Management of Much Maligned, Often Misunderstood Bats
By Marcia Anderson
During summer evenings in Maine, I often sit outside and watch the bats flying to and fro, devouring insects near the edge of a lake. Bats have a reputation for being spooky or even dangerous, but they are some of the most beneficial animals to people. Bats are misunderstood and needlessly feared. Bats actually do humans a great service, as each one can consume hundreds of crop-destroying insects and other pests every night.
Bats do not encounter people by choice and very few bats consume blood. Of the more than 1,100 bat species worldwide, only three feed on blood and none of those live in the United States.
New England is home to many species of bats including the big brown, little brown, red, hoary, 
Eastern small-footed myotis, and Indiana bat. A single little brown bat can eat 3,000 mosquito-sized insects a night. Most North American bats have small teeth for eating insects including corn earworms, cucumber beetles, leafhoppers, stink bugs, mosquitoes, moths, termites, ants and cockroaches.
Bats are essential to maintaining healthy ecosystems and economies, yet their populations are declining worldwide from habitat loss and disease. Some bats are primary pollinators for fruits and other produce and help disperse seeds of plants that restore forests. Bats prefer roosting near open bodies of water, parks and fields where they can catch the most insects during their nighttime forays.
During the day, bats prefer to roost in tight crevices such as cracks in rocks, and in awnings of buildings where they are protected from predators. They may also roost in attics, soffits, louvers, chimneys and porches; under siding, eaves, roof tiles or shingles; and behind shutters. Still, bats need to be treated with respect and care if they enter a house. Usually they enter through an open door or window, but can fit through openings as small as one-half inch in diameter. Without doubt, the bat’s primary goal is to escape back outside.
If you encounter a bat, don’t panic. Bats are rarely aggressive, even if they’re being chased, but they 
may bite in self-defense if handled. It is true that bats can carry rabies and should never be touched with bare hands.
If bats begin to roost in your attic or somewhere you don’t want them, your best bet to solve this problem is with is integrated pest management. First, do not simply wait for bats to fly out at night. Not all bats leave the roost at the same time and some may stay inside for the night, especially the young. To properly seal holes, you can use caulking, flashing, screening or heavy-duty mesh. Ask a professional the best way to evict the roosting bats. Often the answer is a one-way door. In any event, get rid of your bats before mid-May or after mid-September to avoid trapping young.
Every state has unique laws related to bat protection, and it may be illegal for anyone, including animal control officers and exterminators, to kill certain bat species. No pesticides are licensed for use against bats and it is a violation of federal law to use a pesticide in a way not described on the label.
When you decide to get rid of bats you should provide a near-by shelter, such as a bat house. Install the bat house a few weeks before you eliminate their indoor roost, to allow the bats time to find the new shelter. Trees are generally not good places for bat houses since they are accessible to bat predators like raccoons and cats. However, if you do use a tree, add a metal protector guard. A pole mount in a garden or field is the preferred bat house location.
Community bat houses can be educational. Families, like ours, can sit outside at sunset and watch the bats on their nightly fly-out. It seems that there really were fewer mosquitoes this past summer, perhaps because of the presence of more bats.
More information on bats from the Smithsonian Institution (http://www.si.edu/Encyclopedia_SI/nmnh/batfacts.htm)
More information on Integrated Pest Management: http://www.epa.gov/managing-pests-schools/introduction-integrated-pest-management
More information on Safe methods of pest control: http://www.epa.gov/safepestcontrol
Marcia Anderson, who has a doctorate in environmental management, works with EPA’s headquarters on issues related to pest management in schools. She formerly worked in pesticides for EPA Region 2 and has a home in Lyman, Maine.
Management of Much Maligned, Often Misunderstood Bats
Source: EPA Water Science news