I did some googling to see if I could find out anything for you. Some suggestions:
Dove bar soap, "Classic" Ivory soap, Bitter apple, Vinegar OR Perfume (on a rag), or a cayenne pepper repellent, rubbed over the area to protect from bunny interest
Squirting the buns with water when they begin to chew on the shelf is also suggested to deter chewing.
I guess it's whatever makes sense to you and your rabbits. I wish you luck!
bitter apple definitely wouldn't work, lol... I've got this stuff that's even stronger than bitter apple spray - it claims to be made from "the most bitter stuff on earth" and MAN, is it noxious!! worked like a charm for a couple weeks... then Nala suddenly developed a taste for it >.>
water's also probably out 'cause she likes to wake me up with the chewing and because I sleep on an air mattress on the floor/she chews on the highest level of the condo, I'd have to actually get out of bed to squirt the little punk.
sounds like I've got the right kind of soap, though, so I'm gonna give it a try and cross my fingers she hates it
now if only soap could stop loud digging...