Tegu lizards trapped in Miami-Dade
South Florida’s tegu hunters have news — some good, some not so good.
Trapping the invasive reptile, blamed for devouring endangered crocodile and bird eggs, grasshoppers, native fruits and even small mammals, along the southeast fringes of the Everglades could be working. In the past two years, University of Florida researchers say the rate of trapping, and the age of tegus trapped, in one targeted area is down. In population ecology that might indicate the well is running dry.
At the same time, sightings to the north near the Redland, South Florida’s quirky mix of old homesteads and ornamental nurseries, have increased, suggesting the black and white spotted reptiles are on the move. Last year, they were also spotted for the first time near Florida Power & Light’s cooling canals at Turkey Point, where rare American crocodiles nest.
To biologists wearied by the decades-long effort to control the state’s invasive pests, it’s like a whack-a-mole victory, hamstrung by limited resources. So now they’re turning to another weapon: the public.
“Everybody in the Redland that reads this newspaper [needs] to look in their backyard and see if they see tegus because they’re emerging now,” said University of Florida biologist Frank Mazzotti. “If we can get everybody to report what they see, we can make up for lost ground very quickly.”
Tegus first appeared in the wild near a Homestead trailer park a decade ago, likely escapees from a breeder. And while they have been spotted all over the state — one was spotted behind a school in Nassau County in 2013 and nearly three dozen in a Panama City backyard after a breeder moved out — only two areas have established populations near Florida City and in Hillsborough County.
But because they still don’t fully understand their habits, scientists worry the hibernating lizards have the potential to spread beyond the state’s other monster invader, the Burmese python, which can only live in warmer temperatures.
This is by no means a closed system. Our concern is there’s a lot of great habitat.
UF Research Coordinator Jenny Ketterlin Eckles
“This is by no means a closed system,” said UF Research Coordinator Jenny Ketterlin Eckles. “Our concern is there’s a lot of great habitat.”
Intense trapping efforts didn’t begin until 2014, when UF, working with the state and Everglades National Park, focused on the population between the park and the canals, fearing the lizards could harm crocs and another endangered species, the Cape Sable seaside sparrow.
Their first year, UF biologists trapped 277. A year later, the number rose to 432. Last year, although the number of traps more than doubled, the UF team caught 446, a sign efforts were working.
The team also changed tactics. After figuring out how to catch smaller tegus in minnow traps usually used by researchers to catch small fish, they began focusing on hatchlings and yearlings in order to catch lizards before they begin reproducing. The team now monitors 150 traps tucked in pairs along canals and roads near a juvenile detention center.
“We did two things between 2015 and 2016,” Mazzotti said. “We simply put more traps out and we deliberately put traps out for hatchlings. And they worked.”
Because the traps must be checked daily when they’re baited, the effort can be labor intensive. On Tuesday, graduate student Sarah Cooke fought off spiders and mosquitoes, prodded a cottonmouth off the road and even bagged a 6-foot python during a morning check, unfazed by the sound of gunfire from a target range at the detention center filling the air.
In the last year, the team has also refined methods based on information supplied by eight radio-collared tegus that revealed where the lizards live and how they move.
“We know they like to stick to levees or berms, raised land,” said Brittany Mason, the telemetry coordinator. “And we noticed that where berms meet levees is a hot spot, so we’re putting drift fencing [foot-high sheets of aluminum flashing] to better trap them.”
They’re also learning the lizards really like to burrow. On Tuesday, Mason and graduate student Jenna Cole tracked a male tegu underground several feet from a canal bank, using a hand-held antenna and tracker.
While the lower trapping numbers are a good sign, some scientists worry something else might be influencing the results, like El Niño weather pattern that began in 2016 and continued until last year when a La Niña fueled heavy winds that has left the state bone dry this year.
“I’m not quite as optimistic,” said Tylan Dean, chief of biological resources at Everglades National Park, where tegus have been sighted but far less frequently. “It could indicate a reduction in the tegu population. But it could also be a result of some other factor, like the weather.”
Dean, who’s seen invasive pythons wipe out the population of small mammals across the park, also fears that if the tegus move into the Redland, where private land ownership and the mishmash of uses could complicate tracking and trapping, protecting park borders could become more difficult.
“To prevent them from getting into the park becomes a greater effort because we have to focus on more areas,” he said.
The state, which began catching the lizards in March and has so far caught 25, is also on track to trap more than last year in 50 traps set along Card Sound and Tallahassee Roads, said Florida Fish and Wildlife Conservation Commission biologist Sarah Funck, who heads the Nonnative Fish and Wildlife Program. But that increase could be attributed to putting out more traps.
“It is very difficult to determine which factor[s] is contributing to the change in numbers caught for us,” she said in an email.
What worries Mazzotti are the possible scenarios that could be behind the numbers popping up around the Redland: either lizards are spreading out but not setting up colonies, a good thing; isolated populations are popping up; or in the worst case scenario, interconnected breeding populations are forming, called meta populations.
Are they isolated or interconnected? That’s the question.
UF biologist Frank Mazzotti
“There’s certainly isolated individuals and hopefully they’re just dispersing,” he said. “But I don’t think so. Are they isolated or interconnected? That’s the question.”
So to help their cause, the team is taking a community policing approach by knocking on doors and handing out fliers describing tegus and listing contact information — 1-888-483-4681, www.IVEGOT1.org, and the IVE GOT 1 app — for reporting tegus. One researcher has been visiting nurseries and avocado groves, where biologists suspect — based on an outbreak of invasive Oustalet chameleons — tegus are using dirt mounded around newly planted trees to lay eggs, Ketterlin Eckles said.
But if this week is any indication, they’ve got a lot of work to do. As Cooke tried to coax a young tegu into a snake bag along Southwest 424th Street on Tuesday, a motorist slowed, spotted the egg used as bait and asked if she’d caught a bird. Cooke explained that it was a tegu.
“A what?” the woman asked.
“We trap them. They’re invasive,” Cooke replied.
The woman’s response? “What does invasive mean?”
Follow Jenny Staletovich on Twitter @jenstaletovich