rabbits taking off their own fur

Question
I have a friend whose pet rabbit seems to removing its own fur. I saw the rabbit today and there is a place about 4 inches long and maybe 1/4 of an inch wide down its right hindquarters/back where there is no fur.  The skin is not broken and there is no sign of infection.  What is the readon for this behavior?

Thank you for your time and consideration

Answer
Is your friends rabbit a girl? Is there a possibility that it could have gotten bred? It could be some type of fur mite that you cannot see. It also may be rubbing its back or side on the cage and rubbing off its hair. I have a young buck that likes to rub his head on the side of his cage, and often he is bald on his face because of that. Other than these reasons, it has got me puzzled.
Samantha