On a cold night in late February or early March, with the rain and sleet pounding on the roof, the last thing most people would think of would be venturing out to wade through a big puddle. On these nights, however, a migration is occurring along the Blue Ridge Parkway. The migrants are amphibians - frogs and salamanders - and they are on their way to usher in the coming of spring. The puddles are vernal pools, bodies of water ranging from as small as a closet up to several acres in size. "Vernal" refers to spring, and the majority of these pools are temporary, being filled with water for only a short time during the spring. For this reason, many people don't really think of them as true wetlands, or as valuable parts of the ecosystem.
They are critical breeding sites for many species of amphibians, including wood frogs and spotted salamanders. These species are terrestrial most of their lives, except for during the breeding season when they congregate in vernal pools. Wood frogs (Rana sylvatica) are generally out first in February and can be identified near the pools as their "quacking" calls are heard. They call, mate, and deposit egg masses. They are soon followed by the spotted salamander (Ambystoma maculatum), a member of the mole salamander family, which spends its adult life underground. Other species may use vernal pools, including American toads and spring peepers, but the wood frog and spotted salamander utilize vernal pools almost exclusively. The temporary nature of the vernal pool means that many species of predators, such as fish, will not survive the dry periods. This is a distinct advantage if you are looking for a nursery and don't want your young eaten. However, in years of drought, the pool may not contain water at all, or may not sustain water long enough for the young to hatch and metamorphose into terrestrial forms. It is a gamble, with the payoff being a new generation of young. But even if the water dries up it is likely that the adults will probably live long enough to return next year and try again. A risk to the frogs and salamanders includes being run over by vehicles while crossing roads to get to vernal pools. Perhaps the greatest risk, however, comes from humans who fill in pools and who dig ditches to drain the pond. Such actions can lead to local "silent springs" without the familiar calls of our native frogs.