Teeming Life in a Drying Pool

As summer’s rising temperatures and humidity oblige us to slow our pace, we still languish in the heat. Many creatures react in a similar manner: squirrels stretch their bodies along a tree branch or open platform of leaves to nap during the hottest part of the day; birds and their nestlings pant openmouthed to dissipate body heat; and terrestrial salamanders move deeper underground to find and retain necessary moisture. And a woodland vernal pool, though thankfully shaded by forest trees, appears lifeless.

sp-salamander-metLong gone is the March madness that brought a frenzy of amphibians to court and mate in the pool. This frenzy gave way to the early spring egg laying by wood frogs and spotted salamanders, who left the pond for the upland forests once their mission was completed. Their gelatinous, tennis ball-sized egg masses have since produced zillions of tadpoles and salamander larvae, and all evidence of the egg masses themselves have disappeared -recycled into the vernal pool web of life. And now this vernal pool, this temporary body of water, is drying up. A border of darker leaves rings the pool where the water has receded. Soon the only evidence of this wetland habitat, so vital to so many creatures’ lifecycles, will be a dark, smudged depression on the forest floor.

In the meantime, this seemingly lifeless pool is still teeming with creatures in a race against the clock. Though the wood frog tadpoles have most likely transformed into tiny froglets and have left their aquatic nursery by now, the spotted salamander larvae are still growing and developing.

These little aquatic carnivores are voracious hunters, filling their bellies with anything that moves: tiny copepods and daphnia, fly and midge larvae, small worms, and yes, mosquito larvae. In crowded conditions they are also known to nip one another’s tails.

Only one-half inch long at hatching, a spotted salamander larva will grow to two to three inches in length by the time it is ready to leave the pool. Its muddy brown coloration will darken to a gray-black with flecks or small spots of yellow. Over time the large, upward-sweeping external gills that give it the appearance of an underwater lion, will be absorbed into its body and the transforming salamander will need to rise to the surface to breathe air. A newly emerged juvenile salamander will hang around the edges of its natal pool for a while, hiding under leaf litter or woody debris before moving into the forest uplands.

It is said that as a vernal pool dries the salamander larva’s development quickens. But in drought years it may not be quick enough; entire larval populations can succumb to extremely dry conditions in a given year. The good news is that the adult spotted salamanders are long-lived creatures that can survive for a decade or more. As long as their forest habitat is protected and they can cross our roadways unscathed during their breeding migration, they will be back to fill the vernal pool with their offspring the following year.

Submitted by Cindi Kobak

Photo by Cindi Kobak