Living with Bats

Please note that 8 out of the 9 species of bats that occur in Connecticut are on the state's List of Endangered, Threatened, and Special Concern Species. Therefore, they are protected by the Connecticut Endangered Species Act. The only bat that is not a listed species is the big brown bat.

Bats hanging in a cave.

The presence of bats in buildings can be detected in several ways. At dusk, when bats leave roosts to feed, they may be seen exiting through eaves, vents, or from behind shutters or siding. Noise from large colonies may also announce their presence. Droppings and dark brown stains may appear near eaves and beneath entrance holes and roosts. Bat droppings (guano) are easily crushed, revealing shiny bits of undigested insects. Droppings are never white or chalky in appearance, like the droppings of birds.

The 2 most common bats involved in human/bat conflicts are the little brown bat and big brown bat. The little brown bat ranges from 3.1 to 3.7 inches in length and has a wingspan of 8.6 to 10.5 inches. Big brown bats range from 4.1 to 4.8 inches in length, with a wingspan of 12.1 to 12.9 inches. Big brown bats can readily be distinguished from little brown bats in flight by their larger size, slow wingbeats, and audible chatter.

Removing a single bat

A bat that enters a home can often be removed easily. Closing off doorways to the room containing the bat and opening a window will usually prompt the bat to fly outside. A large jar or cardboard box may also be used to remove a bat. Move toward the bat slowly so that it is not startled and gently place the can over it. Slide stiff paper or cardboard under the opening, using it as a lid when removing the bat. Wear heavy leather gloves when removing a bat by hand. Bats, like all wild animals, may bite when handled and should not be removed bare-handed. Remember that bats, like other mammals, may carry rabies. If a mammal is infected, the rabies virus is found in saliva and may be transmitted through the a bite. If you are accidentally bitten while handling a bat, make sure the bat is saved for examination. Immediately wash the bite with soap and water and seek prompt medical advice. Non-bite exposures can also occur and should be treated in the same manner as a bite. A non-bite exposure occurs when saliva or brain tissue from an infected mammal enters scratches, abrasions, open wounds, or mucous membranes (nose, mouth, eyes).

Dealing with a bat colony

Most colonies of bats are small and can remain unnoticed for years without causing any issues for a homeowner. Large colonies residing in an attic or wall may become a conflict because of noise or undesired guano accumulations. Eviction and exclusion of roosting bats are the only safe, permanent solutions to a conflict.

Exclusion and bat-proofing

One of the simplest techniques for solving human/bat conflicts is letting the bats exit on their own and then preventing their re-entry to the roost. Little brown bats do not spend the winter in buildings, so bat-proofing can be done after they travel to their winter roost site. Big brown bats usually travel to other roosts also, but they have been known to use buildings as winter roosts. If conflicts involve big brown bats or if rapid exclusion is necessary, the first step is to find the exit(s) by watching the bats emerge at dusk. Stains from body oils or droppings may help pinpoint exits.

Exclusion should NOT be done from June through mid-August as flightless young may be trapped and die in the roost. In addition to resulting in the suffering of bats, this would likely cause odor problems.

A simple one-way exclusion gate can be made using half-inch polypropylene structural-grade bird netting. During the day, hang the netting around the exits, using staples or duct tape. The netting should be attached several inches above the exits and extend at least 2 feet to either side and below the exit. The sides may be attached, but the bottom must hang free. As bats leave to feed, they will drop out of the roost unhindered. When they return, they will be unable to fly directly into the roost. These exclusion nets should be left in place for 3 or 4 nights to insure that no bats remain in the roost. After exclusion, the openings can be repaired when convenient. Caulk, fine screen, and oakum (petroleum-soaked rope) are all easy items to use for sealing openings.

Another simple one-way excluder can be made from plastic strips. In a section of flexible plastic, cut small strips (about 1-inch wide) that will serve as tiny door flaps. The bats can push past them to exit, but the strips will not flex inward to allow re-entry. This excluder should be installed in the same manner as the bird netting.

Exclusion of bats from Spanish or concrete tile roofs is often as simple as installing a rain gutter. The gutters should be installed flush against the attachment surface. The upper edge of the gutter should be even with the lower edge of the tile, extending outward about 8 inches. This exclusion can be done any time because the bats are still able to leave. Bats dislike climbing over the slippery metal gutter and usually will not return.

If you prefer to hire someone to exclude and bat-proof your home, it is best to seek a specialist. If the bats need to be trapped or handled, the specialist must be licensed by the DEEP Wildlife Division. (Information on hiring a Nuisance Wildlife Control Operator)

As with any business dealing, it is advisable to get more than one estimate for the job. Beware of scare tactics, and remember:

Bats do not multiply like rabbits. In fact, each female bat only has one young per year.
Even sick bats rarely attack people or pets.
Bats are not attracted in hordes by the scent of other bats.
Bats have very few parasites, so additional spraying for parasites is not necessary.
Permanent physical exclusion is essential for any bat control job.
The use of poisons to eliminate a bat colony is illegal without a special permit.
Bat guano is not "toxic".
Rabies rates in bat populations are not increasing.

Some additional considerations may improve the success of a bat exclusion. Female bats form maternity colonies in summer to raise their young collectively, benefitting from warmth of roost-mates and safety in numbers. A suitable roost is used by the same females year after year for generations. Each year, when the females return in spring, they are already pregnant and hungry after a long winter. They will be eager to return to their summer roost and begin foraging each night to nurture their developing young. Females that return to a sealed entrance may try to find other ways into the roost, including entering into the home, or may attempt to roost in another undesirable location. Providing bats with a suitable roost, such as a bat house nearby, may help reduce future conflicts. Mounting the bat house while the bats are still present and prior to undertaking the exclusion could further improve success. Keep in mind that having a bat colony nearby will help control insect pests and can be a fun wildlife watching experience for friends, family, and neighbors throughout the summer!

For more information on bats, contact: DEEP's Wildlife Diversity Program at deep.batprogram@ct.gov or 860-424-3011 and also Bat Conservation International.

For more information on rabies, contact your local health department.

Do you need additional help and advice concerning conflicts with wildlife? Check out wildlifehelp.org and select "Connecticut" as your state to get started. WildlifeHelp.org is supported by the Northeast Association of Fish and Wildlife Agencies and the Northeast Wildlife Damage Management Cooperative.

Content last updated in May 2026.