It’s raining tiny toxic frogs

Poison dart frogs are hard to miss. They’re bright, agile, and as their name suggests, toxic. But at least a few  of these showy amphibians have gone under the radar, until now. Scientists surveying a difficult to reach area of the Brazilian Amazon report two new species in a set of recent papers. The first, published in April in the journal ZooKeys, describes the teal and black Ranitomeya aquamarina. The second, released May 14 in the journal PLOS One, introduces the light blue striped Ranitomeya aetherea.

Despite how frequently novel amphibian species are found elsewhere,  the frogs are the first newly described members of their genus in 13 years. Reaching their habitat requires flying on a small plane, followed by a 10-hour boat journey along the river, Esteban Diego Koch, a study co-author and PhD candidate in evolutionary biology at the National Institute of Amazonian Research, tells Popular Science. 

That long trek for humans is a major part of why the species stayed formally undiscovered for so long, he says. It takes years to properly prepare to survey such a remote region and to build relationships with the local Indigenous community, who were instrumental in assisting and guiding the outside researchers. 

Both of the poison dart species were discovered in pockets of open forest about 30 miles apart, along the banks of the Juruá River in western Brazil, near the border of Peru, Each species has an affinity for the same palm-like plant, with tadpoles that grow up inside the small, ephemeral pools of water that collect at the base of the leaf stalks. They spend their days perched on these plants or foraging in the nearby leaf litter, likely eating the toxic insects that help them build up their own reserves of deadly chemicals. 

The frogs are named in reference to the color of the striking stripes on their backs. R. aquamarina has an array of bright turquoise lines running against a jet black background, while R. aetherea (Latin for ‘heavenly’), displays angelic, sky blue stripes against brick red. The two species share copper-colored, spotted metallic legs that resemble safari-print pants and are both about 15-17 millimeters long, about the diameter of a dime. 

Despite all their similarities, the amphibians seem to lead divergent lives, especially when it comes to mating. The scientists most often found adult R. aquamarina in pairs, suggesting the frogs couple-up to breed and stay together for an extended period of time. This type of monogamy is rare in amphibians and was only first discovered 15 years ago in another dart frog species. In contrast, R. aetherea appears to play the field. Males of the sky blue species were generally sighted solo, emitting frequent advertising calls, and switching to a courtship call when approached by females, who don’t stick around in one place for very long. 

It’s a testament to how deceiving looks can be. Dart frogs have a complex evolutionary history of species emerging and subsequently re-hybridizing. In this genus of frogs, “very distinct species can have the same appearance: the same colors and the same pattern,” Koch says. Adding to the confusion, “sometimes a single species can have multiple patterns of color,” he notes.

Since going by appearance alone isn’t enough, the scientists conducted extensive analyses of both types of frogs to confirm that the striped and spotted dart frog specimens truly represented two new species. They used genetic sequencing, compared the sound waves of mating calls, and took exceptionally accurate measurements of dozens of frogs under a microscope.

They found that the two species were quite distinct, and not as closely related as one might expect. The frogs are nested in different areas of the evolutionary tree, with separate sister species, according to the genetic analysis. However, Koch notes that more data is needed to confirm the exact relationships. 

With more research, additional surprises are likely to emerge. At least one more possible new species was collected in the recent surveys, Koch says. He and his colleagues just have to finish their assessment to know for sure. Beyond what’s already been found, Koch  imagines that many more unidentified amphibians are lurking in similarly difficult to access corners of the Amazon. 

The hard part is getting to them before they’re gone. Deforestation, climate change, increasingly frequent wildfires, and pet trade poaching all threaten poison dart frogs. The frogs of these two new studies were collected across two expeditions in 2023 and 2024. In just that one year gap, Koch says his colleagues noted a big change, with clear cuts and deforestation moving much closer to the amphibians’ habitat.

The scientists currently don’t have enough information to know exactly how secure or at-risk either species is. Yet, given that they found each amphibian in a small range, spotted across just a couple of miles of forest, it seems likely that the toxic frogs themselves are in much more danger than their poison poses to their predators. Losing them would mean losing two especially beautiful branches on the tree of life. It would also stymie our ability to harness their potential power. Chemicals from the skin of specific dart frogs have shown promise as possible medicines. 

“It’s a long road,” from discovering a species to discovering its potential human applications, says Koch. “Someday, they might be useful,” he says. But, to get there, we have to let the frogs stick around. 

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