Thanks again for your help. Everything looks okay as far as the skin goes. He's clean, there's no discharge, and he doesn't have fleas. He was at the vet 2 months ago and the vet said he was healthy. There haven't been any changes around the house since he started doing this. Of course, he's always done it, but not on such a regular schedule, and not for such a long, non-stop period of time every night. We'll keep an eye on him, and when we go to the vet again we'll ask. If the vet says anything interesting I'll post it here on the board in case anybody else has this problem. I looked all over the internet and I wasn't able to find any other mention of this. I was thinking maybe he's just bored or has too much energy or something, but as I said before we take him out for a long walk everyday, and when we give him a chance to go out at night oftentimes he doesn't want to go, and we play with him a lot in the evening, but recently he's just been wandering off to be by himself and do his thing. Anyway, thanks again for your help. Any other thoughts would be appreciated.