Bats consume enormous quantities of insects and are valuable allies when it comes to battling many of our worst agricultural pests. A growing number of farmers, organic growers, and backyard enthusiasts are interested in attracting bats for pest reduction and for wildlife conservation projects. The good news is that bats will use bat houses if you follow a few guidelines and are patient. Bats make good tenants who are happy to pay their rent with free insect control.
If you haven’t seen a bat house lately, it’s time to take a new look. Bat house designs and placement techniques have advanced considerably since the 1980s, especially in just the past few years. Unfortunately, many old, outdated blueprints are still available, and many commercially-built bat houses are not suitable for bats at all. When poorly-made or -placed bat houses fail to attract bats, it hurts legitimate conservation efforts and creates the impression that bat houses do not work. Nothing could be further from the truth. Research shows that when bat houses are constructed and placed to meet bats’ needs (such as proper sun exposure and protection from predators), success is very high.
Bats in Texas
If you reside in Texas and want to attract bats, you’re in luck. The Lone Star state is number one when it comes to bats, with the most bats and bat species in the nation. Texas has 33 of the 45 species found north of Mexico and has the largest bat colonies, including the largest on the planet (Bracken Cave, near San Antonio, is home to 20 to 40 million Mexican free-tailed bats). Bat houses have been intensively researched here, and five species, including Mexican free-tailed bats, evening bats, big brown bats, cave myotis, and pallid bats, have been documented in Texas bat houses. Several other species that occur in Texas are also known to use bat houses, so no matter where you live, chances are very good there are several species in your area looking for a new roost.
Several Texas farmers participating in the North American Bat House Research Project have succeeded in enticing bats to their bat houses and rely on bats as part of their Integrated Pest Management strategies. Bat Conservation International (BCI), a nonprofit organization based in Austin, established the North American Bat House Research Project (NABHRP) in 1993 to determine what factors make bat houses successful. With thousands of bat houses reported to the Project from across the U.S. and Canada, Research Associates have contributed much to our knowledge of bats’ roosting needs.
One farmer that knows the value of his bats is Terry Micnhimer, who raises sweet sorghum, corn, and cattle near Falls City. To use the official “Sweet Sorghum” trademark logo on his projects, he cannot use any chemical pesticides. Although his corn is not grown for commercial purposes, it also cannot be sprayed with pesticides, because it is adjacent to the sorghum. When he discovered that his corn was being damaged by the larvae of the corn earworm moth, one of the most destructive agricultural pests in the U.S., he needed to find an alternative to chemicals to solve his problem. Bat houses seemed like a logical answer.
In 1994, Micnhimer installed a pair of BCI nursery houses next to his sorghum field, less than a quarter-mile from a large pond. The houses were mounted on a sturdy pole, facing north and south. A large metal roof shades them from the hot midday sun. The next year, a colony of Mexican free-tailed bats used the south-facing bat house, and by 1996, more than 200 free-tailed bats and evening bats had moved into both houses. Once bats became established, Micnhimer reported that his corn earworm problem disappeared.
In Medina, the Apple Capital of Texas, Baxter, and Carol Adams have relied on bats for many years to protect their apple crop. They have had great success with their bat houses, attracting a nursery colony of about 500 Mexican free-tailed bats. With over 10,000 apple trees on their ranch, the Adamses have many reasons to appreciate the bats’ services. Apples are vulnerable to codling moths, which lay their eggs directly on the fruit. The developing larvae feed on the applies, destroying them. Luckily, moths are the favorite food of the free-tailed bat, and thanks in part to the bats, the Adamses do not need to spray their apples with any chemical pesticides. The bats also provide another free service as well. Their droppings, known as guano, are rich in nitrogen and make an excellent natural fertilizer. The Adamses harvest their “black gold” with simple collectors placed underneath the bat houses.
To help people build and install bat houses correctly, BCI offers The Bat House Builder’s Handbook, a comprehensive source of information and bat house plants. Research Associates that join the NABHRP receive a copy of the Handbook, the Bat House Researcher — a biannual newsletter covering the latest bat house research findings, “Guidelines for Experimentation” — tips for conducting bat house experiments by geographic region, Research Associate Listings — to contact others in the Project, a Data Report Form, opportunities to compete for special grants and recognition and personal consultation as required. For more information on bats, bat houses, or the research project, contact BCI at 512-327-9721 or at www.batcon.org.