Because wildlife has adapted to living in close proximity to us, they don't mind sharing our homes. They frequently gain access to a home by chewing through roofing shingles or by discovering a small hole along the roofline and chewing it open until it is large enough to break entry. Vents are another common entry point for them into your home. Squirrels, for example, can wreak a lot of damage if they chew on electrical lines, and given the nesting materials they've brought into your home, they could even start a fire.