If you can locate a bull then you should try to go kill him. What does it really matter if hes the herd bull. Easier to kill the bull that is out searching for cows. My Biggest BUll was a lone bull. My first chance at him tried just cow calls. He would answer, but wouldn't come in .
Next day we got him all fired up with aggressive bugles and raking. He came running in and took an arrow thrust the Heart.