Dolphins fishing alone in open waters may whistle without interrupting their sonar clicks as they find and eat or reject fish. Our study is the first to match sound and video from the dolphin with sound and video from near the fish. During search and capture of fish, free-swimming dolphins carried cameras to record video and sound. A hydrophone in the far field near the fish also recorded sound. From these two perspectives, we studied the time course of dolphin sound production during fish capture. Our observations identify the instant of fish capture. There are three consistent acoustic phases: sonar clicks locate the fish; about 0.4 s before capture, the dolphin clicks become more rapid to form a second phase, the terminal buzz; at or just before capture, the buzz turns to an emotional squeal (the victory squeal), which may last 0.2 to 20 s after capture. The squeals are pulse bursts that vary in duration, peak frequency and amplitude. The victory squeal may be a reflection of emotion triggered by brain dopamine release. It may also affect prey to ease capture and/or it may be a way to communicate the presence of food to other dolphins. Dolphins also use whistles as communication or social sounds. Whistling during sonar clicking suggests that dolphins may be adept at doing two things at once. We know that dolphin brain hemispheres may sleep independently. Our results suggest that the two dolphin brain hemispheres may also act independently in communication.

Two dolphins carrying cameras swam in the ocean as they searched for and marked mine simulators – buried, proud or moored. As the animals swam ahead of a boat they searched the ocean. Cameras on their harness recorded continuous sound and video. Once a target was detected, the dolphins received a marker to take to the simulator's location. During search and detection, dolphins made almost continuous trains of varying interval clicks. During the marking phase, shorter click trains were interrupted by periods of silence. As the dolphins marked simulators, they often produced victory squeals – pulse bursts that vary in duration, peak frequency and amplitude. Victory squeals were produced on 72% of marks. Sometimes after marking, or at other times during their long swims, the dolphins produced click packets. Packets typically consisted of two to 10 clicks with inter-click intervals of 7-117 ms followed by a silence of 223-983 ms. Click packets appeared unrelated with searching or marking. We suggest that the packets were used to improve signal to noise ratios for locating a boat or other distant object. Victory squeals produced when marking the targets suggest to us that the dolphins know when they have succeeded in this multipart task.

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.

We suggest how a basic physics problem becomes much richer when researchers of various disciplines converse. Our discussion explores Snell’s window from the perspective of what a dolphin might see. An aperture, Snell’s window, allows light to travel through the air-water interface. Outside this window, there is total reflection from under the water-air interface. Dolphins see through the aperture to follow our movements above the water’s surface. When dolphins look outside the window, can they see their own reflections from under the water-air interface?

For the first time, dolphins wearing video cameras were observed capturing and eating live native fish.  While freely swimming in San Diego Bay, one dolphin caught 69 resident fish, 64 demersal, 5 near surface, while the other caught 40, 36 demersal and 4 near the surface. Two other dolphins were observed capturing 135 live native fish in a sea water pool. Two additional dolphins were observed feeding opportunistically during open water sessions in the Pacific Ocean.  Notably, one of these dolphins was observed to consume 8 yellow-bellied sea snakes ( Hydrophis platurus ).  Searching dolphins clicked at intervals of 20 to 50 ms.  On approaching prey, click intervals shorten into a terminal buzz and then a squeal.  Squeals were bursts of clicks that varied in duration, peak frequency, and amplitude.  Squeals continued as the dolphin seized, manipulated and swallowed the prey.  If fish escaped, the dolphin continued the chase and sonar clicks were heard less often than the continuous terminal buzz and squeal. During captures, the dolphins’ lips flared to reveal nearly all of the teeth. The throat expanded outward.  Fish continued escape swimming even as they entered the dolphins’ mouth, yet the dolphin appeared to suck the fish right down.