Little brown bats offer remedy for pesky mosquitoes

Scott Doggett Wild Neighbors
Posted 7/10/24

Washington’s little brown bats are many things, but they aren’t bloodsucking fiends. 

Those would be vampire bats and, I’m pleased to report, they don’t hang out …

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Little brown bats offer remedy for pesky mosquitoes


Washington’s little brown bats are many things, but they aren’t bloodsucking fiends. 

Those would be vampire bats and, I’m pleased to report, they don’t hang out north of the U.S.-Mexico border.

But little brown bats, or LBBs, are the stuff of nightmares — for mosquitoes, moths and other bugs, but mostly mosquitoes, throughout most of the continental U.S. and Canada.

Thankfully many LBBs reside in Jefferson County. Never mind that they weigh less than a baby’s sock and the largest couldn’t hide a ruler with its wings outstretched. Little brown bats put electric bug zappers to shame. 

“How many bugs we talkin’ about?” you ask. A little brown bat can locate, catch and eat 1,800 mosquitoes between dusk and dawn, says a study published in the July-October 1960 issue of “Animal Behaviour.”

Catching so many bugs so quickly is energy intensive, which is why a little brown bat consumes more than half of its body’s weight in insects nightly, says a study published in the May-June 1989 issue of “Physiological Zoology.”  

But wait, there’s more. A female little brown bat will give birth to a single pup. As it grows, the pup will demand more breast milk from its mom, requiring her to gobble more insects.

At the lactation peak of 18 days, a female LBB must consume 0.35 ounces of insects in a single night, or 125% of her own body weight. If you are a 120-pound mother and face a comparable energy requirement, you must chow down 150 pounds of food in 24 hours.

That’s hard duty for a mother bat, never mind that bat pups have baby teeth. But she provides you with a fabulous opportunity if you’re troubled by skeeters at your home. Just install a bat house and let bats rid you of mosquitoes.

If you’ve got a bat house in your backyard with 30 lactating LBBs roosting in it, the skeeters out back haven’t got a chance. If you don’t own a bat house, consider getting one.

Or do what I did and get eight. I’m hoping to one day house 240 little brown bats and find a way to charge them rent. Which reminds me: Google “WDFW bats” for answers to most of your batty questions. 

Little brown bats have eyesight comparable to ours — the expression “blind as a bat” is hogwash — but it is echolocation, not eyesight, that allows the mouse-eared bats to locate prey on the darkest of nights and in the darkest of caves.

Echolocation starts with the LBB emitting clicky “search-phase calls” at a rate of 20 per second through its mouth, Abby Tobin, a bat biologist for the Washington Department of Fish and Wildlife, told me the other day.

When a search-phase call strikes an object, it generates an echo that the bat hears, much like a sonar operator sends out high-frequency sound waves and listens for echoes. The echoes provide info about an object’s distance and size.

If an object’s echo profile matches that of prey, the bat unleashes a barrage of “feeding buzzes” to pinpoint the object’s location and the bat closes in, Tobin said. When the predator and prey are eye to eye, all that’s left is the catch. 

The same way a baseball glove has webbing that keeps a ball from passing between fingers, the bat’s wings and tail have multiple bones connected by webbed membrane to contain a bug.

The bat also has fast-twitch muscles, which close the wings and tail super quickly, giving the bug no time to flee. And the webbing and the muscles allow the bat to fly into catch position lightning fast.

Unlike the uber-nimble wings of a little brown bat, a bird’s wings contain rigid bones controlled by muscle at the shoulders. The design doesn’t permit breakneck diving, turning, braking and grasping, which is why the LBB is an aerial acrobat and the bird is a jetliner by comparison.

Despite its remarkable abilities the LBB isn’t invincible. Indeed, the little brown bat, one of the most common bat species of the 45 in North America, is facing an existential threat.

White-nose syndrome, a fungal disease thought to have originated in Europe that kills LBBs, was first discovered in North America inside a cave in upstate New York in February 2006, according to an article in the August 2010 issue of “Science.”  

Since then, white-nose syndrome has infected dozens of bat species and left millions of dead bats in its wake. It can now be found in much of Canada and most of the U.S., including Jefferson County, said the WDFW’s Tobin. The mortality rate of those infected tops 90%, she said.

Fortunately for us, white-nose syndrome does not cause illness in humans. But rabies can kill people and some little brown bats carry the disease. 

That said, rabies kills fewer than 10 Americans annually, according to the Centers for Disease Control and Prevention. Still, that’s enough that you should keep bats at arm’s length. Resist the urge to touch, feed, treat or wash a bat. But do contact the WDFW if you have a bat colony in your yard (Google “WDFW bats” for contact info).

“But what about my beehive hairdo?” you wonder. Bats don’t attack people and they aren’t attracted to beehive hairdos, never mind the old horror movies. If a bat crashes into your B-52, it’s likely a clumsy juvenile learning to fly, Tobin said.

Nothing personal. 

Scott Doggett is a former staff writer for the Outdoors section of the Los Angeles Times. He and his wife, Susan, live in Port Townsend.