Bat houses offer shelter for bats, aiding conservation efforts and providing natural pest control. The effectiveness of a bat house depends entirely on its placement, which is the most influential factor determining occupancy. Specific instructions regarding height, sun exposure, and surrounding habitat must be followed to create a successful roost.
Optimal Height and Mounting Surface
The elevation of a bat house is a primary consideration. A minimum height of 12 feet above the ground is recommended, but 15 to 20 feet is better for success, providing greater security for the bats. This height also ensures sufficient vertical clearance for bats to drop and begin flight upon exit, while minimizing the risk of ground-based predator access.
The choice of mounting surface significantly impacts occupancy rates. The sides of buildings or metal/wooden poles are highly preferred over trees. Bat houses mounted directly onto the exterior of a wooden, stone, or brick building are often the most attractive choice because the structure’s mass helps stabilize internal temperatures. Mounting the house under an eave can also provide additional protection from rain.
Trees are generally poor choices for mounting because they typically offer too much shade, interfering with necessary solar heating. Furthermore, trees provide easy access for climbing predators like raccoons, and branches can obstruct the clear flight path bats need. If a pole mount is used, setting up two houses back-to-back, facing north and south, can offer bats a thermal gradient for regulating body temperature.
Essential Solar Exposure
The thermal environment inside the bat house is the most important factor, especially for successful maternity colonies, which have specific heat requirements. Mother bats need a consistently warm roost to reduce the energy required for raising their pups. An internal temperature range between 80°F and 100°F is optimal, achieved by maximizing the structure’s solar gain.
For a single house, the ideal orientation is facing south or southeast to ensure the house receives direct sunlight for the longest part of the day. The house should receive at least six to eight hours of direct sun daily; ten hours or more is better in cooler climates. The color of the house directly influences heat absorption.
A darker color, such as black or dark brown, is recommended for the exterior paint in areas where the average high temperature in July is below 95°F. In very hot regions, a lighter color may be required to prevent overheating.
Habitat Requirements for Success
Beyond height and solar orientation, the surrounding environment must provide the necessary resources for a bat colony to thrive. A successful location requires proximity to a permanent water source, such as a pond, lake, river, or large stream, as bats need to drink frequently. Placement is best within a quarter mile (400 meters) of a water body.
The flight path to and from the house must be completely unobstructed to allow bats safe and easy access. It is recommended to have a clear, open area of at least 20 feet below and in front of the entrance, free from tree branches, utility wires, or potential perches for aerial predators. Avoiding areas with strong artificial light is also important, as bright lights can deter bats from using the roost. The surrounding landscape should be diverse, featuring a mix of forest, agricultural land, and open spaces, which ensures a constant and varied supply of insect prey.