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First published online December 14, 2007
Journal of Experimental Biology 211, 1-8 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.005785
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Review

Energy saving processes in huddling emperor penguins: from experiments to theory

Caroline Gilbert*, Stéphane Blanc, Yvon Le Maho and André Ancel

IPHC-DEPE, UMR 7178; Centre National de la Recherche Scientifique, Université Louis Pasteur, 23 rue Becquerel, 67087 Strasbourg, France

* Author for correspondence (e-mail: caroline.gilbert{at}c-strasbourg.fr)

Accepted 3 October 2007

This paper investigates the energy savings of male emperor penguins Aptenodytes forsteri linked to their huddling behaviour, the key factor that allows them to assume their incubating task while undergoing a long fast. Drawing on new studies by our team, this review examines the energetic benefits accrued from huddling and estimates the respective contributions of wind protection, exposure to mild ambient temperatures, reduction in cold-exposed body surfaces and body temperature adjustments in these energy savings. The metabolic rate of `loosely grouped' birds (restrained in small groups of 5–10 individuals, which are unable to huddle effectively) is reduced by 39% compared to metabolic rate of `isolated' birds, with 32% of these energetic benefits due to wind protection. In addition, metabolic rate of `free-ranging' emperors, i.e. able to move freely and to huddle, is on average 21% lower than that of `loosely grouped' birds. Exposure to mild ambient temperatures within the groups and reduction in cold-exposed body surfaces while huddling, though overestimated, would represent a 38% metabolic reduction. About two thirds of metabolic lowering is attributable to the reduction in cold-exposed body surfaces and one third to the mild microclimate created within the groups. Moreover, body temperature adjustments contribute to these energetic benefits: maintaining body temperatures 1°C lower would represent a 7–17% reduction in energy expenditure. These processes, linked together, explain how huddling emperors save energy and maintain a constant body temperature, which ensures a successful incubation in the midst of the austral winter.

Key words: huddling, emperor penguin, energetic benefit, wind protection, microclimate, body temperature


Related articles in JEB:

HOW HUDDLES HELP PENGUINS WEATHER WINTER
Kathryn Phillips
JEB 2008 211: i. [Full Text]  



This article has been cited by other articles:


Home page
 J. Exp. Biol.Home page
K. Phillips
HOW HUDDLES HELP PENGUINS WEATHER WINTER
J. Exp. Biol., January 1, 2008; 211(1): i - i.
[Full Text] [PDF]


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