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During her daily walk to the scientific station, scientist the researcher stoops near a shallow water body surrounded by thick vegetation and collects a compact plastic audio device.

She had placed there through the night to capture the characteristic calls of the Fowler's snouted treefrog, recognized by Galápagos scientists as an invasive species with effects that experts are just beginning to comprehend.

Despite abounding with unique animals – such as centuries-old giant tortoises, swimming iguanas, and the well-known finches that sparked Darwin's evolutionary theory – the island chain off the shoreline of South America had long remained free of amphibians.

In the late 1990s, this shifted. Some small tree frogs made their way from continental the mainland to the archipelago, probably as stowaways on transport vessels.

DNA studies indicate that, over the years, there have been repeated accidental arrivals to the archipelago, and the frogs now have a firm presence on several locations: Isabela and Santa Cruz.

The population is growing so quickly that researchers have been finding it difficult to keep track, calculating populations in the hundreds of thousands on every island, across urban and farming areas, but also in the conservation natural reserve.

When the biologist marked frogs and attempted to find them in the subsequent 10 days, she could find just one tagged frog occasionally, suggesting their numbers were massive.

They calculated 6,000 frogs in a single pond. "The calculations are still very conservative," states the researcher. "I'm quite certain there are additional numbers."

Acoustic Chaos and Rising Worries

The frogs' abundance is clear from the acoustic disruption they cause. "The number of frogs and the noise – it's truly insane," says the scientist.

For the researchers, their nightly vocalizations are helpful in determining their existence in remote areas, using recorders like the one outside the workplace.

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

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

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

Ecological Impact Remains Unclear

The noise isn't the primary problem, though. While the species has been in the Galápagos for nearly 30 years, experts still know very little about its impact on the archipelago's precariously balanced land and water environments.

On archipelagos, it is very common for invasive species to prosper, as they have none of their enemies. The Galápagos counts over sixteen hundred introduced species, many of which are seriously disrupting the survival of its native ones.

A recent study indicates the invasive frogs are hungry insect consumers, and might be unevenly consuming rare bugs found exclusively on the islands, or depleting the food sources of the region's rare birds, disrupting the ecosystem balance.

Unique Characteristics and Control Challenges

The island frogs have shown some atypical traits, including surviving in slightly salty water, which is rare for amphibians.

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

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

Methods to control the amphibians in the early 2000s were largely unsuccessful. Conservation officers tried capturing significant quantities by manual methods and slowly increasing the salt content of ponds in without success.

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

Without answers to more of the basic issues about their lifestyle and effect, removing the frogs might not even be the right way to advance, says San José.

Financial Obstacles for Research

While she expects the growing use of eDNA methods and DNA examination will help her team make sense of the invader, financial support for the research has been hard to come by.

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