Certainly wouldn't advocate shooting things up the a*se as a matter of course, but saying that, I was out with a mate of mine a few weeks ago.
Shot at a fox broadside on, thought I'd hit him, but he ran. we followed him and he went flat in some young rape. Got out of the truck and walked up the side of the beam, charlie got up and ran straight away from us, as I thought he was wounded, up with the rifle and fired. He went down instantly, dead when we got to him. There was no exit wound, I can only assume that the bullet did sufficient damage as it went in to stop him.
Makes sense, a fox is