May flowers are not all that April's showers bring in Maine. Heavy rains accompanied by the first unseasonably warm temperatures also herald one of the Northeast's most spectacular, if unseen, wildlife migrations. Emerging from under their deep, leafy forest retreats, legions of Maine's wood frogs and spotted mole salamanders (so named for their tendency to spend most daylight hours underground) move en masse toward small woodland pools marking one of the first signs that spring has finally arrived.
Up to 9 inches in length and sporting a seemingly unnatural yellow, polka-dotted pattern across a polished black body, the yellow spotted salamander would be hard to miss were it not for the fact that it spends most of its life in small mammal burrows or under fallen logs, far from the wooded pools it breeds in. Similarly, wood frogs recognized by their dark, raccoon-like mask and tan or chocolate-colored bodies, may travel ¼ mile or more in their efforts to return to the very same forest pool where they transformed from an aquatic tadpole to a terrestrial frog some one or two years before.
While perhaps unnoticed, be assured that the abundance of pool-breeding amphibians (frogs, toads, and salamanders) occupying the forest floor around some woodland pools can be tremendous. Indeed the collective weight (or "biomass" as scientists refer to it) of these unseen spring sentinels has been estimated to exceed that of all birds and mammals combined in some forests with productive breeding pools! Their sheer abundance and palatability (to fox, raccoon, skunk, coyote, snake, hawk, and just about any other forest predator that finds them) has many ecologists convinced that the terrestrial wanderings of these pool-breeding frogs and salamanders play a powerful role in the local ecology of our forests and woodlots.
Wood frogs, spotted salamanders, and blue-spotted salamanders are part of a specialized fauna in Maine that breed almost exclusively in small, isolated forest pools that are fed by spring rains and melting snow but dry partially or completely by late summer. These ephemeral spring wetlands, referred to by ecologists as "vernal pools", are exploding with the sounds and movements of ducks, frogs, salamanders, turtles, snakes, dragonflies, fairy shrimp and other creatures early in the year, but lie surprisingly empty and dormant by late summer.
What makes these fleeting pools so attractive to the wildlife that breeds there is the fact that they lack fish. Isolated from streams and subject to periodic drying, vernal pools provide a nearly predator-free haven for frogs, salamanders and invertebrates that lack the defenses necessary to reproduce in more fishy environs. Of course, in nature every lifestyle bears inherent tradeoffs, and for those choosing ephemeral pools life is a constant race against the drying clock of summer. In severe drought years, such as last, vernal pool-breeding species may suffer catastrophic losses if their home dries up before larval stages can complete development and transformation into terrestrial juveniles. However, the adult stage of pool-breeding amphibians is long-lived, and these species are adapted to withstand occasional years of drought when few juveniles are recruited into the population.
Less certain than the rain is whether the vernal pools themselves will survive to greet another spring migration of forest-dwelling frogs, salamanders, and turtles. Residential development and urban sprawl are taking its toll on wetland habitat, particularly in southern Maine where some towns have recorded population growth rates of up to 30% in just the last ten years. While open space for all of Maine's wildlife suffers from unplanned and unchecked development, smaller wetlands, such as vernal pools, are being lost and degraded at an especially high rate. Part of the problem stems from a gap in current state wetland laws, designed primarily to protect wetlands over 1/3 acre in size. Unfortunately, most vernal pools are smaller than this, thus receiving little or no protection from current wetland laws.
The Department of Inland Fisheries and Wildlife is cooperating with the Department of Conservation, State Planning Office, Maine Audubon Society, and the University of Maine to identify potential strategies for protecting the unique wildlife values associated with smaller wetlands that currently "fall through the cracks" of state wetland laws. Workshops on vernal pools continue to be held throughout the state for land managers, educators, land trusts, and landowners.
In 1999, a Maine Citizen's Guide to Locating and Describing Vernal Pools was updated and republished with help from the U.S. Environmental Protection Agency and is available to the public from IFW and Maine Audubon Society. Habitat Management Guidelines for harvesting timber around vernal pools have recently been completed and will be available for distribution this summer. Voluntary guidelines for mitigating impacts from urban and residential development near vernal pools are also scheduled for completion this spring. Finally, a state-sponsored vernal pool-working group is close to finishing a definition for "Significant Vernal Pools", a new Significant Wildlife Habitat designated under the state's Natural Resource Protection Act. If you would like to learn more about the availability of these projects please contact IFW at 287-8000.
|Back to News||Home||Print This Story|