Abstract

Dolphins make sound to find their way, to communicate, and most importantly to catch food. We hear sounds after dolphins catch fish. When a trainer's whistle signals that a dolphin will get a fish for a correct response, we often hear similar sounds after the whistle. For a long time, we have called these after fish catch and after whistle sounds victory squeals. These calls have reminded us of a child's squeal of delight. Victory squeals are pulse bursts that vary in duration, peak frequency, and amplitude. They are a reflection of dolphin emotions. Victory squeals are also food calls that may communicate to other dolphins about food (You can hear these sounds at our poster).

Figure 1. We habituated dolphins to accept a small camera attached to the melon with a suction cup so that approach to the fish, capture, and departure can be recorded

Figure 2. A dolphin with the camera approaches a fish and then eats it The upper inset shows the spectrogram of sounds as the dolphin approaches and catches the fish. The thin white line through the spectrogram about one-fifth the way from the left shows where the current still picture was taken from the video. The camera on the dolphin's melon is about 50 cm from the fish. The sound changes left to right as the dolphin approaches the fish. First, we hear echolocation pulses, then the terminal buzz and then the longest component the victory squeal, which we think expresses the dolphin's emotion. The squeal may also be a food call signaling other dolphins of the presence of food.

Figure 3. Three Navy bottlenose dolphin moms with their calves - Summer 2014 Food calls shown here were recorded from dolphins also in our population. Dolphins in this population live about 50% longer than those in the wild.

Acknowledgements

We thank the trainers who worked with dolphins employed in our studies. Jennifer Stanley, Leah Crafton, and Courtney Luni were especially helpful.

References

1.  Ridgway S, Moore PW, Carder DA, Romano TA. Feeding buzz components of dolphins and belugas forward shift during associative learning revealing a likely connection to reward expectation, pleasure, and brain dopamine activation. J Exp Biol. 2014;217:2910–2920 doi:10.1242/jeb.100511.

2.  Venn-Watson S, Jensen E, Ridgway S. Advancements in medicine, high annual survival rates, and increasing longevity for Navy bottlenose dolphins (Tursiops truncatus), 2003–2013. J Am Vet Med Assoc. 2015 (In Press).