We have a 3 year old Jack Russell boy, one of a litter of 5, and still living with his mother. We have worked hard to make him number 2 dog, and he generally defers to her, even though he is now twice her size. He is good with people, dogs, livestock etc, but has recently developed a bad habit of nipping people (adult men, always) whilst one of us is chatting to them on walks. It doesn't seem to be territorial, as the last three have been away from home. Neither does it seem to be protection of his mother, as she is nearly always off in some local bit of greenery hunting when these things happen. He normally likes to please, and seems genuinely remorseful once he has done one of these. Any advice of what we should do, or what kind of course we should attend? Many thanks. Roger