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Partners
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| September 23, 2002. |
One of our strange traits is the
number of partnerships we have struck up with other
animals. The dog, which is now such a part of our lives,
was domesticated from the wolf between 12,000 and 15,000
years ago as an aid to a hunting way of life. Cats were
tolerated as mousers in the early granaries before they
took on an additional role as companion animals.
In some cases the association grew
naturally into a stronger relationship, but often there
was a deliberate attempt to control and breed the animals
concerned. The end result is that both ourselves and
our partners have become some of the most numerous animals
on the planet.
Personal hygiene is so important
in the ocean that coral reefs have areas set aside as
beauty parlors for fish. Here a barbershop of attendants,
known as cleaner fish and cleaner shrimp, line up to
tend visiting fish. The cleaners are recognized by their
brightly striped uniform; sometimes the stripes are
blue and white, but, appropriately, the cleaners often
sport the familiar red-and-white trademark of a barber's
pole.
The barbers bob and fuss in front
of their customers to signal their willingness to attend.
The visitors ask for service by suspending themselves
in the water, either head down or head up, and opening
their gills and mouth. The cleaner shrimp and cleaner
fish then go to work. They tidy up their client by trimming
off any loose skin and snipping away at fungal growths
with their mouths. They also remove any fish lice infesting
the skin.
The cleaners will boldly enter the
gaping mouth of even a huge grouper but the grateful
customer never snaps its mouth shut at the wrong moment.
Not all the attendants are to be trusted, however. Some
fish wear the uniform of a cleaner but have a very different
code of practice. Instead of gently removing skin flakes
and other debris, the saber-toothed blenny dives at
its teeth, like a cutthroat barber wielding a razor
blade.
In the gardens of almost every home,
herds of miniature domesticated animals are reared an
milked for food. Usually we fail to notice this pastoral
scene, as the farmers concerned are ants and their flocks
are greenfly. As these aphids suck up sap from our prize
roses, they store a sugary treat for the ants. The ants
milk the aphids for this "honeydew" by stroking
them with their antennae. The ants even defend their
herds against ladybirds and lacewings, like herdsmen
protecting their livestock from wolves. If the aphids
are in danger of overgrazing, the ants move them to
new pastures. The ants that tend the bean aphid even
overwinter their herds in underground stalls, a form
of transhumance like that practiced by cattlemen in
the Swiss Alps.
The partnership between ants and
aphids is mutually beneficial and complex. Like many
partnerships, it probably began by accident. There are
present-day examples that show how such relationships
may begin.
In Texas, screech owls prey on snakes
and bring them back to the nest to feed to their hungry
chicks. Sometimes the owls catch a small burrowing snake
known as a blind snake. Because it has slippery skin,
the blind snake often escapes before disappearing down
a chick's gullet. As it burrows into the debris of the
nest, the snake finds a ready supply of maggots and
nest parasites. Gaining free board and lodging, the
blind snake inadvertently becomes a pest controller
and helps keep down the number of parasites. The relationship
is almost certainly accidental but both parties benefit.
In Africa many local tribes have
established an astonishing relationship with a bird
known as the greater honey guide. In an incredible feat
of memory, this bird makes reconnaissance flights over
an area as big as 100 square miles and memorizes the
location of every bees' nest within it. Then it looks
for a person to open one of them.
As soon as the honey guide hears
human voices, it flies towards them. Perching in a nearby
tree, it uses a persistent, double-pitched call to attract
attention. Then, flitting from branch to branch, it
waits for a reaction. A human honey-gatherer knows the
correct response is to move towards the bird. The bird
replies by flying away, using a conspicuous, undulating
flight. In dense scrub it quickly disappears, but it
is rarely gone for long - it is simply checking the
position of the nearest bees' nest before flying back
to the gatherers. If they are still following, the bird
flies off again in the direction of the nest. This to-ing
and fro-ing may continue for several miles until the
men are drawn close to the nest. The honey guide then
perches nearby and emits a softer, less persistent call
to signal the end of the journey. The birds wait patiently
until the men have broken into the nest and gathered
the honey. The men leave a thank-you gift of grub-filled
honeycomb as a reward.
cupul@pvmirror.com
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