Journal of the Acoustical Society of America , Vol. 112, No. 2, August 2002. pp. 728-739.
Title: Captive dolphins, Tursiops truncatus , develop signature whistles that match acoustic features of human-made model sounds
Authors: Jennifer L. Miksis, Peter L. Tyack, and John R. Buck

This paper presents a cross-sectional study testing whether dolphins that are born in aquarium pools where they hear trainers' whistles develop whistles that are less frequency modulated than those of wild dolphins. Ten pairs of captive and wild dolphins were mateched for age and sex. Twenty whistles were sampled from each dolphin. Several traditional acoustic features (total duration, duration minus and 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 durations of wild dolphin whisltes were found to be significantly longer, and the captive dolphins had whistles that were less frequency modulated and more like the trainers' whistles. Using a standard t-test, the captive dolphin had a significantly higher total flatness ratio in 9/10 matched pairs, and in 8/10 pairs the captive dolphin had significantly higher contiguous flatness ratio. 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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