BATPROOFING STRUCTURES WITH BIRDNETTING CHECKVALVES

Denial of re-entry (batproofing) through structural modification is widely accepted as the most effective and ecologically sound method for eliminating commensal bats from structures. Such methods are clearly superior to lethal measures which have only questionable efficacy and may exacerbate bat/human interactions. However, since bats are able to enter small and obscure openings, conventional batproofing of all such openings is often not practical or economical. Further since this work must usually be done after bats have already begun roosting in a structure, the difficulty of high ladder work at night to seal exit holes can be discouraging to homeowners as well as to pest control operators. A few exclusion devices have been developed previously, but are not readily adaptable to the frequent situation where bats are using diffuse, large, and/or widely distributed exit holes. Polypropylene birdnetting has been field-tested over two seasons as a batproofing tool against little brown bats (Myotis lucifugus) and big brown bats (Eptesicus fuscus). In all cases the work was completed either before young were born or after they were able to fly. The netting is fitted as a checkvalve which allows bats to escape from a structure but prevents their re-entry; thus, the netting can be conveniently applied during daylight hours. At dusk, bats easily find their way out, do not become entangled, and are not driven indoors into the living quarters. At dawn, bats return in their typical swarming behavior, repeatedly land on the net, but are unable to find their way around or under it. Several checkvalves designs have been adapted to cover different patterns of exit holes associated with various architectural details. Specific application techniques with birdnetting checkvalves and responses of the bats are discussed in reference to overall bat management programs