🔗 Share this article Galápagos Had No Native Amphibians. Then Hundreds of Thousands of Amphibians Made Their Home On her regular commute to the research facility, biologist Miriam San José stoops near a small pond surrounded by dense plants and collects a small green audio recorder. She had placed there overnight to record the distinctive croaks of the Scinax quinquefasciatus, recognized by local scientists as an non-native species with consequences that experts are just beginning to understand. Although teeming with unique animals – such as centuries-old giant tortoises, swimming iguanas, and the well-known birds that sparked Charles Darwin's theory of evolution – the island chain near the shoreline of Ecuador had historically been devoid of amphibians. During the 1990s, this changed. Some tiny amphibians made their way from continental the mainland to the archipelago, likely as stowaways on transport vessels. The invasive species arrived in the 90s and have taken hold on multiple Galápagos islands. DNA studies suggest that, over the years, there have been multiple unintentional introductions to the archipelago, and the frogs now have a firm foothold on several islands: Isabela and Santa Cruz. The population is expanding so quickly that scientists have been struggling to monitor, calculating populations in the millions on each island, across developed and agricultural areas, but also in the conservation natural reserve. When San José marked frogs and attempted to recapture them in the subsequent 10 days, she could find only a single tagged frog from time to time, suggesting their populations were massive. They estimated six thousand frogs in a single pond. "Our estimates are still very low," states San José. "I'm quite certain there are additional numbers." Acoustic Chaos and Rising Worries The frogs' abundance is evident from the acoustic chaos they cause. "The amount of frogs and the sound – it's really insane," says San José. For the scientists, their nightly vocalizations are helpful in determining their presence in far-flung areas, using recorders like the one near the workplace. But nearby agricultural workers say the calls are so loud they prevent sleep at night. "In the wet season, I constantly hear their calls and they're extremely loud," says a local coffee farmer from Santa Cruz. "Initially it was a surprise, observing the initial frogs in the area," says Larrea Saltos, who started noticing their abundance about several years ago when one jumped on her palm as she was walking out of her front door. Ecological Impact Remains Unclear The noise isn't the primary problem, though. While the amphibians has been in the islands for almost 30 years, experts still know very little about its impact on the archipelago's precariously balanced land and water environments. Scientists are finding out more about the amphibians, including that they can remain as larvae for as long as half a year. On islands, it is very typical for invasive organisms to thrive, as they have few of their enemies. The islands has over sixteen hundred introduced species, many of which are significantly affecting the survival of its endemic ones. A 2020 study suggests the invasive amphibians are voracious insect eaters, and might be unevenly eating uncommon bugs found only on the archipelago, or depleting the food sources of the islands' uncommon birds, affecting the food chain. Unique Characteristics and Control Challenges The Galápagos frogs have exhibited some atypical characteristics, including surviving in slightly salty water, which is uncommon for frogs. Their metamorphosis process is also extremely inconsistent, with some larvae turning into frogs very quickly and others taking a long time: San José witnessed one which remained as a larva in her lab for half a year. "We truly don't know this part," she says, concerned the tadpoles could be impacting the region's clean water, a very scarce commodity in Galápagos. Additional studies is needed to determine the best way to control the amphibians without affecting other species. Methods to curb the frogs in the beginning of the century were largely unsuccessful. Park rangers tried capturing significant quantities by manual methods and slowly raising the salt content of ponds in without success. Research suggests spraying caffeine – which is extremely toxic to frogs – or using electrical methods could assist, but these methods aren't always safe for other uncommon island species. Lacking solutions to more of the basic questions about their lifestyle and effect, removing the frogs might not even be the correct way to advance, says San José. Financial Obstacles for Research While she expects the growing use of eDNA techniques and DNA examination will assist her team make sense of the invader, financial support for the project has been hard 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 manage."