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Polar Biology

, Volume 34, Issue 7, pp 1057–1063 | Cite as

Dietary isotopic discrimination in gentoo penguin (Pygoscelis papua) feathers

  • Michael J. Polito
  • Stephanie Abel
  • Craig R. Tobias
  • Steven D. Emslie
Original Paper

Abstract

Feathers are used commonly for stable isotope analysis to assess the foraging ecology and migration patterns of birds. However, these studies often require knowledge of species-specific feather isotopic discrimination factors (the differences in isotopic ratios between a species’ diet and feathers), which can be influenced by a species’ physiological state during molt. In this study, we determined the isotopic discrimination factors (Δ13Cdiet−feather and Δ15Ndiet−feather) between adult gentoo penguin (Pygoscelis papua) diet and feathers in a controlled study. In addition, we tested whether molt duration or the magnitude of voluntary dietary reduction during molt influenced isotopic discrimination, as previous studies have found that nutritional stress can exaggerate 15N enrichment and in some cases lead to 13C depletion in feathers. Contrary to this hypothesis, we found no effect of molt duration or dietary reduction on discrimination factors, suggesting that isotopic discrimination is not linearly related to these measures of fasting intensity in penguins. Furthermore, we found that the range of Δ15Ndiet−feather found in several species of penguins, which fast while they molt, was similar to discrimination factors in fish-eating birds, which do not fast during molt. It is likely that species-specific metabolic adaptations that limit nutritional stress while fasting and variation in their relative reliance on endogenous vs. dietary pools during feather growth may confound the use of Δ15Ndiet−feather as a general measure of nutritional stress when comparing among species.

Keywords

Discrimination factors Gentoo penguin Molt Nutritional stress Pygoscelis papua Stable isotopes 

Notes

Acknowledgments

This research was funded by NSF OPP grants ANT-0125098 and ANT-0739575, with additional support from a Ralph W. Brauer Fellowship to M. Polito. We thank K. Vires, J. Beck, K. McGrath, T. Solberg and D. Rivard, and the staff of the Scott Kingdoms of the Seas Aquarium at Omaha’s Henry Doorly Zoo for their invaluable assistance with this study. T. Lankford and K. Durenberger provided assistance with lipid extractions and stable isotope analysis. We also thank Y. Cherel and K. Hobson for helpful insights during the preparation of this manuscript. This manuscript was improved through the comments of three reviewers: M. Beaulie, A. Bond, and C. Williams. This work complies with, and was completed in accordance to, IACUC permit number HDZ#07-800.

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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • Michael J. Polito
    • 1
  • Stephanie Abel
    • 2
  • Craig R. Tobias
    • 3
  • Steven D. Emslie
    • 1
  1. 1.Department of Biology and Marine BiologyUniversity of North CarolinaWilmingtonUSA
  2. 2.Henry Doorly ZooOmahaUSA
  3. 3.Department of Geography and GeologyUniversity of North CarolinaWilmingtonUSA

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