What makes these ponds so special is that they are relatively safe, sheltered, and lack many predators. Large aquatic turtles, snakes, frogs and especially fish cannot permanently live there. Some may discover them and visit, but it is a safe haven for whatever smaller creatures can take advantage of the temporary water. The biggest danger though is that most of these creatures have to be able to complete their life cycles before the pools dry up. Some years, many may make it, other drier years, none may survive. Since many vernal pool creatures are both long lived and reproduce prolifically, there are enough good years to make up for the bad years.
So what are these vernal pool creatures? Well, the most often noted ones are certain species of amphibians, mole salamanders and wood frogs for example, but there are many others as well. Take for instance such tiny creatures and crustaceans as Water Fleas (Daphnia mostly), Springtails, and Cyclops. To most people these are just specks swimming in (or in the case of Springtails, on top) of the water. But these are favorite foods for other creatures. They escape most of these enemies by living in vernal pools, but they support other predators there.
Just a bit larger are the Fingernail Clams. As you may guess, they are rarely the size of even a fingernail. They are adapted to surviving buried in the mud when the pond dries. All of these are mostly detritivores and scavengers, feeding off the fallen leaves and other things rotting in the water.
|My son shows an aptly named Fingernail Clam.|
What vernal pools are most well known for are certain amphibians however. These have adapted to metamorphosing quickly into air breathing adults before the pond dries up (at least most years). They also require for the most part an undisturbed woodland very near by to provide food and shelter for the adults. Without both elements, these animals cannot survive.
|A pair of Wood Frogs in amplexus (mating position).|
|An aggregation od Wood Frog egg masses in a shallow vernal pool.|
|A Spotted Salamander being helped along its way to its natal vernal pool.|
|A Spotted Salamander egg mass with developing embryos.|
Marbeled Salamanders lay their eggs in the Fall or Winter. seeking their dry natal pools and laying their egg masses about half way up the banks. When the rains and melting snows (hopefully) fill the pools, their eggs are already there and they can emerge first. They then have a brief time when they can eat anything else smaller than them born in the water. By the time the Spotted Salamanders begin to out grow them, most have metamorphosed into air-breathing adults and have returned to the woods.
Vernal pools are very specialized habitats with their own collection of organisms that depend on them. These are indeed the only places these animals can survive. They may be temporary, but vernal pools are the only place these animals can survive and need to preserved rather than belittled because of their ephemeral nature. If you get a chance, visit one of these special places and wonder at the amazing world they can contain. Until then, here's a video of a vernal pool in action on the Capital Naturalist YouTube Channel: https://www.youtube.com/watch?v=eCo_J1__Qxo