Narwhals’ acoustic behavior described using audio tagging
The clicking, buzzing and calling behavioral patterns of elusive East Greenland narwhals have been described thanks to in-depth recordings, in a study published June 13, 2018 in the open-access journal PLOS ONE by Susanna Blackwell from Greeneridge Sciences, Incorporated, United States of America, and colleagues.
Climate change is predicted to increase human activity in the Arctic, including remote areas of Greenland where narwhals live. However, little is known about the whales' acoustic behavior or their reactions to anthropogenic sounds. Previous studies have mostly relied upon underwater microphones, which are limited in their ability to record spatial and temporal variations.
The author of the present study captured six narwhals in East Greenland and tagged them with acoustic and satellite instruments. The researchers were able to record 533 hours of audio and analyzed their recordings to describe how the whales' acoustic behavior varied by location and time.
The researchers found that the narwhals produced three types of sounds: clicks, buzzes and calls. Clicks and buzzes were produced during echolocation for feeding, while the authors presume that calls served communication purposes. Calls were typically produced at depths of less than 100 meters, with over half being produced less than 7m from the surface. However, buzzes were produced at much greater depths of between 350 and 650 meters. The authors even used their recordings to identify a likely preferred feeding area: a particular fjord which had especially high buzzing rates. They also noted a possible stress response to capture and tagging: the narwhals were silent afterwards for around a day, reinforcing the need to record over larger timespans.
While much remains unknown about narwhal acoustics, this work provides new insights into where and when these elusive whales produce sound and could establish a baseline to help assess future impacts of climate and anthropogenic changes on narwhals.
Susanna Blackwell says: "Wide-scale changes are taking place in the Arctic, with warmer temperatures leading to shrinking summer ice coverage. More ice-free water means easier access for vessels and industrial operations, such as exploration for oil and gas. The inhospitable pack-ice environment that is narwhals' home for much of the year has for millennia kept them in relative isolation–even from biologists. Now new amazing tools allow us to take a multi-day, virtual ride on the back of a narwhal!"
In your coverage please use this URL to provide access to the freely available article in PLOS ONE: http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0198295
Citation: Blackwell SB, Tervo OM, Conrad AS, Sinding MHS, Hansen RG, Ditlevsen S, et al. (2018) Spatial and temporal patterns of sound production in East Greenland narwhals. PLoS ONE 13(6): e0198295. https://doi.org/10.1371/journal.pone.0198295
Funding: Funding support was provided to MPHJ by the Greenland Institute of Natural Resources (http://www.natur.gl), the Greenland Ministry of Education, Church, Culture & Gender Equality (http://naalakkersuisut.gl/da/Naalakkersuisut/Departementer/Uddannelse-Kultur-Forskning-ogKirke/Uddannelse-og-Forskning/Forskning), the Danish Cooperation for the Environment in the Arctic (DANCEA, http://mst.dk/kemi/kemikalier/arktis/dancea-miljoestoette-til-arktis/) under the Danish Ministry of Environment, the Carlsberg Foundation (grant number 2013_01_0289 and CF14-0169, http://www.carlsbergfondet.dk/da), and the Bureau of Minerals and Petroleum in Greenland (https://www.govmin.gl/petroleum). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. SBB and ASC are employed by Greeneridge Sciences, Inc., an independent, commercial contracting company that performs studies of the interactions between underwater sounds and marine vertebrates. Greeneridge Sciences, Inc., provided support in the form of salaries for SBB and ASC, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of these authors are articulated in the "author contributions" section.
Competing Interests: SBB and ASC are employed by Greeneridge Sciences, Inc. There are no patents to declare, but the AcousondeTM tag used in this study is manufactured by Acoustimetrics, a brand of Greeneridge Sciences, Inc. This does not alter our adherence to PLOS ONE policies on sharing data and materials.
<h4>Related Journal Article</h4>http://dx.doi.org/10.1371/journal.pone.0198295