Bat removal

Structural exclusion and animal removal are related but distinct. Structural exclusion addresses access or re-entry by securing openings and vulnerable structural features. Removal or eviction addresses animals already present. A complete solution may require both, subject to species, life-stage, seasonal, and legal constraints.

Eviction, venting, and exclusion are the methods for eliminating and preventing bats from residing in structures. Exclusion measures include one-way doors or check-valves, caulk, flashing, and screening. Excluded animals will be forced to go elsewhere, and the shift may be to another building nearby. Frightening is not effective, no toxicants are registered, shooting is not practical and is illegal in some states, and trapping is not recommended.

Active holes can be identified by rub marks, guano, and sometimes odor. Except for the actively used holes, all gaps of 1/4 x 1 1/2 inches and openings of 5/8 x 7/8 inches or greater should be sealed. It is tedious to locate all active and potential openings available to bats.

The discovery of rub marks, bat guano, and sightings of bats usually are sufficient to confirm the presence of bats. Rub marks may occur on surfaces along walls, under loose woodwork, between bricks, and around other bat entryways. These marks often have a smooth, polished appearance, are slightly sticky, may contain a few bat hairs, and are yellow-brown to blackish brown in color.

Bat droppings are segmented, elongated, and friable, becoming powdery when crushed and revealing shiny bits of undigested insect remains. Bats urinate and defecate when exiting a roost, causing multiple spotting and staining on sides of buildings, windows, patio furniture, automobiles, and objects near entry and exit holes or beneath roosts. Bat excrement produces an unpleasant, pungent, musty, acrid odor as it decomposes in attics, wall spaces, and other voids. This odor often can be detected from outside a building containing a large or long-term colony.

Bats commonly enter buildings through openings associated with the roof edge and valleys, eaves, the apex of the gable, chimneys, attic or roof vents, dormers, and siding. Other openings may be found under loose-fitting doors, around windows, and at gaps around conduits passing through walls and utility vents. Bats often roost on the outside of buildings, behind shutters, and where the siding and edge boards are not joined properly, lapped, or sealed. For bat management, attention is directed to any gap measuring approximately 1/4 x 3/4 inches or any hole measuring 5/8 inch wide. Smaller species can access an opening no wider than 3/8 inch.

Bat use of buildings varies by species and season. Female little brown bats form summer nursery colonies in attics, barns, and other warm retreats. Northern long-eared bats may also use attics and barns for nursery colonies. Big brown bats commonly use buildings such as attics and may also overwinter in structures.

Pennsylvania bat species do not all have identical conservation status. The Pennsylvania Game Commission currently identifies the little brown bat, northern long-eared bat, tri-colored bat, and Indiana bat as endangered and protected species, and the eastern small-footed bat as threatened and protected. Pennsylvania regulation prohibits a nuisance wildlife control operator from controlling threatened or endangered species without the required permits and Commission approval.

Timing is important to reduce the risk of separating adults from flightless young. Pennsylvania Game Commission guidance identifies Pennsylvania's bat maternity season as May 15 through August 1. Bat exclusions should not be performed during that period. The guide also warns against sealing active bat exit points during winter where bats may be overwintering. Winter one-way work requires timing that allows bats to leave when regular spring activity resumes.

If a bat is found in a living space, avoid bare-hand contact and keep people and pets from handling it. If human contact may have occurred, contact the appropriate health department or healthcare provider promptly. If the bat is available, public-health guidance should be obtained before releasing it because testing may be appropriate.

Guano may provide a growth medium for microorganisms, some of which are pathogenic to humans, such as histoplasmosis. Accumulations of guano may fill spaces between walls, floors, and ceilings, may create a safety hazard on floors, steps, and ladders, and may even cause ceilings to collapse. The weight of droppings and urine can potentially compromise structures. Do not disturb deposits of guano unnecessarily. If possible, dampen them with water or schedule outdoor work at a time when the ground is relatively wet, in order to minimize airborne dust.