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This is our planet's hothouse,
the jungle, the tropical rainforest.

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Forests like these occupy only 3% of the land

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yet they're home
to over half of the world's species.

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But how do so many different kinds
of plants and animals

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find the space here to live alongside one another?

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On the dark, humid forest floor,
the jungle appears to be lifeless.

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Often, the only signs of life are what you hear.

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A male Blue Bird of Paradise
is advertising for a mate.

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It's quite a performance.

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But he's not the only bird of paradise here
keen to make an impression.

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There are nearly 40 different kinds
on the island of New Guinea,

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each with a display
seemingly more bizarre than the rest.

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A Rifle Bird of Paradise.

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Like many jungle animals, birds of paradise
avoid competing with each other.

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And these do so by living in different parts
of this jungle-covered island.

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The Six-Plumed Bird of Paradise
displays in his special clearing on the forest floor.

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The Magnificent Bird of Paradise
favours the low branches of bushes.

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His female is modestly dressed.

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The male has a good set of lungs,

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but he'll have to do more than flutter his eyelids
if he wants to impress her.

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It'll all depend on his performance.

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The females may be dull-looking
but they're very picky.

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And it's time for a really close inspection.

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His right side looks fine, but what about his left?

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Pretty impressive, but is he magnificent enough?

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Oh, dear! Her departure says it all.

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Generations of choosy females have driven
the evolution of these remarkable displays.

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The more extravagant a male is,
the more likely he will be noticed.

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New Guinea lies in a warm tropical belt
that girdles our planet around the equator.

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With abundant rainfall
and 12 hours of daylight 365 days a year,

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it's here that rainforests flourish.

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Surprisingly, only 2% of the sunlight
filters down to the forest floor.

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Down here, seedlings struggle to grow.

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But the gloom is not eternal.

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The death of a forest giant is always saddening.

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But it has to happen
if the forest is to remain healthy.

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The sudden blaze of sunlight
will bring life to the forest floor.

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A single hectare of rainforest
may contain as many as 250 species of tree.

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That's nearly 10 times the number
that grow in Britain.

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And the thirst for light triggers a race
for a place in the sun.

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There's no time to waste.

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A seed that may have fallen only a few days ago
now bursts through the leaf litter.

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With so many competitors,
getting a good start is critical.

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But each plant has its own particular strategy
for making the most of this rare opportunity.

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The seeds of hardwoods are quick to germinate.

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But like the fabled tortoise,
their strategy is to be slow and steady.

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Vines and other climbers put all their energy
into rapid vertical growth rather than girth,

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though they'll need to be well-supported.

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The climber's strategy looks chaotic
but there's method in their madness.

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Their growing tips circle like lassoes
searching out anchors for their spindly stems.

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They put coils in their tendrils

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so that if their support moves,
they will stretch and not snap.

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But the frontrunners at this stage,
the first to fill the clearing,

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are pioneers like the Macarangas.

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Their immense leaves
capture huge amounts of sunlight,

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so fuelling their growth.

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As a result, the Macarangas
grow a remarkable eight metres a year,

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surging ahead of almost all their rivals.

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In the race for the top spot, hundreds will start

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yet few will ever reach the finishing line,

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their growth cut short by the diminishing light.

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In less than four years the gap will have gone,

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but that's not the end of the race.

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The ultimate winners are the tortoises,
the slow and steady hardwoods.

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When the short-lived pioneers have fallen,
it's the hardwoods that take their place.

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And a 50-metre giant like this one

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may keep its place in the sun
for another 200 years.

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At the top is the canopy,
the engine room of the jungle.

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It's up here that most of the animal life
in a rainforest can be found.

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But despite the apparent abundance
of vegetable food,

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gathering it is seldom easy.

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With no real seasons, each tree flowers or fruits
at a different time of the year,

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which means that food is very widely spaced.

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Monkeys, like these tamarins,

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must search the canopy for all kinds of food
if they're to survive.

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But across the world's rainforests,

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there's one type of fruiting tree
that always delivers.

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The fig.

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Wherever they grow, figs are a magnet
for a great diversity of animals.

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In the Amazon,
the first to appear are the spider monkeys.

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These large primates are big fig-eaters.

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But they won't have the tree
to themselves for long.

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Others will want a share.

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Like the diminutive Emperor tamarins.

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The tamarins love figs, too,
but being petite means they're easily scared off.

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Squirrel monkeys are also small,
but they have strength in numbers.

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Their time-share on the tree may be short
so their tactics are more smash-and-grab.

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Capuchin Monkeys are the bully boys
in these forests

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and they want the ripe figs for themselves.

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Figs are one of the few trees
that fruit the year round.

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So when other food is scarce,

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these fruits are always available
somewhere or other.

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Even for leaf-eaters like howler monkeys,
the ripe figs are just too good to miss.

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And howlers are too big
for the capuchins to chase off.

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Figs are so popular that as many as
44 different kinds of bird and monkey

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have been seen working a shift system
on a single tree.

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Because fruiting trees are so valuable,
many monkeys are territorial.

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And if you live in the treetops,

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there's perhaps no better way
of staking your claim to a territory than this.

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The calls of the Siamang gibbons begin as a duet
between the dominant male and female.

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The rest of their family soon join in
and it results in a frenzy of activity.

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The calls can carry over a mile
and their message is clear.

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They tell any neighbouring Siamangs,
"This is our territory, keep out."

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Up here, the calls of Siamang gibbons
seem to dominate the airwaves.

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But with the jungle's incredible diversity,
there are countless others trying to be heard, too.

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Every layer seems to beat to a different tune.

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In the early morning,
the forest's chorus is particularly rich.

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Sounds travel further in the cooler air.

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But few calls can penetrate
as far through the dense vegetation as this one,

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the deep bass solo of a male orang-utan.

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In the middle of the day, little stirs in the jungle

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and the hot, dense air muffles the sound.

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As the afternoon wears on,
a different set of players begin to warm up.

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Insects work in harmony, timing their calls
to fall between the notes of others.

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Many singers stick to precise schedules.

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And right on cue, the 6:00 cicada.

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Night brings out a whole new orchestra.

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The cacophony of competing calls
seems deafening to us,

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but frogs' ears are tuned to hear
only the calls of their own kind.

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The songs of courtship echo from all around.

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Male gliding leaf frogs leap from the treetops.

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To slow their descent,
they use their huge webbed feet as parachutes.

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These large tree frogs spend most of their lives
in the high canopy

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and only come down when it's time to breed.

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Once settled,
they begin to serenade their unseen females.

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Now it's time for the females to make their move.

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There's no shortage of suitors,
but this female has already made her choice.

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She's heading towards the loudest call
because loud calls come from big frogs,

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and big is best.

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But to reach him she must run the gauntlet
of a gang of smaller suitors.

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Their only chance of mating
is to make a sneaky interception.

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He scored.

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But with more females arriving all the time,
it's not over until the fat frog stops singing.

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Feet, so vital for gliding,
are now put to other uses.

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Two's company, three is inconvenient.

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But in any case,
all male frogs are equipped with dry thumbs,

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which enable them to get a vice-like grip
on their moist partners.

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It's a case of first come, first served.

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Living in such a humid environment means
jungle frogs are less tied to puddles and pools.

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And these even lay their eggs out of water.

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There's little chance of them drying out,
and up here they're safer from predators.

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Surprisingly, it doesn't rain every day
in a rainforest,

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but more still falls here
than anywhere else on Earth.

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On average, over two metres a year.

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A single tree can suck up
hundreds of tons of water each year.

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But the trees can't use all this water,

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so much of it returns to the air as vapour,
forming mist and clouds.

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In the Amazon, the largest unbroken stretch
of rainforest in the world,

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half of all the rainwater that falls

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comes from clouds
produced by the trees themselves.

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With so much rain,

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it's not surprising that many of the world's
largest rivers are found in rainforests.

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Inside the forest, the high humidity
creates the perfect conditions

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for a strange world where life is built on decay.

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Amoeba-like slime moulds cruise the surface,

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feeding on bacteria and rotting vegetation.

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Fungi also flourish on decay.

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These are the fruiting bodies of the fungi,

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the only visible sign of a vast underground
network of fungal filaments.

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In temperate forests, the build-up of leaf litter
creates rich stores of nutrients.

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That, however, doesn't happen here.

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Nutrients that reach the soil
are leeched out by the rain,

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but fungi are connected to tree roots
by their underground filaments,

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and by quickly consuming the dead,

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they help to recycle crucial minerals
straight back into the trees.

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And this recycling happens faster here
than anywhere else on the planet.

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There are thought to be nearly a million
different types of fungi in the tropics,

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the vast majority still unknown to science.

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But one thing's for certain.

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Without fungi, rainforests could not exist.

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Nothing goes to waste in a rainforest.

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The fungi become food for others,
like these beetle larvae.

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Finding the fungus isn't a problem for the grubs

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since their caring parents
actually show them the way.

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Incredibly, 80% of all insects live in jungles.

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Few are more successful than the ants.

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There can be eight million individuals
in a single hectare.

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But jungle ants don't have it all their own way.

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These bullet ants are showing
some worrying symptoms.

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Spores from a parasitic fungus called Cordyceps

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have infiltrated their bodies and their minds.

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Its infected brain directs this ant upwards.

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Then, utterly disoriented,
it grips a stem with its mandibles.

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Those afflicted that are discovered by the workers

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are quickly taken away
and dumped far away from the colony.

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It seems extreme, but this is the reason why.

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Like something out of science fiction,

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the fruiting body of the Cordyceps
erupts from the ant's head.

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It can take three weeks to grow,

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and when finished,
the deadly spores will burst from its tip.

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Then any ant in the vicinity
will be in serious risk of death.

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The fungus is so virulent
it can wipe out whole colonies of ants.

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And it's not just ants that fall victim to this killer.

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There are literally thousands
of different types of Cordyceps fungi

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and, remarkably,
each specialises on just one species.

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But these attacks do have a positive effect
on the jungle's diversity,

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since parasites like these
stop any one group of animal

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getting the upper hand.

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The more numerous a species becomes,

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the more likely it will be attacked by its nemesis,
a Cordyceps fungus.

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With so much competition,
jungles have become the home of the specialist.

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And this animal, in the island of Borneo,
is one of the most unusual.

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It's a colugo, or flying lemur,

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though this is something of a misnomer
as it doesn't actually fly,

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and it certainly isn't a lemur.

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In fact, nobody's quite sure
who its closest relative is.

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The colugo depends on a diet of young leaves,

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and to find enough of them,
it must move from tree to tree.

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The leaves are not very nutritious,
but then getting around doesn't use much energy.

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In a single night, a colugo might have to travel
as far as two miles.

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But that task is made easier
by its superior gliding skills.

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The secret of success in the competitive jungle
is specialising,

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and this has led to the evolution
of some very intimate relationships

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between plants and animals.

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These are pitcher plants, also from Borneo.

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Adapted to living in very low-nutrient soils,

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the pitcher plant gets most of its nourishment
from insects lured to nectar glands

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on the underside of the lids.

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Once on board, the waxy sides of the pitcher
ensure there's little chance of escape.

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Most slip to a watery grave.

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At the bottom of the pitcher,
glands secrete enzymes

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which help to digest the corpses,
so feeding the plant.

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But not all visitors have a fatal attraction
to the pitchers.

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The Red Crab Spider
spends its entire life in the pitchers,

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hanging on with threads of silk.

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Instead of building a web,
it relies on the water-filled pitcher to trap its food.

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When an ant falls in,
the spider simply waits for it to drown

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and then abseils down for a spot of fishing.

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00:34:02,400 --> 00:34:06,550
Alive, this ant would be far too dangerous
for the spider to tackle,

230
00:34:06,640 --> 00:34:12,070
so using the pitchers as traps
means it can get bigger meals.

231
00:34:14,320 --> 00:34:17,270
And the spider
doesn't rob the pitcher of everything.

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00:34:17,360 --> 00:34:21,230
The digested remains of its booty
will end up in the water,

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00:34:21,320 --> 00:34:24,310
providing instant food for the plant.

234
00:34:28,600 --> 00:34:33,070
Other food, like mosquito larvae,
seems to be out of reach,

235
00:34:33,160 --> 00:34:36,310
but the spider has another surprising trick.

236
00:34:36,400 --> 00:34:39,590
By taking its own air supply trapped in a bubble,

237
00:34:39,680 --> 00:34:44,030
the crab spider can actually dive
to the very bottom of the pitcher.

238
00:34:47,680 --> 00:34:49,470
Once the prey is captured,

239
00:34:49,560 --> 00:34:53,990
the spider hauls itself back up
its silken safety line.

240
00:35:01,360 --> 00:35:07,070
The pitcher is a one-stop shop for this spider,
but it's not alone.

241
00:35:07,200 --> 00:35:12,630
In the jungle there's competition for everything,
even a small water-filled pitcher plant.

242
00:35:28,560 --> 00:35:33,190
Such specialists create
the jungle's remarkable diversity.

243
00:35:33,680 --> 00:35:36,870
But finding enough food to survive
is so challenging

244
00:35:36,960 --> 00:35:40,150
that most animals living here tend to be small,

245
00:35:40,240 --> 00:35:42,550
though there are exceptions.

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00:35:50,000 --> 00:35:53,510
This is the Congo, in Africa.

247
00:35:53,600 --> 00:35:58,750
It's a vast wilderness
and the least explored of alljungles.

248
00:36:01,360 --> 00:36:07,750
From up here, the forest looks similar to the ones
that grow in the Amazon or Southeast Asia.

249
00:36:07,880 --> 00:36:11,870
But down below,
there are some unexpected sights.

250
00:36:29,120 --> 00:36:34,070
Crisscrossing this forest
are countless miles of highways.

251
00:36:34,160 --> 00:36:37,470
And they were made by something big.

252
00:36:46,600 --> 00:36:51,670
Forest elephants roam great distances
in their search for food,

253
00:36:51,760 --> 00:36:56,270
but to survive they must emerge
from the gloom of the forest.

254
00:36:58,320 --> 00:37:03,790
And clearings like this one are a magnet
for elephants from far and wide.

255
00:37:58,280 --> 00:38:03,270
These elephants live in much smaller groups
than their savannah cousins.

256
00:38:04,080 --> 00:38:09,350
This might be the first time that one group
will have seen another for a month.

257
00:38:18,960 --> 00:38:25,470
For the adult males, it's a welcome break
in an otherwise largely solitary existence.

258
00:38:33,560 --> 00:38:37,390
And they're not the only animals
attracted to the clearing.

259
00:38:39,960 --> 00:38:45,270
Forest buffalos and red river hogs
are also regular visitors.

260
00:38:45,880 --> 00:38:50,310
As are bongos, which are very difficult to see
outside these clearings.

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00:38:51,560 --> 00:38:57,430
All these large forest animals have come here
to collect an essential element of their diet

262
00:38:57,520 --> 00:39:00,310
that lies buried beneath the mud.

263
00:39:04,880 --> 00:39:09,110
And the elephant's trunk
is the perfect tool for reaching it.

264
00:39:23,320 --> 00:39:29,510
To get what they seek, the prospecting elephants
must first blow away the covering layer of silt.

265
00:39:51,400 --> 00:39:54,030
Satisfaction at last.

266
00:39:58,960 --> 00:40:01,870
They're collecting a particular kind of clay

267
00:40:01,960 --> 00:40:06,270
that contains vital minerals
scarce in their natural diet.

268
00:40:06,360 --> 00:40:12,350
It may be mud but there's just nothing
quite like it for enriching the blood.

269
00:40:13,400 --> 00:40:19,710
The clay also helps to absorb the toxins
found in many leaves that the elephants eat.

270
00:40:25,120 --> 00:40:27,990
There are other benefits to coming here.

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00:40:28,880 --> 00:40:30,870
These clearings are the only places

272
00:40:30,960 --> 00:40:34,910
where the forest elephants
can get together in such numbers.

273
00:40:35,000 --> 00:40:37,110
When they return to the forest,

274
00:40:37,200 --> 00:40:40,670
they will have to go
their separate ways once more.

275
00:41:00,760 --> 00:41:03,990
If large animals are rare in jungles,

276
00:41:04,080 --> 00:41:09,030
then groups of large animals
actually living together are even rarer.

277
00:41:27,520 --> 00:41:33,910
This posse of hunters is not only formidable,
it's also very large.

278
00:41:52,840 --> 00:41:54,750
In their search for food,

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00:41:54,840 --> 00:42:00,030
chimpanzees move effortlessly
between the forest floor and the canopy.

280
00:42:00,120 --> 00:42:03,750
They're one of the few jungle animals
able to do so.

281
00:42:18,160 --> 00:42:22,350
Figs are a vital part of a chimpanzee's diet

282
00:42:22,440 --> 00:42:25,590
and some just can't seem to get enough of them.

283
00:42:35,520 --> 00:42:39,710
But there's something special
about this stretch of forest in Uganda.

284
00:42:39,800 --> 00:42:42,270
Fruit is actually abundant.

285
00:42:47,960 --> 00:42:52,310
And a lot of food supports lots of chimps.

286
00:43:08,560 --> 00:43:10,710
At 150 strong,

287
00:43:10,800 --> 00:43:15,110
this community of chimps
is the biggest yet found in Africa.

288
00:43:15,240 --> 00:43:20,550
Their numbers are so large
that they need a big territory, lots of fig trees,

289
00:43:20,640 --> 00:43:22,990
and they're willing to fight for it.

290
00:43:32,040 --> 00:43:38,110
These calls announce the start of a raid
into land controlled by their neighbours.

291
00:43:44,080 --> 00:43:48,110
As they leave their core zone,
the patrol goes silent,

292
00:43:48,200 --> 00:43:50,470
occasionally stopping to listen.

293
00:43:55,000 --> 00:43:59,750
Signs of the enemy are detected
and examined closely.

294
00:44:14,040 --> 00:44:18,750
The chimp militia are now
at the very edge of their territory.

295
00:44:19,760 --> 00:44:23,150
All need to be on maximum alert.

296
00:44:31,440 --> 00:44:34,190
They must wait and listen.

297
00:44:55,120 --> 00:44:58,990
An unfamiliar chimp call raises the tension.

298
00:44:59,120 --> 00:45:05,230
It's an uncertain time,
the size of the rival group is as yet unknown.

299
00:45:08,600 --> 00:45:12,390
Not far away,
their neighbours are feeding in a fig tree,

300
00:45:12,480 --> 00:45:15,230
oblivious to the approaching dangers.

301
00:45:16,960 --> 00:45:20,550
The patrol moves off with a sense of purpose.

302
00:45:20,640 --> 00:45:24,630
They must remain silent
until they close in on their rivals.

303
00:45:36,440 --> 00:45:38,070
The attack is on!

304
00:45:40,600 --> 00:45:42,470
To intimidate their opponents,

305
00:45:42,560 --> 00:45:45,990
the aggressors scream
and drum on buttress roots.

306
00:46:05,840 --> 00:46:08,830
Several males corner an enemy female.

307
00:46:08,920 --> 00:46:12,990
It's a ferocious attack
and she's lucky to escape with her life.

308
00:46:30,240 --> 00:46:32,590
Others are not so fortunate.

309
00:46:39,040 --> 00:46:43,110
The battle won, a grizzly scene unfolds.

310
00:46:44,040 --> 00:46:47,310
An enemy youngster has been caught and killed.

311
00:46:47,400 --> 00:46:51,870
The carcass is shared between members
of the group and eaten.

312
00:46:55,920 --> 00:47:00,350
Killing a competitor makes sense
if you want to protect your food supply.

313
00:47:04,120 --> 00:47:08,670
But exactly why they cannibalise
the dead chimp is not fully understood.

314
00:47:10,000 --> 00:47:14,310
It may simply be a chance for some extra protein.

315
00:47:25,920 --> 00:47:29,950
Teamwork has brought
this group of chimps great success,

316
00:47:30,040 --> 00:47:33,390
but they'll soon reach the limits of their power.

317
00:47:34,600 --> 00:47:40,990
The competition for resources ensures
that no one species dominates the jungle.

318
00:47:47,640 --> 00:47:51,670
The rainforests' great diversity has come at a cost.

319
00:47:51,800 --> 00:47:55,950
It has made them the most finely balanced
ecosystems in the world,

320
00:47:56,040 --> 00:48:00,910
only too easily upset and destroyed
by that other great ape,

321
00:48:01,000 --> 00:48:04,070
the chimpanzee's closest relative,

322
00:48:04,160 --> 00:48:05,670
ourselves.