SHARON - "It's slimy and amazing!" said 11-year-old Michael Kennedy after ferrying a spotted salamander safely across the road on a damp night last week.
He and a half-dozen of his cousins from Walpole scanned Moose Hill Street with flashlights, questing for salamanders along the road that runs through the 2,000-acre Moose Hill Wildlife Sanctuary.
His uncle, Stewart Sullivan, said his family has been bringing their children here for generations on the first warm wet nights of early spring, searching for - and protecting - salamanders that emerge and march to vernal pools to lay their eggs.
Salamanders are homely but appealing creatures. With bulging eyes and mouths that turn up into permanent smiles, they look a bit like moist Muppets.
While half the state's 11 native salamander species are listed as threatened or of special concern, some, such as the spotted salamander, have turned out to be surprisingly common. A formidable 8 inches long with neon yellow spots in a pattern unique to each individual, the spotted salamander is one of New England's best-kept secrets because it lives underground.
About the only time to see it is on rainy nights when the temperatures are above 40 degrees, between mid-March through this week. That's when they surface to march on stubby little legs to vernal pools to reproduce, said Stafford Madison of the Boston office of the US Environmental Protection Agency. Also on the march are their rarer cousins, the chocolate brown Jefferson salamander and the smaller, blue-spotted salamander.
Some towns, such as Sharon and Framingham, will allow key roads near vernal pools to be closed on prime salamander migration routes a few nights a year, but peak nights are hard to predict. Because they must remain moist at all times to breath through their naked skin, these three types of mole salamanders won't leave their tunnels if conditions turn too dry or windy, as well as too cold, said state aquatic ecologist Marea Gabriel in a phone interview.
If weather conditions are just right, and most years they are, thousands can surface at once and head for the pool, sometimes following one another nose-to-tail like elephants in a circus. When this happens, it's called a Big Night. When there's no one perfect night, they will venture forth a few at a time over many nights.
On Big Nights at the vernal pools, aquatic swirling balls - or "a congress of salamanders" - can collect, with males rubbing up against females as part of courtship. "They're all together turning and twisting in the water," said Christine Turnbull, Moose Hill sanctuary director, "but you need a strong light to see it through the rain spattered water surface."
Sexy time for salamanders is a virginal affair, however. First the males drop cottony wads called spermatophers in the pool and then the females pick up the sperm with their cloacal lips and use it to lay fertilized eggs, which, in the case of spotted salamanders, are in very firm, gelatin-like masses. (Blue-spotted salamanders lay eggs singly, while Jefferson salamanders lay long egg masses attached to vegetation.)
Most spotted salamanders live in woods within a half-mile of the vernal pools where they were born. These are depressions that temporarily fill with water in spring but usually turn to mud or dry leaves by summer. This means there are no fish populations to feast on the salamanders eggs.
But there's a trade-off.
The young hatchlings are in a race against time to become air breathing before the pools dry up, which is why their parents try to mate as early in spring as weather allows. If there's not enough rain in a given year, an entire generation of salamanders can literally evaporate. Since individual salamanders can live 20 years, the species can survive a couple of dry springs in a row.
Automobiles are a greater threat, and homeowners and developers who fill in vernal pools or cut down surrounding woods are the greatest threat of all.
Though some vernal pools are no bigger than table tops, they are hugely productive as rich nurseries for salamanders, small frogs, toads and invertebrates such as fairy shrimp that are called "obligate breeders" because they can reproduce nowhere else.
For optimal protection by state and town legislation, most vernal pools need to be certified by the state Natural Heritage & Endangered Species Program. "But most have yet to be certified, so some salamander watchers submit photos of breeding activity in vernal pools to help document and preserve the pools," said wetland consultant Tom Palmer of Milton. (Visit nhesp.org or call 508-389-6371 for more information on vernal pools and their certification).
Warm, rainy spring nights also bring out the other vernal pool breeders such as wood frogs and those loud spring peepers. Last week, Kennedy cousin Abigail Sullivan, 13, was gently poking a wood frog to keep him moving across the road toward a vernal pool. "Have to keep going!" she crooned. "Almost there!"