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On her daily commute to the research facility, scientist Miriam San José crouches near a small water body surrounded by thick plants and retrieves a small green sound device.

She had placed there overnight to capture the characteristic calls of the Fowler's snouted treefrog, known by Galápagos researchers as an non-native species with effects that scientists are just beginning to understand.

Although abounding with remarkable animals – such as ancient giant tortoises, swimming iguanas, and the famous finches that sparked Charles Darwin's theory of evolution – the island chain off the shoreline of South America had long remained devoid of amphibians.

In the late 1990s, this shifted. Several small tree frogs made their way from mainland Ecuador to the archipelago, probably as stowaways on cargo ships.

Genetic research suggest that, through time, there have been repeated accidental introductions to the islands, and the amphibians now have a strong foothold on several locations: Isabela and Santa Cruz.

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

When the biologist tagged frogs and attempted to recapture them in the subsequent 10 days, she could find only a single tagged frog from time to time, suggesting their populations were massive.

They calculated six thousand frogs in a solitary pond. "Our estimates are still very low," states San José. "I'm pretty sure there are additional numbers."

Acoustic Chaos and Growing Concerns

The frogs' proliferation is evident from the acoustic disruption they cause. "The amount of frogs and the noise – it's truly insane," comments San José.

For the scientists, their nightly mating calls are useful in determining their presence in remote areas, using recorders like the one near the office.

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

"In the rainy period, I constantly hear their calls and they're extremely loud," says a local coffee farmer from Santa Cruz.

"At first it was a surprise, observing the first frogs in the region," says the farmer, who started observing their large numbers about three years ago when one leaped on her palm as she was walking out of her house.

Ecological Impact Stays Unknown

The sound isn't the primary problem, however. While the amphibians has been in the Galápagos for nearly 30 years, experts still know limited information about its impact on the archipelago's precariously balanced land and water environments.

On archipelagos, it is very typical for non-native organisms to thrive, as they have few of their enemies. The islands has over sixteen hundred introduced species, many of which are seriously disrupting the safety of its native ones.

A recent research suggests the invasive amphibians are voracious insect eaters, and might be unevenly eating rare bugs found exclusively on the archipelago, or reducing the food sources of the islands' uncommon birds, affecting the ecosystem balance.

Unusual Traits and Control Challenges

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

Their development process is also highly inconsistent, with some larvae turning into frogs very quickly and others taking a extended period: the researcher witnessed one which remained 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 clean water, a very scarce resource in the islands.

Techniques to curb the frogs in the beginning of the century were mostly unsuccessful. Park rangers tried collecting large numbers by hand and slowly raising the salinity of lagoons in vain.

Research suggests spraying caffeine – which is extremely toxic to amphibians – or using electrical methods could help, but these methods aren't always secure for other uncommon Galápagos organisms.

Without answers to more of the basic questions about their biology and effect, removing the amphibians might not even be the correct way to proceed, says the biologist.

Funding Challenges for Research

While she expects the increasing use of eDNA techniques and genetic analysis will help her team make sense of the invasive species, funding for the research has been difficult to obtain.

"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."