🔗 Share this article The Galápagos Islands Had No Indigenous Amphibians. Then Countless Numbers of Amphibians Made Their Home During her regular walk to the scientific station, biologist the researcher crouches near a shallow water body surrounded by dense vegetation and retrieves a small plastic sound recorder. She had placed there overnight to record the distinctive croaks of the Fowler's snouted treefrog, recognized by Galápagos researchers as an invasive threat with consequences that scientists are just beginning to comprehend. Despite teeming with unique animals – such as centuries-old giant tortoises, marine iguanas, and the well-known birds that inspired Darwin's evolutionary theory – the island chain off the shoreline of South America had historically been free of frogs and toads. In the late 1990s, this changed. Several tiny tree frogs made their way from continental Ecuador to the islands, probably as stowaways on transport vessels. The invasive species came in the 1990s and have taken hold on Isabela and Santa Cruz islands. Genetic research indicate that, through time, there have been multiple unintentional introductions to the islands, and the amphibians now have a firm presence on two islands: multiple locations. The numbers is expanding so quickly that scientists have been finding it difficult to keep track, estimating populations in the millions on every island, across developed and agricultural areas, but also in the conservation natural reserve. When the biologist tagged frogs and attempted to recapture them in the following week and a half, she could find just one marked frog from time to time, indicating their numbers were enormous. They estimated six thousand frogs in a single pond. "The calculations are still very low," states the researcher. "I'm pretty sure there are even more." Acoustic Chaos and Growing Concerns The amphibians' proliferation is clear from the sound disruption they cause. "The amount of frogs and the noise – it's truly incredible," says the scientist. For the researchers, their nocturnal mating calls are useful in estimating their existence in remote areas, using audio devices like the one near the workplace. But local agricultural workers say the sounds are so loud they prevent sleep at night. "In the rainy period, I regularly hear their croaks and they're extremely loud," says Jadira Larrea Saltos from the island. "At first it was a shock, seeing the first frogs in the region," says the farmer, who started observing their abundance about three years ago when one jumped on her palm as she was stepping out of her front door. Environmental Consequences Remains Unclear The sound isn't the fundamental problem, however. While the species has been in the Galápagos for almost three decades, experts still know very little about its impact on the islands' precariously balanced terrestrial and aquatic environments. Scientists are finding out more about the frogs, including that they can remain as larvae for as long as six months. On islands, it is very typical for invasive species to thrive, as they have none of their natural predators. The Galápagos counts 1,645 invasive types, many of which are seriously disrupting the safety of its native ones. A recent research indicates the invasive frogs are voracious insect eaters, and might be unevenly consuming uncommon insects found only on the islands, or reducing the nutrition of the region's uncommon birds, disrupting the food chain. Unique Characteristics and Management Difficulties The Galápagos frogs have exhibited some unusual characteristics, including living in slightly salty water, which is uncommon for amphibians. Their metamorphosis process is also highly inconsistent, with some larvae turning into frogs very rapidly and others taking a long time: the researcher observed one which remained as a tadpole in her lab for six months. "We truly don't know this aspect," she says, concerned the tadpoles could be affecting the islands' clean water, a very scarce commodity in the islands. Additional studies is required to determine the optimal way to manage the amphibians without harming other organisms. Techniques to control the amphibians in the beginning of the century were largely ineffective. Conservation officers tried collecting large numbers by hand and gradually increasing the salinity of ponds in without success. Research suggests spraying coffee – which is highly poisonous to frogs – or using electrocution could help, but these methods aren't always secure for other uncommon Galápagos species. Lacking solutions to more of the fundamental issues about their biology and impact, culling the amphibians might not even be the right way to proceed, says San José. Funding Challenges for Research While she expects the growing use of environmental DNA methods and DNA examination will assist her group understand of the invasive species, financial support for the research has been difficult to obtain. "Everybody wants to give support for protecting frogs," says San José. "But it's harder to find funding for an introduced frog that you might want to manage."