They may be called "spring" peepers, but those
from the southern United States can attest that these little amphibians
make their presence known far before its officially spring. While the vast majority of singing
in the North occurs from March to May or June, in Florida, choruses can
be heard in mid-winter.
Peepers actually awake from hibernation one to two months before they are publicly heard, creeping out from
their hibernation sites in the woodlands, under soil, logs, leaves, or bark, and migrating toward ponds and
flooded meadows to sing. They survive the cold of their "pre-season" by manufacturing glucose, which
limits dehydration, and acts as an antifreeze to prevent cell damage. When they first emerge, peepers generally
rely on stored fat for their main diet, but as the climate warms, they turn to their usual prey of
gnats, flies, ants, and mosquitoes. And by this time, they are beginning to make their presence known.
Males get dark brown or black throats, flecked with light yellow, and music fills the air...
Singing marks the official start of the mating season, which
researchers say is timed according to ambient temperature.
Singing is only performed by male peepers, and is accomplished by inflating a vocal sac, and passing air through it
to create the high pitched (about 3 kHz)
"pee-eep" sound. Singing is performed mainly to attract a mate. However, in the process,
it attracts competitors, which creates the chorus sound, described as sounding like jingle bells from far away, and
just downright deafening up close. The songs and competitive aspect have been studied in detail by Goin, who writes
that the chorus, from a frogs point of view, is not composed of a huge mass of individuals. Instead Goin suggests that the frogs
concentrate on groups of three, writing:
"One frog starts things off by sounding the note of A a number of times...If he is not answered, he pauses and gives
a little trill. Usually this stimulates another frog to respond with a G#, and the two call back and forth...
Now the last member of the trio chimes in with a B, and so they continue: A, G#, B; A, G#, B; A, G#, B.
A full chorus is made up of many of these tiny trios, each frog apparently ignoring all others save the two with which
it is singing."
Presumably the intent of all of this singing is to attract females, and it works. A female drawn to a particular male,
probably due to speedy repetition of calls, will swim over to him and make physical contact. The relatively smaller male then
hops on her back, and clasps her in the amplexus position, fertilizing her eggs. At least, that's the ideal situation.
In reality, things are not so easy.
Apparently, even recognizing one's own species is a challenge for these frogs.
In an experiment, female peepers were presented with two different speakers,
one emitting the call of a peeper, and the other of a sympatric species, Pseudacris ornata
. Tests showed that they were unable to discriminate between the two calls. On the male end,
competition is fierce. At the start
of the season there are an estimated nine males for every female at a particular breeding pond.
Studies show that males with the fastest call rate are considered most fit and are therefore the first to mate.
But there are other, less fit males who compete. Sometimes, smaller "satellite" males will lay in wait near a calling male,
staying low to the ground, with their heads down by their feet.
In many frog species, these satellite males intercept females whom the more "fit" male has attracted.
However, the role of satellite males is less intrusive in the spring peeper. Here, the satellite
males lay in wait until the more fit males leave to mate, then steal their territory and start
In the meantime, these little tree frogs are making a lot of noise, and that puts them
at serious risk. Natural predators of the spring peeper include ribbon snakes, water snakes, other frogs,
and aquatic insects, such as diving beetles (Dytiscidae) and water bugs like Lethocerus americanus.
Studies show that the frogs are particularly vulnerable during calling and amplexus.
If a pair successfully copulates, the female will lay about 800 to 1000 eggs either singly
or in small bunches on twigs, plant tems, leaf litter, or the bottom of a pond. Each egg is approximately
1-2mm in diameter, with yolks either pale grey or yellowish-gray in color.
Some populations are polymorphic for the two yolk colors.
The eggs hatch into tadpoles, which stay in their birth ponds until through metamorphosis.
Often times the tadpoles share a pond with another frog species, Pseudacris nigrita, but they
do not compete, because the peeper tadpoles feed on silt at the pond bottom, while the nigrita tadpoles
feed higher up in the water column. The tadpoles hit land as little froglets, 13-14mm long, travelling in waves
of individuals, all hunting for food before another hibernation.
Life expectancy is three years.
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