Have you ever wondered how animals know when to come out of hibernation?  Well, winter is slowly coming to an end, which means a lot of animals will be preparing to emerge and become active again.

Winter in the Rocky Mountains will be done at some point soon and spring will be upon us.  Springtime is when everything seems to come back to life – trees begin growing new leaves, flowers begin to grow, and animals that have been hibernating emerge.  Many animals that go into hibernation have an internal clock that lets them know when it is time to wake up.  You may see bears, ground squirrels, marmots, and other animals becoming active again.

To Remind You – What Is Hibernation?

I just want to make sure we all remember exactly what is hibernation before I get into how animals know when it is time to come out of it.

Hibernation is a form of torpor, where animals are in a sleep-like state for a long period of time.

Animals Have An Internal Clock – A Circadian And Circannual Rhythm

Hibernating animals have a kind of internal clock that is ticking away while they hibernate.  When they first go into hibernation it is as if the clock gets set.  Then it is ticking away all winter long until it is time for that animal to wake up.

This internal clock animals have that tells them when to hibernate is similar to the internal clock that tells animals including people when to go to sleep and wake up each day.  The daily clock is called our circadian rhythms.  Scientists are still learning more about how a similar process works for hibernating animals, but they call the process circannual rhythms.  The circannual rhythm is a yearly cycle that tells the animal when to go into hibernation and come out of it an a yearly basis.

External And Internal Factors Help Set An Animals’ Circannual Rhythms

Those circannual rhythms can be set for the animals by a few external and internal factors.  One internal factor may simply be the amount of fat stores the animal has on its body. At some point the animal is almost out of fat, which means it needs to wake up and find some food to survive.

Two external factors that come into play are the temperature and the amount of day light.  Animals internal clocks may be set to emerge from hibernation as the temperature warms up and the days are long enough.  At that point the animal may know that food is available outside and its time to come out of hibernation.

Do Different Animals Come Out Of Hibernation At The Same Time

NO.  Different animals wake up at different times.  For example, a black bear in the Rocky Mountains and bats in Africa have different lengths of time that they hibernate for.

Animals have developed their own internal clock that lets them know when is the best time for them to wake up – which generally is at a time when there is lots of food available for them to eat.  When they finally wake up they are very hungry, so it is good to wake up when there is lots of good food to eat.

Here is are some animals that hibernate in the Rockies.