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During her daily commute to the scientific station, biologist the researcher crouches near a shallow water body covered by dense vegetation and retrieves a small green audio device.

The device was left there overnight to record the characteristic croaks of the Fowler's snouted treefrog, known by local researchers as an non-native threat with effects that scientists are just beginning to comprehend.

Although teeming with unique animals – including centuries-old large turtles, swimming iguanas, and the famous finches that sparked Charles Darwin's theory of evolution – the Galápagos archipelago near the shoreline of South America had long remained free of amphibians.

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

DNA studies suggest that, over the years, there have been repeated accidental arrivals to the archipelago, and the amphibians now have a firm foothold on two locations: multiple locations.

The numbers is growing so quickly that scientists have been finding it difficult to monitor, calculating populations in the millions on every island, across urban and agricultural areas, but also in the conservation natural reserve.

When the biologist tagged amphibians and attempted to find them in the subsequent week and a half, she could find only a single tagged frog occasionally, indicating their populations were enormous.

They calculated 6,000 frogs in a solitary pond. "The calculations are still very low," states the researcher. "I am quite certain there are even more."

Acoustic Chaos and Rising Worries

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

For the researchers, their nightly mating calls are useful in determining their presence in remote areas, using audio devices like the one near San José's office.

But local agricultural workers say the calls are so loud they prevent sleep at night.

"In the rainy period, I constantly hear their croaks and they're extremely loud," says Jadira Larrea Saltos from Santa Cruz.

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

Ecological Impact Remains Unknown

The noise isn't the primary problem, though. While the amphibians has been in the Galápagos for nearly 30 years, experts still know very little about its impact on the islands' delicately balanced terrestrial and aquatic ecosystems.

On islands, it is very common for invasive species to thrive, as they have few of their enemies. The islands has over sixteen hundred invasive types, many of which are significantly disrupting the survival of its endemic ones.

A recent study suggests the non-native frogs are voracious bug eaters, and might be disproportionately eating uncommon insects found only on the islands, or depleting the nutrition of the islands' uncommon birds, affecting the food chain.

Unique Characteristics and Control Challenges

The Galápagos frogs have shown some atypical traits, including living in brackish water, which is rare for amphibians.

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

"We truly don't know this aspect," she says, worried the larvae could be affecting the region's clean water, a very scarce resource in the islands.

Techniques to control the amphibians in the early 2000s were mostly ineffective. Conservation officers tried collecting large numbers by hand and slowly increasing the salt content of lagoons in vain.

Studies indicates applying coffee – which is extremely poisonous to amphibians – or using electrocution could assist, but these methods aren't necessarily safe for other uncommon Galápagos organisms.

Lacking answers to more of the fundamental issues about their lifestyle and effect, removing the amphibians might not even be the right way to advance, says the biologist.

Funding Challenges for Study

While she expects the growing use of eDNA techniques and genetic examination will help her team understand of the invasive species, funding for the project has been hard to come by.

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