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On her daily walk to the research facility, scientist the researcher stoops near a small water body surrounded by thick plants and collects a compact green sound device.

She had placed there overnight to record the characteristic croaks of the Fowler's snouted treefrog, known by Galápagos scientists as an invasive species with consequences that scientists are just beginning to understand.

Although teeming with unique wildlife – such as ancient large turtles, marine lizards, and the famous finches that sparked Darwin's evolutionary theory – the island chain off the coast of Ecuador had historically been free of frogs and toads.

During the 1990s, this changed. Some small tree frogs traveled from continental the mainland to the archipelago, likely as stowaways on transport vessels.

Genetic studies indicate that, through time, there have been repeated unintentional introductions to the islands, and the frogs now have a firm foothold on several locations: multiple locations.

The population is expanding so rapidly that researchers have been finding it difficult to monitor, calculating numbers in the millions on each island, across developed and farming areas, but also in the conservation 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 tagged frog occasionally, indicating their numbers were massive.

They calculated 6,000 frogs in a solitary pond. "The calculations are still very low," states the researcher. "I'm quite certain there are additional numbers."

Acoustic Chaos and Rising Worries

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

For the researchers, their nocturnal vocalizations are useful in determining their existence in far-flung areas, using audio devices like the one near the workplace.

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

"In the rainy period, I constantly hear their croaks and they're extremely 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 observing their abundance about three years ago when one leaped on her palm as she was walking out of her house.

Environmental Consequences Stays Unclear

The sound isn't the fundamental problem, though. While the species has been in the Galápagos for almost 30 years, experts still know very little about its impact on the islands' precariously balanced terrestrial and aquatic ecosystems.

On archipelagos, it is very common for invasive species to prosper, as they have none of their enemies. The islands counts 1,645 invasive species, many of which are seriously affecting the safety of its endemic ones.

A 2020 study suggests the invasive amphibians are voracious insect consumers, and might be disproportionately eating uncommon insects found only on the islands, or depleting the food sources of the region's rare birds, disrupting the ecosystem balance.

Unusual Traits and Control Challenges

The island amphibians have shown some atypical traits, including surviving in slightly salty water, which is uncommon for frogs.

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

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

Methods to curb the amphibians in the early 2000s were largely unsuccessful. Conservation officers tried collecting large numbers by manual methods and slowly increasing the salt content of lagoons in without success.

Studies indicates applying coffee – which is highly toxic to amphibians – or using electrocution could help, but these methods aren't always safe for other uncommon Galápagos species.

Lacking answers to more of the fundamental questions about their biology and effect, removing the amphibians might not even be the right way to advance, says the biologist.

Financial Obstacles for Research

While she hopes the increasing use of eDNA methods and DNA examination will assist her team make sense of the invader, financial support for the project has been difficult to come by.

"Everybody wants to give funding for protecting frogs," says the researcher. "But it's more difficult to find funding for an introduced frog that you might want to control."