🔗 Share this article Galápagos Lacked Any Indigenous Amphibians. Until Countless Numbers of Amphibians Made Their Home On her regular walk to the scientific station, scientist the researcher stoops near a small pond covered by thick plants and collects a small plastic audio device. The device was left there overnight to capture the distinctive calls of the Scinax quinquefasciatus, known by Galápagos scientists as an non-native species with consequences that experts are just beginning to understand. Despite teeming with remarkable animals – including ancient large turtles, marine lizards, and the well-known finches that sparked Charles Darwin's theory of evolution – the island chain off the coast of Ecuador had long remained devoid of amphibians. In the late 1990s, this changed. Several small tree frogs made their way from continental Ecuador to the islands, probably as stowaways on cargo ships. The invasive species arrived in the 1990s and have become established on Isabela and Santa Cruz islands. Genetic studies indicate that, over the years, there have been multiple accidental arrivals to the islands, and the frogs now have a firm presence on several islands: Isabela and Santa Cruz. The numbers is expanding so rapidly that researchers have been struggling to monitor, calculating numbers in the millions on each island, across developed and agricultural areas, but also in the conservation natural reserve. When San José tagged frogs and attempted to find them in the subsequent 10 days, she could find just one tagged frog occasionally, indicating their numbers were enormous. They calculated six thousand frogs in a solitary pond. "The calculations are still very conservative," states San José. "I am quite certain there are additional numbers." Acoustic Chaos and Rising Worries The amphibians' abundance is clear from the acoustic chaos they cause. "The amount of frogs and the noise – it's truly insane," says San José. For the researchers, their nightly mating calls are useful in determining their presence in far-flung areas, using recorders like the one outside San José's office. But local agricultural workers say the sounds are so loud they keep them up at night. "During the rainy period, I constantly hear their calls and they're really loud," says Jadira Larrea Saltos from Santa Cruz. "Initially it was a shock, seeing the initial frogs in the area," says the farmer, who started noticing their large numbers about three years ago when one jumped on her palm as she was stepping out of her house. Ecological Impact Remains Unclear The sound isn't the fundamental problem, however. While the amphibians has been in the Galápagos for nearly 30 years, scientists still know limited information about its effect on the islands' delicately balanced terrestrial and aquatic ecosystems. Scientists are finding out more about the amphibians, including that they can stay as larvae for as long as half a year. On archipelagos, it is very typical for invasive organisms to prosper, as they have none of their natural predators. The Galápagos has over sixteen hundred introduced species, many of which are seriously affecting the survival of its endemic ones. A 2020 study suggests the invasive frogs are hungry bug consumers, and might be unevenly eating rare bugs found exclusively on the archipelago, or depleting the food sources of the islands' uncommon birds, affecting the ecosystem balance. Unique Characteristics and Control Challenges The Galápagos amphibians have shown some atypical characteristics, including surviving in slightly salty water, which is uncommon for amphibians. Their metamorphosis stage is also extremely variable, with some tadpoles turning into frogs very rapidly and others taking a long time: the researcher witnessed one which remained as a larva in her lab for six months. "We really don't know this part," she says, concerned the tadpoles could be impacting the islands' freshwater, a very scarce commodity in the islands. More research is needed to establish the best way to control the frogs without affecting other species. Techniques to curb the frogs in the early 2000s were largely ineffective. Conservation officers tried capturing significant quantities by manual methods and slowly raising the salinity of lagoons in vain. Studies indicates spraying caffeine – which is highly poisonous to frogs – or using electrical methods could help, but these methods aren't always secure for other uncommon Galápagos organisms. Lacking solutions to more of the fundamental questions about their biology and impact, removing the amphibians might not even be the right way to proceed, says San José. Funding Challenges for Study While she expects the increasing use of environmental DNA techniques and genetic examination will assist her team understand of the invasive species, funding for the research has been difficult to obtain. "Everybody wants to give funding for preserving frogs," says San José. "But it's more difficult to find funding for an invasive frog that you might want to control."