Planet Earth (2006) s01e08 Episode Script

1
This is our planet's hothouse.
The jungle.
The tropical rainforest.
Forests like these occupy only
3% of the land,
yet they're home to over half
of the world's species.
But how do so many different
kinds of plants and animals
find the space here to live
alongside one another?
On the dark, humid forest floor
the jungle appears to be lifeless.
Often, the only signs of life
are what you hear.
A male blue bird of paradise
is advertising for a mate.
It's quite a performance,
but he's not the only bird of paradise
here keen to make an impression.
There are nearly 40 different kinds
on the island of New Guinea,
each with a display seemingly
more bizarre than the rest.
A riflebird of paradise.
Like many jungle animals, birds of paradise
avoid competing with each other
and these do so by living in different
parts of this jungle covered island.
The six plumed bird of paradise displays
in his special clearing on the forest floor.
The magnificent bird of paradise
favors the low branches of bushes.
His female is modestly dressed.
The male has a good set of lungs,
but he'll have to do more than flutter
his eyelids, if he wants to impress her.
It'll all depend on his performance.
The females may be dull looking,
but they're very picky
and it's time
for a really close inspection.
His right side looks fine
but what about his left?
Pretty impressive,
but is he magnificent enough?
Oh dear. Her departure says it all.
Generations of choosy females
have driven the evolution
of these remarkable displays.
The more extravagant a male is,
the more likely he'll be noticed.
New Guinea lies in a warm tropical belt
that girdles our planet around the equator.
With abundant rainfall
and 12 hours of daylight,
365 days a year, it's here
that rainforests flourish.
Surprisingly, only 2% of the sunlight
filters down to the forest floor.
Down here,
seedlings struggle to grow,
but the gloom is not eternal.
The death of a forest giant
is always saddening,
but it has to happen
if the forest is to remain healthy.
The sudden blaze of sunlight
will bring life to the forest floor.
A single hectare of rainforest may
contain as many as 250 species of tree.
That's nearly 10 times the number
that grow in Britain
and the thirst for light triggers
a race for a place in the sun.
There's no time to waste.
A seed that may have fallen only a few days
ago, now bursts through the leaf litter.
With so many competitors,
getting a good start is critical,
but each plant has
it's own particular strategy
for making the most
of this rare opportunity.
The seeds of hardwoods
are quick to germinate
but, like the fabled tortoise, their
strategy is to be slow and steady.
Vines and other climbers put all their energy
into rapid vertical growth, rather than girth,
though they'll need
to be well supported.
The climbers' strategy looks chaotic,
but there's method in their madness.
Their growing tips
circle like lassoes,
searching out anchors
for their spindly stems.
They put coils in their tendrils,
so that if their support moves,
they will stretch and not snap.
But the frontrunners at this stage,
the first to fill the clearing,
are pioneers like the macarangas.
Their immense leaves capture huge amounts
of sunlight, so fueling their growth.
As a result, the macarangas grow
a remarkable 8 meters a year,
surging ahead of almost
all their rivals.
In the race for the top spot,
hundreds will start,
yet few will ever reach
the finishing line,
their growth cut short
by the diminishing light.
In less than 4 years,
the gap will have gone,
but that's not the end of the race.
The ultimate winners are the tortoises,
the slow and steady hardwoods.
When the short-lived pioneers
have fallen,
it's the hardwoods that take their place,
and a 50 meter giant, like this one,
may keep it's place in the sun
for another 200 years.
At the top, is the canopy,
the engine room of the jungle.
It's up here that most of the animal
life in the rainforest can be found.
But despite the apparent abundance of
vegetable food, gathering it is seldom easy.
With no real seasons,
each tree flowers or fruits
at a different time of the year,
which means that food
is very widely spaced.
Monkeys, like these tamarinds, must search
the canopy for all kinds of food
if they're to survive.
But across the world's rainforests,
there's one type of fruiting tree
that always delivers — the fig.
Wherever they grow, figs are a magnet
for a great diversity of animals.
In the Amazon, the first to appear
are the spider monkeys.
These large primates
are big fig eaters,
but they won't have the tree
to themselves for long.
Others will want a share
like the diminutive emperor tamarinds.
The tamarinds love figs too, but being
petite means they're easily scared off.
Squirrel monkeys are also small,
but they have strength in numbers.
Their timeshare on the tree may be short,
so their tactics are more smash and grab.
Capuchin monkeys are the bully boys
in these forests,
and they want the ripe figs
for themselves.
Figs are one of the few trees
that fruit the year round,
so when other food is scarce, these fruits
are always available somewhere or other.
Even for leaf eaters, like howler monkeys,
the ripe figs are just too good to miss.
And howlers are too big
for the capuchins to chase off.
Figs are so popular, that as many as 44
different kinds of bird and monkey
have been seen working
a shift system on a single tree.
Because fruiting trees are so valuable,
many monkeys are territorial.
And if you live in the treetops,
there's perhaps no better way of staking
your claim to a territory, than this.
The calls of the siamang gibbons
begin as a duet
between the dominant male and female.
The rest of their families soon join in,
and it results in a frenzy of activity.
The calls can carry over a mile,
and their message is clear.
They tell any neighboring siamangs
this is our territory. Keep out.
Up here the calls of siamang gibbons
seem to dominate the airwaves,
but with the jungle's
incredible diversity,
there are countless others
trying to be heard too.
Every layer seems to beat
to a different tune.
In the early morning the forest's
chorus is particularly rich.
Sounds travel further in the cooler air,
but few calls can penetrate as far through
the dense vegetation as this one —
the deep bass solo of a male orangutan.
In the middle of the day,
little stirs in the jungle
and the hot dense air
muffles the sound.
As the afternoon wears on, a different
set of players begin to warm up.
Insects work in harmony, timing their calls
to fall between the notes of others.
Many singers
stick to precise schedules
and right on cue the six o'clock cicada.
Night brings out a whole new orchestra.
The cacophony of competing calls
seems deafening to us,
but frogs ears are tuned to hear
only the calls of their own kind —
the songs of courtship echo
from all around.
Male gliding leaf frogs
leap from the treetops.
To slow their descent, they use their
huge webbed feet as parachutes.
These large tree frogs spend most of
their lives in the high canopy
and only come down
when it's time to breed.
Once settled, they begin to
serenade their unseen females.
Now it's time for the females
to make their move.
There's no shortage of suitors, but this
female has already made her choice.
She's heading towards the loudest call,
because loud calls come from big frogs,
and big is best, but to reach him,
she must run the gauntlet
of a gang of smaller suitors.
Their only chance of mating
is to make a sneaky interception.
He's scored.
But with more females
arriving all the time,
it's not over until the
fat frog stops singing.
Feet, so vital for gliding,
are now put to other uses.
Two's company, three's inconvenient,
but in any case, all male frogs
are equipped with dry thumbs
which enable them to get a vice-like
grip on their moist partners.
It's a case of first come,
first served.
Living in such a humid environment,
means jungle frogs are less
tied to puddles and pools,
and these even lay their eggs
out of water.
There's little chance of them drying out,
and up here they're safer from predators.
Surprisingly, it doesn't rain every day
in the rainforest,
but more still falls here
than anywhere else on Earth.
On average, over 2 meters a year.
A single tree can suck up
hundreds of tons of water each year.
But the trees
can't use all this water,
so much of it returns to the air
as vapor, forming mist and clouds.
In the Amazon, the largest unbroken
stretch of rainforest in the world,
half of all the rainwater that falls,
comes from clouds produced
by the trees themselves.
With so much rain, it's not surprising
that many of the worlds largest rivers
are found in rainforests.
Inside the forest,
the high humidity
creates the perfect conditions
for a strange world,
where life is built on decay.
Amoeba like slime molds cruise the surface,
feeding on bacteria and rotting vegetation.
Fungi also flourish on decay.
These are the fruiting bodies of the
fungi, the only visible sign
of a vast underground network
of fungal filaments.
In temperate forests, the buildup of leaf
litter creates rich stores of nutrients.
That however, doesn't happen here.
Nutrients that reach the soil
are leeched out by the rain,
but fungi are connected to tree roots
by their underground filaments.
And by quickly consuming the dead,
they help to recycle crucial minerals
straight back into the trees.
And this recycling happens faster here,
than anywhere else on the planet.
There are thought to be nearly a million
different types of fungi in the tropics,
the vast majority
still unknown to science.
But one thing's for certain:
without fungi,
rainforests could not exist.
Nothing goes to waste in the rainforest.
The fungi become food for others
like these beetle larvae.
Finding the fungus isn't a
problem for the grubs
since their caring parents
actually show them the way.
Incredibly, 80% of all insects
live in jungles,
fewer more successful than the ants.
There can be 8 million individuals
in a single hectare,
but jungle ants
don't have it all their own way.
These bullet ants are showing
some worrying symptoms.
Spores from a parasitic fungus
called cordyceps
have infiltrated
their bodies and their minds.
It's infected brain
directs this ant upwards,
then, utterly disorientated,
it grips a stem with it's mandibles.
Those afflicted, that are
discovered by the workers
are quickly taken away and dumped
far away from the colony.
It seems extreme,
but this is the reason why.
Like something
out of science fiction,
the fruiting body of the cordyceps
erupts from the ant's head.
It can take 3 weeks to grow,
and when finished, the deadly
spores will burst from it's tip,
then, any ant in the vicinity
will be in serious risk of death.
The fungus is so virulent, it can
wipe out whole colonies of ants,
and it's not just ants
that fall victim to this killer.
There are literally thousands of
different types of cordyceps fungi,
and remarkably, each specializes
on just one species.
But these attacks do have a positive
effect on the jungle's diversity,
since parasites like these stop any one
group of animal getting the upper hand.
The more numerous a species becomes,
the more likely it'll be attacked
by it's nemesis —
a cordyceps fungus.
With so much competition, jungles
have become the home of the specialist.
Now this animal, in the island of
Borneo, is one of the most unusual.
It's a colugo, or flying lemur, though
this is something of a misnomer
as it doesn't actually fly,
and it certainly isn't a lemur,
in fact nobody's quite sure
who it's closest relative is.
The colugo depends
on a diet of young leaves,
and to find enough of them,
it must move from tree to tree.
The leaves are not very nutritious, but then,
getting around doesn't use much energy.
In a single night, a colugo might
have to travel as far as 2 miles,
but that task is made easier
by it's superior gliding skills.
The secret of success in the
competitive jungle is specializing,
and this has led to the evolution of
some very intimate relationships
between plants and animals.
These are pitcher plants
also from Borneo.
Adapted to living
in very low nutrient soils,
the pitcher plant gets most of it's nourishment
from insects lured to nectar glands
on the underside of the lids.
Once onboard, the waxy sides of the pitcher
ensure there's little chance of escape.
Most slip to a watery grave.
At the bottom of the pitcher,
glands secrete enzymes,
which help to digest the corpses,
so feeding the plant.
But not all visitors have a fatal
attraction to the pitchers.
The red crab spider spends it's entire life in
the pitchers, hanging on with threads of silk.
Instead of building a web, it relies on
the water filled pitcher to trap it's food.
When an ant falls in, the spider
simply waits for it to drown
and then abseils down
for a spot of fishing.
Alive, this ant would be far too
dangerous for the spider to tackle,
so, using the pitchers as traps,
means it can get bigger meals
and the spider doesn't rob
the pitcher of everything.
The digested remains of it's booty
will end up in the water,
providing instant food for the plant.
Other food, like mosquito larvae,
seems to be out of reach,
but the spider
has another surprising trick.
By taking it's own air supply
trapped in a bubble,
the crab spider can actually dive
to the very bottom of the pitcher.
Once the prey is captured, the spider hauls
itself back up it's silken safety line.
The pitcher is a one stop shop
for this spider, but it's not alone.
In the jungle, there's
competition for everything,
even a small water filled pitcher plant.
Such specialists create
the jungle's remarkable diversity,
but finding enough food to survive
is so challenging
that most animals living here
tend to be small,
though there are exceptions.
This is the Congo in Africa.
It's a vast wilderness and the
least explored of all jungles.
From up here, the forest looks
similar to the ones
that grow in the Amazon
or Southeast Asia,
but down below,
there are some unexpected sights.
Crisscrossing this forest,
are countless miles of highways,
and they were made by something big.
Forest elephants roam great distances
in their search for food,
but to survive, they must emerge
from the gloom of the forest.
And clearings like this one, are a
magnet for elephants from far and wide.
These elephants live in much smaller
groups than their savanna cousins.
This might be the first time that one
group will have seen another for a month.
For the adult males it's a welcome break
in an otherwise largely solitary existence,
and they're not the only animals
attracted to the clearing.
Forest buffaloes and red river hogs
are also regular visitors,
as are bongos, which are very difficult
to see outside these clearings.
All these large forest animals
have come here
to collect an essential
element of their diet
that lies buried beneath the mud.
And the elephant's trunk
is the perfect tool for reaching it.
To get what they seek,
the prospecting elephants must first
blow away the covering layer of silt.
Satisfaction at last.
They're collecting
a particular kind of clay
that contains vital minerals
scarce in their natural diet.
It may be mud, but there's just nothing
quite like it for enriching the blood.
The clay also helps
to absorb the toxins
found in many leaves
that the elephants eat.
There are other benefits to coming here.
These clearings are the only places
where the forest elephants
can get together in such numbers.
When they return to the forest,
they will have to go their
separate ways once more.
If large animals are rare in jungles,
then groups of large animals actually
living together, are even rarer.
This posse of hunters is not only
formidable, it's also very large.
In their search for food,
chimpanzees move effortlessly
between the forest floor
and the canopy.
They're one of the few
jungle animals able to do so.
Figs are a vital part
of a chimpanzee's diet,
and some just can't seem
to get enough of them.
But there's something special about
this stretch of forest in Uganda.
Fruit is actually abundant.
And a lot of food
supports lots of chimps.
At a 150 strong,
this community of chimps
is the biggest yet found in Africa.
Their numbers are so large, that they
need a big territory, lots of fig trees,
and they're willing to fight for it.
These calls announce the start of a raid
into land controlled by their neighbors.
As they leave their core zone, the patrol
goes silent, occasionally stopping to listen.
Signs of the enemy are detected
and examined closely.
The chimp militia are now
at the very edge of their territory.
All need to be on maximum alert.
Then it's wait and listen.
An unfamiliar chimp call
raises the tension.
It's an uncertain time. The size
of the rival group is as yet unknown.
Not far away the neighbors
are feeding in a fig tree,
oblivious to the approaching dangers.
The patrol moves off
with a sense of purpose.
They must remain silent
until they close in on their rivals.
The attack is on.
To intimidate their opponents,
the aggressors scream
and drum on buttress roots.
Several males corner an enemy female.
It's a ferocious attack, and she's
lucky to escape with her life.
Others are not so fortunate.
The battle won,
a grizzly scene unfolds.
An enemy youngster
has been caught and killed.
The carcass is shared between
members of the group, and eaten.
Killing a competitor makes sense if
you want to protect your food supply,
but exactly why they cannibalize the
dead chimp, is not fully understood.
It may simply be a chance
for some extra protein.
Teamwork has brought this
group of chimps great success,
but they'll soon reach
the limits of their power.
The competition for resources ensures
that no one species dominates the jungle.
The rainforest's great diversity
has come at a cost.
It has made them the most finely
balanced ecosystems in the world,
only too easily upset and destroyed
by that other great ape —
the chimpanzee's closest relative —
Ourselves.