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During her regular commute to the research facility, scientist the researcher crouches near a shallow water body surrounded by thick plants and collects a compact plastic sound device.

She had placed there through the night to record the characteristic calls of the Scinax quinquefasciatus, known by local scientists as an non-native threat with consequences that experts are just beginning to understand.

Despite abounding with unique wildlife – including centuries-old large turtles, swimming lizards, and the famous birds that sparked Darwin's theory of evolution – the island chain near the shoreline of South America had long remained devoid of amphibians.

In the late 1990s, this shifted. Several tiny tree frogs traveled from mainland the mainland to the archipelago, likely as stowaways on cargo ships.

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

The numbers is growing so rapidly that researchers have been finding it difficult to keep track, estimating numbers in the hundreds of thousands on each island, across developed and farming areas, but also in the conservation Galápagos national park.

When the biologist marked frogs and attempted to recapture them in the subsequent week and a half, she could find only a single tagged frog occasionally, suggesting their populations were massive.

They calculated six thousand frogs in a single pond. "Our estimates are still very low," says San José. "I am pretty sure there are even more."

Deafening Noise and Growing Concerns

The amphibians' abundance is clear from the acoustic chaos they cause. "The amount of frogs and the noise – it's truly incredible," says San José.

For the scientists, their nightly mating calls are helpful in estimating their existence in far-flung areas, using recorders like the one outside San José's workplace.

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

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

"Initially it was a shock, observing the initial frogs in the area," says the farmer, who started observing their abundance about three years ago when one leaped on her palm as she was walking out of her front door.

Ecological Impact Remains Unclear

The sound isn't the primary problem, though. While the species has been in the Galápagos for nearly 30 years, experts still know very little about its effect on the archipelago's delicately balanced land and water environments.

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

A 2020 research indicates the invasive amphibians are hungry insect eaters, and might be disproportionately consuming uncommon bugs found exclusively on the islands, or depleting the nutrition of the region's rare avian species, affecting the food chain.

Unique Characteristics and Control Challenges

The island amphibians have exhibited some atypical characteristics, including surviving in slightly salty water, which is rare for amphibians.

Their metamorphosis process is also extremely variable, with some larvae turning into frogs very quickly and others taking a long time: the researcher witnessed one which stayed as a larva in her lab for six months.

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

Techniques to control the frogs in the beginning of the century were mostly ineffective. Conservation officers tried capturing significant quantities by manual methods and slowly raising the salinity of ponds in vain.

Research indicates applying coffee – which is extremely poisonous to frogs – or using electrocution could help, but these methods aren't necessarily secure for other rare island organisms.

Without solutions to more of the basic issues about their biology and effect, removing the frogs might not even be the right way to proceed, says San José.

Funding Challenges for Study

While she expects the growing use of environmental DNA methods and DNA examination will assist her team understand of the invader, funding for the research has been difficult to come by.

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