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On her daily commute to the research facility, scientist the researcher stoops near a shallow water body covered by thick plants and collects a small green audio recorder.

She had placed there through the night to capture the characteristic croaks of the Fowler's snouted treefrog, known by local researchers as an invasive threat with effects that experts are just beginning to comprehend.

Although abounding with remarkable animals – including ancient giant tortoises, marine lizards, and the well-known finches that sparked Darwin's theory of evolution – the island chain near the shoreline of Ecuador had long remained devoid of frogs and toads.

During the 1990s, this shifted. Several small tree frogs made their way from continental Ecuador to the islands, likely as stowaways on transport vessels.

Genetic studies indicate that, through time, there have been multiple accidental arrivals to the archipelago, and the amphibians now have a firm foothold on two locations: Isabela and Santa Cruz.

The population is growing so rapidly that scientists have been struggling to monitor, calculating populations in the hundreds of thousands on each island, across urban and farming areas, but also in the protected natural reserve.

When the biologist marked frogs and attempted to recapture them in the following 10 days, she could locate only a single marked frog from time to time, indicating their populations were massive.

They estimated 6,000 frogs in a solitary pond. "Our estimates are still very conservative," says the researcher. "I am quite certain there are additional numbers."

Deafening Noise and Growing Concerns

The frogs' abundance is evident from the acoustic chaos they create. "The amount of frogs and the sound – it's truly 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 near the workplace.

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

"In the rainy period, I regularly hear their calls and they're extremely loud," says a local coffee farmer from Santa Cruz.

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

Environmental Consequences Stays Unclear

The noise isn't the fundamental problem, though. While the species has been in the Galápagos for nearly three decades, scientists 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 enemies. The Galápagos has 1,645 invasive species, many of which are significantly affecting the survival of its native ones.

A recent study indicates the non-native frogs are voracious insect consumers, and might be unevenly consuming uncommon bugs found exclusively on the archipelago, or reducing the food sources of the region's rare avian species, disrupting the food chain.

Unusual Traits and Control Challenges

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

Their metamorphosis process is also extremely inconsistent, with some larvae turning into frogs very rapidly and others taking a extended period: San José observed one which remained as a larva in her lab for half a year.

"We really don't know this aspect," she says, worried the tadpoles could be impacting the region's freshwater, a very scarce resource in Galápagos.

Methods to curb the frogs in the beginning of the century were largely ineffective. Conservation officers tried collecting large numbers by manual methods and gradually increasing the salt content of ponds in without success.

Research indicates applying caffeine – which is highly toxic to frogs – or using electrical methods could help, but these approaches aren't always safe for other uncommon Galápagos organisms.

Lacking answers to more of the basic issues about their biology and effect, removing the amphibians might not even be the right way to advance, says the biologist.

Financial Obstacles for Research

While she hopes the increasing use of eDNA methods and DNA analysis will assist her team understand of the invasive species, funding for the research has been difficult to come by.

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