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On her daily commute to the scientific station, biologist the researcher stoops near a small pond covered by thick vegetation and collects a small plastic sound recorder.

She had placed there through the night to record the characteristic calls of the Scinax quinquefasciatus, recognized by local researchers as an non-native threat with consequences that scientists are just beginning to understand.

Although abounding with unique wildlife – such as ancient large turtles, swimming lizards, and the well-known birds that inspired Charles Darwin's theory of evolution – the island chain off the shoreline of Ecuador had long remained devoid 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, through time, there have been multiple unintentional introductions to the archipelago, and the frogs now have a firm presence on several locations: multiple locations.

The population is growing so quickly that researchers have been struggling to keep track, calculating numbers in the hundreds of thousands on each island, across developed and farming areas, but also in the conservation natural reserve.

When San José marked frogs and attempted to recapture them in the subsequent week and a half, she could find only a single marked 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 the researcher. "I am pretty sure there are even more."

Deafening Noise and Rising Worries

The amphibians' proliferation is clear from the acoustic disruption they create. "The number of frogs and the sound – it's really incredible," says the scientist.

For the scientists, their nocturnal mating calls are helpful in estimating their existence in remote areas, using recorders like the one outside San José's office.

But local agricultural workers say the sounds are so raucous they keep them up at night.

"In the wet season, I constantly hear their croaks and they're extremely loud," says a local coffee farmer from the island.

"At first it was a surprise, observing the initial frogs in the area," says Larrea Saltos, who started observing their large numbers about three years ago when one jumped on her hand as she was walking out of her front door.

Ecological Impact Remains Unclear

The noise isn't the fundamental problem, though. While the amphibians has been in the islands for nearly three decades, scientists still know limited information about its impact on the islands' delicately balanced land and water ecosystems.

On archipelagos, it is very typical for non-native organisms to thrive, as they have none of their enemies. The islands has 1,645 invasive species, many of which are seriously disrupting the survival of its endemic ones.

A 2020 research suggests the invasive amphibians are hungry bug consumers, and might be unevenly eating uncommon bugs found only on the islands, or reducing the food sources of the islands' uncommon birds, disrupting the food chain.

Unusual Traits and Management Difficulties

The Galápagos frogs have shown some atypical traits, including surviving in slightly salty water, which is rare for frogs.

Their metamorphosis process is also highly inconsistent, with some tadpoles becoming frogs very rapidly and others taking a long time: San José observed one which stayed as a tadpole in her laboratory for six months.

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

Techniques to curb the amphibians in the beginning of the century were largely ineffective. Park rangers tried collecting large numbers by hand and slowly raising the salinity of lagoons in without success.

Studies suggests applying caffeine – which is extremely poisonous to frogs – or using electrical methods could help, but these approaches aren't necessarily safe for other rare Galápagos organisms.

Without answers to more of the basic issues about their biology and effect, culling the amphibians might not even be the correct way to proceed, says San José.

Funding Challenges for Study

While she hopes the increasing use of eDNA methods and DNA analysis will assist her group make sense of the invasive species, financial support for the project has been difficult to obtain.

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