Abstract: Lactation is the most energy-demanding event in mammals' reproduction. In pinnipeds, females are the only food providers to the young and have developed numerous behavioral and physiological lactation strategies, from capital-breeding to income-breeding. Lactating females' fine-scale foraging strategy, and precise understanding of how females supplement their pup's needs as well as their own are important to understand the species' ecology and energetic balance. Polar pinnipeds, inhabiting extreme environments, are sensitive to climate change and variability, understanding their constraints and foraging strategy during lactation is therefore important. In 2019, three sonar tags were deployed on lactating Weddell seals in Terre Adélie (East Antarctica) for 7 days, to study fine-scale predator–prey interactions. Feeding activity was mostly benthic, reduced, central-placed, and spatially limited. Females spent most of their time hauled-out. A total of 331 prey capture attempts (PrCAs) were recorded using triaxial acceleration data, with 125 prey identified on echograms (5 cm, acoustic size). All PrCAs occurred on the seafloor, shallower than usual records (mean depth of 88 m, vs 280 m after their molt). We also found that they only fed in three of the five identified dive shapes, during the ascent or throughout the dive. Half of the prey were reactive to the seal's approach, either leaving the seafloor, or escaping just above the seafloor, suggesting that the seals hunt by chasing them from the seabed. Seals continuously scanned the area during the approach phase, evoking opportunistic foraging. Our results provide additional evidence that Weddell seal forage during lactation, displaying a mix of capital-breeding and income-breeding strategies during this period of physiological stress. This work sheds light on previously unexplored aspects of their foraging behavior, such as shallow water environments, targeting benthic prey, generally focusing on single prey rather than schools, and evidence of visual scanning through observed head movements.

Abstract: Abstract King penguins (Aptenodytes patagonicus) are colonial seabirds presenting an extraordinary breeding cycle. Parents take over 14 months to raise a single chick to independence, upon which fledglings depart at sea for more than a year. Juveniles often return to the colony within the three austral summers following departure, and before the age of first reproduction (around 5–6 years old), possibly to acquire the essential skills involved in breeding. Little to nothing is known on the acquisition of parental behaviour. Here, we report an anecdotal, yet highly unusual, observation of chick–chick feeding behaviour in this species. The behaviour is highly unusual in that two non-sibling chicks, not yet independent, and hatched at different times (early and late) of the same breeding season were observed, the older chick feeding the younger one. Whereas alloparental feeding is known to occur in this species, this is the first reported observation of a chick–chick feeding event. This unusual behaviour raises the question of whether the early social environment plays a role in the acquisition of essential parenting skills in this species.

Abstract:

Les endothermes polaires et subpolaires, adaptés à un climat froid, pourraient se révéler particulièrement sensibles au stress thermique dans un contexte de réchauffement global. L'hypothèse température-agression – qui propose un lien causal entre températures ambiantes élevées et motivation agressive – pourrait accentuer le stress thermique. Essentiellement étudiée pour des raisons socio-économiques, l’hypothèse est peu investiguée chez les espèces sauvages. L’étude de manchots royaux en période de reproduction (n= 85, Crozet), a permis de mettre en évidence des relations positives entre paramètres climatiques (température, radiation solaire), température sous-cutanée, indicateurs comportementaux de stress thermique (halètement, écartement des ailerons) et agressivité envers les congénères. Nos résultats ouvrent de nouvelles perspectives écologiques pour l'hypothèse température-agression, et encouragent l'étude du stress thermique dans les écosystèmes polaires.