When Do Bats Come Out of Hibernation?

Back in the fall, we wrote about what to expect for Bat Hibernation in 2022. For the past winter months, bats across the US have been in their hibernation colonies, in a state of inactivity or torpor. Now, with the arrival of Spring, temperatures are rising, flowers are blossoming, and many animals are waking up from hibernation! When do bats come out of hibernation? Some bats start to emerge from hibernation in March, and by April, most bats are becoming active again. However, they may return to a torpid state if their body temperature drops. By the middle of May, when warmer temperatures are consistent, all bats will have come out of hibernation and be fully active. So, what should we expect to see now that the bats are waking up?

What happens when bats come out of hibernation?

When bats first come out of hibernation, they are extremely hungry as they have survived on their fat stores throughout the winter. In fact, by the time they wake up from hibernation, they will usually have lost about half their body weight! So, they will focus on replenishing their supplies when they emerge from hibernation. As a result, we can expect to see many more bats around in the evenings and at night, when they will feed. But it’s not just food the bats are thinking about – female bats may start to prepare for giving birth to pups.

When is bats’ maternity season? 

Although bats mate in the fall, it’s not until the Spring that the female bats become pregnant. So, soon after bats come out of hibernation, mother bats will prepare to give birth to their pups. Female and male bats live separately during this time, and the females are often the first to leave the winter roost (hibernaculum). They then travel to their summer home or “nursery roost.” They share this roost with other female bats as a “maternity colony” until they give birth in May or June. Then, they stay in the maternity roost until their pups can leave the roost on their own. 

Bats Waking Up in the US- fact-file:

Little Brown Bats, Big Brown Bats, and Mexican Free-Tailed Bats are the most common bats in the US. So where can we expect to see them after they emerge from hibernation? 

Little Brown Bat  

When Little Brown Bats come out of hibernation, they migrate from their hibernaculum to their summer roosting site. Some colonies travel almost 300 miles! Usually, this migration starts in April in the Northern States and March in Southern states, and the colony will have usually reached its summer nursery roost location by the end of May. 

Big Brown Bat 

Big brown bats are found throughout most US states. They usually hibernate close to their home, at most only around 80km from their summer roost, so they will not travel far after hibernation. So, if you see big brown bats in the Spring, they have likely woken up from a nearby hibernaculum site.

Mexican Free-Tailed Bat

Mexican Free-Tails do not hibernate but migrate to Mexico for the winter. Then, in early Spring, around February / March, they migrate back North to states such as Texas, Kansas, and Oklahoma. So if you live in these states, you may see a colony in migratory flight! Colonies can be massive, so they won’t be hard to spot! For example, the famous colony of Mexican free-tails that live each summer in Austin, Texas, under the Congress Avenue Bridge, number around 1.5 million – so if you are local to Austin, you may have observed this huge colony returning to its roost in the Springtime.

Keep a look out for bats this Spring!

With bats becoming active again, you should be alert to signs that bats are roosting nearby or in your property. Although bats are vital for our ecosystem, due to the risks of contracting serious diseases such as rabies and histoplasmosis from bats, you should avoid contact with bats. During the Spring, you may hear the sounds of bats in your home or see bats flying to and fro your home at dusk. If so, you may have a colony of bats living in your home. They may even have been hibernating there all winter! Or they may have chosen your home as their maternity site. 

What if bats are in your house?

If you searched “when do bats come out of hibernation” because you suspect bats are roosting in your property, you should arrange a building inspection and plan to exclude the bats safely. However, caution is needed as there are many laws across the US to protect bats, and specific laws prohibit disturbing maternity colonies. Therefore, particularly at this time of year, we recommend not attempting to remove the bats yourself. Instead, contact a professional bat removal company for assistance. 

At Get Bats Out, we have local technicians across the US states who have local expertise and understanding of the laws surrounding bat removal in your state. We can advise you on the safest way to deal with a bat infestation in your property and the best time to do this in line with local legislation. Contact us today if you have any questions or concerns about bats in your property.  

Your Local Bat Removal Expert,

Michael Koski