The huge amphibians, which grow as large as dinner plates, are the focus of University of Georgia graduate student Caitlin Rumrill’s research into how the species reacts to heavy metals.
The creatures, also called “marine toads” or “cane toads,” are native to South and Central America, but have become established as an invasive species in many areas, including Florida.
That’s where Rumrill, a Massachusetts native, went to collect the 70 giant toads needed for her project.
“We got some of them riding around on a golf course,” she said. “The biggest one came out of a lady’s yard where she was feeding a bunch of cats. The toads just come up and eat the cat food.”
At the ecology lab within the Savannah River Site nuclear complex, the giant toads are kept in a secure area, inside a greenhouse – and under lock and key.
The species is problematic because it has toxic skin that can kill cats and dogs, has few predators and tends to eat almost anything, including native toads and frogs that get in its way.
“They compete for resources and available space, which is an issue for other amphibians,” Rumrill said.
Her project, which includes comparitive studies of native Southern toads, is part of a research effort to gauge the giant toads’ ability to survive in areas impacted by contamination, especially metals.
“I’m focusing on copper,” she said. “I’m interested in whether the invasive cane toad is more or less tolerant of this metal than a native toad.”
The theory is that the resilient giant toad is more tolerant to heavy metal stresses than native species. “That might be one of the reasons behind their success,” she said.
Although copper is a necessary trace metal, and is widely used in fertilizer and construction, even a slightly elevated concentration can lead to health effects, she said.
Her project is expected to take about a year.