Differential effects of increased corticosterone on behavior at the nest and reproductive output of chick-rearing Adélie penguins
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Glucocorticoid hormones (GCs) are important mediators of physiological and behavioral responses to stress. While many studies have evaluated the environmental, behavioral, or physiological correlates of GCs and their effects on reproductive performances, further work is needed to clarify the relationship between GCs and fitness. Assessing the effects of increased GC levels on specific behaviors of breeding animals should improve our understanding of how GCs affect parental care. In this experimental study, we measured the effects of an experimental increase in corticosterone (CORT, the main avian GC) levels on the behavior of free-living male Adélie penguins (Pygoscelis adeliae) within the colony, their reproductive output, and the indirect consequences of both on the behavior of their partners. We show that increased CORT levels in males decreased their foraging time at sea while increased their attendance at the nest, although their attentiveness toward the nest itself decreased. In addition, treated males spent more time on comfort behaviors (e.g., preening), vocalizing, and engaging in positive social interactions relative to controls. Treatment further affected the behavior of their partners, but not chick begging and feeding rates. Penguins with increased CORT levels also exhibited decreased reproductive output. Previous studies of Adélie penguins in different life history stages and environmental conditions suggest that the consequences of CORT treatment on reproductive performance are context-dependent. In addition to the potential delay in the effects of increased CORT levels on reproduction, this context dependence should be taken into account when studying the behavior of free-living animals in relation to stress-inducing situations.
KeywordsTime budget Behavior Glucocorticoid Pygoscelis adeliae Reproduction Reproductive performances
The French Polar Institute Paul-Emile Victor provided financial and logistical support. We thank M. Debin for her help in the field, A. Laurent for her contribution in video analyses, and Dr. A. J. J. MacIntosh and Dr. V. A. Viblanc for helpful comments on the manuscript.
The protocol was approved by an independent ethics committee commissioned by the French Polar Institute Paul-Emile Victor and the study was authorized (decrees 2009-57 and 2009-59) by the French Southern and Antarctic Lands (Terres Australes et Antarctiques Françaises). The study complies with the current laws of France and of the Terres Australes et Antarctiques Françaises.
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