🔗 Share this article The Galápagos Islands Lacked Any Indigenous Amphibians. Then Hundreds of Thousands of Amphibians Made Their Home During her daily commute to the research facility, biologist the researcher crouches near a shallow pond surrounded by thick vegetation and retrieves a small plastic audio recorder. She had placed there overnight to capture the distinctive calls of the Fowler's snouted treefrog, recognized by Galápagos scientists as an invasive threat with consequences that experts are starting to understand. Despite abounding with remarkable wildlife – including centuries-old large turtles, swimming iguanas, and the well-known birds that inspired Darwin's evolutionary theory – the island chain off the shoreline of South America had historically been free of frogs and toads. During the 1990s, this shifted. Some tiny tree frogs traveled from mainland Ecuador to the archipelago, probably as stowaways on transport vessels. Fowler’s snouted tree frogs arrived in the 90s and have taken hold on multiple Galápagos islands. DNA research suggest that, through time, there have been multiple unintentional introductions to the archipelago, and the frogs now have a firm presence on several islands: Isabela and Santa Cruz. The numbers is growing so rapidly that scientists have been struggling to keep track, estimating numbers in the millions on each island, across developed and farming 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 only a single marked frog occasionally, indicating their populations were enormous. They estimated 6,000 frogs in a single pond. "Our estimates are still very conservative," says the researcher. "I am pretty sure there are even more." Acoustic Chaos and Growing Concerns The frogs' proliferation is clear from the acoustic chaos they cause. "The amount of frogs and the noise – it's truly incredible," comments San José. For the scientists, their nightly mating calls are helpful in determining their existence in far-flung areas, using audio devices like the one outside San José's office. But nearby agricultural workers say the calls are so loud they prevent sleep at night. "During the rainy period, I regularly hear their calls and they're extremely loud," says a local coffee farmer from Santa Cruz. "At first it was a shock, observing the first frogs in the area," says the farmer, who started noticing their abundance about three years ago when one jumped on her hand as she was walking out of her house. Ecological Impact Stays Unknown The sound isn't the fundamental problem, however. While the species has been in the Galápagos for nearly three decades, experts still know very little about its impact on the archipelago's delicately balanced terrestrial and aquatic environments. Researchers are finding out more about the amphibians, including that they can stay as tadpoles for as long as half a year. On islands, it is very common for invasive organisms to prosper, as they have none of their enemies. The Galápagos counts 1,645 invasive types, many of which are significantly affecting the safety of its endemic ones. A recent study indicates the non-native frogs are hungry bug eaters, and might be unevenly consuming uncommon insects found exclusively on the archipelago, or depleting the food sources of the region's rare birds, affecting the ecosystem balance. Unusual Traits and Control Challenges The island frogs have exhibited some atypical characteristics, including surviving in slightly salty water, which is uncommon for frogs. Their metamorphosis stage is also highly inconsistent, with some tadpoles becoming frogs very quickly and others taking a long time: the researcher observed one which remained as a tadpole in her lab for six months. "We really don't know this aspect," she says, concerned the larvae could be impacting the islands' freshwater, a very scarce commodity in the islands. Additional studies is required to establish the optimal way to control the amphibians without affecting other organisms. Techniques to curb the amphibians in the early 2000s were mostly ineffective. Park rangers tried capturing significant quantities by manual methods and gradually raising the salinity of ponds in vain. Research indicates applying caffeine – which is extremely poisonous to frogs – or using electrical methods could help, but these methods aren't always safe for other rare Galápagos species. Lacking answers to more of the basic issues about their biology and effect, removing the frogs might not even be the correct way to proceed, says the biologist. Funding Challenges for Study While she expects the increasing use of eDNA techniques and genetic analysis will help her group understand of the invasive species, financial support for the project has been difficult to obtain. "Everyone wants to give funding for preserving frogs," says the researcher. "But it's harder to find financial backing for an invasive frog that you might want to control."