My rabbit is eating his own FUR?!?

I have a male rabbit who just turned three. I went to go put him in his outdoor excersise ring for his daily run, and I found him sitting on his loft with something stuffed in his cheeks. I had him spit it out in my hand, and it was a giant wad of fur he had been sucking on!! It's slowly warming up here in Wisconsin, and a couple weeks ago I moved Simon out into his outdoor hutch for the summer. I know they molt, but I've never seen him do this before, and I've never heard of another bunny doing something similar. He gets lots and lots of attention and plenty of free time, so I'm fairly certain it's not boredom. His diet has stayed the same since I got him when he was 3 months old. Hard food with extra nutrients, fresh timothy hay, fresh veggies, and a small fruit treat once a week. Can anyone explain to me why he would suck on his fur like that? Any help is greatly appreciated!