I'd like to let my bunny out more often but he started this habit of peeing on a certain part of my carpet. If I cover it with a big piece of cardboard he pees and poops in the bathroom which is fine. He doesn't go anywhere else, and he has a litterbox in his cage which he never misses. How can I get him to stop peeing on the carpet in that spot so I don't have to use cardboard on my floor? Looks tacky for guests.