Not only do we have an armadillo (or several) running amok on our property, we have now discovered a full-blown, well-formed tunnel in the pasture. The pictures didn't turn out well, but it was amazing how smooth the tunnel walls were. (And no, I didn't put my hand in there to feel them, lol, although it was tempting.) At first we didn't know if it was a burrow or a tunnel, but then we found another entrance -- about 50 feet away! --so that made it a tunnel. Hubby said he later found a third entrance even further away.
In looking around on the web for what might be doing the digging, a gopher appears to be the most likely culprit. Even the southeastern pocket gopher, despite its small size, can dig extensive tunnels.
Does anyone have any other ideas of what might be making the tunnels?