Scientists at the Pontificia Universidad Católica del Ecuador have formally described Pristimantis milpe, a common and widespread frog that spent more than a century being mistaken for another species. The mystery was resolved by studying specimens collected in Ecuador during the 19th century and preserved at the Natural History Museum in London.
The finding stands out because many newly described species are rare or confined to small areas. Pristimantis milpe, by contrast, is widespread, relatively easy to find, and readily detected by its nighttime call. Its known range covers more than 67,000 square kilometers across the Chocó forests of western Ecuador and southern Colombia, from sea level to elevations of 1,200 meters.
The formal description appears in the international journal ZooKeys, which focuses on biodiversity and taxonomy.
A Century-Old Case of Mistaken Identity
Researchers were able to identify Pristimantis milpe by revisiting historical amphibian specimens housed at the Natural History Museum in London (NHM).
Santiago Ron, a researcher at PUCE and lead author of the study, traveled to England to investigate a classification problem that had persisted for more than 100 years. He examined the original specimens – known as “types” – that had been collected in Ecuador during the 19th century and preserved in the museum ever since.
By comparing those historical frogs with living populations from the Ecuadorian Chocó, the team found that the old specimens had been incorrectly linked to a different species. As a result, a frog that had been regularly seen and documented for decades never received a scientific name of its own.
“That such a common species has gone unnoticed under the wrong name for decades highlights the importance of correctly connecting scientific names with living populations in nature,” notes Jhael Ortega, a PhD student at Virginia Tech and one of the study authors.
The Clicking Frog of the Chocó Forest
The Milpe Robber Frog (Cutín de Milpe) is active at night. Males typically call from leaves on shrubs and bromeliads several meters above the forest floor. Their calls are loud and distinctive, producing a sound similar to a “click.”
Females and males also differ noticeably in appearance. Females have striking coloration around the groin and thighs, where orange or light blue tones can appear alongside black spots. Males generally have more uniform coloring.
The frog lives in the forests of the Ecuadorian Chocó and southern Colombia, a region considered especially important for biodiversity conservation.
Why Historic Museum Collections Still Matter
The discovery highlights the continuing scientific importance of natural history collections. Specimens preserved for decades or even centuries can give researchers a way to revisit old classifications, compare physical traits, and resolve questions that earlier scientists could not answer.
In this case, combining 19th-century museum specimens with observations of living frog populations allowed researchers to determine that Pristimantis milpe deserved recognition as a distinct species.
The findings also underscore how much remains to be learned about biodiversity. Even common, widespread animals can conceal surprises, and solving those mysteries often depends on bringing historical collections together with modern research and observations.
