How Big Do Grizzly Bears Get? Grizzly and Kodiak Bear Size

Typical grizzly bear size

Grizzlies are inland North American brown bears, and their size depends heavily on where they live. Bears of the Rocky Mountains and interior Canada eat roots, grasses, berries, insects and the occasional elk calf, and they grow more slowly than bears with salmon.

In the far north, grizzlies of the Canadian barren grounds are among the smallest brown bears, with males averaging only about 140 kg (300 lb), similar to large American black bears.

Why coastal brown bears and Kodiak bears are bigger

The biggest brown bears live where food is richest. On the Alaska Peninsula, adult males average about 390 kg (860 lb) and females about 210 kg (460 lb). On the Kodiak Archipelago, males commonly reach 480–635 kg (1,050–1,400 lb) by autumn.

The key is salmon. Spawning salmon are packed with fat and protein and arrive in huge numbers every summer, so bears can eat far more energy in less time than bears digging for roots. Mild coastal winters and long feeding seasons help too. The same pattern appears in Russia, where the coastal bears of Kamchatka are among the largest brown bears in Eurasia.

How much weight do grizzlies gain before winter?

Every brown bear changes size through the year. In spring, after months in the den without food, bears are at their thinnest. In late summer and autumn they enter hyperphagia, a period of intense feeding, and can gain more than 1 kg (2 lb) of weight a day.

Over a season, a large bear can put on up to about 180 kg (400 lb), much of it as fat. That means the same bear can weigh 30–50% more in October than in May, which is why published weights vary so much. Pregnant females need especially large fat stores, because their cubs are born and nursed in the den.

How big are grizzly cubs?

Cubs are tiny at birth: about 340–680 g (12–24 oz), blind and almost hairless. Mother bear milk is rich in fat, and cubs grow quickly. By the time they leave the den in spring they may weigh around 7–9 kg (15–20 lb), and by their first autumn often 20–45 kg (45–100 lb). Males keep growing until about 10 or 11 years of age.

Size records and how reliable they are

Records for bear size are often confusing. Weights from hunters may be estimates, captive bears are often overweight, and many old “1,000 kg” stories cannot be checked.

The best-documented giants are Kodiak and Alaska Peninsula males, which can reach roughly 680 kg (1,500 lb) in autumn. Wildlife managers and trophy organizations often compare bears by skull size rather than weight, because a skull does not change between spring and autumn. Claims of wild grizzlies over 700 kg (1,540 lb) should be treated with caution unless the animal was actually weighed on scales.

Grizzly vs polar bear and black bear size

The polar bear is usually listed as the largest land carnivore, with adult males typically weighing about 350–700 kg (770–1,540 lb). An average grizzly is clearly smaller, but the largest Kodiak bears overlap with big polar bears. See polar bear vs grizzly bear for a full comparison.

American black bears are smaller on average: adult males often weigh 60–250 kg (130–550 lb), females 40–150 kg (90–330 lb). A big black bear can still outweigh a small grizzly, so size alone is not a reliable way to tell them apart. Shape is better, as explained in grizzly bear vs black bear.

How strong is a grizzly bear?

Size goes with power. The grizzly’s shoulder hump is a mass of muscle used for digging, and bears can flip large rocks and tear open logs to reach insects and rodents. Their bite force has been measured at more than 8 megapascals (about 1,200 psi), strong enough to crack bones. That strength is one reason why people are advised to keep a respectful distance from any bear.

Despite their bulk, grizzlies are also quick. They have been timed at about 48 km/h (30 mph) over short distances, faster than any human sprinter, and big bears can still climb steep slopes and swim across wide rivers with ease.