Rabbit's Fur Problem - "buzz cut"??

by Hannah

Hi there,
I'm wondering what's wrong with my male Holland lop's neck fur. It's not matted, it's like he got a buzz cut under his chin/neck area. I haven't found any signs of mites (though I'm no expert there:)

He is housed right next to our unaltered doe, and I'm wondering maybe if his "buzz cut" is a sign of stress?? He doesn't have any open sores or anything, and the patch isn't completely bald down to his skin...the best I can describe it is somebody gave him a buzz cut under his neck. :-/
Any idea what is causing it? is it a real problem?? Solutions?
Thank you