The bitter apple stuff never worked with any of my bunnies. Zippy said it best, keep Thelmer busy, give him lots of things he can chew on. Bunnies teeth grow constantly, which is why you cannot tell the age of a bunny by looking at its teeth. So they chew to keep their teeth "filed" down. Neutering does help to cut down some but I found age has a lot to do with it too.....my older guys don't chew up stuff like the young ones...