Meeting Abstract
Weddell seals (Leptonychotes weddellii) are among the deepest diving pinnipeds (seals, sea lions, walrus), and adult Weddell seal dive physiology is relatively well understood. However, little is known about their physiology and development as pups during nursing and the transition to independence. The aim of this study was to investigate the development of diving capabilities in Weddell seal pups throughout early ontogeny. We calculated total body oxygen stores (TBO2) from blood and muscle sampled longitudinally at 1, 3, 5 and 7 weeks of age. These data were correlated with diving behavior measured with time-depth recorders. We found that Weddell seal pups started (at 1w) with mass-specific TBO2 values (75.43±3.87 mL O2 kg-1) that were not significantly different from those reported for adults; this is unique among seal species. We hypothesized that TBO2 would increase with dive experience rather than simply calendar age, but instead found that mass (r2=0.96) and age (r2=0.89) were more significantly correlated with total TBO2 (P<0.0001) than time spent in water (P=0.006, r2=0.59) or dive duration (P=0.007, r2=0.38). Pups spent the majority of their time in the water near the surface during dependence; this ‘exercise’ may have signaled oxygen store development even though pups were not likely exposed to hypoxia. Relatively high mass-specific TBO2 values may provide a ‘head start’ for diving and facilitate the successful transition to independent foraging in Weddell seals. Later exposure to hypoxia combined with diving experience may be the key to the subsequent increases in total TBO2 observed in yearlings and juveniles of this species.
