Vocal Matching in Animals
Imitating the calls of group members and mates is a reliable signal of social bonds in some animal species
We can often tell the country or region someone is from simply by hearing them speak. We do this, usually unconsciously, using cues such as speech pattern and vocabulary, which characterize regional dialects. We can also frequently discover clues about someone’s social identity based on hearing them speak: People from different socioeconomic classes or age groups may use different inflections or intonations, even if they have the same regional dialect. In the movie Good Will Hunting, for example, characters from universities in Boston use different accents than do working-class characters from South Boston. The entire cast had to adopt a regional accent, but the actors imitated subtly different versions of that accent that were appropriate for the group their characters represented.
The phenomenon in which individuals from the same geographic area or social group share vocal characteristics is not unique to humans. Such shared vocal characteristics also occur in animal species that are capable of vocal learning. Vocal learning is defined as the production of a vocalization based on auditory input. It is a uncommon trait in the animal world, documented only in birds, cetaceans, bats, elephants and some species of primates. Although most animals probably do not need social experience to produce vocalizations that are species-typical, a handful of species are believed to learn to produce the vocal signals they make. Many of the species that are capable of learned vocal production also engage in vocal matching—imitating companions to generate vocalizations with similar acoustic structures. The occurrence of vocal matching across diverse species suggests that this relatively rare trait may play an important social function in the animal world. Like the aspects of human speech that point to social class and region of origin, shared features of animal communication signals have the potential to reflect aspects of individuals’ social background, because matched vocalizations in animals can be specific to different species, subspecies, populations, social groups, bonded pairs or families.
Orca whales (Orcinus orca) are one species capable of learning matched vocalizations. These whales hunt in stable groups, called pods. Research by Volker Deecke of the University of St. Andrews in Scotland and John Ford and colleagues at the University of British Columbia demonstrated that all of the pods in a given geographic region, which are genetically related to one another and are termed clans, produce a set of matched vocalizations. The shared features of these vocalizations result in a vocal dialect that is analogous to a human accent, reflecting the animals’ lineage and group membership. However, the vocalizations of pod mates share even more characteristics than do the dialects of clan members, making it possible for researchers to determine which particular social group a whale belongs to as well as its region of origin.
This example illustrates that shared vocalizations in animals clearly have the potential to reflect an individual’s social identity. However, we don’t expect animals to pay attention or respond to matched vocalizations unless doing so improves their survival and reproduction (which evolutionary biologists refer to as fitness). That is, in contrast to considering the complex social factors that influence patterns of language similarity in humans, studying vocal matching in animals first requires evaluating how the behavior affects measures related to individuals’ fitness, because traits in animals are shaped by natural and sexual selection.