What creature made this hole in my yard?

I always grew up in Jersey suburbs, but I might as well be a city boy when it comes to some things. About six months ago my wife and I moved to Raritan Township (Flemington mailing address; I never know where to tell people I live) and our back yard ends at a large stretch of woods. I've seen foxes, beavers, and many, many deer along with a bunch of other critters making those woods and our yard their home. I've even wondered if I'll ever see a bear back there. It is Hunterdon County after all.

Well the other day I noticed a hole in the yard. Now I don't mind sharing, but this hole has me concerned. Something has burrowed into the ground and I'd love to know what it is. I don't know enough about this sort of thing to know if anyone can tell just from the size of the hole what it may be. Nonetheless I'm asking. Any thoughts?

To give you a sense of the size here's another picture with my foot next to it.

If it's one hole I don't see it as any big deal. But if it's the kind of critter that is going to be making a ton of these and destroying the yard, then obviously I care. So if you're good with this sort of thing I could use your opinion. What creature do you think I could be dealing with? Please email me at DD@NJ1015.com or use the comment section for your best guess. Thanks!