Why Do Dogs Bark?

Vocalization of European wolves (Canis lupus lupus L.) and various dog breeds (Canis lupus f. fam.)

In 2000, Dr. Feddersen-Petersen attempted to figure out whether the different vocal utterances of domestic dogs served adaptive, context-specific purposes or if they are, in fact, meaningless as Coppinger and Feinstein hypothesized in 1990. To investigate this question, Dr. Feddersen-Petersen compared 104 domestic dogs, 12 of which were Alaskan malamutes, to 11 wolves. All animals were observed from birth until four months of age and were raised in similar conditions. Using sonographic technology, eleven different sound types were observed, with Alaskan malamutes and wolves being able to exhibit all of them, while the American Staffordshire terrier could only display four. The sound type that the researchers were most interested in, however, was the bark.

The wolf only has one type of bark: "the noisy bark sounds (which) occur in many contexts, their meanings are varied and the structure is variable." Therefore, it's almost impossible for a human to discern what a wolf bark signifies. On the other hand, the Alaskan malamute has the ability to display a noisy bark "in agonistic contexts only," when competing for resources, for example. The dog can also exhibit a harmonic, "Christmas tree" bark, named for the Christmas tree shape it diplays on a sonograph machine, in playful situations. Malamutes also have the ability to produce two other harmonic sounds that the wolf cannot produce: the harmonic "vibrato growl" and the "Mauz-sound."

As Alaskan malamutes are considered to be closely related to wolves due to their relatively high level of genetic clustering, the fact that malamutes can generate three more specific sound types than wolves speaks to the impact of domestication on dog behavior. Because of domestication, and especially through the malamute's intense role in human-controlled sled racing, the dog breed has had to develop more effective ways of communicating with humans than their ancestors. The harmonic "Christmas tree" bark and "vibrato growl" exhibited in playful situations speaks specifically to the effect of the increased exposure to humans that malamutes have experienced through domestication. These results also showcase the relatively high rate that the domestic dog has evolved at, considering that malamutes have only been bred for the past few hundred years. 

Citation:

Feddersen-Petersen, D.U., 2000. Vocalization of European wolves (Canis lupis lupis L.) and various dog breeds  (Canis lupis f. fam.). Dummerstorf, 43: 387-397.