First documented movement of a humpback whale between the Cape Verde Islands and West Greenland.

The endangered population of humpback whales (Megaptera novaeangliae) breeding and calving off the Cape Verde Islands (CVI) are known to migrate to feeding areas located along the eastern margin of the North Atlantic Ocean (Iceland, and Norway). Here, we report for the first time a confirmed migration of an individual humpback whale from CVI breeding ground to a western North Atlantic feeding ground of West Greenland. This individual humpback, which was photographed and identified off the coast of West Greenland in 2021, was previously documented in CVI 22 years before (1999). An annual subsistence hunt for humpbacks occurs in West Greenland and the resighting at this location with a humpback whale from CVI has strong implications for the conservation efforts of the small CVI population.

An evolutionarily distinct ringed seal in the Ilulissat Icefjord.

The Earth's polar regions are low rates of inter- and intraspecific diversification. An extreme mammalian example is the Arctic ringed seal (Pusa hispida hispida), which is assumed to be panmictic across its circumpolar Arctic range. Yet, local Inuit communities in Greenland and Canada recognize several regional variants; a finding supported by scientific studies of body size variation. It is however unclear whether this phenotypic variation reflects plasticity, morphs or distinct ecotypes. Here, we combine genomic, biologging and survey data, to document the existence of a unique ringed seal ecotype in the Ilulissat Icefjord (locally 'Kangia'), Greenland; a UNESCO World Heritage site, which is home to the most productive marine-terminating glacier in the Arctic. Genomic analyses reveal a divergence of Kangia ringed seals from other Arctic ringed seals about 240 kya, followed by secondary contact since the Last Glacial Maximum. Despite ongoing gene flow, multiple genomic regions appear under strong selection in Kangia ringed seals, including candidate genes associated with pelage coloration, growth and osmoregulation, potentially explaining the Kangia seal's phenotypic and behavioural uniqueness. The description of 'hidden' diversity and adaptations in yet another Arctic species merits a reassessment of the evolutionary processes that have shaped Arctic diversity and the traditional view of this region as an evolutionary freezer. Our study highlights the value of indigenous knowledge in guiding science and calls for efforts to identify distinct populations or ecotypes to understand how these might respond differently to environmental change.

The significance of the north water polynya to arctic top predators.

The North Water polynya (~76°N to 79°N and 70°W to 80°W) is known to be an important habitat for several species of marine mammals and sea birds. For millennia, it has provided the basis for subsistence hunting and human presence in the northernmost part of Baffin Bay. The abundance of air-breathing top predators also represents a potential source of nutrient cycling that maintains primary production. In this study, aerial surveys conducted in 2009 and 2010 were used for the first time to map the distribution and estimate the abundance of top predators during spring in the North Water. Belugas (Delphinapterus leucas) were not detected north of 77°20'N but were found along the coast of West Greenland and offshore in the middle of the North Water with an abundance estimated at 2245 (95 % CI 1811-2783). Narwhals (Monodon monoceros) were widely distributed on the eastern side of the North Water with an estimate of abundance of 7726 (3761-15 870). Walruses (Odobenus rosmarus) were found across the North Water over both shallow and deep (>500 m) water with an estimated abundance of 1499 (1077-2087). Bearded (Erignathus barbatus) and ringed seals (Phoca hispida) used the large floes of ice in the southeastern part of the North Water for hauling out. Most polar bears (Ursus maritimus) were detected in the southern part of the polynya. The abundances of bearded and ringed seals were 6016 (3322-10 893) and 9529 (5460-16 632), respectively, and that of polar bears was 60 (12-292). Three sea bird species were distributed along the Greenland coast (eiders, Somateria spp.), in leads and cracks close to the Greenland coast (little auks, Alle alle) or widely in open water (thick-billed guillemots, Uria lomvia).