🔗 Share this article The Galápagos Islands Had No Native Amphibians. Then Countless Numbers of Amphibians Invaded On her daily walk to the scientific station, biologist the researcher stoops near a shallow water body covered by thick plants and collects a compact plastic audio recorder. She had placed there through the night to record the characteristic calls of the Scinax quinquefasciatus, known by Galápagos researchers as an non-native threat with consequences that experts are just beginning to understand. Although teeming with remarkable wildlife – including centuries-old large turtles, swimming lizards, and the well-known finches that inspired Darwin's evolutionary theory – the Galápagos archipelago near the coast of Ecuador had historically been free of amphibians. During the 1990s, this shifted. Some tiny amphibians made their way from mainland Ecuador to the archipelago, likely as hitchhikers on cargo ships. Fowler’s snouted tree frogs arrived in the 90s and have taken hold on multiple Galápagos islands. DNA research suggest that, over the years, there have been repeated unintentional introductions to the islands, and the frogs now have a firm foothold on two islands: Isabela and Santa Cruz. The population is expanding so quickly that scientists have been finding it difficult to monitor, estimating numbers in the hundreds of thousands 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 locate only a single tagged frog from time to time, indicating their numbers were massive. They calculated six thousand frogs in a solitary pond. "Our estimates are still very conservative," states the researcher. "I am quite certain there are additional numbers." Deafening Noise and Growing Concerns The amphibians' abundance is evident from the acoustic chaos they create. "The number of frogs and the sound – it's really incredible," comments the scientist. For the scientists, their nocturnal vocalizations are helpful in estimating their presence in remote areas, using audio devices like the one outside San José's workplace. But nearby agricultural workers say the calls are so raucous they keep them up at night. "During the rainy period, I regularly hear their croaks and they're extremely loud," says Jadira Larrea Saltos from Santa Cruz. "At first it was a shock, seeing the first frogs in the area," says Larrea Saltos, who started observing their abundance about three years ago when one leaped on her hand as she was walking out of her house. Ecological Impact Stays Unclear The noise isn't the primary problem, however. While the species has been in the islands for almost three decades, experts still know limited information about its effect on the archipelago's delicately balanced terrestrial and aquatic environments. Researchers 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 organisms to prosper, as they have none of their enemies. The Galápagos has 1,645 introduced types, many of which are seriously disrupting the survival of its endemic ones. A recent study suggests the non-native amphibians are hungry insect consumers, and might be disproportionately consuming uncommon insects found exclusively on the archipelago, or reducing the nutrition of the region's uncommon birds, affecting the ecosystem balance. Unusual Traits and Management Difficulties The island frogs have exhibited some atypical traits, including living in brackish water, which is uncommon for frogs. Their development stage is also extremely variable, with some tadpoles becoming frogs very quickly and others taking a extended period: the researcher observed one which stayed as a larva in her lab for six months. "We really don't know this part," she says, worried the larvae could be affecting the islands' clean water, a very limited commodity in the islands. More research is needed to determine the best way to control the frogs without affecting other organisms. Techniques to curb the amphibians in the early 2000s were mostly ineffective. Conservation officers tried capturing significant quantities by hand and gradually raising the salinity of ponds in vain. Studies indicates applying caffeine – which is highly toxic to amphibians – or using electrocution could assist, but these methods aren't always safe for other rare island species. Lacking answers to more of the basic issues about their biology and impact, 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 environmental DNA methods and DNA analysis will assist her group make sense of the invasive species, financial support for the project has been difficult to obtain. "Everyone wants to give support for preserving frogs," says the researcher. "But it's harder to find financial backing for an invasive frog that you might want to manage."