Unusual number of Southern Rockhopper Penguins, Eudyptes chrysocome, molting and dying along the Southern Patagonian coast of Argentina: pre-molting dispersion event related to adverse oceanographic conditions?
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The annual molt of Southern Rockhopper Penguins, Eudyptes chrysocome, usually takes place at their colonies after a pre-molting foraging trip. In 2016, an unusual number of Rockhopper Penguins was found molting, and in part subsequently dying, along the southernmost portion of the Argentine coast, far from the main colonies. To report the extent of this dispersion and mortality event, a survey was conducted between February and May 2016 along the southern Patagonian coast. A total of 1039 molting Rockhopper Penguins were reported. The mortality, mainly attributed to starvation, varied between 40 and 89%, according to sites. Furthermore, as adverse oceanographic conditions are known to affect prey availability and penguin’s survival, chlorophyll a concentrations (as a primary productivity index) and sea surface temperatures were analyzed at main foraging grounds. The results showed lower chlorophyll a and sea surface temperature values close to the main colonies during 2016 (compared to average 2003–2015). Although these values alone cannot explain such mortality (as similar low values already occurred in some of the previous year without inducing mortality events), our results support the hypothesis of a reduction in primary productivity close to the main colonies prior to the molt, inducing penguins to move towards more distant foraging grounds, which finally led them to molt later and away from their colonies. Although the oceanographic processes were not fully understood, this event highlights the serious effects that unusual conditions prior to molting can pose on the survival of this endangered penguin, in a context of climate variability.
KeywordsEudyptes chrysocome Seabird mortality Ocean productivity Sea surface temperature Southwest Atlantic Ocean Climate change
We thank the staff at Dirección General de Áreas protegidas y Biodiversidad of Secretaria de Ambiente Desarrollo Sostenible y Cambio Climático de Tierra del Fuego (M. L. Flotron, E. D Curto, J. Troche, G. Barreto, E. O. Bauduco, I. Monteagudo Tejedor, G. Gargiulo and F. Encinas) for field and logistical support at Cabo Domingo, Río Grande. We also thank the staff at Consejo Agrario Provincial de Santa Cruz for field and logistical support at Puerto Deseado and Río Gallegos.We are particularly grateful to the numerous observers who shared with us their personal records and greatly enriched this work: J. Fernandez, R. Goronas, C. Moreno, J. Serra, S. Imberti, T. Barrueto, S. Zapata, S. Vidal, and the staff from the Dirección de Turismo de Puerto Santa Cruz. We are also very grateful to Sarah Crofts, Conservation Officer of Falklands Conservation, for sharing personal communications and useful comments on earlier versions of the manuscript. We thank H. Otley and two anonymous reviewers for their comments which greatly helped to improve this work. We thank Dr. A. Piola for sharing his advice concerning the oceanographic conditions that took place at the study site during the study period. Finally, we thank T. A. Gavin for reviewing and improving the English text.
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