A friend of mine called me at the office the other day having discovered a six inch long, yellow spotted salamander in her garage. Those vernal urges must be increasing with the warmer nights. There can still be ice in the vernal pools, but when warmer ambient air temperature combines with rain, the wood frogs and salamanders start to move. Today there is a steady, cold rain and the temperature is in the low 40s. By tonight, the spring amphibian migration could be well underway.
My friend Shep Evans of Stockbridge, MA has an annual contest for the first spring peeper heard in our area. Each evening as I drive home from work, I pause at Robbin's Swamp in South Canaan and listen for the croaking chorus. It is the surest and most exuberant sign of Spring and one I remember fondly from my childhood.
There are several waves of spring Amphibian migrations. Those dependent on vernal pools -Wood frogs, Jeffersons, Blue-spotted, Yellow-spotted and Four-toed salamanders- head through the woods to their accustomed ephemeral wetlands very early in the season. Spring peepers are also out early but can reproduce in other kinds of wetlands. Many frog species in our area migrate throughout April, joined by toads and newts in early May and Bullfrogs in June. On rainy nights there are sections of road that are littered with hopping, skittering and -regrettably - squashed amphibians. Local volunteer networks sometimes monitor heavily traveled migratory crossings and assist the frogs and salamanders on their journey to the opposite side of the road.
Vernal pools are those temporary bodies of freshwater that support breeding populations of dependent species such as wood frogs or fairy shrimp. They seldom hold water year round and often dry completely as the season progresses. As a rule they do not support fish species, thus removing a major class of egg predator from the system. These temporal wetlands are highly significant for maintaining amphibian populations, many species of which are listed as threatened by state wildlife agencies. The Jefferson's salamander hybridizes with the equally uncommon Blue-spotted salamander in this region, while the Northern spring and Four-toed salamanders are on many rare species lists in the Northeast.
Different states afford varying degrees of protection to vernal pools. In Massachusetts, those vernal pools that are certified enjoy a modest buffer, and human activities within that zone receive deeper scrutiny. Some Berkshire foresters have found approval of their cutting plans subject to substantial restrictions when logging in the vicinity of vernal pools. In Connecticut, vernal pools do not enjoy specific state-wide protection, as regulated wetlands are delineated in this state based on hydric soils. Some studies indicate that clearing around vernal pools or drilling residential wells nearby can increase evaporation of vernal pools or lower the water table to levels that impact reproductive success of larval frogs and salamanders. There is a vernal pool in Wareham MA where my grandmother lives that sometimes dries before tadpoles are fully developed. An entire brood year is lost when that happens, an impact that some species can ill afford.
Students and faculty in Reading, MA, have gotten into vernal pool conservation in a big way. The publication "Wicked Big Puddles" that Leo P Kenney and these students developed is a manual for certification of vernal pools and a terrific environmental outreach tool for young and old. I'll be out in the woods in the coming weeks using it with my children, looking for egg masses clumped around submerged branches or streaming up from sunken logs in the dark water. If we find reporducing wood frogs or fairy shrimp, we'll know we've found a vernal pool.