Two years ago, my dad's cleaning lady called me at work to ask how she could contact my dad as something 'strange' was going on in his townhouse. My dad was at the Ocean for the week, and on her day to clean, she let herself in and found shredded paper in the den. She cleaned that up, went upstairs and cleaned up there. When she came back down, there was more shredded paper (from the fanfold computer paper). When I got there, we realized it was a critter, ended up being a squirrel, got in thru the cloths dryer vent (flapper valve was stuck open) and chewed thru the plastic vent hose and 'had the whole house to himself'. We opened up the back door and ended up herding him out. Ended up putting chicken wire over the dryer vent.
Steve