Bats are furred, warm-blooded mammals with body lengths of 3 to 6 inches andwingspans ranging from 8 to 16 inches. They are the only mammals that actually fly. They also have a highly developed echolocation system which allows them to capture flying insects at night. They usually forage from about an hour after sunset to about an hour before sunrise, stopping to rest occasionally under open porches, eaves, trees or other overhanging structures. The most common Northeastern bat species in Rhode Island are little brown, big brown, red, and Eastern pipistrelle. Bats are beneficial because they eat large numbers of insects.
Bats live in a variety of habitats, including wetlands, fields, forests, cities, suburbs, and agricultural areas. Rhode Island’s bats are insect eaters. They usually feed in areas where insects swarm, such as over water and agricultural fields, in forest clearings, along forest edges, and around street lights. Bats are mostly nocturnal and almost always feed “on the wing.”
Bats spend their days roosting, often in the attic or walls of occupied dwellings, posing problems for property owners. Most colonies of bats go unnoticed, but they may become a nuisance due to their vocalization and activity, or odors and stains from urine, feces and rejected food. Many residents wish to eliminate these winged mammals because they can infect humans or pets with rabies.
Rabies is a viral infection of mammals that attacks the central nervous system. It is a deadly disease most often seen among wild animals such as raccoons, skunks, foxes and bats. Bats rank third in number of rabies cases in the United States, behind raccoons and skunks; only less than 1 percent of Northeastern bats are rabid. Symptoms of rabid bats include erratic flight, activity during the daytime, and weakness or paralysis causing the bat to fall from its roost. The rabies virus is found in the saliva of an infected bat. Most human exposure to rabies occurs when people attempt to help grounded bats. If sick or dead bats are found, local public health agencies should be contacted immediately. Bats should never be handled without wearing gloves.
Excluding bats from structures will be the most practical type of bat control. All bats should be outside the building before the entrance points are sealed. Batproofing should be attempted as soon as an unwanted colony is detected, except during early summer when young flightless individuals may be present. No pesticides are currently registered for lethal control of bats in the United States. Chemical controls may actually increase bat rabies risks by producing sick individuals, or by driving bats from attics into living areas. Application of pesticides may pose human health risks because fumes or powders move to occupied floors of the building.
Main access points to structures are found by observing the animals leaving the building at dusk. Bats may enter an opening as small as 1/4 x 1-1/2 inches. Cracks or crevices can be sealed with caulking compound. Larger openings can be covered with metal flashing or 1/4-inch mesh hardware wire. One primary hole should be kept open until bats exit for the evening, and then it can be temporarily closed with a wad of aluminum foil. Trapped animals will leave the following evening if the seal is removed at the normal exit time. After checking for remaining individuals, the opening can be permanently sealed. Trapped bats will soon die creating foul odors. Bats will seek other entry points, so the building should be checked each evening for several days.
Colonies in horizontal moldings or behind shutters will be discouraged by removing the shutters or opening the molding so there are no dark recesses. Shutters can be reattached to the home with 1- to 2-inch wooden block spacers. Installation of lighting in roost areas will also discourage bats (install wires properly to avoid fire hazards). The lights should be left on 24 hours a day for several weeks. Increasing ventilation to lower temperatures may cause bats to leave in some cases.
Mothballs may repel colonies in confined areas with poor ventilation. Recommended application rates are usually high, and vapors could reach living areas posing a health hazard to humans. Ultrasonic devices have not effectively repelled bats.
Once bats are removed from a dwelling, any caked fecal material or crystallized urine should be removedfrom flooring or beams. The odor of bat excrement may act as a pheromone and attract other bats. The fungus Histoplasma capsulatum can be contracted by breathing spores in the dust of bat feces, so respirators and protective clothing should be worn while working in bat roosts. All contaminated insulation should also be discarded. Surfaces contaminated with urine or feces can be disinfected by spraying with a solution of 1 part bleach to 20 parts tap water. Deodorants can then be applied to mask any remaining odors.
Individual bats occasionally enter houses, most often during summer evenings in mid-July and August.
These wayward bats are usually pups that are just beginning to fly. Fortunately, these incidents can be dealt with quite easily. A bat flying in the house will usually circle a room several times in search of an exit. The best method for getting a bat out of the house is to allow it to find its own way out. Chasing or swatting at the bat will cause it to panic and fly erratically around the room, which needlessly prolongs the incident. If you are certain that no person or pet has had direct contact with the bat, it can be released outdoors, away from populated areas, preferably after dark. To remove a bat from a living area, try to confine it in one room, open windows, turn off the lights and allow the bat to leave on its own.
Adapted from: Paul D. Curtis, Department of Natural Resources, Cornell University, 2001; Rhode Island Department of Environmental Management
Bat Conservation International
RI Department of Health
Centers for Disease Control and Prevention, National Center for Infectious Diseases Rabies Section
RI Department of Environmental Management