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On her regular commute to the scientific station, scientist the researcher crouches near a small pond surrounded by dense plants and collects a compact plastic sound recorder.

The device was left there overnight to capture the distinctive croaks of the Scinax quinquefasciatus, recognized by local researchers as an non-native threat with effects that experts are just beginning to understand.

Despite teeming with remarkable animals – such as centuries-old large turtles, marine lizards, and the well-known birds that inspired Darwin's theory of evolution – the island chain off the shoreline of South America had long remained devoid of frogs and toads.

During the 1990s, this shifted. Some small amphibians traveled from continental the mainland to the islands, likely as hitchhikers on cargo ships.

Genetic studies indicate that, over the years, there have been repeated unintentional introductions to the archipelago, and the frogs now have a firm foothold on several islands: Isabela and Santa Cruz.

The numbers is growing so rapidly that scientists have been struggling to keep track, estimating populations in the hundreds of thousands on each island, across developed and agricultural areas, but also in the conservation natural reserve.

When San José tagged frogs and attempted to recapture them in the subsequent 10 days, she could locate just one marked frog occasionally, suggesting their populations were enormous.

They estimated six thousand frogs in a single pond. "The calculations are still very low," says the researcher. "I'm pretty sure there are even more."

Acoustic Chaos and Growing Concerns

The frogs' abundance is evident from the sound disruption they create. "The amount of frogs and the noise – it's really insane," says the scientist.

For the researchers, their nightly mating calls are helpful in determining their existence in remote areas, using recorders like the one near San José's office.

But nearby farmers say the calls are so loud they prevent sleep at night.

"In the rainy period, I constantly hear their calls and they're extremely loud," says a local coffee farmer from Santa Cruz.

"Initially it was a surprise, seeing the initial frogs in the area," says the farmer, who started noticing their large numbers about three years ago when one leaped on her palm as she was stepping out of her house.

Ecological Impact Remains Unclear

The noise isn't the fundamental problem, though. While the species has been in the Galápagos for nearly 30 years, experts still know limited information about its impact on the archipelago's delicately balanced land and water ecosystems.

On archipelagos, it is very common for non-native species to prosper, as they have none of their natural predators. The Galápagos has 1,645 invasive species, many of which are seriously disrupting the survival of its endemic ones.

A 2020 research suggests the invasive frogs are voracious bug consumers, and might be disproportionately eating uncommon insects found exclusively on the archipelago, or reducing the food sources of the region's rare birds, disrupting the ecosystem balance.

Unusual Traits and Control Challenges

The island amphibians have shown some atypical traits, including living in slightly salty water, which is uncommon for amphibians.

Their development stage is also extremely inconsistent, with some tadpoles becoming frogs very rapidly and others taking a long time: San José observed one which stayed as a tadpole in her laboratory for half a year.

"We truly don't know this part," she says, concerned the tadpoles could be impacting the region's freshwater, a very scarce resource in Galápagos.

Techniques to curb the frogs in the early 2000s were largely ineffective. Park rangers tried capturing large numbers by hand and slowly increasing the salinity of lagoons in without success.

Studies indicates applying coffee – which is highly toxic to frogs – or using electrical methods could assist, but these methods aren't always safe for other uncommon Galápagos species.

Lacking answers to more of the fundamental questions about their biology and impact, removing the frogs might not even be the correct way to advance, says San José.

Funding Challenges for Study

While she hopes the growing use of eDNA techniques and DNA examination will assist her team understand of the invasive species, funding for the project has been difficult to obtain.

"Everyone wants to give support for preserving frogs," says the researcher. "But it's more difficult to find financial backing for an invasive frog that you might want to control."