🔗 Share this article Galápagos Had No Native Amphibians. Then Hundreds of Thousands of Frogs Invaded During her regular walk to the scientific station, scientist the researcher crouches near a small water body covered by thick plants and retrieves a compact plastic audio recorder. She had placed there through the night to capture the characteristic croaks of the Scinax quinquefasciatus, known by local researchers as an invasive threat with consequences that scientists are just beginning to understand. Although teeming with unique wildlife – including centuries-old giant tortoises, swimming iguanas, and the famous finches that inspired Darwin's theory of evolution – the island chain off the coast of Ecuador had historically been free of frogs and toads. During the 1990s, this shifted. Some tiny tree frogs traveled from mainland the mainland to the archipelago, probably as stowaways on cargo ships. Fowler’s snouted tree frogs came in the 1990s and have become established on Isabela and Santa Cruz islands. DNA research indicate that, over the years, there have been multiple unintentional arrivals to the archipelago, and the frogs now have a firm presence on two islands: multiple locations. The population is growing so quickly that researchers have been struggling to keep track, calculating numbers in the hundreds of thousands on each island, across developed and agricultural areas, but also in the conservation Galápagos national park. When San José tagged amphibians and attempted to recapture them in the subsequent week and a half, she could find only a single tagged frog from time to time, indicating their numbers were enormous. They calculated 6,000 frogs in a single pond. "Our estimates are still very conservative," says San José. "I am quite certain there are even more." Deafening Noise and Growing Concerns The amphibians' abundance is clear from the acoustic disruption they create. "The amount of frogs and the noise – it's really insane," says San José. For the scientists, their nightly mating calls are useful in determining their existence in remote areas, using recorders like the one outside the workplace. But local farmers say the sounds are so loud they prevent sleep at night. "During the rainy period, I regularly hear their calls and they're extremely loud," says Jadira Larrea Saltos from the island. "At first it was a shock, observing the first frogs in the area," says the farmer, who started observing their large numbers about several years ago when one leaped on her hand as she was stepping out of her front door. Ecological Impact Remains Unclear The noise isn't the primary problem, however. While the amphibians has been in the Galápagos for almost three decades, experts still know very little about its impact on the archipelago's precariously balanced land and water ecosystems. Researchers are discovering more about the amphibians, including that they can remain as tadpoles for as long as six months. On archipelagos, it is very common for non-native organisms to thrive, as they have few of their natural predators. The Galápagos counts 1,645 introduced types, many of which are seriously affecting the safety of its endemic ones. A recent research indicates the invasive frogs are hungry bug consumers, and might be disproportionately consuming uncommon insects found only on the archipelago, or reducing the nutrition of the region's rare avian species, disrupting the ecosystem balance. Unique Characteristics and Management Difficulties The island amphibians have shown some atypical traits, including living in slightly salty water, which is uncommon for frogs. Their development process is also extremely variable, with some tadpoles turning into frogs very rapidly and others taking a long time: San José observed one which stayed as a larva in her laboratory for six months. "We really don't know this part," she says, concerned the larvae could be affecting the region's freshwater, a very scarce commodity in the islands. More research is required to establish the optimal way to control the amphibians without affecting other organisms. Methods to curb the amphibians in the early 2000s were mostly unsuccessful. Conservation officers tried collecting large numbers by manual methods and slowly raising 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 methods aren't necessarily safe for other uncommon Galápagos species. Lacking solutions to more of the basic questions about their lifestyle and impact, removing the amphibians might not even be the correct way to proceed, says the biologist. Financial Obstacles for Research While she expects the growing use of eDNA methods and DNA analysis will assist her group make sense of the invader, financial support for the project has been difficult to obtain. "Everyone wants to give support for preserving frogs," says the researcher. "But it's more difficult to find funding for an invasive frog that you might want to manage."