Teeth Grinding/Chattering

[cee]

I had Pikachu out last night on my bed and he was having a good wander around and then he started doing his "snuggle down" thing which I like to clal is when he just stands still and looks like he's getting comfortable looking like he's dozing off. However I noticed that even though I wasn;t touching him or anything he just started random grinding his teeth and I could hear it quite clearly. I hadn't made any quick movements to scare him but was just wondering why he does that? I've notcied it he;s done it some other times in the past before, and he only ever does it when he does his getting comfortable thing..I never make him threatened, just leave him to it..then after a while he'll just get up and start moving again.

Is this only a male thing? and is it different between other breeds? Pikachu is a dwarf male boy btw...and the only one i own so its not like he can smell other hamsters or anything.