Dolphins are hypothesized to deduce the swimming direction of group members by attending to the spectral pattern of whistle harmonics. This is known as the direction of movement cue hypothesis and may facilitate coordination of complex group behavior when visibility is poor. The direction of movement cue hypothesis hinges on the assumption that dolphins can discriminate between whistles with different harmonic patterns that are associated with signaler orientation. This assumption was tested with a bottlenose dolphin. Whistles were recorded from a dolphin at different azimuth positions (0° to 180° in 45° increments). Noise-free, synthetic whistles were created to mimic the direction-dependant spectral profiles of the recorded whistles. A dolphin was then tested in its ability to discriminate between the synthetic whistles using fixed level and roving level conditions. The dolphin's discrimination performance in both the fixed and roving level conditions was near 100% for whistles separated by angles greater than 45°, and near chance for 45° separations. Computer simulations of the task, along with the dolphin's performance, suggest that the dolphin's discrimination was level invariant and based on the spectral pattern of the whistles.
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September 2013
September 01 2013
Discrimination of mixed-directional whistles by a bottlenose dolphin (Tursiops truncatus)
Brian K. Branstetter;
Brian K. Branstetter
a)
National Marine Mammal Foundation
, 2240 Shelter Island Drive, #204, San Diego, California 92106
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Amy Black;
Amy Black
G2 Software Systems Inc.
, 4250 Pacific Highway, Suite 125, San Diego, California 92110
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Kimberly Bakhtiari
Kimberly Bakhtiari
G2 Software Systems Inc.
, 4250 Pacific Highway, Suite 125, San Diego, California 92110
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a)
Author to whom correspondence should be addressed. Electronic mail: branstet@gmail.com
J. Acoust. Soc. Am. 134, 2274–2285 (2013)
Article history
Received:
January 29 2013
Accepted:
June 26 2013
Citation
Brian K. Branstetter, Amy Black, Kimberly Bakhtiari; Discrimination of mixed-directional whistles by a bottlenose dolphin (Tursiops truncatus). J. Acoust. Soc. Am. 1 September 2013; 134 (3): 2274–2285. https://doi.org/10.1121/1.4816404
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