So what do these findings mean? Well, we can’t tell whether dogs intentionally alter their barks to deliver a message to other dogs or people. The only way to determine this would be to teach the dog English so that he could tell us, “I am now intentionally changing my bark to deliver this message.” Most likely, the variation is a reflection of the internal motivational state the dog is in at the time that he barks.
What we can tell is that because there are specific bark subtypes, barks have the potential to play specific communicative rolls and provide specific information—intentional or unintentional—to the animals, including humans, who are listening. Not specific like, “Timmy’s stuck in the well! The one to the left of the big oak tree on the other side of the creek!” More like, “I’m separated from you! Come get me!” or “Intruder alert!” Furthermore, since bark subtypes occur in specific contexts, we can learn to tell what our dog is saying by listening to his barks and then examining the context. His “woof” for an unknown intruder may be different from his “ruff” when he alerts to a friend approaching the house. And his “huff” to come inside may be different when the desire is more urgent.
But is the barking actually communicative? Well, for a vocalization to be communication, the animal who hears the signal must respond in a specific way. As with the chicken food-call and alarm-call cases, this is usually tested through play-back studies, and such studies have not yet been performed on dogs. However, a study by David MacDonald and Geoff Carr on free-roaming dogs in Italy suggests that barks can have specific effects on other dogs, even when the “barkers” can’t be seen. The free-roaming dogs in this study lived in small groups and scavenged at local dump sites. When the largest group of dogs barked in a group prior to heading toward the dump site from up to one kilometer away, dogs in smaller groups consistently evacuated the site; they apparently knew that they were no match for the larger gang. And on a more familiar note, Marler points out that if we pay attention, it’s easy to notice that barking usually elicits a response from other dogs.
But this is only half the picture. Says Owings, “For the vocalization to be communicative, the vocalizers should be sensitive to social contexts and consequences.” That is, the animal producing the vocalization should adjust it based on the behavior of the listeners. While there is little research in this area, general observations indicate that this happens too. For instance, when one dog barks at the doorbell and another dog, or even the resident human, joins in a barky “No! No!”, the dog responds with louder and more prolonged bark behavior. Take away his back-up and suddenly, the initial barking bout abates. Or then there’s the dog who barks at you until you toss his toy, but barks harder and louder when you’re on the phone because that’s the time when you’re most likely to toss the toy quickly in order to get him to quiet down. These cases provoke the question: What exactly is the role of the human (the primary animal to whom many barks are directed) in the development of bark behavior in dogs?
Clearly, there are an infinite number of questions about barking and its communicative function for the dog, and there’s much catch-up needed to reach the same level of understanding that we have for chickens and squirrels. But it all starts with a simple study showing that dogs have different barks in different contexts, and plugs away, developing and answering one question at a time.
To test your own ability to interpret dog barks, or to read more about barks as communication or as a nuisance behavior, visit Dr. Yin’s “Nerdbook” website.