Tripping Over Toads
I started reading about frogs and toads early one
February, wanting to be prepared for their calls on damp spring nights
when they sing to the raindrops. Frogs and toads (and the salamanders I wrote
about earlier) are amphibians,
close relatives of the first vertebrates to make their way out of the
water about 350 million years ago. Although some amphibians would
later evolve into reptiles that could leave their ocean heritage behind in
the egg, amphibians never quite made that final evolutionary
leap. Instead, frogs and toads migrate to lakes, ponds, rivers,
and puddles every spring to lay their eggs. Their offspring hatch
into swimming larvae --- tadpoles --- and then eventually crawl out of
the water, recreating that long ago journey of discovering life above
the surface.
Fifty degrees
is the magical temperature that tempts the earliest frogs and toads out
of hibernation, but only if the night is wet as well as warm. On
the evening of February 26, the first rainfall came, and I grabbed a
flashlight to search for frogs. Sure enough, Northern Spring
Peepers had begun to call from the shallow vegetation along the water's
edge, hesitant at first but turning into a chorus as the rain thundered
down. Soon, the chuckle of a Wood Frog joined them from a nearby
puddle, and by March, toads had begun to trill in puddles. All of
these singers were males, each one intent upon attracting a mate and
passing on his genes.
In daylight, I
could see egg masses left behind from the night's orgy. Peeper
eggs are laid singly in the vegetation and are invisible to my eyes,
but Wood Frog eggs expand into bulbous masses and toad eggs are laid in
long strings, winding back and forth through the shallow water.
Each transparent egg is speckled with a tiny black embryo of the
growing tadpole within.
As I scouted
nursery puddles one chilly morning, I discovered a mating pair of Wood
Frogs. I cracked the thin ice above them with my fist and pulled
the pair out, an easy feat since their metabolism was slowed by the
frigid water. To my surprise, the male showed no signs of
loosening his stranglehold, with one foreleg wrapped around the
female’s neck and the other just behind one of her front legs.
After a moment, I lowered them back into the water and the female swam
quickly away to bury herself into the mud on the pond bottom, leaving
the male exposed above her except for a cap of mud on his head.
He would cling to her for hours until she was ready to lay her eggs,
then would release his sperm above them, fertilizing the eggs as they
were laid. The mass of eggs would expand as the water soaked into
each clear capsule, growing from small enough to fit in the female’s
body to the six inch masses now dotting the puddles around me.
Spring advanced
and more species began to call. One day, while making my rounds,
I noticed the first toad eggs hatching, tiny black tadpoles valiantly
struggling free of the encircling membrane, then lying stunned on the
puddle bottom to recover their strength. By the time the
summer-loving Green Frogs and Pickerel Frogs began to mate, the puddles
were beginning to dry up and the Wood Frog tadpoles were quickly
growing legs to escape to the land.
Every year
since, I've listened for the first spring frogs, and sought out their
eggs in nearby puddles. As the year progresses, more species will
join the mating dance, until only the peepers are left still singing as
summer turns to fall.
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