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On her daily commute to the scientific station, scientist the researcher stoops near a shallow water body surrounded by thick plants and collects a compact plastic sound device.

She had placed there overnight to capture the distinctive calls of the Scinax quinquefasciatus, recognized by local researchers as an non-native threat with consequences that experts are just beginning to comprehend.

Despite abounding with unique wildlife – such as centuries-old giant tortoises, marine lizards, and the well-known birds that inspired Charles Darwin's evolutionary theory – the Galápagos archipelago off the coast of South America had long remained free of frogs and toads.

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

DNA research suggest that, over the years, there have been multiple accidental introductions to the islands, and the frogs now have a firm presence on two islands: Isabela and Santa Cruz.

The numbers is expanding so quickly that scientists have been struggling to monitor, calculating populations in the hundreds of thousands on every island, across developed and agricultural areas, but also in the conservation Galápagos national park.

When San José tagged frogs and attempted to recapture them in the following week and a half, she could locate just one marked frog occasionally, suggesting their populations were massive.

They estimated 6,000 frogs in a solitary pond. "Our estimates are still very conservative," says San José. "I'm quite certain there are additional numbers."

Acoustic Chaos and Rising Worries

The amphibians' proliferation is evident from the sound chaos they cause. "The amount of frogs and the sound – it's really incredible," says San José.

For the scientists, their nocturnal mating calls are useful in determining their presence in remote areas, using audio devices like the one outside the workplace.

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

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

"At first it was a surprise, observing the initial frogs in the area," says Larrea Saltos, 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 Remains Unknown

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

On islands, it is very common for non-native species to prosper, as they have none of their enemies. The islands counts over sixteen hundred introduced species, many of which are significantly affecting the survival of its endemic ones.

A recent study suggests the invasive frogs are voracious insect eaters, and might be unevenly eating uncommon bugs found only on the islands, or depleting the nutrition of the islands' rare avian species, affecting the ecosystem balance.

Unusual Traits and Management Difficulties

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

Their metamorphosis stage is also highly variable, with some larvae turning into frogs very quickly and others taking a extended period: the researcher witnessed one which remained as a larva in her lab for half a year.

"We really don't know this aspect," she says, concerned the larvae could be impacting the region's clean water, a very limited commodity in Galápagos.

Methods to curb the amphibians in the beginning of the century were largely unsuccessful. Park rangers tried collecting large numbers by manual methods and slowly increasing the salinity of ponds in vain.

Research indicates applying coffee – which is extremely toxic to frogs – or using electrical methods could help, but these methods aren't necessarily secure for other uncommon Galápagos species.

Lacking solutions to more of the fundamental questions about their lifestyle and effect, removing the frogs might not even be the right way to proceed, says the biologist.

Funding Challenges for Research

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

"Everyone wants to give support for preserving frogs," says the researcher. "But it's harder to find financial backing for an introduced frog that you might want to control."