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On her daily walk to the research facility, scientist the researcher crouches near a small water body covered by dense plants and collects a compact green sound device.

The device was left there through the night to capture the distinctive croaks of the Fowler's snouted treefrog, recognized by local researchers as an invasive species with effects that experts are just beginning to comprehend.

Although abounding with unique wildlife – such as centuries-old large turtles, marine iguanas, and the well-known birds that sparked Charles Darwin's theory of evolution – the Galápagos archipelago off the coast of Ecuador had long remained free of frogs and toads.

During the 1990s, this changed. Several small amphibians traveled from mainland the mainland to the islands, likely as hitchhikers on transport vessels.

DNA studies indicate that, through time, there have been multiple accidental introductions to the islands, and the frogs now have a strong presence on several islands: multiple locations.

The population is growing so quickly that researchers have been finding it difficult to keep track, estimating populations in the millions on every island, across developed and agricultural areas, but also in the conservation Galápagos national park.

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

They calculated six thousand frogs in a single pond. "Our estimates are still very low," states the researcher. "I am pretty sure there are additional numbers."

Acoustic Chaos and Rising Worries

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

For the researchers, their nightly mating calls are useful in estimating their existence in remote areas, using recorders like the one near the office.

But local farmers 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 Santa Cruz.

"At first it was a shock, observing the first frogs in the region," says the farmer, who started observing their large numbers about three years ago when one leaped on her palm as she was walking out of her front door.

Ecological Impact Stays Unknown

The noise isn't the fundamental problem, however. While the species has been in the Galápagos for almost three decades, scientists still know limited information 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 Galápagos has over sixteen hundred invasive species, many of which are seriously disrupting the survival of its native ones.

A recent study indicates the invasive frogs are hungry bug eaters, and might be unevenly eating uncommon insects found exclusively on the islands, or reducing the nutrition of the region's uncommon birds, disrupting the ecosystem balance.

Unique Characteristics and Management Difficulties

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

Their development process is also extremely variable, with some larvae becoming frogs very rapidly and others taking a long time: San José observed one which stayed as a larva in her lab for six months.

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

Techniques to control the amphibians in the beginning of the century were largely unsuccessful. Conservation officers tried collecting significant quantities by hand and gradually raising the salt content of lagoons in vain.

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

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

Funding Challenges for Research

While she hopes the increasing use of environmental DNA techniques and DNA examination will help her group understand of the invasive species, funding for the research has been difficult to come by.

"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 manage."