Highly directional sonar beam of narwhals (Monodon monoceros) measured with a vertical 16 hydrophone array

Recordings of narwhal (Monodon monoceros) echolocation signals were made using a linear 16 hydrophone array in the pack ice of Baffin Bay, West Greenland in 2013 at eleven sites. An average-3 dB beam width of 5.0 degrees makes the narwhal click the most directional biosonar signal reported for any s...

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Bibliographic Details
Published in:PLOS ONE
Main Authors: Koblitz, J., Stilz, P., Rasmussen, M., Laidre, K.
Format: Article in Journal/Newspaper
Language:unknown
Published: 2016
Subjects:
Arctic
Baffin Bay
Greenland
Baffin
Monodon monoceros
narwhal*
Sea ice
toothed whales
Online Access:http://hdl.handle.net/21.11116/0000-0005-A4EA-A
Description
Summary:Recordings of narwhal (Monodon monoceros) echolocation signals were made using a linear 16 hydrophone array in the pack ice of Baffin Bay, West Greenland in 2013 at eleven sites. An average-3 dB beam width of 5.0 degrees makes the narwhal click the most directional biosonar signal reported for any species to date. The beam shows a dorsal-ventral asymmetry with a narrower beam above the beam axis. This may be an evolutionary advantage for toothed whales to reduce echoes from the water surface or sea ice surface. Source level measurements show narwhal click intensities of up to 222 dB pp re 1 mu Pa, with a mean apparent source level of 215 dB pp re 1 mu Pa. During ascents and descents the narwhals perform scanning in the vertical plane with their sonar beam. This study provides valuable information for reference sonar parameters of narwhals and for the use of acoustic monitoring in the Arctic.

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