Bats are the most diverse group of mammals, with 1,400 different species, and are very important ecologically and economically.

“We naturally fear most what we understand least,” explains Merlin Tuttle, “and bats are among the least understood animals.”

I had asked this veteran bat conservationist why bats meet with such hostility from the general public. I was hoping to expand my own knowledge and promote a partnership with bats among gardeners. Just being nocturnal, adds Tuttle, makes bats seem mysterious and threatening.

Besides that, there is the accusation that bats are the source of the COVID-19 virus. Supposedly, the virus circulated in bats before jumping to humans. When I ask Dr. Tuttle about that, he says the disease “may be connected to bats, and distantly at that. Most of what we hear about COVID and other major diseases attributed to bats is pure speculation, sensationalized in dramatic headlines. COVID has been speculated to come from snakes, from pangolins, from mice, from all kinds of things.

We still don’t know where COVID came from. We may never know where the first human case came from or how long it’s been in humans. One theory is that it’s been in humans for quite some time and evolved into a dangerous virus while in humans.”

Horseshoe bats in South Asia have a related virus, concedes Tuttle, one that shares 96 percent of its DNA with COVID-19. But humans, Tuttle points out, share 98 percent of their DNA with chimpanzees, “and I don’t think anyone has trouble telling a human from a chimpanzee.”

Consider the wonders of bats, Tuttle asks. Instead of fixating on vampire bats, which constitute less than 1 percent of bat species worldwide, consider that there are bats with 6-foot wingspans and bats so small they weigh less than a U.S. penny.

Most bats have sophisticated social systems, strikingly similar to those of higher primates. They are the most diverse group of mammals, with 1,400 different species, and are very important ecologically and economically. Bats are the key to insect control for a variety of crops and play an important role in pollinating flowers of other economically important plants in Central America and tropical Asia.

Closer to home, in Tuttle’s home state of Texas, he says, the Texas Department of Parks and Wildlife estimates that bats are worth $1.4 billion annually in insect pest control. Nationwide, the value of the bats’ service in eliminating agricultural pests is estimated at $23 billion a year.

Yet bats are under threat throughout much of the United States as well. An introduced fungal disease, known as white-nose syndrome (WNS), has attacked and killed millions of bats, although at its point of introduction, the northeastern states, small populations of resistant bats have survived and appear to be rebuilding.

“So, it’s not a time when we can say, well, they’re going to take care of themselves. It’s a time when they need special help from us,” Tuttle said.

Reducing pesticide use is one way to help bats. Pesticide ingestion, if it doesn’t kill the bats outright, can raise their metabolism so that they can’t hibernate as efficiently. A particular threat is the mosquito-spraying programs enforced in many communities. Mosquitoes breed so prolifically that the sprays depress their populations only fleetingly. But populations of mosquito predators, such as bats or mosquito-eating fish, who are also killed by the sprays, are less prolific and slower to recover. This means that the spray programs are often ineffective — leading to actual increases of mosquito populations over time — as well as addictive; the death of the mosquito predators means that if the spray programs are interrupted the mosquito population explodes.

Another thing gardeners can do to foster the population of bats is to erect two or more bat houses. On the Merlin Tuttle’s Bat Conservation website (, there is a guide to approved bat houses. The plural numbers are important because bats favor areas where they can shift from one roost to another if conditions change. They may favor a bat house located in full sun during chilly weather and move to another in the shade during hot weather.

Attracting a colony in the hundreds is not uncommon, and Tuttle has known of individuals who have installed larger, more elaborate bat houses that have attracted up to 40,000 of the beneficial flying mammals. Watching the bats emerge from their house at dusk becomes, he says, a favorite summertime activity, and the gardener benefits from the pest control the new residents provide.

To listen to the full conversation with Merlin Tuttle, log onto the Berkshire Botanical Garden’s Growing Greener podcast at

Be-a-Better-Gardener is a community service of Berkshire Botanical Garden in Stockbridge. Thomas Christopher is a volunteer at Berkshire Botanical Garden and is the author or co-author of more than a dozen books, including “Nature into Art and The Gardens of Wave Hill” (Timber Press, 2019). The companion broadcast to this column, Growing Greener, streams on, Pacifica Radio and NPR and is available at his website,