Media & Education
BATS Magazine

Volume 20, Issue 2, Summer 2002

North American Bat House Research Project

BCI's Volunteer Researchers Design Better Homes for Bats

By Mark Keiser

America's first known bat houses were built near San Antonio, Texas, in 1902. Hardly anyone noticed, and the idea of artificial bat roosts languished for the next eight decades. Then came the 1980s, and Bat Conservation International became the pivotal promoter of bat houses as an inexpensive way to help bats while cashing in on their voracious appetites for bothersome insects.

Bat houses began popping up in backyards, farmlands, and orchards around the U.S. and Canada, but their effectiveness was still hotly debated as recently as the early 1990s. Few systematic observations existed on the sizes, shapes, colors, building materials, or locations bats might prefer.

In 1992, BCI conducted a comprehensive survey of more than 400 bat house landlords. The study, which found bats using more than half the established houses, effectively erased skepticism about bat house utility. And it generated the first reliable data about bat roosting preferences over broad areas of North America.

The new findings led to the first edition of BCI's The Bat House Builder's Handbook, which remains one of the University of Texas Press' bestsellers. And it led BCI, in the spring of 1993, to launch the North American Bat House Research Project, a long-term volunteer effort to quantify roosting preferences and fine-tune artificial roosts to better meet the needs of bats.

Thousands of volunteer Research Associates from coast to coast make the Bat House Research Project possible. Each Associate receives The Bat House Builder's Handbook, now in its sixth revision, and The Bat House Researcher newsletter. Each year, Research Associates, who range from biologists and students to farmers and urban homeowners, contribute invaluable data about the bat houses they have installed.

As a direct result of this information sharing, bat house success rates have more than doubled since 1995. In our 2000 survey, 155 Research Associates reported sheltering more than 25,000 bats in 636 houses. Over 100,000 more were roosting in specially designed larger roosts in six U.S. states and one Canadian province. At least 13 species now use North American bat houses.

Data analysis demonstrates the importance of vents, landing areas, painting, caulking, proper placement, and the impact of size and design on success. The smallest houses do not perform as well as larger ones; nursery houses with roost chambers at least 25 inches (63.5 centimeters) tall are achieving overall occupancy rates of 85 percent. Those rates approach 96 percent for houses that are built and painted or stained according to BCI criteria and located where they receive adequate sunlight in areas of mixed agriculture and natural vegetation.

As we continue to improve bat house success rates, the project is also broadening its research objectives. One continuing priority is an investigation into the use and effectiveness of bat houses as part of integrated pest management strategies for agriculture.

We are also working with research partners to develop new artificial roost designs to accommodate bats that don't roost in crevices and are therefore not candidates for traditional bat houses. For example, with Walter Sedgwick's support, concrete culverts are being stacked vertically to simulate the increasingly rare giant hollow trees that were formerly used as roosts by Rafinesque's big-eared bats (Corynorhinus rafinesquii) in the southeastern United States. Early results are very encouraging.

Bat houses are now successfully used throughout North America and in Africa, Asia, Australia, the Caribbean, and Europe. Yet much remains to be learned to maximize their potential for varied species and environments. Research Associates are still needed.

Here's a sampling of the project's many outstanding bat house landlords:

Marvin Maberry
The innovator
Retired highway patrol officer Marvin Maberry of Daingerfield, Texas, designed the first plastic bat house in 1989 and attracted his initial tenant, a big brown bat (Eptesicus fuscus), that year. He keeps experimenting with new materials and techniques and now has more than 700 big browns in a dozen bat houses, one of which hosts more than 500 bats -- the largest group of big brown bats reported in any bat house.

Maberry's still making improvements, building and selling eight bat house models, which have been certified as "Bat Approved" by BCI. Thousands of bats, all across North America are now benefiting.

Cal Butchkoski
The biologist
In 1989, Cal Butchkoski cobbled together a bat house from an old army-surplus ammo box. A decade or so later, this Pennsylvania wildlife biologist has built and installed more than 70 bat houses and monitors dozens more. With an incredible occupancy rate of 91 percent, he is providing roosts for thousands of bats.

Among his many contributions to the field of artificial bat roosts, Butchkoski introduced the ventilation slots now used on most bat house designs. And a big 8x8x8-foot (2.4x2.4x2.4-meter) condo he designed is being used by thousands of bats in four U.S. states and one Canadian province.

When nuisance colonies must be excluded from buildings, he has saved countless bats by convincing people to provide strategically placed bat houses before beginning the exclusion.

When not improving bat house designs, Butchkoski often inventories summer nursery colonies in buildings or surveys winter hibernation sites in mines and caves, many of which he has helped protect with bat gates. Bats have few more valuable allies.

Kent Borcherding
The woodworker
Adding a commitment to bats to expert woodworking skills has resulted in the creation of some 500 bat houses since 1994. Retiree Kent Borcherding of Hazel Green, Wisconsin, continually tests new materials, designs, and techniques, then shares what he's learned with other enthusiasts.

He gives frequent lectures about bats and has provided over 50 of his bat houses for use in Illinois and Wisconsin state parks. These alone now shelter more than 5,000 bats.

Frank Bibin
The farmer
Hickory shuckworms were damaging more than 30 percent of the crop at Frank and Teresa Bibin's organic pecan orchard in Georgia. Conventional growers often spray pesticides six times a year to control shuckworms -- not an option at an organic farm.

Searching for non-chemical alternatives, the Bibins joined the Bat House Research Project and built their first nursery house in July 1996. Although bats had rarely been seen on the farm, more than 100 free-tailed bats (Tadarida brasiliensis) and evening bats (Nycticeius humeralis) had moved into the bat house by 1998. The Bibins saw fewer moths that year and suffered less crop damage from shuckworm larvae.

Excited by the prospect of success, the Bibins added 12 more houses over the next few years and now have nearly 3,000 bats patrolling the skies over their orchard. Bibin, who now sells BCI-certified bat houses, reports virtually no losses to shuckworms. Success stories don't get much better than that.

Mark Kiser is Project Coordinator of the North American Bat House Research Project. To join the North American Bat House Research Project, go online at or call 512-327-9721. Our websites also offer The Bat House Builder's Handbook, the Building Homes for Bats video, certified bat houses, and free plans for building a small bat house.

Mark Kiser is Project Coordinator of the North American Bat House Research Project. To join the North American Bat House Research Project, go online at or call 512-327-9721. Our websites also offer The Bat House Builder's Handbook, the Building Homes for Bats video, certified bat houses, and free plans for building a small bat house.

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