We were called out to a termite inspection and bat estimate for a poorly maintained house. Our vertebrate technician, David Adragna, took these pictures (May 2016) of what might be the worst bat infestation we have seen.
Bat poop, or guano, littered the inside, piled high under the main beam of this A-frame house. Contractors sometimes fail to properly trim around the main beams, leaving gaps that bats can enter. Often woodpeckers damage well-trimmed houses, opening a space to store acorns, and consequently, allowing bats access to the space above the beams. The space above a main beam, and below the roof, makes an excellent roosting area.
You can see, from these photos, just how bad a bat infestation can get.