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Marine Ecology Progress Series

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MEPS 384:303-312 (2009)  -  DOI:

Blubber fatty acid profiles indicate dietary resource partitioning between adult and juvenile southern elephant seals

China Newland1,*, Iain C. Field1,2, Peter D. Nichols3,4, Corey J. A. Bradshaw5,6, Mark A. Hindell1,4

1Antarctic Wildlife Research Unit, School of Zoology, University of Tasmania, Private Bag 05, Hobart, Tasmania 7001, Australia
2School for Environmental Research, Institute of Advanced Studies, Charles Darwin University, Darwin, Northern Territory 0909, Australia
3CSIRO Marine and Atmospheric Research, Food Futures Flagship, GPO Box 1538, Hobart, Tasmania 7000, Australia
4Antarctic and Climate Ecosystems CRC, Private Bag 80, Hobart, Tasmania 7001, Australia
5Research Institute for Climate Change and Sustainability, School of Earth and Environmental Sciences, University of Adelaide, Adelaide, South Australia 5005, Australia
6South Australian Research and Development Institute, PO Box 120, Henley Beach, South Australia 5022, Australia

ABSTRACT: When resources are limited or patchy, a species may develop some degree of resource partitioning to reduce intra-specific competition. Development of intra-specific resource partitioning is more pronounced in species with clear phenotypic variation among individuals (e.g. age or sex). Southern elephant seals Mirounga leonina have pronounced sexual dimorphism and range widely in size and foraging range between juvenile and adult stages. However, hypothesized diet-based resource partitioning has been less clear due to difficulties in sampling diet while seals are away from breeding islands. We analysed fatty acids (FAs) from blubber of 122 juvenile seals and compared them to FA profiles from blubber of 52 adult females, and to FA profiles from 51 prey species (grouped as fish and squid) to examine evidence for diet-based resource partitioning in the seals. FA signature analysis revealed physiological and dietary differences between ages. Principle components of the 21 FAs from seal blubber and prey parts distinguished prey from seals, and clearly separated prey species into fish and squid classes. FA profiles from adult females differed to those from juveniles, with the former more ‘squid-like’ and the latter more ‘fish-like’. Variation in FA profiles of seals was also apparent between sexes and during different seasons. Differences in diet between juveniles and adult females suggest resource partitioning occurs in response to large metabolic and physiological differences with age that limit juvenile dispersal and diving abilities. By consuming a different suite of prey species relative to adult females, juvenile southern elephant seals may reduce intra-specific competition.

KEY WORDS: Fatty acid signature analysis · Southern elephant seal · Diet · Resource partitioning

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Cite this article as: Newland C, Field IC, Nichols PD, Bradshaw CJA, Hindell MA (2009) Blubber fatty acid profiles indicate dietary resource partitioning between adult and juvenile southern elephant seals. Mar Ecol Prog Ser 384:303-312.

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