Why do bears hibernate?

When autumn 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 of 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! 

Although, there has been quite some debate as to whether it is true that bears do actually hibernate as they have different habits to other hibernators. 

While a bear is denning, its heart rate, breathing rate, and metabolic rate do slow down, and their body temperature is reduced.

But, compared to true hibernators —  like ground squirrels —  a bear’s metabolic rate is significantly less depressed, and its body temperature is reduced only a little.

For example, a ground squirrel’s body temperature during hibernation is reduced to near freezing. Alternatively, bears reduce their body temperatures by about only 10 degrees or so.

Also, ground squirrels will have to awake every week for about a day, to enable them to eat stored food and go to the toilet. 

However, bears don't do this. Bears can go for more than 100 days without eating, drinking, or toileting!