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Bats are among the most misunderstood animals, yet they are vital to maintaining healthy ecosystems. They eat huge quantities of night-flying insects. And they pollinate plants, such as bananas, avocados, and peaches.

Bats are very fussy about where they will live but they will use well-constructed houses. While the basics are covered here, detailed instructions are available from Bat Conservation International.

Design

Your bat house should be at least 2’ tall, have chambers at least 20” tall and 14” wide. Provide a 3” to 6” landing area. Most bat houses have one to four roosting chambers – the more the better. Roost partitions should be carefully spaced ¾” to 1” apart. All partitions and landing areas should be roughened. Houses that are 24” tall need vents 6” from the bottom. Houses that are 36” tall or more should have vents about 12” from the bottom.

Construction

A combination of exterior plywood and cedar is best. Plywood for bat-house exteriors should be at least ½” thick with at least four plies. Do not use pressure-treated wood. Any screws, hardware or staples used must be exterior grade. Caulk all seams. Alternative materials, such as plastic or fiber-cement board, may last longer and require less maintenance.

Sun exposure

Houses where summer temperatures are less than 80° F should receive at least 10 hours of sun. At least six hours of sun is recommended where it is 80-100° F. Full, all-day sun is often successful in all but the hottest climates.

Mounting

Bat houses should be mounted on buildings or poles. Houses mounted on trees or metal siding are seldom used. All bat houses should be mounted at least 12’ above ground. Bat houses should not be lit by bright lights.

Protection from predators

Houses mounted on the sides of buildings or on metal poles provide the best protection from predators. Metal predator guards may be helpful, especially on wooden poles. Houses should be placed at least 20’ from tree branches, wires or other potential perches for aerial predators.

Avoiding uninvited guests

Use of ¾” roosting spaces reduces the risk of wasps . Open-bottom houses greatly reduce problems with birds, mice, squirrels or parasites, and guano does not accumulate inside.

Timing

Bat houses can be installed at any time of the year, but they are more likely to be used during their first summer if installed before the bats return in spring. When excluding bats from a building, install the bat houses about six weeks before the actual eviction.

 

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