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On her regular commute to the scientific station, biologist the researcher stoops near a shallow water body surrounded by dense plants and collects a small green sound recorder.

She had placed there through the night to record the distinctive croaks of the Scinax quinquefasciatus, recognized by local scientists as an non-native species with consequences that scientists are starting to comprehend.

Despite abounding with remarkable wildlife – such as ancient large turtles, swimming iguanas, and the well-known birds that sparked Darwin's evolutionary theory – the Galápagos archipelago off the coast of Ecuador had historically been devoid of amphibians.

In the late 1990s, this changed. Some tiny amphibians made their way from continental Ecuador to the archipelago, probably as stowaways on transport vessels.

DNA research suggest that, through time, there have been multiple unintentional arrivals to the islands, and the frogs now have a strong presence on several islands: Isabela and Santa Cruz.

The numbers is expanding so rapidly that scientists have been struggling to monitor, calculating populations in the hundreds of thousands on every island, across urban and farming areas, but also in the conservation Galápagos national park.

When San José marked amphibians and attempted to find them in the following 10 days, she could find just one tagged frog from time to time, suggesting their numbers were enormous.

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

Acoustic Chaos and Rising Worries

The amphibians' abundance is evident from the sound chaos they cause. "The amount of frogs and the sound – it's truly insane," says San José.

For the researchers, their nocturnal mating calls are useful in determining their presence in remote areas, using audio devices like the one outside San José's office.

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

"In the rainy period, I regularly hear their croaks 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 the farmer, who started noticing their abundance about three years ago when one leaped on her palm as she was walking out of her front door.

Ecological Impact Stays Unknown

The noise isn't the primary problem, though. While the amphibians has been in the islands for almost three decades, scientists still know limited information about its impact on the archipelago's precariously balanced terrestrial and aquatic environments.

On islands, it is very typical for non-native organisms to prosper, as they have few of their enemies. The islands has over sixteen hundred introduced types, many of which are significantly disrupting the survival of its endemic ones.

A 2020 study suggests the non-native amphibians are hungry insect consumers, and might be disproportionately consuming rare bugs found only on the islands, or depleting the nutrition of the region's rare birds, disrupting the ecosystem balance.

Unique Characteristics and Management Difficulties

The island amphibians have exhibited some unusual characteristics, including living in slightly salty water, which is uncommon for amphibians.

Their development stage is also highly variable, with some tadpoles turning into frogs very rapidly and others taking a long time: the researcher witnessed one which remained as a larva in her lab for half a year.

"We really don't know this part," she says, concerned the tadpoles could be impacting the islands' clean water, a very scarce resource in the islands.

Techniques to curb the amphibians in the beginning of the century were largely ineffective. Conservation officers tried capturing significant quantities by manual methods and gradually increasing the salt content of lagoons in vain.

Studies suggests spraying caffeine – which is extremely toxic to frogs – or using electrocution could help, but these approaches aren't necessarily safe for other rare Galápagos species.

Lacking solutions to more of the fundamental questions about their lifestyle and effect, removing the frogs might not even be the correct way to proceed, says the biologist.

Funding Challenges for Study

While she hopes the increasing use of eDNA methods and DNA examination will help her team understand of the invasive species, funding for the project has been difficult to come by.

"Everybody wants to give funding for protecting frogs," says the researcher. "But it's harder to find financial backing for an introduced frog that you might want to manage."