A wolf pack maintains order through its hierarchy. This order is constantly reinforced by displays of dominance and submission in a complex mix of vocal and physical communications that wolves employ to express and maintain their status. Mistakenly, people too often interpret this language as being viscious and evil, but it is simply the way wolves communicate.
A wolf's posture when encountering other wolves says a lot about its status in the pack. Subordinates crouch and often lick at the dominant wolf's muzzle like a puppy, while alphas are readily identifiable by their stiff-legged gaits and high tails.
Wolves have an extensive repertoire of sounds. Whines and whimpers indicate friendly interaction but also show frustration or anxiety. Growls and snarls are threatening or defensive. Barking is rare, usually an alarm signal. Howls seem to be about togetherness, whether the wolves are gathering for a hunt, mourning a lost pack mate, or announcing territorial or mating intentions.
Smell is probably the most acute of a wolf's senses. Male and female urine differ in chemical composition, so scent marking—urinating on trees—can advertise availability. A paired couple may leave double scent marks, declaring their status as mates and warning other wolves to stay away.