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During her regular commute to the research facility, biologist the researcher stoops near a shallow water body covered by thick vegetation and retrieves a compact green audio device.

The device was left there through the night to capture the characteristic calls of the Scinax quinquefasciatus, known by Galápagos scientists as an non-native species with effects that scientists are starting to comprehend.

Although teeming with unique wildlife – such as centuries-old large turtles, swimming lizards, and the well-known birds that inspired Charles Darwin's theory of evolution – the island chain near the coast of Ecuador had long remained devoid of amphibians.

In the late 1990s, this changed. Some small tree frogs made their way from mainland the mainland to the archipelago, likely as stowaways on cargo ships.

DNA research suggest that, over the years, there have been repeated accidental arrivals to the archipelago, and the amphibians now have a firm foothold on two locations: multiple locations.

The population is growing so rapidly that researchers have been struggling to keep track, calculating numbers in the hundreds of thousands on each island, across developed and farming areas, but also in the conservation Galápagos national park.

When San José marked amphibians and attempted to find them in the following 10 days, she could find only a single tagged frog occasionally, suggesting their numbers were massive.

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

Acoustic Chaos and Growing Concerns

The frogs' abundance is evident from the sound chaos they create. "The amount of frogs and the sound – it's truly insane," says San José.

For the scientists, their nocturnal vocalizations are helpful in estimating their existence in remote areas, using audio devices like the one near the office.

But local agricultural workers say the calls are so raucous they keep them up at night.

"In the rainy period, I regularly hear their calls and they're really loud," says a local coffee farmer from Santa Cruz.

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

Ecological Impact Remains Unclear

The sound isn't the fundamental problem, however. While the amphibians has been in the islands for almost 30 years, experts still know limited information about its impact on the archipelago's precariously balanced land and water environments.

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

A 2020 study suggests the invasive amphibians are voracious insect eaters, and might be unevenly consuming uncommon bugs found exclusively on the archipelago, or depleting the nutrition of the region's uncommon birds, affecting the food chain.

Unique Characteristics and Control Challenges

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

Their development process is also highly variable, with some larvae turning into frogs very rapidly and others taking a extended period: San José observed one which stayed as a tadpole in her lab for six months.

"We really don't know this part," she says, concerned the larvae could be affecting the region's clean water, a very scarce resource in the islands.

Methods to curb the amphibians in the early 2000s were largely unsuccessful. Park rangers tried collecting significant quantities by manual methods and gradually increasing the salt content of ponds in vain.

Studies suggests applying caffeine – which is extremely toxic to amphibians – or using electrocution could help, but these methods aren't necessarily secure for other rare island organisms.

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

Financial Obstacles for Research

While she hopes the increasing use of environmental DNA techniques and genetic examination will assist her team understand of the invasive species, financial support for the project has been difficult to come by.

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