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During her regular commute to the research facility, biologist Miriam San José stoops near a small pond covered by thick plants and collects a small plastic audio device.

She had placed there overnight to record the distinctive calls of the Fowler's snouted treefrog, recognized by local scientists as an invasive threat with consequences that experts are just beginning to comprehend.

Despite abounding with remarkable wildlife – including ancient large turtles, marine iguanas, and the well-known finches that sparked Darwin's theory of evolution – the island chain near the coast of Ecuador had long remained devoid of frogs and toads.

In the late 1990s, this changed. Some tiny tree frogs made their way from continental the mainland to the islands, probably as stowaways on cargo ships.

Genetic studies indicate that, over the years, there have been repeated unintentional arrivals to the islands, and the frogs now have a firm presence on two islands: multiple locations.

The numbers is growing so quickly that researchers have been struggling to keep track, calculating populations in the millions on each island, across urban and farming areas, but also in the conservation natural reserve.

When the biologist tagged amphibians and attempted to recapture them in the following 10 days, she could find only a single tagged frog occasionally, suggesting their numbers were massive.

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

Deafening Noise and Rising Worries

The amphibians' proliferation is evident from the acoustic disruption they cause. "The number of frogs and the sound – it's truly insane," comments San José.

For the scientists, their nocturnal vocalizations are helpful in determining their presence in far-flung areas, using recorders like the one outside the workplace.

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

"During the rainy period, I constantly hear their calls and they're really loud," says a local coffee farmer from Santa Cruz.

"Initially it was a surprise, observing the initial frogs in the area," says the farmer, who started observing their large numbers about three years ago when one leaped on her hand as she was walking out of her front door.

Environmental Consequences Remains Unknown

The noise isn't the fundamental problem, though. While the amphibians has been in the Galápagos for almost 30 years, experts still know very little about its effect on the archipelago's delicately balanced terrestrial and aquatic environments.

On archipelagos, it is very typical for non-native species to thrive, as they have few of their enemies. The islands has over sixteen hundred invasive species, many of which are seriously disrupting the safety of its endemic ones.

A 2020 research suggests the non-native amphibians are hungry insect consumers, and might be unevenly eating rare insects found only on the islands, or reducing the nutrition of the region's rare birds, affecting the ecosystem balance.

Unique Characteristics and Management Difficulties

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

Their development stage is also extremely variable, with some larvae turning into frogs very rapidly and others taking a extended period: San José witnessed one which remained as a larva in her laboratory for half a year.

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

Techniques to curb the amphibians in the early 2000s were largely ineffective. Conservation officers tried capturing significant quantities by hand and slowly raising the salt content of ponds in without success.

Research indicates applying coffee – which is highly toxic to amphibians – or using electrical methods could assist, but these approaches aren't always safe for other uncommon island species.

Lacking answers to more of the fundamental issues about their biology and effect, removing the amphibians might not even be the correct way to proceed, says the biologist.

Funding Challenges for Research

While she expects the growing use of eDNA methods and genetic examination will help her group understand of the invasive species, funding for the research has been hard to come by.

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