When Frank and Teresa Bibin bought their twenty-four-acre property in south Georgia, the new landowners battled swarms of hungry mosquitoes every time they ventured out into a summer evening. Then Frank Bibin read how bats might help control the moths that plagued his pecan orchard. He installed two bat houses, and in 1999, six hundred Mexican free-tail bats moved in, gobbling up the moth problem. The mosquitoes met a similar fate.
What’s your backyard like this summer? Can you grill a burger unscathed, or are you fodder for the swarms? If you’re concerned about overusing chemical repellents, you might find a friend in furry flying mammals, depending on where you live. Bats are opportunistic feeders, meaning they’ll eat beetles, moths, flies, mosquitoes, and whatever else looks tasty. Since beetles and moths cause billions of dollars in crop damage every year, the nonprofit organization Bats Conservation International (BCI) promotes bats to growers as part of natural pest management. But some growers are discovering an added bonus to having bats around.
"The bats make life more comfortable," says Betty Koch, an organic grower in Oregon, "since we don’t have mosquitoes." The Kochs’ colony of little brown bats arrives with the warm weather each spring and resides in some fourteen bat houses installed throughout the property. They remain as long as pests are around to fill their stomachs.
And mosquitoes are on the menu. A 1977 study in the journal Ecology found little brown bats fed on mosquitoes in 77 percent of their evening forays, consuming the bloodsuckers throughout the summer. BCI reports that little brown bats, big brown bats, and Mexican free-tails are three prevalent species in the U.S. most likely to occupy bat houses and feed on pests. The big brown bat specializes in beetles, while the Mexican free-tail bat lives in southerly climes. The little brown — which can eat 50 percent of its body weight each evening — is common throughout the Midwest and specializes in feeding on small insects — including mosquitoes.
"Little brown bats do feed on mosquitoes," says BCI biologist and North American Bat House Research Project Coordinator Mark Kiser, "and having a bat house in your yard is likely to cut down on mosquitoes, though it won’t solve your problem completely. You’ll want to integrate them into a mosquito control strategy," like also building purple martin houses to attract the insect-hungry birds.
Bats are wild animals, of course, and Kiser doesn’t recommend attracting bats to a home where small, curious children might try to handle them. Beyond that, however, the need for concern is almost nonexistent. You may have heard, for example, that bats carry rabies. But don’t worry: you have less chance of getting rabies from a bat than you do of getting encephalitis from a mosquito.
The Welcome Mat
If you live in a rural area, or near woods or a greenway — or if you reside near a lake or pond or stream — then the little brown bats you seek may already be nearby. You just need to entice them to spend a little more time in your mosquito-infested yard. And for that, you need a bat house.
BCI publishes The Bat Builder’s Handbook, a comprehensive guide to building and installing bat houses. For those less inclined to carpentry, BCI also sells ready-made bat boxes that you can install according to the handbook’s guidelines. Either way, there’s an art to properly installing a bat house that conforms to bat tastes. BCI recommends locations where bat houses receive at least six hours of direct sun each day. Homeowners have the most luck in areas within a quarter mile of a permanent water source and near natural or agricultural areas. Bats that are already attempting to live in local buildings bode well, too, since they’re more likely to find any houses that you install.
If your local habitat area has potential, you’ll want to give careful consideration to bat house design. Houses should be at least two feet tall and fourteen inches wide with a landing area below the open-bottomed entrance. Bats crawl up into the roosting chambers, which should be partitioned about three-quarters of an inch to one inch apart. The small spacing discourages wasps from building nests in the box. Durable plastic screening installed inside the chambers also helps bats cling to the roost.
Hardly anybody likes extreme heat, not even bats, so install six inch-tall side vents to help keep the roost comfortable when July temps head into the nineties. On the other hand, dark exterior paint, like a very dark brown, also helps absorb sunlight early in the day to shake off the morning chills.
And don’t skimp on building materials. Bats are most likely to first occupy houses installed before spring, when they emerge from hibernation. If you build your bat house later in the year, it might take two or three years for bats to find it and settle in — particularly if you haven’t noticed any bats in the area before. Quality materials will hold up to outside elements until the mammals discover your location.
Once you have a house ready to go, you’ll need to think about where, exactly, to mount it. Successful houses are at least ten feet above the ground (fifteen to twenty feet is better). But bats don’t like houses on trees, probably because trees give predators easier roost access. So wood or stone buildings or poles make good mounts. Try mounting a house under the eaves of the south, southeast or east side of a stone building with good solar exposure. Be sure to avoid areas that are brightly lit at night.
If all this sounds like a lot of detail, help is available. BCI’s Bat House Research Project assists homeowners who want to provide summer housing for bats. You can get more information about bats on their Web site and even order a bat house if you go to "Bat House Project" on the left-hand column of their homepage. Or you can call the Austin-based BCI at the number listed below.
Mosquitoes are out there, but so are the bats. Little brown bats might not be a mosquito panacea, but they just might help you take back your backyard.
Resource
Bat Conservation International, 512-327-9721