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Invasive tegu lizards from South America are currently established in four locations in Florida and negatively impact native, ground-nesting animals in the Greater Everglades Ecosystem. Two newly published research studies from the U.S. Geological Survey show that, depending on their size and body condition, tegu lizards could survive in cooler, northern climates.  

Tegus surviving in snow
Argentine black and white tegus can survive the winter under semi-natural conditions well beyond their current invasive range.

The Argentine black and white tegu is a large lizard from South America currently inhabiting the Florida counties of Charlotte, Hillsborough, Miami Dade and St. Lucie. Tegus are introduced to the U.S. through the pet trade and then likely released from captivity into the environment. 

"Several lines of evidence from recent USGS research studies published from 2018 to 2021 now provide clear indication for managers that the entire southeast portion of the United States is at risk of tegu establishment if lizard releases continue unabated," said Amy Yackel Adams, a USGS research ecologist. 

In the first study, published in Ecosphere, USGS researchers investigated how the invasive tegu lizards have adapted to hibernate in south Florida. They found that the lizards were able to keep their body temperatures high throughout hibernation despite the cooler environment. Researchers determined that changes in environmental temperatures and length of daylight generally caused the lizards to enter and exit hibernation, which averaged 138 days. Larger tegu lizards hibernated for longer periods of time while one tegu lizard did not hibernate at all, only the second time this behavior has been documented.  

For the second study, published in PLoS ONE, researchers captured tegus in southern Florida and translocated them to a site in Auburn, Alabama, where they were housed in semi-natural outdoor enclosures for one year. Despite the fact that this region receives snowfall, most tegu lizards were able to survive the winter, grew rapidly and hibernated for longer periods compared to resident Florida tegu lizards. One lizard remained underground for a period of 244 days, representing the longest documented period of dormancy for this species. These findings support previous USGS climate studies predicting the lizard’s survival across much of the southern U.S. 

Together, these studies demonstrate that tegu lizards can alter their hibernation behavior to match very different thermal environments, documenting the shortest and longest hibernation durations in this species.  

For more information about invasive species research in the Everglades, please visit the USGS Fort Collins Science Center website. Learn what to do if you see a tegu.

Invasive black and white tegu lizards (Salvator merianae).
A USGS biologist holds an invasive Argentine black and white tegu lizard that had been trapped by a USGS and National Park Service crew outside Everglades National Park.
Hourly tegu temperature during hibernation phases
This figure shows the median hourly temperatures for Argentine black and white tegu, hibernaculum and combined environmental data during days when animals were in pre-hibernation, hibernation, and post-hibernation, Greater Everglades ecosystem, Florida.