02009nas a2200181   4500008004100000022001400041245013400055210006900189260001600258300001400274490000800288520140200296100002001698700001601718700002301734700001901757856005101776       2018                        eng d  a0001-496600aVariability of the inter-pulse interval in sperm whale clicks with implications for size estimation and individual identification0 aVariability of the interpulse interval in sperm whale clicks wit  cJan-07-2018  a365 - 3740 v1443 a<p>Sperm whales generate multi-pulsed clicks for echolocation and communication with an inter-pulse interval (IPI) determined by the size of their hypertrophied sound producing nose. The IPI has therefore been used to estimate body size and distinguish between individuals, and it has been hypothesized that conspecifics may use IPIs to recognize each other. However, the degree to which IPIs vary within individuals has not explicitly been tested, and therefore the inherent precision of this measure and its applicability for size estimation for researchers and sperm whales alike remain unknown. Here, the variability in IPI from both animal-borne Dtags and far-field recordings from echolocating and communicating sperm whales is quantified. Three different automatic methods (envelope, cepstrum, and cross-correlation) are tested and it is found that the envelope approach results in the least dispersion. Furthermore, it is shown that neither growth, depth, nor recording aspect fully explains the observed variability among clicks recorded from the same individual. It is proposed that dynamics in the soft structures of the nose are affecting IPIs, resulting in a variation of approximately 0.2&thinsp;ms. Therefore, it is recommended that this variation be considered in IPI studies and that IPIs may have limited functionality as an identity cue among large groups of conspecifics.</p>
1 aBøttcher, Anne1 aGero, Shane1 aBeedholm, Kristian1 aWhitehead, Hal  uhttp://asa.scitation.org/doi/10.1121/1.5047657