Wolves display an extremely strict, complex social hierarchy within their packs - much of which is expressed through relatively advanced communication through body language. This strict social ranking is effective in promoting social unity and order, which, in turn, greatly increases their success and survival, and contrary to some perceptions, prevents conflict and aggression. In an established pack, rarely do problems escalate to a physical level.
[Photograph by spackman. Original body language chart source unknown via google images).]