I see a few other threads about this sort of behavior, but I thought I'd throw my hat in the ring. I've noticed a few small spots of blood in my chin's cage over the past few days, but couldn't find any source until just now. I thought maybe it was just dry feet from all of this cold weather, but we just noticed Momo chewing his tail. He has been a little more mellow than usual, but still eats hay and pellets with enthusiasm and runs on his chin spin. I attached a photo of where he's chewing. The area seems healthy (if a bit red, like maybe it healed over) and he didn't mind me dabbing it with a damp q-tip to check for injuries. Does this warrant a doctor's visit? Should I just keep an eye on him or should I take his wheel out for a few days? I've read that some people see this with certain cages and tails rubbing on bars, but on the rare occasion that Momo will stick his tail out of the Critter Nation cage he can't fit the whole thing through the bars.