A new sex determination method using morphological traits in adult chinstrap and gentoo penguins on King George Island, Antarctica

Abstract

Sex identification is a fundamental work for studying the behavioural ecology in animals. Although recent molecular sexing techniques have enabled us to distinguish the sexes, it is still convenient to discriminate the sexes with morphological traits especially when surveying colonial animals under harsh field conditions. For chinstrap and gentoo penguins in Antarctica, previous studies developed several morphological discriminant functions, but many studies did not adopt molecular sexing methods for deciding sexes. In this study, we tested previous morphology-based sexing methods to determine their applicability to adult chinstrap and gentoo penguins breeding at Narębski Point (Antarctic Specially Protected Area No. 171) in Barton Peninsula on King George Island. Furthermore, we aimed to develop alternative morphological features to reliably discriminate penguin sexes. Our results showed that the accuracies of previously suggested functions varied among discriminant functions in both species (approximately 64–82%). Here, we developed new functions to discriminate sexes in chinstrap and gentoo penguins, using bill and middle toe size which are easily acquired and less error-prone. The classification accuracy of the discriminant functions derived in this study was >90% for both species. Also, it was successfully applicable to another chinstrap population.