In October, we got a sheltie puppy and around the first of the year, we got a 2 year old cat. They were tentitive at first, but then the pup started getting more brave. Usually, when Lizzy (the) cat is walking around the house, Dexter (our sheltie) stands on top of her or gently gnaws on her neck. We have tried to get him to stop and leave her alone by putting him on his back and telling him no or putting him in a secluded hallway by himself. He still goes running back to torment the cat. We have tried loud noises and giving him something else to chew on, but we just can't get him to stop. Any suggestions?