By SciTechDaily, Feb. 4, 2026
https://scitechdaily.com/thousands-of-penguins-are-being-killed-and-the-reason-is-complicated/
https://scitechdaily.com/thousands-of-penguins-are-being-killed-and-the-reason-is-complicated/
A Magellanic penguin carcass showing signs of predation by puma at the Monte León National Park colony.
Credit: © Joel Reyero 2024
Pumas are back in Patagonia, penguins are paying a price—but climate-driven breeding failures may be the real extinction risk.
Penguins along Argentina’s Patagonian coast are facing an unexpected threat as pumas return to parts of their historic range. A new study closely examines how this predator comeback affects the long term survival of the penguin colony.
Over a four year period, researchers estimate that pumas at a national park killed more than 7,000 adult penguins, representing about 7.6% of the colony’s adult population. Many of the birds were left uneaten, suggesting that not all were killed for food.
Despite the striking number of deaths, the study finds that puma predation alone is unlikely to push the colony toward collapse. Instead, factors such as poor breeding success and lower survival among young penguins pose a much greater risk to the population’s future.
The research was published today (5 February) in the Journal for Nature Conservation.
The research was published today (5 February) in the Journal for Nature Conservation.
A Conservation Dilemma in Patagonia
Should conservation efforts prioritize one iconic species if doing so may harm another, especially in ecosystems still recovering from past human activity? This question is at the heart of an ongoing challenge at Monte Leon National Park along Argentina’s Patagonian coast.
The issue has emerged as wildlife returns to landscapes once heavily altered by people. In this case, the recovery of a top predator has created unexpected consequences for a vulnerable prey species.
Should conservation efforts prioritize one iconic species if doing so may harm another, especially in ecosystems still recovering from past human activity? This question is at the heart of an ongoing challenge at Monte Leon National Park along Argentina’s Patagonian coast.
The issue has emerged as wildlife returns to landscapes once heavily altered by people. In this case, the recovery of a top predator has created unexpected consequences for a vulnerable prey species.
A Magellanic penguin at the nest, built under bushes in Monte León National Park.
Credit: © Joel Reyero 2024
Pumas Return to a Changed Landscape
After cattle ranching ended in southern Argentina in 1990, pumas (Puma concolor) began reclaiming parts of their historic range. Their return brought them into contact with Magellanic penguins (Spheniscus magellanicus), which had previously moved from offshore islands to the mainland when terrestrial predators were absent.
The penguins, which lack strong defenses against land predators, became easy targets. Until recently, however, scientists did not know how much impact this new predator-prey interaction was having on penguin population numbers.
After cattle ranching ended in southern Argentina in 1990, pumas (Puma concolor) began reclaiming parts of their historic range. Their return brought them into contact with Magellanic penguins (Spheniscus magellanicus), which had previously moved from offshore islands to the mainland when terrestrial predators were absent.
The penguins, which lack strong defenses against land predators, became easy targets. Until recently, however, scientists did not know how much impact this new predator-prey interaction was having on penguin population numbers.
An adult puma leaving the penguin nesting area, and a penguin lies dead behind it. (This study did not collar the pumas).
Credit: © Joel Reyero 2024
Tracking Penguin Losses Over Time
Since the park was established in 2004, scientists from the Centro de Investigaciones de Puerto Deseado of the Universidad Nacional de la Patagonia Austral, together with rangers from Monte Leon National Park, have closely monitored penguin colonies. Over a four year period (2007-2010), they documented penguin carcasses linked to puma attacks.
For the latest study, the team partnered with researchers from Oxford University’s Wildlife Conservation Research Unit (WildCRU) to analyze the long term implications of these findings.
Infographic of the study’s findings.
Credit: Sarah Markes
Thousands of Penguins Killed
Based on carcass counts, researchers estimated that more than 7,000 adult penguins were killed during the four year study period. Many of the birds were only partially eaten or left untouched, suggesting they were not all killed for food. This total represents about 7.6% of the adult population (around 93,000 individuals).
Lead author Melisa Lera, a postgraduate student at WildCRU, Oxford University, said: “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’. It is comparable to what is seen in domestic cats when prey are abundant and/or vulnerable: ease of capture can lead to cats hunting more birds, even when they do not end up actually eating them. We needed to understand if the penguin colony’s persistence could be threatened due to this behavior.”
Based on carcass counts, researchers estimated that more than 7,000 adult penguins were killed during the four year study period. Many of the birds were only partially eaten or left untouched, suggesting they were not all killed for food. This total represents about 7.6% of the adult population (around 93,000 individuals).
Lead author Melisa Lera, a postgraduate student at WildCRU, Oxford University, said: “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’. It is comparable to what is seen in domestic cats when prey are abundant and/or vulnerable: ease of capture can lead to cats hunting more birds, even when they do not end up actually eating them. We needed to understand if the penguin colony’s persistence could be threatened due to this behavior.”
Fieldwork included counting carcasses and measuring body dimensions to better assess the impacts of puma predation.
Credit: © Esteban Frere 2007
Modeling the Colony’s Future
When researchers modeled the population data, the results suggested that puma predation alone was unlikely to cause the penguin colony at Monte Leon Park to collapse. Instead, the long term outlook depended more heavily on breeding success and the survival of young penguins.
Extinction scenarios only appeared when the models combined very low juvenile survival, with roughly 20% failing to reach adulthood, and extremely poor reproduction, limited to a maximum of one chick per breeding pair. In these situations, heavy puma predation worsened the outcomes but was not the primary driver.
Study co-author Dr. Jorgelina Marino (WildCRU, Oxford University) said: “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.”
Modeling the Colony’s Future
When researchers modeled the population data, the results suggested that puma predation alone was unlikely to cause the penguin colony at Monte Leon Park to collapse. Instead, the long term outlook depended more heavily on breeding success and the survival of young penguins.
Extinction scenarios only appeared when the models combined very low juvenile survival, with roughly 20% failing to reach adulthood, and extremely poor reproduction, limited to a maximum of one chick per breeding pair. In these situations, heavy puma predation worsened the outcomes but was not the primary driver.
Study co-author Dr. Jorgelina Marino (WildCRU, Oxford University) said: “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.”
Climate and Broader Ecosystem Pressures
Because breeding success and juvenile mortality emerged as key factors, the researchers emphasize the need to better understand how environmental conditions affect penguin reproduction. Factors such as nutrient availability, food supply, and temperature are all known to be influenced by climate change and could play a critical role in future population stability.
The situation in Patagonia reflects a broader global trend. As land predators expand into coastal areas, other mainland seabird colonies may also face new risks. For example, non-native feral hogs have become major predators of loggerhead sea turtle eggs along the Georgia coast, USA, while coyotes in eastern North America are increasingly occupying coastal barrier islands and reshaping those ecosystems.
Because breeding success and juvenile mortality emerged as key factors, the researchers emphasize the need to better understand how environmental conditions affect penguin reproduction. Factors such as nutrient availability, food supply, and temperature are all known to be influenced by climate change and could play a critical role in future population stability.
The situation in Patagonia reflects a broader global trend. As land predators expand into coastal areas, other mainland seabird colonies may also face new risks. For example, non-native feral hogs have become major predators of loggerhead sea turtle eggs along the Georgia coast, USA, while coyotes in eastern North America are increasingly occupying coastal barrier islands and reshaping those ecosystems.
The Need for Ongoing Monitoring
The authors stress that long term monitoring is essential to detect early warning signs of population decline and guide effective management decisions. At Monte Leon National Park, authorities continue to track both puma and penguin populations as they navigate the complex consequences of ecosystem recovery.
The authors stress that long term monitoring is essential to detect early warning signs of population decline and guide effective management decisions. At Monte Leon National Park, authorities continue to track both puma and penguin populations as they navigate the complex consequences of ecosystem recovery.
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