🔗 Share this article The Galápagos Islands Lacked Any Native Amphibians. Then Hundreds of Thousands of Amphibians Invaded On her daily walk to the scientific station, scientist the researcher crouches near a shallow pond surrounded by thick vegetation and collects a compact plastic sound device. The device was left there overnight to record the distinctive croaks of the Fowler's snouted treefrog, known by Galápagos researchers as an non-native threat with consequences that scientists are just beginning to understand. Despite abounding with remarkable wildlife – including centuries-old giant tortoises, swimming lizards, and the famous finches that inspired Charles Darwin's evolutionary theory – the island chain near the shoreline of Ecuador had long remained devoid of frogs and toads. During the 1990s, this shifted. Several small tree frogs made their way from mainland Ecuador to the islands, probably as stowaways on cargo ships. The invasive species came in the 1990s and have taken hold on multiple Galápagos islands. DNA research suggest that, over the years, there have been multiple unintentional arrivals to the archipelago, and the frogs now have a firm foothold on several locations: Isabela and Santa Cruz. The numbers is growing so rapidly that scientists have been finding it difficult to keep track, calculating numbers in the hundreds of thousands on every island, across urban and agricultural areas, but also in the conservation Galápagos national park. When the biologist marked amphibians and attempted to recapture them in the subsequent week and a half, she could locate only a single tagged frog occasionally, suggesting their numbers were massive. They estimated 6,000 frogs in a single pond. "The calculations are still very low," says the researcher. "I am pretty sure there are additional numbers." Acoustic Chaos and Growing Concerns The amphibians' proliferation is evident from the acoustic disruption they create. "The number of frogs and the sound – it's truly insane," says San José. For the scientists, their nightly vocalizations are helpful in estimating their presence in far-flung areas, using audio devices like the one near the workplace. But nearby farmers say the sounds are so raucous they keep them up at night. "During the wet season, I regularly hear their croaks and they're really loud," says Jadira Larrea Saltos from Santa Cruz. "Initially it was a shock, observing the initial frogs in the area," says Larrea Saltos, who started observing their large numbers about three years ago when one jumped on her hand as she was stepping out of her house. Environmental Consequences Remains Unknown The noise isn't the fundamental problem, however. While the amphibians has been in the Galápagos for almost three decades, experts still know limited information about its effect on the islands' precariously balanced land and water ecosystems. Scientists are finding out more about the frogs, including that they can remain as tadpoles for as long as half a year. On islands, it is very typical for non-native organisms to thrive, as they have none of their enemies. The islands counts over sixteen hundred invasive species, many of which are seriously affecting the survival of its endemic ones. A 2020 study indicates the non-native amphibians are hungry bug eaters, and might be disproportionately consuming uncommon bugs found only on the archipelago, or depleting the nutrition of the islands' uncommon birds, affecting the food chain. Unique Characteristics and Management Difficulties The island amphibians have shown some unusual traits, including surviving 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 long time: the researcher observed one which stayed as a tadpole in her laboratory for six months. "We truly don't know this part," she says, concerned the larvae could be affecting the islands' freshwater, a very limited resource in Galápagos. Additional studies is needed to determine the best way to control the frogs without affecting other species. Techniques to curb the frogs in the early 2000s were mostly ineffective. Park rangers tried collecting significant quantities by manual methods and gradually raising the salt content of lagoons in vain. Studies indicates applying coffee – which is extremely toxic to amphibians – or using electrical methods could help, but these methods aren't always secure for other rare island species. Lacking solutions to more of the fundamental issues about their lifestyle and impact, culling the amphibians might not even be the right way to advance, says the biologist. Financial Obstacles for Research While she hopes the growing use of environmental DNA techniques and DNA examination will assist her team make sense of the invader, funding for the project has been difficult to obtain. "Everyone wants to give support for protecting frogs," says San José. "But it's harder to find financial backing for an introduced frog that you might want to manage."