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Bats in Your Backyard

Little Brown Bats (Myotis lucifugus) in a bat house. Photo by Phil Myers, University of Michigan Museum of Zoology.

“When I see the pile of bat guano below the bat house, I realize how many bugs have been eaten and that makes me so happy.”

About three years ago my dad noticed that we had bats in our attic. His first reaction was that he wanted them out of his house as soon as possible. However, when he thought of all the ways that he would achieve this, he realized that he was evicting these poor bats with nowhere to go. A bat’s biggest problem is the shortage of places for them to inhabit. When they return from winter hibernation or migration sites, many species of bats like to come back to their same roost. They have requirements for roosting sites that are increasingly less common on our human-dominated landscapes, leading many bats to explore and live in human dwellings.

My dad, interested in trying not to evict his bat roommates, bought a book all about bats and bat houses in order to learn about what he could do (Beginner’s Guide to Bats, Kim Williams, Rob Mies, Donald & Lillian Stokes). He read about how to build a bat house on his own, but in the end took the easier route and purchased a bat house kit online for roughly 30-40 dollars. “All I had to do was screw it together,” he said. For information on how to build a bat house from scratch, click here for instructions from Bat Conservation International. Most importantly, kit or no kit there are three very important things to put into consideration when building and putting up a bat house:

  1. Solar exposure: Bats like to be warm so it is important to have the house be exposed to maximum amount of sunlight.
  2. Obstacles: Bats like to live near an open space for when they are foraging for food
  3. Water source: bats need to live within a ¼ mile radius from a source of water for drinking.

Bat houses are best mounted on poles at 15-20 feet off the ground, but a single-chambered house should be attached to the side of a wooden or brick building to help regulate the temperature within. Make sure that it is away from any bright lights. The bat house can be installed anytime of year, however bats are more likely to move in to their maternity site when they first return from their winter hibernation in April or May.

Three years ago, before my dad put up his bat house, he didn’t know much about the common bats in Maryland. He is now knowledgeable and enthusiastic, especially about the species that we have at our house, the Little Brown Bat (Myotis lucifugus). He was quick to tell me that what he finds most interesting about Little Brown Bats is that they mate in the fall and the sperm is stored in the females’ bodies for multiple months; she doesn’t become pregnant until the spring.

Cool, Dad.

My dad is a prime example of someone who was quick to want to kick the bats out of his house, but once learning their quirks and benefits-now finds them fascinating.

The comment my dad made about bat guano was just one of the many benefits that they provide. A Little Brown Bat can eat up to 1,200 mosquitoes in one hour. Bats also eat other insects and help control insect populations because some insects can detect bats from 100 feet away and avoid those areas.

Since installing his bat house, my dad has seen a noticeable difference in the amount of mosquitoes and beetles that have bothered us and our plants in the past. More bats means less bug bites and less insecticide use around the house. The guano not only reminds my dad of all the bugs that the bats are eating, but also makes for great fertilizer because it is rich in nutrients and phosphorous and it doesn’t break down as easily as other organic matter does. My dad uses his bat guano for his rose bushes.

The bat house (1), and a healthy heap of guano below it (2). Photo by Lucy Heller.

Sometimes, if you have the right amount of light from the moon, you can see the bats flying around foraging for bugs. Practical benefits of bats aside, getting to see hundreds of bats hunting in the moonlight is my favorite part about having bats around the house.

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Lucy Heller Communications and Maryland Outreach Coordinator, Maryland & DC Office

Lucy is the Communications and Maryland Outreach Coordinator in the Annapolis office. She assists with daily communications work and coordinates Maryland outreach events.

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