This is what you get when you don't remove a cushion after noticing a little nibble and a few pieces of foam.
It looks like those pictures of a shark-bitten surfboard. Boomer's mouth is not that large, but he does get ferocious with foam attacks.
Sigh. I did pay just .50 for the slipcover and I can pick up the foam for reuse, but damn, I wish I had taken the cushions in earlier! And that he would stop with the gnawing.