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Colvin Winner Tara Thean ’13 Explores How Bottlenose Dolphins Learn Their Signature Whistles

Tara Thean
Tara Thean '13, 2012 Colvin Award Winner.

In May 2012, Ecology and Evolutionary Biology major Tara Thean '13 received the Becky Colvin Memorial Award to support her research examining the signature whistles of dolphins and how their unique form of communication might inform the understanding of animal communication in general. Her senior thesis, completed this past spring, was titled "Signature Whistle Models in Bottlenose Dolphins, Tursiops truncatus."

Below, Thean describes her research, how the Colvin Award made such an ambitious project possible, and how this project impacted her desire to attend Cambridge University in the fall of 2013 to study mammal evolution.

Please describe your senior thesis project.

Broadly, my project is an investigation into two questions that have been of interest to scientists for many decades: how animals communicate with one another, and how genetics and the environment interact to produce particular behavioral traits. Specifically, I am studying how bottlenose dolphins learn their signature whistles.

What is particularly intriguing about this area of study?

Tara Thean
A bottlenose dolphin swimming in Sarasota Bay, Florida, wearing a tag that records its vocalizations.  Photo: taken under NMFS Scientific Research Permit No. 15543.

Signature whistles are to dolphins what names are to humans. They are specific to each dolphin and encode identity information, referred to by one of my mentors "as recognizable as a leitmotif in a Wagnerian opera." Dolphins use these whistles to call one another and maintain cohesion within their groups. I'm interested in how young dolphin learning influences what signature whistle it eventually selects. It is already known that bottlenose dolphins have a tremendous capacity for imitating sound. Captive dolphins, for example, can incorporate portions of their trainers' whistles into their own signature whistles. There is some evidence that bottlenose dolphins copy other dolphins' whistle modulation patterns and modify them to produce their own signals. Moreover, it is also known that bottlenose dolphins maintain very tight associations with certain community members, like their mothers, while simultaneously living in very fluid societies. Given all these chunks of information, it seems possible that a dolphin has the capacity to imitate the signature whistles of particular community members to form its own whistles and that it might experience some adaptive advantage from doing so with respect to its complex social structure, such as the maintenance of kinship bonds.

How did the Colvin Award support your research?

The Colvin Award enabled me to travel to Sarasota, Florida in the summer of 2012 to participate in a bottlenose dolphin health assessment with the Sarasota Dolphin Research Program. It was there that I got to see and work with wild dolphins. I worked with vets and scientists to collect information about the life histories, behavior, and health of these animals, including recordings of their signature whistles that were useful for my own project. I was also able to write about this experience in a series of posts for the New York Times.

Later in the year, the funds supported my stay at the Woods Hole Oceanographic Institution (WHOI) in Massachusetts where I analyzed my data with the guidance of a wonderful marine mammal research specialist. I also gained access to a large trove of data on the Sarasota dolphin community dating back to the nineteen seventies.

How did you compile your thesis data?

Tara Thean
Thean and a Woods Hole Oceanographic Institution postdoctoral research fellow, Frants Jensen, searching for tagged dolphins by using handheld trackers that detect beeping signals emitted from the tags.

My thesis data come from the wild bottlenose dolphin community I visited in Sarasota, Florida, and from several zoo facilities. I sought to identify a relationship between the strength of a calf's association with other dolphins during the first year of its life, and the similarity of their whistles. I aimed to understand this relationship in both wild dolphins and those in captivity. It is likely that the functional role of signature whistles changes in captive conditions. For example, they appear to have a reduced need to maintain group cohesion in captive contexts – after all, they are all in the same tank and are not going to lose sight of each other. I also tried to address some of the methodological concerns regarding whistle similarity analysis, using both human observer and automated signal categorization methodologies.

Did your project change once you began the research?

The aims of my project did not change greatly, but my understanding of the methodologies in this field certainly did. Traveling to Sarasota and actually seeing and working with wild dolphins up close was invaluable to my understanding about the complexities of the data. I also began to better understand the complexities of using automated procedures for studying sound perception. There are still things that computers cannot quite do.

What surprised you the most over the course of this project?

I underestimated how complex it is to divide animal signals into categories that are biologically meaningful, especially using automated methods. I can compare one signature whistle to another in any number of ways, but whether or not I'm comparing them the same way that a dolphin brain does, that is a different question.

What are some of the most valuable lessons you learned over the course of this project?

Tara Thean
Another outboard-powered vessel carrying SDRP researchers.

Excluding specific lessons about signature whistle studies, I would say there are two. First, don't be shy about asking others in your field for advice. Most people are extremely willing to help, and their experience and insight can really guide your research path. Second, be extremely vigilant about consistency in recording data. Small inconsistencies can be a huge inconvenience and source of confusion later on.

Why is your research important, and in what ways do you hope it will have an impact beyond the campus?

Understanding what cues bottlenose dolphins take in learning their signature whistles will shed light on several facets of bottlenose dolphin communication, such as how environmental factors affect development and why bottlenose dolphins use signature whistles at all. Comparing wild and captive bottlenose dolphins will help us understand how human care conditions influence animal communication and social behavior. I also hope that my research will interest not just me and other scientists, but anyone who has watched movies or read books like The Lion King, Charlotte's Web, and Animal Farm and thought at all about what animals are conveying when they communicate.

Were you able to accomplish what you originally intended?

I was able to accomplish most of what I originally intended, largely because of the contributions of my mentors - Princeton ecology and environmental biology professor, James Gould, through his extensive knowledge of statistics; Laela Sayigh of WHOI with her experience with bottlenose dolphin field research and generosity with data; and Arik Kershenbaum from the University of Tennessee for his expertise in automated categorization methods and computer programming. I cannot overstate the importance of finding good mentors to work with.

In what ways has this project influenced your plans post graduation?

It has been incredible to have ownership over such a specific project. I loved learning so much about a small pocket of the marine world. This experience has affirmed for me that I want to continue doing science after Princeton. I hope to attend Cambridge University this fall to study biological sciences at the graduate level, hopefully exploring anatomical adaptations for hearing in aquatic vertebrates. I ultimately hope to find work as a science writer.

What advice would you give this year's Colvin winner?

It is really easy in the depths of writing your thesis to get tangled up in data and lose sight of the bigger picture. Make yourself remember why you found this question interesting in the first place, and don't forget that you are doing something interesting that adds a piece, however small, to what we know about nature.

Read Tara's feature article for the research magazine Oceanus: Caller IDs for Whales: Crowd-sourcing helps sort marine mammal vocalizations.

In addition to Tara Thean, ecology and evolutionary biology major Abby Hewett '13 was also awarded Colvin funds last spring. Both students will graduate with certificates in environmental studies in June 2013. Hewett's research was featured in an earlier story. The Becky Colvin Memorial Award supports summer field research projects in support of the senior thesis. The award was established in 1995 by Dr. and Mrs. Robert Colvin in memory of their daughter, Becky Colvin '95. Becky was an ecology and evolutionary biology major who was very interested in field research. Students are selected to receive the Colvin Prize by competitive application in the spring of their junior year.

Additional information about the Becky Colvin Memorial Award and prior recipients of the prize is available on PEI's website.