The pumas returned to Patagonia and met the penguins. What happened next, scientists were amazed.

For decades, pumas preyed on flocks of sheep along Argentina’s coast, and ranchers hunted many of them. Pumas disappeared from the landscape. Then, in 2004, conservationists established the Monte Leon National Park in the area. As expected, after the hunting stopped, the big cats returned. And when they returned, they found a new player in their old neighborhood: the Magellanic penguin.

What the scientists didn’t anticipate was that the pumas would not only hunt the penguins—but that the seasonal arrival of the birds would reorganize how these famously solitary cats move, interact, and hunt across the landscape. A new study published today in the journal Proceedings of the Royal Society b documents this change in puma behavior for the first time and challenges our assumptions about what happens when large predators return to ecosystems.

“When we start to reforest the land, the returning species may find a slightly different system than the one they inhabited 100 years ago – and they adapt to it,” says Emiliano Donadio, science director at Condacion Rewilding Argentina and co-author of the study.

(How penguin ‘genocide’ led to historic new protections in Argentina)

Camera trap unveils puma hunting

Researchers didn’t initially set out to study this unique predator-prey relationship. Lead author and ecologist Michel Serota, then at the University of California Berkeley, was working with Fundación Rewilding Argentina to study how wildlife responds when human pressures are removed from old farmland. “I went to Patagonia to understand the consequences of restoration more broadly. Penguins were not the original focus,” he says.

In 2023, Serota and his colleagues reported that the big cats were actually feeding on the gawky birds. “That interaction was known, but we found it to be small,” he says. “Maybe a handful of people.”

The team installed 32 camera traps in the park and tracked 14 adult pumas (Puma concolor) with GPS collars between September 2019 and January 2023. Combining that data with field observations, the researchers quickly realized that the pumas were feeding on the penguins more often than expected.

“We were frequently discovering pumas around the penguin colony,” recalls Serota. “That’s when it became clear that this wasn’t a side note. It was about shaping how these animals were using the landscape.”

A new food web takes shape

Because the Magellanic penguin (Spheniscus Magellanicus) Spending most of their lives at sea, they are unusual prey for large terrestrial carnivores whose diet consists mostly of land mammals such as deer, guanacos (relatives of llamas) and rabbits. But during their breeding season—roughly September through April—seabirds congregate on land in large numbers. At Monte Leon, more than 40,000 breeding pairs nest along a nearly two-kilometer stretch of coastline.

(What Magellanic Penguins Are Teaching Us About Survival)

For a puma, whose territory can cover hundreds of square kilometers, this creates a unique situation: an extremely abundant food source, concentrated in a very small area, and available only part of the year. The team found that population density remained the same – about 13 cats per 100 square kilometers – whether penguins were present or absent. So, the penguins didn’t create more pumas, but reorganized how these cats shared space.

The penguin-eating puma, it turns out, behaves quite differently from the other food lovers in Patagonia. The study found that bird-eating big cats shared the same territory more often than non-bird-eaters and did not attack each other. Donadio, also a National Geographic explorer, says, “In other words, the penguin-eating pumas were very tolerant of each other’s presence.

Such tolerance was a surprise given the lonely stereotype of pumas. In Patagonia, these big cats are out in the open, as they are top predators. “Unlike in Africa, they don’t have to huddle together to take prey two or three times their size. And unlike in North America, there are no grizzly bears, black bears or wolves, so these cats don’t hide in the trees at night like they do here,” says Jim Williams, who worked for decades, writing about the relationship between Willish Park and Mont Life. Seabirds and Big Cats in his book Way of the Puma.

In part, this has led to pumas hitting a new food source, as penguins are less vulnerable prey. “Big cats — lions, panthers, cougars, pumas — always prey on the most abundant and scarce food sources available,” says Williams, who is not affiliated with the current study. “It’s not shocking from an ecological point of view or natural behavior, but it’s for people who don’t know that penguins and pumas overlap,” he adds.

But the behavior change is amazing. “We think of puma as very aggressive and intolerant,” says Donadio. “But when food is abundant and concentrated, there’s no need to defend it. They are socially tolerant,” he adds.

(What one photographer learned after spending nearly a year with pumas)

Open questions

Donadio says surveys so far have shown that penguin colonies have remained stable or increased since the park was built. How penguin-driven changes in puma behavior will affect the rest of the ecosystem—especially guanacos, Patagonia’s dominant vegetation, and pumas’ primary traditional prey—is uncertain.

Despite the behavioral changes documented in the study, some important questions remain. Although the number of penguins at Monte Leon appears to be stable or increasing, researchers still do not know how many penguins are killed by individual pumas, making it difficult to assess the long-term impact of hunting on the colony. Neither can determine whether high puma density is a temporary or long-term feature of the ecosystem.

Also, researchers have yet to explore the broader ecological consequences of penguin-driven changes in puma behavior. “We know that penguin colonies have changed in terms of where, when, and how pumas get their food, but the next step is to understand the ecological implications of that change,” Serota says.

For now, puma behavioral findings show that when nature is given space, it doesn’t always look back—it improves. “Restoration doesn’t mean going back to some historical snapshot,” says Serota. “Species are returning to ecosystems that have changed dramatically. This can create entirely new interactions.”

The National Geographic Society, a nonprofit committed to illuminating and preserving the wonders of our world, funded the work of explorer Emiliano Donadio. Learn more about the Society’s support for researchers.