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Marine Ecology Progress Series

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MEPS 522:269-286 (2015)  -  DOI:

Seasonal foraging behaviour of Eastern Canada-West Greenland bowhead whales: an assessment of isotopic cycles along baleen

Cory J. D. Matthews1,*, Steven H. Ferguson1,2

1Department of Biological Sciences, University of Manitoba, Winnipeg, MB R3T 2N2, Canada
2Fisheries and Oceans Canada, 501 University Crescent, Winnipeg, MB R3T 2N6, Canada
*Corresponding author:

ABSTRACT: Eastern Canada-West Greenland (EC-WG) bowhead whales Balaena mysticetus migrate seasonally between northwestern Hudson Bay/Foxe Basin and Gulf of Boothia in summer and Hudson and Davis Straits in winter. Despite recent advances in knowledge of summer diet composition, determining seasonal variation in foraging behaviour of EC-WG bowhead whales remains a priority for understanding how annual metabolic requirements are met, as well as identifying factors driving seasonal habitat selection. We measured stable nitrogen, carbon, and sulfur isotope composition (δ15N, δ13C, and δ34S) along continuously growing baleen plates (n = 14) to assess alternative seasonal foraging hypotheses, namely winter fasting vs. year-round foraging. Synchronous δ15N and δ13C cycles, with periods of 15N enrichment corresponding to foraging on the summer grounds, were inconsistent with standard fasting predictions, although δ15N cycles could reflect changes in diet-tissue δ15N discrimination between periods of intense foraging throughout the open-water season and supplemental protein intake during winter/spring. Correlations between δ15N and δ34S values, potentially meditated through amino acid metabolism, support this interpretation. Reasonable agreement between baleen isotope oscillations and regional baseline δ15N and δ13C variation also indicated foraging occurs within isotopically distinct food webs across the summer and winter ranges. We conclude that EC-WG bowhead whales forage throughout their distribution, and conservatively interpret δ15N and δ34S cycles to reflect reduced food consumption during winter. Foraging outside of periods of peak productivity likely contributes to annual metabolic requirements and winter habitat selection.

KEY WORDS: Arctic · Balaena mysticetus · Diet · Fasting · Isoscape · Marine mammal · Stable isotopes · Sulfur · Time series

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Cite this article as: Matthews CJD, Ferguson SH (2015) Seasonal foraging behaviour of Eastern Canada-West Greenland bowhead whales: an assessment of isotopic cycles along baleen. Mar Ecol Prog Ser 522:269-286.

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