Dog leaving the bay

I think you have the answer the question of "is he afraid of you" first. If so, you have some work to do, if not, do as BA-IV says.

We often dicipline dogs but do we priase them the same? I persoanlly would try to heavily praise the dog by catching the dog (obviuosly after the hog is caught and tied) and walking him to the caught hog. I would the praise him at the caught hog and let him know you are okay with this. Maybe leave another bay dog close by that will continue to bay. Do this at the hog, not back at the four wheeler or anywhere else. Priase him and let him go back to baying. Sit down and let him know you are accepting his new behavior. He will know by you being in a sitting position that you are submissive the behavior.