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RESEARCH ARTICLE
Contents Vol 109(3)

Diet composition, continuity in prey availability and marine habitat – keystones to population stability in the Snares Penguin (Eudyptes robustus)

Thomas Mattern A D , David M. Houston B , Chris Lalas C , Alvin N. Setiawan A and Lloyd S. Davis A
+ Author Affiliations
- Author Affiliations

A Department of Zoology, University of Otago, PO Box 56, Dunedin, New Zealand.

B Department of Conservation, Private Bag 68908, Newton, Auckland, New Zealand.

C PO Box 31, Portobello, Dunedin, New Zealand.

D Corresponding author. Email: t.mattern@eudyptes.net

Emu 109(3) 204-213 https://doi.org/10.1071/MU08001
Submitted: 8 January 2008  Accepted: 22 May 2009   Published: 13 August 2009

Abstract

Worldwide, crested penguins (Eudyptes spp.) are in decline and it is suspected that reduced prey availability plays an important role. However, the population of Snares Penguins (E. robustus) does not follow this trend, with its population being stable if not slightly increasing. To assess whether the success of the Snares Penguins is a result of a rich and stable prey resource within the breeding range of the species, we examined the dietary composition of breeding Snares Penguins by analysis of stomach contents, and analysed ratios of carbon (δ13C) and nitrogen (δ15N) stable isotopes in feathers of living penguins and historical specimens. The food brought ashore by the Penguins was dominated by a single species of krill, Nyctiphanes australis (~60% of wet weight of the stomach samples); fish (~30%) and cephalopods (~10%) seemed to form only a minor portion. However, numbers of fish otoliths and cephalopod beaks in the samples suggest that these prey classes are more important food source for adult Penguins while at sea. Stable isotope ratios of Snares Penguin feathers collected between 1880 and 2004 revealed no temporal trend in either δ13C or δ15N indicating no significant changes in marine productivity or general composition of the diet of Snares Penguins in the past 120 years. We discuss our findings in the light of declining population trends and changing stable isotope ratios recently detected in Rockhopper Penguins (E. chrysocome), and conclude that the Snares Penguins benefit from stable prey availability as a function of the oceanographic setting of their breeding habitat.


Acknowledgements

We are especially grateful for the help we received from the many museums we contacted while searching for historic penguin skins. We thank in particular Gillian Stone (Te Papa Tongarewa, Museum of New Zealand, Wellington, NZ), Ernst Bauernfeind and Anita Gamauf (Naturhistorisches Museum, Wien, Austria), Robert Prys-Jones, Joanne Cooper and Mark Adams (Natural History Museum, London, England), Paul Scofield (Canterbury Museum, Christchurch, NZ), and Paul Sweet (American Museum of Natural History, New York, USA). We furthermore extend our gratitude to David Thompson and Sara Bury (NIWA, Wellington, NZ) for facilitating and conducting the stable isotope analysis, and to Uwe Piatkowski (IFM-GEOMAR, University of Kiel, Germany) for his enthusiastic help with cephalopod identification. Very special thanks to Ursula Ellenberg and Katrin Ludynia for help and support in the field, and to Lars-Gunnar Ellenberg for programming the otolith measuring software. We thank the Department of Conservation, Southland Conservancy, for issuing research permits and logistical support. This study was approved by the Department of Conservation and the Animal Ethics Committee of the University of Otago and complies with current laws of New Zealand.


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