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Class: Mammalia (mammal)
Order: Carnivora (meat-eating mammals)
Family: Ursidae (bears)

Brown bears are the most widespread of all bears. They are huge animals, weighing over 135 kgs. The brown bear of North America is also known as a grizzly bear and weighs as much as 390 kg. But the largest brown bears are those found on Kodiak Island in Alaska. These can grow to over 3 m in height and weigh more than 700 kg!

Though brown bears do climb trees, they prefer being on the ground. They walk on all fours in a slow and cumbersome stroll. But despite their bulk, brown bears can be extremely quick, charging at speeds of around 50 kph. They also have great stamina and can run at top speed for miles without taking a break.
Are brown bears agressive?
If disturbed, they may either attack or simply retreat. Only when defending its cubs does a mother bear become ferocious. Brown bears rarely attack humans. When they do, it is often because of their poor eyesight which leads them to mistake a person for another bear or animal.

Long winter sleep
As winter draws near, bears eat almost continuously to stock up for a long winter sleep. Safe in a cave or hole, the bear will sleep from October until March or April.

Bringing up cubs
Brown bears mate in spring, usually every 2nd year. The female bear gives birth to 1 to 3 cubs in the winter months, about 210-255 days after mating. The female either digs out her own den or finds a natural cave or hollow tree in which to sleep and give birth. She remains there through the winter, not feeding and relying on her store of body fat.

The cubs live with their mother for up to 3 years.
Grizzly bear standing in the snow, Rocky Mountains, USA. 
Grizzly bear standing in the snow, Rocky Mountains, USA.
Conservation concern
Most brown bears are found in North America and parts of Russia, although their range has been much reduced in these areas. They are now very rare in Western Europe where they are found in small numbers in Scandinavia, Spain, and central Italy. WWF is exploring ways of increasing numbers of wild bears in Europe.

Bear facts

Grizzly bear (Ursus arctos horribilis), a key species in the Mackenzie Valley. © WWF
  • The frosted, or grizzled, coats of bears living in the American west earned these animals the name 'grizzly'.
  • Sometimes the female bear does not even wake up to give birth during her winter sleep.
  • The average weight of a bear can rise to 400kg in October as the bear stocks up before it waddles off to its den.
  • Bears are usually solitary creatures and avoid the company of other bears. However, bears can gather in large groups to take advantage of rich food sources. At McNeil River Falls in Alaska, the largest concentration of brown bears occurs annually with up to 60 bears at one time, attracted by spawning salmon.