On the foothills of the Andes in central Peru, a brilliantly colored frog lives out a fractured fairy tale.

Once upon a time—specifically, one evening in November 2014—biologist Germán Chávez heard a call echo through the highest-altitude forests of Tingo María National Park. Chávez didn’t recognize the call, so he went out to find the source of the distinctive chirps. Up in a tree, he found a little brown frog less than an inch (2.5 centimeters) long—and quickly realized that like the frogs in stories, this one was more than meets the eye.

“We could see the bright red legs, and that was a surprise,” says Chávez, a biologist with Peru’s Center of Ornithology and Biodiversity. “We have never seen a frog like that.”

Frogs come in a dazzling variety of colors, and depending on the genus, so do their crotches: Related frogs have splotches of yellow, brown, and even orange on their groins, thighs, and shanks. But to see such bright pigmentation—and red, at that—caught the researchers off-guard. (See “New Amazon Frog Named After Mythical Monster.”)

“The exact function [of the pigment] for this species? We don’t know,” says co-discoverer Alessandro Catenazzi of Southern Illinois University. “But we start with putting a name on it.”

After two years of analysis, Chávez and Catenazzi have confirmed that the scarlet-shanked frog represents a species new to science. Its name, Pristimantis pulchridormientes, or the sleeping beauty rain frog, is a nod to the mountain range where the frog was found, which locals describe as resembling a sleeping reclined woman.

View Images The bright red groin of a male Pristimantis pulrhcidormientes. Photograph by Germán Chávez

A (Newly) Safe Haven

The discovery, published recently in ZooKeys, adds to the ever-growing ranks of Pristimantis, a genus of tropical frog that hosts stunning diversity—131 species live in Peru alone—yet has gone understudied for decades.

“When I was introduced to some of these species in the field, I asked, ‘Why don’t people study these frogs?’ And [a graduate student] said, ‘Well, it’s hard to get people excited about a little brown frog,’” says biologist Katherine Krynak of Ohio Northern University, who wasn’t involved with the study.

“Which I just thought was crazy, because they’re not just little brown frogs—but if you don’t look carefully enough, that’s what you assume.” (Also see "Seven New Mini-Frogs Found—Among Smallest Known.")

Scientists now have shown that Pristimantis is anything but boring, inspired by the trailblazing research of herpetologists such as William Duellman and John Lynch. In recent years, biologists have found kaleidoscopic Pristimantis species, some of which even resemble tie-dye T-shirts. One Pristimantis species that Krynak co-discovered can even shape-shift, going from smooth-skinned to spiky in the blink of an eye—the only known vertebrate that can pull off the trick.

But adding to Pristimantis’s ranks wasn’t the only important outcome of the 2014 expedition to Tingo María. In fact, the survey that turned up the sleeping beauty rain frog was the first-ever species inventory of Tingo María National Park. The catalog was long overdue: Tingo María was founded in 1965, putting it among the oldest of Peru’s national parks.

Why had the park gone so long without a closer look? For one, says Catenazzi, the park was established primarily to preserve La Cueva de las Lechuzas, or Cave of the Owls, a notable bird and bat habitat, and the “Sleeping Beauty” mountain range—but not to protect forest biodiversity.

Stumbling Upon a Tiny New Frog Species by Night November 15, 2012—See how, late one evening in a remote Peruvian cloud forest, a National Geographic explorer happened upon a big little discovery—a new frog to go with seven other new species found during the expedition.

In addition, the 18-square-mile (48-square-kilometer) protected area only recently became safe enough for fieldwork. Through the 1980s, cocaine trafficking near the park flourished, and in the surrounding valleys, Peruvian government forces bitterly fought against Sendero Luminoso (Shining Path), a leftist rebel group. But the area has improved significantly, and as of 2015, there was no evidence of coca cultivation in the park.

“We now consider it a safe place to work,” says Chávez.

Save Frogs, Save Ourselves

Catenazzi and Chávez hope that the discovery bolsters the case for protecting Tingo María, both by documenting its hidden diversity and by showing how important the area can be for research.

“In general, the more scientific work is done in a protected area, the more it ends up being protected,” says Catenazzi. “People respect that, and that adds a lot to the value of the park.”

And the scientists warn that frogs not just in Tingo María, but across the region, remain under threat from the global amphibian pet trade, the insidious spread of deadly chytrid fungus, and deforestation caused by oil and mining developments. (Read about how to rescue adorable tree frogs.)

“There are so many things we’re going to need to change to save these species, and ourselves, in the end,” says Krynak. “These amphibians are telling us that we are not doing right by the environment, and we need to listen.”