Northern Prairie Wildlife Research Center
If Constantine's valve-like batproofing device is not available, it will be necessary to resort to the less practical procedures for blocking and sealing apertures. All obvious accesses should be sealed except one or two of the principal openings. For several days, bat counts should be made as the holes are closed, leaving the main exit open. On the night of the final count when all the bats have left, rags, tissue paper, or cotton should be pushed firmly into the main hole to prevent reentry. Returning bats may cluster or flounder outside the plugged entrance. Early the following evening, the plugging should be removed so as to allow any further bats to escape before sealing the last hole. If any bats are seen within the structure, the routine must be repeated. The house should be watched for several evenings at dusk (and later, if necessary) to make certain that bats have not found an overlooked access.