Forest-dwelling salamanders and frogs come out from winter cover each spring to breed in vernal pools. The annual amphibian migration from woods to water usually takes place in March or April, often on a single “Big Night” when air temperatures above 40 degrees and recent rain create ideal conditions for their movement en masse. This year, a brief spell of unusually warm temperatures in February triggered the earliest date of amphibian migration activity recorded in this region since the New York State Department of Environmental Conservation (DEC) began keeping track of it in 2009.
Preliminary reports from volunteers with the Amphibian Migrations and Road Crossings Project, a collaborative effort between the DEC Hudson River Estuary Program and Cornell University, indicate that there were small numbers of salamanders and frogs on the move on Saturday, February 25 – at least two weeks earlier than usual. Volunteers in New Paltz spotted several wood frogs and two spotted salamanders. In the Town of Catskill, eight four-toed salamanders were logged into the record. A woodland pond in Westchester County was reportedly noisy with singing male wood frogs, and throughout the region, spring peepers were seen and heard, lustily peeping away in search of females.
According to the National Oceanographic and Atmospheric Administration (NOAA), last month was the second-warmest February on record in the US during one of the warmest winters ever. But March, as we know, has turned wintry again. What will happen to the frogs and salamanders that migrated early and now face snow and freezing temperatures? Are they able to hang on at the vernal pools until “real” spring arrives?
“That’s a good question,” says Laura Heady, DEC conservationist and land use coordinator who oversees the amphibian migration volunteer project. “Many amphibians are extremely cold-tolerant. Spring peeper, gray tree frog and wood frog all bury themselves under leaves in the forest during the winter, and can actually withstand freezing by using glucose as an antifreeze in their cells. But I’m not sure how the recent erratic weather will take its toll on amphibians that arrived early to the pools last month. Some may hunker down in the leaf litter at the bottom of the pools, where water temperatures are a little warmer than at the surface, but egg masses may be more vulnerable. It’s going to be an interesting season to observe vernal pools.”
There may yet be a Big Night to come, later this month or in April, when the majority of local amphibians make their move to their spring environments. It could also happen that the salamanders and frogs come out of the forest over the course of a series of nights; it’s all very weather-dependent.
Many of the amphibians making their way to vernal pools are on a timetable to lay their eggs. “Species like spotted salamander and wood frog are considered ‘obligate’ vernal-pool species,” says Heady, “because they’re dependent on the seasonal wetlands for their life cycle.” On the other hand, “When we see peepers moving on rainy nights in late winter and early spring, along with other amphibians, they are also moving from their overwintering habitat [where they hibernated] to breeding habitats. But spring peepers are more of a generalist species, considered a ‘facultative’ vernal pool species, as they can also use other aquatic habitats like marshes and ponds for breeding.”
Once they arrive, the males start “peeping” to attract females, which, like the chorus of wood frogs, Heady adds, “is always a welcome reminder that spring is on the way!”
Vernal pools are temporary wetlands formed from snow-melt and rain. The impermanent nature of the ponding (the pools dry up by summer) helps to ensure that amphibian eggs will be as safe as possible once laid there, with no resident predator population sharing the waters. But getting there safely is a challenge for amphibians. They travel great distances and face a virtual minefield of impediments along the way: easy prey for natural predators, and often killed by vehicular traffic at road crossings before they can make it to their destination.
The purpose of Heady’s project is to obtain data and help the amphibian population survive. Volunteers identify new crossings, document the migration and act as crossing guards, literally picking the animals up and moving them across a road to keep them alive. The mortality rate from traffic in the increasingly developed Hudson Valley is high.
Volunteers are advised to travel in twos, so that one person can keep an eye on traffic, and a bright light and reflective vest are advised. Volunteers must have clean hands, free of lotion and products like hand sanitizer, before handling amphibians.
Road mortality of turtles is also a significant concern in New York State, says Heady, with thousands killed each year during nesting migrations and many of the state’s native turtles in decline. “Their movements are primarily in May and June, when turtles leave their core habitats to dig nests in upland areas,” she explains. The DEC has suggestions on its website that motorists and residents can take to help turtles during these migrations.
For now, though, the focus is on the Amphibian Migrations and Road Crossings Project – specifically on the amphibians that move from their forest habitats to vernal pools for breeding in late winter and early spring. “This group of salamanders and frogs is also of conservation concern,” says Heady. “But with amphibian migration often concentrated on several warm, rainy evenings each year, volunteers can make a difference, covering large areas and helping hundreds on the move in just a few nights.”
Information on participating in the Amphibian Migrations and Road Crossings volunteer project can be found at www.dec.ny.gov/docs/remediation_hudson_pdf/amrc2017.pdf