Unusual dispersion and mortality of Rockhopper Penguins. An event related to adverse marine conditions?

ANNICK MORGENTHALER · ESTEBAN FRERE · ANDREA RAYA REY · CHANTAL TORLASCHI · PAULA CEDROLA · EMANUEL TIBERI · RITA LOPEZ · EMANUEL MENDIETA · MARIA LUISA CARRANZA · SORAYA ACARDI · NATALIE COLLM · PATRICIA GANDINI, · ANA MILLONES

Puerto Iguazu

Congreso; Ornithological Congress of the Americas; 2017

The annual molt of Southern Rockhopper Penguins, Eudyptes chrysocome, usually takes place at their colonies after a premoltingforaging trip. In 2016, an unusual number of Rockhopper Penguins was found molting, and in part subsequentlydying, along the southernmost portion of the Argentine coast, far from the main colonies. To report the extent of this dispersionand mortality event, a survey was conducted between February and May 2016 along the southern Patagonian coast. Atotal of 1039 molting Rockhopper Penguins were reported. The mortality, mainly attributed to starvation, varied between40 and 89%, according to sites. Furthermore, as adverse oceanographic conditions are known to affect prey availabilityand penguin?s survival, chlorophyll a concentrations (as a primary productivity index) and sea surface temperatures wereanalyzed at main foraging grounds. The results showed lower chlorophyll a and sea surface temperature values close to themain 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 supportthe hypothesis of a reduction in primary productivity close to the main colonies prior to the molt, inducing penguins tomove towards more distant foraging grounds, which finally led them to molt later and away from their colonies. Althoughthe oceanographic processes were not fully understood, this event highlights the serious effects that unusual conditions priorto molting can pose on the survival of this endangered penguin, in a context of climate variability.