[MARMAM] New paper on fast click series by Risso’s dolphins (Patricia Arranz)
patty.arranz at gmail.com
Sun Jul 10 10:36:52 PDT 2016
We are excited to announce the publication of a behavioral study to
discriminate fast-click series in Risso’s dolphins using digital tags.
For those interested, the title and abstract are cited below:
The Journal of Experimental Biology: doi: 10.1242/jeb.144295
Discrimination of fast click series produced by tagged Risso's
griseus*) for echolocation or communication. P. Arranz, S. L. DeRuiter, A.
K. Stimpert, S. Neves, A. S. Friedlaender, J. A. Goldbogen, F. Visser, J.
Calambokidis,B. L. Southall, P. L. Tyack
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.
PDF available upon request to parranz at st-andrews.ac.uk
On behalf of the authors,
Dr Patricia Arranz
Sea Mammal Research Unit
Scottish Oceans Institute
School of Biology
University of St Andrews
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