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During her regular commute to the scientific station, scientist the researcher crouches near a shallow pond covered by dense vegetation and retrieves a compact green sound device.

She had placed there through the night to record the distinctive croaks of the Fowler's snouted treefrog, known by Galápagos researchers as an non-native threat with effects that experts are just beginning to comprehend.

Despite teeming with unique animals – such as ancient large turtles, marine iguanas, and the well-known birds that inspired Charles Darwin's theory of evolution – the island chain near the shoreline of Ecuador had long remained free of amphibians.

During the 1990s, this changed. Several small tree frogs made their way from continental Ecuador to the islands, likely as hitchhikers on transport vessels.

Genetic studies indicate that, through time, there have been multiple accidental arrivals to the islands, and the frogs now have a strong foothold on two islands: multiple locations.

The population is growing so rapidly that researchers have been finding it difficult to keep track, calculating numbers in the millions on each island, across urban and farming areas, but also in the protected Galápagos national park.

When San José tagged frogs and attempted to find them in the subsequent week and a half, she could locate only a single marked frog from time to time, suggesting their numbers were massive.

They estimated 6,000 frogs in a single pond. "Our estimates are still very low," states San José. "I am pretty sure there are additional numbers."

Deafening Noise and Growing Concerns

The frogs' abundance is evident from the acoustic chaos they cause. "The number of frogs and the noise – it's truly incredible," says the scientist.

For the researchers, their nightly vocalizations are helpful in estimating their existence in remote areas, using recorders like the one outside San José's workplace.

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

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

"At first it was a surprise, observing the initial frogs in the area," says Larrea Saltos, who started noticing their abundance about three 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 fundamental problem, however. While the species has been in the islands for almost 30 years, experts still know very little about its effect on the archipelago's delicately balanced land and water ecosystems.

On archipelagos, it is very common for invasive species to thrive, as they have none of their natural predators. The Galápagos counts over sixteen hundred invasive types, many of which are significantly affecting the safety of its endemic ones.

A recent research suggests the invasive amphibians are voracious bug eaters, and might be unevenly consuming rare insects found exclusively on the archipelago, or reducing the nutrition of the region's rare avian species, affecting the food chain.

Unusual Traits and Control Challenges

The Galápagos amphibians have shown some unusual characteristics, including surviving in brackish water, which is uncommon for frogs.

Their metamorphosis stage is also extremely inconsistent, with some tadpoles becoming frogs very quickly and others taking a extended period: the researcher observed one which remained as a larva in her lab for six months.

"We truly don't know this part," she says, worried the larvae could be impacting the islands' freshwater, a very limited resource in Galápagos.

Techniques to curb the frogs in the beginning of the century were largely unsuccessful. Park rangers tried capturing significant quantities by manual methods and slowly increasing the salinity of ponds in without success.

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

Lacking solutions to more of the basic issues about their biology 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 genetic analysis will assist her group understand of the invader, financial support for the project has been difficult to obtain.

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