Pumas have returned to Argentina's Patagonia after decades away, preying on Magellanic penguins that had no experience with land predators. Researchers estimate over 7,000 adult penguins were killed in four years, though many carcasses were left uneaten. Population models indicate puma attacks alone won't doom the colony, but breeding and juvenile survival pose bigger threats.
In Monte Leon National Park on Argentina's Patagonian coast, the return of pumas following the end of cattle ranching in 1990 has introduced a new dynamic to the local ecosystem. These big cats, reclaiming their historic range, have encountered Magellanic penguins that shifted from offshore islands to the mainland in the absence of terrestrial predators. The penguins, lacking defenses against such carnivores, have become vulnerable targets.
Monitoring began when the park was established in 2004, with researchers from the Centro de Investigaciones de Puerto Deseado at Universidad Nacional de la Patagonia Austral collaborating with park rangers. From 2007 to 2010, they documented penguin carcasses from puma attacks. Partnering with Oxford University's Wildlife Conservation Research Unit, the team analyzed the data for a study published in the Journal for Nature Conservation.
The findings revealed more than 7,000 adult penguins killed over those four years, equating to about 7.6% of the roughly 93,000 adults in the colony. Many birds were partially eaten or abandoned entirely, a behavior known as surplus killing. Lead author Melisa Lera, a postgraduate at WildCRU, noted: "The number of carcasses showing signs of predation we found in the colony is overwhelming, and the fact that they were left uneaten means pumas were killing more penguins than they required for food. This is consistent with what ecologists describe as 'surplus killing'."
However, models suggest puma predation won't drive the colony to extinction on its own. Greater risks stem from low breeding success and poor juvenile survival rates. Extinction scenarios only arise with extreme conditions, like 20% juvenile failure to reach adulthood and pairs producing at most one chick. Co-author Dr. Jorgelina Marino emphasized: "This study captures an emerging conservation challenge, where recovering carnivores are encountering novel prey. Understanding how these dietary shifts affect both predators and prey is essential to inform conservation."
Environmental factors, including climate change impacts on food supply and temperatures, could further hinder penguin reproduction. Similar predator-prey shifts are seen elsewhere, such as feral hogs targeting sea turtle eggs in Georgia, USA, and coyotes invading coastal islands in eastern North America. Authorities at Monte Leon continue tracking both species to guide future management.
