Surplus Killing of Magellanic Penguins Spheniscus magellanicus by Puma Puma concolor

ABSTRACT

Surplus killing (SK) by large carnivores may generate high‐intensity mortality events in colonial seabirds. Here, we document repeated predation events involving Magellanic penguins ( Spheniscus magellanicus ) and pumas ( Puma concolor ) in Islote Lobos National Park (ILNP, Río Negro, Argentina). During the 2024–2025 breeding season, only four adult penguins with cervical injuries and no signs of consumption were recorded, precluding their interpretation as SK. In contrast, during the 2025–2026 breeding season, multiple high‐intensity mortality events were recorded at La Pastosa and Isla de los Pájaros, two islets harboring reproductive penguin colonies in the ILNP. Across all documented 2025–2026 events, at least 961 penguins were found dead, including 887 adults and 74 chicks. Carcasses exhibited cervical bite injuries and little or no evidence of consumption, while fresh puma tracks, feces, and direct observations of an adult individual within the colonies strongly supported puma predation. During the four consecutive breeding seasons prior to these events, population monitoring did not record mortality episodes of comparable magnitude and suggested stable population dynamics within the ILNP colonies. The mortality recorded during the 2025–2026 breeding season represented a minimum direct mortality of 3.52% of the local breeding adult population. These records represent the northernmost confirmed case of SK involving Magellanic penguins and pumas, extending the documented geographic range of this interaction by more than 1000 km northwards. They also suggest that repeated SK events may represent an important source of additive mortality for local penguin colonies. Our findings highlight the ecological importance of episodic terrestrial–marine trophic interactions and the need for continued demographic monitoring in coastal breeding systems.