For decades, cougars have preyed on sheep on Argentina’s coastal ranches, and ranchers have hunted them in large numbers. Mountain lions disappeared from the landscape. Then, in 2004, conservationists established Monteleone National Park in the area. Sure enough, after the hunting stopped, the big cats returned. When they return, they discover a new player among their old neighbors: Magellanic penguins.
What scientists didn’t anticipate was that cougars would not only prey on penguins, but that the seasonal arrival of birds would recalibrate how these famously solitary cats move, interact and hunt on land. A new study published today in the journal Proceedings of the Royal Society B This shift in mountain lion behavior is documented for the first time and challenges our assumptions about what happens when large predators return to ecosystems.
“When we start rewilding the land, returning species may find a slightly different system than the one they inhabited 100 years ago, and they adapt to it,” said Emiliano Donadio, scientific director of Argentina’s Rewilding Foundation and co-author of the study.
(How a penguin ‘massacre’ led to historic new protections in Argentina)
Camera traps reveal cougar hunting behavior
The researchers did not initially set out to study this unique predator-prey relationship. Lead author, ecologist Mitchell Serota, then at the University of California, Berkeley, was working with the Argentinian Wildlife Foundation to study how wildlife responds when human pressure is removed from former rangelands. “I traveled to Patagonia to look extensively at the recovery results. Penguins were not the initial focus at all,” he said.
In 2023, Serota and his colleagues reported that big cats actually feed on these lumbering birds. “This interaction is well known, but we believe it is minor,” he said. “Maybe just a few people.”
The team installed 32 camera traps throughout the park and tracked 14 adult cougars (cougar) wore a GPS collar between September 2019 and January 2023. Combining this data with field observations, the researchers quickly realized that cougars were eating penguin snacks much more frequently than expected.
“We repeatedly detected cougars around penguin colonies,” Serota recalled. “It’s been clear to us since then that this is not a side note. It determines how these animals use the land.”
A new food web is forming
Because Magellanic Penguins (Spheniscus magellanicus Spending most of their lives at sea, they are unusual prey for large terrestrial carnivores and their diet consists mainly of land mammals such as deer, guanacos (a close relative of the camel) and hares. But during the breeding season (from about September to April), seabirds gather on land in large numbers. In Monteleone, more than 40,000 breeding pairs nest along about two kilometers of coastline.
(What Magellanic Penguins Teach Us About Survival)
For mountain lions, whose territories can span hundreds of square kilometers, this creates a strange situation: an extremely rich food source, concentrated in a small area, and only available part of the year. The team found that whether penguins were present or not, population density remained similar – about 13 cats per 100 square kilometres. So instead of creating more cougars, penguins are reorganizing the way these cats share space.
It turns out that pumas that feed on penguins behave very differently than those in Patagonia that prefer other diets. The study found that bird-eating big cats shared the same areas more frequently than non-bird-eating big cats and did not attack each other as often as one would expect. “In other words, cougars that feed on penguins are quite tolerant of each other’s presence,” said Donadio, who is also a National Geographic explorer.
This tolerance is surprising considering the stereotype of cougars as loners. In Patagonia, these big cats are out in the open as they are apex predators. “Unlike in Africa, they don’t need to congregate to hunt prey that’s twice or three times their size. And unlike in North America, there are no grizzly bears, black bears or wolves, so these cats aren’t slinking around in the trees at night like they are here,” Jim Williams said. Cougar Trail.
In Monteleone, cougars often come to penguin colonies to hunt at night. Gonzalo Ignazi
To some extent, it makes sense that cougars would pounce on new food sources because penguins are low-risk prey. “Big cats — lions, panthers, cougars, cougars — always prey on the richest and most vulnerable food sources,” said Williams, who was not involved in the current study. “It’s not shocking from an ecological perspective or natural behavior, but for people who don’t know that penguins and cougars overlap,” he added.
But the behavioral changes were surprising. “We tend to think of mountain lions as being very aggressive and intolerant,” Donadio said. “But when food is plentiful and concentrated, there’s no need to defend it. They become more socially tolerant,” he added.
(What one photographer learned after nearly a year living with a cougar)
open questions
Donadio said surveys so far show penguin colonies have remained stable or even increased since the park was created. What remains uncertain is how the penguin-driven changes in puma behavior rippled through other parts of the ecosystem, particularly guanacos (Patagonia’s main herbivore and the puma’s main traditional prey).
Despite the behavioral changes documented in the study, some important questions remain. Researchers still don’t know how many penguins the cougars killed, making it difficult to assess the long-term effects of predation on the colony, although Monteleone’s penguin population appears to be stable or increasing so far. They also can’t determine whether high mountain lion densities are a temporary or long-term feature of the ecosystem.
Additionally, researchers still need to figure out the broader ecological consequences of penguin-driven changes in cougar behavior. “We know that penguin colonies have changed where, when and how cougars access food, but the next step is to understand the ecological impacts of this change,” Serota said.
So far, behavioral findings in cougars suggest that when nature is given space, it doesn’t always look back but improvises. “Recovery doesn’t mean going back to some historical snapshot,” Serota said. “Species are returning to ecosystems that have undergone dramatic changes. This can create entirely new interactions.”
The nonprofit National Geographic Society, dedicated to illuminating and protecting the wonders of the world, funded the work of explorer Emiliano Donadio. Learn more about the Society’s support for explorers.
