Bat Exclusion and Removal

A call came in from a new homeowner last month in Freehold claiming they have been hearing noises in there attic for the last couple weeks. This young couple had just moved in last November, but only just started hearing the noises in early April. They thought maybe mice but would like someone to check for them. So off me and Matt (my wildlife specialist with over 20 years experience in the field) headed out for the inspection. The access to the attic was through a hatch in the ceiling of a hall closet. I doubt anyone has been up there. As popped our heads up into the attic the smell of feces and urine was overpowering. We both returned to the truck to get our respirators.

When bats roost inside homes, particularly in attics, chimneys, or hollow spaces between walls and floors, the occupants may object to noise from bat vocalizations or activity. Bat droppings (guano) and urine may cause a persistent  stench that is intolerable to humans. Moisture from there urine and droppings can penetrate wallboard ceilings and walls and stain interior surfaces. In some situations, the only remedy is to remove and replace the stained portions. If large colonies have roosted within a building for extended periods, guano removal can be expensive and homeowners insurance will cover.

Bats are implicated in a number of human diseases, although rabies receives the greatest attention by public health officials. Histoplasmosis, an often fatal systemic fungal disease affecting humans, may be a significant hazard to people who work at removal of bats and bat guano (feces). The bat themselves do not transmit histoplasmosis, but the fungus, can be contracted by inhaling the airborne spores in the dust of bat manure that supports the growth of this fungus. Besides rabies and histoplasmosis, bats are also implicated in other diseases such as Chagas` disease, endemic relapsing fever, and St. Louis encephalitis.

Matt & I re-entered the attic and found bat guano that accumulated in different areas as well as live bats. Our inspection now moved to the exterior foundation. Bats can enter through openings as small as 3/8 inch in width. Common entry points to homes include gable vents, utility penetrations, loose flashing, uncapped chimney flues, and facia board gaps.

Exclusion is currently the recommended method of resolving most bat invasions. A colony of bats or a few individuals of a solitary species may be excluded from a building through their removal and bat-proofing. Bat colonies are easier to dislodge from a roosting site if efforts are made soon after they initially take up residence. the longer the bat colony is permitted to exist at one location, the more difficult it may be to expel them from the home.

To exclude bats from a building, openings larger than 3/8 inch must be closed to prevent access. Hardware cloth (1/4 inch mesh) and sheet metal are the materials used most often to close entrances. These materials can be fastened to the building using heavy duty staple gun or cordless screwdriver and wood screws. Unlike rodents, bats cannot gnaw their way through softer building materials, which are easier to work with and more closely match the natural texture of the building. Caulking compounds are effective for closing long, narrow cracks.

When bat proofing, we pay particular attention to chimneys gable and soffit vents, cornices, warped siding and flashing, stone and brick veneer gaps, shake siding, fascia board gaps and utility penetrations. All known  and potential points of bat entry can be sealed except several of the principal openings followed by waiting a minimum of several days. A one-way door (bat door) device is installed at the primary point of entrance that will permit the bats to escape during the evening but prevent them from re-entering the roost. Where many exit holes exist, the same one-way passage of the bats can be accomplished by using lightweight plastic bird netting, loosely fitted and draped over the opening and, secured on the sides, and extended down several feet from the opening. the bats can crawl out from under the netting upon exiting but are blocked by the netting when they attempt to re-enter the opening to there roost.

The first night the customer placed lawn chairs on his front lawn and counted more than 30 bats leaving his home that evening. Matt and I returned two weeks later to remove the one-way bat cones and seal up the final points of entry.