International Journal of Comparative Psychology

We have long observed dolphins producing recognizable sounds—bursts of pulses with sweeping peak frequencies—at prey capture.  We call this the victory squeal.  When dolphins hunt fish, there are three sequential sounds:  sonar clicks, terminal buzz, and the victory squeal. When dolphins find a fish with sonar clicks, but reject the fish during the terminal buzz phase, they omit or truncate the victory squeal.  We also observe dolphins producing the victory squeal after a trainer’s bridge, which serves as secondary reinforcement that bridges the time gap between the dolphin’s performance and delivery of food reinforcement.   It signals the dolphins that they responded correctly and that reward is forthcoming.  Before training, the victory squeal came after fish capture, but with successive trials, there was a forward shift in the victory squeal to come about 200 ms after the bridge.  The victory squeal immediately following the bridge suggests the dolphin expects reward. Although there are no direct studies of dopamine release in cetaceans, early brain stimulation studies demonstrated consistent timing that may link the victory squeal with brain dopamine release. In the current study, we asked if dolphins might produce the victory squeal after task completion, but without the trainer’s bridge.  Dolphins carried cameras, recording video and sound, while performing tasks in the open ocean, away from trainers, during swimmer/mine marking and retrieving.  In each task, we observed the victory squeal immediately upon completion of task components.  We suggest that the victory squeal signals that these experienced dolphins recognized their success.