Bats can be humanely evicted from buildings

With bats leaving their summer roosts to return to their winter hibernation sites, Wisconsinites are reminded that fall is a good time to safely, and humanely, evict bats from homes and buildings. Now through May 31, before the nursing and baby bat protection period begins, bats can be kept out of homes and buildings by following best practices.

The DNR provides do-it-yourself instructions and information on hiring a professional to get bats out of buildings humanely, through a process called exclusion. Exclusion includes sealing a building, except for primary exits, outfitted with one-way doors that let bats exit and prevent reentry.

“While the goal of the DNR’s bat program is to protect bats and bat habitat, we understand that bats don’t need to share living spaces with humans,” said Heather Kaarakka, DNR Conservation Biologist.

Exclusions are prohibited June 1 through Aug. 15, each year, to protect Wisconsin’s little brown and big brown bats during their maternity seasons. Exclusions occurring during this period will separate mothers from their flightless pups, leaving the pups to die of starvation and potentially exacerbating the homeowners’ bat problem, as frantic bat mothers search for an opening to reach their pups.

Effective exclusion efforts should target time periods in the fall and spring, where temperatures are consistently above 50°F, as bats are generally active at temperatures above that level.

To permanently and humanely evict bats from structures, one-way venting devices should be installed at the primary entries/exits for seven to 10 days, in addition to sealing up secondary holes, cracks and crevices that may allow entry into a structure. Primary entries should be closed after a one-way venting device has been in place for the seven to 10 days, and bats are out of the building.

Little brown bats and big brown bats, along with northern long-eared bats and eastern pipistrelles (also known as tricolored bats), are all threatened species in Wisconsin, and receive legal protection, including the ban on exclusions during maternity seasons. These four bat species hibernate in caves and mines in the winter, and have been decimated by the deadly bat disease white-nose syndrome.

White-nose syndrome does not affect humans, but causes a fungus to grow on bats’ noses and skin, disrupting normal hibernation patterns and burning up the energy needed to get them through long Wisconsin winters.

Although bat roosts are protected during the maternity period, exclusions may be completed if the landowner feels the bats pose a health or safety risk to humans, and a health exemption form is submitted. Exclusions are allowed during the maternity season in hospitals, medical clinics, daycare centers, nursing homes, assisted living facilities and restaurants, without a health exemption form.

Bats can reduce pesky mosquitoes and night-flying insects around the home, and garden. Help keep these valuable mammals in the area, by building a house for roosting and to raise their young.

Late winter/early spring is a good time to provide an alternative roost – a bat house – in the general vicinity of where bats enter the building.

A single bat can eat up to 1,000 mosquito-sized insects an hour, and the equivalent of its bodyweight every night. University of Wisconsin-Madison research analyzing bat guano (manure) collected at sites across Wisconsin, confirms that bats consumed 17 distinct types of mosquitoes, including nine species known to carry West Nile virus.

For more information, visit dnr.wisconsin.gov.