Vernal Pools…where life begins.

Vernal Pools

If you hike the woods in early spring, you have likely heard the chorus of frogs on warm rainy days, coming from swampy woodland pools. Natural History of Vermont Class requires every student to do a “herp” project, monitoring reptile or amphibian movement in one of the citizen-scientist projects around the state. I chose the Vermont Center for Ecostudies Vernal Pool Mapping Project (VPMP.

Vernal pools, as the name implies are woodland depressions that fill up in spring with snowmelt and rain. They are ancestral breeding grounds for some frog and salamander species. In a perfect year the pools remain wet just long enough for the larvae to become adults, drying up in the summer, making them unsuitable for fish—major predators of eggs and larvae. Survival rate is small from egg to larvae or tadpole, to frog or salamander adult, yet it only takes two survivors to replace the parents. Used year after year, these pools are revisited by wood frogs (Rana sylvatica), spotted salamanders (Ambystoma maculatum), Jefferson salamanders (Ambystoma jeffersonianum), blue-spotted salamanders (Ambystoma laterale), and tiny upside down swimming fairy shrimp. Females are known to disperse farther than males after breeding, so the genetic mix remains healthy.

 

I located a few possible pools on the VPMP topographical maps, three within hiking distance of my house, one, which I knew to be active. Knowing wood frogs to begin breeding early—even with snow on the ground, I began snowshoeing in to the study areas in late March. Nothing was stirring until April 21, a warm, rainy evening. I could hear them from a hundred yards away—fifty or more male wood frogs, little reptilian heads sticking up out of the water calling. Occasionally a larger female approached and the struggle for amplexus began, the male grasping the female from the back, hoping to be accepted. If she responded, he would release a cloud of sperm into the water as she lay her eggs on a barely submerged twig.

I returned the following evening, expecting yet more activity, but all was quiet. I sat in the light, warm rain, with my camera under my jacket for what seemed like an hour, just looking at the water, hoping something would stir. There, before my eyes, appeared the egg masses laid the night before, thousands of tiny eggs in clumps, forming larger clumps, all clinging to thin shrub branches that emerged from the water. Some masses appeared dark, and some looked white. I rolled up my pants legs and waded in, gently scooping up the globs of tiny black dots to photograph.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Returning every few days, I found what looked like furry nerf-balls, white, gelatinous egg masses on braches that lay a bit deeper in the pool. These were spotted salamander eggs. Salamanders are nocturnal; I never saw any of the adults. In an overflow pool, mosquito larvae, that look like eyeballs with tails and fringed neck collars sprung up and down on decaying leaves that had the white globular spots of salamander spermataphores.

Two potential pools at a nearby farm proved to be muddy, with no eggs or signs of frogs. Nearby tractor tracks showed this area to be used for farming, sugaring, and brush clearing. Perhaps the two pools were active at one time and have been drained, or perhaps they just appeared to have possible characteristics from an arial map, but never were.

I did stumble upon two previously unmapped pools on a hike behind the Justin Morrill Homestead. I happened to notice the reflection of water in the woods and found two classic vernal pools with egg masses.

If you would like to get involved in this project, contact Steve Faccio at sfaccio@vtecostudies.org or check out the Vermont Center for Ecostudies (VCE) web site http://www.vtecostudies.org/