Habitat Use by Weddell Seals and Emperor Penguins Foraging in the Ross Sea, Antarctica1

Abstract

The only apex predators that live year-round at high latitudes of the Ross Sea are the Weddell seal and emperor penguin. The seasonal distribution, foraging depths, and diet of these two species appear to overlap. What makes it possible for emperor penguins and Weddell seals to co-exist at high latitude throughout the winter when other marine tetrapods apparently cannot? Both species have similar adaptations for exploitation of the deep-water habitat, forage on the same species, and routinely make long and deep dives. Yet, despite these similarities, there is probably little trophic overlap between the adults of both species due to geographical and seasonal differences in habitat use. For example, during the winter months while female emperor penguins are ranging widely in the pack ice, adult seals are foraging and fattening for the upcoming summer fast, literally beneath the feet of the male penguins. However, there is more extensive overlap between juvenile seals and adult penguins, and shifts in prey abundance and/or distribution would likely affect these two groups similarly. In contrast, juvenile penguins appear to avoid inter- and intra- specific competition by leaving the Ross Sea once they molt.