I know these situations can be scary, my student was afraid and decided to leave the enclosure (the metal sound of the fence you hear), but I assure you, if you let your canine companions sort out their own conflicts they will become well adapted. Wolf and I survived a conflict so surely you dog can understand his own language.
Wolf Testing Bison
Wolf Chases Bison
The wolf, probably Ruedi, is trying to split the herd of bison. Junior, the head bull, will have nothing to do with it. He is trying to protects the truck against apple thieves, note that Ruedi is scenting the air either for apples of for sick bison, or even both.