Last fall in NW Wyoming, I used cow calls to draw a bull by my partner. The bull was moving his cows into the timber (about 150-200 yards away) and I moved laterally on the far side of the small valley calling intermittently...always in response to his bugles telling me to get over to him "NOW". He got so angry and impatient with me that he actually left his cows to come and get this "straggler" who wouldn't come directly to him. Now bear in mind that I wasn't moving toward him, away from him or staying still - I was moving across the slope SLOWLY.
As he was crossing the small creek broadside in front of my partner - at 30 yards - he was obscured by the willows (except for his head). Long story short, he stopped and stared in my partner's direction for over a minute and then simply turned and went back to his cows - disappearing back into the timber. The bull didn't wind him but saw or sensed something he didn't like. It was quite a thrill for both of us, to say the least. This was my first experience actually "talking" with a bull...amazing!
Hope this helps...