Although people often aren't thrilled about sharing their living quarters with bats, bats make good neighbors. One little brown bat can eat 600 mosquitoes per hour, and big brown bats eat many agricultural pests. They're catching a lot more insects than that bug zapper you have out back. They also help us to reduce our use of insecticides. If you're not sure if bats are sharing your domain, San Julian suggests looking for bat droppings in your attic.
Bats leave dry, black droppings the size of rice grains, filled with shiny insect wings.
Because house bats have only one or two pups each year, protection of maternity colonies is important for their survival, says Brittingham. Destroying just one maternity colony can have a long-term impact on the populations of both bats and insects in a local area. First, look for areas in your attic where bats can get through, says Brittingham. Bats enter through spaces where joined materials have pulled away. They often get through louvered vents with loose screening, roof peaks, dormer windows or areas where flashing has pulled away from the roof or siding.