Abstract: Little is known on the food and feeding ecology of the soft-plumaged petrel Pterodroma mollis, which is the single gadfly petrel Pterodroma spp. with a circumpolar breeding distribution within the Southern Ocean. Our primary goal was to describe its diet at Kerguelen Islands, which is the southernmost breeding locality of the species. Soft-plumaged petrels fed on fish (71% by mass), and secondarily on crustaceans (22%), while cephalopods (7%) and other items (< 1%) were minor dietary components. Eight-hundred and sixty prey were identified from the pooled 33 food samples, with the 2 hyperiid amphipods Cyllopus magellanicus (48%) and Themisto gaudichaudii (35%) being the main food items by number. Owing to their larger size than crustaceans, mesopelagic fishes were the main prey by mass, with myctophids being the most important fish family in terms of both abundance (68% of the fish) and diversity (10 species). Prey distribution indicated that soft-plumaged petrels foraged primarily in oceanic subantarctic waters to feed their chicks. The oceanic life style of gadfly petrels was then highlighted by a review of their diet worldwide (20 species, 26 studies). Gadfly petrels prey mainly upon mesopelagic fishes (chiefly myctophids) and squids with their relative proportions depending on species and localities. Crustaceans are minor food items for tropical species, but they form a significant part of the food of the small- and medium-sized petrels that live in temperate and cold waters. The review underlines the need for more well-designed investigations on this globally endangered group of seabirds, since dietary information is available for only 57% of the 35 species of gadfly petrels.

Abstract: Social interactions are a ubiquitous feature of the lives of vertebrate species. These may be cooperative or competitive, and shape the dynamics of social systems, with profound effects on individual behavior, physiology, fitness, and health. On one hand, a wealth of studies on humans, laboratory animal models, and captive species have focused on understanding the relationships between social interactions and individual health within the context of disease and pathology. On the other, ecological studies are attempting an understanding of how social interactions shape individual phenotypes in the wild, and the consequences this entails in terms of adaptation. Whereas numerous studies in wild vertebrates have focused on the relationships between social environments and the stress axis, much remains to be done in understanding how socially-related activation of the stress axis coordinates other key physiological functions related to health. Here, we review the state of our current knowledge on the effects that social interactions may have on other markers of vertebrate fitness and health. Building upon complementary findings from the biomedical and ecological fields, we identify 6 key physiological functions (cellular metabolism, oxidative stress, cellular senescence, immunity, brain function, and the regulation of biological rhythms) which are intimately related to the stress axis, and likely directly affected by social interactions. Our goal is a holistic understanding of how social environments affect vertebrate fitness and health in the wild. Whereas both social interactions and social environments are recognized as important sources of phenotypic variation, their consequences on vertebrate fitness, and the adaptive nature of social-stress-induced phenotypes, remain unclear. Social flexibility, or the ability of an animal to change its social behavior with resulting changes in social systems in response to fluctuating environments, has emerged as a critical underlying factor that may buffer the beneficial and detrimental effects of social environments on vertebrate fitness and health.

Abstract: The present report is a synthesis of all studies conducted around the long-term ecological research (LTER) monitoring of introduced salmonid species in the sub Antarctic Kerguelen islands over the 2015- 2020 period, within the SALMEVOL-2 project. The monitoring encompasses the history of eight species, five of which are still present in Kerguelen, the data and collections spanning five decades and tenths of rivers. Based on this monitoring, but also thanks to various field experiments, we have undertaken to study the evolutionary ecology of these species, using the invasive Brown trout as flagship model, under the premise that the Kerguelen situation, where rivers were previously void of any fish species, could be an anticipation lab of the situation developing at the poles due to climate change. Our findings pertain to life history traits such as individual growth, migration between freshwater and marine ecosystems, microbiomes, but also proximal and ultimate mechanisms of adaptation in relation to the local environment. We also begin to investigate how the expanding metapopulation structure, resulting from multiple invasion events, may affect life history traits evolution.

Abstract: Seabirds are central place foragers, relying on prey that is patchily distributed and of variable predictability. Species travelling at a high energetic cost are more strongly dependent on spatially predictable prey. This is the case for diving petrels Pelecanoides spp., which are small Procellariiformes that feed by pursuit diving and travel by flapping constantly. Despite their abundance and importance as zooplankton consumers, information on the foraging strategy of diving petrels is still lacking. The detailed at-sea movements and the trophic niche of the South Georgian diving petrel P. georgicus was investigated for the first time using miniaturized GPS and the stable isotope method, respectively. Overall, South Georgian diving petrels from the Kerguelen Islands performed unexpected, direct and long-distance trips (mean foraging range: 191-217 km) to the Antarctic Polar Front, south of the archipelago. This foraging ground is a productive and predictable area, where the birds stopped and fed at the distal part of their trip. Blood isotopic values indicate that the tracked birds fed consistently on macrozooplankton. Such a distant oceanic feeding strategy contrasts with the coastal foraging patterns of the closely related common diving petrel P. urinatrix. Commuting to a more distant but easily accessible resource allows South Georgian diving petrels to cope with their high commuting costs, and to segregate spatially from the sympatric common diving petrel during the breeding season.