Anyone who has spent much time in southern Florida knows it is hard to take more than a few steps without seeing a lizard. While this may be a slight exaggeration, lizards are very abundant in urban and rural landscapes alike. The amazing array of lizard life in this state is not just a function of having a climate suitable for cold-blooded (a.k.a. ectothermic) animals. As a big importation hub for all kinds of goods, including exotic animals sold as pets, Florida essentially puts out a welcome mat for reptiles arriving here from distant continents.

“Astonishingly, there are more non-native reptiles and amphibians established in Florida than anywhere else in the world,” explains Dr. Betsie Rothermel, Archbold’s Herpetology Program Director. “If you conduct a lizard survey in extreme South Florida - which quite a few herpetologists have! – you are now more likely to encounter non-native lizards than native ones.”

Some introduced lizards find Florida wetlands, forests, and other wild spaces to be just as hospitable as their home turf. Once they are free of the predators and competitors that kept them in check in their native territory, they can often reproduce and expand rapidly. However, the outcomes of each new reptile introduction are somewhat unpredictable. Given the pace of introductions, biologists and agencies are scrambling to sort out which species are likely to gain a foothold in the wild. This challenge has spurred an entire branch of ecological science devoted to “invasion biology” that investigates introduction pathways, ecological and economic impacts, and control methods.

Several invasive lizard species that are now roaming the wilds of Florida are much larger than any of our native species. Take, for example, the Argentine Black and White Tegu, which is native to South America and became a popular pet species. Adults of this species can weigh up to 11 pounds and reach 51 inches from nose to tip of tail, much larger than any lizards native to Florida.

Argentine Black and White Tegus have a very diverse diet. According to Aaron Chimelis, a wildlife biologist at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) for the UF Croc Docs lab, “Tegus are omnivores, consuming both plants and animals, including alligator eggs, tortoise hatchlings, invertebrates, fruits and seeds. This flexible, broad diet makes them a grave threat to Florida’s native ecosystems.”

In addition, biologists have recently found tegus infected with an invasive lung parasite (pentastome) carried by Burmese Pythons. According to former Archbold intern Madison Harman, now a Lab Manager for the Florida Invasion Ecology Lab at the University of Florida, “These invasive pentastomes spread from pythons to native snake species, as well as tegus, which are likely dispersing pentastome eggs to new locations. We have found dozens of invasive pentastomes filling the lungs of native snakes. Tegus and other invasive species are a major source of new parasite introductions, which can be really harmful when they infect our native wildlife.”

Tegus are not yet established in Highlands County, but there are breeding populations in nearby counties and the public is urged to report any sightings immediately to FWC’s Invasive Species Hotline (1-888-Ive-Got1). Rothermel explains, “As a large, novel predator, Argentine Black and White Tegus are likely to have more negative impacts than other already-established invasives like Curly-tailed Lizards and Peter's Rock Agamas.” Tegus thrive in open, scrub-like habitat, which brings them into overlap with Gopher Tortoises, Florida Scrub-Jays, and other imperiled native species. As Rothermel puts it, “Imagine you are one of our ground-nesting reptiles or birds that evolved here in the Florida scrub. The only lizards you have ever encountered were small and harmless to you and your young. A tegu showing up in your neighborhood may as well be Godzilla.”

Photo courtesy of University of Florida Croc Docs Lab.

These concerns about Argentine Black and White Tegus prompted the state wildlife agency to declare them a Prohibited Species in 2021, which means they cannot be kept as pets or for commercial sale (with very limited exceptions). There is also a big push to evaluate the effectiveness of different control methods. For example, the UF Croc Docs are “conducting systematic removals of tegus in key areas of Florida while also testing out different ways of trapping tegus such as utilizing AI, which has shown promising results” according to Chimelis “with winter coming soon, tegu activity is decreasing as the lizards begin to brumate for a few months, giving us some more time to prepare for the next trapping season which begins early February when the animals begin to emerge once again.”

Early detection of invasive lizards is vital to control efforts and is something YOU can help with. Please report sightings of invasive lizards, especially large species like tegus. Submit information via the “IveGot1” app (which can be downloaded from your app store) or by calling 1-888-Ive-Got1. If possible, take good photographs of the animal to include with your report. The more details you can provide on where you saw the animal, the better.

Finally, NEVER release an unwanted pet reptile into the wild. If your pet cannot be responsibly rehomed, please contact FWC’s Pet Amnesty program at 1-888-486-4683 or PetAmnesty@MyFWC.com.