I've found a few here and. Didn't know where to look for 'em, just kinda stumbled upon them. Last year found a brand new one while elk hunting. A brushy slope, hidden from view in a tight little canyon.
My oldest son climbed in there, about 3 feet, said it looked like it hooked around the roots of a tree, I told him to not go in any further...it looked to be a very fresh dig, which made me worry, as you can imagine.