Mystery

My very smart, environmentally conscious, and animal-guru friend, MCF, thinks the baby wolf I saw in Yellowstone might instead be a fox or a coyote. I really want to get to the bottom of this. Here are the pictures I took. I need your opinions. (Remember that I'm photo-challenged)

Yes, he's doing exactly what he looks like he's doing. lol.

What say you?! Is he a wolf, coyote, or fox? Either leave a comment or answer poll to the side. Thanks!!