Here’s a little tale about
ants, elephants and a tree that whistles which has rather large implications.
The tree is
Acacia drepanolobium, commonly known as a
whistling thorn
for reasons which will become clear in a moment. It’s native to East
Africa, grows to around six metres tall and has the usual pairs of
mean-looking thorns on its branches.
Ordinarily, thorns don’t deter elephants. They can turn woodland into
grass savanna in remarkably short time and have the ecological delicacy
of bulldozers. But they mostly avoid the whistling thorns like poison
chalices.
The reason is that these trees have bulbous spheres at the base of
their thorns and dispense sugary nectar from the ends of their leaves.
The result is food and housing for several species of stinging ant with
Latin names far longer than themselves.
Some of these bore holes in the spheres, chuck out the contents and
settle in. When the wind blows across the entrances, the spheres whistle
like flutes. If an unwary animal attempts to browse off a whistling
thorn, the ants attack with singular ferocity.
There’s an inverse proportion between an elephant’s size and strength
and the sensitivity of the inside of its trunk. Once bitten, as they
say, twice shy. The same browsing sensitivity goes for giraffes and
other herbivores.
To test whether the ants were deterring elephants, University of
Florida biologist Todd Palmer and University of Wyoming ecologist Jacob
Goheen fed some young orphaned Kenyan elephants branches from whistling
thorn trees, as well as from another acacia. When there were no ants on
the branches, the elephants were just as likely to eat whistling thorn
as they were their usual tree food. But when the branches held ants, the
elephants avoided both types of acacia.
The mutualistic relationship, however, is more complex than just
housing ants. If the whistling thorn could be said to have a preference,
it would be for the
Crematogaster nigriceps ant. And if the
nigriceps
could be said to have a plan, it would (and does) allow occasional
herbivore browsing. This is because a bit of plucking stimulates leaf
growth, which increases the supply of nectar.
However, if one of the other acacia ant species such as
C. sjostedti
takes over a tree, the insects’ preference isn’t for the bulbs but
holes drilled by stem-boring long-horned beetles. In ways not yet
understood, this ant species attracts the beetles, which eventually
weaken a tree and can kill it. To prevent this, if a tree leans out too
far in the direction of another, the
nigriceps prune the twigs so there’s no contact, avoiding a possible invasion.
Too greater variation in the balance between tree, ant and elephant would cause hardship for all three.
There’s no need to remind you that, while an elephant’s brain is
larger than ours, a tree doesn’t have one and an ant’s is smaller than
the point of a pin. We’re talking about something other than
intelligence here and a synecdoche of a story about deep time.
Every second of every minute of every hour of every day, year,
decade, millennium, million and even billions of years, the relationship
between every insect, animal, bird, fish, plant, mountain, continent,
planet, star and galaxy is in an exquisite ongoing dance of this and
every moment of time.
Life on our blue planet is a never-ending story so big, so small, so
destructive and constructive, so beautiful and profound that, like the
blind men trying to describe an elephant by touching parts of it, we can
hardly see it at all.
And the hardest of all is to understand the outrageously vast time it
takes for an ant, a tree and an elephant to learn to dance together in
mutual harmony on the African savanna.
By:
Don Pinnock
http://blog.getaway.co.za/wildlife/animal-stories/ant-elephant-tree-whistles/
