Listening for Spring’s Arrival
by Kathy Reshetiloff
I know that spring has truly sprung the first time I hear spring peepers (Hyla crucifer crucifer). This tiny tree frog’s song, which sounds like the jingle of sleigh bells, signals the sure, though perhaps slow, end to winter.
Like other frogs, male peepers sing to attract females. The mating call can sometimes be heard up to a half-mile away. It’s hard to imagine that these teeny frogs, only three-quarters of an inch to an inch and a half long, can sing so loud.
All frogs croak ribbit and sing by moving air back and forth over their vocal cords, making them vibrate. But spring peepers also have very large vocal sacs under their chins that inflate with air. As they peep, they release the air and their songs resonate. Peeping reaches crescendo on a warm night and almost ceases if temperature drops below 30 degrees.
Most of the year, peepers live in the trees. Adhesive disks on their toes make peepers expert climbers. In winter, they hibernate under leaves, logs and bark. The water in their little bodies freezes. But high levels of glucose work as a kind of anti-freeze, protecting vital organs from crystallizing. Peepers simply thaw out in the spring.
Warming temperatures and early spring rains lure peepers to the moist forest floor where they begin their serenades. When ready, female peepers arrive and choose their mates.
The male sits on the female’s back and fertilizes the 800 to 1,300 eggs she deposits. Each egg, only 1/200th of an inch long, is laid singly on underwater plants. A pair may spend an entire day at this before returning to the trees.
In two to three weeks, the eggs hatch and tiny tadpoles, less than one-fifth of an inch long, emerge. They feed by inhaling water and filtering out blue-green algae. One ounce of tadpoles can clean 12 gallons of water every day.
In five months, tadpoles metamorphose into the adult form. Gills are replaced with lungs, legs grow and tails are reabsorbed into the body. The new tiny frogs leave the water for their woodland habitat.
I can’t imagine a spring without peepers serenading me, but their continued presence is not guaranteed. Spring peepers, like all frogs as well as toads, salamanders and other amphibians, breed in the wetlands where they were born. If these natal areas are disturbed or lost, the amphibians will not breed.
Why should we care? Amphibians help us measure the health of the environment. They exchange water and air primarily through their skin and often absorb pollutants that are in the soil and water. Like a canary in a coal mine, a decline in local populations may indicate a contaminant problem in the environment.
Without these peepers, too, we’d lose a sure sign of spring’s imminence.
Conservationist Kathy Reshetiloff, who works for the Chesapeake Bay office of the U.S. Fish and Wildlife Service, has heard peepers twice so far this spring. Her last story for Bay Weekly was about how birds stay warm in winter.