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

The device was left there overnight to record the characteristic calls of the Scinax quinquefasciatus, recognized by Galápagos scientists as an invasive threat with effects that experts are starting to comprehend.

Despite abounding with unique wildlife – including ancient giant tortoises, marine lizards, and the famous finches that inspired Darwin's evolutionary theory – the Galápagos archipelago near the coast of Ecuador had historically been devoid of frogs and toads.

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

DNA research indicate that, over the years, there have been multiple unintentional arrivals to the archipelago, and the amphibians now have a strong foothold on two locations: multiple locations.

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

When San José marked frogs and attempted to recapture them in the following 10 days, she could find just one tagged frog occasionally, indicating their populations were enormous.

They calculated 6,000 frogs in a solitary pond. "The calculations are still very low," states the researcher. "I'm quite certain there are even more."

Deafening Noise and Growing Concerns

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

For the researchers, their nightly mating calls are helpful in determining their existence in far-flung areas, using recorders like the one near the 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 croaks and they're really 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 observing their large numbers about several years ago when one leaped on her palm as she was walking out of her house.

Environmental Consequences Stays Unknown

The sound isn't the primary problem, however. While the amphibians has been in the islands for almost three decades, experts still know limited information about its effect on the archipelago's precariously balanced land and water environments.

On islands, it is very typical for non-native species to thrive, as they have few of their natural predators. The islands counts over sixteen hundred invasive species, many of which are significantly affecting the survival of its endemic ones.

A 2020 research indicates the non-native frogs are hungry insect consumers, and might be unevenly eating rare bugs found exclusively on the archipelago, or depleting the food sources of the islands' uncommon birds, disrupting the ecosystem balance.

Unusual Traits and Control Challenges

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

Their metamorphosis process is also extremely variable, with some tadpoles becoming frogs very rapidly and others taking a long time: the researcher observed one which stayed as a tadpole in her laboratory for six months.

"We really don't know this aspect," she says, worried the tadpoles could be impacting the islands' clean water, a very limited commodity in the islands.

Techniques to curb the frogs in the beginning of the century were largely ineffective. Park rangers tried collecting significant quantities by hand and gradually increasing the salt content of ponds in without success.

Studies indicates spraying coffee – which is extremely toxic to amphibians – or using electrical methods could assist, but these methods aren't always secure for other uncommon island organisms.

Without solutions to more of the fundamental issues about their biology and effect, culling the frogs might not even be the correct way to advance, says San José.

Funding Challenges for Research

While she expects the growing use of environmental DNA methods and genetic examination will assist her team make sense of the invader, funding for the research has been hard to come by.

"Everyone wants to give support for preserving frogs," says the researcher. "But it's more difficult to find funding for an introduced frog that you might want to control."