Tegus on list of Sunshine State's most aggressive invasive species

This month, a two-foot tegu identified as No. 1125 scampered through a bramble of thick sawgrass in the southern Everglades, a tiny backpack carrying a GPS tracker attached to her back and a string of purple party beads secured around her belly.


First spotted in the wild near a Homestead trailer park and rock pits in south Miami-Dade County less than a decade ago, the black and white reptiles have staked their claim as Florida's latest, most aggressive invasive species.

With their numbers climbing, they have expanded their range from the south end of Miami-Dade, west to Collier County and north to Hillsborough County. In 2009, when biologists first began trapping them in South Florida, they captured just 13 tegus. This year that number is fast approaching 500.

Such a rapid rise has wildlife biologists starting to ask a scary question: could tegus be the next Burmese python?
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"You'd have to rate them right up there," said University of Florida biologist Frank Mazzotti, who is part of a team trapping and tracking tegus but worries the reptiles have slipped beyond "containment zones."

"We have not been able to muster enough resources to deal with this problem," he said.

A team of University of Florida wildlife biologists is tracking a large invasive lizard in the Everglades that is threatening native birds, alligators and crocodiles, raising fears that they could be as destructive as the Burmese python.

Tegus are still readily available in pet stores.

Trapping and selling is legal — just last week Mazzotti and another UF wildlife biologist, Mike Rockford, came across a private trap off Southwest 424th Street, not far from their research traps.
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The state, which is working with UF and shares the cost with the South Florida Water Management District, is paying closer attention, said Kristen Penney Sommers, a section leader for the Florida Fish and Wildlife Conservation Commission.

But so far, the state is not planning to restrict tegus, she said.

"We know we are seeing them in areas where we weren't seeing them before, which would indicate there's more of them," she said.

To get a handle on the threat, biologists enlisted, or rather drafted, No. 1125.

The female tegu was captured last month by two biologists on Mazzotti's team, Lindsey Garner and Kyle Allen, in a trap on a rutted dirt road that runs through state lands in the southern Everglades, not far from a home for delinquent boys on Southwest 424th Street.

The area has been the epicenter of the tegu invasion.

Like with pythons, biologists believe the first tegu - native to Argentina, Bolivia, Brazil and Paraguay — was either a freed or escaped pet.

Tegus live in burrows and forage around water, so they found plenty of hospitable habitat in the marshes that border Florida City and Homestead.

They also eat almost anything: fruits, seeds, eggs, insects and small mammals.

When biologists opened up the guts of 124 captured along the Miami's urban fringes, they found frogs, toads, lizards, snakes and turtles.

But unlike pythons, hardy tegus can survive in the cold, as low as 35 degrees, meaning they could potentially threaten a broader range of native species.

A population of endangered Cape Sable seaside sparrows is less than ten miles from where the UF team is trapping tegus. Last week, the team found two American crocodile nests off the same dirt road where they trap tegus.

"There is no debate about tegus. All of Florida is at risk," Mazzotti said.

For the last year, Garner and Allen have been crisscrossing the southern Everglades trapping the tegus in attempt to contain them and monitor eight females released with trackers. At any given time, the team has between 30 and 40 traps, along with camouflaged cameras, scattered along the roads, tucked into the sawgrass in areas that look especially tegu-ish.

They use raccoon traps, like Have-A-Hearts, baited with chicken eggs from the supermarket. Allen said they experimented with papaya, turkey meat and cat food, keeping tabs on the capture-to-bait ratio.

"These are what get the highest catch effort," Allen said holding up an egg.

The team also tried out smaller traps - PVC pipe covered with chicken wiring - to catch younger tegus sneaking into the larger traps to steal eggs.

During winters, tegu slip into a kind of reptile hibernation called brumation. So - deer flies be damned - Garner and Allen spend every week day in spring and summer checking traps. They have clearly gotten better at trapping - a fact that Mazzotti said can not be ignored in analyzing numbers.

They average five catches a day. Their record remains one week in April when they caught 31tegus in three days.

"For me, the most surprising thing is just how many there are," said Allen, who said the biggest tegu was nearly five feet long.

Aside from removing the lizards from the wild, trapping is also helping them understand how the tegus are adapting to South Florida.

In a study published earlier this year, researchers with the U.S. Geological Survey looked at the relationship between tegus and altered habitat. Researchers know that Florida has more invasive species partly because its native forests and wetlands, that might otherwise have withstood marauding Brazilian peppers, Australian pines, Nile monitors and rock pythons, have been weakened by being drained, paved and subdivided.

The study found that tegus on the periphery of the Everglades moved more than those in its dense middle. Where there were roads and drained wetlands, tegus moved more freely. They also found tegus liked to hang out near trees and shrubs, suggesting they may be hunting bird eggs.

Another scary fact: tegus are capable of prolific breeding. In April, Garner and Allen discovered two nests, each holding 27 eggs. Mazzotti said tegus aren't necessarily social, but tend to clump together. More than once, his team have found multiple tegus in a single trap. They also know females guard nests.

Armed with this information, they are now tracking the eight females - in white, pink and blue party beads to better identify those photographed - hoping to detect a pattern to better manage trapping efforts. While biologists suspect numbers are going up, they still have no good population estimates, Mazzotti said, meaning they can't even be sure whether trapping is slowing down growth. More importantly, the state needs to formalize a plan for dealing with invasive species in the future. The state's "rapid" assessment of the tegu took two years, he said.

On Wednesday, Sommers said the team will give an update on efforts at the Everglades Invasive Species Summit in Davie, the yearly meeting where biologists from state and federal agencies meet with researchers and others to coordinate efforts.

"It's a legitimate question: what affect are we having," Mazzotti said. "If the number we're trapping is too small, the population will compensate. If we're not trapping enough females, we may not be having the desired affects…..We have convincing data on python's impact on mammals. We don't have the same on tegus."

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