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On her regular commute to the research facility, scientist the researcher crouches near a small pond surrounded by dense vegetation and retrieves a small green sound recorder.

The device was left there through the night to capture the characteristic croaks of the Fowler's snouted treefrog, recognized by local researchers as an non-native species with effects that scientists are starting to understand.

Although abounding with unique animals – such as ancient large turtles, swimming lizards, and the famous birds that inspired Darwin's theory of evolution – the Galápagos archipelago off the coast of South America had historically been free of frogs and toads.

In the late 1990s, this shifted. Several tiny amphibians made their way from continental the mainland to the archipelago, likely as stowaways on transport vessels.

Genetic research indicate that, through time, there have been multiple unintentional arrivals to the islands, and the frogs now have a strong presence on two locations: Isabela and Santa Cruz.

The numbers is expanding so rapidly that scientists have been struggling to monitor, calculating populations in the millions on each island, across urban and agricultural areas, but also in the conservation natural reserve.

When the biologist tagged frogs and attempted to find them in the following 10 days, 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 San José. "I'm pretty sure there are additional numbers."

Acoustic Chaos and Growing Concerns

The frogs' proliferation is evident from the acoustic chaos they create. "The amount of frogs and the noise – it's really insane," says the scientist.

For the researchers, their nightly mating calls are helpful in determining their presence in far-flung areas, using audio devices like the one outside San José's workplace.

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

"During the rainy period, I constantly hear their calls and they're really loud," says Jadira Larrea Saltos from Santa Cruz.

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

Environmental Consequences Stays Unclear

The sound isn't the primary problem, though. While the species has been in the islands for almost 30 years, experts still know limited information about its impact on the islands' delicately balanced land and water ecosystems.

On islands, it is very typical for non-native species to prosper, as they have few of their natural predators. The islands has 1,645 introduced types, many of which are significantly affecting the survival of its endemic ones.

A recent research indicates the invasive frogs are hungry bug eaters, and might be disproportionately consuming rare insects found only on the archipelago, or reducing the nutrition of the islands' uncommon birds, disrupting the ecosystem balance.

Unique Characteristics and Management Difficulties

The Galápagos frogs have shown some unusual characteristics, including living in slightly salty water, which is rare for amphibians.

Their development stage is also highly inconsistent, 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 lab for half a year.

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

Techniques to curb the frogs in the early 2000s were mostly unsuccessful. Conservation officers tried collecting significant quantities by hand and gradually increasing the salt content of lagoons in vain.

Research suggests spraying caffeine – which is highly toxic to frogs – or using electrical methods could help, but these approaches aren't always secure for other uncommon island organisms.

Without answers to more of the fundamental questions about their lifestyle and impact, culling the frogs might not even be the correct way to advance, says the biologist.

Funding Challenges for Study

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

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