Posted on March 16, 2017 by Jim MacDougall
March - Thaw Creates Vernal Pools
Vernal pools are much more than places where amphibians breed. These isolated flooded basins in the ground are a life-saving oasis for many animals during a long cold winter. When the amphibians arrive in April, they become tasty omelets dropped into a frozen desert.
A vernal pool is the interface of groundwater with the atmosphere, the phreatic zone with frost, the ecotone of earth and water. The pool's margin is the recharge of warm groundwater to a frozen surface. This water may be the only source of fresh water for a mile or more during the coldest part of winter. All active winter creatures will seek it out. The pool is akin to the water hole for the pride of lions in a drought-prone savanna, a place to drink and a place to catch food. Deer, mink, raccoons, fisher, fox, coyote, voles, shrews and mice all visit the edge of a vernal pool to stay alive during the winter.
And they are ready and hungry by late March and April when the mole salamanders migrate out of the shrew's burrow and into the fishless pool for their annual courtship. Wood frogs, Spring Peepers, American Toads, Grey Tree Frogs, Green Frogs and Red-spotted Newts all join in. When they lay their eggs, they dump a huge mass of protein, the first real food of the new year. Spotted turtles walk miles to dine on these eggs, along with diving beetles and water snakes. The nutrients of the eggs feed algae and phytoplankton that are grazed on by tadpoles, copepods and caddisflies.
But the real show is the salamanders themselves. Up to 8 inches long and as fat as your thumb, these fossorial creatures chance it all by walking overland on cool, rainy March and April evenings to breed. It is worth the effort to see this at least once in your life. To make it a habit may cause too much damage to a local population. Easily accessible vernal pools can be found at the Tompson Street Reservation / Gloucester, Farnsworth Reservation / North Andover and Willowdale Meadow / Topsfield.
A Field Guide to the Animals of Vernal Pools Leo Kenney and Matt Burne.
Vernal Pools Betsy Colburn.