Breeding status affects the hormonal and metabolic response to acute stress in a long-lived seabird, the king penguin
Résumé
Stress responses are suggested to physiologically underlie parental decisions promoting the redirection of
behaviour away from offspring care when survival is jeopardized (e.g., when facing a predator). Besides
this classical view, the ‘‘brood-value hypothesis” suggests that parents’ stress responses may be adaptively
attenuated to increase fitness, ensuring continued breeding when the relative value of the brood
is high. Here, we test the brood-value hypothesis in breeding king penguins (Aptenodytes patagonicus),
long-lived seabirds for which the energy commitment to reproduction is high. We subjected birds at
different breeding stages (courtship, incubation and chick brooding) to an acute 30-min capture stress
and measured their hormonal (corticosterone, CORT) and metabolic (non-esterified fatty acid, NEFA)
responses to stress. We found that CORT responses were markedly attenuated in chick-brooding birds
when compared to earlier stages of breeding (courtship and incubation). In addition, NEFA responses
appeared to be rapidly attenuated in incubating and brooding birds, but a progressive increase in
NEFA plasma levels in courting birds suggested energy mobilization to deal with the threat. Our results
support the idea that stress responses may constitute an important life-history mechanism mediating
parental reproductive decisions in relation to their expected fitness outcome