Population-specific sex and size variation in long-term foraging ecology of belugas and narwhals

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Intraspecific variation in resource use by individuals of different age, sex or size may reflect differing energetic requirements and physiological constraints. Males and females often show differences in diet owing to sexual size dimorphism, different life histories and/or habitat use. Here, we investigate how sex and size influence the long-term foraging ecology of belugas and narwhals in Greenland, using stable isotopes of carbon and nitrogen from bone collagen. We show that males have a higher trophic level and a larger ecological niche than females in West Greenland belugas and in East Greenland narwhals. In addition, for these two populations, we find that δ 15 N increases with size, particularly in males. We hypothesize that sexual size dimorphism together with strong maternal investment drive these differences. By contrast, we find no differences in foraging ecology between sexes in West Greenland narwhals and observe no influence of size on trophic level. This may reflect the influence of interspecific competition in West Greenland, where the distributions of belugas and narwhals overlap, and/or geographical resource partitioning among different summer aggregations of narwhals. Our results suggest that sex and size variations in diet are population dependent, and probably the result of varying ecological interactions.

TidsskriftRoyal Society Open Science
Udgave nummer2
Antal sider8
StatusUdgivet - 2021

Bibliografisk note

Funding Information:
Data accessibility. Electronic supplementary material, table S1. Authors’ contributions. E.D.L. conceived the study. M.L., P.S. and E.D.L. conceived the analyses. E.G. and M.P.H.-J. collected samples. M.L. and M.S. sampled the skulls. P.S. ran the isotopic laboratory analyses. M.L. performed the statistics. M.L. and E.D.L. wrote the manuscript with input from all co-authors. Competing interests. We have no competing interests. Funding. This research was supported by the Carlsberg Foundation Distinguished Associate Professor Fellowship, grant CF16-0202 to E.D.L. Acknowledgements. We thank fieldworkers and hunters involved in specimen collection. We are grateful to Uko Gorter for the illustrations, Julie Lorenzen for sampling advice and Rene Swift for figure 1a. We also would like to thank three anonymous reviewers for their input.

Publisher Copyright:
© 2021 The Authors.

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