In recent times bat colonies in houses appear to be less tolerated. Entire local bat populations, whose maternity roosts were in buildings, have been purposely destroyed. Bats that have adapted from one roost type to another are now imperiled by changes in human tolerance of bats and by changes in building construction, i.e., cavity wall insulation, modern churches without belfries, flat gravel roofs, and less use of attics and shutters. The general requirements for bat roosts in buildings are known. Less well known is the importance of other factors that govern roost-site selection such as temperature, humidity, vegetation, and the physical characteristics of roost sites.
Older structures are particularly attractive to bats.
When Bats Cause Problems Bat colonies may cause a nuisance when they are located in buildings. The noise created by bats squeaking, scratching, scrambling, and crawling in attics, walls, and in chimneys can be objectionable if the roost site is close to human living quarters. Bats nearly always reveal their presence by their fecal droppings left beneath entrance holes and below roosts. Brown stains and odors from urine, feces, and glandular body secretions, found near the eaves of wooden buildings and barns, may often indicate the presence of bats inside the structures. In old, loosely constructed buildings where there is an attic roost or a space between the wall and a chimney, excreta may seep through cracks and stain ceilings and walls.