🔗 Share this article The Galápagos Islands Lacked Any Indigenous Amphibians. Until Hundreds of Thousands of Amphibians Invaded During her daily commute to the research facility, biologist Miriam San José crouches near a shallow pond covered by thick vegetation and collects a compact green audio device. She had placed there through the night to record the characteristic croaks of the Scinax quinquefasciatus, recognized by Galápagos researchers as an non-native species with effects that experts are just beginning to understand. Despite abounding with remarkable animals – such as ancient giant tortoises, marine lizards, and the well-known birds that inspired Darwin's evolutionary theory – the Galápagos archipelago off the coast of South America had historically been devoid of frogs and toads. During the 1990s, this changed. Several small tree frogs traveled from mainland the mainland to the islands, probably as stowaways on cargo ships. Fowler’s snouted tree frogs arrived in the 1990s and have become established on multiple Galápagos islands. Genetic studies indicate that, through time, there have been multiple unintentional arrivals to the archipelago, and the amphibians now have a firm foothold on two islands: Isabela and Santa Cruz. The population is growing so rapidly that researchers have been struggling to monitor, estimating populations in the hundreds of thousands on every island, across urban and agricultural areas, but also in the protected natural reserve. When San José marked frogs and attempted to recapture them in the following 10 days, she could locate just one marked frog occasionally, indicating their numbers were massive. They estimated six thousand frogs in a single pond. "Our estimates are still very low," states San José. "I'm quite certain there are even more." Acoustic Chaos and Rising Worries The frogs' abundance is clear from the sound disruption they cause. "The number of frogs and the noise – it's truly incredible," comments San José. For the researchers, their nightly vocalizations are useful in determining their presence in remote areas, using audio devices like the one outside the workplace. But nearby farmers say the sounds are so loud they prevent sleep at night. "In the rainy period, I constantly hear their calls and they're extremely loud," says Jadira Larrea Saltos from the island. "At first it was a surprise, seeing the first frogs in the region," says Larrea Saltos, who started observing their abundance about three years ago when one jumped on her hand as she was walking out of her front door. Environmental Consequences Remains Unclear The sound isn't the fundamental problem, however. While the amphibians has been in the Galápagos for nearly 30 years, experts still know limited information about its impact on the archipelago's precariously balanced terrestrial and aquatic environments. Scientists are discovering more about the frogs, including that they can remain as tadpoles for as long as six months. On islands, it is very typical for invasive species to prosper, as they have few of their enemies. The Galápagos counts over sixteen hundred introduced types, many of which are significantly disrupting the safety of its endemic ones. A recent research indicates the invasive frogs are voracious insect consumers, and might be disproportionately consuming rare bugs found exclusively on the islands, or depleting the nutrition of the islands' uncommon birds, affecting the food chain. Unique Characteristics and Control Challenges The island amphibians have shown some unusual characteristics, including living in slightly salty water, which is uncommon for amphibians. Their metamorphosis stage is also highly variable, with some larvae becoming frogs very rapidly and others taking a long time: San José witnessed one which stayed as a tadpole in her laboratory for half a year. "We really don't know this aspect," she says, worried the tadpoles could be affecting the islands' clean water, a very scarce commodity in the islands. Additional studies is needed to establish the best way to manage the frogs without affecting other species. Techniques to control the amphibians in the beginning of the century were largely unsuccessful. Park rangers tried collecting significant quantities by hand and gradually raising the salt content of lagoons in without success. Studies suggests applying coffee – which is highly toxic to frogs – or using electrocution could help, but these methods aren't always safe for other uncommon Galápagos species. Lacking solutions to more of the basic issues about their lifestyle and effect, removing the amphibians might not even be the correct way to proceed, says San José. Financial Obstacles for Study While she expects the growing use of environmental DNA methods and genetic analysis will help her group make sense of the invasive species, financial support for the research 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."