Vermont’s Amphibian Underpass Cuts Wildlife Road Deaths by 80 Percent

A 12-year study shows Vermont’s amphibian underpass saved thousands of frogs, newts, and salamanders during spring migration seasons.

A small Vermont town discovered an innovative way to reduce amphibian road deaths by 80 percent after constructing an innovative amphibian underpass system beneath a busy road. This 12-year study offers hope for wildlife protection efforts nationwide, though, honestly, the solution isn’t flawless.

Monkton, nestled near Burlington, Vermont, witnessed a heartbreaking sight in spring 2006. Over two nights, more than 1,000 frogs, newts, and salamanders met their end on town roads. This tragic scene unfolded during the spring migration season, when these creatures move from forests to nearby ponds and streams to mate and lay eggs.

Every spring, this grim spectacle repeats across America’s roads. Adult amphibians migrate en masse from their wooded habitats to water sources for breeding. When a road intersects their path, the outcome is predictably deadly. I’ve seen many dead amphibians along the road, and it’s disheartening to say the least.

But the residents of Monkton refused to accept this as inevitable. Led by state wildlife biologist Steve Parren, a dedicated team of neighbours, state officials, university scientists, and environmental groups took decisive action. They constructed two concrete tunnels, each 1.5 meters wide, beneath the road, creating effective amphibian underpasses for migrating creatures.

The pivotal question remained: would these amphibian underpasses actually work? Here’s where Monkton’s approach stands out. Unlike many wildlife crossing projects, which lack rigorous before-and-after studies to measure effectiveness, Monkton’s effort was meticulously documented. For 12 years, volunteers and University of Vermont scientists braved rainy spring nights, meticulously surveying a 1.3-kilometre stretch of road. This extensive groundwork provided a solid baseline for comparison, with five years of data collected before the underpasses were operational.

The results surpassed expectations. In areas equipped with tunnels and concrete guide walls, amphibian deaths plummeted by 80 percent. For ground-dwelling species unable to climb trees or small concrete walls, the improvement was even more remarkable, with mortality rates plummeting by 94 percent. The design of the amphibian underpasses proved remarkably effective in safeguarding these vulnerable species.

“It was astonishing. I knew underpasses could help, but I didn’t anticipate such effectiveness,” remarked Matthew Marcelino, the University of Vermont ecologist leading the study. Published in the Journal for Nature Conservation, this research stands as one of the most comprehensive evaluations of amphibian underpass efficacy ever conducted.

Unexpectedly, the tunnels attracted a variety of users. Wildlife cameras captured black bears, bobcats, and porcupines making their way beneath the road. These larger animals benefit from safe passage just as much as the tiny amphibians the underpasses were initially designed to protect, underscoring the broader ecological value of this infrastructure.

Yet, the solution isn’t flawless. While death rates among spring peepers, small frogs capable of climbing, dropped by 74 percent, the improvement wasn’t statistically significant. More concerning, there was no improvement in amphibian death counts in buffer zones adjacent to the tunnels or road sections farther from these crossings.

To enhance underpass performance, the research team suggests several improvements. Adjusting the angle of concrete guide walls away from the road could better direct animals toward tunnel entrances. Installing overhangs atop these walls might prevent tree-climbing species from scaling barriers and entering traffic lanes.

For many, this may seem a niche issue impacting only rural Vermont towns. Yet, amphibian road deaths occur wherever suburban and rural roads intersect natural habitats. During spring migration, countless roads become amphibian graveyards as these creatures follow ancient routes now bisected by busy streets.

Timing exacerbates the issue. Amphibians migrate on warm, rainy spring nights when visibility is poor and roads are slick. I’ve driven on such nights—you can barely see what’s right in front of you, let alone tiny creatures crossing the road. This is precisely when an amphibian underpass proves invaluable.

Beyond immediate animal welfare, amphibian deaths impact ecosystem health. These creatures regulate insect populations, serve as vital food sources for other wildlife, and signal the health of wetland ecosystems, which provide flood control and water filtration. Protecting them through infrastructure like amphibian underpasses benefits entire ecological systems.

See also: Hedgehog Highways Offer Hope for Species Recovery

The success in Monkton could inspire similar projects elsewhere, though funding remains a hurdle. State transportation departments typically prioritize human safety and traffic flow over wildlife protection in budget decisions. However, the proven effectiveness of Monkton’s underpass model may justify future investments.

This study also raises broader questions about transportation choices. While tunnels represent engineering triumphs, they address symptoms rather than root causes. Researchers hint at a simpler solution that requires no construction: reducing vehicle usage.

For now, Monkton’s amphibian underpass serves as a beacon for communities confronting similar wildlife crossing challenges. The project showcases what is possible when communities, scientists, and government agencies come together in wildlife protection efforts.

As each spring approaches, those tunnels beneath Vermont’s roads continue their quiet work. Salamanders, frogs, and newts embark on their ancient journey to breeding grounds, now with a significantly higher chance of survival thanks to their dedicated amphibian underpass.