🔗 Share this article The Galápagos Islands Had No Native Amphibians. Then Hundreds of Thousands of Frogs Made Their Home During her daily walk to the research facility, scientist the researcher stoops near a shallow water body surrounded by dense plants and collects a compact green sound device. She had placed there overnight to record the characteristic croaks of the Fowler's snouted treefrog, recognized by local scientists as an invasive species with consequences that scientists are just beginning to comprehend. Despite teeming with remarkable wildlife – including centuries-old large turtles, swimming iguanas, and the famous birds that sparked Darwin's theory of evolution – the island chain near the coast of South America had historically been devoid of amphibians. In the late 1990s, this changed. Several small tree frogs traveled from continental Ecuador to the islands, likely as stowaways on cargo ships. The invasive species came in the 90s 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 strong presence on several islands: multiple locations. The numbers is growing so rapidly that researchers have been finding it difficult to keep track, estimating numbers in the millions on each island, across urban and agricultural areas, but also in the protected Galápagos national park. When the biologist tagged amphibians and attempted to recapture them in the following week and a half, she could locate only a single tagged frog occasionally, suggesting their numbers were massive. They estimated six thousand frogs in a solitary pond. "Our estimates are still very low," says San José. "I'm pretty sure there are additional numbers." Acoustic Chaos and Growing Concerns The amphibians' abundance is clear from the sound disruption they cause. "The amount of frogs and the noise – it's really insane," comments the scientist. For the scientists, their nocturnal mating calls are helpful in determining their existence in remote areas, using audio devices like the one outside San José's workplace. But nearby farmers say the sounds are so raucous they prevent sleep at night. "In the wet season, I constantly hear their calls and they're extremely loud," says a local coffee farmer from Santa Cruz. "At first it was a shock, seeing the initial frogs in the region," says the farmer, who started observing their abundance about several years ago when one jumped on her palm as she was walking out of her front door. Ecological Impact Remains Unknown The noise isn't the fundamental problem, though. While the amphibians has been in the Galápagos for nearly 30 years, scientists still know limited information about its effect on the archipelago's delicately balanced terrestrial and aquatic environments. Scientists are discovering more about the amphibians, including that they can remain as tadpoles for as long as half a year. On islands, it is very common for non-native species to thrive, as they have few of their natural predators. The Galápagos has 1,645 introduced species, many of which are significantly affecting the survival of its native ones. A recent study suggests the invasive frogs are voracious bug consumers, and might be unevenly eating uncommon bugs found only on the islands, or depleting the nutrition of the islands' uncommon avian species, affecting the food chain. Unique Characteristics and Control Challenges The island amphibians have shown some unusual traits, including surviving in brackish water, which is rare for frogs. Their metamorphosis process is also highly inconsistent, with some larvae turning into frogs very quickly and others taking a extended period: San José observed one which stayed as a tadpole in her laboratory for half a year. "We really don't know this aspect," she says, concerned the larvae could be impacting the islands' clean water, a very limited commodity in Galápagos. More research is needed to establish the best way to control the amphibians without affecting other species. Techniques to control the amphibians in the beginning of the century were mostly ineffective. Park rangers tried collecting significant quantities by manual methods and slowly increasing the salinity of lagoons in vain. Studies indicates spraying caffeine – which is extremely toxic to amphibians – or using electrocution could help, but these methods aren't always secure for other uncommon island species. Lacking answers to more of the basic questions about their biology and effect, removing the frogs might not even be the right way to proceed, says San José. Financial Obstacles for Research While she hopes the increasing use of environmental DNA techniques and genetic analysis will help her team understand of the invasive species, financial support for the project has been hard to come by. "Everyone wants to give funding for protecting frogs," says San José. "But it's harder to find financial backing for an invasive frog that you might want to control."