A Vermont study proves that a simple concrete tunnel can save thousands of frogs and salamanders each year—and help restore balance to fragile ecosystems.
Key Points at a Glance
- Wildlife underpasses reduced amphibian road mortality by over 80% in a 10+ year study.
- Over 5,000 frogs, toads, and salamanders were tracked, showing consistent use of tunnels.
- The project highlights the cost-effectiveness of small-scale conservation infrastructure.
- Local community engagement played a key role in driving the project and research success.
In the quiet Vermont town of Monkton, a revolution in conservation began not with technology—but with concrete and community. A newly published study led by the University of Vermont shows that wildlife underpasses—small concrete tunnels built beneath roads—can reduce amphibian roadkill by more than 80%.
The study, published in the Journal for Nature Conservation, tracked amphibian deaths over a 12-year period, making it the first long-term, peer-reviewed research of its kind in the northeastern U.S. It found that even modest underpass structures, designed specifically for small animals like frogs and salamanders, can offer massive ecological returns.
“It was surprising,” said lead author Matthew Marcelino. “I knew that underpasses would work, but I didn’t think they would be that effective.” When climbing species like spring peeper frogs were excluded, the mortality reduction jumped to 94%.
Before construction in 2015, the Monkton road was a deadly obstacle. Local residents documented over a thousand dead amphibians during just two rainy nights in spring 2006. Their concern led to action: a collaboration between the Monkton Conservation Commission, Vermont state agencies, UVM researchers, and conservation groups. The result? Two four-foot-wide concrete underpasses, complete with wing walls to guide the animals safely beneath the road.
The study team used a “before-after-control-impact” design to compare areas with and without underpasses. Between 2011 and 2022, they recorded over 5,200 amphibians—tracking twelve species including spotted salamanders and wood frogs. Mortality rates were consistently and dramatically lower in zones with tunnels. Even the buffer areas near the tunnels showed improved survival, suggesting that amphibians actively sought out the structures rather than being displaced.
Costing just over $340,000, the underpasses were a fraction of the price of large mammal crossings—which can soar into the millions. Yet they delivered ecosystem-scale benefits. Cameras installed by the Lewis Creek Association captured not only amphibians, but also bobcats, raccoons, bears, and birds using the structures. What began as a tool for frogs became a corridor for the entire forest.
Senior author and UVM professor Brittany Mosher emphasized the ecological timing of amphibian migrations. “It’s not just one species crossing—it’s many species, often all at once, moving from upland forests to breeding wetlands. Roads are often built right in their way.”
Because amphibians are slow and small, their chances of crossing safely without help are slim. But with underpasses, they gain a chance to complete their life cycles, maintain population health, and keep ecosystems thriving. “These are beautiful creatures,” Marcelino said. “So beautiful, so ancient.”
The study offers a clear message: conservation works when communities and science come together. What happened in Monkton could be a model for towns across the world facing biodiversity loss from habitat fragmentation.
“This study provides strong evidence that wildlife underpasses work,” Marcelino added. “We hope transportation departments everywhere take note.”
Source: University of Vermont
