Rabbits really do best in separate cages. Especially if you have both bucks and does. Otherwise you will quickly be over run with rabbits. Bucks will fight with each other, most does will fight with each other. They really are solitary animals. If (however) you mean to put straw under the cages, that would be fine I guess. I can't really comment on rabbits on straw as ours get hay every day, but have never given them straw. I don't suppose it would hurt them, I know ours love the oats they get as a treat now and then, and straw is made from oats. Hopefully someone with more knowledge on the straw part will come along soon.