Balls are picky, and he might not want to switch. You are feeding live? Will he eat F/T? I know to switch some people will thaw a rat and a mouse and rub them together really good so the scent of the mouse is on the rat and the snake will be more apt to taking it. Few times of doing that and it usually stops being an issue. I'm not sure rubbing a live mouse with a live rat would go over so well, though...