My dog Sammy plays well with other dogs, for the most part. Being a shepherd mix, he tends to want to herd all his playmates into one convenient group by nipping them on their neck. If the dog is a large dog, he has to get on top to nip them, which is a dominance sign, which means there will be a fight if the other dog doesn’t want to be bossed around. He also doesn’t like other dogs in his home, touching his toys, drinking out of his water bowl. The exception is Sid. For some reason, Sammy has …