An ecologically important leopard seal aggregation site in South Bay, Livingston Island

Abstract Leopard seals ( Hydrurga leptonyx ) are apex predators that shape Southern Ocean food webs through consumption of a wide range of prey. Despite their ecological importance and broad circumpolar distribution, consistent aggregation sites are poorly documented. During the 2025–2026 austral summer, we identified and monitored a previously undocumented aggregation of leopard seals in South Bay, Livingston Island, Antarctica. Over two months (Nov–Jan), we conducted land- and ice-based observations, photo-identification, and biological sampling as part of the first systematic study of leopard seals at this site. We recorded 33 unique individuals in South Bay, which is a relatively high seasonal count compared to recent reports from other known aggregations over the past decade. Most individuals (91%) were adults in good to excellent body condition. We had repeated sightings of nine individuals, indicating potential seasonal residency to South Bay. Feeding activity, including predation on penguins, flying seabirds and krill, was observed and confirmed with scat analysis. Reproductive behaviors, including male–female co-occurrence on icebergs, mating calls, and the presence of a visibly pregnant female, were documented. Together, the repeated site use, local foraging, and reproductive activities suggest that South Bay is an ecologically significant, multi-use habitat for leopard seals. These findings provide a baseline for long-term leopard seal monitoring and may inform consideration of ecologically significant habitats in the design of Antarctic Specially Protected Areas (ASPAs).