🔗 Share this article Galápagos Lacked Any Native Amphibians. Until Hundreds of Thousands of Frogs Invaded During her daily commute to the research facility, biologist the researcher stoops near a shallow pond covered by dense vegetation and retrieves a small green sound recorder. She had placed there overnight to capture the characteristic croaks of the Fowler's snouted treefrog, known by Galápagos scientists as an non-native species with consequences that scientists are just beginning to comprehend. Despite abounding with remarkable wildlife – including ancient large turtles, marine lizards, and the famous birds that sparked Charles Darwin's theory of evolution – the Galápagos archipelago off the shoreline of South America had long remained devoid of amphibians. During the 1990s, this shifted. Some small amphibians traveled from mainland Ecuador to the islands, likely as hitchhikers on transport vessels. The invasive species arrived in the 1990s and have taken hold on Isabela and Santa Cruz islands. Genetic studies suggest that, through time, there have been repeated unintentional arrivals to the islands, and the frogs now have a firm presence on several locations: multiple locations. The population is expanding so quickly that researchers have been struggling to keep track, calculating numbers in the millions on every island, across urban and agricultural areas, but also in the conservation natural reserve. When San José tagged frogs and attempted to find them in the following week and a half, she could find just one tagged frog from time to time, suggesting their populations were enormous. They estimated 6,000 frogs in a solitary pond. "Our estimates are still very conservative," states San José. "I'm quite certain there are additional numbers." Acoustic Chaos and Growing Concerns The amphibians' proliferation is clear from the acoustic chaos they create. "The number of frogs and the noise – it's truly incredible," comments San José. For the scientists, their nightly mating calls are helpful in estimating their existence in far-flung areas, using recorders like the one near the office. But local agricultural workers say the calls are so raucous they keep them up at night. "During the wet season, I constantly hear their calls and they're extremely loud," says Jadira Larrea Saltos from Santa Cruz. "Initially it was a surprise, observing 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 front door. Ecological Impact Stays Unclear The noise isn't the primary problem, however. While the species has been in the islands for almost 30 years, experts still know limited information about its effect on the archipelago's delicately balanced land and water environments. Researchers are discovering more about the frogs, including that they can stay as larvae for as long as six months. On archipelagos, it is very common for invasive organisms to thrive, as they have none of their enemies. The Galápagos counts over sixteen hundred introduced types, many of which are significantly affecting the safety of its endemic ones. A recent study suggests the invasive frogs are hungry bug eaters, and might be disproportionately eating uncommon bugs found exclusively on the islands, or reducing the food sources of the region's uncommon birds, affecting the food chain. Unusual Traits and Management Difficulties The Galápagos frogs have exhibited some unusual characteristics, including living in brackish water, which is rare for amphibians. Their metamorphosis process is also extremely inconsistent, with some tadpoles becoming frogs very quickly and others taking a long time: the researcher observed one which stayed as a tadpole in her lab for six months. "We truly don't know this aspect," she says, worried the tadpoles could be impacting the region's freshwater, a very limited resource in Galápagos. More research is required to establish the best way to manage the frogs without affecting other organisms. Methods to control the frogs in the early 2000s were largely unsuccessful. Conservation officers tried collecting significant quantities by hand and slowly increasing the salt content of ponds in without success. Research indicates spraying caffeine – which is extremely poisonous to amphibians – or using electrical methods could help, but these approaches aren't necessarily safe for other rare island organisms. Lacking answers to more of the fundamental issues about their lifestyle and impact, culling the amphibians might not even be the correct way to proceed, says San José. Financial Obstacles for Study While she hopes the growing use of environmental DNA techniques and DNA examination will help her group make sense of the invader, funding for the project has been hard to obtain. "Everybody wants to give funding for protecting frogs," says the researcher. "But it's harder to find financial backing for an invasive frog that you might want to control."