Using latent behavior analysis to identify key foraging areas for Adélie penguins in a declining colony in West Antarctic Peninsula

Abstract

Adélie penguins are considered indicators of Antarctic ecosystems. Their populations have declined by more than 50% in the West Antarctic Peninsula, an area strongly affected by global warming, and that concentrates most of Antarctic krill harvesting. The use of high-resolution data to identify foraging areas regularly used by krill predators could provide valuable information for current discussions on the development of small-scale management and conservation measures for this region. We used information on the foraging trips of 57 individuals breeding in King George Island, tracked over 2019/2020, 2020/2021 and 2021/2022 breeding seasons during the chick-rearing stage, to identify their key foraging areas. Using an accelerometry-based latent behavioral analysis approach, we identified an area within 10 km of the colony consistently used by over 60% of the population throughout and between seasons. We also observed that almost 20% of the population uses the area near a seamount located 35 km from the colony for foraging, mainly during the late guarding phase when chick energy demands are highest or the effects of prey depletion might become more evident. The distances and duration of trips and the area explored increased as the season progressed and varied between seasons, consistent with annual differences in krill availability observed in the region. Foraging dives comprise roughly 40% of the dives performed during foraging trips, irrespective of the stage of the chick-rearing period, or the season analyzed. Our results emphasize the need to understand how variability in environmental conditions, prey availability, and energetic demands affect how predators use space, and the role that bathymetric features might play in providing reliable foraging grounds, for penguins, in a rapidly changing region.