🔗 Share this article Galápagos Lacked Any Indigenous Amphibians. Then Countless Numbers of Amphibians Made Their Home On her daily commute to the scientific station, scientist the researcher crouches near a small pond surrounded by dense plants and collects a small green audio device. The device was left there overnight to capture the characteristic calls of the Scinax quinquefasciatus, known by Galápagos scientists as an invasive species with effects that scientists are just beginning to understand. Although teeming with remarkable wildlife – including centuries-old giant tortoises, marine lizards, and the well-known birds that sparked Darwin's theory of evolution – the island chain off the shoreline of Ecuador had historically been devoid of amphibians. In the late 1990s, this shifted. Several small amphibians made their way from mainland the mainland to the islands, probably as stowaways on transport vessels. Fowler’s snouted tree frogs came in the 1990s and have taken hold on multiple Galápagos islands. DNA studies indicate that, through time, there have been multiple accidental arrivals to the islands, and the amphibians now have a firm foothold on several locations: Isabela and Santa Cruz. The population is expanding so rapidly that scientists have been finding it difficult to monitor, estimating numbers in the hundreds of thousands on each island, across urban and agricultural areas, but also in the protected Galápagos national park. When the biologist marked frogs and attempted to find them in the following week and a half, she could locate just one marked frog occasionally, suggesting their populations were massive. They calculated six thousand frogs in a solitary pond. "Our estimates are still very low," states San José. "I am pretty sure there are even more." Acoustic Chaos and Growing Concerns The amphibians' abundance is evident from the acoustic chaos they cause. "The number of frogs and the sound – it's truly incredible," says San José. For the scientists, their nocturnal vocalizations are helpful in determining their existence in far-flung areas, using audio devices like the one outside San José's workplace. But local agricultural workers say the sounds are so raucous they prevent sleep at night. "During the rainy period, I regularly hear their croaks and they're extremely loud," says Jadira Larrea Saltos from the island. "Initially it was a surprise, observing the initial frogs in the region," says the farmer, who started noticing their abundance about several years ago when one jumped on her palm as she was stepping out of her front door. Ecological Impact Stays Unknown The sound isn't the primary problem, though. While the amphibians has been in the Galápagos for almost 30 years, scientists still know very little about its impact on the archipelago's precariously balanced land and water environments. Researchers are finding out more about the amphibians, including that they can stay as tadpoles for as long as six months. On archipelagos, it is very common for non-native species to thrive, as they have few of their enemies. The Galápagos counts over sixteen hundred invasive types, many of which are seriously disrupting the safety of its endemic ones. A 2020 research suggests the invasive frogs are voracious bug eaters, and might be unevenly eating uncommon insects found exclusively on the islands, or depleting the food sources of the islands' uncommon avian species, disrupting the ecosystem balance. Unusual Traits and Control Challenges The Galápagos frogs have exhibited some atypical traits, including surviving in slightly salty water, which is rare for frogs. Their metamorphosis process is also extremely inconsistent, with some larvae becoming frogs very rapidly and others taking a long time: the researcher observed one which stayed as a larva in her lab for six months. "We really don't know this part," she says, concerned the larvae could be impacting the islands' clean water, a very limited resource in Galápagos. More research is required to establish the best way to manage the amphibians without harming other organisms. Techniques to control the frogs in the beginning of the century were largely ineffective. Conservation officers tried collecting significant quantities by manual methods and slowly increasing the salt content of ponds in vain. Research indicates spraying coffee – which is extremely poisonous to amphibians – or using electrical methods could help, but these methods aren't necessarily secure for other uncommon Galápagos organisms. Lacking solutions to more of the basic issues about their lifestyle and effect, removing the frogs might not even be the correct way to advance, says the biologist. Financial Obstacles for Research While she expects the growing use of environmental DNA techniques and genetic examination will assist her group make sense of the invader, funding for the research has been difficult to obtain. "Everyone wants to give funding for preserving frogs," says San José. "But it's more difficult to find funding for an invasive frog that you might want to manage."