Science of Hibernation: Why do Animals Hibernate?

Fascinating and strange natural phenomenon is what we call Hibernation. Everyone knows about such a phenomenon but a few people know the detail of it. You must be aware of hibernation as deep sleep animals have in winter. However, there is much more about it which you are not aware of. Let’s get some answers.

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The slowing down of metabolism and entering into a coma-like state is called hibernation. It is an adaptation that supports animals in conserving energy by being inactive. The animals reduce their body temperatures for a long time and consume less energy.

Hibernation usually happens in winters when the animals can’t get enough water or food for survival. This state continues for days, weeks or even months, liable on the stored energy before hibernation. The animal gets energy from the accumulated stored fat in the body prior to hibernation.


During the hibernation process, the heart rate, metabolism and breath rate of animal decreases. Hibernating animals slow their metabolism by 5 to 10 °C on average. Meanwhile, the animal becomes immobile and goes into a coma-like state. During this, the animal’s energy needs also decrease. As mentioned above, the animal’s body gets essential nutrients by stored fats in the body.

Note: The body fat provides warmth to the hibernating animal, thus, saving him from freezing.

Some people confuse hibernation with sleep but, it’s a different situation. Sleep occurs by a change in brain wave pattern whereas hibernation is a physiological change. The brain cycle for hibernating animals resembles their wake up patterns. Even some animals need to wake up periodically in their hibernating state.

In case you were wondering then yes, animals do not produce waste during hibernation. The reason is that nothing passes by their digestive tract. Bears do an interesting thing as to break down their waste products into useable amino acids and take nutrients from it during hibernation.


Animals have advanced to become very skillful at detecting seasonal changes. As the summer ends, they sense fall approaching, they start preparing for hibernation. For a successful hibernation, they need to gorge themselves on ample food. An extra layer of fat is built around the body by eating too much. This fat will be consumed during the hibernation process. This extra fat is also helpful to give them warmth while they are immobile.  

Eating is not the only thing animals manage before hibernation, but they also need a protective shelter. They are totally vulnerable during hibernation, so in order to survive, they need a shelter.

  • Some animals form dens called Hibernaculum. These dens are hidden, enclosed, insulated and often contains food.
  • Some move into secluded places.
  • Some take other animal’s dens. Of course, when it comes to survival, everything is fair.

Which Animals Usually Hibernate?

Hibernation process is common in only warm-blooded animals as the cold-blooded can’t regulate their body temperatures in winters. They select warm, safe and hidden places to hibernate and avoid predators. Below is a short list of hibernating animals.

  • Groundhogs
  • Hamster
  • Bears
  • Badgers
  • Hedgehogs
  • Ground squirrels
  • Woodchucks
  • Fat-tailed lemurs
  • Dormouse
  • Ladybird
  • Prairie dogs

Not every warm-blooded animal go through hibernation. They will stay active throughout the year. Examples of such animals are:

  • Opossums
  • Raccoons
  • Coyotes
  • Moles

Some animals enter into a torpor state but they will not go for full hibernation. They will sleep for days or weeks but then resume normal daily activities to regain their energies. Their names are:

  • Hummingbirds
  • Bats
  • Skunks

Note: Similar to hibernation, cold-blooded animals go through Estivation, where they sleep in hot dry weather. 


The interesting fact is that hibernation is different among species.

  • Black bear usually sleeps in the entire winter approximately seven months. They sleep continuously without waking up in between. 
  • On the other side, squirrels wake up every 5 days for food and excrete. 
  • Hibernation for domestic animals is very different from their wild counterparts. There is no food shortage for them, so their hibernation periods are not long and inactive. They will still hibernate as per their natural instinct.

Right now, those animals who are hiding away are eating like there is no tomorrow. In no time, they will start looking for warm and nice dens where they can stay for the whole winter. Make sure that any of these dens are not in your home.

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