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On her regular walk to the scientific station, scientist Miriam San José stoops near a small pond surrounded by dense plants and retrieves a small green sound recorder.

She had placed there through the night to capture the distinctive calls of the Fowler's snouted treefrog, known by local scientists as an invasive species with effects that scientists are just beginning to comprehend.

Despite abounding with unique wildlife – such as ancient giant tortoises, marine lizards, and the famous finches that inspired Charles Darwin's theory of evolution – the island chain near the shoreline of South America had historically been devoid of amphibians.

During the 1990s, this changed. Some small tree frogs traveled from continental the mainland to the archipelago, likely as hitchhikers on transport vessels.

Genetic research suggest that, over the years, there have been repeated accidental arrivals to the archipelago, and the frogs now have a strong presence on several locations: Isabela and Santa Cruz.

The numbers is expanding so rapidly that scientists have been finding it difficult to keep track, calculating populations in the hundreds of thousands on each island, across urban and farming areas, but also in the conservation natural reserve.

When the biologist marked frogs and attempted to recapture them in the subsequent 10 days, she could locate only a single tagged frog occasionally, indicating their numbers were enormous.

They calculated six thousand frogs in a solitary pond. "Our estimates are still very conservative," says the researcher. "I'm quite certain there are additional numbers."

Acoustic Chaos and Growing Concerns

The amphibians' proliferation is evident from the sound disruption they cause. "The amount of frogs and the noise – it's really insane," says San José.

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

But nearby farmers say the sounds are so raucous they keep them up at night.

"In the rainy period, I constantly hear their calls and they're really loud," says Jadira Larrea Saltos from Santa Cruz.

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

Environmental Consequences Stays Unclear

The noise isn't the fundamental problem, though. While the amphibians 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 environments.

On islands, it is very common for invasive organisms to thrive, as they have none of their enemies. The Galápagos has 1,645 invasive species, many of which are seriously disrupting the survival of its endemic ones.

A recent research indicates the invasive frogs are hungry insect consumers, and might be unevenly consuming rare bugs found only on the archipelago, or depleting the nutrition of the region's uncommon avian species, affecting the ecosystem balance.

Unusual Traits and Control Challenges

The island amphibians have exhibited some atypical traits, including living in slightly salty water, which is rare for amphibians.

Their development process is also extremely inconsistent, with some larvae becoming frogs very quickly and others taking a long time: San José witnessed one which stayed as a tadpole in her laboratory for half a year.

"We truly don't know this part," she says, concerned the tadpoles could be affecting the region's clean water, a very limited commodity in the islands.

Methods to control the frogs in the early 2000s were mostly unsuccessful. Conservation officers tried capturing large numbers by manual methods and slowly raising the salinity of ponds in vain.

Research indicates applying caffeine – which is extremely poisonous to frogs – or using electrocution could assist, but these approaches aren't always safe for other rare Galápagos organisms.

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

Funding Challenges for Research

While she expects the increasing use of eDNA techniques and DNA examination will help her team understand of the invasive species, financial support for the project has been hard 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 manage."