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During her regular commute to the research facility, scientist Miriam San José crouches near a shallow pond covered by dense vegetation and retrieves a small plastic sound device.

The device was left there overnight to record the distinctive calls of the Fowler's snouted treefrog, known by local scientists as an non-native species with consequences that experts are just beginning to understand.

Despite teeming with unique wildlife – including centuries-old giant tortoises, marine iguanas, and the famous birds that sparked Darwin's evolutionary theory – the island chain near the shoreline of South America had historically been free of amphibians.

During the 1990s, this changed. Several small tree frogs made their way from mainland Ecuador to the islands, likely as stowaways on cargo ships.

Genetic studies indicate that, through time, there have been multiple unintentional arrivals to the archipelago, and the amphibians now have a firm foothold on several locations: Isabela and Santa Cruz.

The population is growing so quickly that researchers have been finding it difficult to keep track, calculating numbers in the millions on each island, across developed and farming areas, but also in the conservation natural reserve.

When the biologist tagged amphibians and attempted to find them in the subsequent 10 days, she could find just one marked frog from time to time, suggesting their populations were massive.

They estimated six thousand frogs in a solitary pond. "The calculations are still very low," says the researcher. "I am pretty sure there are even more."

Deafening Noise and Rising Worries

The amphibians' proliferation is evident from the sound chaos they cause. "The amount of frogs and the sound – it's really insane," says the scientist.

For the researchers, their nocturnal vocalizations are useful in estimating their presence in far-flung areas, using recorders like the one outside San José's office.

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

"In the wet season, I regularly hear their croaks and they're extremely loud," says Jadira Larrea Saltos from the island.

"Initially it was a shock, observing the first frogs in the area," says Larrea Saltos, who started observing their large numbers about several years ago when one leaped on her hand as she was walking out of her front door.

Environmental Consequences Stays Unknown

The noise isn't the primary problem, though. While the amphibians has been in the Galápagos for almost three decades, scientists still know limited information about its impact on the islands' delicately balanced terrestrial and aquatic environments.

On archipelagos, it is very typical for invasive organisms to prosper, as they have few of their natural predators. The islands has 1,645 invasive types, many of which are seriously affecting the safety of its endemic ones.

A recent study suggests the invasive frogs are voracious insect eaters, and might be unevenly consuming rare bugs found exclusively on the islands, or reducing the nutrition of the islands' rare birds, affecting the ecosystem balance.

Unusual Traits and Management Difficulties

The island frogs have exhibited some atypical traits, including living in brackish water, which is rare for frogs.

Their development stage is also highly variable, with some larvae becoming frogs very rapidly and others taking a extended period: the researcher witnessed one which remained as a larva in her laboratory for half a year.

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

Methods to control the amphibians in the early 2000s were largely ineffective. Conservation officers tried collecting large numbers by hand and gradually raising the salinity of lagoons in vain.

Studies suggests applying caffeine – which is extremely poisonous to frogs – or using electrocution could assist, but these methods aren't necessarily secure for other uncommon Galápagos organisms.

Without solutions to more of the basic issues about their lifestyle and effect, culling the frogs might not even be the correct way to proceed, says the biologist.

Funding Challenges for Study

While she hopes the growing use of environmental DNA methods and DNA analysis will help her group make sense of the invader, financial support for the project has been hard to come by.

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