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On her regular commute to the research facility, biologist the researcher stoops near a small water body covered by dense plants and collects a small plastic sound recorder.

She had placed there through the night to record the characteristic calls of the Fowler's snouted treefrog, recognized by Galápagos scientists as an invasive threat with effects that experts are just beginning to understand.

Although teeming with remarkable animals – including ancient large turtles, swimming lizards, and the famous finches that sparked Charles Darwin's theory of evolution – the island chain near the shoreline of South America had long remained free of frogs and toads.

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

DNA research suggest that, through time, there have been repeated accidental arrivals to the archipelago, and the amphibians now have a firm presence on two locations: multiple locations.

The population is growing so rapidly that scientists have been struggling to monitor, estimating numbers 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 find them in the following week and a half, she could find only a single tagged frog from time to time, suggesting their populations were massive.

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

Acoustic Chaos and Rising Worries

The amphibians' abundance is evident from the sound chaos they cause. "The number of frogs and the sound – it's truly insane," comments the scientist.

For the researchers, their nocturnal vocalizations are useful in estimating their existence in far-flung areas, using audio devices like the one outside San José's workplace.

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

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

"Initially it was a surprise, seeing the first frogs in the region," says Larrea Saltos, who started observing their large numbers about three years ago when one jumped on her hand as she was stepping out of her house.

Environmental Consequences Stays Unknown

The sound isn't the fundamental problem, however. While the amphibians has been in the Galápagos for nearly 30 years, experts still know very little about its effect on the islands' delicately balanced terrestrial and aquatic environments.

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

A recent study suggests the invasive amphibians are voracious bug eaters, and might be disproportionately eating rare bugs found exclusively on the archipelago, or depleting the nutrition of the region's uncommon avian species, affecting the ecosystem balance.

Unique Characteristics and Control Challenges

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

Their metamorphosis stage is also extremely inconsistent, with some larvae becoming frogs very quickly and others taking a extended period: the researcher observed one which remained as a larva in her lab for six months.

"We truly don't know this part," she says, worried the larvae could be impacting the region's freshwater, a very limited commodity in Galápagos.

Methods to curb the amphibians in the early 2000s were mostly ineffective. Conservation officers tried capturing significant quantities by hand and slowly raising the salt content of lagoons in without success.

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

Without solutions to more of the basic questions about their lifestyle and impact, removing the frogs might not even be the correct way to advance, says the biologist.

Financial Obstacles for Study

While she expects the growing use of eDNA techniques and DNA analysis will assist her group understand of the invasive species, funding for the project has been difficult to come by.

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