Winter habitat use and foraging behavior of crabeater seals along the Western Antarctic Peninsula

We quantified the winter and spring movement patterns and foraging behavior of adult crabeater seals (Lobodon carcinophagus), and the influence of sea ice and bathymetry on their foraging behavior. Thirty-four seals (16 M 18 F) were outfitted with Satellite Relay Data Loggers (SRDLs) in the Marguerite Bay Region of the Antarctic Peninsula (∼67°S, 67°W) during the austral winters of 2001 and 2002. Tags transmitted position and dive information for between 4 and 174 days. Overall, winter activity patterns differed significantly from previously reported data collected during the summer: seals in this study dived deeper (92±0.2 m, range 6–713 m) and longer (5.26 min±0.6, range 0.2–23.6 min), hauled out during the night rather than the day, and showed seasonal shifts in foraging patterns consistent with foraging on vertically migrating prey. While these patterns were more pronounced in 2001 than in 2002, there were no strong differences in patterns of habitat use between the 2 years. Some animals made long distance movements (furthest movements 664 km to northeast, 1147 km to southwest), but most seals remained within 300 km of their tagging location. Within the Marguerite Bay/Crystal Sound region, seals appeared to favor foraging locations on the continental shelf within the 50 to 450 m depth range, with a tendency to avoid depths of 600 m or greater. In both years, seals remained deep within the pack ice throughout the winter, and did not move into regions with less ice cover. Seals were more likely to be located in shallow water where the bathymetric gradients were greatest, and in areas of higher sea-ice concentration. In combination, these findings suggest that crabeater seals alter their behavior to accommodate seasonal and/or annual fluctuations in seasonal sea ice and associate with bathymetric features likely to concentrate prey patches.