I spent four hours today walking over new land, and locating and marking dens with two competing pin-drop software apps on my iPhone. It's a lot of land! None of the dens are in the fields -- they are all inside the forest edge, which is thick with multi-flora rose, wild grape, and many, many trees.
I spent the first two hours walking land without the dogs, then walked another piece of land with the dogs. Guess what? You find a hell of a lot more dens with dogs!