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During her regular commute to the scientific station, scientist the researcher stoops near a shallow pond surrounded by thick vegetation and collects a compact green audio device.

She had placed there overnight to record the characteristic croaks of the Scinax quinquefasciatus, known by Galápagos researchers as an non-native threat with consequences that experts are starting to comprehend.

Despite teeming with unique wildlife – such as ancient giant tortoises, swimming iguanas, and the well-known birds that inspired Darwin's theory of evolution – the Galápagos archipelago off the coast of Ecuador had historically been devoid of frogs and toads.

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

Genetic studies suggest that, over the years, there have been multiple accidental introductions to the islands, and the amphibians now have a strong foothold on two locations: Isabela and Santa Cruz.

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

When San José marked frogs and attempted to recapture them in the subsequent week and a half, she could locate just one tagged 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'm quite certain there are additional numbers."

Deafening Noise and Growing Concerns

The frogs' proliferation is clear from the acoustic chaos they create. "The amount of frogs and the noise – it's truly incredible," comments the scientist.

For the scientists, their nightly mating calls are useful in determining their presence in far-flung areas, using recorders like the one outside the office.

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

"During the wet season, I regularly hear their calls and they're really loud," says a local coffee farmer from the island.

"Initially it was a surprise, seeing the initial frogs in the area," says Larrea Saltos, who started noticing their large numbers about several years ago when one leaped on her palm as she was stepping out of her house.

Environmental Consequences Stays Unknown

The noise isn't the fundamental problem, however. While the amphibians has been in the islands for nearly 30 years, experts still know very little about its impact on the islands' precariously balanced terrestrial and aquatic ecosystems.

On archipelagos, it is very typical for invasive organisms to prosper, as they have none of their enemies. The Galápagos counts over sixteen hundred invasive species, many of which are significantly disrupting the safety of its endemic ones.

A recent research suggests the invasive frogs are voracious insect consumers, and might be disproportionately consuming uncommon bugs found only on the archipelago, or reducing the nutrition of the region's uncommon birds, affecting the ecosystem balance.

Unusual Traits and Management Difficulties

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

Their development process is also highly variable, with some larvae turning into frogs very quickly and others taking a long time: the researcher observed one which stayed as a tadpole in her laboratory for six months.

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

Techniques to curb the frogs in the early 2000s were mostly unsuccessful. Park rangers tried capturing significant quantities by manual methods and gradually increasing the salt content of ponds in without success.

Studies indicates spraying caffeine – which is extremely poisonous to amphibians – or using electrocution could help, but these methods aren't always safe for other uncommon Galápagos organisms.

Without answers to more of the fundamental questions about their lifestyle and impact, culling the amphibians might not even be the right way to proceed, says San José.

Financial Obstacles for Study

While she hopes the increasing use of environmental DNA methods and DNA examination will help her group understand of the invasive species, funding for the research has been hard to come by.

"Everyone wants to give support for preserving frogs," says San José. "But it's more difficult to find financial backing for an invasive frog that you might want to control."