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9 brown bats clinging to a basement ceiling
Big brown bats are one of the bat species most likely to be found in buildings. Photo: USDA, Forest Service. Click photos to see enlarged versions.

All bats in the Northeast are insect-eaters, making them environmentally and economically important. In other words, they are good to have around.

There are two types of bats in the Northeast. Some species live largely solitary lives primarily in tree canopies and cavities and, like many birds, migrate south for the winter. Bats in the second group are communal and typically overwinter in caves and mines. These species, especially little brown bats and big brown bats, are most likely to be found in buildings.

What Do Bats Look Like?

Batman got it right—you’re most likely to see bat silhouettes in the sky at dawn and dusk. Most bats that use buildings in the Northeast look surprisingly small hanging from the rafters, but actually have 9 to 12 inch wingspans.

five bats in flight against a black background
Five photos of a single bat merged into one. Photo: Stuart Anthony, flickr.

You may also notice their poop, aka guano, which piles up beneath their hang-out spots and entry holes.

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Should I Worry About Bats?

brown bat with wings spread out on tree trunk
Little brown bats can also be found in buildings. Photo: J.N. Stuart, flickr.

Bats are one of those creatures that instill fear in people. (Thanks, Hollywood.) But many of those fears are overblown. Don’t take offense if a bat swoops at you outside—it’s not going after you like some birds do if you get too close to its nest. Instead, that bat is hungrily catching flying insects, including pesky mosquitos. And don’t worry about it getting stuck in your hair. Their use of precise echolocation helps find those small insects and prevents collisions with larger objects like you.

If you find a bat in your room, it’s probably as shocked as you are. Sometimes the young get lost when learning to fly in late summer. If a bat gets trapped indoors or you find it on the ground, call a professional wildlife control operator. Always be cautious about the potential for rabies, especially if there is a possibility of direct contact with a person or pet. According to Paul Curtis, Cornell Extension Wildlife Specialist, "If a person wakes up in a room with a free-flying bat, and it’s unclear if there was actually an exposure, then the bat is usually tested for rabies.  This is especially true if the person was a child, under the influence, or compromised in some way. All bat-related incidents should be reported to the local health department."

a pile of bat poop lying on a discarded carpet piece in an attic
Bat guano in an attic is usually found in piles.  Photo: NYSIPM.

Also of concern, bat guano can grow mold. One, histoplasma, can cause respiratory problems due to histoplasmosis. Wear a protective mask when in places where bats have resided indoors.

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Why Do I Have Bats in My Attic?

Beginning in the spring and into the fall, both species have “maternal roosts” consisting of females and the young-of-the-year congregating in the warm upper sections of buildings. Bats can get through crevices as small as ¼” wide by 1 ½” long or holes ½” by ½”. At night they’re mainly on the wing and hunting, but now and then they relax a bit under your porch or breezeway.

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How Do I Manage Bats?

If bats are in your belfry, call a professional. They’ll work with you at the right times of the year to close up crevices and holes that let bats in. Closing up entry holes in the summer could trap baby bats inside. Sources for assistance in locating professionals include your state’s wildlife agency, the National Wildlife Control Operators Association, and in New York State, the NYS Wildlife Management Association.

Bat-proofing of a building is best done with the use of checkvalves (one-way door devices), either home-made or commerical.

small brown bat with white coating on nose
Little brown bat with white-nose syndrome. Photo: Al Hicks, NYDEC.

The legal status of bats varies from state to state. In New York, two species, the Indiana bat and the northern long-eared bat, are protected. However, the conservation of all bats is encouraged. This is particularly important since the populations of some bat species, especially the little brown bat, have been decimated by an introduced fungal disease, white-nose syndrome.

Due to the biocontrol benefits of bats, you may be interested in promoting bat habitat on your property.

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