Spring's Frog Chorus
by Nicholas Kokales
(Conservation Currents, Northern Virginia Soil and Water Conservation District, April 2006)
It's Spring! Let the Chorusing Begin!
Ah spring, the time of year when our minds turn to thoughts of fancy. It’s no different in the frog and toad world. Frogs and toads, collectively called anurans, belong to the class of animals known as amphibians. Like many amphibians, anurans start life in water. They hatch from eggs deposited in water and have an aquatic larval stage (tadpole). As they develop, they morph into land-dwelling creatures.
Each year, anurans return to the water to breed, in some cases traveling to their natal pool. Timing of the annual trek depends on temperature, and varies by species. For instance, in Northern Virginia, wood frogs (Rana sylvatica) usually arrive at their breeding pools by early February, whereas green frogs (Rana clamitans) may not arrive at their breeding sites until late May.
Male anurans arrive at the water first and use sound to attract females. Each species has a unique call. The spring peeper’s call (Pseudacris crucifer) is a high pitched whistle. In contrast, the pickerel frog’s call (Rana palustris) is a low snore. The sound of many anurans calling simultaneously is referred to as a chorus.
Location, location, location! Often cited as the “three” most important factors in real estate, location is an important factor in anuran breeding as well. Wood frogs breed in temporary bodies of water known as vernal pools. These temporary pools lack fish populations that could eat the wood frog larvae. Bull frogs (Rana catesbeiana) prefer permanent bodies of water, because their larvae can take two years to morph. American toads (Bufo americanus) employ the “any port in a storm” strategy and simply use the closest waterbody to breed, be it a pond or a small ditch.
Although mating habits vary among species, for all frogs and toads spring is the season. Their throaty voices are nature’s springtime chorus, telling us spring has sprung. Are you listening?
Illustration courtesy of David Jenne.