A bat house is an artificial structure designed to mimic natural roosting locations, such as hollow trees or rock crevices, that bats use for shelter during the day. Providing this habitat helps local bat populations, which are facing severe declines due to disease and habitat loss. This guide provides homeowners with the practical information needed to determine if installing a bat house is appropriate for their property and to maximize the likelihood of a successful installation. Making an informed decision requires understanding the ecological advantages, installation requirements, and safety precautions.
Ecological Role of Bats and Benefits to Homeowners
The primary benefit of attracting bats to a residential area is the natural control of insect populations. Most North American bats are insectivores and consume a remarkable quantity of night-flying pests, including mosquitoes, moths, and agricultural insects. A single adult bat can consume thousands of insects in one night.
The collective feeding activity of these animals provides an ecosystem service that benefits agriculture by reducing the need for chemical pesticides. The economic value of this pest control service to the U.S. agricultural industry is estimated to be billions of dollars annually. Beyond pest control, bats play a broader role in global ecosystems by acting as pollinators and seed dispersers, particularly in tropical environments. By installing a bat house, a homeowner contributes directly to conservation efforts, offering shelter to species threatened by habitat destruction and diseases like White-Nose Syndrome.
Site Selection and Installation Requirements
The success of a bat house depends entirely on meeting the requirements for temperature and location, which are more demanding than for birdhouses. The internal temperature is a factor for maternity colonies, which require a consistently warm environment, often exceeding 85°F, to promote the rapid growth of their young.
To achieve this warmth, the house must be mounted in a location that receives a minimum of six to eight hours of direct sunlight daily. In most climates, this means facing the bat house toward the south or southeast to capture morning and midday sun. In cooler regions, a dark exterior paint or stain maximizes solar heat absorption. In extremely hot climates, a lighter color may be necessary to prevent overheating.
The structure should be mounted at least 12 feet off the ground, with higher placements being more successful. Preferred mounting locations are on a sturdy pole or the side of a building, as these surfaces absorb and radiate heat more effectively and offer protection from predators. Mounting on trees is discouraged because foliage blocks sunlight and provides easy access for predators.
A clear flight path is necessary, meaning the area in front of the house should be free of obstacles for at least 20 feet. Bats need a reliable water source nearby, such as a pond or river, ideally within a quarter mile of the roost site. The house itself should be a multi-chamber design, with roosting chambers approximately three-quarters of an inch wide. Untreated, rough-sawn lumber is the appropriate material, as the bats need the texture to grip the interior surfaces.
Common Misconceptions and Safety Considerations
A significant concern for many homeowners is the risk of disease, particularly rabies. While bats are the most frequent source of human rabies cases in the United States, transmission to people is rare, averaging only one to three cases per year nationally. The risk is exclusive to individuals who have direct physical contact with a sick or grounded bat. The standard precaution is simple: never attempt to touch or handle a bat.
Another common concern involves bat droppings, known as guano. Bat guano is a highly effective, natural fertilizer, and the small amounts produced by a residential bat house pose little health risk. However, large, undisturbed accumulations of dried guano can create an environment where the fungus Histoplasma capsulatum can grow. Inhaling the spores from this fungus can lead to a lung infection called histoplasmosis.
To safely manage guano, especially when cleaning up larger deposits, wear a respirator mask and mist the guano with water before disturbing it. This prevents the fungal spores from becoming airborne. The fear that bats will seek entry into the home is unfounded, as they prefer the secure, high roosts provided by a properly installed bat house. Home entry typically only occurs if there is an existing, unintended opening in a structure. If bats are already roosting in a home structure, they must be safely excluded from the building before a bat house is installed to encourage them to adopt the new, external roost.