RIVERVIEW — Jimmy Doane did a doubletake the first time he saw the giant lizard ambling nearby.
"It was like a baby alligator," he said. "I thought, 'What in the world!' "
Doane is no longer startled by the creatures he now knows as the Argentine black and white tegu. That is because the lizards make periodic appearances at his workplace on the southern end of Balm Riverview Road in Riverview.
Doane said the critters camp outside the maintenance department at Goodson Farms where he is the shop foreman. Sometimes, they stroll inside, and occasionally they steal a meal from the cat bowls.
His most recent sighting was March 28, when one of the lizards parked in a grassy area behind the shop to soak up the sun's rays.
"There are many out there," Doane said. "I don't like them. They're not good for the environment."
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Wildlife experts said Doane is right.
The lizards, which can grow to just over 4 feet, are thriving in sparsely populated areas of Riverview, Lithia and Wimauma in southern Hillsborough County.
They also agree Doane is correct in saying the native South American lizards can harm Florida's ecosystem.
"Any nonnative species that establishes its population in the environment is going to have an effect up and down the food chain," said Gary Morse, a spokesman for the Florida Fish and Wildlife Conservation Commission.
Morse said the tegu has a presence in southern Hillsborough but is not so prolific that you will see one on every corner.
"I've seen reports that they are taking over," Morse said. "That's not true. They are there. They are a concern."
Morse said the tegu poses a problem because it eats native plants and animals. He also warned that they could become a bigger nuisance because of their appetite.
"They are so voracious they could pose a problem," he said.
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Todd Campbell, an associate professor in the University of Tampa biology department said it is unknown how many tegus are out there. But, he added, it's probably not in the hundreds and more likely in the thousands.
Campbell said the state definitely has to do something about the tegu, which he called a "top predator." He said it's a tough task because the lizards are spread out in rural areas.
Campbell said there have been sightings over a broad range of territory, such as the RVR Horse Rescue off Rhodine Road, the Balm Boyette Scrub Preserve on Boyette Balm Road and the Alafia River State Park off County Road 39.
Most troubling, said Campbell, a reptile and amphibian expert who has been studying the tegu for nearly a decade, is that the lizard loves eggs, which could be detrimental to animals that lay eggs.
Campbell is thrilled the commission hired one of his students, Tessie Offner, to continue to study the tegu.
"They need to be managed," he said. "They are going to eat all of our native species."
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Rick Gibson, who works with Doane at Goodson Farms' maintenance shop, said he has never seen an emaciated tegu.
"They're big and healthy, so they are eating something," he said.
Fish and wildlife commission officials are trapping tegu and are troubled by what they find during necropsies. Their bellies are filled with birds, rats, mice, and bird and gopher tortoise eggs. Morse said they likely are eating smaller tortoises and other animals, too.
The killing of native species is troubling because it impacts the entire environment, Morse said.
"They are all important to the ecosystem," he said.
Morse cited the gopher tortoise as an example. The tortoise digs deep burrows that are shared by 100 or more other animals. If the tegu damages the tortoise population, then other species will be impacted, too.
In addition to Hillsborough, the commission said tegu populations have also popped in other Florida locales, such as neighboring Polk County and also Miami-Dade County.
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No one knows how the tegu ended up here or other spots in Florida. Most likely, they were pets and either escaped or were released by their owners.
Campbell said baby lizards and snakes grow up just like kittens and puppies, so be sure you want one for the long run before you buy or adopt.
He begged owners of exotic species to stop releasing animals they no longer want into the wild.
Instead, Campbell encouraged people to take advantage of "amnesty days," when pet owners can give up their exotic animals, no questions asked.
"Prevention is the way to solve this problem," he said.
The commission is studying the tegu's impact on the environment. They want to know the range of where they live, what they're eating, how fast they're growing and their impact on native species.
Morse said it's highly unlikely they'll rid the area of the tegu. But, maybe, their research will help find the animal's "Achilles' heel."
"There may be a way to manage a population," he said. "Keep it under control."