"Right now, they're considered exotics -- non-native animals that aren't supposed to be here," Congdon told ABC News today. "But if they breed and grow enough to the point that they're causing damage, they could be considered an invasive species."
Capybaras were first accidentally introduced to forests in northern Florida after five of them escaped a research facility in the early '90s, said Congdon, an assistant professor at the Bethune-Cookman University in Daytona Beach, Florida, who warned about the potential threat of the species at an animal behavior conference earlier this month.
Since then, Congdon said there have been dozens of capybaras sighted over the past few years in a state park near the facility -- including about 50 in 2008.
"They're definitely breeding, and there's certainly more than 50 of them there by now," she said.
As long as the capybara population doesn't grow and stays within the state park's confines, Congdon said she believes they will not pose a problem. However, they could begin breeding at more rapid rates and start spreading to agricultural areas.
Congdon explained that the dog-sized rodents are "very social" and resilient. They warn each other of predators coming and females work together and actually help nurse each other's young.
"If they start growing and expanding, they could start eating crops," she said. "They're known to eat corn and sugar cane in Brazil. That could cause significant economic damage for the state."
Congdon and her students will be studying the animals and trying to come up with a population estimate for the next few months, she said.
"At this point, we're just trying to prevent them from becoming an invasive species, and we don't necessarily know the solution right now," she said. "It could be that we have to remove large males or breeding females. It may be possible to fence in the park so they simple can't escape and control their spread that way."
The "most extreme solution" would be to kill some of them, Congdon said.
"That's the question: How do you humanely stop the spread?" she said. "And it's a fine line for those of us studying these animals. I love them, and they're my favorite animal in the planet, but at the same time, it may be necessary to remove them from here."
For now, Congdon said she will be working hard to do more research on the animal and find potential preventive solutions.