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April 2, 2014: The Sounds of Spring Peepers & Wood Frogs
Through the winter, woodlands and meadows are mostly quiet at night. But with the arrival of spring rains and warming temperatures, that silence is broken by loud choruses of wood frogs and spring peepers. These are the first frog species to come out of hibernation and begin the year’s amphibian breeding season.
Spring peepers are small, just one inch in length, but you wouldn’t know it from their sound. Each peeper can produce a call as loud as 90 decibels. Multiply that by the number of frogs in a wetland habitat, and you have a sound that can rival that of a rock concert.
Why so noisy? That’s how the male spring peepers attract females from the surrounding woodlands. As the females come out of hibernation, they are carrying between 200 and 1,000 eggs, and the females are outnumbered by the males at about 9 to 1. Competition is intense, and females choose males based on the quality of his song.
Because of this competition, males wrestle for the best spots at the chorusing site. Interestingly, Dr. Don Forester and David Lykens of Towson University discovered that some spring peeper males were successful in breeding with females through a very deceptive strategy. Because calling requires a huge amount of energy, some spring peeper males, known as satellite males, don’t call at all.
Instead, these satellite males save energy by positioning themselves near the top singers. They then intercept females moving toward the calling males. Satellite males are smaller than calling males and would probably be at a disadvantage in trying to attract females with a less impressive voice.
Though the spring peeper is often considered the first frog to emerge from hibernation and therefore an early sign that winter is indeed over, the wood frog is usually ahead of the peeper. In fact, in mild winters, wood frogs have been observed arriving in woodland pools as early as February.
Wood frogs are often referred to as “explosive breeders” because they arrive in large numbers and have a short breeding season, usually only lasting the first few weeks of late winter or early spring. Wood frogs almost exclusively lay their eggs in vernal pools, which are small temporary bodies of water that form in depressions.
Because these pools dry over the summer, wood frogs must lay their eggs, the eggs must hatch, and tadpoles must fully develop and metamorphose before the pools dry. The wood frog’s strategy is to arrive first and maximize the time needed to make it the entire way through the process. Wood frog tadpoles often dine on the newly laid eggs of later arriving frog species.
Even as these frogs perpetuate their life cycle, they do face challenges. Their well-being is intricately linked to the survival of their woodland home and their vernal pools. Be considerate of these habitats in your neighborhood by preventing trash and other pollution from traveling through your waterways. Slow down while driving on warm spring nights, allowing amphibians to migrate safely across roadways. And when you pay these amazing creatures a visit in their natural habitat, observe but don’t disturb.
Want to buff up a bit more on your amphibian knowledge? Check out our latest infographic on all things frog!