mr.beefy does it sometimes, and i'm always home... i think it's cause he's bored. he'll do it for a day or two, chew a bald spot, drive me insane, then stop. a month or two later he's back at it, you know, right after the hair grows back. i've asked the vet about it, but it they said they didn't see anything causing it. i'm not sure what to tell you if you aren't home when he's doing it, i distact beefy when i catch him, and he forgets about it.