Weddell seal dive behavior and rhythmicity from 2010-2012 in the Ross Sea

Diel vertical migrations (DVM) have been well-documented across numerous taxa, with prey descend through the water column during daylight hours to avoid visual predators and feed at the surface at night. However, the ability of marine mammals such as Weddell seals (Leptonychotes weddellii) to follow prey to depths is likely constrained by limited breath-hold capacities and the physiological consequences of pushing aerobic thresholds. In particular, dives that exceed the aerobic dive limit require exponentially longer surface recuperation times to clear lactate byproducts from circulation. This is time that the animals then cannot spend foraging. In this study, we assess the circadian organization of the Weddell seal's dive efforts and when animals make their longest/deepest (most 'extreme') dives that far exceed aerobic thresholds. Sixty-two adult Weddell seals were instrumented with satellite linked relay loggers in the Ross Sea to collect behavioral information across the austral winter. Daily activities are likely to shift across the year in a highly-seasonal polar environment, and through this 'natural experiment' we test how free-ranging seals alter foraging behavior during Polar Day and Night (continuous light, LL and dark, DD, respectively) and varying light/dark (LD) cycling across the year.