The same algorithm used to find tunes in music retrieval systems has been successfully used to identify the signature whistles of dolphins, according to research done at the National Institute for Mathematical and Biological Synthesis at UT.
Published this week in the journal PLOS ONE, the finding provides a new time-saving technique for research into dolphin communication and social behavior.
Bottlenose dolphins, in particular, recognize each other by the sound of each animal’s “signature” whistle, which each dolphin develops at a young age. Bottlenose dolphins appear to show preference to the signature whistles of familiar individuals. Scientists have found that dolphins use the signature whistles to foster and maintain group cohesion.
Until now, individual dolphin whistles have been classified by examining a spectrograph, which visually represents the spectrum of its frequencies. But the method is time-consuming, requires more data than might be necessary, and is subject to human error.
The study describes a new method that uses an algorithm based on the Parsons code, which has been used extensively in computerized retrieval of tunes from music databases. Instead of looking at the precise variation in frequency, the Parsons code only considers whether the pitch goes up, down, or stays the same.
The researchers examined 400 signature whistles from twenty different dolphins. The new algorithm did well at assigning signature whistles to individual animals, helping scientists to classify the tested whistles quickly and efficiently.
“The Parsons code is a robust way to compare dolphins’ signature whistles because it is able to home in on the variation in frequency that actually matters. It discards the information that isn’t useful for the analysis,” said lead author Arik Kershenbaum, a postdoctoral fellow at NIMBioS.
Being able to identify information in signature whistles is important for assessing the similarity of whistles and studying how social behavior influences the development of these learned calls.
“Cetacean vocalizations are highly varied and presumably serve varied functions. So determining what aspects of the vocalizations hold information is crucial to be able to classify them and to be able to understand their meaning,” Kershenbaum said.
Watch a video about the research below.
View an animation of the sound frequencies of four signature whistles from four different dolphins. The spectrograph visually displays the differences in the frequencies, but in a new study, scientists have developed a more efficient method for analyzing the unique “tune” of a dolphin’s signature whistle. (Animation credit: Arik Kershenbaum.)
NIMBioS brings together researchers from around the world to collaborate across disciplinary boundaries to investigate solutions to basic and applied problems in the life sciences. NIMBioS is sponsored by the National Science Foundation, the US Department of Homeland Security, and the US Department of Agriculture, with additional support from UT.