10 lizards were smuggled into Cincinnati in a sock. Now there are tens of thousands.

National Geographic

05-03-2025

Native to Europe, common wall lizards are growing bigger, faster, and more resilient in Ohio. Scientists say the city itself may be driving their evolution.
A Lazarus lizard suns itself on a warm rock in Burnet Woods, one of many European transplants that have taken over Cincinnati, Ohio. Scientists say the city's hills, aging infrastructure, and even its climate have helped them thrive.
A Lazarus lizard suns itself on a warm rock in Burnet Woods, one of many European transplants that have taken over Cincinnati, Ohio. Scientists say the city's hills, aging infrastructure, and even its climate have helped them thrive.
A Lazarus lizard suns itself on a warm rock in Burnet Woods, one of many European transplants that have taken over Cincinnati, Ohio. Scientists say the city's hills, aging infrastructure, and even its climate have helped them thrive.
A Lazarus lizard suns itself on a warm rock in Burnet Woods, one of many European transplants that have taken over Cincinnati, Ohio. Scientists say the city's hills, aging infrastructure, and even its climate have helped them thrive.
For more than 70 years, thousands of common wall lizards, known as Lazarus lizards, from Europe have made Cincinnati their home. Even through record-low temperatures and snowfall, they've managed to survive—and multiply. But how did these Mediterranean reptiles gain such a foothold in a Midwestern city? It all started with a 10-year-old boy and a sock full of lizards.
In 1951, George Rau Jr., whose stepfather, Fred Lazarus Jr., founded the retail chain that would later become Macy's, smuggled 10 Italian lizards home from a family trip in Lake Garda and set them loose in his backyard. He had no idea he was unleashing an ecological experiment spanning decades.
Today, their descendants number in tens of thousands—if not hundreds—of thousands. Declared 'permanent residents' by the Ohio Division of Wildlife, they scurry across sidewalks, cling to brick walls, and flourish in an environment that seems much different than where they're from. How did Cincinnati become their perfect home?
Why Cincinnati is the perfect lizard habitat
Although Cincinnati is not 'traditionally thought of as lizardy,' it has proven to be a haven for the introduced lizards, says Eric Gangloff, a biology professor at Ohio Wesleyan University. He has spent five years studying the lizards in Cincinnati, and before that, he researched them in their native European range.
In the 1980s, researcher S.E. Hedeen discovered that Cincinnati's climate is remarkably similar to that of Milan, just 70 miles west of Lake Garda, where the lizards originated. Their year-round temperatures vary by only a few degrees Celsius, and precipitation levels stay within the same 10-centimeter range each month.
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But climate isn't the only reason these reptiles have flourished. Cincinnati's landscape has turned out to be an ideal substitute for their native habitat as well.
'Cincinnati is extremely hilly, and a lot of the old neighborhoods have stacked-rock retaining walls,' says Jeffrey Davis, a herpetologist who has been monitoring them since the early 2000s. Many of those walls have no mortar or cement between the rocks, which 'makes a zillion little nooks and crannies and crevices that the lizards can dart into, and it also gives them access to the underground,' where they go in winter, he adds.
'It probably isn't terribly surprising to [biologists] that they survived, because they were pre-adapted,' says Davis. 'The thing to me that is so surprising is the density of the populations.' This species, Podarcis muralis, has also been found in other areas of Ohio and on Vancouver Island, Canada, but no other population is believed to be as prolific.
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In some neighborhoods, as many as 1,500 lizards pack into a single acre, far more than their typical density in Europe, partially due to the reduced threat of predators and parasites. Even the Torrence Court neighborhood, where Rau Jr. first released them, remains a lizard hotspot.
Evolving lizards
After decades in Cincinnati, the lizards may be evolving to better navigate their urban world.
Gangloff oversees a team of student researchers—dubbed the 'Lizard League'—who study the reptiles in a lab, testing how they respond to different environmental conditions. So far, they've found that the animals are getting larger and developing longer limbs, possibly to help them run from house cats, their primary urban predators.
After subjecting the lizards to various temperatures and wind speeds, hypothesizing that they would select cooler temperatures in higher winds to conserve hydration, the lizards did the opposite. And despite prolonged exposure to heavy metals in the city, the lizards seem unaffected.
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'One of our experiments involved running lizards on treadmills to test their endurance and see if the levels of lead in their blood had any effect on this, because we expected that there would be some kind of association there,' says Emma Foster, a neuroscience junior at Ohio Wesleyan. 'And we found that the lizards didn't seem impacted by the lead toxicity at all.'
Since 2022, this research has been funded by a four-year grant from the U.S. National Science Foundation, which 'seeks to identify the reasons that this species has flourished in novel urban environments on a new continent after an introduction of so few animals.' The entire population in Ohio is believed to have spawned from just three individuals of the original 10.
Beyond solving the mystery of Cincinnati's lizard boom, this research could have broader implications—including for human health. While mice are the widely preferred model organisms for biomedical research, Foster says, 'there is also value in studying unique features of animal brains that are less similar to the human brain.' If the lizards are more resilient to heavy metal exposure, then how could that translate into a drug for humans?
'That's very far in the future,' she says, 'but thinking broadly, that is where this kind of research could go.'