Bottlenose dolphins produce a variety of sounds, although most research on dolphin communication has focused on their individually distinctive signature whistles. Development of these whistles is a complex and variable process that involves learning. The signature whistle usually develops within the first year of life, and then appears to remain stable for many years. However, adult females tend to produce whistles with greater bandwidth and frequency modulation than do younger animals. Dr. Sayigh will attempt to document quantitatively this apparent occurrence of vocal modification in adult bottlenose dolphins. She also will study the functional role (if any) that such modification may play in the natural communication system of these animals. Selection may have favored any modification of the signature whistle that facilitates mother-offspring recognition, given the large investment by dolphin mothers in their offspring. To quantify the apparent age difference in signature-whistle structure, Dr. Sayigh will utilize a large library of whistles recorded from dolphins during temporary-capture-and-release projects in Sarasota, Florida. Whistles will be analyzed using quantitative techniques of acoustic and statistical analysis, including the acoustic-feature-extraction program ACOUSTAT. Playback experiments will be conducted in Sarasota to test whether or not synthetic whistles with contours similar to those of the mothers' whistles but with greater bandwidth and frequency modulation are more salient to young dolphins than are the actual whistles of the mothers. The quantitative-analysis techniques that Dr. Sayigh learns during this work will be used in future research on whistle development in free-ranging bottlenose dolphins.
