A female individual of Alsodes vittatus (Credit: Edvin Riveros)

CONCEPCIÓN, Chile — For 130 years, a small Chilean frog vanished from scientific view. Biologists searched. Nature enthusiasts kept their eyes open. But Alsodes vittatus remained stubbornly invisible, known only from a single preserved specimen and the yellowed pages of a century-old scientific description.

That changed when a team of determined researchers from Chilean universities finally located not one but three populations of this mythical amphibian hiding in remote Andean streams. Their March 2025 paper in the journal ZooKeys documents what might be the most exciting amphibian rediscovery in South America this decade.

Historical Mystery: The Vanishing Frog

The story begins with Rudolph Amandus Philippi, a German-born naturalist who described dozens of Chilean amphibian species in 1902. Many of his classifications were later questioned or rejected outright by other scientists, who felt Philippi split species unnecessarily based on small differences. But the case of Alsodes vittatus stood apart, mainly because the species had one distinctive feature—a yellowish stripe running the length of its back, from snout to rear end.

After Philippi’s description, the frog vanished. Despite targeted searches between 1995 and 2002, nobody could find it again. The frog became a ghost, possibly extinct, or perhaps never a valid species at all.

Finding the lost frog required detective work as much as biology. The research team dug through historical documents, focusing on the journey of entomologist Philibert Germain, who collected the original specimens in December 1893 while traveling through an enormous estate called Hacienda San Ignacio de Pemehue.

Using Germain’s own travel accounts published in 1894, the team mapped his likely route through the mountainous terrain of what is now the border between Chile’s Biobío and La Araucanía regions. This historical sleuthing pointed them toward small streams in specific valleys of the Andean foothills.

From Maps to Mountain Streams

Between 2015 and 2024, the researchers conducted field expeditions, primarily working at night when the frogs would be active. Their persistence paid off: they discovered five previously unknown populations of Alsodes frogs. Two were identified as the related species Alsodes igneus, but three others proved to be the long-lost A. vittatus.

These surviving populations inhabited small mountain streams at elevations between 1,421 and 1,610 meters, nestled among temperate forests mixed with distinctive monkey puzzle trees. The cold, rocky waterways had somehow sheltered the species through decades of habitat changes in the surrounding lowlands.

When they examined the rediscovered frogs, the researchers noticed something unexpected: the yellowish stripe that had been considered the species’ calling card wasn’t present on all individuals. Some frogs displayed it prominently, while others lacked it entirely. This variation within the species had never been documented before and explains why earlier researchers might have missed populations during their searches.

DNA analysis brought another surprise. The Alsodes vittatus populations were closely related to Alsodes neuquensis, a species previously known only from Argentina. One A. vittatus specimen was genetically closer to A. neuquensis than to other A. vittatus from the same location. This suggests the two species might actually be one, with a range spanning both sides of the Andes.

Conservation Challenges and Future Threats

The rediscovery allowed researchers to reassess the conservation status of Alsodes vittatus. Previously listed as Critically Endangered in Chile, they now suggest downgrading it to Endangered. While better than extinction, the species still faces serious threats: its known habitat covers roughly 8 square kilometers, and the researchers documented problems including forest fragmentation, livestock activity, introduced trout that may prey on tadpoles, forest fires, invasive algae, and climate change.

During night surveys, the team saw remarkable diversity in the frogs’ colors. Adult males ranged from light brown with yellow and green tints to olive brown, while some juveniles showed darker brown coloration. This variation appeared both within and between populations.

One discovery particularly excited the team: they found smaller frogs with dark brown coloration and a stripe that closely matched Philippi’s original 1902 illustration. These juveniles were also approximately the same size (41mm) as mentioned in Philippi’s description, suggesting he based his classification on immature specimens rather than adults—solving another piece of the century-old puzzle.

“The rediscovery of A. vittatus, after 130 years since the collection of the type specimens, demonstrates that Philippi’s taxonomic legacy has not yet been fully dimensioned,” write the researchers, led by Dr. Claudio Correa from the Universidad de Concepción.

Beyond One Species: Broader Implications

The research carries weight beyond this single species. It vindicates aspects of Philippi’s work, once dismissed by later taxonomists. It shows that some “extinct” species may persist undetected even when scientists actively search for them. And it highlights major knowledge gaps about amphibians in the Chilean Andes, suggesting other undiscovered species may await detection.

For conservationists, the find offers both hope and urgency. With specific habitat information, protection efforts can now target critical areas. But the frogs’ extremely limited range and ongoing habitat degradation mean immediate action is needed to prevent their second disappearance—this time for good.

“Findings like these demonstrate that a greater exploration effort, guided by rigorous historical research, is required to continue revealing the diversity and distribution patterns of Chile’s amphibians,” the authors write.

While environmental headlines often read like obituaries, Alsodes vittatus offers a rare second chance. These frogs survived 130 years without human intervention, but their next century looks considerably more precarious. With just 8 square kilometers of known habitat and a changing climate hanging in the balance, so does the future of this fascinating frog.