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During her regular commute to the scientific station, biologist the researcher stoops near a shallow water body covered by dense plants and collects a small plastic audio recorder.

The device was left there overnight to record the distinctive calls of the Scinax quinquefasciatus, recognized by local scientists as an invasive threat with consequences that experts are just beginning to comprehend.

Despite abounding with remarkable wildlife – including ancient giant tortoises, marine lizards, and the famous finches that inspired Darwin's evolutionary theory – the island chain near the shoreline of Ecuador had historically been devoid of amphibians.

In the late 1990s, this shifted. Some small amphibians traveled from mainland the mainland to the archipelago, likely as hitchhikers on cargo ships.

Genetic studies suggest that, over the years, there have been multiple accidental arrivals to the islands, and the amphibians now have a strong presence on several locations: Isabela and Santa Cruz.

The population is growing so quickly that scientists have been struggling to keep track, calculating populations in the millions on each island, across urban and farming areas, but also in the protected natural reserve.

When the biologist marked frogs and attempted to find them in the subsequent 10 days, she could locate just one marked frog from time to time, suggesting their populations were massive.

They calculated six thousand frogs in a single pond. "Our estimates are still very low," states the researcher. "I am quite certain there are additional numbers."

Acoustic Chaos and Growing Concerns

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

For the scientists, their nocturnal mating calls are useful in estimating their presence in remote areas, using recorders like the one near the office.

But local agricultural workers say the sounds are so raucous they prevent sleep at night.

"During the rainy period, I constantly hear their calls 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 region," says Larrea Saltos, who started noticing their large numbers about three years ago when one jumped on her hand as she was stepping out of her house.

Environmental Consequences Stays Unclear

The noise isn't the primary problem, though. While the amphibians has been in the islands for nearly 30 years, scientists still know very little about its effect on the islands' precariously balanced terrestrial and aquatic environments.

On archipelagos, it is very typical for non-native organisms to thrive, as they have none of their natural predators. The Galápagos has over sixteen hundred introduced types, many of which are significantly affecting the survival of its native ones.

A 2020 research indicates the invasive frogs are voracious insect consumers, and might be disproportionately consuming uncommon bugs found only on the islands, or reducing the nutrition of the region's rare birds, affecting the ecosystem balance.

Unusual Traits and Management Difficulties

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

Their development process is also extremely inconsistent, with some larvae turning into frogs very rapidly and others taking a long time: the researcher observed one which remained as a tadpole in her laboratory for half a year.

"We really don't know this aspect," she says, worried the larvae could be impacting the region's clean water, a very scarce commodity in the islands.

Techniques to control the frogs in the beginning of the century were mostly ineffective. Park rangers tried collecting large numbers by manual methods and slowly increasing the salt content of lagoons in vain.

Research suggests applying coffee – which is extremely toxic to frogs – or using electrical methods could assist, but these methods aren't necessarily safe for other uncommon island organisms.

Without solutions to more of the basic questions about their lifestyle and effect, culling the frogs might not even be the correct way to advance, says San José.

Financial Obstacles for Research

While she expects the growing use of environmental DNA methods and DNA analysis will help her group understand of the invader, financial support for the project has been hard to obtain.

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