Once, when I was on a backpacking trip above timberline, I heard a couple of bulls bugle at cows after they saw my brother-in-law and me. It seemed they were warning the cows of danger. That was in July if I remember right. I just heard several elk bugle yesterday where I live (in Estes Park, Co. the elk seem to do whatever they want and they can't be hunted on most of the land in the area so they feel safe). It appears that most of the big bulls in this area have now gathered into their bachelor herds but the small bulls are hanging out with the cows (and bugling), I imagine to try to catch a late estrus cow. In other areas that I have hunted the elk pretty much stop talking (cows and bulls) by mid October. You will ocassionally hear cows and calves talking after that, but not like they do during the rut.