Long-term population trends of gentoo penguins in relation to environmental factors at Esperanza/Hope Bay, Antarctic Peninsula

Abstract

Pygoscelis species are considered indicators of the Antarctic ecosystem, and monitoring their populations is essential for understanding ecosystem dynamics. Their populations are strongly influenced by environmental conditions and food availability, particularly Antarctic krill (Euphausia superba), although the magnitude and direction of these effects may vary among species and sites. Contrasting population trends have been reported for gentoo penguins (Pygoscelis papua) along the western Antarctic Peninsula and adjacent islands. We analysed population trends over 14 breeding seasons (2010/11–2024/25) in a colony at the tip of the Antarctic Peninsula (Esperanza/Hope Bay). We also examined relationships with environmental and anthropogenic variables, given the colony’s proximity to a permanent Argentinian station. For this, the colony was classified into zones of high (HDZ) and low (LDZ) anthropogenic impact. Breeding success and diet composition (via stomach lavage) were also evaluated. An increasing trend in breeding pairs was observed, with contrasting patterns between zones. The increase in the HDZ was markedly higher than that observed in the LDZ. However, breeding success did not increase among seasons and did not differ between zones. Diet composition shifted over time from a higher proportion of fish to dominance by Antarctic krill, consistent with reports of increased krill availability in the region. Finally, the rise in breeding pairs was positively associated with reduced sea ice extent during the non-breeding period, consistent with the ice-intolerant life history of this species and suggesting facilitated dispersal among colonies.