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.
Susanna Blackwell from Greeneridge Sciences, Incorporated, 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. Some of their recordings are available below for listening.
Balder Conference: social interaction between several narwhals
Eistla regular clicks with echoes: female narwhal echolocating while on a foraging dive
Freya burst pulse with running water: female narwhal producing a “burst pulse” with sounds of running water from a melting glacier in the background
Frida triple trumpet: call by female Frida
Helge Conference: social interaction between several narwhals <= good one!
Thora Conference: social interaction between several narwhals
Thora four burst pulses A: four consecutive burst pulses by female Thora. Between the calls you can hear her fluke strokes as she is swimming
Thora four burst pulses B: four consecutive burst pulses by female Thora. Calls more closely spaced than previous sample.
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.
Reference: 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
Image Credit: Susanna Blackwell