Abstract: Group-living is associated with both fitness benefits and costs for animals. In seabird colonies, spatial heterogeneity in social density and other environmental parameters may affect the quality of breeding territories. For instance, in king penguins, increased conspecific density has been correlated with increased stress hormone levels and increased energy expenditure in individual birds, suggesting a cost of colonial breeding. We unravelled the influences of early (genetic and early maternal effects) and rearing environments on chick growth trajectories, stress physiology and survival. Our results suggest that the rearing social environment (rather than biological background) can influence chicks’ phenotype, growth and survival. Especially, chicks reared in high density areas of the colony showed increased weight gain and survival probabilities. These results suggest either a difference in terms of parental quality between individual breeding at high and low social densities or a difference in chick’s competitiveness due to their early life social environment.

Abstract: Coloniality is associated with various benefits and costs for animals affecting their fitness. Breeding colonies are heterogeneous both in terms of physical and social parameters, thus, breeding territories are of different quality relative to their location within the colony. In king penguins, increased conspecific density has been correlated with increased stress level in individual birds, suggesting a cost of colonial breeding. We used a cross-fostering approach to question the relationship linking breeding location, phenotype and reproduction success. We crossfostered eggs shortly after laying within and between high-and low-density colony areas. This design allowed us to unravel the influences of early genetic and maternal effects together with rearing environments on chick growth trajectories, stress physiology and survival. We tested whether chick phenotype is determined at birth to match their early environment or if higher social density conferred an advantage for reproduction.

Abstract: Subsequent to their introduction in the 1950s, Arctic charr Salvelinus alpinus have been able to establish a self-sustaining population that has adapted to the unique conditions of the sub-Antarctic Kerguelen Islands. Here, 48 individuals (198–415 mm) were caught with gillnets and their basic biology and feeding ecology were examined using stable isotope analysis. The Lac des Fougères population split use of littoral and pelagic resources evenly, although larger fish relied more heavily on littoral production and appear to follow the size-dependent life history habitat template seen in many Scandinavian lakes where smaller sized individuals occupy the pelagic zone and larger individuals dominate the littoral habitat. In Kerguelen, Arctic charr mature at the same ages (5.6 years) as Arctic charr in both sub-Arctic and Arctic lakes. Although mortality was average in comparison to comparator sub-Arctic lakes, it was high in comparison to Arctic lakes. Maximal age (>7+) was at the lower end of the range typically seen in sub-Arctic lakes. Although they inhabit a resource-poor environment, Kerguelen Arctic charr showed no evidence of cannibalism. Thus, while Arctic charr can survive and reproduce in the relatively unproductive Kerguelen lake environments, survival and growth nevertheless appear to be traded off against survival and longevity. The uniqueness of the population location and the recency of its introduction suggest that further monitoring of the population has the potential to yield valuable insights into both the adaptability of the species and its likely responses to ongoing large-scale environmental change as represented by climate change.

Abstract: Debris-covered glaciers constitute a large part of the world's cryosphere. However, little is known about their long-term response to multi-millennial climate variability, in particular in the Southern Hemisphere. Here, we provide first insights into the response of a debris-covered glacier to multi-millennial climate variability in the sub-Antarctic Kerguelen Archipelago, which can be compared to that of recently investigated debris-free glaciers. We focus on the Gentil Glacier and present 13 new 36Cl cosmic-ray exposure ages from moraine boulders. The Gentil Glacier experienced at least two glacial advances: the first one during the Late Glacial (19.0–11.6 ka) at ~14.3 ka and the second one during the Late Holocene at ~2.6 ka. Both debris-covered and debris-free glaciers advanced broadly synchronously during the Late Glacial, most probably during the Antarctic Cold Reversal event (14.5–12.9 ka). This suggests that both glacier types at Kerguelen were sensitive to abrupt temperature changes recorded in Antarctic ice cores, associated with increased moisture. However, during the Late Holocene, the advance at ~2.6 ka was not observed in other glaciers and seems to be an original feature of the debris-covered Gentil Glacier, related to either distinct dynamics or to distinct sensitivity to precipitation changes.

Abstract: TOI-216 hosts a pair of warm, large exoplanets discovered by the TESS mission. These planets were found to be in or near the 2:1 resonance, and both of them exhibit transit timing variations (TTVs). Precise characterization of the planets’ masses and radii, orbital properties, and resonant behavior can test theories for the origins of planets orbiting close to their stars. Previous characterization of the system using the first six sectors of TESS data suffered from a degeneracy between planet mass and orbital eccentricity. Radial-velocity measurements using HARPS, FEROS, and the Planet Finder Spectrograph break that degeneracy, and an expanded TTV baseline from TESS and an ongoing ground-based transit observing campaign increase the precision of the mass and eccentricity measurements. We determine that TOI-216c is a warm Jupiter, TOI-216b is an eccentric warm Neptune, and that they librate in 2:1 resonance with a moderate libration amplitude of deg, a small but significant free eccentricity of for TOI-216b, and a small but significant mutual inclination of 1.°2–3.°9 (95% confidence interval). The libration amplitude, free eccentricity, and mutual inclination imply a disturbance of TOI-216b before or after resonance capture, perhaps by an undetected third planet.