Dolphins Signal Success by Producing a Victory Squeal

Abstract

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.

Evaluating Potential Cetacean Welfare Indicators from Video of Live Stranded Long-Finned Pilot Whales (Globicephala melas edwardii)

“…Interestingly, vocalisation during filming was rare and was only heard where focal animals were calves or adults in the presence of a calf, suggesting a possible maternal–filial connection. Previous studies suggest vocalisations are linked to cetacean welfare state in captive situations [ 85 , 86 , 87 ] and may affect epimeletic behaviour provided to wild distressed conspecifics [ 88 ]. Accordingly, we recommend additional data collection at stranding events to further assess the validity of vocalisations as a welfare indicator and to compile a comprehensive vocal repertoire for strandings.…”

Sights and sounds of dolphins, Tursiops truncatus, preying on native fish of San Diego Bay and offshore in the Pacific Ocean

“…To observe dolphins catching live fish, we used cameras attached to the animals' harness (Figure 1 A.) similar to our previous studies (Ridgway et al 2015(Ridgway et al , 2018Dibble et al 2016). Our observations were of six T. truncatus of different ages (Table 1).…”

“…To observe dolphins catching live fish, we used cameras attached to the animals' harness (Figure 1 A.) similar to our previous studies (Ridgway et al 2015(Ridgway et al , 2018Dibble et al 2016) We recorded video and sound from four female and two male T. truncatus (Table 1) as they caught and ate live prey. All animals wore harnesses to which we attached cameras so that the dolphins' fore bodies and the water ahead was clearly visible (Figure 1 A).…”

“…In previous studies we did simultaneous recordings with a broadband hydrophone system (125 kHz bandwidth) and the same cameras used here. In that study, the timing of the dolphin's sounds were accurately represented by the camera even though recording a limited 16 kHz bandwidth (Ridgway et al 2015, Dibble et al 2016. Dolphin S was recorded during 15 periods of about 50 minutes each.…”

“…Sounds and head jerks of toothed whales have been recorded as they captured live prey (Johnson et al 2006; Jensen et al 2009; Wisniewska et al 2015, 2016). Sounds and video have also been recorded from dolphins finding and consuming dead fish (Wisniewska et al 2014; Ridgway et al 2014, 2015; Dibble et al 2016; Ladegaard et al 2017). However, sound and video together have never been used to observe behavior of dolphins and of the live fish they capture and consume.…”