You probably already know this but whistling seems to be the only way to kind of 'call' a groundhog I have seen. Well it isn't really calling them but it will get them to stand up because whistling is thier means of communication to eachother. A short snappy whistle will most of the time put a chuck on its two hind legs long enough to get the shot.
A loud dog whistle or the like would be good unless you can give out a good hoot yourself... /ubbthreads/images/graemlins/laugh.gif Over the years I have finally 'perfected', so to speak, my whistling skills and am able to almost deafen anybody near by when I let er rip.
After all...alotta folks call them 'whistlepigs' for a good reason I suppose /ubbthreads/images/graemlins/wink.gif