Vocal Response of Bottlenose Dolphins (Tursiops truncatus) to a Novel Stimulus

Bottlenose dolphins utilize acoustic signals as their primary mode of communication. Although some aspects of dolphin vocal behavior are well understood, less is known about vocalizations in different behavioral contexts and how these vocal behaviors may indicate habituation and sensitization. The focus of this study was to investigate how bottlenose dolphins respond vocally to a novel stimulus. Archival data from three populations of bottlenose dolphins (N = 20) living in a human-care facility were exposed to a novel apparatus (a mirror) for 10 trials, each lasting 20 minutes. Five of the trials presented the mirror covered with an opaque cloth whereas the other five trials left the mirror uncovered, exposing the reflective surface. Rates of two distinct vocal types (whistles and burst pulses) were calculated for each trial. Vocal rates were greater on the last (non-novel) trials versus novel trials—a pattern of sensitization to the novel stimulus. Vocal rates and the degree of sensitization were greater on reflective trials than non-reflective trials. Finally, vocal rates were greater for whistles than burst pulses overall, but sensitization was most apparent with burst pulses. This study identifies how the production of two types of vocalizations change in response to a novel stimulus of varying reflectivity over repeated exposures thereby providing a greater understanding of the contexts in which these utterances are used.