Has anyone come across this before? One of my rats spends periods vigorously shaking/flicking his head and body for a second every couple of seconds. Like you might if you were trying to shake a bug out of your hair. This goes on for a while and seems to be worse at night. I thought he might have mites but wouldn't he be scratching a lot instead? Anyway he's been treated for them previously just in case. It doesn't seem to bother him greatly, it's more disturbing to me I guess. He's otherwise very healthy although getting quite old. I'm just wondering what could be irritating him like that. Has anyone seen this symptom before?