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During her regular commute to the research facility, scientist Miriam San José crouches near a small pond covered by dense plants and retrieves a small green sound recorder.

The device was left there through the night to capture the distinctive croaks of the Fowler's snouted treefrog, known by local researchers as an invasive species with effects that scientists are starting to comprehend.

Despite teeming with remarkable animals – such as ancient large turtles, swimming iguanas, and the well-known birds that sparked Darwin's theory of evolution – the island chain near the shoreline of Ecuador had historically been free of amphibians.

In the late 1990s, this shifted. Some tiny amphibians traveled from mainland the mainland to the archipelago, likely as hitchhikers on transport vessels.

DNA studies indicate that, through time, there have been multiple accidental arrivals to the islands, and the frogs now have a strong presence on several islands: Isabela and Santa Cruz.

The population 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 recapture them in the following week and a half, she could find just one marked frog occasionally, suggesting their numbers were massive.

They estimated 6,000 frogs in a single pond. "Our estimates are still very conservative," states San José. "I am pretty sure there are additional numbers."

Deafening Noise and Rising Worries

The amphibians' proliferation is evident from the sound chaos they create. "The number of frogs and the sound – it's truly insane," says the scientist.

For the researchers, their nocturnal vocalizations are useful in determining their presence in remote areas, using audio devices like the one outside San José's workplace.

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

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

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

Environmental Consequences Remains Unknown

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

On islands, it is very common for non-native species to prosper, as they have few of their enemies. The islands counts 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 consumers, and might be unevenly consuming uncommon bugs found exclusively on the islands, or reducing the nutrition of the islands' uncommon avian species, affecting the food chain.

Unusual Traits and Management Difficulties

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

Their development stage is also extremely variable, with some tadpoles becoming frogs very quickly and others taking a long time: San José observed one which stayed as a tadpole in her lab for six months.

"We truly don't know this part," she says, worried the tadpoles could be affecting the region's freshwater, a very limited resource in the islands.

Techniques to control the amphibians in the beginning of the century were largely ineffective. Conservation officers tried capturing large numbers by manual methods and gradually raising the salinity of ponds in vain.

Studies suggests applying caffeine – which is extremely toxic to frogs – or using electrocution could assist, but these approaches aren't necessarily secure for other uncommon Galápagos organisms.

Lacking solutions to more of the basic questions about their biology and effect, culling the frogs might not even be the right way to proceed, says San José.

Financial Obstacles for Study

While she hopes the increasing use of eDNA techniques and genetic analysis will help her group make sense of the invasive species, financial support for the project has been difficult to come by.

"Everyone wants to give funding for protecting frogs," says San José. "But it's more difficult to find financial backing for an invasive frog that you might want to control."