The big night: vernal pools

Shep Evans up in Stockbridge, Mass., has an annual contest for whomever hears the first spring peeper of the season in the southern Berkshires.  Though Litchfield County falls below that line of demarcation, I still pause at Robbins Swamp in Falls Village on my way home from work to listen for that sweet squeaking chorus. Peepers are among the first amphibians to move from their winter quarters to find dark waters to breed. Their song is the surest and most exuberant sign of spring, and one that has stirred my heart since I was very young and first learned that peepers were teeny frogs.   

There are several waves of spring amphibian migrations, starting with The Big Night in late March or early April when the rain falls and mercury rises above 40 degrees.  In one of Earth’s great movements of wildlife — and one that few people note, though it happens in their backyards —  wood frogs, spring peepers, gray tree frogs and mole salamanders start to move in great numbers to their breeding pools.  

Other frogs emerge throughout April, with toads and newts in early May and bullfrogs bringing up the rear in June.  The early frogs and salamanders therefore avoid some of their bigger, more gluttonous competition. 

In western New England we have three species of mole salamanders — the yellow spotted, blue spotted and Jefferson varieties — that, along with wood frogs and fairy shrimp, depend on vernal pools to breed.

Vernal pools are unique wetland habitats that usually dry out completely as the season progresses. They do not support fish species, thus removing a major class of egg predator from the system.   

These intermittent wetlands are highly significant for maintaining amphibian populations, many species of which are listed as threatened by state wildlife agencies.  

The Jefferson salamander hybridizes with the equally uncommon blue-spotted salamander in this region, so I’m never quite sure which one is which when I find one; but both are considered rare species of special concern.

Different states afford varying degrees of protection to vernal pools. In Massachusetts, certified vernal pools enjoy a modest buffer, and human activities within that zone receive deeper scrutiny. In Connecticut, vernal pools do not enjoy specific statewide protection, and they are often too small to appear on the hydric soils maps that delineate regulated wetlands in the Nutmeg State.  

Towns that undertake Natural Resource Inventories often try to rectify this omission by identifying their vernal pools, with volunteers looking for egg masses clumped around submerged branches or streaming up from sunken logs in dark water.

On warm rainy nights in early spring, there are certain roads in our area that are littered with hopping, skittering and — regrettably — squashed amphibians.  Volunteers sometimes monitor heavily traveled crossings during the migration and assist the frogs and salamanders on their journey to the opposite side of the road. My children and I look forward to being out one evening very soon when The Big Night arrives, “saving Spotty†and its many relations.

Tim Abbott is program director of Housatonic Valley Association’s Litchfield Hills Greenprint. His blog is at greensleeves.typepad.com.