Extra-pair paternity and intraspecific brood parasitism in the Gentoo Penguin (Pygoscelis papua) on Elephant Island, Antarctica

Recent studies have shown that many species of apparently monogamous birds engage in extra-pair copulation (EPC). Penguins have intense shared parental care for their young, and thus have been considered monogamous. The present study aimed to assess the reproductive system of the gentoo penguin (Pygoscelis papua) on Elephant Island, Antarctica, by evaluating extra-pair paternity (EPP) and intraspecific brood parasitism (IBP). Our data revealed high rates of EPC, with approximately 48.75% of chicks originating from EPP, corresponding to 72.5% of nests. IBP was found for ~ 17% of the gentoo penguin nests, a behavior previously recorded only for Magellanic penguins (~ 6%). The reasons for these behaviors are not clear, as increased genetic diversity or sex bias of offspring was not found. Thus, social and ecological aspects could be more important for determining the costs and benefits of EPP. Other genetic and ecological aspects must be investigated in future studies, such as genetic compatibility of the immune system or fluctuations of the EPP rate due to environmental conditions.