Urban Lizards Full of Lead, but Not Dead
Featured Image caption: Urban Lizard (Podacris muralis) by Gzen92 CC by SA 4.0 via Wikimedia Commons
Primary Source Article: Moore, M. M., Foster, E. G., Amer, A., Fraire, L., Head, A., Blanchette, A., Hankison, S. J., Gunderson, A. R., & Gangloff, E. J. (2025). Urban wall lizards are resilient to high levels of blood lead. Environmental Research, 264(Pt 1), 120248-. https://doi.org/10.1016/j.envres.2024.120248
When you drink a glass of water, take a breath of air, or go out to play, metal contamination is not something you think of. However, heavy metal contamination is a problem in the United States. For residents in Cincinnati, Ohio, concerns about lead poisoning are real. Living in urban environments is challenging not just to people, but wildlife as well. According to Moore and colleagues, little is known about the effects of lead on reptiles, but studying lead toxicity in these creatures, specifically urban lizards, can provide clues on how to improve health outcomes of lead poisoning in people. Urban wall lizards from Cincinnati, Ohio were studied for lead poisoning and exercise performance to determine the effects of lead poisoning on wildlife.
What is a Wall Lizard?
A Wall lizard (Podacris muralis) is a European species of reptile that arrived in Cincinnati after they were released in the early 1950s. They are about 5-8 inches (about 13-20 cm) in length with a brown or gray back and spots on the sides These lizards now reside in the Cincinnati area, northern Kentucky, and have expanded into southwest Ohio and southeast Indiana. These critters like to reside on rocky areas near river banks and urban or suburban areas. They are at home in hubble heaps, loose stone, and degraded buildings. They aren’t picky eaters and have a diet of insects such as crickets, grasshoppers, spiders, invertebrates, and plant materials. As their name implies, they can run quickly, climb well, and jump.
Understanding the Cincinnati Urban Landscape
Cincinnati has a diverse urban landscape. It is made up of industrial sites, parks, and residential areas. Lead contamination comes from different sources and concentrations, which includes vehicle exhaust particles, weathered street surface particles, industrial emission, lead pipes, and domestic emissions from buildings built before the mid 90s with leaded paint. Over time, this accumulates in the soil and is then transferred to lizards directly or through their food source.
Scientists in this study wanted to study whether the average amount of lead in the blood would differ in locations close to roads versus park regions. If this were the case, how would different lead concentrations of the blood affect the exercise performance?
Wall Lizards Work out for Science
How do you get wall lizards to exercise in a way that is measurable for performance? When Moore and colleagues were designing the experiment, performance measures were tested based on exercise that they would normally do in their habitat and would also potentially be affected by the toxin in question. These scientists opted to study balance since lizards are climbing specialists and it is known that lead has neurotoxic effects that affect balance and coordination. In addition, they chose an endurance test since lead affects red blood cell production and the ability for the body to carry oxygen. They also collected blood samples from lizards and measured their lead concentrations.
To test for balance, each lizard was placed on wooden dowels and tapped on the hindlegs with a paint brush to begin the trial. For each trial, they looked at the total number of slips and total distance traveled. If a lizard’s hind feet lost traction or if they clung to the balance beam to stop from falling off, this was considered a slip.
When it was time to test for endurance, lizards were placed on treadmills. That’s right, treadmills! There are treadmills specifically designed for tiny critters.
Relationship of Lead on Performance
Some of the results of the experiment may surprise you. Lizards that were collected on the roadside compared to park locations had 28% higher concentrations of lead in their blood. Yet, blood cell count was unaffected by lead concentration. However, when comparing exercise performance, lizards with higher lead concentrations performed better in the balance tests, and showed no difference in endurance tests.
Moore and colleagues had difficulty narrowing down a reason behind why balance performance was better. Could it be that these lizards have a mechanism to avoid the negative effects of lead? Is it possible that lead still has an effect on these lizards in more subtle ways? In terms of the effect of lead concentration of the sexes, females in the study had significantly higher levels of lead than males. Transfer of lead to offspring have been observed in other species, but this was mainly observed in bird species. According to the article, lizards have the ability to regenerate brain cells which may have enabled these results.
Why Care About Lizard Health?
Overall, this research adds to the broad discussion that health does not happen in isolation. The health of people, animals, and the environment are intertwined. Fighting health issues involves looking at all of these things holistically to inform public health and policy practices. Rightfully so, Moore and colleagues highlight how this research adds to the “One Health approach” for improving health outcomes. It’s important to understand that if lizards are dealing with metal contamination, chances are so are we. Looking at reptiles can be a quick approach for determining whether environmental policies are having an impact. Perhaps studying reptiles can also help us better understand coping mechanisms for lead poisoning, and could allow us to develop better treatments in the future.
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