I have a male cairn terrier who has not been castrated. When he is off his lead in the park with other dogs he will not come back to me. If it is just one other dog he is very well behaved and responds to coming back for a treat but if he is part of a 'pack' there is no hope. We are undecided as to wether to have him castrated. He is very good natured. Has anyone got any suggestions?