Bat Exclusion is currently the recommended method of bat removal. 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 a bat colony is permitted to exist at one location, the more difficult it may be to expel them from the building. Additionally, the colony may grow in size each year.
Bats are most difficult to exclude from some large multistory buildings, such as warehouses and factories, that have many crevices and other places of concealment, and when semi-open roosting sites exist, such as large porches or roofs projecting over loading docks. Where ample habitat is found, a bat colony displaced from one area of a building may simply move to another area. If a seasonal infestation is tolerated for a time, the building manager may be relieved when the bats leave, believing the problem has disappeared. It is unwise, however, to assume that they will not return, because they frequently return year after year to the same site.
One of the easiest times to bat-proof a building is after the bats have left for the season. To exclude most bat species from a building, openings larger than 3/8 inch must be closed to prevent access. Hardware cloth (1/4-inch mesh) or sheet metal are the materials used most often to close entrances, although softer building materials are also useful, such as aluminum flashing, particle board, and plywood. These materials can be fastened to the building using a 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 may more closely match the natural texture of the building. An effective way of sealing or filling voids within walls occupied by bats is to inject one of the newer types of wall insulation foams through holes bored into the wall. The work should be completed during the evening after the bats have left to feed.
If foam or other loose-type insulation is used, be certain that any substantial amount of droppings are first removed and not just covered over, for objectionable odors may continue. Quick-setting hard putty can be used to close some small openings. Sealants, caulking compound, weather stripping or equivalent materials are effective for closing long, narrow cracks. Copper mesh or large stainless-steel scouring pads (which do not cause rust stains) are useful for temporarily plugging openings in Spanish tile roofs. Such openings can later be sealed with mortar.
When bat-proofing, Varment Guard technicians 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.