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During her regular walk to the research facility, scientist the researcher stoops near a small pond surrounded by thick vegetation and retrieves a small plastic sound device.

She had placed there through the night to capture the characteristic croaks of the Scinax quinquefasciatus, recognized by local scientists as an non-native species with consequences that experts are just beginning to understand.

Despite teeming with remarkable wildlife – such as centuries-old large turtles, swimming iguanas, and the famous finches that inspired Darwin's evolutionary theory – the island chain off the shoreline of Ecuador had long remained devoid of frogs and toads.

In the late 1990s, this shifted. Some tiny tree frogs made their way from continental the mainland to the islands, likely as hitchhikers on transport vessels.

Genetic studies suggest that, over the years, there have been multiple accidental introductions to the islands, and the frogs now have a strong presence on two locations: Isabela and Santa Cruz.

The population is growing so rapidly that researchers have been finding it difficult to keep track, estimating numbers in the hundreds of thousands on each island, across urban and agricultural areas, but also in the protected natural reserve.

When the biologist tagged amphibians and attempted to find them in the following 10 days, she could find just one marked frog from time to time, indicating their numbers were massive.

They calculated 6,000 frogs in a solitary pond. "Our estimates are still very conservative," says the researcher. "I am pretty sure there are additional numbers."

Deafening Noise and Rising Worries

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

For the researchers, their nocturnal mating calls are helpful in estimating their existence in far-flung areas, using recorders like the one outside the office.

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

"In the rainy period, I constantly hear their croaks and they're extremely loud," says a local coffee farmer from the island.

"Initially it was a shock, seeing 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 walking out of her house.

Environmental Consequences Stays Unclear

The sound isn't the primary problem, though. While the amphibians has been in the islands for nearly three decades, scientists still know very little about its effect on the islands' delicately balanced land and water ecosystems.

On islands, it is very common for non-native organisms to prosper, as they have few of their natural predators. The islands has 1,645 invasive types, many of which are seriously disrupting the survival of its native ones.

A recent research suggests the invasive frogs are voracious bug eaters, and might be unevenly eating rare insects found only on the archipelago, or reducing the food sources of the islands' uncommon avian species, disrupting the ecosystem balance.

Unique Characteristics and Management Difficulties

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

Their metamorphosis process is also extremely variable, with some larvae becoming frogs very quickly and others taking a extended period: the researcher witnessed one which remained as a larva in her laboratory for six months.

"We really don't know this part," she says, concerned the tadpoles could be affecting the islands' freshwater, a very limited commodity in the islands.

Methods to curb the amphibians in the early 2000s were mostly ineffective. Park rangers tried collecting large numbers by manual methods and slowly increasing the salinity of ponds in without success.

Research suggests spraying coffee – which is extremely poisonous to frogs – or using electrical methods could assist, but these approaches aren't necessarily safe for other rare Galápagos organisms.

Lacking answers to more of the fundamental issues about their lifestyle and impact, removing the frogs might not even be the right way to proceed, says the biologist.

Funding Challenges for Research

While she hopes the increasing use of environmental DNA techniques and DNA examination will help her team make sense of the invasive species, funding for the research has been hard to come by.

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