Nature’s Bug Zappers

At twilight the other day, I was pleased to see a Big Brown Bat flying high among the trees in my yard. I knew that my high-flying friend was doing its bit to keep mosquitoes under control. That’s a good thing, because mosquitoes are vectors for illnesses like encephalitis and West Nile virus—diseases with serious consequences for humans and that will likely become more prevalent as high heat days, urban heat islands, and other consequences of climate change intensify.

A healthy, hibernating Big Brown Bat (Eptesicus fuscus). Photo by Ann Froschauer, USFWS.

Insect elimination devices are not a good substitute for nature’s bug zappers. These devices kill not only mosquitoes, but many beneficial insects. One study of homeowners’ backyards showed that although thousands of insects were killed in a 24-hour period by just one of these devices, only 0.13% were female mosquitoes, which are the ones that seek a blood meal and bite. An estimated 71 to 350 billion beneficial insects are killed annually in the United States by these electrocuting devices. This is likely contributing to the decline of songbirds. 

Not everyone is a fan of bats. Rabies is a concern for some. But research shows that less than 1% of bats carry rabies—so you are more likely to die from a dog attack, bee sting, or lightning strike than from bat-transmitted rabies. Most of us no longer believe the old misconceptions such as bats flying into people’s hair, but somehow the fascinating facts about bats are less well known.

The bat is the only mammal adapted for active flight, with true wings that can fly. A bat can live more than 30 years. Bats can reach speeds of up to 60 miles (97 kilometers) an hour. They use sound to navigate (echolocation) and “see” in the dark. Some species play a key role in pollinating crops. And their ability to control insect populations in our neighborhoods can’t be beat. A single bat can catch 1,200 mosquitoes in an hour. The Mexican Free-tailed Bats (Tadarida brasiliensis) of Austin, Texas, are that city’s most popular visitor attraction.

Wildlife biologists use bio-acoustic equipment to capture high frequency sounds bats emit during echolocation. CT DEEP biologists recently discovered a long lost species, the Eastern Small-footed Bat during bio-acoustic surveys. Click the photo to hear the sounds of a Big Brown Bat. Photo and audio by Wikipedia.

The Big Brown Bat (Eptesicus fuscus), the one I observed in my yard, is one of nine species of bat found in Connecticut. These are the Little Brown Bat (Myotis lucifugus), Eastern Long-eared Bat (Myotis septentrionalis), Eastern Pipistrelle (Pipistrellus subflavus), Silver-haired Bat (Lasionycteris noctivagans), Hoary Bat (Lasiurus cinereus), Red Bat (Lasiurus borealis), Indiana Bat (Myotis sodalis), and the Eastern Small-footed Bat (Myotis leibeii). All are mostly insectivorous, with the exception of the Hoary Bat, which sometimes eats other bats, particularly Eastern Pipistrelles.

The Eastern Small-footed Bat was thought to be extirpated (eliminated) from Connecticut. It hadn’t been seen here since the 1940s, until one was found injured and was rehabilitated in eastern Connecticut in 2016. It had been identified in the area the year before through bio-acoustic surveys, in which wildlife biologists use special equipment to listen to the high-pitched calls bats use to find prey through echolocation.

The Little Brown Bat was Connecticut’s most common species until 2006, when a fungus called Pseudogymnoascus destructans was introduced from Europe, probably on the shoes of visitors to a commercial cave in upstate New York. It spread quickly. This fungus causes White-Nose Syndrome, named for the white fuzz often seen around the muzzles of dead or dying bats. It is a disease that invades and eats away the skin of hibernating bats, including their wings. Because it causes bats to wake up frequently during the winter, they use up their limited fat reserves very rapidly. Bats have been known to fly out of caves in the middle of winter to find food. Some bats survive winter only to die in the spring, when their immune systems kick into overdrive, attacking both the fungal invader and their own tissues. Over 90% of the Connecticut Little Brown Bat population has been wiped out. It is now a state-listed endangered species.

Hibernating Little Brown Bats suffering from White Nose Syndrome. The fungus Pseudogymnoascus destructans gives the disease White Nose Syndrome its name. Photo by New Hampshire Fish and Game.

White-Nose Syndrome has spread across the United States (see the progression map here). There is no known cure yet. Research being done with a naturally occurring bacteria that limits the growth of the fungus needs more testing.

You can help bats where you live.

Build a bat box (a summer place for them to have babies) for your yard or the side of your house to attract these natural bug zappers. Bats are more likely to use these boxes if they are placed on the south side of your house about 20 feet (6 meters) above the ground or on a pole at least 15 feet (about 4.5 meters) high. A location near wetlands, a pond, or lake is even better.

You can help bat populations by erecting a bat house on a pole or the south side of your house. Photo by Mark Buckawicki.

—Report sightings of live and dead bats seen in late December through mid-March to the Connecticut Department of Energy and Environmental Protection Wildlife Division at Also let DEEP know about summer bat colonies that you see. There might be a maternity colony nearby. Report summer colonies to the same address.

—If you have a problem with bats in your attic or other enclosed area, take the humane approach to reclaiming your space. Never pick up a bat that is lying on the ground.

—Tell others about the beautiful side of bats. The more people learn to appreciate this maligned creature, the better for bats—and people. Find more fascinating facts about them from Bat Conservation International.

It’s time to think about all that bats do to help us and how we can help them.

Published by Jim Sirch

Jim Sirch is the author of Beyond Your Back Door, a weekly blog about nature in your neighborhood. He is also Education Coordinator for the Yale Peabody Museum, a UConn Master Gardener and board member of his local land trust. As a trained naturalist, he brings a deep understanding of geology, plants and wildlife and how they interact within a particular ecosystem. He holds a B.S in Forestry from West Virginia University, a B.S. from Miami University in Science Education; and an M.S. in Environmental Studies Administration from Antioch University. He is also the 2014 Sigmund Abeles Award recipient from the Connecticut Science Teachers and Supervisors Association for outstanding science teaching and professional development.

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