I am gonna guess that a large very dark form moving thru the woods, and stopping once in a while is all you need. It could be rectangular and still work. They need to see something dark.
Now, if you walk out in a field right to them, maybe not. i HAVE seen video of a guy with a moose head on a stick, with bullwinkle antlers, teasing a bull during the rut. Right in an open area. He had to stop cause the bull was obviously gonna come kick his butt.
I want my guide to do that. . ( while I am hiding off to the side).
ChuckC