🔗 Share this article Galápagos Lacked Any Native Amphibians. Then Hundreds of Thousands of Frogs Arrived On her daily commute to the research facility, biologist Miriam San José crouches near a small water body surrounded by dense vegetation and collects a small green sound device. The device was left there overnight to capture the distinctive calls of the Scinax quinquefasciatus, recognized by Galápagos researchers as an non-native threat with consequences that experts are starting to understand. Despite abounding with remarkable wildlife – such as ancient giant tortoises, marine lizards, and the well-known finches that inspired Darwin's theory of evolution – the island chain near the shoreline of Ecuador had historically been free of frogs and toads. During the 1990s, this changed. Several small amphibians traveled from mainland the mainland to the archipelago, probably as hitchhikers on transport vessels. Fowler’s snouted tree frogs came in the 90s and have become established on multiple Galápagos islands. Genetic research indicate that, through time, there have been multiple accidental introductions to the archipelago, and the frogs now have a firm foothold on several locations: Isabela and Santa Cruz. The numbers is expanding so rapidly that scientists have been finding it difficult to monitor, calculating numbers in the millions on each island, across developed and farming areas, but also in the protected Galápagos national park. When San José marked frogs and attempted to recapture them in the subsequent 10 days, she could find just one tagged frog from time to time, indicating their numbers were enormous. They calculated six thousand frogs in a single pond. "Our estimates are still very conservative," states the researcher. "I'm pretty sure there are even more." Acoustic Chaos and Rising Worries The amphibians' proliferation is evident from the sound disruption they create. "The number of frogs and the sound – it's truly incredible," says the scientist. For the researchers, their nocturnal vocalizations are helpful in estimating their presence in remote areas, using recorders like the one near the workplace. But nearby farmers say the calls are so loud they keep them up at night. "In the rainy period, I constantly hear their calls and they're extremely loud," says a local coffee farmer from Santa Cruz. "Initially it was a shock, seeing the first frogs in the region," says the farmer, who started observing their large numbers about three years ago when one leaped on her palm as she was stepping out of her house. Environmental Consequences Stays Unclear The sound isn't the primary problem, though. While the amphibians has been in the Galápagos for nearly 30 years, experts still know limited information about its effect on the archipelago's delicately balanced land and water ecosystems. Researchers are discovering more about the frogs, including that they can remain as larvae for as long as half a year. On islands, it is very typical for invasive organisms to prosper, as they have none of their natural predators. The islands counts over sixteen hundred introduced species, many of which are seriously disrupting the safety of its native ones. A 2020 study indicates the non-native frogs are hungry insect eaters, and might be disproportionately eating rare bugs found only on the archipelago, or depleting the food sources of the islands' rare birds, affecting the ecosystem balance. Unique Characteristics and Management Difficulties The Galápagos amphibians have exhibited some atypical traits, including living in brackish water, which is rare for frogs. Their metamorphosis stage is also extremely inconsistent, with some tadpoles becoming 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 truly don't know this part," she says, concerned the tadpoles could be impacting the islands' clean water, a very scarce commodity in the islands. Additional studies is needed to determine the best way to manage the amphibians without affecting other organisms. Methods to control the frogs in the early 2000s were largely ineffective. Park rangers tried collecting significant quantities by manual methods and gradually increasing the salinity of ponds in vain. Research indicates applying caffeine – which is extremely poisonous to amphibians – or using electrocution 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, culling the amphibians might not even be the correct way to advance, says the biologist. Financial Obstacles for Study While she expects the increasing use of eDNA techniques and genetic analysis will assist her team understand of the invader, financial support for the research has been difficult to obtain. "Everyone wants to give support for preserving frogs," says the researcher. "But it's more difficult to find financial backing for an invasive frog that you might want to manage."