Before the rain finally and blessedly arrived, things were looking bleak in many of the vernal pools on the ridge. Last Sunday morning, after the overnight precipitation that had been predicted once again failed to materialize, I walked downhill from the house to the temporary pond complex that I monitor to see how parched things had gotten. A newly arrived Northern waterthrush, a sweet-voiced warbler that is often heard but seldom seen, was sounding confused. Instead of its usual and ringing jumble of notes, I swear it was singing something like â€śwhere the heck is the water?â€ť over and over again.
It is, of course, the nature of vernal pools to disappear, but in a typical year, the drying-out doesnâ€™t happen until early-to-mid-summer. A March-to-at-least-early-July hydroperiod is long enough to enable amphibians like wood frogs and spotted salamanders to go through the aquatic part of their life cycle: hatching from the egg masses that the adults had deposited around the beginning of spring and then growing large enough in the water to metamorphose into land dwellers before their nursery disappears in the summer heat. Itâ€™s a high-stakes race, but the weather usually cooperates and a new generation of amphibian teens emerges to continue the cycle.
This year has been anything but typical, and as the color on the US Drought Monitor chart changed weekly through April from yellowâ€”â€ťAbnormally dryâ€ťâ€”to light greenâ€”â€ťDroughtâ€“Moderateâ€ťâ€”to a kind of appropriately burnt orangeâ€”â€ťDroughtâ€“Severeâ€ťâ€”where it was on the 17th, I had a real fear that 2012 was shaping up to be a total wipeout for our local vernal-pool-dependent frogs and salamanders. Maybe the waterthrush should have been singing Jim Morrisonâ€™s â€śThe End.â€ť
That dirge was certainly appropriate for those amphibians that had dumped their eggs in a shallow stretch of water Iâ€™ve dubbed the â€śLoserâ€™s Pond.â€ť My pond complexâ€”vernal pool naturalists get very possessive about the temporary waters they have under observationâ€”is actually two separate ponds in a wooded area about the size of a football field. The Loserâ€™s area, a stretch about 20 yards long and 10 yards wide, got its name because itâ€™s very shallowâ€”no more than a foot deepâ€”and it often dries too quickly to enable even a wood frog to grow from egg to tadpole to forest-dwelling adult, a process that takes eight to twelve weeks. So, most years, itâ€™s a bad place in which to lay eggs. Still, more than a few wood frogs find it attractive. Perhaps theyâ€™re first-timers who are over-eager and just donâ€™t know any better; perhaps the more experienced wood frogs have claimed all the good breeding real-estate in the main pond and relegated the also-rans to this inferior nursery. I donâ€™t understand the reasonâ€”assuming wood frogs possess the ability to reasonâ€”and no one else Iâ€™ve asked over the years does either.
I guess when youâ€™re that pressed for time in the breeding sweepstakes, you take the first likely option. And then you donâ€™t look back.
Which, for any potential parents who left their eggs in the Loserâ€™s Pond, was a good thing in 2012. Last Sunday morning, this vernal pool had lost all its water and was nothing more than dry leaves and a fairly solid bottom. All of the wood frog tadpoles that had been swimming in the tea-colored pond were now ghosts.
Conditions were somewhat better in parts of the main pond. This vernal pool is actually a series of depressions that vary from a foot- to three-feet deep, but in times of normal rainfall, these are all connected in the early part of the breeding season. This allows tadpoles to move about freely in an area about double the size of the Loserâ€™s Pond.
But April was not normal, and so the tadpoles were stuck in whatever depression they happened find themselves when their moms had deposited her eggs. And by Earth Day, when I visited the pond complex, most of these now-isolated hollows were beginning to resemble shallow graves. Some of them held no more than an inch or two of water, and there, staying as close to the bottom as possible, were numerous black wood frog tadpoles. Occasionally, one of them would â€śbeachâ€ť itself like a wayward dolphin. Maybe it would wriggle back into the water; maybe it had just committed amphibian suicide.
Maybe it would attract the attention of a green frog, a predatory amphibian with an appetite for tadpoles of all species. If the drought continued much longer, the greenie, distinguished from another predator, the bullfrog, by the presence of two parallel ridges along its backâ€”the bullfrog lacks theseâ€”would soon have plenty of easy pickings, as the mini-pools shrunk and concentrated legions of tadpoles into ever-smaller spaces. At least the end might benefit someone: green frogs and bullfrogs, along with raccoons and that great blue heron Iâ€™ve seen frogging here from time to time.
I never did find out if that beached tadpole made it back to safety, and though amphibians most certainly lack a sense of irony, it would have been grimly ironic had that wood-frog-to-be given up its quest to become an adult. Early that afternoon, a genuine storm rolled up the coastâ€”the kind of norâ€™easter that the weird weather pattern had kept at bay all winterâ€”and paid us a very rainy visit. There was even heavy snow farther to our west, and when the deluge finally stopped on Monday afternoon, we registered five inches of rain in the ridge gauge. The pond was replenished. The wood frogs had been saved. The spotted salamander egg masses would hatch and, if we had more rain, the salamander larvae might make it to metamorphosis.
In the vernal pool world, we had come right down to the wire in the ongoing battle between life and death. This time, life won.
Well, mostly so. The Loserâ€™s Pond will not send forth a crop of amphibians this year. It will, alas, nurture a crop of mosquitoes. But we needed the rain, which will help fill my well, moisten my garden, and prevent a â€ślost generationâ€ť at our other vernal pools. Iâ€™d best give thanks and endure the bites. Sing a half-Hosanna. The waterthrush will, no doubt, join the chorus.