So, I thought I'd found the solution to my beautiful Halfmoon "Curly"'s tailbiting. (Not the one in my avitar, another one). I kept him alone in a quiet room, since he didn't respond well at all to the more stimulation I tried. For about 3 weeks, that had been working - his tail was just starting to show regrowth and get a bit longer. Then just this morning while we were out, he chomped his tail again. It's in shreds. So frustrating! Nothing had changed to make him do it, and his tail hadn't grown in much yet, so it wasn't from being too long. I wish I could make him stop - he had such a beautiful tail before this started.