Trade-offs Between Migration and Foraging Success: Winter Behavior of Weddell Seals in the Ross Sea, Antarctica

Wintering periods are vital for the survival and reproductive success of Antarctic animals, yet their winter behaviors remain poorly understood. This study investigates the winter movements and foraging behavior of Weddell seals (Leptonychotes weddellii), an indicator species for the Commission for the Conservation of Antarctic Marine Living Resources, at Terra Nova Bay in the Ross Sea. Using CTD-Satellite Relay Data Loggers, which record head movement and oceanographic data (temperature and salinity), we tracked 48 individuals for three consecutive years (2021–2023) over the migratory period. Of these, 23 seals migrated an average of 339 km (up to 911 km) northeast or southeast between March and early April, while 25 seals remained within 200 km from the summering site restricted at near Terra Nova Bay. Migratory seals exhibited higher prey capture attempts (4.88 ± 1.23 attempts per hour) compared to resident seals (3.86 ± 0.96 attempts per hour), suggesting that long-distance travel provides foraging benefits despite associated energetic costs and risks. Regions frequented by migrants, particularly near continental shelf edges, exhibited warmer water (-1.44 ± 0.37°C) intake at 200–350 m depth, indicative of nutrient-rich conditions. These findings reveal divergent wintering strategies in Weddell seals, highlighting a trade-off between migratory risks and feeding advantages. Long-term integrated monitoring of seal behavior and environmental changes is essential to advancing our understanding of their ecological adaptations and the Antarctic marine ecosystem.