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During her regular commute to the research facility, scientist the researcher crouches near a shallow pond covered by dense vegetation and collects a small green sound device.

The device was left there through the night to record the characteristic croaks of the Scinax quinquefasciatus, known by local scientists as an invasive threat with effects that experts are starting to comprehend.

Despite teeming with unique wildlife – including ancient large turtles, swimming iguanas, and the famous finches that inspired Darwin's theory of evolution – the island chain near the shoreline of South America had long remained free of frogs and toads.

In the late 1990s, this shifted. Several tiny amphibians traveled from mainland the mainland to the islands, likely as hitchhikers on cargo ships.

DNA research suggest 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 quickly that researchers have been finding it difficult to monitor, estimating numbers in the millions on each island, across urban and farming areas, but also in the conservation Galápagos national park.

When San José tagged amphibians and attempted to recapture them in the subsequent 10 days, she could locate just one tagged frog from time to time, indicating their numbers were enormous.

They estimated six thousand frogs in a solitary pond. "The calculations are still very conservative," states San José. "I am pretty sure there are even more."

Acoustic Chaos and Growing Concerns

The frogs' proliferation is evident from the acoustic chaos they cause. "The amount of frogs and the noise – it's really incredible," says San José.

For the scientists, their nightly mating calls are useful in determining their existence in remote areas, using audio devices like the one near the workplace.

But local farmers say the calls are so loud they keep them up at night.

"During the rainy period, I regularly hear their calls and they're really loud," says Jadira Larrea Saltos from the island.

"At first it was a surprise, observing the initial frogs in the area," says the farmer, who started observing their abundance about three years ago when one jumped on her palm as she was stepping out of her front door.

Environmental Consequences Stays Unclear

The sound isn't the fundamental problem, however. While the species has been in the islands for almost 30 years, experts still know limited information about its impact on the islands' delicately balanced terrestrial and aquatic environments.

On islands, it is very common for non-native organisms to prosper, as they have none of their enemies. The Galápagos counts over sixteen hundred introduced types, many of which are seriously disrupting the survival of its endemic ones.

A 2020 study indicates the non-native amphibians are hungry bug consumers, and might be unevenly eating rare bugs found only on the archipelago, or depleting the food sources of the islands' rare birds, disrupting the ecosystem balance.

Unusual Traits and Management Difficulties

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

Their development process is also extremely variable, with some tadpoles turning into frogs very rapidly and others taking a extended period: the researcher observed one which stayed as a larva in her laboratory for half a year.

"We really don't know this part," she says, worried the tadpoles could be affecting the region's freshwater, a very limited resource in the islands.

Methods to curb the amphibians in the early 2000s were largely unsuccessful. Park rangers tried capturing significant quantities by manual methods and gradually raising the salinity of lagoons in vain.

Studies indicates spraying caffeine – which is extremely poisonous to frogs – or using electrocution could help, but these approaches aren't necessarily secure for other uncommon island species.

Lacking answers to more of the fundamental issues about their biology and impact, culling the amphibians might not even be the correct way to advance, says the biologist.

Financial Obstacles for Study

While she expects the increasing use of environmental DNA methods and genetic analysis will help her group understand of the invader, financial support for the research has been hard to come by.

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