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During her daily commute to the research facility, biologist the researcher stoops near a shallow pond surrounded by dense plants and collects a compact plastic audio device.

She had placed there overnight to capture the distinctive calls of the Fowler's snouted treefrog, known by local scientists as an invasive species with effects that experts are starting to understand.

Despite abounding with unique animals – such as ancient large turtles, swimming lizards, and the well-known birds that inspired Charles Darwin's evolutionary theory – the Galápagos archipelago near the coast of Ecuador had historically been free of amphibians.

During the 1990s, this changed. Several small amphibians traveled from continental the mainland to the islands, probably as hitchhikers on cargo ships.

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

The population is growing so quickly that scientists have been struggling to monitor, calculating numbers in the millions on every island, across urban and farming areas, but also in the protected Galápagos national park.

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

They estimated six thousand frogs in a solitary pond. "Our estimates are still very low," says San José. "I am pretty sure there are additional numbers."

Deafening Noise and Rising Worries

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

For the scientists, their nightly mating calls are helpful in estimating their existence in remote areas, using audio devices like the one near the workplace.

But local agricultural workers say the calls are so loud they prevent sleep at night.

"In the wet season, I regularly 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 abundance about three years ago when one jumped on her hand as she was stepping out of her front door.

Ecological Impact Stays Unknown

The sound isn't the fundamental problem, however. While the amphibians has been in the islands for almost 30 years, scientists still know limited information 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 none of their natural predators. The islands has over sixteen hundred introduced species, many of which are seriously affecting the safety of its native ones.

A 2020 research suggests the non-native amphibians are voracious insect consumers, and might be unevenly consuming uncommon insects found exclusively on the islands, or depleting the nutrition of the islands' uncommon birds, disrupting the ecosystem balance.

Unusual Traits and Control Challenges

The island frogs have exhibited some unusual traits, including living in slightly salty water, which is uncommon for amphibians.

Their development stage is also extremely variable, with some tadpoles becoming frogs very quickly and others taking a extended period: San José witnessed one which remained as a larva in her lab for six months.

"We really don't know this aspect," she says, concerned the larvae could be impacting the islands' freshwater, a very scarce resource in Galápagos.

Techniques to curb the amphibians in the early 2000s were largely ineffective. Park rangers tried collecting significant quantities by hand and gradually increasing the salt content of ponds in vain.

Research suggests spraying coffee – which is extremely poisonous to amphibians – or using electrical methods could assist, but these approaches aren't necessarily secure for other uncommon Galápagos species.

Lacking solutions to more of the fundamental questions about their biology and effect, removing the frogs might not even be the correct way to advance, says the biologist.

Financial Obstacles for Study

While she expects the growing use of eDNA techniques and genetic analysis will assist her group understand of the invader, funding for the project has been hard to obtain.

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