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During her regular commute to the research facility, biologist the researcher crouches near a shallow water body covered by thick vegetation and retrieves a small green sound device.

She had placed there overnight to capture the distinctive calls of the Scinax quinquefasciatus, known by local researchers as an invasive species with effects that experts are just beginning to comprehend.

Although teeming with remarkable animals – including centuries-old large turtles, marine iguanas, and the well-known finches that sparked Charles Darwin's theory of evolution – the Galápagos archipelago near the shoreline of South America had long remained free of frogs and toads.

During the 1990s, this shifted. Some tiny amphibians traveled from continental Ecuador to the archipelago, likely as stowaways on transport vessels.

Genetic research indicate that, over the years, there have been multiple accidental introductions to the archipelago, and the amphibians now have a strong foothold on two locations: Isabela and Santa Cruz.

The population is expanding so quickly that scientists have been struggling to keep track, estimating numbers in the hundreds of thousands on each 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 10 days, she could find just one tagged frog occasionally, suggesting their populations were enormous.

They calculated 6,000 frogs in a single pond. "The calculations are still very conservative," says San José. "I'm quite certain there are even more."

Deafening Noise and Growing Concerns

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

For the scientists, their nocturnal mating calls are useful in determining their existence in remote areas, using audio devices like the one near the office.

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

"In the wet season, 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 area," says the farmer, who started observing their large numbers about three years ago when one jumped on her palm as she was walking out of her house.

Environmental Consequences Stays Unknown

The noise isn't the primary problem, however. While the species has been in the islands for almost three decades, experts still know very little about its impact on the islands' delicately balanced land and water environments.

On islands, it is very common for invasive species to thrive, as they have few of their natural predators. The Galápagos counts 1,645 invasive species, many of which are significantly disrupting the safety of its endemic ones.

A recent study indicates the non-native amphibians are voracious bug consumers, and might be disproportionately eating uncommon bugs found exclusively on the islands, or reducing the nutrition of the region's rare birds, affecting the ecosystem balance.

Unusual Traits and Control Challenges

The Galápagos amphibians have exhibited some atypical traits, including surviving in brackish water, which is rare for amphibians.

Their metamorphosis stage is also extremely inconsistent, with some tadpoles turning into frogs very quickly and others taking a extended period: San José observed one which remained as a larva in her lab for six months.

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

Methods to curb the amphibians in the early 2000s were mostly unsuccessful. Park rangers tried capturing large numbers by hand and slowly increasing the salinity of lagoons in vain.

Research indicates applying coffee – which is highly poisonous to frogs – or using electrical methods could help, but these approaches aren't always secure for other rare island species.

Without answers to more of the basic questions about their lifestyle and effect, culling the frogs might not even be the right way to proceed, says the biologist.

Financial Obstacles for Research

While she expects the growing use of environmental DNA methods and DNA examination will help her team understand of the invader, funding for the research has been difficult to obtain.

"Everyone wants to give funding for protecting frogs," says San José. "But it's harder to find financial backing for an invasive frog that you might want to control."