July 6, 2016 -- Can bats help keep mosquitoes at bay?
The hope that they can is boosting sales of bat houses and fueling conversation on social media, where stores are advertising bat houses for mosquito control. From Pinellas Park, FL, to North Hempstead, N.Y., to Columbus, OH, headlines are popping up about communities and homeowners putting up bat houses to help control insects, including mosquitoes.
They've been good business for Jay Lee, owner of Pest Entry Management in Nashville, which specializes in chemical-free pest control. He says he has sold 80 to 100 bat houses this season compared to three or four last year, mainly because of fears of Zika. His new nickname: “Batman.”
The rectangular boxes, typically made of wood, have an open bottom and an envelope-like opening at the top. The inside has chambers or cells for bats to hang out, and the boxes are mounted on poles or trees.
One of Lee's customers, David Calvo, says fears of the Zika virus prompted him to spend a few hundred dollars to put up his first bat house. Calvo has three children and a swimming pool. They’re outside a lot, and they live next to the Cumberland River in Tennessee, a haven for mosquitoes.
“In the past, the city has come by and sprayed chemicals, and I’m not a fan of spraying chemicals. I was thinking of a way that would be safer for my family,” he says.
With fears of Zika and other mosquito-borne illnesses like West Nile hitting this summer, bats are touted as an environmentally friendly way to combat the dreaded pests.
There’s only one problem.
Using bats doesn’t work -- at least for controlling mosquitoes.
“Bats are very poor predators of mosquitoes,” says Joe Conlon, a medical entomologist with the American Mosquito Control Association. While they’ll eat the insects, they prefer moths and beetles.
“Less than 1% of their foodstuffs are mosquitoes,” Conlon says. “They would starve if they relied on mosquitoes.”
Shelly Redovan, head of the Florida Mosquito Control Association, says the state of Florida has tried using bats to control mosquitoes.
“They tried bat towers, bat houses, and they were a dismal failure,” Redovan says. “Most of the time, bats don’t like coming to the houses. They like to find their own places. Down here, it’s our palm trees.”
It’s even less likely that a bat will meet up with Aedes aegypti, the species of mosquito that can spread Zika, a virus associated with devastating birth defects in babies whose mothers have been infected. Aedes aegypti mosquitoes operate during the day, while bats do their feeding at night.
Redovan says that this type of mosquito also stays close to homes, buzzing around patios and under eaves, waiting for a blood meal. Bats don’t venture so close.
“Unfortunately, it’s a disservice to people, telling them that bat houses will help,” Redovan says.
So where did the idea get started? According to the University of Wisconsin in Madison, it may have been from a lab study done in the 1950s. Researchers released bats in a mosquito-filled room and said they could catch up to 10 mosquitoes per minute. The results have been extrapolated to various numbers along the way. Several social media posters have claimed that one bat can eat 10,000 mosquitoes a night.
But bats in the wild aren’t locked up in a room with only one type of food. On their own, brown bats prefer moths and spiders.
“There is no evidence that increasing the population of bats in an area will reduce the numbers of mosquitoes enough to affect human biting rates,” the article says.
Still, putting up a bat house can’t hurt, and it also may help replenish the bat population, which has been decimated by white-nose syndrome, a fungal disease that has killed millions of bats in the middle and eastern U.S. and Canada.
“People are becoming aware of bat species decreasing and are increasing roosting opportunities for bats,” says Todd Sinander, a senior biologist with Bat Management and Conservation in Carlisle, PA. The group has seen a gradual growth in bat house sales over the last 3 years, he says.
Store owner Lee put up a bat house in his own yard, and says while bats haven’t gravitated toward it, they do swoop around. He hasn’t been bitten so far this year, he says.
Calvo says he hasn’t noticed bats in his backyard yet, “but I have noticed I’m able to go outside and have peace of mind. We are nowhere near as infested as we’ve been in previous summers.”
How do you keep mosquitoes at bay?
If you’re still searching for a way to do that this season, the CDC and American Mosquito Control Association offer these tips:
- Get rid of standing water in your yard -- in whatever kind of container it has collected, from boat covers to gutters to bottle caps. Check furniture and pool covers for stagnant water, too.
- Scrub bird baths every 5 days to get rid of mosquito eggs just above the water line.
- If you have a pond on your property, keep the edges free of vegetation so mosquitoes can’t hide from predators. If you have an ornamental pond, stock it with top-feeding minnows.
- Use an outdoor insecticide spray in areas where mosquitoes rest, such as under patio furniture.
- Repair gaps and cracks in your septic tank, and cover open vents and pipes.
Brenda Goodman contributed to this report.