A sickle-blade mower has a bar of roughly eight feet or so in length, with triangular saw-teeth about three inches on a side. The toothed bar slides back and forth, cutting against fixed teeth on the parent bar. It's used for cutting hay for conventional bales.
A shredder pretty much makes mulch of everything in its path; this is what's used along highway rights of way. Don't fall off the tractor seat; it's a one-time event.
Then you have your combine-type, the large rig with the blades like a giant old-timey push-type lawnmower. The wheatfield stuff.
Offhand, I don't see any easy mechanical way to protect whatever critter is in the path...
Art