Marine mammals as models for charting the evolution of social vocal rhythm

In this Perspective, we suggest combining physiological, neurobiological, behavioural, and social data from multiple marine mammal species to create evolutionary models of the emergence of social vocal coordination. Marine mammal sound production mechanisms have evolved to manage vocalizing and breathing in an aquatic environment, potentially releasing functional constraints on the control of vocal timing. Intervals in rhythmic cetacean vocalizations cover a remarkable temporal range, from less than a millisecond in porpoise burst pulses to 10 s in sperm whale slow clicks. Many cetaceans demonstrate temporally coordinated social behaviour, while pinnipeds express high variability in vocal plasticity and social behaviour. The systematic variability of vocal production mechanisms, vocal rhythms, and sociality can be compared phylogenetically to generate models for the evolution of social rhythm in the vocal domain.