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During her daily walk to the research facility, biologist the researcher crouches near a small pond covered by dense plants and collects a small green audio recorder.

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

Although abounding with remarkable wildlife – such as ancient 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 historically been free of frogs and toads.

In the late 1990s, this shifted. Some small amphibians made their way from mainland Ecuador to the archipelago, probably as hitchhikers on cargo ships.

DNA studies indicate that, through time, there have been multiple accidental introductions to the islands, and the amphibians now have a firm foothold on several locations: multiple locations.

The population is growing so quickly that scientists have been struggling to monitor, estimating populations in the millions on every island, across developed and farming areas, but also in the conservation natural reserve.

When the biologist marked frogs and attempted to recapture them in the following week and a half, she could find only a single marked frog occasionally, indicating their numbers were enormous.

They calculated six thousand frogs in a solitary pond. "Our estimates are still very low," says the researcher. "I'm quite certain there are additional numbers."

Acoustic Chaos and Rising Worries

The frogs' abundance is evident from the acoustic disruption they create. "The number of frogs and the noise – it's really insane," comments the scientist.

For the researchers, their nocturnal vocalizations are useful in estimating their existence in far-flung areas, using audio devices like the one near the office.

But local agricultural workers say the sounds are so raucous they keep them up at night.

"During the wet season, I regularly hear their calls and they're extremely loud," says a local coffee farmer from the island.

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

Environmental Consequences Remains Unknown

The noise isn't the fundamental problem, however. 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 terrestrial and aquatic environments.

On archipelagos, it is very typical for invasive species to thrive, as they have none of their enemies. The Galápagos counts over sixteen hundred invasive types, many of which are significantly disrupting the safety of its endemic ones.

A 2020 research indicates the non-native amphibians are hungry bug consumers, and might be disproportionately eating rare bugs found exclusively on the archipelago, or reducing the food sources of the islands' rare avian species, affecting the ecosystem balance.

Unusual Traits and Management Difficulties

The island amphibians have shown some atypical characteristics, including living in brackish water, which is rare for amphibians.

Their metamorphosis stage is also highly inconsistent, with some larvae turning into frogs very quickly and others taking a long time: the researcher witnessed one which remained as a tadpole in her laboratory for six months.

"We truly don't know this part," she says, concerned the larvae could be impacting the islands' clean water, a very scarce commodity in the islands.

Techniques to curb the amphibians in the beginning of the century were largely unsuccessful. Conservation officers tried collecting significant quantities by hand and slowly raising the salinity of lagoons in without success.

Research suggests applying caffeine – which is highly toxic to amphibians – or using electrical methods could assist, but these methods aren't always secure for other uncommon island species.

Lacking solutions to more of the basic issues about their biology and effect, culling the amphibians might not even be the correct way to advance, says the biologist.

Financial Obstacles for Study

While she expects the growing use of environmental DNA methods and DNA examination will help her team understand of the invader, funding for the project has been hard to come by.

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