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On her regular walk to the research facility, biologist the researcher stoops near a shallow pond covered by thick vegetation and collects a compact green audio device.

She had placed there through the night to record the distinctive croaks of the Scinax quinquefasciatus, recognized by local researchers as an non-native threat with effects that scientists are starting to comprehend.

Although abounding with unique wildlife – such as ancient large turtles, swimming lizards, and the famous birds that sparked Darwin's evolutionary theory – the island chain near the coast of South America had historically been devoid of amphibians.

During the 1990s, this changed. Some tiny tree frogs traveled from mainland Ecuador to the islands, probably as stowaways on transport vessels.

DNA studies indicate that, through time, there have been multiple unintentional introductions to the archipelago, and the amphibians now have a firm presence on several islands: multiple locations.

The population is growing so rapidly that researchers have been struggling to keep track, estimating populations in the hundreds of thousands on every island, across developed and agricultural areas, but also in the conservation natural reserve.

When San José tagged frogs and attempted to recapture them in the subsequent 10 days, she could find just one tagged frog occasionally, indicating their populations were enormous.

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

Acoustic Chaos and Growing Concerns

The frogs' abundance is evident from the acoustic chaos they create. "The amount of frogs and the noise – it's truly incredible," comments San José.

For the researchers, their nocturnal vocalizations are useful in estimating their existence in remote areas, using recorders like the one near the workplace.

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

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

"At first it was a shock, seeing the first frogs in the region," says Larrea Saltos, who started noticing their large numbers about several years ago when one jumped on her palm as she was stepping out of her front door.

Ecological Impact Stays Unclear

The sound isn't the primary problem, however. While the amphibians has been in the Galápagos for nearly three decades, experts still know very little about its effect on the archipelago's delicately balanced terrestrial and aquatic ecosystems.

On archipelagos, it is very typical for non-native organisms to prosper, as they have few of their enemies. The Galápagos has over sixteen hundred invasive species, many of which are significantly disrupting the survival of its native ones.

A recent research suggests the non-native frogs are voracious insect eaters, and might be unevenly consuming rare insects found exclusively on the archipelago, or reducing the food sources of the region's rare birds, disrupting the food chain.

Unique Characteristics and Control Challenges

The island amphibians have shown some unusual traits, including living in brackish water, which is uncommon for frogs.

Their development process is also highly variable, with some tadpoles becoming frogs very rapidly and others taking a extended period: the researcher witnessed one which stayed as a tadpole in her laboratory for six months.

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

Methods to curb the amphibians in the beginning of the century were largely unsuccessful. Conservation officers tried collecting significant quantities by manual methods and gradually increasing the salt content of ponds in without success.

Research suggests spraying caffeine – which is extremely toxic to amphibians – or using electrocution could help, but these methods aren't necessarily safe for other uncommon Galápagos organisms.

Lacking answers to more of the basic questions about their lifestyle and effect, culling the frogs might not even be the correct way to advance, says San José.

Financial Obstacles for Research

While she expects the growing use of eDNA techniques and DNA examination will help her team make sense of the invader, funding for the project has been difficult to come by.

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