Most complaints regarding unwanted "house bats" are based solely on ungrounded fears. The primary problem is misinformation, not bats. Nevertheless, bats can occasionally become a nuisance when too many roost in the wrong place, and BCI members are certain to be called upon for solutions. Here are some helpful hints.
Harmless repellent devices would seem ideal. Nevertheless, none are known to be effective. The U.S. Environmental Protection Agency recently assessed a fine of $450,000 against a Chicago manufacturer for marketing one of these worthless products. All brands thus far tested by reliable bat experts have proven ineffective, and some may endanger people.
Naphthalene flakes(moth balls)are hardly any better. Their primary usefulness is in generating repeat business for the pest control industry. To be effective, they must evaporate rapidly, requiring frequent replacement. Aerosol dog and cat repellents can discourage bat use of a particular roosting spot for periods of up to several months. They, of course, never should be applied while bats are present.
The only safe, permanent solution is exclusion. Occasional bat wanderers in human living quarters can be excluded by covering chimneys and vents with hardware cloth screens, by installing draft guards beneath appropriate doors, and by sealing any other possible access routes, especially around windows and plumbing.
If a bat colony must be evicted from a wall or attic, careful observations should be made at dusk to find its entry holes. Scattered droppings beneath such places may provide additional clues. Once found, bat entry holes can be plugged while the bats are out feeding or during their winter absence. Nursery colonies should not be evicted while flightless young are present (usually June or July in the U.S.). Poisons used against such bats are costly, ineffective and often create problems far worse than those they are supposed to solve (see Bats and Public Health, "Hazards of Mismanagement," available from BCI).
(Editor's Note: One BCI member, Susan Barnard, in Atlanta, provides free consultation to local pest control companies, offering safe alternatives to extermination. Other BCI members may wish to follow her example. There are honest companies who need and appreciate such assistance.)