This page details the basic quirk to this fictional sport. You can't get knocked out, and you can't get pushed/thrown out of the ring either! It's a mix of MMA and wrestling, essentially. Considering animal characters have different species-related quirks and physiques, I'd imagine such a sport would be really fun to watch in the animal kingdom... so I made it a reality here!
Side note, I'm kind of proud of how I made Nes's pose look in the third panel. It genuinely looks like he's sucking in air through his teeth. X3