Pristimantis ruidus: Frog Species Missing for 100 Years Rediscovered in Ecuador

During a 2022 expedition to the Molleturo forest in the Ecuadorian Andes, biologist Juan Sánchez-Nivicela and his team made a remarkable discovery: two tiny frogs that could not be immediately identified. Now, as the researchers report in the journal Zoosystematics and Evolution, the frogs belong to the species Pristimantis ruidus, a rain frog species that had been considered lost for a century.

The International Union for Conservation of Nature (IUCN) had listed Pristimantis ruidus as “possibly extinct,” as no further sightings of the species had been recorded in the wild since its discovery in 1922 by American zoologist George Tate. One of the major threats to the species is the massive deforestation at its only known location, where large areas of forest have been converted into grazing land.

The original description of Pristimantis ruidus was published in 1979 by American herpetologist John D. Lynch, based on preserved specimens collected by Tate nearly 50 years earlier. Despite extensive searches in southern Ecuador in the 1970s, Lynch was unable to locate any additional specimens.

In their laboratory at Universidad San Francisco in Quito, Sánchez-Nivicela and his team compared the frogs they discovered in 2022 with Lynch’s descriptions. The frogs matched perfectly: rough skin, numerous bumps, and distinctive W-shaped ridges on their backs. The lack of prominent tympana (eardrums), as seen in other frogs, further confirmed the identification.

To definitively verify the rediscovery, the researchers analyzed the DNA of the two female frogs and compared it with genetic data from 35 other Pristimantis species stored in a gene bank. The genetic code matched no other species, conclusively confirming the rediscovery of the rain frog Pristimantis ruidus, which had been missing for nearly 100 years.

Amphibians in Ecuador: Rediscoveries strengthen conservation efforts

“This discovery fills us with hope,” says biologist María del Carmen Vizcaíno, director of the Alianza Jambato, in an interview with National Geographic. The coalition of over 26 institutions is dedicated to the conservation of Ecuador’s amphibians. Vizcaíno believes the rediscovery of Pristimantis ruidus could become a powerful symbol in the fight to protect the southern Andes – the country’s most endangered ecosystem, threatened by mining and illegal logging.

In Ecuador, herpetologists and conservationists are using rediscoveries of lost amphibian species to highlight the growing threats to the nation’s biodiversity. Notable examples include the long-nosed stubfoot toad (Atelopus longirostris), rediscovered in 2015 after 30 years, and the Jambato harlequin frog (Atelopus ignescens), found again after 28 years. These species have become symbols of resistance in the battle against mining in the Intag Valley. In 2024, scientists and activists won a legal case against two major mining companies, resulting in a court decision that revoked the Llurimagua mining project’s license.

Despite this legal victory, the situation remains dire. The forests of the western Andes, including the Molleturo Forest, have lost around 70 percent of their original area to deforestation and mining over the past two decades. Juan Sánchez-Nivicela, lead author of the study on the rediscovery of Pristimantis ruidus, believes that each newly discovered species strengthens the case for protecting these endangered regions. The discovery of this rain frog marks a significant step in conservation, offering hope that other lost species might also resurface. New discoveries also play a key role: in 2023, Sánchez-Nivicela and his team identified a new frog species in southeastern Ecuador – the Tolkien frog (Hyloscirtus tolkieni).