Loki digs in Woody Pet... digs it right out of his litterbox.:rollseyes
I wouldn't recommend clay cat litter, even if it's nonclumping, because it's so dusty. Sand would be good though, and less messy than dirt. I keep meaning to give my buns a box of sand. What mine also love is a cardboard box stuffed with newspaper and hay, or just a big old pile of newspapers.