So Paul,
What is the answer, or is there one to get this bull to come to you. I have had this happen on many occasions. I have even had a cow follow me down the mountain barking. Last weekend I had a bull do this "nervous grunt". My son was hunting and I tried moving away and cow calling as I went, but it seemed the bull wouldn't come across the small opening toward my son. I have always felt that this type of bark or grunt was done when an elk was alerted to the hunter's presence but did not wind him--possibly may have even caught a glimpse of the hunter but couldn't identify him. Can you share more?
Mike