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During her regular walk to the research facility, scientist the researcher crouches near a small pond surrounded by dense plants and retrieves a small plastic sound recorder.

She had placed there through the night to record the characteristic calls of the Fowler's snouted treefrog, recognized by Galápagos researchers as an non-native threat with effects that experts are starting to understand.

Despite abounding with unique wildlife – such as ancient large turtles, swimming lizards, and the famous finches that inspired Darwin's evolutionary theory – the Galápagos archipelago near the shoreline of Ecuador had historically been devoid of amphibians.

During the 1990s, this changed. Some tiny amphibians traveled from continental Ecuador to the archipelago, likely as stowaways on transport vessels.

DNA studies indicate that, through time, there have been repeated unintentional introductions to the islands, and the amphibians now have a firm presence on two islands: multiple locations.

The numbers is growing so rapidly that researchers have been finding it difficult to keep track, calculating numbers in the millions 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 following week and a half, she could locate only a single tagged frog from time to time, indicating their numbers were enormous.

They calculated six thousand frogs in a single pond. "Our estimates are still very conservative," states the researcher. "I am pretty sure there are additional numbers."

Deafening Noise and Rising Worries

The amphibians' abundance is clear from the acoustic chaos they create. "The number of frogs and the noise – it's really insane," comments the scientist.

For the researchers, their nocturnal vocalizations are useful in estimating their presence in remote areas, using audio devices like the one outside San José's workplace.

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

"During the wet season, I regularly hear their calls and they're extremely loud," says Jadira Larrea Saltos from Santa Cruz.

"Initially it was a surprise, seeing the first frogs in the area," says Larrea Saltos, who started observing their abundance about three years ago when one leaped on her palm as she was stepping out of her house.

Ecological Impact Stays Unknown

The sound isn't the primary problem, however. While the species has been in the Galápagos for nearly 30 years, scientists still know limited information about its impact on the archipelago's precariously balanced land and water ecosystems.

On islands, it is very common for non-native organisms to prosper, as they have none of their enemies. The islands counts 1,645 introduced types, many of which are seriously disrupting the safety of its endemic ones.

A 2020 study suggests the invasive frogs are voracious insect consumers, and might be unevenly consuming uncommon bugs found only on the archipelago, or reducing the nutrition of the islands' uncommon birds, disrupting the ecosystem balance.

Unique Characteristics and Management Difficulties

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

Their development process is also highly inconsistent, with some tadpoles becoming frogs very quickly and others taking a extended period: the researcher witnessed one which remained as a tadpole in her lab for six months.

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

Methods to curb the amphibians in the beginning of the century were largely ineffective. Park rangers tried capturing significant quantities by hand and slowly raising the salt content of lagoons in without success.

Research indicates applying coffee – which is highly toxic to frogs – or using electrical methods could assist, but these approaches aren't necessarily safe for other rare Galápagos organisms.

Without answers to more of the fundamental issues about their biology and impact, removing the frogs might not even be the right way to advance, says San José.

Funding Challenges for Study

While she expects the growing use of eDNA methods and DNA analysis will assist her group understand of the invasive species, funding for the project has been hard to come by.

"Everybody wants to give funding for protecting frogs," says the researcher. "But it's more difficult to find funding for an invasive frog that you might want to manage."