Changes in climate are rapidly modifying the Arctic environment. As a result, human activities—and the sounds they produce—are predicted to increase in remote areas of Greenland, such as those inhabited by the narwhals (Monodon monoceros) of East Greenland. Meanwhile, nothing is known about these whales’ acoustic behavior or their reactions to anthropogenic sounds. This lack of knowledge was addressed by instrumenting six narwhals in Scoresby Sound (Aug 2013–2016) with Acousonde™ acoustic tags and satellite tags. Continuous recordings over up to seven days were used to describe the acoustic behavior of the whales, in particular their use of three types of sounds serving two different purposes: echolocation clicks and buzzes, which serve feeding, and calls, presumably used for social communication. Logistic regression models were used to assess the effects of location in time and space on buzzing and calling rates. Buzzes were mostly produced at depths of 350–650 m and buzzing rates were higher in one particular fjord, likely a preferred feeding area. Calls generally occurred at shallower depths (<100 m), with more than half of these calls occurring near the surface (<7 m), where the whales also spent more than half of their time. A period of silence following release, present in all subjects, was attributed to the capture and tagging operations, emphasizing the importance of longer (multi-day) records. This study provides basic life-history information on a poorly known species—and therefore control data in ongoing or future sound-effect studies.

Comparison of behavioural similarities between subpopulations of species that have been isolated for a long time is important for understanding the general ecology of species that are under pressure from large‐scale changes in habitats. Narwhals (Monodon monoceros) east and west of Greenland are examples of separated populations that, in different ocean parts, will be coping with similar anthropogenic and climate‐driven habitat alterations. To study this, 28 narwhals from the Scoresby Sound fjord system were tracked by satellite in 2010–2013. The average duration of contact with the whales was 124 days with one tag lasting 305 days and one whale recaptured <1 km from its tagging site 366 days later. All whales exhibited the same migratory pattern. The whales departed from the summering grounds in Scoresby Sound in September and arrived at the edge of the continental shelf by November. Here, they stayed through May–June and conducted daily dives to the mesopelagic zone at ∼1000 m depth. Despite the isolation by the landmass of Greenland and the genetic differentiation from other narwhal populations, there is still a remarkable similarity not just in behavioural traits like phenology of migrations and movements in relation to sea ice formation, but also in site fidelity, diving behaviour, feeding ecology, habitat selection, daily travel speed and even potential conflicts with fisheries for Greenland halibut (Reinhardtius hippoglossoides). Greenland halibut are likely target prey during the deep dives in winter but capelin (Mallotus villosus) may, with ocean warming, become of increasing importance. The ocean‐wide predictability in culturally inherited migration patterns, size of wintering grounds and habitat selection among narwhal populations is certainly different from other Arctic cetaceans and renders narwhals more vulnerable to large‐scale changes in their restricted and specialized habitats.

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One of the last pristine marine soundscapes, the Arctic, is exposed to increasing anthropogenic activities due to climate-induced decrease in sea ice coverage. In this study, we combined movement and behavioral data from animal-borne tags in a controlled sound exposure study to describe the reactions of narwhals, Monodon monoceros, to airgun pulses and ship noise. Sixteen narwhals were live captured and instrumented with satellite tags and Acousonde acoustic-behavioral recorders, and 11 of them were exposed to airgun pulses and vessel sounds. The sound exposure levels (SELs) of pulses from a small airgun (3.4 L) used in 2017 and a larger one (17.0 L) used in 2018 were measured using drifting recorders. The experiment was divided into trials with airgun and ship-noise exposure, intertrials with only ship-noise, and pre- and postexposure periods. Both trials and intertrials lasted ∼4 h on average per individual. Depending on the location of the whales, the number of separate exposures ranged between one and eight trials or intertrials. Received pulse SELs dropped below 130 dB re 1 μPa2 s by 2.5 km for the small airgun and 4–9 km for the larger airgun, and background noise levels were reached at distances of ∼3 and 8–10.5 km, respectively, for the small and big airguns. Avoidance reactions of the whales could be detected at distances &gt;5 km in 2017 and &gt;11 km in 2018 when in line of sight of the seismic vessel. Meanwhile, a ∼30% increase in horizontal travel speed could be detected up to 2 h before the seismic vessel was in line of sight. Applying line of sight as the criterion for exposure thus excludes some potential pre-response effects, and our estimates of effects must therefore be considered conservative. The whales reacted by changing their swimming speed and direction at distances between 5 and 24 km depending on topographical surroundings where the exposure occurred. The propensity of the whales to move towards the shore increased with increasing exposure (i.e., shorter distance to vessels) and was highest with the large airgun used in 2018, where the whales moved towards the shore at distances of 10–15 km. No long-term effects of the response study could be detected.