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During her daily walk to the scientific station, biologist the researcher crouches near a small pond surrounded by thick vegetation and retrieves a small green audio recorder.

The device was left there through the night to capture the distinctive calls of the Fowler's snouted treefrog, known by Galápagos researchers as an invasive species with consequences that experts are just beginning to comprehend.

Despite abounding with remarkable animals – including centuries-old large turtles, swimming iguanas, and the well-known finches that sparked Darwin's evolutionary theory – the Galápagos archipelago off the coast of South America had long remained devoid of frogs and toads.

In the late 1990s, this shifted. Some tiny amphibians traveled from mainland Ecuador to the islands, likely as stowaways on cargo ships.

DNA studies indicate that, over the years, there have been repeated unintentional arrivals to the archipelago, and the frogs now have a firm presence on several islands: multiple locations.

The population is growing so rapidly that researchers have been struggling to keep track, estimating numbers in the hundreds of thousands on every island, across developed and agricultural areas, but also in the protected Galápagos national park.

When the biologist tagged amphibians and attempted to recapture them in the following 10 days, she could locate only a single tagged frog from time to time, indicating their populations were massive.

They estimated 6,000 frogs in a solitary pond. "The calculations are still very conservative," states the researcher. "I'm pretty sure there are even more."

Acoustic Chaos and Growing Concerns

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

For the scientists, their nightly vocalizations are helpful in determining their existence in remote areas, using audio devices like the one outside San José's workplace.

But local farmers say the calls are so raucous they keep them up at night.

"In the wet season, I regularly hear their calls and they're really loud," says Jadira Larrea Saltos from Santa Cruz.

"Initially it was a shock, seeing the first frogs in the region," says the farmer, who started observing their abundance about three years ago when one jumped on her palm as she was walking out of her house.

Ecological Impact Remains Unclear

The noise isn't the primary problem, however. While the species has been in the Galápagos for nearly three decades, scientists still know very little about its impact on the islands' delicately balanced land and water environments.

On islands, it is very common for non-native species to thrive, as they have few of their enemies. The islands has 1,645 invasive types, many of which are significantly disrupting the safety of its native ones.

A 2020 study indicates the non-native frogs are voracious bug consumers, and might be disproportionately consuming rare insects found only on the islands, or reducing the nutrition of the islands' rare birds, affecting the ecosystem balance.

Unique Characteristics and Management Difficulties

The Galápagos frogs have exhibited some unusual characteristics, including surviving in slightly salty water, which is uncommon for frogs.

Their metamorphosis process is also extremely inconsistent, with some tadpoles turning into frogs very quickly and others taking a long time: the researcher witnessed one which remained as a tadpole in her lab for half a year.

"We really don't know this aspect," she says, concerned the tadpoles could be affecting the islands' freshwater, a very limited resource in the islands.

Methods to control the frogs in the beginning of the century were mostly ineffective. Park rangers tried capturing significant quantities by hand and slowly raising the salt content of ponds in without success.

Studies indicates applying coffee – which is highly poisonous to frogs – or using electrical methods could assist, but these methods aren't necessarily secure for other rare Galápagos organisms.

Lacking answers to more of the basic questions about their biology and impact, culling the amphibians might not even be the right way to proceed, says the biologist.

Financial Obstacles for Study

While she hopes the growing use of environmental DNA techniques and genetic examination will assist her team make sense of the invader, financial support for the project has been hard to come by.

"Everyone wants to give funding for preserving frogs," says the researcher. "But it's harder to find funding for an invasive frog that you might want to manage."