When fall turns to winter and the temperature dips, the food sources for the wild animals becomes very scarce. Some animals wait out the harsh conditions of winter, constantly searching for food and shelter. Other animals, like the bear, spend the winter in hibernation.
Hibernation is a dormant sleep-like state.
By going into hibernation the bears bypass winter when their food supply, nuts and berries, disappears. Animals like the bear would find it extremely difficult to find enough food during winter, and therefore go into hibernation. During hibernation the bear cuddles up in a cave or in a hollowed out tree, safe from the dangers of winter. In order to survive this long period of inactivity the bear must build up its body weight by accumulating fat. In the months before hibernation bears can gain up to forty pounds of fat per week.