If you can pull the grass back and see a little dug-out den, its a rabbit. If it's a true hole, it could be a vole, mole, or any number of burrowing varmint. I don't have anything for scale but it does not look like a groundhog.

I've run over more baby rabbits with my lawnmower than I'd prefer but it's hard to tell if it's one of their dens.