Tapir valley tree frog.

Its unusual, shrill call had researchers intrigued.

An interesting and unusual call helped a naturalist in Costa Rica discover a new species of frog.

The tapir valley tree frog (Tlalocohyla celeste) is tiny and mostly green with red spots and blue armpits. The frog was described for the first time in a recent paper in the journal Zootaxa.1

Donald Varela Soto, co-owner of Tapir Valley Nature Reserve, was intrigued when he first heard the frog’s shrill calls.

“We as country boys, we know sounds,” said Soto, who is the paper’s lead author. “I grew up in the countryside; I grew up in the forests walking around learning to identify species of trees, birds, and frogs. I listened to this little frog and it was almost impossible to find it, it was so well camouflaged. I was really happy when I found it because I had been trying to find the frog that was making that unusual call for six months after I first heard it.”2

He heard the frog for the first time about four years ago when he was working around a pond after the first heavy rains of the year. The sound was so distinct that he had to find the creature making it.

“He began listening and studying the sounds of the wetland at night; there are around 16 other frog species inhabiting it, all producing different calls,” biologist Valeria Espinall, who helped spot the frog, tells Treehugger. “There was a particular shrill call that seemed to be very abundant. Donald followed the sound and it was the same tiny green frog.”

The frog was only about 2 centimeters (.79 inches) and was so well-hidden in the tall grasses that it was nearly impossible to see. It was mostly green with blue armpits, red spots, and a yellow line that runs partially down its sides.2

Searching for Tadpoles

In order to tell how different the species was from other similar frogs, researchers went looking for tadpoles, which can help identify the genus. Finding tadpoles allows them to describe the entire life cycle and also helps them know what habitat the frog needs in order to survive.3

“The almost permanent waters of the wetland are the necessary site for its reproduction,” herpetologist Juan Abarca tells Treehugger. “Without knowing what the tadpole is like, where it lives and what requirements it needs for its development, it is not possible to investigate or protect this species in future conservation actions, which we are starting to develop.”

Because there were so many other species in the wetland, they couldn’t be sure which ones belonged to the new frog. The best way to know for sure is to find frogs in a mating position, called amplexus, and then follow the female until she lays her eggs.3

Researchers looked for months at night but never were able to find the frogs in the mating embrace. So they decided to look for them in the very early morning hours.

Tapir valley tree frogs in mating embrace.

“That is why one day we did not go at dusk as usual, but instead we left at 4:00 in the morning to see if we were lucky, and after searching quite a lot just as dawn was beginning (at 5:00 h) we observed the first amplexus reported for that species, and with great luck, they were just in the process of ovipositing,” Abarca says.

They were thrilled with their discovery.

“The emotion at that moment was double, not only for seeing the amplexus for the first time, but also for confirming what the egg laying was like and being able to see for the first time a natural event that no one had witnessed before,” Abarca says.

“The emotion that it gave us at that moment was one of the most enriching experiences that I have felt during all the time that I have worked with wildlife. The feeling of being a pioneer and being able to have something new and interesting to show the world,  it's like to recover that capacity for child wonder that is often lost as an adult person.”

The frog was found in a former cattle ranch that was harmed by deforestation and lots of cattle activity. Donald Varela Soto and his co-owners turned it into a nature reserve.4

“Donald wanted to get rid of all the cows and restore the landscape to create an ecotourism hotspot,” says Espinall. “Little did he know, a new species was hiding right there. The strongest message here is that when we protect habitat we protect even what we don’t know exists.”

Fact checked by Haley Mast