Biennial Conference on the Biology of Marine Mammals, Fall 2001
Title: Human-Made Model Sound Incorporation in Captive Dolphin Whistles
Authors: Jennifer L. Miksis, Peter L. Tyack, John R. Buck

Adult dolphins have long been known to imitate synthetic whistle-like sounds, but little is known about the role of imitation in the development of whistles in young dolphins. Intensive longitudinal studies of whistle development in three captive bottlenose dolphins suggested that two of the three calves may have developed whistles similar to those produced by dolphin trainers (Tyack & Sayigh, 1997). The most distinctive feature of this trainer's whistle is that it is much less modulated in frequency than most dolphin whistles. This study presents a cross-sectional study testing whether dolphins that are born in captivity where they hear trainers' whistles develop whistles that are less frequency modulated than those of wild dolphins. Ten pairs or captive and wild dolphins were matched for age and sex. Twenty whistles were sampled from each dolphin. Several traditional acoustic features (total duration, duration minus any silent periods, etc.) were measured for each whistle, in addition to newly defined flatness parameters: total flatness ratio (percentage of whistle scored as unmodulated) and contiguous flatness ratio (duration of longest flat segment divided by total duration). The duration of wild dolphin whistles were found to be significantly longer, and the captive dolphins did have whistles that were less frequency modulated and more like the trainer's whistle. In 9/10 matched pairs, the captive dolphin had a significantly higher total flatness ratio and in 8/10 pairs had significantly higher contiguous flatness ratios. These results suggest that captive born dolphins can incorporate features of artificial acoustic models made by humans into their signature whistles.

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