Bats and remedial timber treatment chemicals a review

All species of bat found in Britain have declined in numbers and all are classified as vulnerable or endangered. Their habitual use of roof voids for roosting and the formation of breeding colonies brings them into close contact with structural timbers which are often treated with long‐lasting pesticides to eradicate or prevent infestations of wood‐boring insects or wood‐rotting fungi. Some of the pesticides used have a considerable toxicity to mammals and are applied at a sufficiently high concentration to present a significant hazard to bats roosting on the treated timbers. Laboratory studies have shown that bats can be killed when they roost on timbers treated with lindane or pentachlorophenol, although some other chemicals, notably die synthetic pyrethroids, appear to be harmless. Numerous field incidents in which bats have been killed by remedial treatment chemicals emphasize the scale of the problem.