| Summary: | Author Posting. © Acoustical Society of America, 2008. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 123 (2008): 1753-1762, doi:10.1121/1.2828210. Blainville's beaked whales (Mesoplodon densirostris) use broadband, ultrasonic echolocation signals with a −10 dB bandwidth from 26 to 51 kHz to search for, localize, and approach prey that generally consist of mid-water and deep-water fishes and squid. Although it is well known that the spectral characteristics of broadband echoes from marine organisms vary as a function of size, shape, orientation, and anatomical group, there is little evidence as to whether or not free-ranging toothed whales use spectral cues in discriminating between prey and nonprey. In order to study the prey-classification process, a stereo acoustic tag was deployed on a Blainville's beaked whale so that emitted clicks and the corresponding echoes from targets in the water could be recorded. A comparison of echoes from targets apparently selected by the whale and those from a sample of scatterers that were not selected suggests that spectral features of the echoes, target strengths, or both may have been used by the whale to discriminate between echoes. Specifically, the whale appears to favor targets with one or more nulls in the echo spectra and to seek prey with higher target strengths at deeper depths. Field work was supported by the U.S. National Oceanographic Partnership Program, the U.S. Office of Naval Research, and the Canary Islands government. Analysis of the data was supported by the Office of the Oceanographer of the U.S. Navy, The Academic Programs Office at the Woods Hole Oceanographic Institution and the Danish Natural Science Research Council through a Steno scholarship to Peter T. Madsen.
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