| Summary: | During austral summers, crabeater seals (Lobodon carcinophagus) preferentially target the large zooplankton and krill that are abundant in surface waters. However, during winter months, seals forage deeper and closer to the seafloor, where their preferred prey aggregate. As a result, winter foraging is associated with a much greater proportion of dives longer than the seals’ calculated aerobic dive limit (cADL, 6.1 ‐ 11.8 min). To determine if aerobic capacity constrains winter foraging activities, we examined the relationship between the cADL and dive depth, bottom time, and bathymetric depth in 34 crabeater seals ranging in mass from 118 – 365 kg. While fewer than 10% of dives shallower than 150 m were anaerobic, this percentage exceeded 30% for dives deeper than 250 m. These deeper dives were most common in late winter and during the day. Interestingly, larger animals made more anaerobic dives, perhaps because they dove closer to the seafloor than smaller animals. In combination, our findings suggest that body size and physiological capacity influence crabeater seal foraging strategies, particularly during winter. These findings have implications for crabeater seal foraging success, particularly if warming along the Antarctic Peninsula causes changes in the abundance and depth distribution of preferred prey items. This research was funded by NSF OPP # 0003956 & 0006429 to JMB and DPC.
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