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Defenceless penguins are being killed en masse as puma populations recover in Monte Leon National Park in Argentina’s ruthlessly wild Patagonia.
After cattle ranching was abandoned in the country’s south in the 1990s, pumas began recolonising parts of their historical range. At the same time, Magellanic penguin colonies have expanded from nearby islands to the mainland, where “terrestrial predators” had previously been absent.
It’s resulted in what scientists are calling a “conservation dilemma” that could see penguin colonies dwindle in the region. Now, a study by Oxford University has quantified the risk of long-term penguin population survival.
How pumas became these penguins’ biggest threat
Researchers from the Centro de Investigaciones de Puerto Deseado of the Universidad Nacional de la Patagonia Austral and rangers from the Monte Leon National Park have been monitoring penguin populations in the park.
Over four years (2007 to 2010) they counted the number of penguin carcasses attributed to puma predation. They then collaborated with Oxford University’s Wildlife Conservation Research Unit to analyse the data.
The new study, published in the Journal for Nature Conservation, estimates that more than 7,000 adult penguins were killed over the four-year period, but most of them weren’t fully eaten. This is around 7.6 per cent of the adult population.
Lead author Melisa Lera says the number of carcasses showing signs of predation in the colony is “overwhelming”.
“The fact that they were left uneaten means pumas were killing more penguins than they required for food,” she adds. “This is consistent with what ecologists describe as ‘surplus killing’.”
This is similar to domestic cats which can end up hunting more birds – even if they don’t eat them – because they’re abundant and vulnerable.
Will penguins in Patagonia become extinct?
Researchers carried out modelling on the data and concluded that pumas alone were “unlikely” to drive the colony at the national park to extinction.
The penguins’ future appears to be more sensitive to factors such as reproductive success and juvenile survival – but high puma predation will exacerbate these outcomes.
“This study captures an emerging conservation challenge, where recovering carnivores are encountering novel prey,” says co-author Dr Jorgelina Marino.
“Understanding how these dietary shifts affect both predators and prey is essential to inform conservation.”
Since the models identified breeding success and mortality of the juveniles as some of the key determinants of population viability, the authors highlight the need to understand how environmental factors such as nutrients, food and temperature – known to be influenced by climate change – may affect the penguins’ reproductive success.
The Park authorities continue to monitor puma and penguin populations.