Spatially explicit estimates of prey consumption reveal a new krill predator in the Southern Ocean

Andrea Walters, Mary Anne Lea, John Van Den Hoff, Iain C. Field, Patti Virtue, Sergei Sokolov, Matt H. Pinkerton, Mark A. Hindell

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Abstract

Development in foraging behaviour and dietary intake of many vertebrates are age-structured. Differences in feeding ecology may correlate with ontogenetic shifts in dispersal patterns, and therefore affect foraging habitat and resource utilization. Such life-history traits have important implications in interpreting tropho-dynamic linkages. Stable isotope ratios in the whiskers of sub-yearling southern elephant seals (Mirounga leonina; n = 12) were used, in conjunction with satellite telemetry and environmental data, to examine their foraging habitat and diet during their first foraging migration. The trophic position of seals from Macquarie Island (54°30′S, 158°57′E) was estimated using stable carbon (δ13C) and nitrogen (δ15N) ratios along the length of the whisker, which provided a temporal record of prey intake. Satellite-relayed data loggers provided details on seal movement patterns, which were related to isotopic concentrations along the whisker. Animals fed in waters south of the Polar Front (>60°S) or within Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) Statistical Subareas 88.1 and 88.2, as indicated by both their depleted δ13C (<-20%) values, and tracking data. They predominantly exploited varying proportions of mesopelagic fish and squid, and crustaceans, such as euphausiids, which have not been reported as a prey item for this species. Comparison of isotopic data between sub-yearlings, and 1, 2 and 3 yr olds indicated that sub-yearlings, limited by their size, dive capabilities and prey capture skills to feeding higher in the water column, fed at a lower trophic level than older seals. This is consistent with the consumption of euphausiids and most probably, Antarctic krill (Euphausia superba), which constitute an abundant, easily accessible source of prey in water masses used by this age class of seals. Isotopic assessment and concurrent tracking of seals are successfully used here to identify ontogenetic shifts in broad-scale foraging habitat use and diet preferences in a highly migratory predator.

Original languageEnglish
Article numbere86452
Pages (from-to)1-17
Number of pages17
JournalPLoS ONE
Volume9
Issue number1
DOIs
Publication statusPublished - 24 Jan 2014

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Copyright the Author(s) 2014. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

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    Walters, A., Lea, M. A., Van Den Hoff, J., Field, I. C., Virtue, P., Sokolov, S., ... Hindell, M. A. (2014). Spatially explicit estimates of prey consumption reveal a new krill predator in the Southern Ocean. PLoS ONE, 9(1), 1-17. [e86452]. https://doi.org/10.1371/journal.pone.0086452