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Centre d'Ecologie et Physiologie Energétiques, Unité Propre de Recherche 9010, Centre National de la Recherche Scientifique, Associé à l'Université Louis Pasteur, Affilié à l'Institut National de la Santé et de la Recherche Médicale, 67087 Strasbourg, France
This study examines the relationships
between metabolic status and behavior in spontaneously fasting birds in
the context of long-term regulation of body mass and
feeding. Locomotor activity, escape behavior, display
songs, body mass, and metabolic and endocrine status of captive male
emperor penguins were recorded during a breeding fast. We also examined
whether body mass at the end of the fast affected further survival. The
major part of the fast (phase II)
was characterized by the maintenance of a very low level of locomotor
activity, with almost no attempt to escape, by an almost constant rate
of body mass loss, and by steady plasma levels of uric acid,
-hydroxybutyrate, and corticosterone. This indicates behavioral and
metabolic adjustments directed toward sparing energy and body protein.
Below a body mass of ~24 kg (phase III), spontaneous locomotor activity and attempts to
escape increased by up to 8- and 15-fold, respectively, and display
songs were resumed. This probably reflected an increase in the drive to
refeed. Simultaneously, daily body mass loss and plasma levels of uric acid and corticosterone increased, whereas plasma levels of
-hydroxybutyrate decreased. Some experimental birds were seen again
in following years. These findings suggest that at a threshold of body
mass, a metabolic and endocrine shift, possibly related to a limited availability of fat stores, acts as a "refeeding signal" that improves the survival of penguins to fasting.
energy balance; anorexia; spontaneous fasting; body mass threshold; locomotor activity; feeding behavior; corticosterone
This article has been cited by other articles:
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  S. F. Bernard, J. Orvoine, and R. Groscolas Glucose regulates lipid metabolism in fasting king penguins Am J Physiol Regulatory Integrative Comp Physiol, August 1, 2003; 285(2): R313 - R320. [Abstract] [Full Text] [PDF]
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S. F. Bernard, M.-A. Thil, and R. Groscolas Lipolytic and metabolic response to glucagon in fasting king penguins: phase II vs. phase III Am J Physiol Regulatory Integrative Comp Physiol, February 1, 2003; 284(2): R444 - R454. [Abstract] [Full Text] [PDF]
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 S. F. Bernard, C. Fayolle, J.-P. Robin, and R. Groscolas Glycerol and NEFA kinetics in long-term fasting king penguins: phase II versus phase III J. Exp. Biol., September 1, 2002; 205(17): 2745 - 2754. [Abstract] [Full Text] [PDF]
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S. F. Bernard, E. Mioskowski, and R. Groscolas Blockade of fatty acid oxidation mimics phase II-phase III transition in a fasting bird, the king penguin Am J Physiol Regulatory Integrative Comp Physiol, July 1, 2002; 283(1): R144 - R152. [Abstract] [Full Text] [PDF]
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R. Groscolas, F. Decrock, M.-A. Thil, C. Fayolle, C. Boissery, and J.-P. Robin Refeeding signal in fasting-incubating king penguins: changes in behavior and egg temperature Am J Physiol Regulatory Integrative Comp Physiol, December 1, 2000; 279(6): R2104 - R2112. [Abstract] [Full Text] [PDF]
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L. Jenni, S. Jenni-Eiermann, F. Spina, and H. Schwabl Regulation of protein breakdown and adrenocortical response to stress in birds during migratory flight Am J Physiol Regulatory Integrative Comp Physiol, May 1, 2000; 278(5): R1182 - R1189. [Abstract] [Full Text] [PDF]
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