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During her daily walk to the research facility, biologist Miriam San José stoops near a shallow water body surrounded by thick vegetation and collects a small plastic sound recorder.

The device was left there overnight to capture the characteristic calls of the Scinax quinquefasciatus, recognized by local researchers as an non-native species with consequences that scientists are just beginning to understand.

Despite abounding with unique wildlife – including ancient large turtles, marine iguanas, and the famous finches that sparked Charles Darwin's theory of evolution – the Galápagos archipelago off the coast of South America had historically been free of frogs and toads.

During the 1990s, this shifted. Several small tree frogs traveled from continental the mainland to the islands, likely as hitchhikers on cargo ships.

Genetic studies indicate that, through time, there have been repeated unintentional introductions to the archipelago, and the frogs now have a strong foothold on several islands: Isabela and Santa Cruz.

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

When the biologist tagged amphibians and attempted to find them in the subsequent week and a half, she could locate just one tagged frog occasionally, suggesting their numbers were massive.

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

Deafening Noise and Rising Worries

The frogs' abundance is evident from the acoustic chaos they cause. "The amount of frogs and the noise – it's truly insane," says the scientist.

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

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

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

"At first it was a surprise, seeing the initial frogs in the area," says Larrea Saltos, who started observing their abundance about several years ago when one jumped on her palm as she was walking out of her front door.

Ecological Impact Remains Unclear

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

On islands, it is very common for non-native organisms to thrive, as they have none of their enemies. The islands counts over sixteen hundred invasive species, many of which are significantly disrupting the safety of its native ones.

A 2020 research indicates the non-native frogs are hungry bug consumers, and might be unevenly consuming uncommon bugs found only on the archipelago, or reducing the food sources of the region's rare avian species, affecting the ecosystem balance.

Unusual Traits and Management Difficulties

The island amphibians have shown some unusual traits, including surviving in brackish water, which is rare for amphibians.

Their development process is also extremely variable, with some tadpoles becoming frogs very rapidly and others taking a extended period: the researcher witnessed one which stayed 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 amphibians in the early 2000s were mostly unsuccessful. Conservation officers tried collecting significant quantities by manual methods and gradually raising the salinity of lagoons in vain.

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

Lacking solutions to more of the basic issues about their lifestyle and effect, removing the frogs might not even be the right way to advance, says the biologist.

Financial Obstacles for Research

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

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