|
by Nicholas Kokales
(Conservation Currents,
Northern Virginia Soil and Water Conservation District, April
2006)
 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.
|
