Pumas came back to Patagonia—and met penguins. What happened next surprised scientists.

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For decades, pumas preyed on sheep from ranches along Argentina’s coast, and ranchers hunted them—heavily.Pumas disappeared from the landscape. Then, in 2004, conservationists established Monte León National Park in the region. As expected, once the hunting stopped, the big cats came back. And when they returned, they found a new player in their old neighborhood: Magellanic penguins.

What scientists did not anticipate was that not only would pumas prey on penguins—but that the birds’ seasonal arrival 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 shift in puma behavior for the first time and challenges our assumptions about what happens when large predators return to an ecosystem.

“When we start to rewild the land, the species that are coming back might find a system that is a bit different from the one that they used to inhabit 100 years ago—and they adapt to it,” says Emiliano Donadio, science director at the Fundación Rewilding Argentina and a coauthor of the study.

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

Camera traps unveil puma predation

The researchers didn’t initially set out to study this unique predator-prey relationship. Lead author and ecologist Mitchell 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 former ranchlands. “I went down to Patagonia to understand restoration outcomes broadly. The penguins weren’t the original focus at all,” 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 thought it was minor,” he says. “Maybe just a handful of individuals.”

The team had installed 32 camera traps across 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 pumas were snacking on penguins much more frequently than expected.

“We were getting repeated detections of pumas right around the penguin colony,” Serota recalls. “That’s when it became clear this was not a side note. It was something shaping how these animals were using the landscape.”

A new food web takes shape

Because Magellanic penguins (Spheniscus magellanicus) spend much of their lives at sea, they are unusual prey for a large terrestrial carnivore whose diet is mostly made up of land mammals, such as deer, guanacos (relatives of llamas), and hares. But during their breeding season—roughly September through April—the seabirds huddle on land in large numbers. At Monte León, more than 40,000 breeding pairs nest along a coastline of about two kilometers long.

(What Magellanic penguins are teaching us about survival)

For a puma, whose territory can cover hundreds of square kilometers, this creates an odd situation: an extremely abundant food source, concentrated in a very small area, and available only part of the year. The team found that the population density remained similar—around 13 cats per 100 square kilometers—whether penguins were present or absent. So, penguins did not create more pumas, but reorganized how these cats share space.

Penguin-eating pumas, it turns out, behave quite differently from those who prefer other diets in Patagonia. The study found that bird-eating big cats shared the same area much more frequently than non-bird-eating ones and were not attacking each other as often as one would expect. “In other words, penguin-eating pumas were quite tolerant of the presence of one another,” says Donadio, who is also a National Geographic Explorer.

Such tolerance was a surprise, given the pumas’ loner stereotype. In Patagonia, these big cats are out in the open, as they are the top predator. “Unlike Africa, they don’t need to scrum together to take down prey twice or three times their size. And unlike North America, there are no grizzly bears, black bears or wolves, so these cats are not sneaking around in the trees at night like they are up here,” says Jim Williams, who worked for decades as a biologist with Montana Fish, Wildlife and Parks and wrote about the relationship between the seabirds and big cats in his book Path of the Puma.

To some degree, it makes sense that pumas pounced on the new food source, as penguins are low-risk prey. “Big cats—lions, panthers, cougars, pumas—always prey on the most abundant and vulnerable food sources available,” says Williams, who was not affiliated with the current study. “That’s not shocking from an ecological point of view or a natural behavior, but it is for people who don’t know that penguins and pumas overlap,” he adds.

But the behavior changes are surprising. “We tend to think of pumas as extremely aggressive and intolerant,” Donadio says. “But when food is abundant and concentrated, there’s no need to defend it. They become more socially tolerant,” he adds.

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

Open questions

Donadio says that, so far, surveys suggest the penguin colony has remained stable or even increased since the park was created. What remains uncertain is how the penguin-driven changes in puma behavior ripple through the rest of the ecosystem—especially to guanacos, Patagonia’s dominant herbivore, and the pumas’ primary traditional prey.

Despite the behavioral shifts documented in the study, some important questions remain. The researchers still don’t know how many penguins individual pumas kill, making it difficult to assess the long-term impact of predation onthe colony, even though penguin numbers at Monte León appear stable or increasing so far. Nor can they yet determine whether the high puma density is a temporary or a long-term feature of the ecosystem.

Also, researchers still have to figure out the broader ecological consequences of penguin-driven changes in puma behavior. “We know that the penguin colony has changed where, when, and how pumas obtain their food, but the next step is to understand the ecological implications of that change,” Serota says.

For now, the puma behavior findings demonstrate that when nature is given space, it does not always look back—it improvises. “Restoration doesn’t mean going back to some historical snapshot,” Serota says. “Species are returning to ecosystems that have changed dramatically. That can create entirely new interactions.”

The nonprofit National Geographic Society, committed to illuminating and protecting the wonder of our world, funded Explorer Emiliano Donadio’s work. Learn more about the Society’s support of Explorers.