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On her regular commute to the research facility, scientist the researcher stoops near a shallow water body covered by thick plants and retrieves a compact green sound recorder.

The device was left there through the night to capture the characteristic croaks of the Fowler's snouted treefrog, known by Galápagos researchers as an non-native species with consequences that experts are starting to comprehend.

Despite teeming with unique animals – such as ancient large turtles, marine iguanas, and the famous finches that sparked Charles Darwin's evolutionary theory – the Galápagos archipelago near the shoreline of South America had historically been devoid of amphibians.

During the 1990s, this shifted. Some tiny tree frogs traveled from continental Ecuador to the islands, probably as hitchhikers on cargo ships.

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

The numbers is growing so quickly that researchers have been finding it difficult to monitor, calculating populations in the millions on each island, across developed and agricultural areas, but also in the conservation Galápagos national park.

When the biologist tagged frogs and attempted to recapture them in the following week and a half, she could find just one tagged frog occasionally, suggesting their numbers were enormous.

They estimated six thousand frogs in a single pond. "Our estimates are still very low," states the researcher. "I am quite certain there are even more."

Acoustic Chaos and Growing Concerns

The frogs' proliferation is clear from the sound disruption they create. "The amount of frogs and the sound – it's truly insane," says San José.

For the scientists, their nocturnal mating calls are helpful in determining their existence in far-flung areas, using recorders like the one outside the workplace.

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

"In the rainy period, I constantly hear their calls 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 noticing their large numbers about several years ago when one jumped on her palm as she was walking out of her house.

Environmental Consequences Stays Unknown

The noise isn't the fundamental problem, though. While the species has been in the islands for almost 30 years, scientists still know limited information about its impact on the archipelago's precariously balanced land and water ecosystems.

On archipelagos, it is very common for non-native species to thrive, as they have few of their natural predators. The Galápagos has 1,645 invasive species, many of which are seriously affecting the safety of its native ones.

A recent study suggests the invasive frogs are hungry insect eaters, and might be disproportionately consuming rare bugs found exclusively on the archipelago, or depleting the food sources of the region's uncommon birds, affecting the food chain.

Unusual Traits and Control Challenges

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

Their development stage is also extremely inconsistent, with some larvae becoming frogs very quickly and others taking a extended period: San José observed one which remained as a larva in her lab for half a year.

"We truly don't know this part," she says, concerned the larvae could be affecting the islands' freshwater, a very scarce commodity in the islands.

Methods to curb the frogs in the early 2000s were largely ineffective. Conservation officers tried collecting large numbers by hand and gradually raising the salt content of lagoons in vain.

Studies suggests spraying caffeine – which is highly poisonous to frogs – or using electrocution could help, but these methods aren't necessarily safe for other uncommon island organisms.

Without solutions to more of the basic questions about their lifestyle and impact, removing the frogs might not even be the correct way to advance, says San José.

Funding Challenges for Research

While she hopes the increasing use of environmental DNA techniques and DNA examination will assist her group make sense of the invader, financial support for the project has been hard to obtain.

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