National Geographic: Rain Forest

---

Millions of years ago,

before man, before the ice ages,

when the world was warm and humid,

forests like these covered

much of the earth.

And it was here,

rough eons of geological time,

that a profusion of life evolved.

The remnants of

those primordial jungles

are the rain forests of today.

They are home to half of

all the animal species on earth.

Yet, in the shady depths

of the forest,

there is seldom more than a

fleeting glimpse of this abundance.

When they are seen,

the animals are often revealed

as strange

and splendid examples of

natural perfection and adaptation.

Myriad in their diversity

and sometimes bizarre in form,

these creatures give

the somber forest

a special mystery and splendor.

Endless rains and high temperatures

create the steamy atmosphere

in which rain forests thrive.

These conditions occur now only in

a narrow belt around the equator

where forests blanket some

three million square miles

of the earth's tropics.

Within this belt

lies the small Central American

country of Costa Rica,

which possesses one of the richest

natural endowments on earth.

When Christopher Columbus landed

here in 1502,

he found a mountainous land

of rivers

and forests like those he'd seen

ten years earlier in Hispaniola.

Then, in what is perhaps the first

description ever of a rain forest,

Columbus wrote:

"Its lands... are most beautiful...

and filled with trees of

a thousand kinds and tall,

and they seem to touch the sky;

and I am told that

they never lose their foliage,

as I can understand,

for I saw them as green

and as lovely as they are

in Spain in May..."

But it was partly from

the early explorers

that some popular misconceptions

arose.

For many, the first glimpse

of a rain forest

was from the rivers

that flowed through them.

The forests seemed impenetrable-

a tangled mass of undergrowth

through

which a man could only hack

a path with difficulty.

But in reality,

the dim interior is more open

and usually easy to move about in.

Little light penetrates

the dense canopy

and so undergrowth is sparse.

Only a thin layer of leaves

covers the ground.

A coral snake searches

for a place to drink

and finds enough rainwater

in a curled leaf.

The bright bands of color warn

predators that it's poisonous.

Below this thin layer of leaves

lies the forest soil and a paradox.

For the luxuriant vegetation

of a rain forest

is often based

on impoverished soil.

The explanation lies in the way

the forest recycles its nutrients.

Dead trees and fallen leaves rot

quickly,

and their nutrients are rapidly

reabsorbed by fungi

and tiny roots near the surface.

The entire system is so efficient

that little is lost,

and fully 95 percent

of the rain forest's nutrients

are held in the living vegetation,

hardly any in the soil.

To shed its old skin,

the coral snake rubs its body

against rough surfaces

in the leaf litter.

A male poison-arrow frog is

courting a female.

With his monotonous song,

he will try to entice her

to follow him under a leaf

where they'll mate.

The male leads the way.

She follows. Within the shelter

of a curled leaf,

she'll lay her eggs,

and the male will fertilize them.

She has produced five eggs

in a cluster of jelly

and will stay nearby

until they're ready to hatch.

Workers from a colony

of leaf-cutting ants

are harvesting leaves to

take back to their nests.

With their scissor like jaws,

they easily cut the leaves

to manageable size.

But some skill is needed

for the next stage

when the leaf is hoisted into

position for the journey ahead.

For some, the problem may be

too much help

for others, just a sudden puff of wind.

But they're the exceptions.

For most ants,

it's only the first step

in the long trek back to the nest,

which may be 100 yards or more away.

They follow a chemical trail

laid down by the workers

that first scouted this tree,

so they seldom go astray.

The leaf fragments that

they carry are not for eating.

Instead, they are employed

by the ants

in a remarkable system of farming.

The leaves are used to

culture the fungus

that is the only food source

for the ants and their brood.

Here in the underground garden,

the leaves are cut into much

smaller pieces and carefully cleaned

probably to remove any spores

that might contaminate

the pure culture.

The leaf edges are chewed

to a wet pulp,

and a clear droplet of body fluid

is added to create

the perfect foundation

for the precious fungus

that sustains the colony.

This is not the work

of leaf-cutter ants.

The insects that create these

patterns

are seldom seen during the day.

In daylight, insects are

more vulnerable to predators,

so many feed only at night,

leaving their mark everywhere

in the understory of the forest.

But some insects are active by day,

and this morpho butterfly is

a brilliant target for a jacamar.

Before it can be swallowed,

the wings must be removed.

Great agility and keen eyesight

make this anole

lizard a formidable predator

on small insects.

Nearby, a female is shedding.

Her old skin is too nutritious

to be wasted;

she eats every bit of it.

The female is in his territory

and by staying,

she shows that she is willing

to be courted.

He displays to her by flashing

his brilliant dewlap.

A performance like this is both

a signal to the female

and proclaims his territory.

The female will remain here now,

and they'll mate frequently

over the next few days.

Its body blending perfectly

with the leaves,

a praying mantis settles

in a patch of sunlight

created by a fallen tree.

When a great tree falls,

a gap is created in the forest

canopy.

It is in these sunny spaces

that the forest regenerates itself.

The seedlings of most forest trees

cannot survive in shade;

to flourish, they need light.

So the competition for space

around a fallen tree is intense.

And for every sapling,

there is a clinging vine competing

for a place in the sun.

But in this gap,

there's a tree that always has

clear growing space around it.

This species of swollen-thorn acacia

has evolved a remarkable system

of defense.

For as soon as a sapling

or vine touches it,

ants that live on the acacia

attack the intruder.

They cross onto the touching vine

and cut through its leaf stems.

In a short time, their work is done,

and the vine will lose its leaves,

wither, and die.

Most forest trees have evolved

poisonous chemicals

in their leaves to stop insects

from eating them.

But the acacia is edible,

and would soon be destroyed

were it not for the vigilance

of the ants.

Any insect that lands on this acacia

soon learns its error-for the

ants bite and sting viciously.

In return for their protection,

the tree completely supports

the ants.

It secretes for them

a sugar-rich solution,

which they drink from little

nectarines between the leaves.

On the tips of some leaves

in each acacia,

unique structures are grown

especially for the ants.

Rate this script:0.0 / 0 votes