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During her daily commute to the research facility, scientist Miriam San José stoops near a small pond surrounded by dense plants and collects a compact green audio recorder.

The device was left there through the night to record the characteristic croaks of the Fowler's snouted treefrog, known by local researchers as an non-native threat with consequences that scientists are starting to comprehend.

Although teeming with unique animals – including centuries-old giant tortoises, swimming lizards, and the well-known finches that inspired Darwin's evolutionary theory – the island chain near the coast of South America had long remained devoid of amphibians.

During the 1990s, this shifted. Several tiny amphibians traveled from mainland the mainland to the archipelago, probably as hitchhikers on cargo ships.

Genetic studies suggest that, over the years, there have been multiple accidental introductions to the archipelago, and the amphibians now have a firm presence on two locations: multiple locations.

The numbers is expanding so quickly that scientists have been finding it difficult to monitor, calculating numbers in the hundreds of thousands on each island, across urban and agricultural areas, but also in the conservation Galápagos national park.

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

They estimated six thousand frogs in a single pond. "Our estimates are still very conservative," states San José. "I'm pretty sure there are additional numbers."

Acoustic Chaos and Rising Worries

The frogs' proliferation is evident from the sound chaos they cause. "The number of frogs and the noise – it's truly insane," comments San José.

For the researchers, their nocturnal vocalizations are helpful in determining their existence in remote areas, using recorders like the one near the office.

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

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

"Initially it was a surprise, observing the first frogs in the area," says Larrea Saltos, who started observing their abundance about several years ago when one jumped on her palm as she was walking out of her front door.

Environmental Consequences Stays Unknown

The noise isn't the fundamental problem, however. While the species has been in the Galápagos for nearly 30 years, scientists still know limited information about its effect on the islands' precariously balanced terrestrial and aquatic ecosystems.

On islands, it is very common for non-native species to thrive, as they have few of their natural predators. The islands counts over sixteen hundred invasive species, many of which are significantly disrupting the safety of its native ones.

A 2020 research indicates the non-native frogs are hungry insect consumers, and might be disproportionately eating uncommon insects found exclusively on the archipelago, or depleting the nutrition of the region's uncommon avian species, disrupting the ecosystem balance.

Unusual Traits and Management Difficulties

The Galápagos frogs have exhibited some unusual traits, including living in slightly salty water, which is uncommon for amphibians.

Their development process is also extremely inconsistent, with some larvae becoming frogs very quickly and others taking a long time: San José 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 affecting the region's freshwater, a very scarce commodity in Galápagos.

Techniques to curb the frogs in the early 2000s were largely ineffective. Conservation officers tried capturing significant quantities by manual methods and slowly increasing the salt content of ponds in vain.

Research indicates spraying coffee – which is extremely toxic to frogs – or using electrical methods could assist, but these approaches aren't necessarily safe for other rare Galápagos species.

Lacking solutions to more of the fundamental issues about their lifestyle and impact, removing the frogs might not even be the right way to advance, says the biologist.

Financial Obstacles for Study

While she hopes the increasing use of environmental DNA methods and genetic examination will help her group make sense of the invader, financial support for the research has been difficult to obtain.

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