A Vernal Pond

     On the morning of March 8 of this year, after a day or two of warmth and rain, I visited a bottomland, deciduous woods among several wooded hills in southeastern Pennsylvania to listen for male wood frogs that should now be croaking to get mates for spawning masses of eggs in shallow pools in that woodland.  The weather was warm and sunny when I found an inches-deep pond in the woods where many male wood frogs were croaking hoarsely, as they would have during the last couple of rainy nights.  While the male woodies called amorously, I estimated 170 individual egg masses in three big rafts of egg masses floating on the water's surface.  There's about 50 eggs per individual mass and 170 masses for a total of at least 8500 wood frog eggs in that one pool.  And there are still more eggs to come, judging by the many pairs of woodies still spawning on the surface of the puddle.  Some of the copulating females leaped across mud or inch-deep water with their male partner hanging onto their backs.  I noticed, too, that woodies are dark like the forest floor they live in to be nearly invisible to would-be predators.
     I visited that pool in those bottomland woods for about two hours and the male wood frogs croaked most of that time.  Their calling is another sign of spring's arrival.  Explosive breeders, these wood frogs will spawn a few days, then retreat back to the dead-leaf-carpeted forest floor to spend the rest of the warmer months eating invertebrates.  And they spend winters dormant in those deep carpets of dead leaves on the ground until warm, March rains wake them again.   
     The vernal, woodland pond where I experienced many spawning wood frogs is about 40 yards long and 10 yards wide on average, and its bottom was covered with dead leaves from last year, foliage that true katydids didn't get to eat.  But those decaying leaves, and alga, will be food for developing wood frog tadpoles. 
     Certain plants in and around that vernal pond added to the beauty and interest of it, the frogs and their egg masses.  Skunk cabbage flower hoods and dead tussock grass emerged from the shallows.  Green moss covered small logs half submerged in the pool and the bases of red maple trees poking our of the muck and shallows like tiny islands.  And a little green grass decorated the pool's shores here and there.  Skunk cabbage leaves, tussock grass and the tadpoles will all grow together in this wooded swamp.
     However, the bottomland woods surrounding that puddle is still gray and brown, as it is in winter.  That woodland is dominated by red maple trees that do best in moist soil.  But white oaks, pin oaks, shag-bark hickories and swamp white oaks are in that woods as well.  They, too, are trees that do well in damp ground. 
     To hear croaking wood frogs, and the calls of other kinds of frogs and toads, is to step back many millions of years to the long-ago age of amphibians.  Their simple mating calls have not changed in all those many years. 
     There are many colonies of breeding wood frogs in the forests of the eastern half of Canada and the United States, but this one is the best I have experienced so far because the woods where it's located is large, and undisturbed by people, except occasional vehicles passing close by.
     Male woodies croaked almost incessantly and very excitedly from the moment I arrived at their vernal pond until I left it.  They only get one chance a year to reproduce.  Interestingly, they stopped vocalizing only when a vehicle drove by their spawning pool.  They seem very aware of happenings in their environment.  And I think the males listen to each other.  When one starts croaking after a period of silence, they all chime in as competitors to get mates.
     Every spring and into early summer, wood frog tadpoles in their shallow pools need to develop lungs and legs before those puddles dry up in the heat of summer.  Some years the tadpoles win and hop onto the forest floor as tiny frogs and some years they die in a stinking, black heap where the water had been.
     It takes effort to find wood frog spawning pools in deciduous woods in March.  And one must listen for them at the right time or those puddles of lively, noisy frogs will be missed altogether because wood frogs spawn in a few days and disappear back in woodland floor rugs of dead leaves until the next spring.  Woodies are obvious for a few days in spring and elusive the rest of the year, which is one of the reasons, I think, why they are so alluring to many outdoors people.