Installing a Bat House in Your Yard

Installing a Bat House in Your Yard

This week I begin my spring and summer volunteer work for the CT DEEP Wildlife Division to help monitor bats. This will be the fourth year I’m doing this work, and I have written about this important volunteer activity in past columns.

Twice a month, after sunset, I drive a 20-mile transect of small country roads between Windham and Putnam. CT DEEP provides me with a laptop loaded with sophisticated mapping and recording software. I only drive 17 to 20 miles per hour and along the way a large, highly sensitive microphone attached to the vehicle roof by a strong magnet records the echolocation calls of feeding bats.

Echolocation is a type of sonar bats use to navigate in the dark while searching out and feeding on flying insects. The bats create high frequency pulses of sound and listen for the returning echo to create a mental picture of their surroundings that allows them to locate and catch flying insects.

While driving the prescribed route the microphone and recording system pick up these sound waves and create a date and location sound file on the laptop. I like to keep the volume up on the equipment so we can hear the sound of the bats.

Biologists then use the recordings to classify the different bat species by their individual vocalizations, establishing which species are present in the recordings. With samples from several summer evenings, they can estimate the numbers and species of bats in each area, in essence creating a census that counts bat species by their own distinctive echolocation calls. This data is another important component to understanding what is happening to our bat population across the state, a population that has been decimated by white-nose syndrome.

Bats are beneficial animals, especially since they help control mosquitoes, and are an important part of the local ecosystem. In fact, bats are the primary predator of night-flying insects, including mosquitos known to spread the serious infectious disease Eastern Equine Encephalitis (EEE).

Through my volunteer efforts I’ve become fascinated with bats and I’ve decided to help them out by putting a bat house on my property. A little research has revealed there are ways to offer bats a home that work and others that will not.

I know we have bats at our property in Putnam because we have seen them at dusk flying in our backyard. For the past year I have been thinking about installing a bat house to provide a safe environment and roosting location for them. A bat house provides a warm and protected place for female bats to raise their young. Female bats typically only have one pup a year and their populations grow slowly.

I have been looking at online resources for bat house information, including sources for pre-made bat houses as well as plans for building one myself. An interesting source I located is Bat Conservation International, loaded with helpful information about bats, conservation efforts and, of course, bat houses.  Here is a link to their website and information about bat houses:

Here are some important bat house facts that I will consider as I look to install one in my back yard:

  • Bats prefer roosts mounted on buildings or other large wooden or concrete structures rather than on poles or trees.
  • Bat houses mounted on poles work well in moderate to hot climates that do not experience extreme temperature swings between day and night.
  • Mounting bat houses on trees should be avoided as trees tends to shade the houses and present greater risks of predation.
  • A bat house should get at least 6 hours of sun exposure (facing either east or south) and preferably have a nearby water source.
  • The bat house should be painted a black or brown to help retain heat.
  • Bats prefer to launch from their roost and gain momentum by gliding before flying. The bat house should be located 20 to 30 feet from tree branches or other obstacles and 12 to 20 feet above the ground.

With this helpful information I have decided it would be better to mount a bat box on a pole instead of attached to a building. We do have two barns on our property, however both have too much tree cover that would shade the box.

My plan is to either build or purchase a bat house and mount it on a tall pole 15 feet above the ground. I will locate it in an open area of our back yard, paint or stain it black, and place one of our birdbaths nearby for a water source.

So, what makes bats so special and why all this fuss? Here are a few facts:

  • Bats are the only mammals capable of true flight and there are more 1,300 different species worldwide.
  • In our region, we have nine different bat species and all but one (the big brown bat) are on Connecticut’s list of endangered, threatened and special concern species.
  • A single bat can eat 1,200 night-flying insects in an hour! They have a very high metabolism and can eat up to 125 percent of their body weight in insects in a single night! That’s a lot of mosquitos.
  • Despite popular belief, bats are not blind. They have good eyesight but rely on echolocation to fly at night and to locate prey flying insects.

Information about bats in Connecticut and white-nose syndrome can be found at:

Later this summer I’ll provide an update about my travels recording the echolocation calls of bats and any success I may have enticing bats to roost in a new bat hotel in my backyard.

The more we know about bats, the better our management decisions and conservation practices. Bats deserve our attention, even more so now that their numbers have declined due to white-nose syndrome. They live with us in a beautiful place called The Last Green Valley. I hope you’ll join me and so many others as we enjoy it, care for it, and pass it on.

Bill Reid is the Chief Ranger of The Last Green Valley National Heritage Corridor. He has lived in and explored the region for over 40 years and can be reached at


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