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On her regular commute to the scientific station, scientist the researcher crouches near a small water body covered by dense vegetation and collects a compact plastic audio recorder.

The device was left there overnight 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 unique wildlife – such as centuries-old large turtles, swimming iguanas, and the well-known birds that inspired Charles Darwin's evolutionary theory – the island chain off the shoreline of Ecuador had long remained devoid of frogs and toads.

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

Genetic studies indicate that, over the years, there have been multiple accidental arrivals to the islands, and the frogs now have a strong foothold on two islands: Isabela and Santa Cruz.

The numbers is growing so rapidly that researchers have been struggling to monitor, estimating populations in the millions on every island, across developed and farming areas, but also in the conservation natural reserve.

When the biologist tagged frogs and attempted to recapture them in the following week and a half, she could locate only a single tagged frog from time to time, suggesting their numbers were massive.

They calculated 6,000 frogs in a single pond. "The calculations are still very conservative," says San José. "I am quite certain there are additional numbers."

Deafening Noise and Growing Concerns

The amphibians' abundance is evident from the acoustic disruption they cause. "The number of frogs and the noise – it's truly insane," comments the scientist.

For the scientists, their nocturnal vocalizations are useful in estimating their existence in far-flung areas, using recorders like the one outside the office.

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

"During the wet season, I regularly hear their croaks and they're really loud," says Jadira Larrea Saltos from Santa Cruz.

"Initially it was a surprise, seeing the initial frogs in the area," says Larrea Saltos, who started noticing their abundance about several years ago when one leaped on her palm as she was stepping out of her house.

Environmental Consequences Stays Unknown

The noise isn't the fundamental problem, however. While the amphibians has been in the Galápagos for nearly 30 years, experts still know limited information about its effect on the islands' precariously balanced land and water environments.

On islands, it is very typical for non-native species to prosper, as they have none of their natural predators. The islands counts over sixteen hundred invasive types, many of which are seriously affecting the survival of its native ones.

A 2020 study suggests the non-native frogs are voracious bug eaters, and might be unevenly eating uncommon bugs found exclusively on the archipelago, or depleting the food sources of the islands' uncommon birds, disrupting the ecosystem balance.

Unique Characteristics and Management Difficulties

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

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

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

Methods to curb the frogs in the beginning of the century were mostly unsuccessful. Conservation officers tried collecting large numbers by manual methods and slowly increasing the salinity of lagoons in vain.

Research indicates applying caffeine – which is extremely toxic to frogs – or using electrocution could assist, but these approaches aren't always secure for other rare Galápagos organisms.

Lacking solutions to more of the basic questions about their biology and effect, culling the amphibians might not even be the correct way to proceed, says the biologist.

Financial Obstacles for Study

While she expects the increasing use of environmental DNA techniques and DNA analysis will assist her group make sense of the invasive species, funding for the project has been hard to obtain.

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