Timing for Excluding Bats

We have a group of bats living in our attic and would like to bat proof the house but don’t want to seal bats in. What is the best time for excluding bats?
Timing for Excluding Bats - Articles

Updated: August 8, 2017

Timing for Excluding Bats

It sounds like you probably have a maternity colony in your attic where female bats gather and raise their young. Bats are generally very site faithful and the same breeding location will be used year after year. The best time for bat-proofing is in the early spring, before bats enter the roost, or in the fall, after the bats have left. Bats generally enter the roost in late April or early May and young are born in late May or early June. Young bats (pups) will be flightless until around mid-July so you want to avoid any bat proofing between May-July when you risk sealing bats in. If bat-proofing must be done while bats are inhabiting the building, it should be done by installing a one-way door after the pups are able to fly. One-way doors, are designed to allow bats to leave and not reenter a building. For more information on bat proofing and one way doorssee, the Penn State Extension Wildlife website.

Timing of Bat-proofing

  • January-April: Seal entrances before bats return to the building.
  • May-August: Watch bats to identify entrances. Do not seal openings.
  • August-October: Install one way door(s).
  • November-December: Seal entrances once bats have left the building.


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