🔗 Share this article Galápagos Had No Native Amphibians. Until Countless Numbers of Amphibians Arrived During her daily commute to the scientific station, scientist Miriam San José crouches near a shallow pond covered by thick plants and retrieves a small plastic sound recorder. She had placed there overnight to record the distinctive croaks of the Scinax quinquefasciatus, known by Galápagos scientists as an invasive species with consequences that scientists are just beginning to comprehend. Although abounding with remarkable wildlife – including centuries-old large turtles, marine lizards, and the well-known birds that inspired Charles Darwin's evolutionary theory – the island chain near the coast of Ecuador had historically been devoid of amphibians. During the 1990s, this changed. Several small tree frogs traveled from continental the mainland to the islands, likely as hitchhikers on cargo ships. Fowler’s snouted tree frogs came in the 90s and have become established on Isabela and Santa Cruz islands. Genetic studies indicate that, through time, there have been repeated accidental introductions to the archipelago, and the amphibians now have a firm presence on several islands: Isabela and Santa Cruz. The numbers is growing so rapidly that researchers have been struggling to monitor, estimating numbers in the millions on every island, across urban and farming areas, but also in the conservation Galápagos national park. When San José tagged frogs and attempted to find them in the subsequent 10 days, she could find just one marked frog from time to time, suggesting their populations were enormous. They calculated six thousand frogs in a single pond. "Our estimates are still very conservative," states San José. "I'm quite certain there are additional numbers." Deafening Noise and Growing Concerns The amphibians' abundance is clear from the sound disruption they cause. "The amount of frogs and the sound – it's really incredible," says San José. For the scientists, their nocturnal vocalizations are useful in estimating their existence in remote areas, using recorders like the one outside the workplace. But nearby agricultural workers say the sounds are so loud they keep them up at night. "In the rainy period, I constantly hear their croaks and they're extremely loud," says Jadira Larrea Saltos from Santa Cruz. "Initially it was a surprise, observing the first frogs in the area," says Larrea Saltos, who started noticing their abundance about several years ago when one jumped on her palm as she was stepping out of her house. Ecological Impact Stays Unknown The noise isn't the primary problem, though. While the species has been in the Galápagos for nearly three decades, experts still know limited information about its impact on the islands' delicately balanced land and water environments. Scientists are discovering more about the amphibians, including that they can remain as larvae for as long as six months. On islands, it is very typical for non-native species to prosper, as they have none of their natural predators. The Galápagos counts 1,645 introduced types, many of which are seriously disrupting the survival of its endemic ones. A recent research indicates the non-native frogs are voracious insect eaters, and might be disproportionately eating rare bugs found only on the archipelago, or depleting the nutrition of the islands' uncommon birds, disrupting the ecosystem balance. Unusual Traits and Control Challenges The island frogs have exhibited some unusual characteristics, including living in brackish water, which is rare for amphibians. Their metamorphosis process is also highly inconsistent, with some tadpoles becoming frogs very quickly and others taking a long time: San José observed one which remained as a larva in her laboratory for six months. "We truly don't know this aspect," she says, worried the larvae could be affecting the region's clean water, a very limited commodity in Galápagos. Additional studies is needed to determine the optimal way to manage the amphibians without affecting other species. Methods to control the frogs in the beginning of the century were mostly ineffective. Conservation officers tried collecting significant quantities by hand and gradually increasing the salt content of lagoons in without success. Research suggests spraying caffeine – which is highly toxic to amphibians – or using electrocution could assist, but these methods aren't always safe for other uncommon island species. Lacking solutions to more of the fundamental questions about their lifestyle and effect, removing the frogs might not even be the correct way to advance, says the biologist. Funding Challenges for Research While she expects the increasing use of environmental DNA methods and DNA analysis will assist her team make sense of the invasive species, financial support for the research has been hard to obtain. "Everybody wants to give support for preserving frogs," says San José. "But it's more difficult to find financial backing for an introduced frog that you might want to control."