Scientists have recorded grizzly bears in the Greater Yellowstone area eating more than 260 kinds of food. A grizzly eats both plants and animals.

In spring, grizzlies eat new green grasses and other young plants. They eat berries. They eat grasses, roots and bulbs.

A grizzly eats insects, including ants. In summer, some grizzlies climb to high mountain slopes where moths gather, and eat them.

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

A grizzly's longest front claws can grow to about 8 to 10 centimeters (3 to 4 inches). A grizzly uses its front claws to dig.

A grizzly's hearing is about like ours. Its sense of smell is the one it depends on most. It is very good, and it can lead the bear 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. In the fall, a grizzly bear may gain as much as 3.64 pounds (1.65 kilograms) in a single day.

Grizzlies in the lower 48 states go into their dens in the fall. Pregnant females go in first, then mothers with cubs, and lone males are the last. Grizzlies usually dig their dens on steep slopes where deep snow piles up. In warm places, bears spend less time in dens than bears where winters are long, and some may not den at all.

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. It lives on the fat it stored up during the fall. It does not eat or drink all winter. It can wake up quickly if something disturbs it.

Adult male grizzlies have much larger home ranges than adult females. Grizzly bears have home ranges that overlap with other bears' ranges. They do not guard a territory.

Words to know

• carrion: dead animal food
• hyperphagia: eating a lot
• hibernation: deep winter sleep
• territory: guarded land
• marmots: furry digging animals