I've lost a couple plants to rabbits. It sucks. We had a mesh fence surrounding it, and a few inches under the soil. We also put large broken branches at the bottom of the hole. The fuckers came from beneath and took the entire 10 inch plant, roots and all. The problem is we planted in an area where rabbits had a little village (it was the only stealth location with a lot of sun). My guess would be to dig a large hole, line the bottom and sides with large stones, and use a submerged and raised fence. Maybe kill a rabbit and put it's dead body on a totem, with garlic, peppers, human hair, piss, and a nuclear warhead hanging from hooks in it's skin.