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On her daily walk to the research facility, biologist the researcher stoops near a small pond covered by thick plants and retrieves a small green audio recorder.

She had placed there overnight to capture the characteristic calls of the Fowler's snouted treefrog, recognized by local scientists as an invasive threat with effects that scientists are starting to comprehend.

Despite teeming with unique animals – such as ancient large turtles, marine iguanas, and the famous finches that sparked Charles Darwin's evolutionary theory – the island chain near the shoreline of Ecuador had historically been devoid of amphibians.

In the late 1990s, this shifted. Several tiny amphibians made their way from mainland the mainland to the islands, probably as hitchhikers on transport vessels.

Genetic studies suggest that, over the years, there have been repeated unintentional introductions to the islands, and the amphibians now have a firm presence on several locations: Isabela and Santa Cruz.

The population is growing so rapidly that scientists have been struggling to monitor, estimating populations in the millions on every island, across developed and agricultural areas, but also in the conservation natural reserve.

When San José marked amphibians and attempted to find them in the subsequent 10 days, she could locate only a single tagged frog from time to time, suggesting their numbers were enormous.

They calculated six thousand frogs in a single pond. "Our estimates are still very conservative," states San José. "I'm pretty sure there are additional numbers."

Acoustic Chaos and Rising Worries

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

For the scientists, their nocturnal vocalizations are useful in determining their existence in far-flung areas, using recorders like the one outside the office.

But local agricultural workers say the sounds are so raucous they prevent sleep at night.

"During the rainy period, I regularly hear their calls and they're extremely loud," says a local coffee farmer from the island.

"At first it was a shock, seeing the initial frogs in the area," says the farmer, who started noticing their abundance about several years ago when one jumped on her palm as she was walking out of her front door.

Environmental Consequences Stays Unclear

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

On islands, it is very typical for non-native species to prosper, as they have none of their enemies. The Galápagos has 1,645 invasive types, many of which are significantly affecting the safety of its native ones.

A 2020 research indicates the invasive amphibians are voracious insect eaters, and might be disproportionately consuming rare bugs found exclusively on the archipelago, or depleting the food sources of the region's rare avian species, disrupting the food chain.

Unique Characteristics and Management Difficulties

The Galápagos frogs have shown some unusual traits, including living in brackish water, which is uncommon for amphibians.

Their development process 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 laboratory for six months.

"We truly don't know this part," she says, worried the tadpoles could be impacting the region's clean water, a very limited commodity in the islands.

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

Research indicates spraying caffeine – which is extremely toxic to frogs – or using electrocution could help, but these methods aren't necessarily secure for other rare island species.

Lacking answers to more of the basic questions about their lifestyle and impact, removing the frogs might not even be the right way to proceed, says San José.

Funding Challenges for Study

While she hopes the increasing use of environmental DNA techniques and genetic examination will assist her group understand of the invader, financial support for the research has been difficult to obtain.

"Everybody wants to give funding for protecting frogs," says San José. "But it's harder to find financial backing for an invasive frog that you might want to control."