Izzy and Luna show their teeth, and Luna growls and yips
I used to separate them at first, I thought they were trying to kill each other. But they'd cry until I put them back together, then they were right back at it again. Izzy could rip Luna's throat out if she so desired, she's twice her size, but she's never hurt Luna at all, in fact Luna is the agressor in most of their play, while Iz lays on her back and takes it