This axis studies behavioral and physiological responses to fasting and how birds cope with re-feeding after a prolonged fast, depending on whether or not a threshold of depletion of lipid reserves has been reached. This is a situation that king penguins naturally face during incubation and depends, at least in part, on the length of the partner's foraging journey. Indeed, we have already shown that in this species, under optimal coordination of breeding pairs, the incubating individual retains a lipid mass greater than a minimum threshold at which survival might be threatened. However, if the partner is slow to return, the incubating animal ends up giving up reproduction when its protein metabolism is increased, its lipid mass having reached a lower critical mass (Groscolas and Robin, 2001, Comp. Biochem. Physiol. A. et al. Robin et al., 2001, J. of Avian Biology for review). Yet in both cases, animals seem to recover well, and the mechanisms are underlying such recovery are unclear. The king penguin is one of the few animal models in which this situation can be studied in natura. The interest is both fundamental to understanding the phenomenon and can have implications in terms of conservation biology, the duration of food journeys can be modified by a disturbance of the environment, such as that linked, for example, to changes global or overfishing.

King penguin colonies experience a sharp increase in density during the breeding season. Individuals must defend their territory (approximately 80 cm in diameter) because the area chosen is of capital importance for breeding success. The location which the animals choose to breed in the colony has major consequences on the predation levels they experience, the parasites the are subject to and, apparently, their stress levels that seem to be higher at higher social density. This axis explores the relationship between plasma levels of corticosterone (stress hormone, CORT) and territorial behavior in breeding adults - and the consequences this has on various aspects of physiology (energy metabolism, oxidative stress, immunity) and fitness.

One objective is to determine whether stress hormones are a causal factor allowing more aggressive birds to secure more central positions in the colony, or if higher levels of CORT observed in central birds are a consequence of the higher social density and associated social stress (Viblanc et al., 2014a).

This research axis led in collaboration with the 394 polar porgam (C Bost, Y Handrich) aims at studying the interrelation between bird performance on land, and bird performance at sea. Specifically, we are interested in the the links between morphology, physiology and behavior during reproduction in the king penguin - and the diving performances of birds when they leave the colony to forage. This approach also includes taking into account environmental conditions to test the importance of natural selection on combinations of particular traits. Ultimately, the objective is to determine the effect of the environment and parental characteristics on the natural variation of the phenotype in the chicks and on the couple's reproductive success. One of the major questions in this axis is the comparison of early and late breeding individuals. Indeed, the duration of the reproductive cycle in the king penguin is more than one year, some individuals will start breeding very late in the season although their chances of success are minimal. We seek to understand the differences between early and late breeding strategies, and the consequences of those for chick phenotype and survival.

Although aging is a complex and multifactorial process, mitochondrial dysfunction, oxidative stress and telomere shortening appear to be major factors. This is because the mitochondria is the main producer of reactive oxygen species (ROS) which can damage the cell and shorten the lifespan when produced in excess (oxidative stress). This phenomenon is exacerbated during exposure to stress via the alteration of mitochondrial function by the stress hormone (glucocorticoids). Oxidative stress helps accelerate the shortening of telomeres, non-coding DNA structures that protect the ends of chromosomes, thereby helping to protect cells from senescence. This xis of the program aims to explore these aging processes in the king penguin and explain the inter-individual differences observed by integrating environmental parameters, individual performance and reproductive success. We are specifically interested in the phenotypic adaptations allowing birds to cope with their stressful on-land environment.

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The theory of sexual selection suggests that extravagant morphological traits can be preserved during evolution if they provide advantages to their carriers for access to reproduction. These traits are expensive to produce / maintain and therefore must "honestly" reflect the quality of the wearer, since only individuals capable of investing in both survival and ornamentation are able to put on such pageantry. In the king penguin, males and females present multiple sexual ornaments: large auricular feather patches with bright yellow-orange feathers, a pectoral gradient with feathers ranging from brown to yellow, as well as two orange-yellow mandibular plates on either side of the beak, which also reflects UV. In this species, previous studies have experimentally demonstrated an important role of auricular and beak tasks in the choice of mate. Indeed, reducing the surface (spots) or the brightness (beak) of these ornaments induces a delay in the pairing, thus placing these signals directly under the influence of sexual selection. In this axis of the program, we are interested in understand the mechanisms underlying these secondary sexual characteristics and that guarantee the honesty of ornamental signals.