All Online Exclusives

Nighttime Teamwork Improves Odds for Amphibians

Brett Amy Thelen ’99 and New Hampshire volunteers assist amphibians on their dangerous seasonal journey

March 16, 2023
By Laura Grove ’22

SAVING SALAMANDERS: Brett Amy Thelen ’99 poses with a spotted salamander in Keene, New Hampshire. Thelen’s passion for community science as a way to connect environmental education with conservation research shines through in the popularity and success of the Salamander Crossing Brigades. Photo by Anna Miller.

A woman stoops over a cold, wet road in a reflector vest just after 10 p.m. as steady rain patters the pavement. She gingerly scoops up an orange-brown frog the size of the tip of her thumb. She takes note of its tiny suction cup toes, dark banded legs and the X-shaped pattern on its back before delicately depositing it on the other side of the road. Volunteering alone tonight due to an unexpected change in the weather, she has tallied more dead amphibians than live ones.

Brett Amy Thelen ’99 is the science director at the Harris Center for Conservation Education in Hancock, New Hampshire. Her passion for community science, love of the outdoors and patient, practical demeanor make her the perfect fit for her position. Among other things, she supervises the Salamander Crossing Brigades, groups of local volunteers who don warm clothes and reflective vests on specific nights when multitudes of amphibians migrate. On these “Big Nights,” hundreds of volunteers travel to sites in southwest New Hampshire where amphibians cross roads in large numbers. They then ferry our fun-size friends across by hand.

Amphibians are critical to forest and wetland ecosystems, but their populations are dwindling rapidly. One of the culprits in their decline is road mortality, which is particularly problematic on rainy spring nights. Everyday people are passionately working to remedy this situation, however, and they’re having the time of their lives doing it.

In woodland and wetland ecosystems, amphibians such as frogs, toads, newts and salamanders are indispensable members of the food web. They voraciously chow down on insects and worms. Toads, for example, can eat approximately one to three times their body weight in insects each night. In turn, amphibians are devoured by numerous other species. Without the crucial sustenance that amphibians provide, countless birds, reptiles, fish and mammals would struggle to survive, particularly in the early spring when winter food sources are limited.

Additionally, a diversity of plants, animals and microorganisms is necessary to effectively maintain natural cycles that provide food, clean water and breathable air. By contributing nourishment to such a wide variety of species, amphibians play a crucial role in maintaining the biodiversity necessary to propel these vital life-sustaining processes.

A frog camouflages onto a road
ROAD CAMO: A gray tree frog blends in with the pavement at a crossing site in Keene, New Hampshire. Note the sizeable toepads, which this species uses for climbing trees. When not migrating, gray tree frogs live on bark, look like bark, and eat insects that live in bark. Photo: Brett Amy Thelen

In many temperate areas of the world such as North America and Europe, the forest floor awakens on early spring nights when the weather is just right. Armies of amphibians travel, as they have for millions of years, from upland forests to vernal pools and other wetlands to breed and lay eggs. Human development has thrown new perils into their path, and roads are one of the most deadly. A 1991 study found that cars crush an estimated 50% to 100% of salamanders attempting to cross rural roads in New York state, according to “Global Climate Change and Life on Earth by Richard L. Wyman. A 2005 study by researchers from the College of Environmental Science and Forestry in New York estimates that road mortality could cause the extinction of local populations of amphibians at their Massachusetts study sites in as few as 25 years.

Since 2007, approximately 1,800 Salamander Crossing Brigade volunteers have shuttled more than 70,000 amphibians to safety in southwest New Hampshire. Members also carefully record the number of each species that they encounter. Thelen, who has worked on many community science projects, finds that this one particularly appeals to volunteers. “In addition to collecting information, we’re saving the lives of individual animals, which is a really powerful experience for people,” Thelen explains.

There are three conditions that Thelen evaluates when predicting when Big Nights will occur: thawed ground, nighttime temperatures and wet weather. Spring-migrating amphibians spend the winter below ground. Wood frogs, who survive the winter by freezing solid, nestle into the ground 2 to 4 inches below the surface, counting on a natural form of antifreeze in their systems to protect their internal organs from damage while they’re frozen. Most other amphibians snooze below the freeze line, which is the maximum depth to which the ground water within soil freezes. In New Hampshire, that can be as deep as 60 inches below the surface. The ground must be thawed for amphibians to clamber their way back to the forest floor to migrate. Additionally, amphibians are ectotherms, meaning that their body temperature is regulated by their environment. Therefore, air temperatures must be at least 40 degrees Fahrenheit for them to be active enough to travel. Lastly, amphibians breathe through their lungs and their skin. In order to absorb oxygen through their skin, they must stay moist. Thus, they travel in wet weather. Thelen keeps a close eye on the weather and provides a five-day salamander forecast during migration season. Volunteers can easily check the website to see if they should remain on-call.

What is it like volunteering in a Salamander Crossing Brigade on a Big Night? Safety comes first, Thelen explains. A reflective vest is mandatory. It’s dark, rainy and sometimes foggy, and drivers cannot see you without one. A bright flashlight or headlamp is also necessary for spotting amphibians on the pavement. Many Brigade members, including Thelen, use both. Layers of warm clothing and rain gear are also important. For recording data, volunteers gather a clipboard, pencil and forms on special paper that can be used in rainy weather. Some members bring a clean bucket to particularly busy sites so that they can transport multiple amphibians at once. Cameras and phones are popular items, too, as pictures allow volunteers to share their experience with friends and family.

A salamander rests on a volunteer's hand, above a data sheet.
THE VERY BEST KIND OF DATA: A Salamander Crossing Brigade volunteer collects data at a crossing site in Keene, New Hampshire, on a Big Night in April 2018. Photo: Brett Amy Thelen

Brigade members range from parentally supervised 6-year-olds to senior citizens. Volunteers come from all walks of life, including nurses, restaurant workers, lawyers and landscapers. Some are experiencing their first season, and others have been at it for more than 15 years. Many work in pairs. One person transports and identifies the amphibians and the other records the data. The adventure begins at sundown and lasts as long as volunteers choose to stay. Many leave by midnight, when traffic has mostly petered out, but some stay until 2 or 3 a.m. Thelen stresses that having fun is important. “If you’re not smiling anymore because you’re cold, wet and tired,” she instructs her trainees, “it’s time to go home.”

Since 2014, volunteers at five selected sites in Keene, Swanzey and Nelson, New Hampshire, have had a special mission: photographing individual spotted salamanders. Each brightly colored salamander showcases a unique pattern of dazzling yellow spots on the back of its blue-black body, much like human fingerprints. Members of this mostly subterranean species can survive more than 20 years. By comparing photos to those from previous years, researchers at the Harris Center have been able to determine that several of the same salamanders cross at the same site year after year. Thelen explains that volunteers are excited about the implications. “It’s not just a generic salamander. It’s this salamander who I have carried across the road for the last five years in a row. This individual.”

A salamander is held in a volunteer's hand
MR. ADORABLE: This wee spotted salamander was helped across a road in Peterborough, New Hampshire, by dedicated Salamander Crossing Brigade volunteers on a late-season migration night in May 2019. Photo: Sarah Thomas

Most of the spotted salamander data has yet to be analyzed as there simply isn’t enough time, but Thelen believes that it is a veritable treasure trove for just the right graduate student. The data has the potential to provide valuable insight into the year-to-year survival and migration patterns of individuals within the species.

The other data that Brigadiers collect comes in handy for local decision making. However, Thelen is quick to point out that their data isn’t necessarily suitable for peer-reviewed studies. This is largely due to variable effort. For example, one site may have 25 volunteers collecting information, and another may only have two. Thus, data at the second site is likely to be less complete than data from the first site. Additionally, most volunteers go home by midnight, but the migration continues until dawn. Amphibians that cross in the absence of volunteers are not counted. Some volunteers also prefer not to count dead amphibians, so those numbers are often underreported. However, the data collected can still be put to good use.

Take the case of a property in Keene, New Hampshire, that was slated for residential development. Situated adjacent to a wetland and across a road from a wooded hillside, this land is heavily used by amphibians traveling between their year-round habitat and spring breeding grounds. When called upon by the local Conservation Commission for information about this site, Thelen shared Brigade data from a few nights before. Approximately 25 volunteers had moved 838 frogs across the road to that property within four hours. The Brigade data was a significant factor in the decision to deny the development proposal, and the land is now preserved as a valuable amphibian breeding habitat. “I really believe that if we didn’t have the data, those numbers, both of amphibians and people who care about amphibians, it wouldn’t have been as compelling an argument,” Thelen explains.

A salamander has its photo taken in a lightbox.
SALAMANDER PAPARAZZI: The spots on adult spotted salamanders are like fingerprints on humans: each salamander has its own unique pattern, which can be used to tell that individual apart from all others. Thus far, nearly 50 different individual salamanders have been recorded on more than one occasion by Harris Center volunteers. Modified coolers known as “lightboxes” (seen here) allow for hands-free photos for the Harris Center's spot pattern database. Photo: Brett Amy Thelen

Conservationists employ several strategies to combat amphibian road mortality. Amphibian tunnels installed under roads at crossing sites are one of the most effective. These structures are approximately 2 feet wide, 2 feet deep and topped with an open grating to allow sufficient rain penetration and air circulation. Fencing positioned along the road guides creatures to the tunnel. Researchers from the University of Cambridge determined that these structures are an effective way for amphibians to dodge dangerous roads. The problem is that tunnels are expensive. For example, two tunnels recently installed in Monkton, Vermont, cost approximately $400,000. Although amphibian deaths are now negligible at that site, the price tag is still a big hurdle for decision-makers in other communities. Thus, they often search out other strategies.

Currently, the next best solution is temporarily closing specific roads on Big Nights. In Keene, New Hampshire, that would mean closing roads four to six nights each spring to allow amphibians to safely cross throughout the entire night. In 2008, Thelen made her case for closing one particular road, North Lincoln Street, on Big Nights. The Salamander Crossing Brigades were fairly new, but Thelen had two years of data showing that amphibians cross this road in extremely high numbers. She stood alone before the Keene City Council and presented her case.

They politely turned her down.

Although disappointed with the decision, Thelen continued with her work. News of the Salamander CrossingBrigades spread, and more members of the community signed up each season. Friends, family and coworkers of volunteers attended training sessions and patrolled the roads at night, delighting in amphibian encounters.

Ten years passed before Thelen again stood in front of the city council, requesting that they close North Lincoln Street on Big Nights. But this time, things were different.

People of all ages and backgrounds squeezed into the room. All wore reflective vests, the uniform of the Salamander Crossing Brigade. Not only did Brigadiers fill every chair, they also lined the walls, vests reflecting the fluorescent light. Thelen presented 12 years of data, and this time, the motion passed.

Asked about the public’s reaction to the road closure, Thelen explained, “At first there was a lot of worry that people would be irritated by the inconvenience or think it was stupid or silly, but it’s become an incredible source of pride for that town.” Since then, council members have approved closing another stretch of road on Big Nights. Public awareness and the ranks of the Brigade continue to swell, giving New Hampshire amphibians a fighting chance.

So, what you can do to help local amphibians? If volunteering on Big Nights sounds like your kind of thing,nine states in the eastern U.S. now have amphibian crossing programs. Check to see if there is one near you. Starting your own group is another option and finding potential crossing sites isn’t difficult. A 2009 study found that these sites are almost always within 100 meters of a wetland. Thelen suggests looking for any stretch of road with a forested hillside on one side and some kind of wetland on the other. Try not to drive too far, though, as you may end up crushing some amphibians on your way to help others. “Throw on a reflective vest, get a flashlight, and go out for a walk and see the world, because it’s amazing on these nights,” Thelen advises. “But do it on foot, if you can.”

If you’d prefer not to spend hours outside in cold rain, you can still save amphibian lives by trying to avoid driving on rainy spring nights. When possible, put that errand off until tomorrow, cozy up with a good book and rest comfortably, knowing that even one less car on the road makes traveling safer for our amphibian friends.

A few nights later on that cold, wet road, the rain lets up a little as the woman gently grasps a sleek spotted salamander that wears the oft-observed friendly smile for which its kind are famous. A dozen other steadfast amphibian enthusiasts work alongside her tonight, so live amphibians are far more numerous than dead ones. Each precious individual that they save can complete its journey to ensure future generations of its species. She smiles as she imagines future generations of her own species enjoying the wonders and benefits that these creatures provide.

Learn more about Thelen's work in this podcast, "Toadside Assistance," by Laura Grove ’22, Tara Malloy ’22 and Erin Ramsey ’23.

For a photo essay by Thelen, see the spring 2023 issue of Northern Woodlands magazine.