Posted on March 14, 2017 by Neil Ungerleider
Vernal pool photo by Nicholas Tonelli/WikiCommons
Early spring means the thawing of vernal pools and the annual creation of a unique wildlife habitat for the amphibians and invertebrate species that rely on them for breeding.
Vernal pools, which are common throughout Massachusetts, are essential to the breeding of some species because they offer an environment safe from fish, predators that might otherwise eat the eggs laid there.
Because vernal pools are either dry or sharply lower by summer, they prevent fish from establishing permanent populations, which is critical to the species that rely on the vernal pools.
Fairy Shrimp photo by Pacific Southwest Region/WikiCommons
While many species may occasionally use a vernal pool as a place to lay eggs, others, called obligate species, require them to complete their life cycle.
In Massachusetts, the obligate species are the spotted salamander, blue-spotted salamander, marbled salamander, wood frog, Jefferson salamander and fairy shrimp.
The edges of the pool thaw first and become the most valuable areas for breeding. It not only provides the earliest breeding ground, but the water remains warmer throughout the spring and summer.
Blue spotted salamander photo by Iron Chris/WikiCommons
While fairy shrimp, a small one-inch crustacean, spend their short life of just a few weeks in the pool, other species that rely on vernal pools live in moist woodlands.
The wood frog heads toward vernal pools in early spring, lay their eggs and then return to the woodlands that are their homes. Their tadpoles develop, grow in the pool and eventually join the adult frogs in the woodlands.
Wood frog photo by DDauri Daniel D'Auria/WikiCommons
Salamanders will migrate to vernal pools, mate and lay their eggs. In an example of nature’s exquisite timing, the young salamanders emerge from the eggs just as the pool is drying. They likewise head for the forest floor.
Massachusetts requires that obligate species be present for a formal designation as a vernal pool. Many are protected under the Massachusetts Wetlands Protection Act.