Discrimination of fast click series produced by tagged Risso’s dolphins (Grampus griseus) for echolocation or communication

P. Arranz Alonso, S. L. DeRuiter, A. K. Stimpert, Silvana Neves, A. S. Friedlaender, J. A. Goldbogen, F. Visser, J. Calambokidis, B. L. Southall, P. L. Tyack

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Early studies that categorized odontocete pulsed sounds had few means of discriminating signals used for biosonar-based foraging from those used for communication. This capability to identify the function of sounds is important for understanding and interpreting behavior; it is also essential for monitoring and mitigating potential disturbance from human activities. Archival tags were placed on free-ranging Grampus griseus to quantify and discriminate between pulsed sounds used for echolocation-based foraging and those used for communication. Two types of rapid click-series pulsed sounds, buzzes and burst pulses, were identified as produced by the tagged dolphins and classified using a Gaussian mixture model based on their duration, association with jerk (i.e., rapid change of acceleration), and temporal association with click trains. Buzzes followed regular echolocation clicks and coincided with a strong jerk signal from accelerometers on the tag. They consisted of series averaging 359 ± 210 (mean ± SD) clicks with an increasing repetition rate and relatively low amplitude. Burst pulses consisted of relatively short click series averaging 45 ± 54 clicks with decreasing repetition rate and longer inter-click interval that were less likely to be associated with regular echolocation and the jerk signal. These results suggest that the longer, relatively lower amplitude, jerk-associated buzzes are used in this species to capture prey, mostly during the bottom phase of foraging dives, as seen in other odontocetes. In contrast, the shorter, isolated burst pulses that are generally emitted by the dolphins while at or near the surface are used outside of a direct, known foraging context.
Original languageEnglish
Pages (from-to)2898-2907
Number of pages10
JournalJournal of Experimental Biology
Issue number18
Early online date8 Jul 2016
Publication statusPublished - 21 Sept 2016


  • Biosonar
  • Pulsed sound
  • Buzz
  • Burst pulse
  • Jerk
  • Foraging behavior


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