Sarasota Dolphin Research Program

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Dolphin communication studies
By Vincent Janik, PhD, SMRU, St. Andrews, UK and Laela Sayigh, PhD, WHOI

Setting up for a playback experiment during the 2009 health assessment.

The Sarasota dolphin whistle database is a unique resource of dolphin whistles, containing signature and other whistles of 232 individuals that have been recorded during brief capture-release events over the last 35 years. It contains multiple recordings of individuals that cover time spans of up to 34 years, with up to 16 recordings of each individual. There is no other dataset like it in the world, and it allows us (and others) to ask scientific questions that are otherwise not possible to address. Much of our effort goes into updating, digitizing, and making this dataset available to other researchers. Over the last few years, we have used it to address many novel questions. Most recently we investigated the temporal structure of multi-loop whistles, how dolphins recognize each other individually, and whether whistles may serve as indicators of stress. We also used the catalogue to develop a method to identify signature whistles in free-swimming dolphins, which does not require capture-release (described in the last issue of Nicks’n’Notches). We are now using this method to compare dolphin dialects all over the world. The study uses recordings from all continents to describe different dialects and to compare how genetic similarity influences whistle similarity across populations. Starting from Sarasota Bay, this will allow us to produce a world view of bottlenose dolphin communication.

During capture-release sessions we collected the last necessary data for our study on “addressing” in bottlenose dolphins. Here we compared reactions of dolphins to their own signature whistle with those they show to whistles of their relatives. A first analysis shows that they react by replying with their own whistle if they are addressed in this way, while they try to approach the speaker if they hear the whistle of a relative. Just like in previous years, we only used synthetic whistles for this study. This way we can be sure that the reaction is based on the frequency modulation patterns that the dolphin invented rather than on the voice features that every animal has due to the unique shape of its vocal tract. We have observed whistle copying interactions in wild dolphins and know that they use copying regularly. The results from our experiments in Sarasota Bay show that copying a signature whistle provides an effective way of addressing dolphins.

This work was funded by a Protect Wild Dolphins Grant to L. Sayigh and R. Wells from the Harbor Branch Oceanographic Institute Protect Wild Dolphins Program, and a Royal Society University Research Fellowship from the UK to V. M. Janik.