A Hungry Little SquatterBy: Rachel Nuwer
the creature thrashing around in a metal trap they had laid off a weedy dirt road. Inside it was
what some biologists consider the most troublesome invasive species in the Everglades: not a
Burmese python, but a 24-inch lizard, the Argentine black and white tegu.
It thumped its long tail like a snare drum — a tactic the species uses to shift predators’ attention
to that expendable appendage (it can grow a new one). Ms. Vinci, a wildlife biologist, was not
fooled. Wiping her brow in the 91-degree Florida heat, she attached a cloth bag to the end of the
cage and then carefully opened it, shooing the tegu inside.
As she knotted the bag, the animal went limp, playing dead. That didn’t work either: The tegu,
along with three others trapped earlier, would be taking a one-way trip out of the marsh, in
Miami-Dade County, and to the University of Florida’s Fort Lauderdale Research and Education
Tegus (usually pronounced TAY-goos) originally came here from South America through the pet
trade. Although Dr. Mazzotti prefers cats, he can understand why people like them: They are
smart, attractive animals, patterned like an abstract Moroccan rug. They have a nasty bite, but
with enough handling, they grow docile. “They’ll crawl on you — the reptile version of
interacting,” Dr. Mazzotti said.
But like pythons and other invasive species first brought here as pets, tegus eventually found
their way into the natural environment. Once they were unleashed in Florida’s wetlands, the
warm weather, bountiful food and absence of natural predators allowed them to thrive.
Wild tegus were first spotted in 2008, scuttling around a trailer park in Florida City, south of
Miami. But their range quickly expanded, spilling into the nearby Everglades, where they took
advantage of a smorgasbord of native wildlife. The lizards have a taste for eggs — both reptile
and bird — but they will also eat small mammals, insects and fruit. “Everything they get their
jaws around, plant or animal, they seem to swallow,” Dr. Mazzotti said.
A wildlife biologist whose accent gives away his Long Island roots, Dr. Mazzotti, 65, has
worked in Florida’s swamps for nearly 40 years. He had hoped to become a marine biologist but
scrapped that plan after discovering he had crippling seasickness. On a class trip to Big Cypress
National Park, he discovered a new calling: the Everglades.
For decades, he focused his research on alligators and threatened American crocodiles, earning
the nickname “the croc doc.” But since the early 2000s, Dr. Mazzotti has turned his attention to
the dozens of coldblooded species that have invaded the Everglades, including pythons, Nile
monitor lizards, Cuban tree frogs and black spiny-tailed iguanas.
Still, he said, of all the invaders, tegus worry him the most. They are more tolerant of cold than
many reptiles, meaning they have a larger potential habitat range. Rare freezes in southern
Florida kill nine out of 10 pythons, but tegus have successfully overwintered as far north as
Panama City, on the Florida Panhandle. (The Florida Fish and Wildlife Conservation
Commission managed to wipe out that population before it could expand.) The invasion has two centers, Florida City and Riverview, southeast of Tampa. Some of the lizards escaped from
captivity or were set free by owners who no longer wanted them; scientists and officials suspect
many were released by reptile breeders on the theory that harvesting them in the wild is cheaper
than breeding them in captivity.
“We know in those two areas they’re reproducing,” said Kristen Sommers, the head of exotic
species at the Florida wildlife agency. “We’re trying to get a better handle on what’s going on in
those areas, and we’ve really been increasing our trapping efforts.”
Dr. Mazzotti is reluctant to cite specific population figures, but he notes that the number of tegus
trapped around Florida City has risen to 400 a year, from just 13 in 2009 and 21 in 2010; he
thinks that represents less than 10 percent of the total population. A time-lapse map he created to
track the invasion — yellow dots for traps, red for those that catch a tegu — resembles the
progression of a disease outbreak.
Dr. Mazzotti and his colleagues take turns hitting the field each day, checking about 30 live traps
that they bait with chicken eggs. They have also fitted several tegus with small transmitters to
track their movements, and set up cameras to monitor the species’ colonization patterns. While
the biologists focus on the invasion’s front lines, they have also recruited private trappers to
capture the lizards in well-established core areas, nicknamed “trailer park” and “rock pit.”
Rodney Irwin, a licensed tegu trapper in nearby Homestead, has collaborated with the
researchers for three years. “Everyone’s on the same page about one thing,” he said. “We’ve got
to do something about these aggressive predators. Argentine tegus are taking out animals that I
grew up with — that my dad and my grandfather grew up with.”
Rather than kill the invaders, Mr. Irwin chooses to sell them to pet dealers. “It would have been
easy for me to put on my redneck hat, grab my rifle and just start killing them,” he said. “But I
spent time with them and just fell in love.” He has more than 200 tegus and says almost all of his
shipments go out of state. Prices vary from $40 to $140.
Dr. Mazzotti said he did not care whether captured tegus were euthanized or returned to the pet
trade (preferably to destinations “like Montana or Mongolia,” he added dryly). His primary
concern is removing tegus from the environment, and he says he thinks the invasion can still be
contained or even stopped. But that will require acting quickly.
Tegu populations are creeping east toward Turkey Point Nuclear Generating Station, where
threatened American crocodiles nest; west into Everglades National Park, populated by protected
Liguus tree snails and endangered Cape Sable seaside sparrows; and south to Crocodile Lake
National Wildlife Refuge, the home of the endangered Key Largo wood rat and cotton mouse,
and more crocodiles. These rare animals or their eggs are potential prey for tegus, Dr. Mazzotti
said, adding, “We cannot wait until an invasive species demonstrates negative impacts to act,
because then it’s too late.”
Despite the threats to native wildlife, he said, efforts to tackle the tegu problem are lagging.
Attention is still primarily focused on pythons, even though that species is already so well
established that there is little hope of eliminating it. “I get weary not so much of fighting the battle to protect our resources,” he said, “but of our seeming inability to learn from past