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During her regular commute to the research facility, scientist the researcher stoops near a small pond surrounded by thick plants and retrieves a small plastic audio recorder.

The device was left there overnight to capture the distinctive croaks of the Scinax quinquefasciatus, recognized by Galápagos scientists as an non-native threat with effects that scientists are starting to comprehend.

Although abounding with unique animals – such as centuries-old giant tortoises, marine lizards, and the famous finches that inspired Darwin's theory of evolution – the Galápagos archipelago near the coast of South America had long remained devoid of amphibians.

In the late 1990s, this shifted. Some small tree frogs made their way from mainland Ecuador to the islands, likely as hitchhikers on transport vessels.

Genetic studies indicate that, over the years, there have been repeated accidental introductions to the islands, and the amphibians now have a strong presence on several islands: multiple locations.

The population is expanding so quickly that researchers have been finding it difficult to keep track, calculating populations in the millions on each island, across developed and agricultural areas, but also in the conservation natural reserve.

When San José tagged amphibians and attempted to find them in the subsequent 10 days, she could find only a single tagged frog occasionally, indicating their populations were enormous.

They calculated six thousand frogs in a single pond. "Our estimates are still very conservative," states the researcher. "I am pretty sure there are additional numbers."

Deafening Noise and Growing Concerns

The amphibians' abundance is clear from the sound disruption they create. "The number of frogs and the noise – it's truly incredible," comments the scientist.

For the scientists, their nocturnal mating calls are helpful in determining their existence in far-flung areas, using audio devices like the one outside the office.

But nearby farmers say the calls are so loud they keep them up at night.

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

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

Ecological Impact Stays Unclear

The noise isn't the primary problem, though. While the amphibians has been in the islands for nearly three decades, experts still know very little about its impact on the archipelago's delicately balanced land and water ecosystems.

On islands, it is very typical for invasive species to prosper, as they have few of their natural predators. The islands has over sixteen hundred invasive species, many of which are significantly disrupting the survival of its native ones.

A 2020 research suggests the invasive frogs are hungry bug eaters, and might be unevenly consuming rare insects found only on the islands, or depleting the nutrition of the region's rare birds, disrupting the ecosystem balance.

Unusual Traits and Control Challenges

The island frogs have exhibited some atypical characteristics, including living in slightly salty water, which is rare for frogs.

Their development process is also highly variable, with some larvae turning into frogs very rapidly and others taking a long time: the researcher observed one which stayed as a larva in her laboratory for half a year.

"We truly don't know this part," she says, concerned the larvae could be impacting the region's freshwater, a very limited commodity in the islands.

Techniques to control the amphibians in the beginning of the century were largely ineffective. Park rangers tried collecting significant quantities by manual methods and gradually increasing the salinity of lagoons in vain.

Research indicates applying caffeine – which is extremely poisonous to frogs – or using electrocution could assist, but these methods aren't always safe for other rare Galápagos organisms.

Lacking answers to more of the basic questions about their lifestyle and effect, removing the frogs might not even be the right way to advance, says the biologist.

Financial Obstacles for Study

While she hopes the growing use of eDNA methods and genetic examination will help her team understand of the invader, funding for the project has been hard to obtain.

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