Regional Differences in the Diets of Adelie and Emperor Penguins in the Ross Sea, Antarctica

Abstract

Simple Summary Stable isotope analysis (SIA) and Stable isotope analysis in R (SIAR) model were used to identify the diet composition and regional differences of Adelie and Emperor penguins in Ross Sea region. Adelie Penguin at Cape Hallett fed on Antarctic krill and Adelie Penguin at Inexpressible Island fed on ice krill and Antarctic silverfish. Emperor Penguins fed on Antarctic silverfish regardless breeding site. Therefore, Adelie Penguin showed regional difference in the diet and Emperor Penguin showed no regional differences in the diet. These diet composition of penguins is affected by competition and distribution of prey, it is important to study the diet of penguins in relation to the sympathetic food sources needed to understand the changes in energy flows and Ross Sea ecosystems due to climate change. To identify the dietary composition and characteristics of both Adelie (Pygoscelis adeliae) and Emperor (Aptenodytes forsteri) penguins at four breeding sites, we performed stable carbon (delta C-13) and nitrogen (delta N-15) isotope analysis of down samples taken from penguin chicks. Adelie Penguin chicks at Cape Hallett mostly fed on Antarctic krill (Euphausia superba; 65.5 +/- 3.5%), a reflection of the prevalence of that species near Cape Hallett, and no significant differences were noted between 2017 and 2018. However, Adelie Penguin chicks at Inexpressible Island, located near Terra Nova Bay, fed on both Antarctic silverfish (Pleuragramma antarctica; 42.5%) and ice krill (Euphausia crystallorophias; 47%), reflecting the high biomass observed in Terra Nova Bay. Meanwhile, no significant difference was noted between the two breeding sites of the Emperor Penguin. Emperor Penguin chicks predominantly fed on Antarctic silverfish (74.5 +/- 2.1%) at both breeding sites (Cape Washington and Coulman Island), suggesting that diet preference represents the main factor influencing Emperor Penguin foraging. In contrast, the diet of the Adelie Penguin reflects presumed regional differences in prey prevalence, as inferred from available survey data.