It can when it becomes a dominance thing. My weimaraner and a friend's dog used to play together at the park, everything was fine and for over a year we met every single night, then one day my friend brought a rope toy and they started playing tug, at first it was great, looked like they were having fun with it, but after a couple of nights doing this it started to get ugly, one would snarl at the other if he had the rope and then out of nowhere they just went at it and it turned into a big bloody mess, after that we couldn't hangout together because the dogs hated eachother and fought as soon as they would see eachother, it was ugly. I think it just depends on the dog's personality and if it already has aggressive tendancies, both of these dogs were alpha males, so I think it had a lot to do with it. So, from my experience, yes, I think it can under certain circumstances, but I wouldn't worry too much about it with you and Coco playing
