I have seen this play out many times when calling (grunts, rattles), typically during the rut & always a buck that considers himself alpha. If you convince him there is another buck vying for his does he will almost away come directly to you. If he isn't convinced, he'll work the area from every angle while trying to catch wind of whatever is there. You will notice many times he'll have his mouth open as if he's panting, this helps improve his senses. Scientist say it improves their sense of smell. Nogalus is spot on...it was a wise old veteran. Both bucks and does react to bleats, so could have been either.