Monte León National Park Pumas Threaten Magellanic Penguins

Monte León National Park on Argentina’s Patagonian coastline faces a familiar conservation dilemma: how should managers respond when the recovery of a native predator puts pressure on a prey species that colonised the area only because predators had disappeared?

Following the end of cattle ranching in southern Argentina around 1990, pumas (Puma concolor) started to reoccupy sections of their former range.

Meanwhile, Magellanic penguins (Spheniscus magellanicus) had begun breeding on the mainland after previously depending on nearby islands for protection.

Because they had effectively lived on land without major terrestrial predators, the penguins proved easy prey once pumas returned.

Measuring losses in the penguin colony

Researchers from the Centro de Investigaciones de Puerto Deseado, alongside park rangers, have monitored the park’s penguins since Monte León was established in 2004.

Between 2007 and 2010, they additionally recorded penguin carcasses believed to have been killed by pumas.

For the latest study, the researchers joined forces with Oxford University’s Wildlife Conservation Research Unit (WildCRU) to examine what those figures could indicate for the colony’s long-term prospects.

The estimated toll is stark: more than 7,000 adult penguins were killed during the four-year period. This equates to about 7.6% of the adult population, estimated at roughly 93,000 birds.

The researchers were particularly concerned that most penguins had not been eaten in full. This implies that many may not have been killed solely to provide food for the pumas.

“Surplus killing” by pumas

“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,” said study lead author Melisa Lera, a postgraduate student at WildCRU.

“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.”

Lera said the researchers aimed to determine whether this behaviour could endanger the continued existence of the penguin colony.

When prey is especially simple to catch, predators may kill more animals than they need. Although this can appear catastrophic, it does not necessarily mean the population will collapse in the long term.

Could pumas drive Magellanic penguins to extinction?

The unexpected finding was that population models did not indicate pumas alone were likely to eliminate Monte León’s penguins.

Rather, the models showed that the colony was considerably more vulnerable to two factors: penguin breeding performance, or reproductive success, and the number of juveniles that survive to enter the adult population.

Extinction occurred only under theoretical worst-case combinations, such as a sharp fall in juvenile survival alongside very low reproductive output.

The study defines this as a maximum of one chick per pair. Under those conditions, intense puma predation worsened the prospects, but was not the only cause.

Carnivores encountering unfamiliar prey

The issue has relevance beyond Patagonia, as these encounters could become increasingly frequent when ecosystems recover, predators extend their ranges and animals begin interacting in ways not seen for a long time.

“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,” said study co-author Jorgelina Marino from WildCRU.

The article identifies comparable cases elsewhere, including feral hogs heavily preying on loggerhead sea turtle eggs along Georgia’s coast and coyotes reaching coastal barrier islands in eastern North America.

What Monte León National Park needs next

As breeding success and juvenile survival seem to be so significant, the authors say the next priority is identifying the factors that determine them.

The team plans to investigate environmental conditions, including food availability, nutrients and temperature, which can all be affected by climate change.

Puma predation is substantial, real and disturbing, yet the colony’s future may depend equally-or even more-on the survival of chicks and young birds.

Park authorities will continue observing both pumas and penguins so that any serious demographic decline can be detected early enough for action to be taken.