I just love when I can get great behavior shots. It is fairly easy to get pleasing portraits of our subjects. But shots like this really tell a story. While it certainly looks intimidating, most of this kind of behavior between wolves is just bluffing and posturing. They have a definite pecking order within the pack and rarely does it require bloodshed for the members of the pack to know where they stand. In this case the wolf on our left is a much older wolf, you can tell this by how worn her teeth are. She is just trying to save face before backing down to the more dominant stronger younger wolf.
When opportunities like this present themselves I usually open my f-stop wide (to get a faster shutter speed) and shoot in small 5 or 6 frame bursts with my motor drive on high. I try to time the bursts to times of peak action. I will also fine tune the composition between the bursts.
Good Luck and Good Light
Steve
Image: Grey Wolves (captive) Near Algonquin National Park, Canada