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During her daily commute to the research facility, scientist the researcher stoops near a small pond surrounded by thick vegetation and retrieves a small plastic audio device.

The device was left there through the night to record the characteristic croaks of the Scinax quinquefasciatus, known by Galápagos scientists as an invasive threat with effects that experts are just beginning to understand.

Despite abounding with unique animals – including centuries-old giant tortoises, swimming lizards, and the famous finches that sparked Darwin's theory of evolution – the island chain near the shoreline of Ecuador had long remained devoid of amphibians.

During the 1990s, this shifted. Several tiny amphibians made their way from continental Ecuador to the archipelago, likely as stowaways on transport vessels.

Genetic research suggest that, through time, there have been multiple unintentional introductions to the archipelago, and the frogs now have a strong presence on several islands: Isabela and Santa Cruz.

The numbers is expanding so quickly that scientists have been struggling to monitor, estimating numbers in the hundreds of thousands on each island, across developed and agricultural areas, but also in the conservation natural reserve.

When the biologist marked amphibians and attempted to recapture them in the subsequent week and a half, she could find only a single marked frog from time to time, indicating their numbers were massive.

They calculated six thousand frogs in a single pond. "Our estimates are still very conservative," states San José. "I'm pretty sure there are additional numbers."

Acoustic Chaos and Growing Concerns

The amphibians' proliferation is clear from the acoustic disruption they create. "The number of frogs and the sound – it's really incredible," says the scientist.

For the scientists, their nightly mating calls are helpful in estimating their presence in far-flung areas, using recorders like the one outside the workplace.

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

"In the wet season, I constantly hear their croaks and they're really loud," says a local coffee farmer from the island.

"Initially it was a surprise, seeing the initial frogs in the region," says Larrea Saltos, who started noticing their abundance about several years ago when one jumped on her palm as she was stepping out of her front door.

Ecological Impact Remains Unclear

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 effect on the archipelago's precariously balanced land and water environments.

On islands, it is very common for invasive organisms to prosper, as they have few of their enemies. The islands has over sixteen hundred introduced species, many of which are significantly disrupting the safety of its native ones.

A 2020 research suggests the non-native amphibians are hungry insect eaters, and might be disproportionately consuming uncommon bugs found exclusively on the archipelago, or depleting the food sources of the islands' uncommon avian species, affecting the ecosystem balance.

Unusual Traits and Management Difficulties

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

Their metamorphosis process is also highly inconsistent, with some larvae becoming frogs very quickly and others taking a long time: the researcher witnessed one which remained as a tadpole in her laboratory for half a year.

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

Methods to control the amphibians in the early 2000s were largely ineffective. Conservation officers tried capturing large numbers by manual methods and slowly increasing the salinity of lagoons in vain.

Studies suggests spraying coffee – which is highly poisonous to frogs – or using electrical methods could help, but these approaches aren't necessarily secure for other rare island organisms.

Without answers to more of the basic issues about their lifestyle and effect, culling 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 techniques and genetic analysis will assist her team understand of the invader, financial support for the research has been difficult to come by.

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