AB 3:217-226 (2008)  -  DOI: https://doi.org/10.3354/ab00082

Seeing the light: depth and time restrictions in the foraging capacity of emperor penguins at Pointe Géologie, Antarctica

Ilka Zimmer1,*, Rory P. Wilson2, Michaël Beaulieu3, André Ancel3, Joachim Plötz1

1Alfred Wegener Institute for Polar and Marine Research, PO Box 120161, 27515 Bremerhaven, Germany
2Institute of Environmental Sustainability, School of Biological Sciences, University of Wales Swansea, Singleton Park, Swansea SA2 8PP , Wales, UK
3IPHC—Département Écologie, Physiologie et Éthologie—UMR7178 Centre National de la Recherche Scientifique and Université Louis Pasteur, 23 rue Becquerel, 67087 Strasbourg, France

ABSTRACT: The foraging ability of visual hunters depends critically on light conditions. Emperor penguins Aptenodytes forsteri are reported to be visual hunters, but breed and forage at high latitudes and are thus exposed to extreme changes in light conditions in the course of the year. We examined how light influenced the foraging ability of breeding emperor penguins using loggers in winter (n = 5) and spring (n = 4) 2005 at Pointe Géologie (66°40’S, 140°01’E), Antarctica, as well as by using models of light availability over the year and as a function of depth. The model showed that daylight was continuous between days of the year 350 and 363 and that the sun did not rise between days of the year 166 and 180. Logger-measured light intensity decreased with water depth, and depth-specific values were higher at greater sun elevation angles. Depth–time use (given by the maximum depth reached multiplied by the number of hours at which this depth could be achieved over 24 h) of spring-foraging penguins was 8394.5 m × h, which was more than twice that of winter-foraging birds at 3845.4 m × h, showing the severe constraints imposed by winter conditions. Average catch-per-unit effort was related to mean maximum diving depth and was highest around mid-day in winter and highest during dawn and dusk in spring. This reflects availability of prey to foraging emperor penguins.

KEY WORDS: Light intensity · Foraging · Emperor penguins · Depth–time availability

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Cite this article as: Zimmer I, Wilson RP, Beaulieu M, Ancel A, Plötz J (2008) Seeing the light: depth and time restrictions in the foraging capacity of emperor penguins at Pointe Géologie, Antarctica. Aquat Biol 3:217-226. https://doi.org/10.3354/ab00082

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