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J Acoust Soc Am. 2017 Feb;141(2):737. doi: 10.1121/1.4974858.

Acoustic differentiation of Shiho- and Naisa-type short-finned pilot whales in the Pacific Ocean.

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Scripps Institution of Oceanography, University of California-San Diego, La Jolla, California 92038, USA.
San Diego State University, San Diego, California 92182, USA.
Cascadia Research Collective, Olympia, Washington 98501, USA.
Woods Hole Oceanographic Institution, Massachusetts Institute of Technology, Woods Hole, Massachusetts 02543, USA.
National Oceanic and Atmospheric Administration (NOAA)-National Marine Fisheries Service (NMFS) Southwest Fisheries Science Center, La Jolla, California 92037, USA.


Divergence in acoustic signals used by different populations of marine mammals can be caused by a variety of environmental, hereditary, or social factors, and can indicate isolation between those populations. Two types of genetically and morphologically distinct short-finned pilot whales, called the Naisa- and Shiho-types when first described off Japan, have been identified in the Pacific Ocean. Acoustic differentiation between these types would support their designation as sub-species or species, and improve the understanding of their distribution in areas where genetic samples are difficult to obtain. Calls from two regions representing the two types were analyzed using 24 recordings from Hawai'i (Naisa-type) and 12 recordings from the eastern Pacific Ocean (Shiho-type). Calls from the two types were significantly differentiated in median start frequency, frequency range, and duration, and were significantly differentiated in the cumulative distribution of start frequency, frequency range, and duration. Gaussian mixture models were used to classify calls from the two different regions with 74% accuracy, which was significantly greater than chance. The results of these analyses indicate that the two types are acoustically distinct, which supports the hypothesis that the two types may be separate sub-species.


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