What are the white stains left by my male rabbit in his hutch?

Ignore all the silly comments. It's only urine. Rabbit urine stains things white. Make sure you clean the hutch out once a week, and every other day clear out some of his mess. If you dont already have one, get a pet safe cage cleaner, you can get them from pretty mch any pet shop, helps get rid of the stains, and bacteria!