Decadal changes in blood δ 13 C values, at-sea distribution, and weaning mass of southern elephant seals from Kerguelen Islands

Mestre, Julie, Authier, Matthieu, Cherel, Yves, Harcourt, Rob, McMahon, Clive R., Hindell, Mark A., Charrassin, Jean-Benoît and Guinet, Christophe (2020) Decadal changes in blood δ 13 C values, at-sea distribution, and weaning mass of southern elephant seals from Kerguelen Islands. Proceedings of the Royal Society B: Biological Sciences, 287 (1933). (doi:10.1098/rspb.2020.1544).

Abstract

Changes in the foraging environment and at-sea distribution of southern
elephant seals from Kerguelen Islands were investigated over a decade
(2004–2018) using tracking, weaning mass, and blood δ13C values. Females
showed either a sub-Antarctic or an Antarctic foraging strategy, and no
significant shift in their at-sea distribution was detected between 2004 and
2017. The proportion of females foraging in sub-Antarctic versus Antarctic
habitats did not change over the 2006–2018 period. Pup weaning mass
varied according to the foraging habitat of their mothers. The weaning
mass of sub-Antarctic foraging mothers’ pups decreased by 11.7 kg over
the study period, but they were on average 5.8 kg heavier than pups from
Antarctic foraging mothers. Pup blood δ13C values decreased by 1.1‰
over the study period regardless of their sex and the presumed foraging
habitat of their mothers. Together, these results suggest an ecological
change is occurring within the Indian sector of the Southern Ocean with
possible consequences on the foraging performance of southern elephant
seals. We hypothesize that this shift in δ13C is related to a change in primary
production and/or in the composition of phytoplankton communities, but
this requires further multidisciplinary investigations.

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Contributors

Author: Julie Mestre

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