How to safely exclude bats
Are you wondering what to do with an infestation of bats in your house? You don't want to injure them, but you don't want to let them live with you either. What should you do?
The best way to remove bats from a crevice during spring, summer, and fall is to exclude them with netting, as shown in the adjacent photo where bats are coming out of a hole and moving through the netting to get out and then fly away. After they get out, they cannot get back in because they have wings, not hands, and cannot pick up the netting to get back in. Do not exclude bats from June until September, when bats are having babies. Bat babies (called pups) cannot fly and would die without their mothers to take care of them.
Steps to safely exclude bats
1) Look for guano (bat excrement that looks like mouse droppings) around your house walls that'll help identify where the colony is roosting. You can also sometimes hear the bats; they'll chatter when disturbed or when they're about exit their roost in the evening. Bats also have a strong ammonia-like smell from urinating and defecating when entering and exiting roosts.
2) In the evening, just as it's getting dark, watch where the bats are coming out. The next day, before the bats come out, tape netting over the hole, and drape the netting over the hole about 12-inches. Make sure it's not too tight and that the bats can climb out. Can you slip your fingers under the netting as you're tacking it down? If so, that'll work; the bats will be able to scramble out. What you're making is a one way 'pet door'. Also, make sure to use material that's see-through, like bridal veil material or bird netting. Bats rely on sight to see light to find their way out of dark areas (blind as a bat is a myth). If you place a dark cloth over the hole, they won't know where or how to get out.
3) The next day, watch in the evening to see if the bats are still coming out. You might have to adjust the netting if they're still getting back into the hole. You also don't want to seal them in. Also, bats only come out when it's a nice, warm evening; if it's cold or rainy with no bugs to eat, they'll stay indoors (not all that different from us)!
4) After a week to 10 days, when you're sure that the bats are all out (you can't smell, hear, or see signs of them like their guano), you can remove the netting and seal up the entrance with blocks of wood, foam, netting, or steel wool.
Excluding bats is the safe way to remove bats without coming in contact with them. It's safe for you and bats too. Licensed pest control operators are also available to exclude bats and are familiar with safe exclusion practices that protect bats.
Bats are good! Let's help them out! You might want to put up a bat house for bats if you exclude them so they have a home to go to. See the 'bat box' section.