MEPS 577:237-250 (2017)  -  DOI: https://doi.org/10.3354/meps12240

Low trophic level diet of juvenile southern elephant seals Mirounga leonina from Marion Island: a stable isotope investigation using vibrissal regrowths

Nico Lübcker1,*, Ryan R. Reisinger1,4, W. Chris Oosthuizen1, P. J. Nico de Bruyn1, André van Tonder1, Pierre A. Pistorius2,3, Marthán N. Bester1

1Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Hatfield 0028, Pretoria, South Africa
2Marine Apex Predator Research Unit, Institute for Coastal and Marine Research, Nelson Mandela Metropolitan University, South Campus, Port Elizabeth 6031, South Africa
3DST/NRF Centre of Excellence at the Percy FitzPatrick Institute, Department of Zoology, Nelson Mandela Metropolitan University, South Campus, Port Elizabeth 6031, South Africa
4Present address: Centre d’Etudes Biologiques de Chizé, UMR 7372 du CNRS-Université de La Rochelle, 79360 Villiers-en-Bois, France
*Corresponding author:

ABSTRACT: Insight into the trophic ecology of marine predators is vital for understanding their ecosystem role and predicting their responses to environmental change. Juvenile southern elephant seals (SES) Mirounga leonina are considered generalist predators within the Southern Ocean. Although mesopelagic fish and squid dominate their stomach lavage samples, the stable isotope profile captured along the length of sampled vibrissae of young SES at Macquarie Island, southwest Pacific Ocean (54.5°S, 158.9°E) recently emphasized the contribution of crustaceans to their diet (likely Euphausia superba). Herein, we used the stable isotope values of sampled vibrissal regrowths with known growth histories to assess the diet of juvenile SES at Marion Island, southern Indian Ocean (46.8°S, 37.8°E) on a temporally integrated basis. We specifically aimed to quantify the possible contribution of crustaceans to the diet of juvenile SES. Sequentially (chronologically) sampled vibrissal regrowths of 14 juvenile SES produced fine-scale dietary information spanning up to 9 mo. The depleted stable isotope signatures of nitrogen (δ15N) (8.5 ± 0.6‰) and carbon (δ13C) (-20.3 ± 0.1‰) measured during the period of independent foraging suggested the use of a lower trophic level diet within the Polar Frontal Zone. A mixing model predicted that up to 76% of juvenile SES diet comprised crustaceans, consisting of 2 crustacean groups, each contributing 26% (credible interval, CI: 13-39%) and 50% (CI: 35-64%) to their diets, presumably representing subantarctic krill species. This first utilisation of the isotopic signature captured along the length of vibrissal regrowths confirms the inclusion and importance of crustaceans in the diet of juvenile SES.


KEY WORDS: Crustaceans · Diet · Marine mammals · Pinnipeds · Stable isotopes · Vibrissae · Whiskers


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Cite this article as: Lübcker N, Reisinger RR, Oosthuizen WC, de Bruyn PJN, van Tonder A, Pistorius PA, Bester MN (2017) Low trophic level diet of juvenile southern elephant seals Mirounga leonina from Marion Island: a stable isotope investigation using vibrissal regrowths. Mar Ecol Prog Ser 577:237-250. https://doi.org/10.3354/meps12240

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