I have no idea. I just got back from cow/spike hunting in the Blues. I was pretty dang close to some screaming bulls multiple times, heard one "glunking" to his cows and with that one even had the cows chirping back at me, but nothing would come in. Patience is probably the best advice, but hard to do. In all those situations after not hearing or seeing anything for a while I eventually made a move closer and I am sure I got busted, because by the time I got to where they should have been there was nothing, they just disappeared.
A friend gets 50 yards off the road hits the hoochie mama and has a bull and a cow run right by him, he wasn't ready, so he sets up hits the hoochie again and the cow runs right to him for a nice 30 yard shot.
Guess I need to work on some tactics for the late hunt.