Devin Edmonds isn’t like most amphibian hobbyists. For one thing, he’s now a trained herpetologist, studying frogs and turtles as a doctoral student at the University of Illinois Urbana-Champaign. But as an amateur back in 2006, he did something bold for the love of frogs that changed the trajectory of his life, not to mention the frogs’. 

“I have been keeping and breeding amphibians as a hobby since I was young, and in college I saved up for a ticket to go to Madagascar to see some of the frogs I kept at home in the wild,” said Edmonds, doctoral candidate in the Department of Natural Resources and Environmental Sciences, part of the College of Agricultural, Consumer and Environmental Sciences at U. of I. Edmonds is also affiliated with the Illinois Natural History Survey, part of the Prairie Research Institute.

“I was walking down the road in Andasibe showing people photos of the golden mantella frog to see if they knew it and could take me to see them in the wild. I ran into Edupsie, the brother of Association Mitsinjo's president and a guide, and he said he knew where to go. So we spent the next week traveling around the area to see and photograph the frogs I liked.”

When Edmonds showed Edupsie photos of his frog room back in Wisconsin, it sparked the idea that would eventually bring Edmonds back to Madagascar for six years. Edmonds went home and graduated, then sought funding to help Association Mitsinjo, a conservation and eco-tourism organization, set up a conservation breeding program for native amphibians. The facility would become the national breeding program for Madagascar.

Around 2014, while living near Andasibe-Mantadia National Park, Edmonds started getting emails about a toad that concerned local scientific and conservation communities. Warty, yellow, and toxic, the Asian black-spined toad had been spotted near Toamasina, Madagascar’s Indian Ocean seaport and second largest city. 

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Invasive elsewhere, the toads were immediately recognized as a potential conservation nightmare for Madagascar, a world-renowned biodiversity hotspot. Armed with a potent toxin released when bitten, the toad can gobble its prey and reproduce wildly with little interference from predators.

Edmonds and his Mitsinjo colleagues jumped in, volunteering to do surveys for the invasive toad, including interviews with local residents.

“Toamasina has about 300,000 residents, many of whom live without basic necessities like reliable clean water and safe housing,” Edmonds said. “Our sampling sites were in urban areas as well as rural sites outside the city, and we’d have to sample at night because the toads are nocturnal. 

“We would talk with people and then they would go around with me and the team from Mitsinjo, plus staff from the Madagascar Fauna and Flora Group. We would all be walking around at night, shining our flashlights to try and see if toads were there. The highest densities of toads that I remember seeing were at the dump, which is a big smoldering trash pile outside of town and a pretty unpleasant place to do amphibian surveys.” 

When the team found toads, they’d take a tissue sample before euthanizing them. These samples turned out to be a pivotal part of a new genomic study of Asian black-spined toads that reconstructs historical routes of invasion — likely along the Maritime Silk Road — and reveals that Madagascar toads actually represent a new species.  

“It is interesting to think about these toads hitching a ride on a ship from India to Indonesia a thousand years ago, showing how people have been moving animals around the world for a lot longer than just the last century or two,” said Edmonds, a co-author on the Nature Communications study.

Although Asian toads in Madagascar were thought to belong to the same species (Duttaphrynus melanostictus) as those invading in Indonesian biodiversity hotspots, the genomic analysis revealed they had morphed into an as-yet-unnamed novel species.

“This is important because it shows all the hidden biological diversity that remains to be described on the planet,” Edmonds said. “This toad is widespread and common, but without this study, it would have just been thought of as one species. Morphologically there is some diversity and previous work had looked at genetics, but without the genomic work we wouldn’t have been able to see this toad is really two different toads.”

Distinguishing the new species from Duttaphrynus melanostictus could make a difference in terms of managing the invasive threat. If it has evolved different habitat preferences, reproductive output, or toxicity levels, wildlife managers may need to adjust their approach to control. Since Edmonds’ initial surveys, the toad has spread to impact at least 550 square kilometers (about 136,000 acres), with local wildlife managers struggling to keep up. 

Although Edmonds’ time with the toads was brief — he moved back to the U.S. in 2016 and started a master’s program at U. of I. the following year — the invaders still weigh on his mind. His current studies focus on Madagascar’s endangered harlequin mantella frog, Mantella cowanii, which means he frequently returns to the island and the frog genus that first stole his heart in 2006.

“Although Mantella cowanii is not directly threatened by this invasive toad, more broadly it is a threatened amphibian species, and invasive species are among the threats all amphibians have to deal with in Madagascar and elsewhere.”

Edmonds’ work with the harlequin mantella frog is helping to fulfill Madagascar’s national conservation strategy for the endangered species, in part by determining which of the remote, isolated populations are at greatest risk of being lost. Edmonds’ aim, as always, is to learn as much as possible about these frogs in order to help them survive and, ultimately, thrive.

Edmonds is a two-time ACES International Graduate Grant recipient for his work on the harlequin mantella frog. He is advised by Michael Dreslik, associate research scientist at INHS and research associate professor in NRES. Edmonds plans to continue studying amphibians and the best approaches for their conservation after finishing his doctoral studies in 2025.

The Nature Communications study, “Speciation and historical invasions of the Asian black-spined toad (Duttaphrynus melanostictus)” [DOI:10.1038/s41467-024-54933-4], is available by request.