Being nocturnal creatures, bats spend the daytime hours roosting in dark attics or walls. At night, swarms of bats take flight and leave their hiding places. While this makes great film footage when the bats alight from beneath a church steeple, it is much less picturesque if the swarm originates from a spot under the eaves of your roof. Batproof your home to keep out any bats and prevent those you currently host from returning.
Know the likelihood: Nearby bodies of water are risk factors for a bat infestation
Location, location, location is not just the mantra of realtors; it is also the method of site selection for bats in search of a roost. If your home is located near a stream or lake that supports a large quantity of insect life, Purdue University experts warn that you are at a greater risk of encountering bats in the attic. If you have not already done so, take the steps needed to batproof your home.
Inspect the attic: From the outside (for a summer roost)
Just before dusk, go outside and see if any bats emerge from your attic. Place a friend or family member on the opposite side of your home to look for emerging bats there. If no bats come out to feed, you may not have bats in the attic yet and should proceed with batproofing. Another telltale sign of a bat entry or exit hole is staining around the opening, the University of Florida notes. Made up of body oil and feces, the stain points to a frequently used opening. If bats do leave your home, try to size the colony. It may be as small as a few dozen bats or as large as about 200 animals.
Inspect the attic: From the inside (for a winter roost)
When bats hibernate, they will not fly out to search for food. Climb into the attic and shine a strong flashlight into the darkest corners. Inspect the floor for droppings. If you hear chirping during the day, the odds are good that you have some chimney swifts nearby. Bats usually do not vocalize during the day, making it is possible for a homeowner to never notice an entire colony of attic-dwelling bats, the experts from the University of Rhode Island Landscape Horticulture Program explain.
Time batproofing efforts just right
If your inspection shows that you are dealing with a summer roost, let the animals finish rearing their young. The colony usually departs in the late fall in search of a hibernation locale. If your home is being used as a winter roost, wait until early spring when the animals leave in search of a maternity roost. Do not try to evict a colony between May and August, when the animals are rearing their young. Even if you are successful in getting rid of the adults, you will be left with dying juvenile bats that create a serious odor problem.
Search for points of entry
Relying on the authority of the Bell Museum of Natural History, the University of Minnesota notes that an opening as wide as one-quarter of an inch is sufficient to allow access to your attic. The urban wildlife specialist quoted by Clemson University puts the possible size of an entry hole as measuring roughly three-eighths of an inch by seven-eighths of an inch. Inspect the roofline, attic vents, and siding for holes and cracks of this size. It is a good idea to enter the attic on a bright day and look for light entering the space. These are the entry points likely used by bats.
Seal the points of entry
Sheet metal is a good material to keep out bats. If you are looking for a temporary fix, bar access with the help of steel wool. Another option is the use of window screening to cover louvered vents, the experts at the Penn State College of Agricultural Sciences note. Do not forget to also cap your chimney and any vents.