Bats roosting in a building often go unnoticed for years. If they are not causing damage to the building then no action need be taken. You may hear sounds from bats vocalizing or crawling around. Bats make the most noise on hot days and when leaving the roost at dusk or returning at dawn. Bat droppings, called guano, may be found on the attic floor or can stain the ceiling or siding.

Bats can squeeze through cracks as small as inch wide. They may enter through openings found around a chimney, attic, vent or siding. To locate exit/entry points watch from the corner of the building and look for bats flying in and out. Begin the watch 30 minutes before dusk and observe for 1 hour.

Its best to evict bats by allowing them to leave on their own and then denying entry. Seal all but the largest or most used entrance with building material (hardware cloth, netting or sheet metal).

One Way Bat Netting

The last entrance should be covered with garden netting. Hang it over the entry point so it extends 2 feet below and to each side of the opening. Only the bottom edge should hang loosely. This allows bats leaving the building to crawl under and out, but returning bats cannot find their way back in. Secure the net in place so that it hangs free an inch or so away from the building. It will act as a one-way valvepermitting exit, but closing when bats land on it to return. Leave the netting up for several days before sealing the opening, as some bats will not leave to feed at night. Inspect the attic to see that bats have left or watch the outside of the house at dusk.

Never attempt to exclude bats between the months of May and August since there may be young present. A mother bat will be unrelenting when seeking a way back to her baby. And young bats may find their way into living space looking for their mother, or create an odor after they die. By September, young bats are flying and able to live on their own, so fall is the best time to evict bats.

There are methods you can use to make the roosting area undesirable:

• Lower the temperature in the attic by creating an air draft. Use fans or add wall and roof vents.
• String floodlights in the attic to illuminate the roosting area.
• Bats can live to be 30 years old, and the colony will attempt to return to their traditional roost. Installing a bat house will increase your success rates in keeping bats out of your house and reduce the local mosquito population.

Trapping is not recommended since excluding bats is less complicated to carry out, less time consuming, more effective and requires no handling of bats.

Never attempt to poison bats! Poison is not effective because many of our bats are insectivorous and bats often roost deep in cracks where the poison wont reach. Poisoned bats will leave the house sick, and are then more likely to bite pets or people.

A lone bat found in the living space can be easily removed. Confine it to one room, open a window or door leading outside, turn off the lights, and leave for 30 minutes to 1 hour. You can also wait until the bat stops flying, cover it with a coffee can or jar, and slide a piece of cardboard underneath the jar. Take the captive bat outside and release it after dark. Always wear leather work gloves when handling a bat. In some communities, your local humane society, animal shelter or animal control officer can assist you with removal of single bats from your home.