Mice commonly occupy attics in Michigan. Some of the signs that you have trouble in the attic is a scampering noise, gnawing noises, droppings in the insulation, and tunnelling in the attic insulation. Attics provide a warm secure environment that provides protection from predators.
It is a good idea to have your attic inspected on a periodic basis. It is vital to maintain a supply of rodenticide inside the attic to control mice populations. Prevention is the key to a mouse free home.