New frog species discovered in Tapir Valley Nature Reserve, Bijagua, Costa Rica

Donald Varela Soto grew up surrounded by the sounds of the rainforest. From a young age, he learned to pick out specific animals within the chorus.

“As country boys, we know sounds,” says Soto, a Costa Rican naturalist and farmer. So when Soto heard an unusual frog call one day while exploring a local forest, he knew it could be something special.

Soto found the frog just in time. For nearly two decades, Soto and local collaborators have been transforming a 220-acre section of land in northern Costa Rica into a wildlife paradise called Tapir Valley Nature Reserve. Soto, his family, and people from the nearby town of Bijagua have transformed the land by hand from a clear-cut cattle ranch to a forest teeming with trilling birds, hooting primates, and lumbering tapirs.

Soto was planning to expand part of the reserve’s wetland to create more habitat for migratory birds, but unusually heavy rain halted construction days before they were planning to break ground. When he was walking around the flooded area soon after, Soto heard an unfamiliar and intriguing frog call.

“It was calling very differently than anything else that I had seen or heard at our reserve,” says Soto. “I listened to this little frog but it was almost impossible to find it, it was so well camouflaged.” After searching through the foliage, he finally spotted it: a tiny green amphibian perched on a leaf.

Eager to find out what the mystery frog could be, Soto compared the frog to those in his local field guides, but no species matched. iNaturalist, a species identification site, didn’t provide any matches either. He snapped a few pictures of the male frog and shared them with colleagues, who suspected the frog was a juvenile of a common species called Boana rufitela. But Soto wasn’t so sure, noting that the frog lacked rufitela’s characteristic yellow line down its flanks.

“None of the ones that I had seen have that continuous line all the way to the back of the frog, so it had to be something different,” says Soto.

Still not convinced, Soto returned to the wetland, recorded a video of the frog and shared it with Esteban Brenes-Mora, director of Costa Rica Wildlife Foundation and Re:wild’s senior Mesoamerica associate. Brenes-Mora then contacted Andrew Whitworth, director of Osa Conservation, inviting him to visit the nature reserve. The herpetologist was immediately intrigued, and after visiting the Tapir Valley Nature Reserve to try and locate the mystery frog in person he connected Soto with herpetologists Twan Leenders and Juan Gabriel Abarca.

“It's super hard to find,” says Esteban Brenes-Mora, director of Costa Rica Wildlife Foundation and Re:wild’s senior Mesoamerica associate. “Personally, it took me almost two years to find my first specimen.”

Once Soto, Abarca and Leenders located a handful of individuals, they began comparing the amphibian to other species in the area, including its call, physical characteristics, and genetics. Their thorough analysis revealed what Soto had suspected: the frog was a new species. The team named the species Tlalocohyla celeste due to the light blue coloration in the axillary membranes and male vocal sac. It was given in tribute to the famous turquoise waterfall, Río Celeste, a tourism icon for the community.

Based on scientists’ survey of the area, the species seems to be isolated to a single wetland in the Tapir Valley Reserve. “As far as we know, it's restricted to this 20-acre (8-hectare) wetland in Tapir Valley,” says Valeria Aspinall, a biologist involved in the discovery.

Next, she says they want to expand search efforts in similar habitat and explore the specific conditions around the wetland to unravel why the frog seems to prefer this habitat.

The research team is now working to get Tlalocohyla Celeste recognized by the International Union for Conservation of Nature.

“It's a critically endangered species that needs conservation action right now,” says Brenes-Mora. “Otherwise, we are going to describe it and then lose it in a couple of years. That's my major concern. We don’t want to make noise about the discovery of a new species and then make noise about its disappearance/extinction.”

Brenes-Mora notes that this recent discovery would never have been possible without an interdisciplinary approach and shared knowledge from members of the local community. Their finding demonstrates what’s possible when more people are included in the scientific process of finding and describing a new species, says Brenes-Mora.

“This story is an example of how we can learn from people that have been protecting and understanding nature on the ground,” he says.

Soto similarly hopes that finding Tlalocohyla celeste inspires his local community to document and report new and interesting species.

“There might be something hiding in their properties, in their lands, in their forests, that is an important addition to science,” says Soto. “I believe the more we know about what we have, the more we can do to protect it.”