Scientists in Costa Rica have identified a new species of tree frog measuring less than four centimeters long that lives near streams and coffee farms in the central Pacific region.
The newly described amphibian, named Isthmohyla nacientes, is endemic to the Central American nation, meaning it is found nowhere else on Earth. Researchers warned that the sensitive stream and agricultural habitats where the frog survives face growing threats from agricultural chemical runoff and habitat degradation.
The scientific description of the species was published in July 2026 in the peer-reviewed journal Ichthyology & Herpetology. The discovery was led by a team of biologists from the University of Costa Rica, the National University of Costa Rica, and the National Scientific and Technical Research Council of Argentina.
Scientific identification and historical observations
Specimens of the frog were first collected and observed in the field as early as the 1960s. However, for decades scientists classified the population as belonging to a previously known species within the same genus.
Researchers confirmed that the frog was an entirely distinct species by combining genetic testing, evaluating physical morphological features, and analyzing acoustic sound recordings of both adult frogs and larval tadpoles.
The research team included Argentine biologist Julián Faivovich of the National Scientific and Technical Research Council and the Bernardino Rivadavia Argentine Museum of Natural Sciences in Buenos Aires. Costa Rican scientists Wagner Chaves-Acuña, Jonathan Navarro-Picado, and Marilyn Ureña-Chaves also co-authored the study.
The University of Costa Rica and the National University of Costa Rica are leading public research institutions in Central America, while the Bernardino Rivadavia Museum in Argentina is one of South America's oldest natural history institutions.
Physical characteristics and underwater vocalizations
The frog is smaller than four centimeters in length and features a greenish body covered with irregular dark spots across its back. Its upper and lower limbs display distinct yellowish-orange color tones, while adult males possess a translucent throat sac that visibly inflates when calling.
Field researchers documented several unique vocalizations produced by the species, including a specialized courtship call performed underwater. Submerged mating calls are considered an unusual acoustic behavior among tree frogs, which typically call from elevated vegetation.
Known commonly as the spring frog, or rana de las nacientes, the species derives its name from its reliance on headwater streams and small creeks situated between 1,400 and 2,000 meters above sea level. These high-altitude aquatic ecosystems represent fragile environments that are highly vulnerable to human modification.
The species also maintains a close ecological relationship with highland coffee plantations in the central Pacific mountains. The nocturnal frogs are frequently observed resting on coffee bushes during the night when their activity peaks.
Although the frogs inhabit agricultural areas, they do not feed on coffee crops or leaves. Instead, the amphibians prey on small insects while using the dense foliage of the plantation bushes for shade and essential moisture retention.
Threats from agricultural pesticides and habitat degradation
The close proximity of the frogs to agricultural land exposes their fragile water sources to chemical contamination. Wagner Chaves-Acuña stated that agricultural chemicals travel through the air, soak into the soil, and wash directly into the stream networks where tadpoles develop.
Pesticide exposure during larval development can alter amphibian growth rates, weaken immune responses, and cause mortality in sensitive freshwater species.
Jonathan Navarro-Picado, a researcher at the International Institute for Wildlife Conservation and Management at the National University of Costa Rica, identified the removal of natural riverbank vegetation as another severe threat. He explained that clearing native grasses and shrubs along stream buffer zones destroys essential shelter and potential breeding sites.
Conservation concerns have intensified following field observations conducted during the monitoring project. Marilyn Ureña-Chaves noted that while the frogs were relatively common across several streams when initial surveys began, field workers detected the animals with progressively decreasing frequency over time.
