All language subtitles for National.Geographic.100.Years.Vol03.Rain.Forest.eng

== ��Ļ�������Զ������� ==
����Ļ����ѧϰ�������Ͻ�������ҵ;��

Millions of years ago,

before man, before the ice ages,

when the world was warm and humid,

forests like these covered
ch 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:

"Lts 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 scissorlike 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
nectaries between the leaves.

On the tips of some leaves
in each acacia,

unique structures are grown
especially for the ants.

They are rich in protein
and vitamins,

and are taken by the ants
to feed their larvae.

It's here within the large hollow
thorns of the acacia

that the ants rear their brood.

Some of these larvae will mature
into fertile adults with wings,

and fly away to start
another colony in a seedling tree.

These young basilisk lizards forage
along the river's edge.

They live in the territory
of this adult male

who tolerates them
and probably fathered them.

But he allows no other adult male
to intrude here.

This female is exclusively his.

Flowers are attractive
to the leaf-cutters as well,

and many end up
in the fungus gardens.

Spider monkeys move
as easily through the canopy

as the puma through
the forest's understory.

Towering 100 feet above
the forest floor,

the canopy harbors more
tree-dwelling creatures

than any other habitat on earth.

The treetops mingle and interlock
to create a self-contained world;

many of its inhabitants never leave
its sunny spaces to venture below.

A three-toed sloth feeds
in the hot sun,

while a mother carries her baby

into the cool shade
within the canopy.

A"lie-in-wait" lizard remains
perfectly motionless.

It's a strategy that serves it well:
By keeping still,

the lizard is overlooked
by both predator and prey.

And an unsuspecting victim
can be pounced on from above.

Rain forests seldom get less than
100 inches of rain in a year.

Some even exceed 400 inches.

And so, most of the leaves
in the humid understory

of the forest are specially
adapted to drain water

from their surface as quickly
as possible.

If water stays on them,

the leaves may rot or become host
to tiny plants that may do damage.

These drip tips ensure that
the leaves will dry quickly.

The forest floor can usually
absorb rain as it falls.

But when the rains are
particularly heavy,

the forest becomes saturated

and the water runs off to flood
the surrounding rivers

flushing fallen trees
and debris out to sea.

A tide line of rotting vegetation
is left on the beach,

and a shy agouti forages
among it for fruits.

These paper wasps are drying
their nest.

Constructed of wood pulp,

it would soon soak up the rain

if the wasps didn't drink the water
and spit it over the edge.

The adults take so much care
and trouble,

because in each of the cells is
a developing wasp,

and their entire brood could be
destroyed by a heavy downpour.

As each larva grows,

the wasps enlarge its cell
by adding another layer

of pulp and saliva
to the outside rim.

And when the nest begins to warm
in the sun,

they cool their brood
by rapidly vibrating

their wings to create a current
of air.

The eggs of a poison-arrow frog
have hatched,

and the female carries two tiny
tadpoles on her back.

While they are developing into
frogs,

they have to be in water.

She takes them up a tree to a site

she has chosen in
a bromeliad plant.

She will deposit them in rainwater
held in the bromeliad.

She makes her way down a leaf
to a small pool at its base.

And here, she submerges her tadpoles

until they release their grip
and leave her back.

The tadpoles will complete their
development in this tiny pool.

In six to eight,
weeks they'll emerge as frogs

and return to the forest floor.

Army ants are on the move.

They build no permanent nests and

constantly comb the forest
for their prey.

This species preys only
on the larvae of social insects

and here they attack a nest
of paper wasps.

There is nothing the wasps can do.

They abandon their brood
to the voracious horde,

which will soon strip the nest
of all life.

They take their plunder
to a bivouac

on the underside of a fallen log.

Here, by linking special hooks
at the ends of their legs,

they form long, hanging chains.

Through sheer numbers,

these strands mesh together to
from the living fabric of the nest.

Within the nest,
strands of workers interlock

to create chambers for
the queen and brood.

At night, the forest teems
with a different life.

It's now that most of
the leaf-eating insects emerge.

To survive the ravages of insects,

most plants have evolved toxic
compounds that protect their leaves.

But insects in turn have developed
immunity to the chemicals.

So together they have evolved,
insect and plant,

until now most insects have become
such specialized feeders

that they can only eat the leaves
of one particular plant,

or only one family of plants.

This harlequin beetle spends
most of its life

as a larva concealed
within dead wood.

But now as an adult,
it emerges to find a mate.

The beetle is host to
a resident colony of mites

that finds refuge in the creases
and folds of its back.

Also riding on the beetle

are pseudoscorpions that prey
on the mites.

Help in the prowerful job

the creases is no chance
in the Chigao seem see

A stick spider suspends itself
head down

above a leaf on which its prey
might walk.

Its web is held by the tips
of its four front legs.

Green leaf-frogs gather near
a forest pool to mate.

The males wait near the water

to intercept the females
as they arrive.

Clasping the much larger female,

the male will stay with her now
until she has laid her eggs.

She selects a leaf directly
above the water,

and as she lays her eggs,
the male fertilizes them.

The cat-eyed snake isn't
interested in the frogs.

He is after their eggs.

And as egg-laying has been going
on for several days,

he will easily find others.

Many snakes are attracted
to the pool

when the leaf-frogs are laying.

They eat almost all the eggs.

Glass frogs also lay their eggs
above water,

in this case a stream,

and the male remains
close to the eggs

until they're ready to hatch.

His presence probably deters flies

and other insects
that would harm them.

On a rainy night about two weeks
after the eggs are laid,

the vigil of the male ends

when the emerging tadpoles drop
into the stream below.

But the frogs do not always manage

to lay their eggs directly
above the water.

However, the tadpoles are specially
equipped with reflexes

that help them cope
with this situation.

The first rays of sun
warm the forest

and a mist rises up
the great mountain mass

that divides Costa Rica,

separating the forests of
the Atlantic coast

from those of the Pacific.

High in these mountains,

the forest receives moisture

from direct contact with the clouds,

and the vegetation changes
imperceptibly.

Many of the creatures found here

can live only at these
cooler heights.

And it's here at the very top
of the mountain

that a rare mating ritual occurs.

It takes place only during
the few days of the year

when contact of cloud
and forest is at its greatest

when enough water has collected to
form the few small pools

in which golden toads lay their eggs.

These toads occupy an area
of mountaintop

no greater than one square mile.

They have been found nowhere else
on earth.

The golden males gather
at these pools

and fight for possession of
one of the drab females.

Once firmly established on her back,

a male is usually secure
in his conquest

and can easily repel
any further challenge.

Long strings of eggs are laid in
the tiny pool,

and if the misty weather persists
long enough to maintain the pool,

another generation of golden toads
will be produced.

Bellbirds announce their territories

from the tops of the tallest trees.

A pair of Resplendent Quetzals are
digging out a nest in a dead tree.

The males are considered

the most beautiful birds
in the Western Hemisphere.

The ancient Mayas and
Aztecs so revered

the quetzal that only royalty
and nobility

were allowed to wear
the magnificent feathers

in their ceremonial costumes.

To kill the bird was a crime;

they were simply caught

and released after their long
plumes had been plucked.

But the forests are going.

At the present rate of destruction,

most countries will lose their
rain forests within our lifetime.

And with the forests will go
hundreds of thousands of unique

and irreplaceable life forms
that can survive nowhere else.

Many will become extinct even

before they have been described
by science.

Their importance to
nature's balance

and their possible contribution

to human welfare will never
be known.

But at last,

some countries are beginning
to realize that

rain forests justify their
existence simply by being there.

And tiny Costa Rica, by its example,

has become a world leader
in conservation.

One quarter of its land is given
some measure of protection,

and a full eight percent

is permanently protected
in national parks.

If other nations will follow
Costa Rica's example,

there is hope.

But it is a race against time,

because in the hour it has taken
to view this film,

some 3,000 acres of the world's
rain forest have been destroyed.