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On her daily commute to the research facility, scientist Miriam San José stoops near a shallow pond surrounded by dense plants and collects a small green sound device.

She had placed there through the night to record the distinctive calls of the Scinax quinquefasciatus, known by local researchers as an invasive threat with consequences that experts are just beginning to understand.

Despite abounding with unique animals – including centuries-old giant tortoises, swimming iguanas, and the well-known birds that inspired Charles Darwin's theory of evolution – the island chain near the coast of Ecuador had historically been devoid of frogs and toads.

In the late 1990s, this changed. Some small tree frogs made their way from mainland Ecuador to the islands, likely as stowaways on transport vessels.

DNA studies suggest that, over the years, there have been repeated unintentional introductions to the archipelago, and the amphibians now have a strong foothold on several islands: multiple locations.

The numbers is growing so rapidly that researchers have been struggling to monitor, estimating populations in the millions on each island, across urban and farming areas, but also in the protected Galápagos national park.

When the biologist marked amphibians and attempted to find them in the following week and a half, she could locate just one marked frog occasionally, suggesting their numbers were massive.

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

Acoustic Chaos and Growing Concerns

The frogs' abundance is evident from the sound chaos they cause. "The amount of frogs and the sound – it's really incredible," comments San José.

For the scientists, their nocturnal vocalizations are useful in determining their existence in remote areas, using audio devices like the one near the office.

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

"During the rainy period, I constantly hear their croaks and they're extremely loud," says Jadira Larrea Saltos from Santa Cruz.

"Initially it was a surprise, seeing the first frogs in the area," says the farmer, who started noticing their large numbers about several years ago when one jumped on her hand as she was stepping out of her front door.

Ecological Impact Remains Unknown

The sound isn't the primary problem, though. While the amphibians has been in the islands for almost three decades, scientists still know very little about its impact on the archipelago's delicately balanced land and water ecosystems.

On archipelagos, it is very typical for invasive organisms to thrive, as they have few of their enemies. The islands counts 1,645 introduced types, many of which are significantly disrupting the safety of its native ones.

A recent study indicates the invasive amphibians are hungry insect eaters, and might be unevenly consuming uncommon insects found exclusively on the islands, or reducing the food sources of the islands' rare avian species, disrupting the food chain.

Unique Characteristics and Management Difficulties

The Galápagos frogs have exhibited some atypical characteristics, including living in brackish water, which is rare for amphibians.

Their development process is also extremely variable, with some larvae becoming frogs very rapidly and others taking a long time: the researcher witnessed one which remained as a larva in her lab for six months.

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

Methods to control the frogs in the early 2000s were mostly unsuccessful. Conservation officers tried capturing large numbers by hand and slowly increasing the salt content of ponds in without success.

Studies suggests applying coffee – which is extremely toxic to amphibians – or using electrocution could help, but these methods aren't always secure for other rare island species.

Without answers to more of the basic issues about their biology and impact, removing the amphibians might not even be the right way to advance, says the biologist.

Funding Challenges for Study

While she hopes the growing use of eDNA methods and DNA examination will assist her team make sense of the invasive species, financial support for the project has been difficult to obtain.

"Everybody wants to give support for protecting frogs," says San José. "But it's harder to find financial backing for an invasive frog that you might want to manage."