Bats in Southwest Florida

Question: We have bats that have lived in our house for years, but they are now coming inside. What can we do?

Answer: There are 17 species of bats found in Florida. Bats generally live near water and roost in dark areas during the day. Bats are an essential link in the balance of nature. Bats consume mosquitoes and other night flying insects, and pose little health risk to humans. Bats are most frequently seen on warm nights feeding over water bodies, around buildings or forest edges, or around lights.

The presence of a bat in the home is a sign that the house is not weather-tight. The best way to remove a bat from the home is to isolate the bat in one room and simply open a window. The bat will eventually detect the open window (within a few minutes) and fly out on its own. If possible, stay in the room with the lights on until the bat leaves. Another method is to use leather gloves and pick the bat up. Do not use bare hands because the bat may bite trying to protect itself. You can also trap a bat under a coffee can and slip cardboard under it to capture the bat in the can and take it outdoors.

One or two bats in the home may be a sign that a colony has established a roost in a crawl space or attic. The attic is the most common area for bats to live, and if they become a nuisance, the only long-term solution is to "bat proof" the building. Since bats play such an important role, non-lethal methods of control are recommended. The use of pesticides for the purpose of controlling bats is illegal.

Several methods of controlling bats include exclusion, artificial light, repellents, fumigants, and ultrasonics. Exclusion is the method to use for permanent control. Discovering the entryways is the most important step. Bats nurse young from April through July, so exclusion at this time is not recommended since the odor from dead bats is extremely offensive and may attract more bats. Seal off all entrances except for the main one and remember that a crack only 3/8 inches wide will allow bats to enter. Install a one-way door over the primary entrance and after four nights; monitor the opening from 30 minutes before sunset to 30 minutes after sunset. If bats are no longer seen leaving the building, seal the remaining hole. If you have sealed all of the holes, there will be no further problems.

Manipulating light has been used to remove bats since they prefer dark spaces. This method can be successful, but only if the light is kept on continuously and moved around frequently to prevent the bats from moving to deeper, secluded corners in the house. This solution is temporary. Repellents are another temporary solution. Mothballs can deter bats, but only as long as there is a strong odor. Ammonia can be used to clean infested areas and then pans of the solution put into roosting areas to act as a repellent. These repellent solutions may be intolerable to humans since the treatment will have to be continuously repeated. Fumigants can only be considered for control in a public health emergency under special permit, and only after all other feasible methods of exclusion have failed. Ultrasonic repellents are ineffective and may actually attract bats.

It may be helpful to provide alternative shelter. It is easy to build or buy a bat house and install it in your yard. It may take some time for the bats to use these houses, but it can help deter them from your home. Call me for instructions on building your own bat house.

Shannon L. Ruby is the Natural Resources/Agriculture Agent with the University of Florida/IFAS and Lee County Extension Service. To submit questions, call 461-7515 between 9am and 4pm or send questions to 3406 Palm Beach Blvd. Fort Myers, FL 33916-3736 or via e-mail at rubys@leegov.com.