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On her regular commute to the research facility, scientist Miriam San José stoops near a shallow water body covered by dense vegetation and retrieves a small green audio device.

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

Despite abounding with remarkable wildlife – such as ancient large turtles, marine lizards, and the well-known finches that sparked Darwin's evolutionary theory – the island chain off the coast of Ecuador had historically been free of frogs and toads.

In the late 1990s, this changed. Some tiny amphibians traveled from mainland the mainland to the islands, probably as stowaways on transport vessels.

Genetic research indicate that, through time, there have been multiple unintentional arrivals to the islands, and the frogs now have a strong presence on two locations: Isabela and Santa Cruz.

The population is expanding so rapidly that researchers have been struggling to monitor, estimating numbers in the millions on every island, across developed and farming areas, but also in the conservation natural reserve.

When the biologist tagged frogs and attempted to recapture them in the subsequent week and a half, she could find just one tagged frog from time to time, suggesting their numbers were massive.

They calculated six thousand frogs in a solitary pond. "The calculations are still very low," states San José. "I'm quite certain there are additional numbers."

Deafening Noise and Rising Worries

The amphibians' proliferation is clear from the sound disruption they cause. "The amount of frogs and the sound – it's truly incredible," says San José.

For the researchers, their nocturnal vocalizations are useful in estimating their existence in far-flung areas, using recorders like the one near San José's office.

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

"During the rainy period, I constantly hear their croaks and they're really loud," says Jadira Larrea Saltos from the island.

"At first it was a surprise, observing the first frogs in the region," says the farmer, who started observing their large numbers about several years ago when one jumped on her hand as she was stepping out of her house.

Environmental Consequences Remains Unclear

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

On archipelagos, it is very common for invasive species to prosper, as they have none of their natural predators. The islands has over sixteen hundred invasive species, many of which are seriously disrupting the survival of its native ones.

A 2020 research suggests the non-native amphibians are hungry bug consumers, and might be unevenly eating rare bugs found only on the islands, or reducing the food sources of the islands' uncommon birds, disrupting the food chain.

Unusual Traits and Management Difficulties

The Galápagos frogs have exhibited some unusual characteristics, including living in slightly salty water, which is uncommon for frogs.

Their development stage is also extremely inconsistent, with some larvae becoming frogs very rapidly and others taking a extended period: San José witnessed one which stayed as a tadpole in her laboratory for six months.

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

Methods to control the frogs in the beginning of the century were mostly ineffective. Conservation officers tried collecting significant quantities by manual methods and slowly raising the salinity of lagoons in without success.

Studies suggests applying caffeine – which is highly toxic to frogs – or using electrical methods could help, but these methods aren't always secure for other uncommon island organisms.

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

Funding Challenges for Study

While she hopes the increasing use of environmental DNA methods and DNA examination will assist her team make sense of the invader, financial support for the project has been difficult to come by.

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