Throughout the Northeast, spring rains are creating temporary pools of water in woodlands and meadows known as vernal pools. Vernal pools, though often small and inconspicuous, come alive as frogs, toads, salamanders, and other amphibians converge on them to breed.
Vernal pools provide just the right environment to support both the eggs and larvae of amphibians. Because vernal pools are isolated from other water sources, they do not support fish that would prey upon amphibian eggs and larvae.
Amphibians spend part of their lives living in water and the other part living on land. Most amphibians lay soft eggs in water. An egg hatches into an aquatic larval stage which looks and acts quite differently from the more terrestrial adult stage. For instance, toad and frog eggs hatch into tadpoles, which can only survive in water. As the larvae grow, they experience radical physical changes and are transformed into adults in a process known as metamorphosis.
Some salamanders, like the marbled salamander (Amystoma opacum), deposit eggs in the fall and the larvae overwinter in the dry pool. Other salamanders, like the spotted salamander (Amystoma maculatum) seen on the right, will wait until spring to lay their eggs.
Unlike quiet salamanders, toads and frogs congregate at vernal pools and call to attract mates. Frogs produce their calls by moving air back and forth over their vocal cords causing them to vibrate and produce sounds. So although you may not see them, you can identify species by listening to their calls.
Wood frogs (Rana sylvatica) migrate to vernal pools early in the spring-often before the winter snow and ice have completely melted. The call of the wood frog is a hoarse clacking sound, like a quack. Click on the photo (right) to hear a wood frog.
Spring peepers (Hyla crucifer), a tree frog, follow the wood frogs by a week or two. From February to March, spring peepers leave the trees to mate in open water. Click on the photo (left) to hear their unmistakable mating call, the peep, which can be heard up to a half a mile away.
The American toad (Bufo americanus) can be found almost anywhere there are moist places, plenty of insects to eat and shallow waters to breed. Breeding from March to July, their mating call is a pleasant musical trill.
All across the world, amphibian populations are declining due to, among other things, loss of habitat. Many amphibians return to breed at the same ponds and wetlands where they were born. If natal areas are disturbed or lost, those amphibians will not breed. Deforestation reduces woodlands needed by adults.
Why should we care? Amphibians help us to measure the health of the environment. Because they exchange water and air primarily through their skin, amphibians also absorb pollutants that are in the soil and water. Like a canary in a coal mine, a decline in local populations may indicate a widespread problem.
Protecting forested wetlands and woodlands is a step to preserving amphibians. Vegetated buffer strips along waterways are equally important. People also benefit from such actions. These same areas are also habitat for a multitude of wildlife including invertebrates, fish, birds, and mammals. The forests and wetlands offer us such a retreat, to enjoy the serenades from the woods.
You can help scientists monitor amphibians in your area:
North American Monitoring Program www.pwrc.usgs.gov/naamp
National Wildlife Federation Frogwatch Program www.nwf.org/frogwatchusa
All photos U.S. Fish & Wildlife Service