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During her daily commute to the research facility, biologist the researcher crouches near a small water body covered by dense plants and retrieves a small plastic audio device.

She had placed there overnight to record the characteristic croaks of the Fowler's snouted treefrog, known by Galápagos researchers as an non-native threat with consequences that experts are just beginning to comprehend.

Despite abounding with remarkable animals – including centuries-old large turtles, swimming lizards, and the famous birds that inspired Darwin's theory of evolution – the Galápagos archipelago off the shoreline of Ecuador had long remained free of amphibians.

In the late 1990s, this shifted. Some tiny tree frogs made their way from mainland the mainland to the islands, likely as hitchhikers on transport vessels.

Genetic studies indicate that, over the years, there have been multiple accidental introductions to the islands, and the amphibians now have a firm foothold on several islands: multiple locations.

The numbers is expanding so quickly that researchers have been finding it difficult to keep track, calculating numbers in the millions on each island, across urban and farming areas, but also in the conservation natural reserve.

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

They calculated six thousand frogs in a solitary pond. "Our estimates are still very low," states the researcher. "I'm pretty sure there are additional numbers."

Deafening Noise and Growing Concerns

The amphibians' proliferation is clear from the sound disruption they create. "The amount of frogs and the noise – it's really incredible," says San José.

For the researchers, their nightly mating calls are helpful in estimating their existence in remote areas, using audio devices like the one near San José's workplace.

But nearby farmers say the sounds are so loud they keep them up at night.

"In the rainy period, I constantly hear their croaks and they're really loud," says Jadira Larrea Saltos from Santa Cruz.

"Initially it was a shock, observing the first frogs in the region," says the farmer, who started observing their abundance about three years ago when one jumped on her palm as she was walking out of her front door.

Environmental Consequences Remains Unknown

The noise isn't the primary problem, however. While the species has been in the Galápagos for almost three decades, experts still know very little about its impact on the islands' delicately balanced terrestrial and aquatic ecosystems.

On islands, it is very typical for non-native species to thrive, as they have none of their enemies. The Galápagos has over sixteen hundred invasive types, many of which are significantly affecting the safety of its endemic ones.

A recent study indicates the invasive frogs are hungry insect consumers, and might be disproportionately consuming uncommon bugs found exclusively on the islands, or reducing the food sources of the region's uncommon birds, disrupting the ecosystem balance.

Unusual Traits and Management Difficulties

The Galápagos frogs have shown some unusual characteristics, including surviving in brackish water, which is rare for amphibians.

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

"We truly don't know this aspect," she says, concerned the larvae could be affecting the region's freshwater, a very scarce commodity in the islands.

Methods to control the frogs in the beginning of the century were mostly unsuccessful. Conservation officers tried collecting significant quantities by hand and slowly raising the salt content of ponds in vain.

Research suggests spraying coffee – which is highly toxic to amphibians – or using electrical methods could assist, but these methods aren't necessarily secure for other uncommon island organisms.

Lacking answers to more of the basic questions about their biology and effect, removing the amphibians might not even be the correct way to advance, says San José.

Funding Challenges for Study

While she hopes the growing use of eDNA methods and genetic analysis will assist her team understand of the invasive species, funding for the research has been hard to obtain.

"Everybody wants to give support for protecting frogs," says San José. "But it's more difficult to find funding for an invasive frog that you might want to control."