I think hair chewing is a sign that they need more protein in their diet? Other people will know more and me answering you will bump this thread back up to the top of the list.
I know it's a thing with chickens. They eat feathers if they need more protein. I'm pretty sure I've heard it here somewhere and just didn't doubt it cause of the chicken thing.Or it could be the protein thing, I've never heard of it but it seems others have..