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On her daily commute to the research facility, scientist the researcher crouches near a small water body surrounded by dense plants and retrieves a small green audio device.

She had placed there overnight to capture the distinctive calls of the Fowler's snouted treefrog, known by Galápagos researchers as an invasive species with effects that experts are just beginning to comprehend.

Despite teeming with unique animals – such as ancient giant tortoises, marine iguanas, and the well-known birds that sparked Charles Darwin's theory of evolution – the Galápagos archipelago near the shoreline of Ecuador had long remained free of frogs and toads.

During the 1990s, this changed. Several small amphibians traveled from continental Ecuador to the archipelago, probably as stowaways on transport vessels.

Genetic research indicate that, through time, there have been repeated unintentional arrivals to the archipelago, and the amphibians now have a strong presence on two locations: Isabela and Santa Cruz.

The population is expanding so rapidly that scientists have been finding it difficult to keep track, calculating populations in the millions on each island, across urban and agricultural areas, but also in the protected Galápagos national park.

When San José tagged frogs and attempted to find them in the following 10 days, 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 low," says San José. "I am quite certain there are additional numbers."

Acoustic Chaos and Growing Concerns

The amphibians' abundance is evident from the acoustic disruption they cause. "The amount of frogs and the sound – it's really incredible," comments San José.

For the researchers, their nightly mating calls are useful in estimating their existence in remote areas, using audio devices like the one outside San José's workplace.

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

"During the wet season, I regularly hear their calls and they're extremely loud," says a local coffee farmer from Santa Cruz.

"At first it was a surprise, observing the first frogs in the region," says Larrea Saltos, who started observing their large numbers about several years ago when one leaped on her hand as she was stepping out of her house.

Ecological Impact Remains Unknown

The noise isn't the fundamental problem, however. While the species 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 environments.

On islands, it is very typical for non-native organisms to prosper, as they have few of their enemies. The islands counts 1,645 introduced species, many of which are seriously affecting the survival of its endemic ones.

A recent research indicates the non-native amphibians are voracious insect consumers, and might be unevenly consuming uncommon insects found only on the archipelago, or depleting the nutrition of the region's rare avian species, disrupting the ecosystem balance.

Unique Characteristics and Management Difficulties

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

Their development process is also highly inconsistent, with some tadpoles turning into frogs very quickly and others taking a long time: San José observed one which stayed as a larva in her laboratory for six months.

"We truly don't know this part," she says, worried the tadpoles could be impacting the region's clean water, a very scarce resource in Galápagos.

Techniques to control the amphibians in the early 2000s were largely ineffective. Conservation officers tried capturing large numbers by manual methods and gradually increasing the salt content of ponds in vain.

Research indicates spraying coffee – which is highly toxic to frogs – or using electrocution could help, but these approaches aren't always safe for other rare island species.

Without solutions to more of the fundamental issues about their lifestyle and effect, removing the amphibians might not even be the right way to advance, says the biologist.

Funding Challenges for Study

While she hopes the increasing use of environmental DNA methods and DNA analysis will help her team understand of the invasive species, funding for the project has been hard to obtain.

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