February 17th, 2016 (Bob Yirka). A trio of researchers working off the coast of the Caribbean island of Dominica, has found evidence that suggests whales living in the Caribbean Sea have a different ‘accent’ than whales living in other oceans. In their paper published in Royal Society Open Science, Shane Gero, with the University of Aarhus in Denmark, Hal Whitehead, with Dalhousie University in Canada and Luke Rendell with the University of St Andrews in the U.K., describe their multiyear study of sperm whale communities living in the Caribbean Sea and why they believe their findings support the social complexity hypothesis.
For many years scientists have been studying both the communication and social habits of human and other creatures and over time have developed some hypotheses which they believe transcend species. One of them, known as the social complexity hypothesis, suggests that social structure complexity drives diversity in communications. To find out if sperm whale behavior conforms to the hypothesis, the researchers studied nine individual Caribbean social units (whale groupings) over a period of six years. Recordings were made which allowed for computer analysis of patterns of what are called codas—stretches of clicks and pauses made by whales, perhaps comparable to individual letters in a word, or multiple words in a sentence, for us humans. Many years of study of whales by many scientists has confirmed that the noises whales make are actual communication, not just random sounds generated for no particular reason.
In this new effort, the researchers identified unique codas and assigned them to individuals using photo-identification and other acoustic measurements. Altogether the team was able to identify 21 unique coda types, of which two were dominant, together accounting for 65 percent of all recorded codas. One of them called ‘1+1+3’ has been documented before, but now it appears it is more standard than was known—every individual in every unit made the coda in exactly the same way—but only in the Caribbean—sperm whales in other oceans or even other parts of the Atlantic don’t have the same coda, which the team suggests means that Caribbean sperm whales communicate with one another in their own unique dialect. Interestingly, the other dominant coda, called ‘5R’ was created slightly differently between members of the same units, which allowed perhaps, some individuality among group members. Taken together, the researchers suggest that the codas show that sperm whales do indeed conform to the social complexity hypothesis.
Citation : Shane Gero et al. Individual, unit and vocal clan level identity cues in sperm whale codas, Royal Society Open Science (01/20/2016). DOI : 10.1098/rsos.150372