Across Vermont, the songs of spring peepers mark the change in seasons. Temperatures rise, snow melts and water runs into the dips and divots of the land to form vernal pools.
Biologists call those springtime basins the coral reefs of the forest — and their emergence helps explain why spring peepers and other frogs get so vocal this time of year.
The fishless bodies of water are vital to the survival of reptiles and amphibians, known together as herptiles or herps, and provide safe breeding grounds for species such as wood frogs, spotted salamanders and, to a lesser extent, the peepers. Without fish around to eat herptiles’ eggs, breeding can boom.
In early spring, forests are dry and barren. Vernal pools spread nutrients across the landscape, serve as sites for photosynthesis and help manage flooding by providing a place for water to settle.
It all makes the pools a prime destination for species such as herps. But the journey often is not easy.
On rainy nights, when temperatures reach above freezing, herps leave their winter habitats to head toward vernal pools — and frequently attempt to cross busy roadways, said Jim Andrews, a herpetologist who manages the Vermont Reptile and Amphibian Atlas.
Those migrations, known around the country as “Big Nights,” see hundreds of herps per hour crossing roads to reach the vernal pools.
To protect the creatures and reduce casualties, volunteers across Vermont gather on those nights to help herps traverse the roads. Most often, that entails people scooping critters into their hands and shuttling them to safety.
They also collect data.
“We record the number of herps we see, the species, how many are dead or alive and the sounds we hear,” said Ira Powsner, an assistant at the Vermont Reptile and Amphibian Atlas.
The info collected by these volunteers is used by the atlas and the Vermont Center for Ecostudies to track the location of the vernal pools and the herps statewide.
Despite those efforts, vernal pools and their herp inhabitants face increasing threats as the result of both climate change and human development.
"We're seeing changes in hydroperiods," said Kevin Tolan, a staff biologist at the Vermont Center for Ecostudies, referring to times when land is waterlogged.
Less snowfall and warmer winters shrink spring runoff and dry up vernal pools, leaving less time for herptiles to breed successfully and survive.
Early warm spells often cause herps to migrate too soon, only for temperature to drop again and cause more deaths.
Increased flooding across the state — also tied to climate change — has effectively sterilized streams, cleaning rocks and getting rid of leaf matter and other organic material that herptiles rely on for food, Andrews, the atlas manager, said.
Flooding also flushes salamanders downstream, killing many. Those that survive and return to their homes find them unsuitable.
Development often isolates breeding areas, forcing herps to make dangerous road crossings during their migrations.
Building over vernal pools directly destroys the basin herptiles rely on. Development within 400 to 500 feet of a pool, known as the "life zone," can significantly disturb their habitat, Tolan said.
Still, Vermont's herptile populations remain healthier than those in many more heavily developed states.
Only a few herptile species, such as the boreal chorus frog and Fowler’s toad, are believed to have disappeared in Vermont in recent decades. The frog, for example, hasn’t been seen or heard here in over 25 years.
In 2019, the Vermont Center for Ecostudies launched the Vernal Pool Monitoring Project to track herptile populations. Volunteers visit pools throughout the spring, recording egg masses, frog calls and water temperatures to monitor the timing of events and population trends.
Protecting herp habitats, after all, first requires identifying them.
“Vernal pools qualify as protected wetlands, but they must be officially mapped and documented,” Tolan said.
Citizens play a growing role in conservation by helping with monitoring and crossings, or by submitting sightings through platforms like iNaturalist.
Projects including road closures on rainy nights and organized crossing events also help raise awareness of the importance of herp migrations. And groups statewide keep the conversation going. University of Vermont students run a club dedicated to herps. Last month, a crew of people came to Huntington for a new Audubon Vermont event called “Women Who Herp.”
In Monkton, wildlife underpasses have been installed to help animals safely cross busy roads, reducing roadkill and preserving migration routes, Andrews said.
“Introducing people to herptiles is key to conservation,” he said.
The Community News Service is a program in which University of Vermont students work with professional editors to provide content for local news outlets at no cost.
