TY - JOUR

T1 - Narwhals react to ship noise and airgun pulses embedded in background noise

AU - Tervo, Outi M.

AU - Blackwell, Susanna B.

AU - Ditlevsen, Susanne

AU - Conrad, Alexander S.

AU - Samson, Adeline L.

AU - Garde, Eva

AU - Hansen, Rikke G.

AU - Heide-Jørgensen, Mads Peter

N1 - Publisher Copyright: © 2021 The Authors.

PY - 2021

Y1 - 2021

N2 - Anthropogenic activities are increasing in the Arctic, posing a threat to niche-conservative species with high seasonal site fidelity, such as the narwhal Monodon monoceros. In this controlled sound exposure study, six narwhals were live-captured and instrumented with animal-borne tags providing movement and behavioural data, and exposed to concurrent ship noise and airgun pulses. All narwhals reacted to sound exposure with reduced buzzing rates, where the response was dependent on the magnitude of exposure defined as 1/distance to ship. Buzzing rate was halved at 12 km from the ship, and whales ceased foraging at 7-8 km. Effects of exposure could be detected at distances > 40 km from the ship.At only a few kilometres from the ship, the received high-frequency cetacean weighted sound exposure levels were below background noise indicating extreme sensitivity of narwhals towards sound disturbance and demonstrating their ability to detect signals embedded in background noise. The narwhal's reactions to sustained disturbance may have a plethora of consequences both at individual and population levels. The observed reactions of the whales demonstrate their auditory sensitivity but also emphasize, that anthropogenic activities in pristine narwhal habitats needs to be managed carefully if healthy narwhal populations are to be maintained.

AB - Anthropogenic activities are increasing in the Arctic, posing a threat to niche-conservative species with high seasonal site fidelity, such as the narwhal Monodon monoceros. In this controlled sound exposure study, six narwhals were live-captured and instrumented with animal-borne tags providing movement and behavioural data, and exposed to concurrent ship noise and airgun pulses. All narwhals reacted to sound exposure with reduced buzzing rates, where the response was dependent on the magnitude of exposure defined as 1/distance to ship. Buzzing rate was halved at 12 km from the ship, and whales ceased foraging at 7-8 km. Effects of exposure could be detected at distances > 40 km from the ship.At only a few kilometres from the ship, the received high-frequency cetacean weighted sound exposure levels were below background noise indicating extreme sensitivity of narwhals towards sound disturbance and demonstrating their ability to detect signals embedded in background noise. The narwhal's reactions to sustained disturbance may have a plethora of consequences both at individual and population levels. The observed reactions of the whales demonstrate their auditory sensitivity but also emphasize, that anthropogenic activities in pristine narwhal habitats needs to be managed carefully if healthy narwhal populations are to be maintained.

KW - airgun

KW - arctic

KW - disturbance

KW - foraging

KW - narwhal

KW - noise

UR - http://www.scopus.com/inward/record.url?scp=85121728684&partnerID=8YFLogxK

U2 - 10.1098/rsbl.2021.0220

DO - 10.1098/rsbl.2021.0220

M3 - Journal article

C2 - 34753294

AN - SCOPUS:85121728684

VL - 17

JO - Biology Letters

JF - Biology Letters

SN - 1744-9561

IS - 11

M1 - 20210220

ER -