Grizzly Bears live on the western side of North America where there are mountains and wide spaces. They are mostly located north of the United States, but some can be found within the lower 48 states. The males usually travel alone, but the females with their cubs. During the summer, however, 50 or 60 grizzlies gather at the falls of rushing rivers to catch salmons. From June to October, salmons swim up rivers from the Pacific Ocean to lay their eggs. At this time bears fatten up for the winter. They go where there is food. Grizzlies may fish in one river this month, but another the next month. They also travel to meadows where they find berries. When winter comes bears hibernate. They usually wait until the first snowfall before hiding in dens. Both males and females sleep for the winter. They don't wake up unless there are floods or if the days get warm. When days start to lengthen again, their biological clock tells them to get up.
The grizzlies are brown. They have a keen nose to sniff the air to find food. There are 42 teeth. This includes sharp teeth for tearing meat, and flat molars for chewing plants. Each paw has 5 sharp claws. Grizzlies' furs have 2 sizes. Long hairs keep off insects and dirt while short hairs keep the bear warm. The brown color also camouflages them from their preys. Bears have a large hump behind the neck. This hump contains muscle to strengthen the two front legs. Underneath the skin is a 10-inch (25cm) thick layer of fat. They build up the fat during summer by feeding a lot. During hibernation they don't eat or drink but burn the fat as food. After each hibernation, they can lose up to 40% of their original weight. When they hibernated during winter, their whole body slows down and the temperature drops. The heart rate decreases from 50 beats per minute to about 8 beats/min. Their body temperature drops from 89°F (31.7°C) to just about 80°F (26.7°C). Since they are resting, grizzlies don't use up a lot of energy.
After mating the females are ready to give birth during hibernation. The cubs are born in the dens. A mother usually has 2 cubs, rarely does she have 3 or 4. At birth the babies are only 1pound (.45kg) in weight and about 1 foot (30cm) in length. The cubs are blind and deaf. Their tiny bodies are covered with fine hair. They stay in the den with their mother for 3 months, until hibernation is over. During these 3 months they fatten up with their mother's nutritious milk. At soon as hibernation is over, they go in search of food. The young bears need nursing every 2 hours. By this time they are about 7 pounds (3.15kg). The mother is very protective of the cubs. She keeps them away from any potential dangers. When the cubs are a little more than a year old, they begin to feed on some solid food such as berries, nuts, roots, grasses, and meat. The mother teaches them how to survive in the wild. They learn how to hunt, and defend themselves. The cubs are ready to be on their own by the third year. The mother's milk starts to dry up. Her body is getting ready for the next pregnancy. The youngsters are on their own now. They will probably not see their mother any more. The cubs stay together for 2 or 3 years. By the time they are 6 or 7, grizzlies are ready to establish their territories. A grizzly usually lives up to an age of 20 in the wild.
Grizzlies eat a variety of foods. They eat fish, especially salmons, young elks, deer, or caribou. Sometimes they eat carrion. They would steal it from coyotes, wolves, or other bears. Grizzlies also are plant eaters. They consume berries, roots, grass, and nuts.
In 1975, the United States officially announced that Grizzly Bears were threatened. As population and tourism grow around bear country, more of their habitat is being taken away. With the loss of habitat, they are reduced to a small space. Their sources of food are also affected. When human lives are threatened, they would kill the bears. Others kill bears for the sport and the excitement. Still others hunt them down for their precious parts. Poachers kill bears for their paws, gallbladder, fur, and skin. They ship these parts to Asia where they are used as medicine. The most important thing, however, is to preserve their natural habitat.