Signature whistle productions, development, and perception in free-ranging bottlenose dolphins

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Mandy Hill (Creator)
Institution
The University of North Carolina Wilmington (UNCW )
Web Site: http://library.uncw.edu/
Advisor
Laela Sayigh

Abstract: Data from behavioral observations and acoustic recordings of free-ranging bottlenose dolphins (Tursiops truncatus) were analyzed to determine whether signature whistles occur in the wild, and to determine when whistle crystallization occurs in calves. The study animals were part of a resident community of bottlenose dolphins in the waters near Sarasota, Florida. Three mother-calf pairs and their associates were recorded for a total of 141.25 hours between May and August of 1994 and 1995. Each whistle was conservatively classified into one of four categories: signature, probable signature, upsweep, or other. Overall whistle production varied significantly with both activity and group size. Whistles occurred more frequently than expected during socializing and in groups of over five dolphins, and occurred less frequently than expected during travelling and in groups of two dolphins. Signature and probable signature whistles made up approximately 52% of all whistles produced by these free-ranging bottlenose dolphins. Each of the three calves studied developed its whistle prior to four months of age. Each mother’s signature whistle comprised approximately 3% of the whistles recorded during the first year of her calf’s life, regardless of social or auditory environment, which varied greatly among the calves. One calf developed a signature whistle similar to that of its mother. To evaluate whether certain acoustic features of whistles are perceptually important to dolphins, 44 playback experiments were conducted with temporarily captured dolphins near Sarasota, Florida in June of 2000 and 2001. Response measures included number of head turns toward or away from the speaker, echolocation bouts, and whistles. In a modified habituation-dishabituation design, habituation to the first stimulus did not occur. Additionally, there were low overall response rates to most synthetic stimuli. There were no significant differences in responses to whistles containing differing numbers of loops or differing contours, with the exception that head turn rates were higher in response to modified synthetic upsweeps than to several other synthetic stimuli. In addition, whistle response rates were significantly higher to known, natural whistle stimuli than to synthetic upsweeps. These results suggest that natural whistles and modified upsweeps contain whistle features not adequately conveyed by other synthetic stimuli.

Additional Information

Publication
Thesis
A Thesis Submitted to the University of North Carolina Wilmington in Partial Fulfilment of the Requirements for the Degree of Master of Science
Language: English
Date: 2009
Keywords
Animal sounds, Bottlenose dolphin--Behavior, Bottlenose dolphin--Research, Sound production by animals
Subjects
Animal sounds
Sound production by animals
Bottlenose dolphin -- Behavior
Bottlenose dolphin -- Research