Baffin Bay narwhal (Monodon monoceros) select bathymetry over sea ice during winter
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Arctic pack ice structure and extent have been changing due to warming. Thus, understanding important habitat features for marine mammals that depend on sea ice, such as narwhal (Monodon monoceros), during winter will provide insight into impacts of future changes within the pack ice. The objective of this study was to determine narwhal habitat selection for bathymetry, sea ice concentration, thickness, and floe size during the winter season. Nineteen narwhals were equipped with SPLASH tags in Admiralty Inlet and Eclipse Sound (2009–2011), with 50% of the transmitters lasting until April allowing for analysis of the entire winter season. Generalized linear mixed models indicated that both sexes selected similar bathymetric habitat likely corresponding to higher prey densities of Greenland halibut. This preference for prey habitat occurred regardless of the mobile pack ice structure or amount of open water at the ocean surface. In addition, we found evidence of a potential relationship between increased winter movements and decreased ice extent over the 2009–2011 period. Together these findings suggest that changes to sea ice structure likely will not negatively impact narwhal directly in the winter. However, indirect effects of changing sea ice, such as changing prey densities and distribution, increased presence of killer whales (Orcinus orca) as predators, increased interspecies competition for prey, and increased anthropogenic activities could influence winter habitat selection of narwhal. In conclusion, the extensive winter movements indicate that narwhal may be more flexible in their selection of winter habitat than previously believed.
KeywordsBathymetry Habitat use Greenland halibut Migration Animal telemetry Winter sea ice
We thank the Pond Inlet and Arctic Bay Hunters and Trappers Organizations for their support in live capturing and tagging of narwhals. Logistical support was provided by Polar Continental Shelf Program. This study was funded by Nunavut Wildlife Management Board, World Wildlife Fund Canada (Grant No. G-1215-141-02-D), Natural Sciences and Engineering Research Council (Grant No. CGS M), ArcticNet Network of Centres of Excellence, University of Manitoba (Grant Nos. 45525, TMSA), and Fisheries and Oceans Canada. We thank the Canada Excellence Research Chair, the Canada Research Chair, the Arctic Science Partnership, and the Center of Earth Observation Science for their support. DJY was supported by the W. Garfield Weston Foundation.
Compliance with ethical standards
Animal handling procedures were approved by the Freshwater Institute Animal Care Committee under Animal Use Protocols FWI-ACC-2009-024, FWI-ACC-2010-008, and FWI-ACC-2011-016. Licence to Fish for Scientific Purposes from the Minister of Fisheries and Oceans were obtained. Licence Numbers were S-09/10-1015-NU, S-10/11-1029-NU, and S-11/12/1039-NU.
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