Vernal pools are seasonally fresh- water flooded depressions, usually filling with water in the spring as water tables rise in the spring. Although some depressions are filled in the fall, and may be referred to as “ autumnal pools “, the vernal pool in Connecticut contains water for about two months during the growing season. It typically has no outlet stream, and no fish populations are found in them. Most years, vernal pools dry out completely by late summer.
Vernal pools are rich breeding areas for many amphibians. Some of these amphibians need to complete at least part of their life cycle in the pools before reaching adulthood. Look for eggs of the various amphibians that will be born there starting in late March through early April. Among them are wood frogs, spotted salamanders, marbled salamanders and gray tree frogs, and to some extent spring peepers, American toads and red-spotted newts.
Spotted salamanders and wood frogs lay their eggs in vernal pools in the spring, and the nymphs need time to develop into air- breathing amphibians before the pools dry up. A droughty spring can mean disaster if the early stages of the amphibians still have gills and the pool dries up. This spring started off droughty, but recent rains may have helped prolong the length of water retention in Connecticut pools.
If you are adventurous, spend some time looking under logs and leaves in areas surrounding vernal pools, even after the pools have dried up. You may be rewarded with some good finds. On one recent log rolling venture, my sister and I uncovered many red- backed salamanders. The day after a rain you may find red- spotted newt efts and box turtles, especially near woodland vernal pools.
The red- spotted newt has a complicated life- cycle. It hatches from an egg laid in the spring under decaying leaves in a pond, then lives as a carnivorous larvae with a finned tail and gills, much like the spotted salamander. But the red-spot undergoes metamorphosis into an eft form later in the summer where it has lungs and lives outside the water for several years. Then it undergoes a second metamorphosis into its final adult form where it finishes its life in the water.
Spotted salamanders on the other hand spend little of their time in the water. Eggs are laid in large clumps in vernal pools after adults migrate from burrows in the wood during winter rains. The aquatic form of this salamander can sometimes be mistaken for polliwogs by the casual observer. Their development into terrestrial forms depends upon the water temperature. The warmer it is, the faster these salamanders develop into the land- dwelling form. After they move to land, they are seldom seen as they are of a nocturnal habit, dwelling in hardwood forests and swamps. This salamander depends upon vernal pools or wetlands where no fish are found that would feed on the eggs and larvae.
Wood frogs are among the first breeding animals to arrive at the vernal pool. Listen for their loud quacking and shortly after look for their Wood frogs lay eggs prolifically in vernal pools. The egg masses of wood frogs are usually attached to vegetation near the surface of the water and may-cover the surface of the pool if wood frogs are in abundance. They can survive in pools that dry up by August as the tadpole stage typically is completed by mid- June to mid-July in Connecticut.
There are many other things found in and around vernal pools that we can observe and appreciate. The next time you here incessant quacking in the woods in early spring, remember the wood frog. And think about all the drama about to unfold as the melting snow and rising water table provide the perfect environment for the unheralded amphibians of the woodlands.
All pictures Copyrighted 2013 by Pamm Cooper