An entire species in a stream you can walk in a day

You can cross the whole world of the Valcheta Frog in an afternoon. Pleurodema somuncurense is smaller than a matchbox and lives only in the thermal headwaters of the Valcheta Stream, on the Somuncura Plateau in Río Negro, Argentina (Figures 1 and 2). Its entire global range covers less than 10 square kilometers. There is no second population in a neighboring valley, no backup catchment, no insurance elsewhere on the plateau. Whatever happens in those few kilometers of warm water happens to the species.

A shallow stream running through a broad valley on the Somuncura Plateau, with low rocky hills and tussock grass along both banks under a clear blue sky
Figure 2. The Somuncura Plateau, Río Negro, Argentina. Thermal springs are the only reliable water across much of this landscape, which is why both frogs and livestock concentrate at them. Photo: Federico Kacoliris

We arrived in 2013 to protect the frog, and nothing else. We found that the frog could not be protected on its own terms. The pressures driving it toward extinction were greater than the species itself, and unless we took them on, nothing we did for the frog would hold. So, the project grew, until it covered the whole biodiversity of the area, and we decided to establish our own NGO, Fundación Somuncura, to strengthen and scale up our work there. Thirteen years later, the frog is still one of the smaller things we are responsible for, and one of the bigger reasons for all the rest.

What we found

Rainbow trout (Oncorhynchus mykiss) were introduced into the Valcheta Stream almost a century ago. They did what introduced salmonids do in a system with no evolutionary history of them: they became the apex predator. Over decades, the frogs were pushed out of the main stream and into the hot springs at the headwaters, pockets of warm water where trout could not follow because of the existence of waterfalls (1).

But the springs came with their own problems. On a dry plateau, they are the only reliable water, which means livestock go to them, and cattle and sheep trample spring margins into mud. Some springs had been tapped. Others sat inside grazing paddocks with no fence, and no reason for one to exist.

Every one of these pressures landed on the frog, and not one of them was aimed at it. Nobody stocked trout to harm an amphibian, and nobody waters cattle at a spring with a Critically Endangered species in mind. The frog was disappearing because the valley it lived in had been quietly rearranged around it over the course of a century, by fish stocked for sport, by animals kept for wool and meat, by an economy with no relationship to the stream except as a resource. That is not a problem a captive-breeding facility solves, and not one you can solve by working on the frog alone.

The frog as a lever

Here is what we did not expect. In a region where almost nothing about the landscape is legible to a funder or a ministry, the frog was legible.

Nobody funds “a degraded stretch of Patagonian steppe.” It has no status, no listing, no photograph that makes anyone stop scrolling. But a Critically Endangered amphibian with a global range under 10 square kilometers is a fact that travels. It sits on the IUCN Red List. It can be named in a provincial decree. It fits in a press release. It gives a donor something to point at, a government something to legislate for, and a rancher something specific to remember about their own property. Whether a tiny frog can ever compete with a panda or an eagle in the charisma stakes is a discussion for another article.

So, we began using the frog deliberately, not only as the object of the work, but also as the door into it. Everything this project has since become; it became because a frog got us through that door.

What the ambassador moved

Springs. All known spring systems within the frog’s range are now protected and fenced against livestock. The last of them, El Ariete, was completed in 2026. Eight of eight sounds tidy; it took the better part of a decade of separate negotiations with separate landowners (Figure 3).

A wire fence and a white gate enclosing a green spring system on a rocky hillside, with an interpretive sign mounted on the fence
Figure 3. A fenced spring system. All eight springs within the frog’s range are now protected from livestock trampling; El Ariete, the last of them, was completed in 2026. Photo: Federico Kacoliris

The stream itself. Five kilometers of the Valcheta Stream are now confirmed free of introduced trout. Getting there took years of trial and error. Our early barriers failed as early barriers do, and each failure sent us back to the drawing board; the designs holding the line today were developed with hydraulic engineers, and they work. Behind each barrier came the slower, less visible half of the job: removing trout reach by reach, and going back again, and again, until the water was empty of them and stayed empty. Environmental DNA sampling is now our verification method.

Land. Twenty-seven thousand hectares of the plateau are now under conservation protection, roughly 35% of the frog’s watershed, including two properties purchased outright. Those hectares contain a great deal that is not a frog: guanaco, puma, endemic plants, and the headwaters of streams we have barely begun to survey.

People. This is the part we would most want other practitioners to take away. On plateau ranches, pumas and foxes take lambs, and ranchers shoot them. We introduced livestock guardian dogs, raised from puppyhood among the flock, on properties inside the frog’s watershed. Through 2025, no predators were killed on any property in the program. Two more dogs, Blas and Vicente, went to their ranches this August.

Those dogs do not protect frogs, not directly. But follow the chain. Predation losses are the main reason ranchers here consider replacing sheep with cattle, which pumas and foxes rarely touch. Cattle are also far heavier on a thermal spring: they wade in, break down the margins, and reduce a spring system to mud in a fraction of the time sheep take. A dog that keeps lambs alive removes the reason to switch. So, the dogs defend production, they end the shooting of predators, and they hold the plateau’s historic sheep management in place, and it is that last, least obvious link that protects the frogs (Figure 4).

A white livestock guardian dog sitting on bare ground in front of a flock of sheep inside a corral at sunset, with a stone building behind
Figure 4. Livestock guardian dog raised among the flock, before being transferred to ranches within the frog’s watershed. No predators were killed on program properties during 2025. By reducing lamb losses, the dogs also remove the incentive to replace sheep with cattle, a shift that would be far more damaging to the thermal springs. Photo: Rodrigo Calvo

We did not design that chain; we found it, several years in, by asking ranchers what would actually change their minds. The frog opened the conversation. What came through the door was a working relationship with the people who own the land the frog depends on, and an answer none of us would have reached from the frog alone.

An economy. In July 2026, Fundación Somuncura signed a formal agreement with the Río Negro Secretariat of the Environment covering visitor management on the plateau. The work underneath that agreement is a series of workshops with plateau residents, aimed less at recruiting guides than at helping people start or strengthen whatever ecotourism activity suits their own situation. Some of them want to be local guides; others are building services for the visitors who come. The number of visitors at our two monitored access points is increasing, and we have developed facilities such as camping areas, rustic trails, and interpretive signage for them. Our goal is that local families could earn a significant part of their living from a frog most of the province has never heard of.

Other flagships. The stream is not only the frogs. It is also the entire world range of three Critically Endangered species: the naked characin (Gymnocharacinus bergii), the only endemic fish in the Patagonia steppe, and of two freshwater snails of the genus Potamolithus found nowhere else. They face the same trout and the same trampled springs. Every meter of stream cleared and every spring fenced counts for all of them at once.

The traffic runs both ways. Those species have their own projects and their own funding, which in turn protect habitat the frog needs. A stream with four flagships is harder to overlook than a stream with one, and each project makes the next easier to justify.

And the frog. Population monitoring indicates reestablishment of extinct local populations and an increase of roughly 20% of the entire metapopulation across the range (2, 3), with further analyses in press. Twenty percent may not sound like a great deal. For a Critically Endangered species with nowhere else to go, it is: the difference between a population that can absorb a bad season and one that cannot. If the trend holds, the Valcheta Frog could qualify for downlisting from Critically Endangered to Endangered or even lower categories within a few years, an outcome that seemed out of reach when we started.

What it cost us

We would be doing readers a disservice if we made this sound tidy.

The social work took far longer than the ecological work, and we budgeted it the other way around. Removing trout from a reach of a stream is a logistical problem with a known solution, but implementing it is far from easy. Persuading a fourth-generation rancher that a dog will do a better job than a rifle is a matter of years, of showing up in the same kitchen repeatedly, and of the first dog not failing.

Administration is its own ecosystem. Our eDNA samples sat for over a month waiting on export permits, a delay entirely outside our control that pushed verification past a funder’s reporting window. Build that into your timeline, because it will happen to you.

And the ambassador framing carries a real cost, which we are still managing. When a single species becomes the currency of a program, everything has to be justified in that currency. There is a great deal on the Somuncura Plateau that matters and has no Red List entry to trade on: springs outside the frog’s range, grassland the fences do not reach, plants nobody has assessed. A flagship gets you through the door; it can also become the only room you are allowed into. Now that the door is open, we are working to widen the case.

Late November

At the end of November 2026, we will reintroduce Valcheta Frogs into El Ariete, the eighth spring, which is fenced and has vegetation recovering along its margins. It is also where the species was first found. Some of the specimens Dr. José M. Cei used to describe Pleurodema somuncurense in 1969 came from this spring, and the frogs that produced them are gone: the population went locally extinct sometime after the species it defined was named. Returning animals to El Ariete completes the range on paper, eight springs of eight. It also returns a species to its type locality, which is harder to include in a funder’s report than a percentage, and which we suspect will matter more in the long run.

If it holds, we will have a species present across every spring system in its historic known range, in a stream five kilometers cleaner than we found it, inside a 27,000-hectare conservation landscape, on ranches where nobody has shot a puma in over a year, watched over by guides who grew up nearby.

That is a great deal to ask of an animal you can hold in a closed hand. But it is what happened, and we do not think it was an accident. If you work on a microendemic species, one of those animals whose entire existence fits inside a single valley, you may be holding more leverage than you realize. The smallness is not the obstacle. It is the argument.

Acknowledgments

This work has been supported by the Whitley Fund for Nature, the Indianapolis Zoo, the People’s Trust for Endangered Species, the World Land Trust, USFWS, NatGeo, Rufford Foundation and Amphibian Ark. We also thank Secretaría de Ambiente y Cambio Climático de Río Negro for its partnership on visitor management, the Ecoparque de Buenos Aires for collaborating with ex situ management and ASA and ASG for advice. Finally, we would like to thank the ranching families of the Somuncura Plateau, among them Lorenzo Alan, Diego Pérez, the Ortiz family and Ariel Calvo, without whom none of the fish barriers, the fences, the dogs or the frogs would be where they are.

References

  1. Velasco MA, Berkunsky I, Simoy MV, Quiroga S, Bucciarelli G, Kats L, Kacoliris FP. 2017. The rainbow trout is affecting the occupancy of native amphibians in Patagonia. Hydrobiologia, 817(1), 447–455. https://doi.org/10.1007/s10750-017-3450-6
  2. Velasco MA, Berkunsky I, Akmentins MS, Kass C, Arellano ML, Aguirre T, Williams JD, Kacoliris FP. 2019. Status and population dynamics of the Critically Endangered Valcheta frog Pleurodema somuncurense on the Patagonian Somuncura Plateau. Endangered Species Research, 40: 163–169.
  3. Calvo R, Rolón MCJ, Tettamanti G, Fortunato D, Vera D, De los Santos F, Kacoliris FP, Berkunsky I, Jones J, Quiroga S, Di Pietro DO, Velasco MA. In press. Effectiveness of reintroduction and habitat management actions on the Valcheta Frog (Pleurodema somuncurense) in the Valcheta Stream, Northern Patagonia, Argentina. Aquatic Conservation: Marine and Freshwater Ecosystems.