I have never figured out what triggers that biting mode to set in, either. My Roger can be very gentle one second and then start the biting the next. And it hurts, doesn't it? Imagine what it would be like with a larger breed!

I usually offer my finger to Roger and ask him to "step up". If he doesn't do it right away, I usually back off because that is the time he is most likely to nail me.

Roger's "wife", Milly, has only ever bitten me once and it was when she was sitting on eggs. She is very gentle, otherwise.