A wolf makes four primary sounds, namely howling, barking, whimpering and growling. It combines these four sounds into actions such as howl-whimpering or bark-growling to communicate things to other wolves or other species.
Each primary sound communicates one primary message. Barks typically communicate warnings, either to ward off an encroaching animal or defend friendly wolves. Whimpering often communicates submission, either in the form of nursing another wolf, or in the form of submitting to a dominant wolf. Growling asserts dominance, and is used to warn animals encroaching on wolves. Wolves use howling to communicate sounds at a long distance, often to other wolves in their pack.