Although the natural habitat for a mouse is outdoors, when they come indoor mice prefer quite places such as attics, garages, basements, crawlspaces or behind walls. There are several signs of a mouse infestation. Small holes in bags or boxes of food, droppings the size of small rice or loose nests of paper, cloth and other material can all be signs of an infestation. It is also wise to look for an infestation if you see a mouse in or around your home.