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During her regular commute to the scientific station, biologist the researcher stoops near a small pond surrounded by dense vegetation and retrieves a compact plastic audio recorder.

The device was left there overnight to capture the characteristic croaks of the Scinax quinquefasciatus, known by local researchers as an invasive threat with effects that experts are just beginning to understand.

Despite abounding with remarkable animals – such as ancient giant tortoises, swimming lizards, and the famous finches that sparked Charles Darwin's evolutionary theory – the island chain off the coast of Ecuador had long remained devoid of frogs and toads.

During the 1990s, this changed. Several tiny amphibians traveled from continental the mainland to the archipelago, probably as hitchhikers on transport vessels.

DNA research indicate that, over the years, there have been repeated unintentional introductions to the archipelago, and the frogs now have a firm presence on several islands: multiple locations.

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

When the biologist marked frogs and attempted to recapture them in the following week and a half, she could locate only a single tagged frog from time to time, suggesting their populations were massive.

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

Deafening Noise and Rising Worries

The amphibians' proliferation is evident from the acoustic chaos they cause. "The amount of frogs and the noise – it's really incredible," comments San José.

For the researchers, their nocturnal mating calls are useful in determining their existence in far-flung areas, using audio devices like the one outside San José's office.

But nearby agricultural workers say the sounds are so loud they prevent sleep at night.

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

"Initially it was a shock, seeing the first frogs in the area," says Larrea Saltos, who started noticing their large numbers about three years ago when one jumped on her hand as she was walking out of her house.

Environmental Consequences Remains Unclear

The sound isn't the primary problem, though. While the species has been in the Galápagos for almost three decades, experts still know very little about its effect on the archipelago's delicately balanced land and water environments.

On archipelagos, it is very common for invasive organisms to prosper, as they have none of their natural predators. The islands has 1,645 introduced types, many of which are significantly disrupting the safety of its endemic ones.

A recent research indicates the invasive amphibians are hungry bug consumers, and might be disproportionately eating uncommon insects found exclusively on the islands, or depleting the nutrition of the region's uncommon birds, disrupting the food chain.

Unusual Traits and Management Difficulties

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

Their development stage is also highly inconsistent, with some larvae turning into frogs very quickly and others taking a long time: the researcher observed 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 clean water, a very scarce resource in the islands.

Techniques to control the amphibians in the early 2000s were largely unsuccessful. Conservation officers tried capturing significant quantities by hand and gradually increasing the salt content of ponds in without success.

Studies suggests spraying caffeine – which is extremely poisonous to amphibians – or using electrical methods could assist, but these approaches aren't necessarily safe for other uncommon island species.

Lacking solutions to more of the fundamental questions about their lifestyle and effect, removing the amphibians might not even be the right way to proceed, says the biologist.

Financial Obstacles for Research

While she expects the increasing use of environmental DNA techniques and genetic examination will assist her team understand of the invader, funding for the research has been difficult to obtain.

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