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During her daily commute to the research facility, biologist the researcher crouches near a shallow water body surrounded by thick plants and collects a small plastic sound recorder.

She had placed there overnight to record the characteristic calls of the Scinax quinquefasciatus, known by local scientists as an non-native species with effects that scientists are starting to comprehend.

Although teeming with unique wildlife – such as centuries-old large turtles, swimming iguanas, and the famous birds that sparked Darwin's theory of evolution – the Galápagos archipelago near the shoreline of South America had historically been free of amphibians.

During the 1990s, this shifted. Several small amphibians traveled from continental the mainland to the archipelago, probably as stowaways on transport vessels.

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

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

When San José tagged frogs and attempted to recapture them in the subsequent 10 days, she could locate just one marked frog occasionally, indicating their populations were enormous.

They calculated six thousand frogs in a solitary pond. "The calculations are still very conservative," states the researcher. "I'm pretty sure there are even more."

Deafening Noise and Growing Concerns

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

For the scientists, their nocturnal mating calls are helpful in determining their presence in remote areas, using recorders like the one outside the office.

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

"During the wet season, I constantly hear their croaks and they're extremely loud," says a local coffee farmer from the island.

"At first it was a surprise, seeing the initial frogs in the region," says the farmer, who started observing their abundance about several years ago when one leaped on her hand as she was walking out of her front door.

Ecological Impact Stays Unknown

The sound isn't the primary problem, though. While the species has been in the islands for almost three decades, scientists still know very little about its effect on the islands' delicately balanced terrestrial and aquatic ecosystems.

On archipelagos, it is very typical for invasive species to prosper, as they have few of their enemies. The islands has 1,645 introduced types, many of which are significantly affecting the survival of its endemic ones.

A recent study indicates the invasive amphibians are voracious insect eaters, and might be unevenly eating rare insects found only on the islands, or depleting the food sources of the islands' rare birds, disrupting the food chain.

Unique Characteristics and Management Difficulties

The island frogs have shown some atypical traits, including surviving in brackish water, which is uncommon for amphibians.

Their development stage is also extremely inconsistent, with some larvae becoming frogs very quickly and others taking a extended period: San José witnessed one which remained as a larva in her laboratory for half a year.

"We truly don't know this part," she says, worried the larvae could be affecting the region's clean water, a very scarce resource in Galápagos.

Methods to curb the frogs in the early 2000s were mostly unsuccessful. Conservation officers tried capturing large numbers by manual methods and gradually increasing the salt content of lagoons in without success.

Studies suggests applying coffee – which is highly poisonous to amphibians – or using electrical methods could help, but these approaches aren't necessarily safe for other uncommon Galápagos organisms.

Without solutions to more of the fundamental questions about their biology and effect, removing the amphibians might not even be the correct way to proceed, says San José.

Financial Obstacles for Study

While she hopes the growing use of eDNA techniques and DNA analysis will help her team understand of the invasive species, funding for the project has been difficult to obtain.

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