Tunnel crossings eyed as a fix for deadly reptile, amphibian roadkill hotspots

Munching on mosquito larvae, recycling nutrients, or helping lock away carbon: Tucked away in New Hampshire’s forests, waterways, and vernal pools, reptiles and amphibians are doing it all. But throughout the state, these animals also face a fast-moving and rising threat to their continued existence: traffic.

Roadkill is one of the biggest threats that reptile and amphibian populations face in the Northeast, scientists say. With traffic and development increasing in the region, the danger to wildlife is mounting. But there are infrastructure improvements that can reduce that risk, and some of them are now in the works in New Hampshire for the first time.

A grant awarded to the New Hampshire Department of Fish and Game will fund the state’s first set of wildlife underpasses at several high-hit sites in the state, the department announced March 19. Conservationists hope it will touch off a cascade of similar projects to help address the broad-reaching impacts of roads and traffic.

“We can’t carry every frog across every road, so we’re really excited about projects like this,” said Brett Amy Thelen, science director at the Hancock conservation nonprofit The Harris Center. “…For each animal, you know, [a crossing] really makes a difference.”

A major danger and an ‘invisible problem’

“They’re, like, six to eight inches long. They’re as thick around as your thumb. They have bright yellow polka dots. They’re stunning, and they live around us all the time, but we almost never get to see them, because they’re mostly underground,” Thelen said Mar. 23, animatedly describing one of New Hampshire’s native amphibians: the spotted salamander.

Most of the time, the species spends its days hidden under leaf litter in the forest. It’s when these animals emerge to migrate to vernal pools, as they do in droves every spring, that they are most likely to cross paths with humans and cars.

Spotted salamanders’ vulnerability to roadkill is not unique. Roads are lethal for many wild species. But amphibians and reptiles, a category collectively referred to as “herps,” are particularly vulnerable, said Sandra Houghton, wildlife diversity biologist with the New Hampshire Fish and Game Department.

One reason for this is their small size and slow movement. Another is that for certain long-lived animals, like turtles, the death of just one individual makes a significant dent in their local population.

The life patterns of these species often make them more likely to encounter cars, too. Many follow seasonal migration patterns that require them to cross from one habitat to another every year. And in New Hampshire, that journey often involves crossing a road.

Yet when most people think of roadkill, they associate the phenomenon with mammals, Thelen said.

“It’s, for many people, an invisible problem, because it’s happening after dark on rainy nights and by morning many of the … amphibians that have been killed have been scavenged or kind of crushed beyond recognition,” she said.

Though public awareness of the phenomenon might be limited, its impact is not. Research suggests that roadkill alone could be enough to eliminate local populations of amphibians from a given habitat within a matter of decades, Thelen said. 

Meanwhile, turtle deaths at road crossings can have similar effects on their populations, according to a 2023 state report on the status of the endangered Blanding’s Turtle. Roads also pollute adjacent areas with road salt, emissions, and noise, according to the New Hampshire 2025 State Wildlife Action Plan, while other pressures like climate change, habitat loss, and disease add to the burden on wild species.

As New Hampshire becomes more developed, the state’s network of roads, the volume of traffic on them, and their impact on wildlife is also growing, according to the action plan.

This is, in part, because roads generally aren’t designed with wildlife in mind, conservationists said. In all of New Hampshire, for example, there are an estimated 26,000 places where aquatic habitat is bisected by a road, according to the Blanding’s turtle report. Many of those crossings weren’t designed with wildlife-friendly infrastructure, the report found.

The projects planned for the grant dollars, said Houghton, are intended to help address that at a handful of sites.

A solution in sight

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The grant, from the National Fish and Wildlife Foundation, will allow the Department of Fish and Game to work with three municipalities — Keene, Newmarket, and Nottingham — to improve an existing road by installing a wildlife-friendly underpass.

The projects will consist of culverts and tunnels designed for amphibians to pass through, coupled with barriers to help usher creatures toward the passageway, according to a press release from the department.

Similar projects in neighboring states have shown positive results. One study at a wildlife underpass in Monkton, Vermont, found that the passageway reduced amphibian mortality by about 80%.

The solution isn’t perfect: Passageways are expensive to implement, and not all amphibians find their way to them. Some manage to get over the barriers and onto roads — particularly species like spring peepers, which are natural climbers. But Houghton said the method was promising nonetheless, and an important next step to make roads safer for amphibians.

“It’s one of those opportunities where there is a solution that has been shown to work, which we don’t always have. So that’s one of the really exciting pieces,” she said.

She also anticipates that the changes will improve the flow of water under roadways in a way that makes the roads themselves more resilient to flooding.

Volunteers keep tabs on herps

The locations were chosen with help from monitoring data, proving that the sites are home to species of “grave conservation need” as listed in the State Wildlife Action Plan, Houghton said.

That data came from an array of sources, including the volunteers marshalled every spring by the Harris Center’s “salamander crossing brigades,” which Thelen helps lead.

“Brigade” volunteers focus their efforts on a series of major amphibian migrations that occur every spring, coinciding with the first warm rains after the ground has begun to thaw. It is on these days — called “big nights” — that amphibians come out in droves, migrating to the seasonal pools where they were born to start the cycle anew. At road crossing hotspots across the state, volunteers emerge, too, to help shepherd the creatures across.

The main goal of the program is to reduce roadkill, Thelen said. But volunteers also mark down data about the different species they see and total numbers of observed crossings. Twenty years of that data helped inform the plans for two underpasses in Keene that will be funded with the grant, Houghton said.

On March 16, the first southern New Hampshire “big night” of 2026, what the volunteer network observed in Keene underscored the importance of the planned projects, Thelen said. On one stretch of road between a forest and vernal pool, volunteers recorded more than 1,000 frogs in about three hours. Other amphibians were spotted, too, including the endangered Jefferson salamander.

The Harris Center works with the town of Keene to limit traffic on two hotspot roads. But even with that measure and a network of volunteers, they still documented three Jefferson salamander roadkill deaths on the 16th, Thelen said.

“It doesn’t take a lot of cars to do a lot of damage on a night like that,” she said.

Jordan Road, where those deaths were recorded, is the site of the planned crossings in Keene, according to Thelen. 

Herps contribute to the ecosystems they reside in in myriad ways, from keeping insect populations in control to serving, themselves, as an important food source for a number of animals higher on the food chain. But in addition to all that, it’s the joy that salamanders and amphibians bring to volunteers every Big Night that keeps Thelen motivated, she said. 

“If you’re someone who cares about wildlife, hearing every day about how humans are causing harm to wildlife, it’s just really hard. So the crossing brigade nights are kind of an antidote to that,” she said. 

For her and for Houghton, the planned passageways are another spot of hope.

“This is the first project of its kind in New Hampshire, but it’s my sincere hope that it won’t be the last,” Thelen said.