They have chewed multiple holes in the roof felt, and generally made a mess! They like burrowing under the insulation, and although they tend to defecate in neat piles, it's still not pleasant having to clear it up every year. There is no physical way to keep them out, and I appreciate that they keep rats and mice at bay, but I'm looking for ways to deter them. An ultrasonic device doesn't appear to work. Does anyone else have this problem, or can suggest a way to deter them?