SCRIPPS NEWS (Washington, DC) 13 April 07 Vernal pools attract mating creatures and nurseries (Ken Weber)
The top of a hill seems a strange place for a pond, for a place where frogs and turtles and salamanders congregate in early spring. But hundreds of amphibians and reptiles gather there each year, almost as soon as the ice is gone. This is their most important time, a breeding season.
Frequently, the little wood frogs are first to arrive at the pond, heading for the still-chilled water just as soon as they awake from hibernation in the woods. Once they reach the water, the frogs start advertising for mates, crying out with calls that sound like ducks quacking. Smaller frogs called spring peepers use the water, too, as do a variety of salamanders and turtles, dragonflies and damselflies, and numerous other creatures.
Maybe describing that place as a pond is being too generous; it's just a shallow depression among the rocks and trees and bushes on a rather high hill. It fills with water each spring when snow melts. Sometimes, water remains through the year; sometimes, the pond goes dry in summer. Biologists would call it a vernal pool, meaning that it holds water in spring. Whether it dries up later is not as important. Spring is when it serves a critical purpose. Not only do frogs and the other little critters go there for breeding, but such pools serve as egg incubators and nurseries.
There are hundreds, perhaps thousands, of vernal pools across the country. They might not look like much to casual observers _ just overgrown puddles in the woods _ but without them, the populations of frogs and turtles and salamanders would plummet. They need these pools, and, whether we realize it or not, we need the little creatures.
Forget for the moment the frogs' links in the predator-prey chain, and all the good they do in helping control insects; they fill a vital role each spring just by reawakening the countryside, and our own senses, with their courtship calls. The bizarre clacking of wood frogs and the high-pitched chants of spring peepers are as much a part of the music of spring as the melodies of songbirds. And just as welcome. It's not until we hear the first frogs that we realize how quiet winter was, and how long winter lasted.
My favorite vernal pool is still that one on the hill. There are half a dozen other pools within walking distance of my house, but I keep making the long climb up the rocky hill, year after year. That pond is larger than most seasonal pools, and possibly more active. It has good sitting rocks, too; I can plop down on a boulder at the water's edge and let the frogs do their thing almost at my feet.
Most of my climbs are on sunny afternoons, when I'm looking for wood frogs. In ideal conditions _ warm sunshine helps _ more than 100 frogs are likely to be in view at a time. Last spring, my high count was 125 frogs, some floating on the surface, some charging about, some gripping potential partners, some diving, some resurfacing. There might have been more than 125; with all the movement it's hard to make accurate counts.
Spring peepers are harder to see, and they are more vocal in the evening, so other trips are necessary after sunset. Then, with a flashlight, it's usually possible to pick out the tiny frogs clinging to weeds and belting out their calls, which they create by inflating and deflating throat sacs. Think of frogs blowing huge bubblegum bubbles; that's what spring peepers resemble when they are calling.
But each spring I have to remind myself all over again just how small the peepers are. They are no larger than my thumb to the first knuckle, so it takes intense concentration to see them, despite the ringing chants. A flashlight beam helps considerably in focusing on small areas at a time. Unlike wood frogs, which call from the water itself, the peepers always climb onto weeds or branches to proclaim their availability.
Salamanders are silent in their courtships, except for the splashing they can do when most stimulated. That pool usually attracts the big spotted salamanders _ lizard-shaped creatures with garish yellow spots _ and they can churn up the water when a dozen of them get tangled in a tumultuous, whirling frenzy. Salamanders are most active during night rains, so, to see the shows, it is necessary to go out there in rain. Lying face-down on a boulder, in pounding rain, while shining a light into water, might not seem like a great way to spend a spring evening, but when the salamanders are going full-speed, it is a memorable experience. Uncomfortable perhaps, but memorable.
Turtles require less effort. There are not a great many turtles in that pool but occasionally I find interesting species. Last spring, on the day I counted 125 wood frogs, I started looking for frog eggs and found spotted turtles. Wood frogs attach their eggs to underwater objects, such as branches, so I peered into bushes looking for the egg masses. Down there, clutching branches at water level, were two turtles with yellow dots on their shells. Spotted turtles are relatively rare; those two seemed like bonuses, more benefits of a vernal pool.
Vernal pools attract mating creatures and nurseries