The Choreography of Belonging: Toothed Whale Spatial Cohesion and Acoustic Communication

Nicholas Macfarlane, Ph.D., 2016
Peter Tyack, Advisor

By simultaneously deploying acoustic tags on closely-associated pairs of dolphins, this thesis investigates the acoustic signals they use to maintain spatial cohesion. These first reported deployments of acoustic tags on dolphins uncovered large variation in vocal rates and inter-call waiting time between animals. Looking more specifically at signature whistles linked to cohesion, I found that one animal’s whistle increased the probability of its partner responding with its own whistle. To better evaluate potential cohesion functions for signature whistles, I then modeled the probability of an animal producing a signature whistle throughout a temporary separation from its partner. These data suggest that dolphins use signature whistles to signal a motivation to reunite and to confirm identity prior to rejoining their partner. To examine how they might maintain cohesion during separations without whistles, I investigated whether dolphins could track their partners by passively listening to conspecific echolocation clicks. Using a multi-pronged approach, I demonstrated that the amount of time since an animal last detected a click from its partner helped explain its probability of producing a signature whistle. Finally, this thesis developed a portable 3D stereo photogrammetry system to study cohesion in situations where tagging is not possible.