Sleepy bedtime tussling turned into enthusiastic bitey-face. There was much angry pigeon-tiger play-growling on both sides, with a brief episode of "Okay, you ready for a break? Yeah, let's take a break. BREAK OVER!"
You can see Tris trying to lure Yv into full-on tussling again, trying to roll over and invite leg-grabbing, but she's not interested at that moment.