Foraging behaviors of Adélie penguin and emperor penguin given the regional differences in the Ross Sea, Antarctica

Abstract

To identify the dietary composition of both Adélie (Pygoscelis adeliae) and emperor penguin (Aptenodytes forsteri) in four breeding sites, stable carbon (δ13C) and nitrogen (δ15N) isotope analysis of feathers and fatty acid analysis of muscles of penguin chicks were performed. Adélie penguin chicks at Cape Hallett mostly fed on Antarctic krill (Eupausia superba; 65.5 ± 3.5 %) given its large dominance near Cape Hallett, and no significant differences were noted between 2017 and 2018. However, Adélie penguin chicks at Inexpressible Island located near the Terra Nova Bay fed on both Antarctic silverfish (Pleuragramma antarcticum; 42.5 %) and ice krill (Euphausia crystallorophias; 47 %) given the high biomass observed in Terra Nova Bay. On the other hands, No significant difference was noted between both breeding sites of the emperor penguins. In the PCA plot based on penguins, Adélie penguins differed from region to region, and emperor penguins showed more individual differences than regional differences. Emperor penguin chicks predominantly fed on Antarctic silverfish (74.5 ± 2.1 %) at the breeding sites (Cape Washington and Coulman Island), suggesting that diet preference represents the main factor for emperor penguin foraging. In contrast, the diet of Adélie penguin is dependent on prey availability. These study can provide a better understanding of penguin feeding activity in the Ross Sea.