My two rats have always gotten along. With the whole flipping over things Little tiffs. Artan has always been the dominant one. My other rat cauis has become a little bit of a bully. There have been rat ball fights quite frequently. no serious injuries yet..but lunging and chasing my other rat. Lots of sound. And my other rat now seems to run and hide. Caius never used to have this behaviour to artan. I'm thinking it could be hormones. And am considering a neuter of this rat. Cauis also bit me which he has never done.