During the 20th century, pumas, along with foxes and large herbivores, disappeared from Argentine Patagonia to make way for sheep farming after European colonization. Their absence has allowed Magellanic penguin colonies, previously confined to islands off the Atlantic coast, to expand across the continent. Today, this scenario has changed and the mountain lions have returned after an attempt to restore the wildlife of the past. Their return to a transformed ecosystem, with large numbers of penguins, modifies their behavior and has led to unprecedented population densities for the species.
An international team of scientists documented this discovery in the Monte León National Park (MLNP), in southern Argentina, more precisely in the province of Santa Cruz. According to ecologist Mitchell Serota of the University of California, Berkeley, who led the research, the study highlights the effects of conservation on transformed ecosystems. “Wildlife is recolonizing ecosystems that have changed dramatically since these species disappeared,” says Serota.
Magellanic penguins form huge colonies and spend more than half the year on land. They are abundant, predictable and defenseless against a big cat. Unlike other prey, these birds are not adapted to terrestrial predation. “Two key factors for pumas come together here: penguins are numerous and easy to capture,” summarizes Serota.
The study – based on GPS collars, camera traps and advanced population models – shows that when penguins are present, pumas reduce their movements and concentrate their activity around the colony. They stay longer in one place and return again and again to the coastal area. “If you have ever visited a penguin colony, you understand straight away. It’s a small strip of beach where everything is concentrated,” explains the ecologist.
Less lonely cougars
The puma is known to be a solitary and territorial hunter. However, the level of social interaction witnessed by these Argentine, American and German scientists is surprisingly high. “This is the highest density of pumas recorded so far,” underlines Serota. More than double the maximum values observed elsewhere in South America.
Adult females, who normally avoid their peers, tolerate each other in the same space. Additionally, interactions between pumas were thought to be primarily limited to reproductive behavior. However, the study indicates that we cannot exclude the possibility that there is a genetic relationship between these animals, which could promote greater social tolerance between them.
Penguins play a key role in puma population density, but they alone do not explain this phenomenon. “We think they are an important driver, but we must take into account that penguins are a seasonal resource, they are present a little more than half the year,” specifies the author. When birds migrate to the sea, pumas, the region’s only large carnivore, must turn to other prey, such as guanacos, a Patagonian wild animal that resembles a llama. “There is a large population of guanacos. This helps the pumas when the penguins are gone,” says the expert, adding that the combination of resources is what allows predator densities to be maintained so high.
Regular hunting of seabirds by large land carnivores is unusual, but there is precedent. The researcher compares the phenomenon to the relationship between bears and salmon. “Bears congregate in rivers during salmon migrations, and something very similar happens here with mountain lions and penguins: They create a hotspot that reorganizes their behavior across the landscape.” There are also records of Tasmanian devils hunting penguins, as well as other recent studies of lions and jaguars feeding on marine resources.
The creation of the Monte León National Park dates back to 2004, but the research was carried out from 2019 to 2023. “Many people asked us if this represented a threat to the penguins,” admits the researcher. However, he says data indicates the penguin population in the area appears stable and even growing since the park’s creation.
Predators are often the subject of restoration projects because of their ability to regulate other species, but changes in landscape, climate, and prey availability alter how, when, and where they obtain food. “Restoring wildlife does not mean returning ecosystems to the past. It can generate completely new interactions that change behavior and populations in unexpected ways,” says Serota.
The researcher says that now that we know how the new prey has changed the pumas’ behavior, it remains to understand in what other aspects this translates. “The next step is to find out what these changes mean for the rest of the ecosystem,” says Serota, particularly for guanacos, Patagonia’s main large herbivore. “The relationship between pumas and guanacos is central to the region, and any changes in how pumas move and hunt can have repercussions.”
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