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Bats in Buildings


Rafinesque’s big-eared bat,
Corynorhinus rafinesquii Credit: Mylea Bayless, BCI

Once, ancient forests covered most of eastern North America, prairies stretched across the Great Plains, the arid southwest boasted a vast array of plant communities and habitat types, and to the north great boreal forests stretched to the tundra. A vast network of rivers and streams fed the land, and quiet, open water dotted the land in beaver ponds, glacial lakes, and bison wallows.

With the arrival of Europeans, eastern forests rapidly fell to large-scale logging and agriculture. People seeking new land headed west and plowed the prairies of the Great Plains, captured and diverted open water, cleared forests, and fenced the western landscape. Some colonial (social) bat species adapted to the new shapes on the landscape and made use of barns and outbuildings, which were warm, dry, and fairly safe from predators. But in many areas, agriculture has recently given way to residential development, forcing bats to use the only habitat left—houses and the infrastructure of suburban life, like storefronts, culverts and bridges. Bats share our habitat and are a natural part of our world, and they need our help now more than ever to replace disappearing habitat.

Obviously, no one should share living quarters with wild animals, but bats using houses or other buildings are in a perilous predicament. Frequently they are exterminated; if they are lucky, they are evicted. Unfortunately, suitable habitat is now extremely limited and bats may have nowhere to go once evicted. Most building colonies are comprised of mothers and their young. Poorly timed exclusions (evictions) of bats from buildings can trap flightless young inside, preventing mothers from returning to them and resulting in the pups’ starvation and death. Besides being terribly cruel, the practice of separating mothers from young, or outright extermination, causes the loss of hundreds of years of reproductive potential. Bats reproduce very slowly, and every mother or baby that dies means that potential descendants are lost too. Every lost maternity colony pushes bats closer to oblivion.

What to do if you find a single bat in your house or business


Credit: Bat Conservation International

A solitary bat – often a lost youngster – will occasionally fly into a home, garage or other building through an open door or window. When this happens, the bat’s primary goal is to escape safely back outside. As long as no direct human contact with the bat has occurred, it can be released outdoors, but these bats will usually leave on their own if a window or door to the outside is opened, while others leading to the rest of the building are closed.

If the bat does not leave on its own, it can be safely captured and released outside. Wait until the bat lands, then cover it with a small box or other container. Slip a piece of cardboard between the wall and the container, gently trapping the bat inside. Wait until nightfall and, with the bat inside the cardboard-covered container, take it outdoors and release it.

If the bat appears unable to fly and falls to the ground, it may be injured or sick. In that case, gently return it to the box, cover it and call a local wildlife rehabilitator or in the case of a potential rabies exposure, contact your local animal control or public health office.

If bats are roosting in your building


Pallid bats, Antrozous pallidus, in the rafters Credit:

There may be little reason to evict bats from areas where they don’t come into contact with humans, but when exclusion is the best option, it’s important to fully understand the process and not cut corners.

It is also essential in scenarios involving large numbers of bats being displaced to install one or more bat houses as replacement roosts. Bat houses should be installed as far in advance of the exclusion date as possible—weeks or even months ahead, and should be within the flight path of emerging bats.

Keeping bats in the vicinity of their former roost allows people to continue to take advantage of their pest suppression services, and may prevent bats from simply moving into another building.