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During her regular walk to the research facility, scientist the researcher stoops near a small water body surrounded by thick plants and retrieves a compact plastic sound recorder.

She had placed there through the night to record the distinctive calls of the Scinax quinquefasciatus, known by local researchers as an non-native species with effects that experts are just beginning to understand.

Although abounding with remarkable wildlife – such as centuries-old giant tortoises, swimming lizards, and the well-known birds that sparked Charles Darwin's evolutionary theory – the island chain off the shoreline of Ecuador had long remained devoid of frogs and toads.

During the 1990s, this shifted. Several tiny tree frogs made their way from mainland Ecuador to the islands, likely as hitchhikers on cargo ships.

DNA research indicate that, over the years, there have been repeated accidental introductions to the archipelago, and the frogs now have a strong foothold on two islands: Isabela and Santa Cruz.

The population is expanding so rapidly that scientists have been struggling to monitor, calculating populations in the hundreds of thousands on each island, across urban and farming areas, but also in the protected natural reserve.

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

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

Acoustic Chaos and Rising Worries

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

For the researchers, their nightly vocalizations are useful in estimating their presence in far-flung areas, using recorders like the one near the office.

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

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

"At first it was a surprise, seeing the initial frogs in the area," says Larrea Saltos, who started observing their abundance about several years ago when one jumped on her palm as she was stepping out of her front door.

Environmental Consequences Stays Unknown

The sound isn't the fundamental problem, though. While the species has been in the islands for almost 30 years, scientists still know very little about its impact on the islands' delicately balanced terrestrial and aquatic environments.

On archipelagos, it is very typical for non-native species to prosper, as they have none of their enemies. The Galápagos has over sixteen hundred introduced species, many of which are seriously affecting the safety of its native ones.

A recent research suggests the non-native frogs are hungry insect eaters, and might be disproportionately eating uncommon insects found exclusively on the archipelago, or depleting the nutrition of the islands' uncommon birds, disrupting the food chain.

Unusual Traits and Control Challenges

The island amphibians have exhibited some atypical traits, including surviving in slightly salty water, which is rare for frogs.

Their development stage is also extremely inconsistent, with some larvae becoming frogs very quickly and others taking a long time: San José observed one which stayed as a larva in her laboratory for half a year.

"We truly don't know this part," she says, worried the larvae could be impacting the islands' freshwater, a very scarce commodity in the islands.

Techniques to control the frogs in the early 2000s were mostly ineffective. Park rangers tried capturing significant quantities by manual methods and slowly increasing the salinity of ponds in vain.

Studies suggests applying caffeine – which is highly toxic to frogs – or using electrocution could assist, but these methods aren't always secure for other rare Galápagos organisms.

Without solutions to more of the fundamental questions about their biology and impact, culling the frogs might not even be the correct way to proceed, says the biologist.

Financial Obstacles for Research

While she expects the increasing use of environmental DNA techniques and genetic analysis will help her team understand of the invasive species, funding for the project has been difficult to obtain.

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