These giant lizards have a reptile superpower that can help them thrive from Florida to North Carolina
Argentine black and white tegu lizards seem to break many reptile rules. They are smart enough to recognize individual humans. They are large, up to four feet long from nose to tail with intricate patterns. And they’re not entirely cold-blooded, a remarkable adaptation that intrigues biologists…and scares conservationists.
Native to South America, Argentine tegu populations are growing rapidly in Florida as descendants of escaped pet lizards gain a foothold in the wild. Conservationists worry that the tegu’s ability to regulate its body temperature, unique among reptiles, could help it survive and become established in North Carolina winters. The prospect is so worrisome that the state Wildlife Resources Commission banned sales and imports of Argentine tegu, effective Aug. 1, after only a handful of sightings statewide.
They are actually able to raise their temperature slightly above ambient conditions. This can give them a competitive edge to be able to invade further north than we originally intended.
Amy Yackel-Adams, research ecologist at the US Geological Survey
The first sign that these giant lizards can regulate their body temperature was discovered in 2016. Researchers from São Paulo State University noticed that tegus were sometimes considerably warmer than their surroundings.
Unlike other reptiles, which closely match the temperature of their environment, the tegus could stay warm for days in cool weather, perhaps thanks to an uncannily fast metabolism that sometimes resembled that of a mammal more than it did. that of a typical lizard. More recent research in the Everglades found that invasive tegus are almost always warmer than their surroundings year-round.
“They’re actually able to raise their temperature slightly above ambient conditions,” says Amy Yackel-Adams, a research ecologist at the US Geological Survey who helped study the Everglades. “It may give them a competitive advantage to be able to invade further north than we originally planned.”
In addition to fearing that they will establish themselves in North Carolina, tegus can sometimes survive in areas of the country that are considerably colder than they currently inhabit.
In a study of tegus’ ability to adapt to colder temperatures, researchers kept the lizards outdoors during the winter in Auburn, Alabama, more than a hundred miles north of Florida. Not all tegu survived, but those that did nearly doubled in weight at the end of a full year. The monthly low temperatures in Auburn are colder than in Wilmington throughout the year.
Their ability to withstand cold winters may be one of the reasons these lizards thrive in Florida, but it’s not the only one. Nor is it the only reason why they make environmentalists’ blood run cold.
Tegus are remarkably adaptable, which in Florida has made them both efficient and environmentally damaging. Tegus thrives in forests, plains, scrublands, wetlands, and even suburbs. “They’re incredible predators,” says Jeff Hall, a herpetologist at the North Carolina Wildlife Resources Commission.
“They eat just about anything they can put in their mouths.”
Tegus will after all go from fruit to snakes, turtles and baby raccoons. Of particular concern to conservationists, they also eat a lot of eggs, which can have a huge impact on native reptiles and ground-nesting birds.
Many reptile keepers are still unconvinced that tegus could ever establish themselves in North Carolina. Owner and President of Tegu temporary of the North Carolina Reptile Keepers Association, Adam Wulf describes the new restrictions on tegus as “extremely unnecessary”, saying the experience of tegu keepers shows they need temperatures much warmer than those that can be maintained in North Carolina.
“It’s been pretty firmly established that Argentine tegus do in fact need a very warm place to bask, and they need it quite regularly,” says Wulf. “Is it conceivable that one or two could spend the winter here or there? Maybe? But I would really doubt it because of our climate.
It’s hard to convince anyone of a problem before it starts, and in this case, state officials believe the tegus pose enough of a risk to impose a ban. So far, there has only been one recorded case of a tegu managing to survive a North Carolina winter – an unusual case of a tegu hiding in warm pipes under a nursery.
“But,” Hall asks, “how many cases like that does it take before you end up with an introduced population?” And once you have an introduced population, how difficult is it to eliminate that population? I do not know. I really don’t want to know.
Want to learn more about giant tegus and other species? CREEP is a podcast about creatures invading our space and changing the world around us, presented by WUNC and the North Carolina Museum of Natural Sciences. Listen and subscribe wherever you get your podcasts.