Bat Boxes
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What Are Bat Boxes?
Bat boxes, also called bat houses, are artificial roosting sites that bats rest in during the day. They can be made of a variety of materials, and can be mounted on poles, trees, or structures like houses and barns. You can build or buy your own, and install it on your property to help bat populations, check out the links below to learn more!
Why Are Bat Boxes Important?
Bat houses are a significant way to help bat populations in areas where natural roosting sites like dead trees have been cleared due to human activity. In NY, even bat species that hibernate in caves will use bat houses during the spring and summer.
Major Considerations for Bat Boxes:
When building a bat box, be sure to do your research first! There are several great resources in the "learn more" section below. Bats are sensitive to temperature fluctuations, sleep and raise young in bat boxes, and come into very close contact with the bat box material. Because of this, here are some important things to consider:
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What materials will make up the bat box?
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Are they non-toxic, durable, and thermally appropriate? -Metal can rust and pressure treated boards contain chemicals that are unsafe for bats, instead use a wood like pine or cedar and consider painting it to protect the wood and to help the bat house absorb and retain warmth. See the map below for paint color suggestions!
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What are the dimensions of the bat box?
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Is it a good width and height for bat use (should be taller and skinnier than a bird house)? -The experts at Bat Conservation International note that, "bat houses only 24 inches tall and wide, and 5 or 6 inches deep, can attract nursery colonies of as many as 200 to 300 bats"!
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Is the spacing of internal partitions appropriate?
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Will there be grooves inside for the bats to cling to?
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*Read more on the specifics of bat box construction in the "Learn More" section below!
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Is the ecology right for bats?
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Are there food and water sources nearby?
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What bats are native to your area?
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Will noise or light pollution bother the bats?
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*More on this below!​​
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Little Brown Bat clinging to groves of bat house. Image credit: pbskids.org
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What will be the location of the bat box?
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Does the mount site get the right amount of sunlight? - Heat is one of the largest factors that will determine the success of a bat box! Most bats need temperatures of at least 85°F to retain body heat and keep pups (baby bats) warm; morning sun is best (Rutger, 2017). In NY, typically the issue is that boxes aren't hot enough for long enough to keep bat pups warm as they grow; usually at least 6 hours of direct sunlight is appropriate.
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Could the location lead to predation? -Animals like snakes, raccoons, and cats will hunt bats and bat pups. Make sure your bat box is not a snack bar! Consider avoiding trees if possible (they're easy for predators to climb), and make sure the entrance to the bat box is at LEAST 10 feet off the ground, but higher is generally better. Aim for 12-20ft or more above the ground if possible (Chambers & Mering, 2014 ; Rutgers, 2017).
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Can the bats fly in and out easily? -Clear of branches and debris at least 12-16inches below entry point.
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How will you mount the bat box? -Poles, trees, and man made structures (like the sides of barns/houses/garages) are all bat box mounting options. Be careful to consider predator issues with trees, and note that smooth surfaces (like poles or some house siding) can make it tough for pups and mothers to climb up into the boxes, so be sure there is a rough landing surface 3-6 inches below the entry point (BCM, 2017). Poles should also be positioned in close proximity to a tree line (10-15ft) to provide shelter from strong, chilling wind (Rutgers, 2017).
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Is the bat box close to a water source? -Bats drink water too! Typically, a slow moving or still water source will need to be within about 1/4 mile of the bat box to support a healthy, hydrated colony (Rutgers, 2017).
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Are sound and light pollution a concern? -Bats rely on echolocation to hunt, so extremely loud areas are not great options for bat boxes. Intense artificial light nearby or shining on a bat box can also disturb bats (though things light street lamps in the neighborhood can actually provide great hunting opportunities, so don't worry too much). Try to find an area that is relatively dark and quiet if possible.
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A tree mounted bat box in a NY nature preserve.
Image credit: Wendy Bosco
This map was generated by the bat experts of Bat Conservation and Management to help anyone installing a bat box decide what color to paint it.
As noted by John Chenger
of Bat Conservation and Management,
"[For] the majority of the country medium brown should work, or black. It's actually easier to fix a bat house that is too hot, but bats will never use a bat house that is too cold, so always err on the side of overheating" (2019).
Which Bats Use Bat Boxes, and Why?
According to Kathleen Kerwin (2017) of the Wildlife Conservation and Management Program at Rutgers University, “The two species that most commonly use bat houses in the northeast United States are big brown bats (Eptesicus fuscus) and little brown bats (Myotis lucifugus). During the spring and summer months, females roost together in ‘maternity colonies’ to raise pups. Males may use bat houses to roost individually or in small groups”.
A Big Brown Bat nursing her new pup.
Image credit: Bat Specialists of Michigan
A Little Brown Bat on a tree trunk.
Image credit: Dawn Vezina
Learn more:
In addition to a plethora of information on bats, this site contains tried and tested build instructions.
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Another great resource for information on bats. This section of their site explores types of bat houses, including many available for purchase.
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This website contains easy-to-follow tips accompanied by helpful diagrams and references.
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Merlin Tuttle on Bat Boxes
One of the world's foremost experts on bats and bat houses explains some of his preferences.
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Learn with a local: Explore a novice's bat box journey
Coming soon! Wendy Bosco shares her experience in building and installing a bat box at home!