During capture-release sessions in 2012, we carried out playback experiments designed to determine the feasibility of using the habituation/dishabituation playback design to study whistle perception.
This type of experiment involves playing back a series of one whistle type (e.g., a signature whistle), for a long enough time until the target dolphin stops responding to it (habituates). We then play back another whistle type.
If the target dolphin responds to the 2nd whistle type (dishabituates), this indicates that it perceives the 2nd whistle as a different whistle, whereas if no dishabituation occurs, it indicates that the dolphin perceives the 2nd whistle as the same as the 1st whistle.
Our ultimate goal is to use this paradigm to look at whether dolphins discriminate between signature whistles and signature whistle copies produced by another dolphin. In 2012 we simply played back two very different whistles, under the assumption that if we do not see predictable dishabituation in such a case, then we should not pursue this experimental design for more subtle discriminations. Analysis of these experiments is currently underway but we can already see there is good potential for using this paradigm. We hope that in future playback experiments we will be able to test whether dolphins can discriminate among “original” vs. “copied” signature whistles. Our ultimate goal is to carry out playbacks with free-swimming, tagged dolphins (see article by Peter Tyack et al.) to study how whistle copies function in the natural communication system of dolphins.
We continue to build up the Sarasota dolphin whistle database, which currently contains signature and other whistles from more than 250 individuals that have been recorded during brief capture-release events over the last 35 years. The database contains multiple recordings of individuals that cover time spans of up to 34 years, with up to 16 recordings of each individual.
Using the whistle database, this past year we began a large-scale study of signature whistle development, with Princeton University student Tara Thean. Tara’s senior thesis is focusing on social influences on calf vocal development. We have a sample size of more than 100 calves that have been recorded during capture-release, and we are comparing them to the whistles of their associates during their first year of life, thanks to the unique, large, long-term photo-identification database of the SDRP. We are also examining factors such as sex, number of associates, and average group size, among others, as possible influences on vocal development.
This article was published on page 13 in the January 2013 Nicks n Notches.