Following the Water (10 page)

I am familiar with the migrations of mayfly larvae making their way against the drift of water throughout the gradually sloping wetlands, where they are emblematic of my first followings of water in a new season. Ascending from this farther floodplain later in the season, these larvae are quite likely a different species from the one I am so familiar with—it is not easy to make a definite identification of any one species of the 676 known to inhabit North America. These larval insects move with a determination and intimation of destiny that would seem more the province of spawning salmon. Minute bits of driven life, a living seasonal tide that is timed to move against a temporal streaming of water, they press on, swimming with their characteristic undulations, ceaseless, untiring. They are one of the inexhaustible living energies powered by an exceedingly minimal energy base, in this case bits of algae and decaying leaves. They will not be deterred by surges or tumbles of water in the uneven terrain or by debris dams of twigs and sodden leaves. In some level terraces along the run there are pools
just deep and broad enough to harbor little green frogs and bullfrogs; they keep to outlying areas or headwaters in order to avoid larger members of their kind, who would make no distinction between them and anything else in their diet. How long is this column of larvae? It has lined the entire length of the draw along which I have walked, a distance of nearly half a mile. I did not join the procession at its beginning, but perhaps I can follow it to its end.

At length I do come to the end of my search, that is to say, to the beginning of the water. And here, too, the journey of the mayfly larvae has its end. The water's origin here is not a sphagnum-moss seep or rocky spring but a shallow shrub-swamp pool, thick with emergent winterberry. At times of abundant snowmelt or rain, groundwater wells to the surface at this interface, recharging a wetland basin high in the hills, filling it to the brim and over the brim, from which it flows on to follow the cut it has been carving in the landscape since the melting of the glaciers, down to the floodplain, for a final meander to join the river.

The pool teems with larvae. The air is filled with mayflies rising, pale-winged insects trailing long filaments, like tiny kites with three tails. I arrive at the site, and the moment, of a stunning transformation. As larvae continue to stream into the pool, subimagoes, as the mayflies transitional between larvae and adults are known, depart from it. They take to the air and fly short distances to alight on twigs and
branches, where they will wait one more day for their final transition. At its culmination they shed one last skin, this time with delicate wing coverings, to go forth as fully formed adults, or imagoes.

Following this, one act of life remains: mating. They will not be feeding; in fact, they have no mouth parts. The males, great numbers of them, will unite in a swarm, filling the air above the pool and beyond, to perform a dance that may not last a day. The males of each species choreograph a unique aerial ballet, a synchronization of vertical and horizontal movements, cued to a certain time of day. The females of their kind recognize the visual and temporal pattern and fly into the swarm, where they are quickly seized by males. Immediately after mating, the females descend to the water to lay their eggs. All, males and females alike, die following this coupling in the air. A life of perhaps a year (two or three years in some species) as egg and larva ends in as little as several hours or one day of adulthood. The temporality that marks their order has led scientists to name it Ephemeroptera. They have their "day of wings," one might say, as the term is derived from the Greek
ephemeros,
lasting a day, and
ptera,
wings.

I have seen the migrations of larvae and the winged dances of adults throughout my familiar wetlands over the course of many years, but I have never before witnessed this moment of metamorphosis. I look intently at the swimming
larvae and the subimagoes ascending from the dark surface. In a fraction of a second the split skin of a former life is left behind for that brief time in the air. I try to make out the actual dividing line, the instant of the aerial insect's emergence from the husk of the aquatic, gill-breathing larva. This is not the long-drawn-out, laborious work of a dragonfly extricating itself from the exoskeleton of a nymph. I follow some larvae as they rise to the surface and see them as they touch it, but I cannot see the actual departure: one moment there is a larva with its back just breaking the water, the next a mayfly in the air, with the shed skin floating below. Transformations, dividing lines—is there any greater metamorphosis, any narrower dividing line, than that of the invisible instant separating life and death?

Frogs are abundant and active throughout the pool, catching mayflies as they rise into the air or struggle upward through mazes of overhanging branches and sedges. A hermit thrush works the shoreline, snatching up larvae before they transform. This woodland bird becomes a wading bird, albeit in mere films of water. I have seen robins, red-winged blackbirds, and grackles, who know precisely the places and timings of these migrations, pursue larvae in this way each spring at the overflow of the vernal pool. Perhaps one thing that guides these long migrations is an adaptation to move to fishless waters for this elemental, vulnerable metamorphosis. But I see nothing that I could interpret as

Mayfly metamorphosis.

an effort to elude predators; nothing in this critical timing allows for delay or avoidance. It is not about the individual but about a species en masse, as one identity: numbers plotted against a common fate. In this communal going forth lies the persistence of an ancient order of life.

27
MAY.
A welcome new voice, one that I have been anticipating for some days now, breaks out as I wade the swale. After the first choruses of wood frogs and peep frogs herald spring's arrival, these loud trills of the gray treefrogs signal the season's steady progression toward summer. As is typical of their intermittent, infrequent daytime vocalizing, the treefrog chorus comes up all at once from hidden places in the emergent shrub borders and occasional islands of shrubs and saplings in this great, grassy vernal pool. It rings out for three or four minutes, then suddenly drops off to silence. I make one of my annual notations: "Hear first gray treefrogs."

Having no proper voice of my own to celebrate the seasons—I am as silent as the turtles in my wanderings—I am happy to have the calls of frogs, songs of birds, sounds of wind and water, to serve as my expressions. I love being silent as much as I love being in the silence, that is, of being where there is no human noise for some periods of time. (There is no lasting freedom from human sounds, but even a minute is sweet and healing.) Here are only the voices of nature and at times no sounds at all. In time another chorus erupts and rises up all at once, as though on cue from some conductor invisible to me but seen by dozens of frogs in their scattered hiding places. What baton is raised to set them all singing at the same instant? They fill the mild May afternoon with their vibrant trilling and then, as though the baton has been brought down, end their chorus as abruptly as they began it. This one communal voice of the many has always mystified me. Silence takes over again, above the still water lying beneath leisurely white drifts of cumulus clouds, soft in the sky with their blurred edges.

About to wade on, I hold still, arrested by a thought: "Hold on ... these frogs are here, all around me." Although by day they sound like—and evidently I have been content to regard them as—disembodied voices, spirits and sprites, phantoms of spring who come to life by night, the frogs do exist in the physical universe. There are no large trees with great cavities and sloughs of bark in this seasonally flooded
wetland; it doesn't seem possible that all of these frogs can be completely hidden from sight.

I have gone out to look for them by flashlight when they take up their all-night chorusing with resounding enthusiasm. Such searches in pitch-black darkness in the shrub swamps that these frogs favor for breeding have always been quite difficult. Some, such as rhodora, buttonbush, or blueberry swamps, are all but impenetrable and often complicated by treacherously deep, mucky, boglike substrates. At times I have had to suddenly grab hold of branches and stems to keep from going under in deep sinkholes. This is an alarming enough experience in broad daylight, let alone by night.

As is the case with spring peepers, it is nearly impossible to pick out the call of an individual treefrog from the deafening many, and all the more difficult to track the call to the frog who sings it out. Gray treefrogs are good ventriloquists, their loud trills seeming to come from anywhere and everywhere—everywhere but where they are. Encounters with them outside of their several-week-long breeding season, when they have departed from the wetlands and dispersed through the upland forests, are uncommon chance events. In boyhood, one of the rare places I could count on finding them away from their breeding pools was above the treetops, on a water tower I climbed, with barely suppressed terror, in games with friends.

As a consequence of my avid turtle focus, my eyes are virtually always on the water. I can miss an entire day's sky except for its reflections on the waters I wade. Now, with a new quest in mind I look upward. I let my eyesight ascend trunks and stems, then move along horizontal branches, trying to penetrate mazes of woody forkings and criss-crossings, layers and layers of leaves; my eyes become treefrogs looking for treefrogs. With nothing specific to go by, save that I do know what these frogs look like, I keep my head tilted to the canopy. I find it even more awkward to wade looking up than looking down. From all my years of looking for turtles, I have become something of a specialized animal, one with a neck permanently inclined to the water and ground at my feet.

Some friends who conduct fieldwork with birds once told me that they are often in wetlands and yet never see turtles. A group asked me to guide a tour and give them pointers on how to look for them. Lesson number one proved quite basic. After fifteen minutes or so I looked up to see them all with heads skyward, eyes affixed to binoculars. Those who observe birds are obviously accustomed to seeing what they seek considerably more frequently than those who look for turtles. "You won't find turtles in trees," I called out to them. But then, many of my bird sightings have come by way of a reflection on the water.

Head tilted up, I let my eyes do most of the moving; I
take a stride or two and scan my surroundings. This is how I look for turtles, but with my head inclined to the water or the earth rather than the canopy. And in considerably less time than is entailed in searching for something new to me, perhaps within seven minutes, I see a treefrog. Whether, as on some uncommon and fortuitous occasions, I find what I am seeking almost immediately, or whether it happens only after long searchings, sometimes over several seasons, there is something sudden and startling about finding the sought-after. The two-and-a-quarter-inch frog is settled into the narrow crotch of a nearly perpendicular forking upreach of winterberry holly, in a welter of vertical and horizontal branches. Mimicking the color and pattern of winterberry bark, he has become one with his embracing surroundings. He appears to have inflated himself somewhat in order to leave no froglike outline, to become an indistinguishable part of the whole. Loose folds of skin obscure what might be the revealing contour of a leg. In a group of animals known for their crypsis in color, pattern, and motionlessness, the gray treefrog is legendary. He doesn't move as I approach and look at him closely from different angles, even when I move some slender branches in order to get a photo of him.

With several strides and turnings of my head I see another. This is how it is: one must find a treefrog (or wood turtle or any of the other most hidden ones) before one can
find a treefrog. This one is on a dead branch arching from a dying elm sapling at the edge of the alder-winterberry border that rings the large, open central zone of reed canary grass and tussock sedge in this vernal pool, which is unusual in its wetland class for its size and its abundant and varied vegetation. Here the treefrog quite successfully passes himself off as one of the knobs and branch stubs of the stressed elm. I am reminded of musk turtles who mimic bumps on logs when they climb riverine deadfalls to bask; the head and legs hang down, pressed against the log, and the knoblike dome of the shell very closely approximates a branch stub.

My third frog is not so well hidden, perched on a horizontal stem of winterberry in a setting with a more open canopy, about four feet above my head. With his front legs tucked under his chin and his feet curled into fists, he looks down on me with the insouciance of the Cheshire cat. His bower is crowded with leaves, through which the strong sunlight passes, and he has taken on the green cast of his glowing ambiance. This chameleon-like adaptation produces at times rather green gray treefrogs. As I look up at him I am struck by the thought that these frogs have been watching me for years and also by the humbling realization that I, with my reputation for being an especially keen observer of nature, have been wading this seasonal wetland from thaw until it dries up in midsummer for three decades,
and it has not occurred to me until today to try for a daytime sighting of one of these tree-dwelling amphibians. From the angle of one's eyes to the focus of one's mind, one can never have enough ways of seeing. And no matter how hard we look, however much we see, there is inevitably much that goes unseen.