In Minnesota and Wisconsin we have many species of bats, but only a couple invade and breed in structures.  The two species that are pests are the Big and Little Brown Bats.  When bats choose a structure to live and breed they either overwinter in the structure or leave and return in the spring to resume nesting.  Bats carry parasites like mites and batbugs and can carry diseases.  The primary disease they can cause is found in there droppings when inhaled called Histoplasmosis. If you notice or suspect bats living in your home you should call a professional to schedule an inspection.  If you do have bats roosting inside of your structure we use exclusionary methods to get rid of the infestation.  We leave devices on entry/exit points that allow the bats to leave and they cannot re-enter.  We also seal up any possible re-entry points on the structure.  Bats cannot chew through closed areas because of their very brittle teeth, so once sealed they have to go elsewhere.