A grizzly bear is a big, heavy bear. An adult stands about 3.5 feet (about 1 meter) tall at the shoulder. In the lower 48 states, adult males average 400 to 600 pounds (200 to 300 kilograms). Adult females average 250 to 350 pounds (110 to 160 kilograms).

Grizzlies eat both plants and animals. In spring, they eat new green grasses and other young plants. They eat berries. They eat grasses, roots and bulbs.

Grizzlies eat fish, such as salmon, and small animals such as ground squirrels and marmots. They eat insects, including ants. They also eat carrion, which is an animal they find already dead.

In summer, some grizzlies climb to high mountain slopes where moths gather, and eat them.

A grizzly bear's hearing is about like ours. Its sense of smell is the one it depends on most. Its nose can lead it to food from far away.

Hyperphagia is the time in fall when a grizzly eats far more than usual and turns the extra food into fat. It lasts two to four months before the bear enters its den.

Grizzlies in the lower 48 states go into their dens in the fall. A den can be a natural cave or a hole dug into a hillside. The bear spends the winter sleeping there.

A bear's winter sleep is not true hibernation, because its body temperature does not drop very far. In the den, its heart beats much more slowly and its body uses less energy. A bear lives on the fat it stored up during the fall. All winter in the den, it does not eat or drink. A bear in its den can wake up quickly if something disturbs it.

Cubs are born in the den in winter. A grizzly mother usually has about two cubs at a time, and can have as many as four. In the den, the cubs nurse and keep warm against their mother until spring. Cubs stay with their mother for about two to three years.

Words to know

• hyperphagia: eating a lot
• carrion: dead animal food
• hibernation: deep winter sleep
• marmots: furry digging animals
• bulbs: plant parts

The short version

A grizzly bear eats both plants and animals, from berries and roots to fish and ground squirrels. In the fall, it eats far more than usual and turns the extra food into fat. Then it spends the winter sleeping in a den, living on that fat. It does not eat or drink all winter.

Quick facts

• Grizzly bears eat both plants and animals.
• Hyperphagia is the time in fall when a grizzly eats far more than usual and turns the extra food into fat.
• A grizzly bear spends the winter sleeping in a den.
• A bear in its den lives on the fat it stored up during the fall.
• All winter in the den, a grizzly bear does not eat or drink.