Vernal Pools - A Vanishing Resource
May flowers are not all that April's showers bring in Maine. Heavy rains accompanied by the season's first warm temperatures also herald one of the Northeast's most spectacular, if unseen, wildlife migrations. Emerging from under their deep, leafy retreats, legions of Maine's wood frogs and spotted mole salamanders (so named for their tendency to spend 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 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, 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 their lack of 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 vernal pool-breeding species may suffer catastrophic losses if their home dries up before larval stages can complete development and transformation into the terrestrial-adapted juvenile phase.
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 and coastal 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 regulations.
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 and a state-sponsored working group is continuing to work on a definition for "Significant Vernal Pools", a new Significant Wildlife Habitat designated under the state's Natural Resource Protection Act.
Additionally, the Department has cooperated with Maine Audubon Society and University of Maine to produce several new publications designed to provide landowners voluntary techniques and recommendations for protecting vernal pools and their wildife values. The Maine Citizen's Guide to Locating and Documenting Vernal Pools provides a comprehensive introduction to recognizing and monitoring vernal pools, including color photographs of the indicator species. Also now available to the public are two complementary guide-books for protecting vernal pool habitat during timber management (Forestry Habitat Management Guidelines for Vernal Pool Wildlife) and during residential and commercial development (Conserving Pool-breeding Amphibians in Residential and Commercial Developments in the Northeastern United States). All of these guides can be obtained by contacting Becca Wilson at Maine Audubon Society (207-781-6180 ext. 222; [email protected]).
The Amphibians, Snakes and Turtles of Maine
Reptiles, such as snakes and turtles will appear later, and they can be found basking in sunny spots. Your best bet is to find southern facing rocky slopes on sunny days in late April and May. In the summer, you can still find amphibians and reptiles. Sunny afternoons are great time to search for reptiles, and rainy nights are the best time to find amphibians. Shorelines, where aquatic and terrestrial habitats converge are an excellent area to search. Paddling or walking along the shore can bring a discovery of turtles, frogs and snakes. Banks of woodland brooks are prime habitat for salamanders, look under stones to find them, and remember to always replace the stone in the same position to preserve their habitat.
The Department of Inland Fisheries and Wildlife recently produced a series of posters on Maine's turtles, snakes and amphibians, which offers timely information concerning these species with warmer weather now here. The posters feature full color photographs on the front for identification, and on the back side of the poster, there is a biological summary of each species, including range, habitat, breeding information, and threats.
Amphibians in Maine include frogs, toads, salamanders and newts. The word amphibian comes from the greet word, Amphibios, which means living a double life, and that is just what most amphibians do.
Some amphibians live in forests and fields, but most times you will find them in moist habitats such as rotting logs, small mammal tunnels, and spaces such as tree hollows. Most of Maine's amphibians breed and lay eggs in streams, wetlands, and vernal pools and young amphibians are characterized by gills.
Most amphibians are sensitive to drying out, which is why they seek damp or moist areas to live. However, amphibians have special skin that helps them stay moist by secreting fluids, and that is what gives their skin a slimy feeling whey you touch them.
Frogs and salamanders are most active on rainy days and nights, when it is easiest to keep their skin moist. An amphibians need to live in both land and water exposes them to many risks that are associated with development such as habitat loss, pollution, ozone depletion and disease.
The turtle poster features seven turtles that are found in Maine. It includes the two endangered turtles in the state, the Blanding's and Easter Box Turtle, as well as the spotted turtle, which is listed as threatened in Maine. The common musk turtle and the wood turtle are species of special concern in the state, and the common snapping turtle and the painted turtle area also featured.
Turtles belong to an ancient group of animals that have been present on earth for more than 200 million years, long before the appearance of mammals on the scene. One thing everyone recognizes on turtles is their shell, which helps protect turtles from natural predators. However, the shell offers little protection against newer human threats such as cars, pets and habitat loss.
Probably no other group of animals brings forth the reactions reserved for snakes. They are loathed my many, and unjustly feared by some. In Maine, all nine species are harmless to people. There has only been one venomous snake that was native to Maine, the timber rattler, but that was last sighted over one hundred years ago in Maine. All snakes are predators, and they prey on worms, insects mice and other small prey. A snake's elongated body makes allows them to access areas such as tunnels, logs, rock walls and other structures that other predators can't access. Threats to snakes include roads and habitat loss, as well persecution. Snakes play an important ecological role as predators in the fields, forests and wetlands of Maine.
The snake poster feature's Maine's ten snakes, including the eastern racer, which is endangered in Maine, and the eastern ribbon snake, which is a species of special concern in Maine. The backside features biological summaries and interesting facts such as the fact that redbelly snakes are a gentle creature that won't bite when handled.
These three posters featuring Maine's amphibians, snakes and turtles are available through the Department of Inland Fisheries and Wildlife Information Center by calling 207-287-8000 or at the Department's website at