Vernal Pools

(This column first appeared in the April 24, 2000 Buffalo News.)

    As ephemeral as those early flowers that grace our woodlands are our vernal pools. Full of life for a few brief weeks each spring, they disappear by midsummer, their waters evaporated, the rich life they briefly supported long gone.

    A vernal pool has the following characteristics. Physically it is contained in a basin depression lacking a permanent above ground outlet. Its water derives from snow melt or spring runoff and at some time of the year it usually dries up. Our extraordinarily mild winter almost left us with no vernal pools this spring, but those recent rains we have been complaining about have come to their rescue.

    A vernal pool also has a biological character. Most important, because of this periodic drying, it contains no fish. It must, however, support several species that would have been immediately gobbled up by any fish population: fairy shrimp, wood frogs, and one or more of our regional species of mole salamanders.

    Fairy shrimp are strange little crustaceans that look like -- and very well may be -- vestiges of the Triassic Age. About an inch in length, they swim about on their backs by waving caterpillar-like appendages and steering with their feathery tail. They are semi-transparent -- you can observe their body functions. Most noticeable are their outsized yellow and black staring eyes.

    Fairy shrimp feed on small bits of plant and animal matter and are, of course, themselves fed upon by virtually everything else. Their place is at the bottom of the animal food pyramid but their unusual mating habits make them survivors. Their eggs remain dormant in the ground clutter when the pools dry up and only open when water returns. They will even hatch after several years of drought-induced quiescence.

    The wood frog is my favorite amphibian. A small brown frog about 2 1/2 inches long, it is easily identified by its black mask. You must listen carefully to make out their soft quacking calls that are unlike those of any other frog.

    Although wood frogs define vernal pools, they are not the only anurians that briefly inhabit these temporal ponds. The more strident comb-ticking calls of chorus flogs come together to create an almost alarm clock pulsating sound that often overwhelms the wood frogs' soft gurgles and the simple bleeps of another tiny frog, the spring peeper.

    Mole salamanders are aptly named for their lives are mostly spent underground in the burrows of mice and moles. Our most common species is the spotted salamander, 5 to 7 inches in length, easily identified by its many bright yellow (or sometimes orange) spots on a dark body. Less common is the blue-spotted salamander, smaller at 4 to 5 inches and black with small blue flecks. (In this region its range overlaps and it hybridizes with the Jefferson salamander, a more southern species that occurs in brown or gray forms.)

    All of these frogs and salamanders breed at this time of year, producing gelatinous egg masses that will soon give us a new generation of their kind. Before the vernal pools dry up their offspring will have retreated to their woodland homes.

    Unfortunately vernal pools are almost as threatened as the species they harbor. They are drained to create farmland or housing subdivisions. They are polluted by salt runoff from roads and by pesticides spread to kill mosquitoes that also inhabit them. In the process the amphibians that feed on mosquito larvae are eliminated, exacerbating rather than solving the problem.

    So important are these pools that several programs to identify and protect them have been mounted in Massachusetts. Conservationists here might well consider similar activities.-- Gerry Rising