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

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...