From
Budgeteer News
By late April, the snow melts and rains have provided us
with numerous small ponds. These vernal pools serve as the
breeding sites and temporary homes of a few species of frogs.
Since some of these ponds will dry up in summer, this whole
process must be quick.
Early spring frogs begin mating calls almost as soon as
they wake from hibernation. Frogs spend the Northland winter
either in the mud under the pond or buried under leaves
on land. Regardless of their sleeping site, the calling
and mating takes place in the water of these ponds.
Three species in our region lay eggs in late April. This
trio of spring peeper, wood frog and chorus frog now sing
on these spring nights unless the cold silences them. Males
of each kind make unique sounds that both attract the attention
of females and warn other males to stay away from this male’s
chosen location, its territory.
Egg masses produced by these frogs are usually clear jelly
substances surrounding black dots. The eggs must be kept
moist, and if water conditions are right, the black dots
quickly form into long embryos that resemble the tadpoles
that they are soon to become. Within a week, these early
frog eggs hatch and the tiny tadpoles settle into a life
of eating algae and rapidly growing. By midsummer they will
have already metamorphosed into adult frogs and leave the
ponds for a terrestrial existence. Each of these three frogs
that breed early and fast are more at home on land than
in water. Except for coming to ponds to lay eggs, they are
rarely seen in water. Even their hibernating takes place
on land.
Tadpoles changing to frogs is a phenomenon that we have
all known about for years. But it is quite a change. The
critter goes from an aquatic form with no legs to a terrestrial
one with strong hopping appendages. They go from a gilled
animal to one with lungs. And they switch diets (including
the whole digestive system) from algae eating to an insect-eating
predator.
This water-land existence begins now in late April in the
vernal ponds and matures in mid-July. Countless thousands
of eggs and tadpoles begin, but only one or two percent
of these will reach adulthood. Predators and weather conditions
vastly cut down the numbers.
On these spring nights, we may be able to hear the sharp
and penetrating peeping call of the spring peepers. Or maybe
we’ll hear the clucking calls of the wood frogs. Creaking
chorus frog calls have been compared to the sound of running
our thumb over the teeth of a comb. Frogs seldom call in
the cool of the early mornings, but often by late afternoon
they commence singing and continue until several hours after
dusk. Despite the chilly temperatures, ice and snow of late
winter, the frogs are now beginning a new breeding season
in the Northland in late April.
Larry Weber is author of the “Backyard Almanac”
and “Butterflies of the Northwoods.” He lives
in Carlton County and teaches natural science at Duluth’s
Marshall School.
