Do bats hibernate? You may be asking yourself this is you haven’t seen any bats during the autumn or winter nights.
Some bat species do hibernate in the winter months. They will go into a dormant state known as extended torpor. This type of hibernation allows bats to lower their heart rate, metabolism, and body temperature. Bat hibernation lasts for 6 months (183days) to allow them to survive harsh winter conditions.
This guide will take you through everything you need to know about what bats do during the winter.
Sound good? Then let’s get started.
Bat Torpor Vs Bat hibernation
Hibernation and torpor are both states of dormancy and can be used interchangeably. Bats can do both depending on their environment.
Let’s take a look at what each dormant state is and when bats use it.
Hibernation is an extreme state of dormancy that bats use during the winter months.
By going into a state of hibernation bats will:
- Drop their heart rate to as low as 4 beats per minute
- Lower their body temperature to around 35.6°F (2°C)
- Lower their respiratory rate to 5 breaths per minute
- Stop Digesting Food
A bat’s ability to slow all these essential body functions helps them to save as much energy as possible. They know that food supplies during the winter are scarce. Plus winter conditions can be deadly.
Going into a state of hibernation helps bats to survive over the winter months. Bat hibernation will last for around 6 months of the year.
The change in temperatures and lack of insects will trigger a bat’s hibernation behaviors. Bats will usually go into hibernation mode from November through to March. This may lengthen or shorten depending on when the daily temperatures rise above 50°F (10°C).
Think of torpor as a less extreme version of hibernation. Going into torpor means bats can reduce the energy consumption from body functions, but not as severely as with hibernation.
When Bats are into torpor they will:
- Reduce their heart rate to 4-80 beats per minute
- Reduce oxygen rate by 90%
During Torpor a bat won’t drop their temperature as they do when in hibernation mode.
A bat will normally use periods of torpor at any time of the year when weather conditions are poor. If the temperature drop below 50°F (10°C) for a few days then a bat will go into a state of torpor.
That’s because there is less insect activity during poor weather conditions. The lack of a food source means less energy. The best way for bats to save energy is not to use up what they already have available to them.
Short states of torpor are an energy-saving survival strategy just like hibernation. This type of torpor last usually only 1 day with bats.
Do bats Wake during hibernation?
Bat don’t stay inactive during their 6 month hibernation period. They will occasionally wake. How often they do this will depend on the species of bat. Some bat species will wake once per week, others only once every 4-6 weeks.
That’s why bat hibernation is essentially lots of prolonged periods of torpor joined together.
When a bat wakes during hibernation it will have a short burst of foraging for insects, drink, and get rid of urine and feces. They will quickly return and go back into a state of hibernation.
These periods of waking can be dangerous for bats. It takes a lot of energy for bats to wake even short periods of 30 minutes to an hour.
If they use too much energy they may not be able to get back into a state of hibernation. They then run the risk of starvation or freezing in winter conditions. They also run the risk of disturbing other hibernating bats and causing them to wake too early.
How Do Bats Prepare For Hibernation?
Hibernation isn’t as easy as you may think for bats.
It’s quite a dangerous time for them and if they don’t prepare properly they may even die. Preparation for hibernation in the summer and autumn months is essential for the species survival.
There are four main ways that bats prepare to go into hibernation. Let’s take a look.
1. Fatten up
During the summer season bats will eat lots of insects. One of the reasons they do this is to put on as many fat stores as they can. These fats stores aren’t your usual white fat but a special brown fat for winter.
The brown fat that bats store during this time will act as an energy source for bats during hibernation. The bats won’t use much of the fat during torpor. However, the period when they wake up uses a lot of energy for bats.
Having a good fat supply means the bats can wake and re-enter into a state of hibernation.
Bats will put on around 25%-30% of their body weight in preparations for winter.
2. Find a good location
For successful hibernation, bats need to find a good location. They need a place that is quiet, cool with consistent temperature and humidity. Those last two parts are essential.
Bats will seek out dark caves, mines, quarries, bridges, disused buildings, tunnels, and attics. These locations will protect bats from erratic weather conditions and prevent them from being easily disturbed.
The location a bat hibernates in is called a hibernacula. Bats will often return to use successful hibernacula for years.
The ideal temperature of a bat hibernacula is 41°F (5°C). This allows bats to maintain a low temperature during hibernation. The right humidity is essential to make sure that bats don’t lose too much water during hibernation.
Trying to keep disruption to a minimum is also vital for their survival. Disruption cause bats to wake early and use up too much energy. A disturbed bat may not be able to return to a hibernation state. If this happens in the height of winter, they may starve or freeze to death.
3. Huddle Together
Bats will huddle together in a cluster with lots of other bats in their hibernacula.
This gathering behavior has a few advantages for bats including:
- Maintaining even temperature and humidity
- Shelter from poor weather
- Protection from predators
- Increasing reproductive success
These groups of bats are known as colonies. The number of bats in a colony can range from twenty to thousands. A typical bat colony will be in the hundreds.
Bats will sleep upside down when gathered in their colony. This is a behavior known as roosting. Bats roost so they can fit more bats together in a smaller area for more protection.
4. Grow Fur
Bats will shed and grow fur once a year. This happens around the summer and autumn months. This means that overwintering bats should have fresh fur for hibernation.
Bat fur is an essential part of the hibernation process.
Fur not only prevent bats from losing water through evaporation. It can also help with the process of waking from torpor states. When a bat wakes they need to raise their body temperature from around 35°F (2°C) to 106°F (41°C) very quickly.
Having a warm fur layer helps bats to do this without losing precious heat. The fur also prevents bats from heat loss and using up too much energy to stay warm during their short waking periods.
Do all Bats Hibernate?
Not all bat species will hibernate in the winter. Some bats will migrate to warmer climates to survive. Warm climates mean better temperatures to survive and a rich source of insects to feed on.
Some bats will migrate and hibernate. And some may not migrate or hibernate. This is more common with bats residing in a state with a warm winter climate such as Southern Texas or Florida.
|Bat Species||Hibernate||Migrate From USA||Both|
|Little Brown Bat||x|
|Lesser Nosed Bat||x|
|Big Brown Bat||x|
|Silver Haired Bat||x|
Helping Bats Survive the Winter
There are a few things that you can do to help bats in your local area survive over the winter.
1. Hang a Bat Box
Hanging a bat box in your yard is a great way to provide a safe roosting site for bats over the winter.
Mounting a bat box on the side of your house is much better than on a tree or a pole. Although bats will use boxes located in these areas, it puts them at risk of predators.
Hanging a bat box on your house will help to prevent the bats from actually roosting in your home and causing damage.
You’ll have more success attracting bats by mounting two or more bat houses in the same location. Dark-colored bat boxes are also preferred by bats.
If you’re after a quality bat house to help bats through the winter then check out this bestselling bat house.
2. Attract Insects
In the winter insects are scarce. Yet we know that they like to hunker down in ground vegetation. You can keep small piles of logs or flowers and plant vegetation in your yard.
This will provide bats with a great place to forage for insects. A good supply of insects will help insects fill up and save energy during their short waking periods.
Having lots of plants, trees, or bushes in your yard is a fantastic way to help bats in the winter.
Bats will use these as locations to orientate themselves around your yard. That’s because they use echolocation to move around. The easier they can do this, the more energy they save from flying around.
Any foliage in your yard will also be a great place for the bats to forage for insects.
4. Do Not disturb
If you find a bat roosting in the winter months, do not try to move it. A hibernating bat won’t cause any harm to you or your home.
If you do disturb the bat then it may not survive through the winter. It’s best to leave a hibernating bat until the early spring. If you need to evict them, it’s safe to do so at this point as they will have a food source to survive on.
Some species of bats will hibernate in the winter, whereas others may migrate. Bats that hibernate will do this to survive to cold winter months and lack of good food supply.
Bats need to prepare for their winter hibernation. This is because they need the energy to wake for brief periods of time. These waking periods allow bats to forage, drink and get rid of waste.
Bats will hibernate in large colonies to help them to survive, and they need to be choosy about where they hibernate. This will allow them the right conditions for the best chances of survival.
There are ways you can help bats over the winter. This is mainly providing habitat and means to a good food source. Check out my guide for more information on how to attract bats to your yard.
It’s important that hibernating bats are not disturbed in the height of winter, as this is likely to result in the bat starving or freezing to death.