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On her regular commute to the research facility, scientist the researcher crouches near a small pond surrounded by thick plants and retrieves a small green sound recorder.

The device was left there overnight to record the characteristic calls of the Scinax quinquefasciatus, known by Galápagos researchers as an non-native species with effects that experts are just beginning to comprehend.

Although teeming with remarkable wildlife – including ancient large turtles, marine lizards, and the well-known finches that inspired Darwin's theory of evolution – the island chain near the coast of Ecuador had long remained devoid of frogs and toads.

During the 1990s, this shifted. Several tiny tree frogs traveled from mainland the mainland to the islands, probably as stowaways on transport vessels.

DNA research indicate that, over the years, there have been multiple accidental arrivals to the archipelago, and the amphibians now have a firm presence on two islands: Isabela and Santa Cruz.

The numbers is growing so rapidly that scientists have been struggling to keep track, calculating numbers in the millions on each island, across urban and farming areas, but also in the protected Galápagos national park.

When the biologist tagged frogs and attempted to recapture them in the following 10 days, she could locate just one marked frog from time to time, indicating their numbers were massive.

They estimated 6,000 frogs in a single pond. "The calculations are still very conservative," states San José. "I am quite certain there are even more."

Deafening Noise and Growing Concerns

The frogs' abundance is clear from the sound chaos they create. "The amount of frogs and the noise – it's truly incredible," comments San José.

For the scientists, their nocturnal mating calls are useful in estimating their existence in far-flung areas, using audio devices like the one outside San José's office.

But nearby farmers say the sounds are so loud they prevent sleep at night.

"During the rainy period, I regularly hear their croaks and they're really loud," says a local coffee farmer from Santa Cruz.

"At first it was a surprise, observing the first frogs in the area," says Larrea Saltos, who started observing their large numbers about several years ago when one leaped on her palm as she was walking out of her house.

Environmental Consequences Stays Unknown

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

On islands, it is very common for non-native species to prosper, as they have none of their enemies. The islands has 1,645 invasive types, many of which are seriously disrupting the safety of its native ones.

A 2020 research indicates the non-native frogs are hungry bug eaters, and might be disproportionately consuming rare bugs found only on the archipelago, or reducing the nutrition of the islands' rare birds, disrupting the ecosystem balance.

Unusual Traits and Control Challenges

The Galápagos amphibians have shown some atypical characteristics, including living in brackish water, which is uncommon for amphibians.

Their development process is also extremely inconsistent, with some larvae becoming frogs very quickly and others taking a long time: San José observed one which stayed as a larva in her lab for six months.

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

Methods to control the amphibians in the beginning of the century were largely ineffective. Conservation officers tried collecting significant quantities by manual methods and slowly raising the salt content of lagoons in without success.

Research suggests applying coffee – which is extremely poisonous to amphibians – or using electrocution could assist, but these approaches aren't necessarily safe for other rare Galápagos species.

Lacking answers to more of the basic issues about their lifestyle and impact, culling the amphibians might not even be the correct way to proceed, says the biologist.

Funding Challenges for Study

While she hopes the growing use of environmental DNA methods and genetic examination will help her team make sense of the invasive species, funding for the research has been hard to come by.

"Everybody wants to give support for protecting frogs," says the researcher. "But it's more difficult to find financial backing for an invasive frog that you might want to control."