What should I do?
Due to the small size of bats they are able to gain entry to an attic through a hole as small as a half-inch. This can make it difficult to find all possible entry/exit sites used by the bat(s), but it is important to investigate thoroughly and find all the access points if possible. Firstly, conduct a “bat watch.” Go outside about 30 minutes before dusk and watch for bats leaving the attic. Watch closely untill about 30 minutes after dusk. Once you have spotted the entry/exit hole(s) you may begin steps to exclude the bats from your attic. However, do not begin exclusion during the months of May to August, or you may trap young inside that will die.
The best time to exclude bats is the fall when they are looking for other roosting sites for hibernating. Install one-way doors over the entry/exit holes. This allows bats to leave the attic but not return. You can also try placing netting over the hole that extends 18 to 24 centimeters from the entry/exit hole. Secure the top and sides of the net but leave the bottom open. This system will allow the bats to exit the attic, but will prevent them from re-entering. Leave the netting and one-way doors in place for several days, then check the attic for signs of bats and conduct another “bat watch.” When you are certain there are no more bats remaining in the attic you can permanently seal the entry/exit holes.