Abstract:
This thesis presents methods to analyze the function of vocalizations of the bottlenose
dolphin, Tursiops truncatus. The thesis uses the social interaction as the basic unit of
analysis, and maintains a deliberate focus on quantitative and replicable analyses
throughout.
A method for determining identity of the vocalizing animal in a lagoon was developed.
This method combined passive acoustic localization with video sampling to determine
which animal vocalized. It fills an urgent need for unbiased identification of
vocalizations of undisturbed dolphins where details of social interactions can be followed
without affecting the behavior of the subjects. This method was implemented in a
captive lagoon with 6 dolphins: two adult females, their two male calves, and a juvenile
male and a juvenile female.
This thesis also reviews the current state of analysis of the bottlenose dolphin acoustic
repertoire, highlighting the need for a detailed, quantitative, and consistent study of the
entire vocal repertoire. It does not attempt to do a comprehensive repertoire study, but
uses several new quantitative methods to parameterize vocalizations and relate these to
behavior from dolphins. Vocalizations within the lagoon tended to occur around the time
of onset of behaviors produced by the focal dolphin. A comparison of vocalizations
during affiliative and agonistic interactions revealed that the association of group
vocalizations with the behavior of a focal animal was related to agonistic but not
affiliative interactions.
Using the localization/video method, vocalizations in a time window around submissive
behaviors were localized and classified as having come from either dolphins engaged in
the interaction or dolphins not engaged in the interaction. Vocalizations were emitted by
interactants more often than expected, and by non-interactants less often than expected.
Use of different vocalization types was found to vary depending on the context of the
agonistic interaction. In addition, the sequence of vocalizations with respect to behaviors
within the interaction mattered, with more vocalizations occurring after than before
submissive behaviors. These results demonstrated that group-based analyses of
vocalizations are insufficient and one must use techniques designed to focus on the level
of the interaction in order to study communication and social behavior in dolphins.
