🔗 Share this article The Galápagos Islands Lacked Any Native Amphibians. Until Countless Numbers of Amphibians Invaded On her daily walk to the research facility, biologist the researcher crouches near a shallow pond surrounded by thick plants and collects a small plastic audio device. The device was left there through the night to record the characteristic croaks of the Scinax quinquefasciatus, recognized by Galápagos researchers as an non-native species with effects that scientists are just beginning to understand. Although teeming with unique wildlife – such as centuries-old giant tortoises, marine iguanas, and the well-known birds that sparked Darwin's evolutionary theory – the Galápagos archipelago off the coast of South America had historically been free of frogs and toads. In the late 1990s, this changed. Several tiny amphibians traveled from continental the mainland to the islands, likely as hitchhikers on cargo ships. Fowler’s snouted tree frogs arrived in the 90s and have become established on multiple Galápagos islands. DNA research suggest that, over the years, there have been repeated accidental arrivals to the archipelago, and the amphibians now have a strong presence on several islands: Isabela and Santa Cruz. The numbers is expanding so quickly that scientists have been struggling to keep track, estimating numbers in the millions on every island, across urban and farming areas, but also in the conservation natural reserve. When the biologist marked amphibians and attempted to find them in the following week and a half, she could locate only a single marked frog from time to time, indicating their numbers were enormous. They estimated six thousand frogs in a solitary pond. "The calculations are still very low," says the researcher. "I'm pretty sure there are additional numbers." Acoustic Chaos and Rising Worries The amphibians' proliferation is clear from the acoustic disruption they create. "The number of frogs and the sound – it's truly incredible," says San José. For the researchers, their nightly vocalizations are helpful in estimating their presence in remote areas, using recorders like the one outside San José's office. But local farmers say the sounds are so raucous they prevent sleep at night. "In the rainy period, I constantly hear their croaks and they're extremely loud," says a local coffee farmer from the island. "At first it was a surprise, seeing the initial frogs in the region," says the farmer, who started noticing their abundance about three years ago when one jumped on her palm as she was stepping out of her house. Environmental Consequences Remains Unknown The sound isn't the primary problem, though. While the amphibians has been in the islands for nearly three decades, scientists still know very little about its impact on the archipelago's delicately balanced terrestrial and aquatic environments. Scientists are finding out more about the frogs, including that they can stay as tadpoles for as long as six months. On islands, it is very common for invasive organisms to prosper, as they have few of their enemies. The islands has over sixteen hundred introduced species, many of which are seriously disrupting the safety of its endemic ones. A 2020 study indicates the non-native frogs are voracious insect eaters, and might be disproportionately eating uncommon insects found exclusively on the islands, or reducing the nutrition of the islands' uncommon avian species, disrupting the food chain. Unique Characteristics and Management Difficulties The island frogs have shown some atypical characteristics, including living in slightly salty water, which is rare for amphibians. Their metamorphosis process is also highly inconsistent, with some tadpoles becoming frogs very quickly and others taking a long time: San José observed one which stayed as a tadpole in her lab for half a year. "We really don't know this part," she says, worried the larvae could be impacting the islands' clean water, a very limited commodity in the islands. Additional studies is needed to determine the optimal way to manage the frogs without harming other species. Techniques to control the frogs in the beginning of the century were mostly unsuccessful. Park rangers tried collecting significant quantities by manual methods and gradually increasing the salt content of lagoons in vain. Research suggests applying coffee – which is highly poisonous to amphibians – or using electrical methods could assist, but these methods aren't necessarily secure for other uncommon island organisms. Without answers to more of the fundamental issues about their lifestyle and effect, removing the amphibians might not even be the right way to advance, says San José. Financial Obstacles for Research While she hopes the increasing use of environmental DNA techniques and DNA examination will assist her team make sense of the invasive species, funding for the research has been difficult to come by. "Everybody wants to give support for preserving frogs," says the researcher. "But it's more difficult to find financial backing for an invasive frog that you might want to manage."