title: Are stress hormone levels a good proxy of foraging success? An experiment with king penguins, Aptenodytes patagonicus.
abstract: In seabirds, variations in stress hormone (corticosterone; henceforth CORT) levels have been shown to reflect changing marine conditions and, especially, changes in food availability. However, it remains unclear how CORT levels can be mechanistically affected by these changes at the individual level. Specifically, the influence of food acquisition and foraging success on CORT secretion is poorly understood. In this study, we tested whether food acquisition can reduce baseline CORT levels (;the food intake hypothesis') by experimentally reducing foraging success of King Penguins (Aptenodytes patagonicus). Although CORT levels overall decreased during a foraging trip, CORT levels did not differ between experimental birds and controls. These results demonstrate that mass gain at sea is not involved in changes in baseline CORT levels in this species. The overall decrease in CORT levels during a foraging trip could result from CORT-mediated energy regulation (;the energy utilisation hypothesis'). Along with other evidence, we suggest that the influence of foraging success and food intake on CORT levels is complex and that the ecological meaning of baseline CORT levels can definitely vary between species and ecological contexts. Therefore, further studies are needed to better understand (1) how baseline CORT levels are functionally regulated according to energetic status and energetic demands and (2) to what extent CORT can be used to aid in the conservation of seabird populations.
authors.affiliation: Centre d'Etudes Biologiques de Chizé, Centre National de la Recherche Scientifique, 79360, Villiers en Bois, France. fangelier@ucdavis.edu
authors.forename: Frédéric
authors.initials: F
authors.lastname: Angelier
authors.forename: Mathieu
authors.initials: M
authors.lastname: Giraudeau
authors.forename: Charles-André
authors.initials: CA
authors.lastname: Bost
authors.forename: Fabrice
authors.initials: F
authors.lastname: Le Bouard
authors.forename: Olivier
authors.initials: O
authors.lastname: Chastel
mesh_terms: D000818:Animals; D001823:Body Composition; D003345:Corticosterone / Q000097:blood*; D004435:Eating; D005247:Feeding Behavior; D005260:Female; D008297:Male; D046429:Spheniscidae / Q000033:anatomy & histology / Q000378:metabolism* / Q000502:physiology
chemical_list: D003345:Corticosterone