A mammal for all seasons: Contributions from the bottlenose dolphin TRO to bioacoustics research at the US Navy Marine Mammal Program

Abstract

Among the notoriously small sample sizes of marine mammals in cooperative behavioral research, there is an even smaller subset of subjects that can be considered “experts.” In essence, these are subjects that have “learned how to learn” in the contexts of novel experimental paradigms. One such subject is the bottlenose dolphin TRO at the US Navy Marine Mammal Program. The first scientific publication including TRO heralded his potential; aided by a phantom echo generator, he was likely the first marine mammal in history to echolocate while out of water. Subsequent behavioral experiments with TRO have examined numerous aspects of biosonar, including transmit beam characteristics and the use of click “packets” during long-range target detection. The patient nature of TRO has made him an ideal subject for electrophysiological studies, where he has diligently listened to exotic acoustic stimuli designed to examine auditory processing in the dolphin brainstem. The most significant scientific contributions from TRO are arguably from studies that have used auditory evoked potential methods during biosonar tasks. These data provide the temporal resolution necessary to examine hearing at the level of click production and echo reception and are a result of TRO’s dependable participation in studies combining multiple experimental techniques