I have a 10 month old cat (Mittens) and just got a 3 month old chihuahuha (Alex). They started smelling around eachother right away and started playing. My cat has never hissed when he's introduced to another animal. They play, roll around with eachother and chase alot. How do I know if it's getting to rough though?? After they calm down a bit the dog attacks the cat just the same to start again. When they are rolling around playing they dont hiss or bark or make any pain noises but it looks rough. When they are playing together the dog always has his tail wagging and hopping at the cat. They sleep by eachother once in awhile and are fine. Is it ok to let them play yet or should it be stopped? Thanks