Resource Library

Managing the Real Risks of Bats in Buildings

Date: September 2018

Bats are a common sight around Minnesota; however, many people view them with fear or as pests to be eliminated. These attitudes often do not accurately reflect the actual severity of risks bats pose to human health or property. MCIT has had few claims from injuries or negative health effects related to bats. Unfortunately, some common responses to bats may lead to problems greater than the actual risks of bats.

4 Protected, of Concern Species in Minnesota

Nationally and in Minnesota, many bat populations have been in decline. This has prompted federal and state agencies to declare some Minnesota bat species as threatened or of special concern. According to the Minnesota Department of Natural Resources, seven bat species are known to inhabit the state, and four of them are listed as threatened or of special concern on state or federal endangered species lists.

Penalties for killing a threatened species on the federal endangered species list could receive $25,000 and six months in prison, depending on the intent to kill. In addition to these criminal penalties, civil penalties of up to $23,744 may also apply. Such penalties would not be covered by MCIT.

Furthermore, killing a threatened or special concern species may damage an organization’s reputation if environmental groups and advocates bring media attention to the situation. With these severe penalties and risks, it makes sense for members to make controlling bats without killing them a high priority.

Old Courthouses, Buildings Are Ideal Homes for Bats

Many county courthouses are ideal bat roosts or winter hibernation sites, as brick buildings with large attics are favored. Cracks or holes in eaves or masonry as small as a dime can allow bats to inhabit the space. Bats do not chew their way into buildings but use pre-existing cracks or openings. For this reason, members may want to inspect aging or historic buildings for cracks and holes and seal them.

Sealing holes in buildings can also have a positive effect on energy efficiency, help prevent water infiltration and inhibit birds and insects from building nests.

Careful Removal of Bats Is Key

There are several bat control methods. The best technique to use may depend on where the bats are relative to where people are in the building.

If bats are already in the building where people do not typically go, such as attics, belfries and steeples, members can try methods to exclude bats. Often members use a bat exclusion company to handle this.

Exclusion typically involves the installation of one-way gates that allow bats to leave but not re-enter the location. In addition to the gates, any other entry points are identified and patched.

When pursuing this option, it is important to consider the time of year and the bat lifecycle. In spring and summer, many bat species give birth, and the babies are unable to fly. Excluding bats in the spring or summer could inadvertently kill the young, as their parents would not be able to feed and care for them once leaving the roost.

In cases where a bat enters a space where employees or the public are present, the bat should be actively removed from the property. In these situations, the best approach would be to isolate the bat into a room and open a window to let it escape.

Another option is to capture the bat and either release it outside or submit the bat for testing (see below). When capturing a bat, always use leather or other thick protective gloves.

To best capture a bat, approach it slowly and place a container over the bat. Slide the lid or a piece of cardboard underneath the container and flip the container over, trapping the bat. Secure the lid with tape.

Ideally the bat should be held in a container with a lid, as bats can chew through fabric, such as towels, nets and blankets.

Rabies Responsibilities, Other Hazards Caused by Presence of Bats

Though extremely rare, bats may carry rabies. Rabies is a viral disease most often transmitted through the bite of a rabid animal that ultimately leads to death if not treated.

Only 3 percent to 4 percent of bats sent for testing are found to have rabies. In fact, according to the National Weather Service and Centers for Disease Control and Prevention the odds of being fatally struck by lightning are almost 10 times greater than dying from rabies contracted from any animal.

Despite the rarity of rabies, a bat should be tested for rabies if it:

  • bit someone.
  • had physical contact with people prior to capture.
  • was found on the ground or appears sick.
  • was found with children or others who cannot reliably communicate.

If tests reveal that the bat carried rabies, a rabies post-exposure prophylaxis (PEP) should be administered. If the bat is not available for testing, a PEP should be given if physical contact occurred or may have occurred.

Another hazard can be created by significant accumulations of bat droppings, known as guano, in an attic, steeple or roost for example. When disturbed, bat droppings can cause fungal spores to become airborne, which if inhaled, have been linked to adverse respiratory conditions.

People removing droppings should be equipped with appropriate respirators and a written respiratory safety program instated to ensure proper fit, use and storage of the equipment. Members may want to hire an outside service to clean the guano given these requirements. Many bat exclusion companies also offer this service.

Safety and Risk Management Recommendations

Although many people view bats as pests, the reactions to bats are often disproportional to the risks bats present. MCIT recommends the following when controlling associated risks of bats.

  • As multiple bat species are protected by federal or state laws, members should protect the bat while controlling or removing it, not kill it.
  • Members should seek to exclude bats from structures, following the measures discussed above.
  • Health hazards from bats, such as rabies are rare but serious. These risks can be controlled with the use of personal protective equipment, testing and vaccines.

Further information about bats, including the protected species, and bat exclusion, removal and testing can be found at the websites for the Minnesota Department of Natural Resources (DNR.state.mn.us) and Minnesota Department of Health (Health.state.mn.us).

MCIT coverage for bat-related incidents is fact specific. Members can contact their risk management consultant with questions at 1.866.547.6516.

By following careful risk management and safety measures, bats and their associated risks can be controlled in a safe and humane way.


Benefits of Bats

Bats fill an important ecological niche and help make Minnesota more livable. All seven of the bat species in Minnesota consume insects for food. On average, a bat eats about half of its body weight in insects each night. For example, the most common bat in Minnesota, the little brown bat, can eat approximately 600 mosquitoes every hour.

Many of the insects bats eat would otherwise go on to damage crops or bite people. Often this is the reason cited when people encourage bats to roost nearby through installing special bat houses.


Originally published as “Bats, Courthouses and People: Separating Facts from Fears” in December 2016 MCIT Bulletin

The information contained in this document is intended for general information purposes only and does not constitute legal or coverage advice on any specific matter.