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During her regular walk to the scientific station, biologist the researcher stoops near a shallow water body surrounded by thick vegetation and collects a compact green audio recorder.

She had placed there overnight to capture the characteristic calls of the Fowler's snouted treefrog, recognized by Galápagos scientists as an non-native threat with consequences that experts are starting to comprehend.

Despite teeming with remarkable animals – such as ancient giant tortoises, marine lizards, and the well-known birds that inspired Charles Darwin's theory of evolution – the island chain near the shoreline of Ecuador had long remained free of amphibians.

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

DNA research indicate that, over the years, there have been multiple accidental introductions to the archipelago, and the amphibians now have a firm presence on several locations: multiple locations.

The numbers is growing so rapidly that researchers have been finding it difficult to keep track, calculating numbers in the millions on every island, across developed and agricultural areas, but also in the protected natural reserve.

When the biologist tagged amphibians and attempted to find them in the subsequent week and a half, she could find only a single tagged frog occasionally, indicating their populations were enormous.

They estimated six thousand frogs in a solitary pond. "Our estimates are still very low," says the researcher. "I am pretty sure there are additional numbers."

Deafening Noise and Rising Worries

The amphibians' abundance is clear from the acoustic chaos they cause. "The amount of frogs and the noise – it's truly insane," comments the scientist.

For the researchers, their nocturnal mating calls are useful in determining their presence in far-flung areas, using audio devices like the one near the office.

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

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

"At first it was a shock, observing the initial frogs in the region," says Larrea Saltos, who started noticing their abundance about three years ago when one leaped on her hand as she was stepping out of her front door.

Environmental Consequences Remains Unclear

The noise isn't the fundamental problem, though. While the species has been in the Galápagos for almost 30 years, scientists still know limited information about its impact on the archipelago's precariously balanced terrestrial and aquatic environments.

On archipelagos, it is very typical for non-native organisms to prosper, as they have none of their natural predators. The islands counts 1,645 invasive species, many of which are significantly affecting the safety of its native ones.

A recent study indicates the invasive frogs are voracious insect consumers, and might be unevenly consuming rare bugs found only on the archipelago, or depleting the food sources of the islands' rare avian species, affecting the food chain.

Unusual Traits and Control Challenges

The island amphibians have shown some atypical characteristics, including living in slightly salty 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 witnessed one which remained as a tadpole in her laboratory for half a year.

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

Methods to control the frogs in the beginning of the century were largely ineffective. Conservation officers tried capturing large numbers by manual methods and slowly raising the salinity of ponds in vain.

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

Without answers to more of the basic issues about their lifestyle and impact, removing the amphibians might not even be the correct way to proceed, says the biologist.

Funding Challenges for Study

While she expects the growing use of environmental DNA techniques and DNA analysis will help her group understand of the invader, funding for the research has been hard to come by.

"Everybody 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 manage."