer and autumn, a period called hyperphagia, when they may eat for up to 20 hours a day and put on more than 1 kg a day. In the den they live on that fat and can lose up to a third of their body weight by spring. Newborn cubs weigh only about half a kilogram, one of the smallest newborns compared with the mother's size of any mammal, and by their first autumn they may weigh 25 to 45 kg.
How big and tall is a grizzly bear?
On all fours, an adult grizzly stands about 90 to 110 cm tall at the shoulder, roughly the height of a kitchen counter. Standing on its hind legs, which it does to smell the air and see farther, a large male reaches about 2 to 2.5 meters, taller than most doorways. From nose to tail, adults measure about 1.8 to 2.4 meters, and the tail is only a few centimeters long. The most distinctive feature is the hump on the shoulders. It is not fat but a mass of muscle that powers the front legs for digging, so the bear can tear up the ground for roots and ground squirrels or dig out its winter den. The front claws are long and only slightly curved, reaching about 5 to 10 cm, and are often pale, so they show clearly on the paw. The face is broad and has a dished, slightly concave profile between the eyes and the nose, and the ears are short and round. The coat is thick and long, especially in autumn, and its color goes from pale blond or cinnamon to dark brown and almost black. Many bears have darker legs and lighter fur on the back and shoulders, with the pale tips that give the grizzly its name.
Where do grizzly bears live?
Grizzly bears live in two countries: Canada and the United States. Alaska holds the largest share, with about 30,000 brown bears and grizzlies, found almost everywhere from the coastal rainforest to the Arctic tundra of the Brooks Range. In Canada they live across British Columbia, western Alberta, Yukon, the Northwest Territories and western Nunavut, with about 26,000 to 29,000 bears, most of them in British Columbia and Yukon. In the lower 48 states only about 2,000 remain, in a few separate areas of Montana, Wyoming, Idaho and Washington. The biggest groups are in the Northern Continental Divide, around Glacier National Park, and in the Greater Yellowstone Ecosystem, with smaller ones in the Cabinet and Yaak and the Selkirk Mountains. Grizzlies once lived across much of western North America, from Alaska to central Mexico and east onto the Great Plains. Hunting, trapping and poisoning wiped them out from most of that range in the 1800s and early 1900s. The California grizzly, which is still on the state flag, was gone by the 1920s, and the Mexican grizzly disappeared in the 1960s. Today grizzlies use forests, alpine meadows, river valleys, prairies at the foot of the mountains and open tundra, as long as they have enough space and food.
What do grizzly bears eat?
Grizzly bears are omnivores, and although they are powerful predators, most of what they eat comes from plants. In spring, after leaving the den, they eat fresh grasses and sedges, dig up roots and bulbs, and look for animals that died in winter, such as elk and bison in Yellowstone. In late spring some hunt newborn elk and moose calves, and they also dig out ground squirrels and steal kills from wolves and cougars. Summer brings insects and fruit. In Yellowstone and Glacier, some grizzlies climb to high rocky slopes to eat army cutworm moths that gather there, and a single bear can eat up to 40,000 moths in a day. Ants, beetles and their larvae are also on the menu, and berries such as huckleberries and buffaloberries become a main food in late summer. In autumn, grizzlies near the coast and big rivers feed on salmon, catching them at waterfalls and in shallow streams, while inland bears in some areas eat the seeds of whitebark pine, a tree that is now in decline. Before winter they enter hyperphagia and may eat for up to 20 hours a day. Grizzlies also take garbage, livestock, pet food and crops when they can, which often ends badly for them.
Do grizzly bears hibernate?
Yes. Grizzlies spend the winter in a den, usually from October or November to March or April, about five to seven months depending on the place, the sex of the bear and the weather. Pregnant females go in first and come out last. Most grizzlies dig their own den on a steep slope, often under the roots of a tree or a large rock, at high elevation where deep snow seals the entrance and keeps them warm. Some use natural caves. In the den they do not eat, drink, urinate or defecate for months. Their heart rate drops from about 40 to 50 beats a minute to as few as 8 to 19, and their breathing slows, but their body temperature falls only a few degrees, so they can wake up quickly if disturbed. Scientists debate whether to call this true hibernation, but bears are among the best known hibernating mammals. They live entirely on their fat and recycle waste products into protein, so they keep most of their muscle and bone. The rest of the year, adult grizzlies live alone, except for mothers with cubs and pairs during the mating season. They do not defend territories, and many bears can share the same area, especially where food is plentiful, such as a salmon river.
How fast and strong is a grizzly bear?
Grizzlies look heavy and slow, but they are surprisingly fast. The National Park Service says they can run at 35 to 40 miles per hour, about 56 to 64 km/h, over short distances, uphill or downhill. That is much faster than the best human sprinters, which is why running away from a grizzly never works and can trigger a chase. They are also good swimmers and cross wide rivers easily. Their strength comes from the shoulder hump and the thick muscles of the front legs. With them a grizzly can dig a den in a few days, roll over large rocks to find insects, tear apart logs and dig ground squirrels out of their burrows. It can kill an elk or a moose calf with a blow and drag a carcass much heavier than itself before burying it to eat later. Adult grizzlies are usually not good climbers, because their long, straight claws are made for digging, not for gripping bark, but young bears can climb, and adults can get up trees with low branches. Their sense of smell is one of the best of any animal, many times better than a dog's, and lets them find carcasses and food from kilometers away. Their hearing and eyesight are also good.
Grizzly bear cubs and lifespan
Grizzlies mate in late spring and early summer, from about May to July. The fertilized egg floats in the uterus without developing until autumn, and it only implants if the female has gained enough fat. Cubs are born in the den in January or February, usually two, sometimes one to four. They are blind, almost hairless and weigh only about half a kilogram, and they spend the first months nursing on their mother's very rich milk while she sleeps. When the family leaves the den in spring, the cubs follow their mother everywhere for two to three years, learning where to find each food in each season, how to dig and how to fish. Cubs face many dangers: adult males sometimes kill cubs, and wolves and cougars take some, so in many areas only about half survive their first year. A female has her first litter at about five or six years old and then only every three years or so, which makes grizzlies one of the slowest breeding mammals in North America. That is why the loss of adult females hits populations hard. In the wild, grizzlies usually live about 20 to 25 years. The oldest known in the Yellowstone area, Grizzly 168, was 34 years old.
Are grizzly bears dangerous?
Grizzly bears can be dangerous, but attacks are rare, and most bears avoid people when they notice them in time. In Yellowstone, the National Park Service puts the chance of being injured by a bear at about 1 in 2.7 million visits. Most attacks are defensive. They happen when a hiker surprises a bear at close range, especially a mother with cubs, or comes near a carcass the bear is guarding. In those cases the bear may charge, often stopping short in a bluff charge, or knock the person down. Much rarer are attacks by bears that treat people as prey or that have learned to link people with food. Bears that get used to garbage, campsites or livestock often end up being killed, so wildlife managers say that a fed bear is a dead bear. The best protection is to avoid surprising a bear: hike in groups, make noise, watch for fresh signs such as dug up ground or carcasses, and keep food and garbage locked away. Bear spray, a strong pepper spray, has proven very effective at stopping charges and is recommended for anyone hiking in grizzly country. Grizzlies are not usually aggressive toward people in cars or at a distance, but approaching them for photos is dangerous and illegal in national parks.
How many grizzly bears are left?
About 55,000 grizzly and brown bears live in North America: roughly 30,000 in Alaska, 26,000 to 29,000 in Canada and about 2,000 in the lower 48 states. Worldwide, the brown bear is listed as Least Concern on the IUCN Red List, in an assessment made on 2 February 2016 and published in 2017, with about 110,000 mature bears and a stable population. In the lower 48, grizzlies fell from perhaps 50,000 before European settlement to fewer than 1,000 and were listed as threatened under the Endangered Species Act in 1975. Since then the Greater Yellowstone population has grown from about 136 bears to more than 1,000, and the Northern Continental Divide population around Glacier National Park is now the largest in the lower 48. Their future is still debated. The states want to manage and hunt them, while conservation groups say they need protection, and 2025 was the deadliest year since 1975 in Greater Yellowstone, with at least 72 grizzlies killed, mostly by people. In July 2026 the federal government proposed giving more management authority to the states without removing the listing. In Canada, the western grizzly is listed as Special Concern, Alberta lists it as threatened, and British Columbia ended all grizzly hunting in 2017.
