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

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 inv...

Full description

Bibliographic Details
Published in:Royal Society Open Science
Main Authors: Louis, Marie, Skovrind, Mikkel, Garde, Eva, Heide-Jørgensen, Mads Peter, Szpak, Paul, Lorenzen, Eline D.
Other Authors: Carlsberg Foundation Distinguished Associate Professor Fellowship
Format: Article in Journal/Newspaper
Language:English
Published: The Royal Society 2021
Subjects:
Online Access:http://dx.doi.org/10.1098/rsos.202226
https://royalsocietypublishing.org/doi/pdf/10.1098/rsos.202226
https://royalsocietypublishing.org/doi/full-xml/10.1098/rsos.202226
Description
Summary: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.