What kind of damage can bats cause you ask. Most people usually notice the odor from bat guano and bat urine first. If the colony is large enough, people also notice the noises that bats make. They are generally harmless animals, they don’t chew on wires like rodents do, but the main problem they cause is that they poop and pee a lot. Each bat can poop 20 pellets per day, and if you multiply that number times hundreds of bats over a couple of years, you get an attic full of bat guano! It smells bad, it corrodes wood and drywall, and it can grow mold. Bat guano (bat poop) can contain histo spores that can lead to an illness called histoplasmosis. Read our Bat Damage Page to find out What Kind Of Damage Can Bats Cause.