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During her daily walk to the research facility, biologist Miriam San José stoops near a shallow pond surrounded by thick vegetation and collects a small green audio device.

She had placed there through the night to capture the distinctive calls of the Fowler's snouted treefrog, known by local scientists as an non-native threat with consequences that experts are starting to understand.

Despite teeming with unique wildlife – such as ancient large turtles, swimming lizards, and the well-known birds that sparked Charles Darwin's evolutionary theory – the island chain off the coast of Ecuador had long remained free of frogs and toads.

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

Genetic research suggest that, over the years, there have been multiple accidental introductions to the archipelago, and the amphibians now have a firm presence on several islands: Isabela and Santa Cruz.

The population is expanding so rapidly that researchers have been struggling to keep track, calculating populations in the hundreds of thousands on every island, across urban and farming areas, but also in the conservation natural reserve.

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

They calculated six thousand frogs in a solitary pond. "Our estimates are still very conservative," states San José. "I'm pretty sure there are even more."

Deafening Noise and Rising Worries

The amphibians' proliferation is evident from the acoustic disruption they cause. "The amount of frogs and the sound – it's truly insane," comments San José.

For the scientists, their nightly vocalizations are useful in determining their existence in far-flung areas, using audio devices like the one outside the office.

But nearby farmers say the sounds are so loud they keep them up 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, seeing the first frogs in the area," says the farmer, who started noticing their abundance about several years ago when one leaped on her palm as she was walking out of her house.

Environmental Consequences Stays Unknown

The sound isn't the primary problem, though. While the species has been in the islands for almost three decades, scientists still know very little about its impact on the archipelago's precariously balanced terrestrial and aquatic ecosystems.

On islands, it is very common for non-native organisms to prosper, as they have none of their enemies. The Galápagos counts over sixteen hundred introduced types, many of which are significantly disrupting the survival of its native ones.

A 2020 study suggests the invasive frogs are voracious bug consumers, and might be unevenly eating rare bugs found only on the archipelago, or depleting the food sources of the islands' rare avian species, affecting the ecosystem balance.

Unusual Traits and Management Difficulties

The Galápagos frogs have exhibited some atypical characteristics, including surviving in slightly salty water, which is rare for amphibians.

Their development process is also highly variable, with some tadpoles turning into frogs very quickly and others taking a long time: San José observed one which remained as a larva in her laboratory for six months.

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

Techniques to control the amphibians in the beginning of the century were largely ineffective. Park rangers tried collecting significant quantities by hand and gradually increasing the salinity of ponds in vain.

Research indicates applying caffeine – which is highly toxic to frogs – or using electrocution could assist, but these approaches aren't always secure for other uncommon island species.

Lacking answers to more of the basic questions about their biology and impact, culling the frogs might not even be the right way to proceed, says San José.

Funding Challenges for Study

While she expects the growing use of eDNA techniques and genetic examination will help her team make sense of the invasive species, financial support for the research has been hard to obtain.

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