Bats in Buildings


QUESTION: If I install a bat house, will the bats move into it AND leave my house?

ANSWER: Bat houses are excellent management tools that can provide displaced bats with a safe alternate roost away from structures where they are unwelcome. And while it is true that bats in a bat house are not in your house, bats are faithful to their homes, and very rarely voluntarily leave an active roost for a bat house.

Even the most well-planned and humanely-intentioned bat exclusion means habitatloss and displacement for bats. For that reason, when an exclusion is planned, BCI recommends installing one or more bat houses nearby, well in advance. Learn more by visiting our bat house page

QUESTION: How can I get bats to leave and not come back?

ANSWER: When bats roosting in a structure are unwelcome, exclusion is the only permanent solution. The objective should be to get all bats safely out of a building and to keep them out permanently. Although projects can vary in scale depending on structure type, species present and roost location, the process is the same regardless of the number of bats or how long they’ve been there. A complete description of the bat exclusion process can be found here.

QUESTION: What if I find a bat (or a colony) out in the open?

ANSWER: Bats are sometimes found alone or in large numbers roosting on the exterior of structures, or in open structures like parking garages. These are usually temporary stopovers, sometimes during fall and spring migration. Left alone, these bats will usually continue on their way within a few days or weeks.

QUESTION: What if you WANT bats in your attic?

ANSWER: Each year, BCI staff field hundreds of inquiries about excluding bats from buildings. Occasionally, however, we get a call from somebody wanting to increase the numbers of bats in their building! Often these are abandoned buildings used for interpretive purposes, structures housing endangered or threatened species, or buildings owned by people who simply realize that the benefits of bat residents can outweigh drawbacks. See our bat house page where we have re-posted the archive of Bat House Research Project newsletters we published during our 10-year research project, for ways to accommodate more bats, while minimizing problems from guano or noise.

QUESTION: How I can discourage bats from roosting on my porch?

ANSWER: Some species such as pallid bats (Antrozous pallidus) use open porches, patios, or garages as temporary night roosts for feeding or social activity. Bats are usually absent from these sites during the day, and insect parts or guano may be the only evidence that bats were roosting the night before. These night roosting bats can be discouraged by making their roosting area ‘less comfortable’ by adding clutter or making roosting surfaces difficult to hang on.

Bat Roosting Deterrents (To be employed only when bats are NOT present)

  • Mylar Balloons floating near the roost
  • Strips of mylar material or even tin foil tacked up at the roost so they move in the breeze
  • Curling ribbon (long pieces, curled and tacked at the roost)
  • Plastic taped over the roosting spot (to make it too slick for their feet to hold on and hang there)
  • Bright lights and fans


These ideas are intended for night roosting bats (i.e., bats roosting under eaves of a roof or on a porch, etc., digesting the insects they have eaten), and the idea is for the bats to develop new habits. Day-roosting bats are usually in nooks, crannies, and crevices and must be properly excluded.

QUESTION: What if I find a bat in my patio umbrella?

ANSWER: Some bat species, including tri-colored bats, evening bats and southeastern myotis, find the crevice-like folds of a closed patio umbrella to be a perfect day or night roost. These are often transient solitary bats , but small maternity groups of Evening bats have been observed in early summer. If mothers and pups are present, they should be left undisturbed until pups are flying on their own. Then, if the bats are not welcome, the umbrella can be carefully opened after the bats leave at night and left partially open to discourage roosting.

QUESTION: Are bats dangerous?

ANSWER: Bats do not attack people, and reports that they do are usually related to incidents where bats fly near people in swimming pools as they swoop in for a drink, or near people outdoors in the summertime, when insects are abundant around us; bats DO attack insects! However, bats, along with several other mammal species, are a “rabies vector” species. That means that there will always be incidences of the rabies virus in bat populations. However, bats do not “carry” rabies. The vast majority of bats do not become rabid and there is no evidence of epidemic outbreaks in bat colonies. That is because when bats become infected with rabies, they die from the disease. Rabies can only be contracted if the virus enters the nervous system through a bite wound or mucous membranes (eyes, mouth or nasal passages). The virus is not spread through contact with blood, urine or droppings (guano), but through contact with saliva or central nervous system tissue. The virus is almost always contracted by way of a bite from a rabid animal.

CREDIT: J. Scott Altenbach

QUESTION: What is an ‘undetected’ bat bite?

ANSWER: Many people believe that it is common to be bitten by a bat and not feel it. Though it is not impossible for that to happen under unusual circumstances, most professionals who handle bats on a regular basis will tell you that bat bites hurt. Bats have small, sharp teeth made for biting through insect parts and a bite from an insectivorous bat feels very much like a needle jab. However, because those teeth are small and sharp, a bat bite might not bleed and might not leave a very noticeable mark on human skin.

QUESTION: Is bat guano harmful to my family?

ANSWER: Histoplasmosis is a respiratory disease caused by a fungus that grows in soil enriched by animal droppings, including those from bats. Ninety percent of all reported cases in humans come from the Ohio and Mississippi River valleys and adjacent areas where warm, humid conditions favor fungal growth. The disease is rare or nonexistent in most of Canada and in the far northern and western United States. The majority of cases are asymptomatic or involve flu-like symptoms, though some individuals, primarily those who are immune-compromised, become seriously ill, especially if exposed to large quantities of spore-laden dust. To be safe, avoid breathing dust in areas where there are animal droppings; if you must clean an area of bat or bird droppings, wear a respirator that can guard against particles as small as two microns.

The U.S. Centers for Disease Control and Prevention provides information about Histoplasmosis here.

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