 |
 |
 |
|
|
|
|
By Kristen Lamb, Education & Outreach Director
Vernal Pools are formed in depressions in our forests. In the Northeast, a vernal pool fills with water because of the rising water table of fall and winter, or with the melting water from the spring thaw of winter snow and ice. It is an important ecosystem of our forests, and without it our entire ecosystem would not be complete. Several species of amphibians are obligate vernal pool species, which means that they need to use a vernal pool for various parts of their life cycles. Because vernal pools are a temporary habitat (only wet for 3 seasons), the species associated with vernal pools very cleverly only use them for some or part of their life cycles. The other parts of their life cycles are spent out and about in other habitats, playing an important role in those ecosystems as well, where other plants and animals interact with and sometimes depend on them for food or other reasons. Thus the vernal pools are connected to many of our other forest habitats, as well as the larger ecosystem that we call New England. The loss of vernal pools and their species would mean a local loss of amphibian species, a decrease in biodiversity, and a decline in food available for many other animals that live around them. But what about us? Don’t worry, we are connected too. Besides bringing us joy through observation, a beautiful spring chorus, and the fact that they have been here longer than us, these species and microhabitats unknowingly help to keep our air and water clean. Because the vernal pools are filled through drainage of the water table, what we put down our drains at home, what leaks out of our cars, what we put on our lawns, and what we put on the roads among other things can eventually make its way to our vernal pools.
Let’s take a look at who is using these pools and what their roles are. Because of its unique environment, many rare species are able to thrive here. Believe it or not, there is an entire ecosystem thriving inside of a healthy vernal pool. To clarify, there are obligate vernal pool species (those that are unable to complete their life cycles without vernal pools), and facultative vernal pool species (those that can use vernal pools to complete their life cycles, but are able to use other water bodies as well). The absence of fish in vernal pools (because it dries up in the summer) allows for a rich diversity of amphibians and invertebrates found here. Among obligate amphibians are the wood frog, spotted salamander, and the blue-spotted salamander. Obligate invertebrates include the fairy shrimp. Facultative species include the spotted turtle, Blanding’s turtle, painted turtle, wood turtle, snapping turtle, Eastern ribbonsnake, Northern watersnake, common gartersnake, spring peeper, gray treefrog, American toad, Fowler’s toad, green frog, pickerel frog, leopard frog, bull frog, red-spotted newt, dragonfly larvae, mosquitoes, damselfly larvae, water boatmen, backswimmer, and clam shrimp, and many more! Mallards, wood ducks, raccoons, egrets, hawks, warblers, bats, and others use vernal pools as a seasonal source of food and water. Threats to vernal pools include housing development, roads, or a loss of tree cover in surrounding habitat. This can lead to decreased shading, rising water temperatures, decreased oxygen content, increased evaporation, and shorter flooding cycles, impacting the delicate creatures that call the pool home.
Let’s take a look at how one particular species may use a vernal pool throughout the year. We’ll focus on the spotted turtle. At 7 to 14 years old, if she manages to survive all the hazards she will face in her “childhood,” a female is finally ready to lay eggs. In May or June she will leave her wetland or vernal pool and find a nice sunny, moist spot with well-drained soil in which to lay her eggs. Using her hind feet she will dig a nest and lay 1 to 8 eggs in her clutch. The turtles will hatch in August or September, but most likely will remain in the nest until spring. After laying the eggs she will travel back to her wetland or vernal pool area. Moving on land can be very dangerous for a spotted turtle as they are vulnerable to clever raccoons. The pools offer an escape route as they are able to dive down quickly and hide under leaves and other vegetation. In the fall the spotted will make her way back to her hibernacula which occurs in a variety of wetland habitats including vernal pools. Her winter home may be a structure made from clumps of cattails, grasses and sedges, or submerged cavities created by rocks and tree roots. She also may choose a soft winter den inside of elevated mats of sphagnum moss. Cozy! She will fuel up for hibernation with everything her pool has to offer. Algae, water lily seeds, worms, mollusks, crustaceans, adult and larval insects, and amphibian eggs provide the perfect fall feast. As the temperatures start to drop, and fall turns to winter, her body processes will slow down and she will remain in her hibernacula until spring. Emergence in Maine usually occurs from late March to May, depending on the temperatures. She may very likely be awakened by her neighbors the wood frogs who are typically the first early risers to emerge. She will be slow to wake up, and probably won’t start to feel hungry until water temperatures reach 15 degrees C. She will spend the spring feeding in her vernal pool, and if it dries up she will venture to another one close by. She will find a mate early in spring, mating in the water. In May and June she will hopefully lay another clutch and do it all over again!
There are several actions we can take to help protect vernal pools, on small and large scales.
Here are a few ides:
Copyright © 2007 The Center for Wildlife
P.O. Box 620
Cape Neddick, ME 03902
(207) 361-1400