🔗 Share this article Galápagos Had No Indigenous Amphibians. Until Hundreds of Thousands of Frogs Made Their Home On her regular commute to the scientific station, scientist Miriam San José stoops near a shallow water body surrounded by thick plants and retrieves a small green audio recorder. The device was left there overnight to capture the characteristic calls of the Fowler's snouted treefrog, known by Galápagos scientists as an invasive threat with consequences that scientists are just beginning to understand. Despite abounding with remarkable animals – such as ancient large turtles, marine lizards, and the famous birds that inspired Darwin's evolutionary theory – the Galápagos archipelago off the coast of South America had long remained devoid of frogs and toads. During the 1990s, this shifted. Some tiny tree frogs made their way from continental the mainland to the archipelago, likely as stowaways on transport vessels. Fowler’s snouted tree frogs came in the 90s and have become established on multiple Galápagos islands. DNA research suggest that, through time, there have been multiple accidental arrivals to the archipelago, and the amphibians now have a firm presence on two locations: Isabela and Santa Cruz. The numbers is expanding so quickly that scientists have been struggling to keep track, calculating populations in the millions on every island, across developed and farming areas, but also in the conservation natural reserve. When San José tagged amphibians and attempted to find them in the following week and a half, she could find only a single marked frog from time to time, indicating their numbers were enormous. They calculated 6,000 frogs in a solitary pond. "The calculations are still very conservative," states the researcher. "I'm quite certain there are even more." Acoustic Chaos and Growing Concerns The amphibians' abundance is clear from the acoustic chaos they cause. "The number of frogs and the sound – it's truly incredible," says the scientist. For the researchers, their nocturnal mating calls are helpful in estimating their presence in remote areas, using recorders like the one outside the office. But nearby farmers say the sounds are so raucous they prevent sleep at night. "In the rainy period, I constantly hear their calls and they're really loud," says a local coffee farmer from Santa Cruz. "At first it was a surprise, seeing the initial frogs in the region," says Larrea Saltos, who started observing their large numbers about several years ago when one leaped on her hand as she was stepping out of her house. Ecological Impact Stays Unclear The noise isn't the fundamental problem, though. While the amphibians has been in the islands for almost three decades, experts still know limited information about its effect on the archipelago's delicately balanced terrestrial and aquatic environments. Researchers are finding out more about the frogs, including that they can stay as larvae for as long as half a year. On islands, it is very common for non-native organisms to thrive, as they have none of their enemies. The islands has over sixteen hundred introduced types, many of which are significantly affecting the safety of its endemic ones. A 2020 research suggests the invasive frogs are voracious insect consumers, and might be unevenly eating rare bugs found only on the archipelago, or depleting the food sources of the region's rare avian species, disrupting the ecosystem balance. Unique Characteristics and Management Difficulties The island amphibians have shown some atypical characteristics, including living in brackish water, which is rare for amphibians. Their development stage is also highly inconsistent, with some larvae turning into frogs very rapidly and others taking a long time: the researcher witnessed one which stayed as a larva in her laboratory for half a year. "We really don't know this part," she says, worried the tadpoles could be impacting the region's freshwater, a very scarce commodity in Galápagos. Additional studies is needed to determine the optimal way to manage the frogs without affecting other species. Techniques to curb the amphibians in the beginning of the century were largely ineffective. Park rangers tried capturing significant quantities by manual methods and slowly increasing the salinity of lagoons in vain. Studies suggests applying coffee – which is highly poisonous to frogs – or using electrical methods could help, but these approaches aren't necessarily safe for other uncommon island organisms. Without solutions to more of the basic questions about their biology and impact, culling the amphibians might not even be the right way to advance, says San José. Funding Challenges for Study While she expects the growing use of environmental DNA techniques and genetic analysis will assist her team make sense of the invasive species, funding for the research has been hard to come by. "Everyone wants to give funding for preserving frogs," says the researcher. "But it's more difficult to find funding for an introduced frog that you might want to manage."