Bat houses offer valuable shelter for local bat populations, which are natural and highly effective controllers of nocturnal insect pests. These artificial roosts are particularly important for female bats, providing a warm, secure location to form “maternity colonies” where they can raise their young. Maximizing the chances of attracting bats to a newly installed structure relies on careful planning and adherence to specific environmental requirements. Understanding the precise needs of these mammals is the first step in creating a successful, long-term roosting site.
Choosing the Best Location for Installation
The success of a new bat house is determined by its position, starting with the proper height. A bat house must be mounted at a minimum height of 10 to 12 feet off the ground, though a range of 15 to 20 feet is often recommended for better results. This elevation provides a safe drop space necessary for bats to take flight and helps to minimize the risk of predation from terrestrial animals, such as cats and raccoons.
Achieving the correct internal temperature is the single most important factor for attracting and retaining a maternity colony. The interior of the house needs to consistently reach and maintain temperatures between 80°F and 100°F during the summer months. To achieve this, the house must receive substantial direct sun exposure, ideally for six to eight hours each day, especially the morning sun.
Orienting the house to face South, Southeast, or East is generally the most effective way to capture this necessary solar energy. While mounting on a tree may seem convenient, it is strongly discouraged because foliage can quickly block the sun and interfere with the required solar heating. Furthermore, trees provide easy access for predators and create flight path obstructions that deter bats.
Mounting the bat house on the side of a building or a sturdy, dedicated metal or wooden pole is a superior option. A pole mount offers the greatest flexibility for ensuring unobstructed sun exposure and a clear, 20-foot radius flight path. Mounting a house directly onto a structure, like a barn or a house, can also be beneficial, as the building material radiates heat, providing greater thermal stability to the roost.
Preparing the Structure for Occupancy
Before installation, several modifications should be made to the structure to make it habitable. In most climates, especially those that are moderate or cool, the exterior must be painted or stained a very dark color, such as black or dark brown. This dark color maximizes the absorption of solar radiation, which is necessary to reach the high internal temperatures preferred by maternity colonies.
Preventing drafts is another structural detail that significantly increases the appeal of the roost. Bats are highly sensitive to air movement, so all joints and seams on the exterior of the house, particularly the roof and the upper two-thirds of the structure, should be sealed with high-quality, non-toxic caulking. An airtight structure helps to maintain the stable, warm microclimate that female bats seek for raising their pups.
The interior surfaces and the landing pad must be roughened to allow bats to easily grip the wood. If the wood is not already grooved, this can be achieved by adding a plastic mesh or scoring the wood horizontally at half-inch intervals. The rough texture is particularly important for juvenile bats, which need a secure hold as they learn to fly.
While many people inquire about shortcuts, there is no reliable chemical or material lure that can be used to speed up occupancy. Existing evidence suggests that commercial attractants or even bat guano are ineffective and should be avoided. Bats will investigate and find suitable roosts on their own during their nightly foraging flights, relying entirely on the quality of the structure and its location.
Patience and Managing Expectations
Installing the bat house at the correct time of year can increase the speed of initial occupancy. The structure should ideally be installed during the fall or winter months, ensuring it is ready and cured before the bats return from hibernation and begin their spring maternity season. This timing gives the house a chance to weather naturally and be in place when bats are actively searching for summer roosting sites.
Even with perfect installation, immediate occupancy is a rare occurrence. It is important to realize that for a new structure, the typical waiting period ranges from one to three years. In fact, for a percentage of houses, it can take up to five years before a colony takes up permanent residence.
Studies have shown that about 50 percent of well-designed, properly-placed houses are occupied within the first year, with that number rising to 90 percent within two years. The presence of nearby natural resources can influence these timelines and the long-term success of the colony. Bats are more likely to find and remain in a house if it is located within a quarter-mile of a permanent water source, such as a pond or stream, which provides the necessary feeding grounds to sustain a large maternity colony.