Northern Prairie Wildlife Research Center
Bats should be out of the building before batproofing begins. The best time for batproofing is in the fall after the young bats have learned to fly and before the advent of cold weather. The time of day is also important so that holes can be blocked in the early evening after the bats have departed to feed. Most bats start to leave a building about 15 min after sunset; however, some species of bats leave their roosts later than others, some when it is dark.