Tuffy still humps and it's been a year since he was neutered. Luckily he only humps one thing so I don't really worry about him doing it to people or to Pixie. I would squirt him with a water bottle and give him a correction anytime you see him doing it if you really dislike that kind of behavior. You can teach them not to do it.. though it's pretty tough. Tuffy never learned.
