Vertical sonar beam width and scanning behavior of wild belugas (Delphinapterus leucas) in West Greenland

Marie J. Zahn*, Kristin L. Laidre, Peter Stilz, Marianne H. Rasmussen, Jens C. Koblitz

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Echolocation signals of wild beluga whales (Delphinapterus leucas) were recorded in 2013 using a vertical, linear 16-hydrophone array at two locations in the pack ice of Baffin Bay, West Greenland. Individual whales were localized for 4:42 minutes of 1:04 hours of recordings. Clicks centered on the recording equipment (i.e. on-axis clicks) were isolated to calculate sonar parameters. We report the first sonar beam estimate of in situ recordings of wild belugas with an average -3 dB asymmetrical vertical beam width of 5.4◦, showing a wider ventral beam. This narrow beam width is consistent with estimates from captive belugas; however, our results indicate that beluga sonar beams may not be symmetrical and may differ in wild and captive contexts. The mean apparent source level for on-axis clicks was 212 dB pp re 1 μPa and whales were shown to vertically scan the array from 120 meters distance. Our findings support the hypothesis that highly directional sonar beams and high source levels are an evolutionary adaptation for Arctic odontocetes to reduce unwanted surface echoes from sea ice (i.e., acoustic clutter) and effectively navigate through leads in the pack ice (e.g., find breathing holes). These results provide the first baseline beluga sonar metrics from free-ranging animals using a hydrophone array and are important for acoustic programs throughout the Arctic, particularly for acoustic classification between belugas and narwhals (Monodon monoceros).

Original languageEnglish
Article numbere0257054
Pages (from-to)e0257054
JournalPLoS ONE
Volume16
Issue number9 September
DOIs
Publication statusPublished - 9 Sep 2021

Bibliographical note

Publisher Copyright:
© 2021 Zahn et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Other keywords

  • Animals
  • Beluga Whale/physiology
  • Echolocation
  • Geography
  • Greenland
  • Sound

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