An undeserving reputation has surrounded Midwestern bats thanks to their tropical cousins that feed on the blood of livestock and wildlife. Of course, the bats of Minnesota and Wisconsin don't share that trait, but that doesn't mean the average person enjoys their company.
Bat species found in Minnesota and Wisconsin are quite small, weighing between one-fifth of an ounce to a little over 1 ounce, according to the Minnesota Department of Natural Resources. However, that small size is an indication of how easily a bat can enter your home. Bats can enter through holes as small as 3/8-inch or spaces 3/8-by-7/8 inch. The tell-tale signs of bats roosting in your house include scratching and squeaking noises coming from walls and ceilings or seeing bats enter and leave your home at dusk.
Getting rid of a colony once it has made a permanent roosting site in your attic is not as simple as it sounds either, especially if there are many bats taking up residence. Whether taking on the project of bat removal on your own or hiring a pest removal company, the only consistently successful method is physical exclusion.
Exclusion comes with a caveat though — if a colony has taken up residence, exclusion can only happen between late August and March to ensure the young bats are able to fly. Any attempts during summer months will mean flightless bats will starve to death and likely cause an odor problem. With temperatures around the area dropping, now is the time to start removing a colony from local buildings.
Safely removing a colony
The first step to bat proofing is to make sure access points to attics and basements are sealed and any holes in walls or ceilings are repaired so that bats can't accidently enter the primary areas of your house. Next, you will need to locate where the bats are actually entering the building. Typical entrances include chimneys, louver fans, air intakes, exhaust vents, openings around plumbing, power or cable lines, spaces around doors and windows, and where exterior siding has shrunk, warped or loosened. Stains on ceilings or walls from the accumulation of bat droppings are often an indication of entrance points as well. Bat droppings can be distinguished from those of other animals in that they easily break apart and contain many small shiny insect parts. Close inspection during the day will help determine the exact location of the entry points.
After all of the entry points have been located, seal all but one up. With the final entry point, create a one-way escape for the bats. Once it has been determined that all bats have left their roosting place, the final entry point can be sealed up.
Attempts to poison bats, or exclude them using inappropriate methods can actually increase human contact, as sick or homeless bats may disperse through the neighborhood thereby increasing chance encounters with people or pets. Be wary of any pest control company that suggests the use of ultrasonic devices or toxic chemicals. There are no chemicals registered in Minnesota for use on bats.
Finally, after the bats have safely and permanently been removed, it is a good idea to clean up any bat droppings. The primary reason for this is histoplasmosis — a disease associated with some bat colonies. The disease is caused by inhalation of spores or fragments of the soil fungus found in bat droppings. Human infections occur through breathing dust that contains the spores. Some infections produce flu-like symptoms, but many infections in humans produce no symptoms or distress.
Benefits of bats
Bats in your attic shouldn't be ignored and the removal of a colony should be done immediately, however, bats in your neighborhood are likely to cause more good than harm. Bats feed mostly on flying insects, including beetles, moths and mosquitoes which they catch in their cupped tail membranes. Once an insect is caught, the bat transfers prey to its mouth while in flight. While chasing insects, bats often fly erratically. This has led some people to mistakenly believe they are being attacked by the bat. Actually, bats are proficient flyers and can easily catch insects while avoiding people.
The enormous quantities of mosquitos and other insects that bats consume each year certainly make summers more bearable. So the next time you are camping and complain about getting bit by mosquitos, just remember how much worse it could be without bats.