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Reproduction: A Courting To Nature
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REPRODUCTION: A-Courting to Nature! LIFE SCIENCES SIG
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For some time she had watched his movements, appearing coyly in his
haunts. And now, had it paid off? Doubtless, he was in love. His muscles
were taut; he swooped through the air more like an eagle than a Greylag
gander. The only problem was, it was not for her that he then landed in
a flurry of quacks and wingbeats, or for her that he dashed off surprise
attacks on his fellows. It was, rather, for another - for her preening
rival across the Bavarian lake.
Poor goose. Will she mate with the gander of her dreams? Or will she
trail him for years, laying infertile egg clutches as proof of her
faithfulness? Either outcome is possible in an animal world marked daily
by scenes of courtship, spurning and love triumphant. And take note: these
are not the imaginings of some Disney screen-16 writer. Decades ago Konrad
Lorenz, a famed Austrian naturalist, made detailed studies of Greylags and
afterwards showed no hesitation in using words like love, grief and even
embarrassment to describe the behavior of these large, social birds.
At the same time he did not forget that all romance - animal and human - is
tied intimately to natural selection. Natural selection brought on the
evolution of males and females during prehistoric epochs when environmental
change was making life difficult for single-sex species such as bacteria
and algae. Generally, these reproduced by splitting into identical copies
of themselves. New generations were thus no better than old ones at
surviving in an altered world. With the emergence of the sexes, however,
youngsters acquired the qualities of two parents. This meant that they
were different from both - different and perhaps better at coping with
tough problems of survival. At the same time, nature had to furnish a new
set of instincts which would make "parents" out of such unreflective
entities as mollusks and jellyfish..
The peacock's splendid feathers, the firefly's flash, the humpback whale's
resounding bellow - all are means these animals have evolved to obey
nature's command: "Find a mate. Transmit your characteristics through
time!" But while most males would accept indiscriminate mating, females
generally have more on their minds.
In most species, after all, they take on reproduction's hardest chores such
as carrying young, incubating eggs and tending newborns. Often they can
produce only a few young in a lifetime. (Given half a chance, most males
would spawn thousands.) So it's no surprising that the ladies are choosy.
They want to match their characteristics with those of a successful mate.
He may flap his wings or join a hockey team, but somehow he must show that
his offspring will not likely be last to eat or first in predatory jaws.
Strolling through the Australian underbrush that morning, she had seen
nothing that might catch a female bowerbird's eye. True, several males
along the way had built avenue bowers - twin rows of twigs lined up north
and south. True, they had decorated their constructions with plant juices
and charcoal. Yet they displayed nothing out front! Not a beetle's wing.
Not a piece of flower. Then she saw him. He stood before the largest bower
and in his mouth held a most beautiful object. It was a powder blue
cigarette package, and beneath it there glinted a pair of pilfered car keys.
Without hesitation she hopped forward to watch his ritual dance.
Males have found many ways to prove their worth. Some, like bowerbirds,
flaunt possessions and territory, defending these aggressively against the
intrusion of fellow males. Others, like many birds and meat-eating mammals,
pantomime nest building or otherwise demonstrate their capacity as dads.
Still others, however, do nothing. Gentlemen may bring flowers, but most
male fish just fertilize an egg pile some unknown female has left in
underwater sand. For a fish, survival itself is a romantic feat. For other
species, though, love demands supreme sacrifices.
Shortly after alighting on the back of his mate, the male praying mantis
probably had no idea what was in store. This would have been a good thing
too, because as he continued to fertilize his partner's eggs, she twisted
slowly around and bit off his head. She continued to put away his body
parts until well nourished and thus more able to sustain her developing
young.
Luckily for most species, the urge to mate come on only occasionally,
usually in springtime. For love can hurt, particularly if you intended has
difficulty telling a mate from a meal. Pity the poor male of the spider
species, Xysticus Cristatus, for instance. His only hope of survival is to
tie a much larger female to the ground with silk thread, and keep her there.
Every time a moth releases its attracting scent, or a bullfrog sings out
its mating call, these animals are risking a blind date with some predator.
Such alluring traits have long puzzled scientists, particularly those which
seem not only risky but useless as well. Why, after all, should a frigate
bird mate more if he puffs out an extra large red throat sac? How does
ownership of such a thing indicate a superior individual? Until recently,
the question stymied biologists, but then researchers in the U.S. and
Sweden announced a possible answer. While studying widowbirds, among whom
extravagant tail feathers are hip, they discovered that the longest-tailed
males also carried a lower number of blood parasites. Sexual ornamentation
seemed to be a means by which males could show of superfluous health and
energy.
All of which may bring us to fast sports cars, flashy clothes and other
accessories of the human suitor. After all, if he can afford dinner at the
city's most expensive restaurant, chances are he could finance a baby too.
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