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The Amazing Bat

by Liz Magnanti

With recent mosquito-borne illnesses making headlines, I have been getting a lot of questions about ways of controlling pests naturally without using harsh chemicals or pesticides. Attracting wildlife to your yard can help with insect issues. While birds will eat a lot of insects during the day, another winged creature, bats, will take care of insect issues at night. Because bats are out at the same time mosquitoes are, they can make a huge difference in controlling this pest. Just one bat alone can eat anywhere from 2,000 to 6,000 insects each night. This is the equivalent of 20-50% of their own body weight! Certain species of bats can be attracted to your yard by providing a bat house. This provides space for bats to roost, and females to raise their young safely.

In New York we have 9 species of bats who call our state home. They are all insectivores, relying exclusively on insects for their diet. Three of these bats are classified as tree bats, who spend their days hanging from trees, camouflaged by their wings and tail membranes which they can wrap around themselves for warmth and protection. Tree bats tend to be solitary, and do not form large communal groups. They can be common, we just don’t see them due to their great camouflage. Many look like dead leaves hanging from trees during the day. The other six species of bats we have are cave bats, those who spend the winter in caves where they hibernate. Some of these cave bats, such as the Little Brown Bat (Myotis lucifugus), Big Brown Bat (Eptesicus fuscus), and Tri-colored Bat (Perimyotis subflavus) are known for roosting in bat houses.

Bat houses come in many sizes and styles. In general, the more chambers the bat house has the better. The larger houses are able to provide more temperature fluctuation, which is best to accommodate a large nursery colony. Bats require a warm area to roost in. In our climate the bat house should be painted black or a dark color in order to absorb heat from the light. An outdoor, water-based, non-toxic latex paint is safe to use on the house. Bat houses can be mounted on poles or on the side of buildings and ideally by a water source. Houses can be mounted on trees. However, this usually does not provide them with the light they need to warm the house, and it leaves the house vulnerable to predators who may climb the tree to raid it. Houses mounted on poles and the side of buildings often become occupied more quickly than houses mounted on trees. Make sure the house is mounted at least 15 feet high, with the area underneath it clear, as bats need to be able to drop out of the bottom of the house for flight.

A bat house can be put up any time of the year. Bats will begin using them in early spring as they return to our area from their hibernation or migration sites. At any point in the year, however, bat houses may become occupied. Especially if a colony has been removed from a house, barn, or their roost has been destroyed in another way. Once a bat house has been put up, it requires little maintenance. It should be checked every year for evidence of wasps building a hive inside.

There are many myths about bats that have vilified them. The most common myths being all bats have rabies, they are blind, and they will fly into and get tangled in your hair. These just are not true. While bats, like all mammals, are susceptible to rabies, less than 1% of their population ever has it. Bats can see, almost as well as we can, but rely on their amazing sense of echolocation to navigate and find their prey at night. This also makes it possible for them to avoid running into structures, or getting too close to humans or predators in complete darkness.

Little Brown Bat confirmed with white-nose syndrome. Photo courtesy Flickr: Progressive Animal Welfare Society (PAWS).

Little Brown Bat confirmed with white-nose syndrome. Photo courtesy Flickr: Progressive Animal Welfare Society (PAWS).


Recently, millions of bats have fallen victim to a disease called white-nose syndrome. White-nose syndrome causes hibernating bats to wake up more frequently during their hibernation, which burn off the fat reserves they need to survive the winter. Many end up dying as they leave their hibernation site too early in the winter in search of food. The disease is named for the white fungus that is visible on the face and wings of the affected bats. It is estimated that there has been an 80% decline in the population of bats since the introduction of this fungal disease to the Northeast. This disease, combined with habitat loss, has made it increasing difficult for bats to find a safe place to roost and raise young. Most bats only have one pup a year so these spots are critical for their survival.

Not only are bats fascinating creatures, they are amazing to watch! Set up your bat house this summer and soon you may be entertained nightly by these fuzzy, aerodynamic insect eaters.

Liz Magnanti is the manager of the Bird House on Monroe Avenue in Pittsford. She has a degree in wildlife conservation and has worked as a naturalist at various nature centers.

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