For decades, pumi preyed on sheep from ranches along the coast of Argentina, and ranchers hunted them—largely. The knobs disappeared from the landscape. Then, in 2004, conservationists established the 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: the Magellanic Penguins.
What the scientists didn’t anticipate was that not only would the pumas prey on the 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 change 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 save the land again, the species that are coming back can find a system that is a bit different from the one they lived in 100 years ago—and adapt to it,” says Emiliano Donadio, director of science at the Fundación Rewilding Argentina and co-author of the study.
(How a penguin ‘massacre’ led to historic new protections in Argentina)
Camera traps reveal puma predation
Researchers did not 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 reacts when human pressures are removed from previous pastures. “I went down to Patagonia to understand the results of the restoration in a broad way. The penguins were not the original focus at all,” he says.
In 2023, Serota and his colleagues reported that the big cats were actually eating the gawky birds. “That interaction was known, but we thought it was minor,” he says. “Maybe just a few individuals.”
The team installed 32 camera traps around 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 drinking the penguins much more often than expected.
“We were getting repeated sightings of pumas around the penguin colony,” Serota recalls. “That’s when it became clear that this was not a side note. It was something that shaped how these animals were using the landscape.”
A new food web takes shape
Because the Magellanic penguins (Spheniscus magellanicus) spending most of their lives at sea, they are unusual prey for a large terrestrial carnivore whose diet is made up mostly of land mammals, such as deer, guanacos (relatives of the llama), and hares. But during their breeding season—between September and April—the seabirds flock to land in great numbers. In Monte León, more than 40,000 breeding pairs nest along a coastline of about two kilometers.
(What the Magellanic Penguins are teaching us about survival)
For a puma, whose territory can cover hundreds of square kilometers, this creates a strange situation: an extremely abundant source of food, concentrated in a very small area, and available only part of the year. The team found that population density remained similar—about 13 cats per 100 square kilometers—whether penguins were present or absent. Therefore, the penguins did not create more handles, but reorganized how these cats share space.
It turns out that pumas that eat penguins behave quite differently from those that prefer other diets in Patagonia. The study found that bird-eating big cats shared the same area much more often than non-bird-eaters and were not attacking each other as often as expected. “In other words, the pumas that eat the penguins were quite tolerant of each other’s presence,” says Donadio, who is also a National Geographic Explorer.
Such tolerance was surprising, given the solitary stereotype of pumas. In Patagonia, these big cats are in the open, as they are the best predators. “Unlike in Africa, they don’t need to huddle together to take down prey two or three times their size. And unlike in North America, there are no grizzly bears, black bears or wolves, so these cats aren’t prowling the trees at night like they are above,” says Jim Williams, who worked for decades as a biologist with Montana Fish and Sea wrote about the relationship between Montana Fish and wildlife. in his book Puma Path.
In Monte León, pumas often visit the penguin colony in the evening to hunt. Gonzalo Ignazi
To some extent, it makes sense that pumas latched onto the new food source, since 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. “This is not shocking from an ecological point of view or a natural behavior, but it is for people who do not know that penguins and pumas overlap,” he adds.
But the changes in behavior are surprising. “We tend to think of pumas as extremely aggressive and intolerant,” says Donadio. “But when food is abundant and concentrated, there is no need to defend it. They become more socially tolerant,” he adds.
(What one photographer learned after spending almost a year with pumas)
Open questions
Donadio says that, so far, surveys suggest that the penguin colony has remained stable or even increased since the park was created. What remains uncertain is how penguin-driven changes in puma behavior will drive the rest of the ecosystem—especially for guanacos, Patagonia’s dominant herbivore, and pumas’ primary traditional prey.
Despite the behavioral changes documented in the study, some important questions remain. Researchers still don’t know how many individual pumas penguins kill, making it difficult to assess the long-term impact of predation on the 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 long-term feature of the ecosystem.
Also, researchers have yet 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 the pumas get their food, but the next step is to understand the ecological implications of that change,” says Serota.
For now, the findings of puma behavior show that when nature is given space, it doesn’t always look back—it improvises. “Restoration does not mean going back to some historical picture,” says Serota. “Species are returning to ecosystems that have changed dramatically. This can create completely new interactions.”
The non-profit National Geographic Society, committed to illuminating and protecting the wonder of our world, funded the work of Explorer Emiliano Donadio. Learn more about the Society’s support for Explorers.