All language subtitles for The.Great.Rift.Africas.Wild.Heart.3of3.720p.HDTV.x264_Subtitles01.ENG

30 million years ago,

tropical Africa
was covered in dense jungle.

But not any more.

Here in East Africa,

the forest has all but vanished,

a changed landscape that is the stage

for the most epic wildlife story
on the continent.

And it begins in the forest.

Chimpanzees are perfectly adapted
for life in the trees.

They gather almost all their food
from the canopy.

But these chimps live
in the Kyambura Gorge of Uganda,

and will sometimes embark
on an unusual journey.

Their home,
in this narrow strip of forest,

is surrounded by vast,
open savannas...

..mile after mile of rich,
grass-covered plains.

Living on the border between forest
and savanna means the chimps

sometimes venture into this new and
exciting habitat in search of food.

But they don't feel comfortable
in the open grasslands,

so only forage for a few hours
at a time before
returning to the forest.

However, for countless other
species, this new habitat,

the East African plains, has
become fundamental to their survival.

So how did this part of Africa
change so dramatically?

30 million years ago, when the jungle
still shrouded the continent,

a vast plume of molten lava pushed
up beneath the plateau
of East Africa.

The Earth's crust cracked
under the strain,

creating Africa's Great Rift.

Great volcanoes sprang up
along the rift,

and triggered a chain of events

that changed the face
of the landscape for ever.

RUMBLING

Ol Doinyo Lengai
is still an active volcano.

Its Masai name means
"Mountain of the Gods".

Its latest eruption covered
the plains below
in a blanket of thick ash.

Ash has a profound effect
on the surrounding vegetation.

It dries harder than concrete.

It's so solid that tree roots
struggle to grow through it.

Huge swathes of East Africa's
Great Rift

are covered in tree-resistant
volcanic ash...

..stretching on the east side
from Tanzania into northern Kenya,

and along the arm of the
shorter Western Rift up
the valley floor of Uganda.

The rising rift valley
not only created towering volcanoes,

it forced up great chains of
mountains like these,

the mighty Ruwenzori.

They stand three miles high,

and like all the great highlands
of the Rift,

they have a huge effect
on the local weather

and, in turn, the surrounding
vegetation.

Mist and cloud rolls in
from the drenched jungles
of the Congo Basin

that lie directly west of the
Ruwenzori.

Warm, moist air rises up the
mountains.

As it does, it cools, so most
of the moisture falls on the slopes,

and little rain reaches
the plains to the east.

It's the Rift's unique combination
of restricted rain and volcanic ash

that keeps the forests at bay.

But the space left behind
is now a battleground.

Two determined colonisers fight
to stake their claim on the plains.

One competitor is rather small
and unassuming -

grass...

RUSTLING

..its challenger the only tree
that still holds out for
its place in the savannas...

..the thorn tree of Africa
- the acacia.

It's able to cope
because its shallow roots

can extract any moisture from
the soil above the hard ash pan...

..and its tiny leaves reduce
water lost by evaporation.

It's so successful,
it can grow six metres tall.

But it has a predator to match.

The acacia's small leaves
are nutritious enough

to support the world's tallest
antelope...

..lofty enough to exploit a niche
that no others can reach.

But the acacia crown is not only
attacked from the top down,

but also from the bottom up.

The gerenuk has a skeleton
that's adapted

to enable it to spend all day
standing on its hind legs.

But height isn't the only key
to unlock the acacia's defences.

The dik-dik is one of
Africa's shortest antelopes.

It can't reach the high crown,
and at ground level,

the acacia thorns are at their
fiercest.

But the dik-dik's tiny head
fits perfectly between the spikes,

and so the acacia
is attacked from every angle.

The acacia can just about cope
with the impact of nibblers like
these,

but there's one heavyweight
that does more than just snack.

LOW-PITCHED RUMBLING

Seedling acacias are simply
annihilated

by the world's heaviest vegetarian.

But adult trees aren't safe, either.

The elephant's trunk is sensitive
enough to select
individual leaves...

..but strong enough
to rip off entire branches.

The combination of tusk and trunk
makes short work of heavy wood...

..and a three-tonne body
makes an effective bulldozer.

A single African elephant
can flatten a tree a day.

And in the savannas of the Rift,
the herds number over 150,000...

..capable of wiping out
entire acacia woodlands.

Landscape gardening on this scale
plays an important role

in helping the acacia's competitor,
grass.

Grass makes up over 50%
of an elephant's diet,
so it's in their own interests

to clear the trees
and maintain space for grass to grow.

Grass, unlike other plants,
grows from its roots
instead of the tip.

This gives it astonishing powers
of regeneration.

It also means it can be
almost constantly cropped -

a never-ending supply of food.

This indestructible plant
has taken over the Rift Valley
plains.

It supports the greatest numbers
and diversity

of large grazers in the world.

SNORTING

But there is a downside.

Grass is hard to process, so grazers
have to consume vast amounts.

That means big guts,
and big guts need a big body.

A diet of grass also means eating
for up to 16 hours per day,

and that leaves little time
for the other important tasks.

These are Uganda kob,

the most abundant antelope
in the Western Rift Valley.

Somehow they find time to indulge
in a surprisingly complex mating
ritual.

The kob have a dedicated mating
ground, known as a lek.

It's where males gather
to flaunt themselves,

and the females turn up
to pick a mate.

The males want to hold
the best spot.

To win it, they have to fight.

It's all to impress the ladies,

who are very picky when it comes
to choosing the right mate.

The females are after the buck
with the best blood -

the strongest male,
holding the most coveted position

right in the middle of the lek.

The female chooses her mate,
and then allows him

to test her scent for hormones
to confirm she's ready to mate.

A female comes into season
every 20 days or so,

but is only receptive
for a couple of hours,

so there's not much time for
flirting.

Job done.
The exchange of genes is complete.

WHISTLING CALL

CALLS AGAIN

Now the female can relax
under the protection of her champion.

There is a selfish reason
behind her choice.

The middle of the lek
is actually the safest spot,

as a concentration
of distracted antelope

attracts the inevitable antelope
eaters.

Adult lions hunt best
working as a pride,

but this single mother is alone,

so providing for her family
of three teenage cubs
is all down to her.

PLAYFUL GROWLING

WHISTLES

Kob are fast, with excellent
eyesight,

and so during the day,
catching one is extremely tricky.

But as night falls,
the advantage swings to the hunter.

LION ROARS

ROAR REPEATED

For the mother lioness,
hunting is a serious business...

..best done without
her three boisterous cubs.

The mother wears a radio collar
so scientists can track her
movements,

but it doesn't hinder her hunting.

In the pitch black
of the moonless night,

both the kob and lioness
are reduced to near blindness.

They can smell each other,
but the lioness can't pinpoint
a target

unless it makes a sound.

So as long as the kob hold their
nerve and don't break cover,
they'll be safe.

Meanwhile, the hungry and impatient
cubs wander into trouble.

SNORTING

BUFFALO SNORTS

COUGHING ROAR

HUFFING AND SNORTING

The three cubs might look dangerous,
but they are only ten months old

and they won't learn to hunt
properly until they're two.

They're no match for these buffalo,

but the opportunity for stalking
practice is too good to miss.

Meanwhile,
their mother is on to something.

She digs down almost a metre.

SHE GROWLS

After a huge effort,
she only pulls out a tiny meal -

barely a mouthful.

But satisfying hunger is not
on this mother's agenda tonight.

These warthog piglets are
a perfect size for the cubs
to practise killing.

LION GROWLS AND PIGLET SQUEAKS

PIGLET SQUEALS

SQUEALING

She pulls out six
and saves them all for her young.

The sooner the cubs learn to hunt,

the sooner they'll be able
to help their mother.

Ambushing prey at night
is very effective,

but it's not the only way
for a cat to catch a meal.

The cheetah is the fastest runner
on the planet,

but here, speed is no good
without stealth.

He must use camouflage
to creep up on his target.

With only the grass as cover,
he can't get close enough for a
sprint.

and as the hartebeest
is one of Africa's fastest antelopes,

from this distance
he has no chance in a straight race.

But it might still be worth a go.

Unfortunately for him,
they are all fit and well.

A full sprint is heavy work
for a cheetah under the hot sun.

He'll need time to recover
before he can try again.

Antelope like this topi
use the long grass

to hide their babies from predators.

If they stay still
they won't be found.

But what if you want to be seen?

Then long grass can be rather
a nuisance.

This male widow bird has prepared
a dance floor to seduce a female.

But first, he needs to get her
attention.

The modestly clad females
are currently on the fence.

When one flies in for a closer
look...

..a male gives it all he's got.

The Rift's grasslands bake
beneath the African sun.

The long grass can become very dry,

and that makes it vulnerable to
one of nature's most powerful
forces...

CRACKLING

..fire.

Thousands of tonnes of dry grass
is enough to fuel a blazing inferno.

But the flames can provide a feast.

BIRDS CHIRP

Migrating sand martins brave
the smoke to take advantage

of the tiny insects
that flee the flames...

..a welcome windfall

to a bird on a 1,000-mile journey
from Africa to Europe.

This looks like devastation.

The grass has been burnt away,
and so have the seedling trees.

But because grasses store energy
underground in their roots,

within days, new sprouts
push through the fertile ash.

Grass may be tough enough
to survive even the hottest fire...

..but there is one force of nature
here that grass cannot
defend against.

It's an extraordinary creature,

and it only comes out at night.

A hippopotamus has a mouth
half a metre wide,

built for devouring grass -
40 kilograms in one sitting.

A fussy eater,
it only likes short grass,

which it tears up with great lips.

Hippopotamus roam for miles
between dusk and dawn

in search of good grazing.

But there's a limit to their range,
and they must turn around

and head back to water
before the sun rises.

RHYTHMIC GRUNTING

RHYTHMIC GRUNTING

The still, shallow waters
bear their great weight.

Now they relax, snooze,
and socialise in comfort.

Mzima Springs lie
in the Eastern Rift,

a source of water filtered
through ancient Rift Valley lava
that never dries up.

This is a haven
for a small population of hippo,

who graze the savanna
in a ten-mile radius
around the spring.

But now the surrounding area
is in the deathly grip of drought.

With no rain,
the grass has stopped growing.

Like all hippos, the Mzima herd
are bound to their pool,

so can't escape
to search for pastures new.

Before long, the hippos will eat
everything within range,

and that will create a disaster.

They brave the sun in
a desperate search for food,
but to no avail.

Weakened, they sicken and die...

..but not before they have reduced
this savanna to a dust bowl.

The topsoil has blown away,

and even the roots of the grasses
are destroyed.

It will take this part of the Great
Rift Valley many years to recover.

The rain shadow of the Rift Valley
makes the grasslands extremely dry...

..but just enough rain makes it
across the mountains
to keep the grass alive.

THUNDER CRASHES AND ROLLS

THUNDER RUMBLES

Not everyone enjoys the rain.

But for the Uganda kob,
it's a joy not to feel
plagued by hunger or thirst.

When the rain clouds make
it across the mountains
of the Western Rift,

they bring the grasslands
exploding to life.

GRUNTING

THUNDER RUMBLES

The prevailing winds that
bring the rain move
in a north-south cycle

up and down the continent.

The resulting wet seasons
bring intense downpours,

but not to everywhere at once.

These isolated rains
mean that some animals

have to run for thousands of miles
in search of freshly grown grass.

LOWING

Every year, almost two million
wildebeest

follow the thunder clouds
like storm chasers,

trekking from the Serengeti
to the Masai Mara.

And in their wake
comes Thomson's gazelle.

Tommies are one
of the smaller antelope
found in the Rift savannas.

Their size makes them
very vulnerable to predators.

These cheetahs have been waiting
for the tommies for months.

Now's their chance
to eat as much as they can.

FLIES BUZZ

Each cat has a different style
of hunt,

but stealth is always key

if they are to stand a chance
against the fleet-footed tommy.

The cheetah is faster,

but the tommy can turn quicker
and has more stamina.

Each chase lasts
only 300 metres at most,

but those few seconds
decide the fate of the tommy.

TOMMY BLEATS

THEY SNORT

In a fair chase, the cheetah has
a 50/50 chance of catching a meal -

the highest success rate
of all the African big cats.

An unlucky stumble is enough
to seal a tommy's fate.

BLEATS

FLIES BUZZ

For savanna herbivores,
living here has a price.

But the richness of these grasslands
make it worth the risk,

and the rewards are so tempting that
even a primate has made them home.

Primates are normally forest
dwellers.

To flourish on the open plains
has been a hard step to take.

The olive baboon
is one of very few monkeys

to make a success of savanna life.

For a small animal on the plains,
there's safety in numbers.

Living in a large troop
requires organisation.

To avoid constant squabbling,

the baboons have developed
a sophisticated social order.

Regular grooming
is not just for reasons of hygiene.

The constant contact
is important for social bonding.

It's a good way to make friends.

Males are tough enough
to look after themselves,

and come and go as they choose.

But mothers and babies
must stick together.

The little ones are very important
for establishing rank and order.

BABY SQUEALS

This baby is being used
to keep its mother in her place.

The mother must sit
and watch it being treated roughly

by the more dominant female

if she wants to stay
within the safety of the troop.

Her low rank means she has no choice
but to tolerate her oppressor.

Whilst the inequalities of baboon
society might seem harsh,

this system of complex relationships
and communication

is essential
for their survival in the savanna.

UNDERDOG SQUEALS

When darkness falls,

the baboons' sharp senses fail them

and they must return to the trees
to sleep,

safe from night prowlers.

Baboon behaviour can give an insight

into what it takes for any primate
to survive on the savanna.

Our own primate ancestors
may have coped on the
open plains in a similar way.

But there's another primate
in the Rift Valley

that can tell us more
about our ancient history.

In Uganda's Kibale Forest, chimps
are bedding down for the night.

They bend branches into a nest
for a restful night's sleep,

just as our common ancestors
might have done

over eight million years ago.

Our ancient relatives living
in the primeval jungles of Africa

shared the well-developed brains
and nimble hands of modern
chimpanzees.

But at the same time
that the Great Rift Valley formed

and the forests were pushed back,
our ancestors moved out

into the savannas, leaving
their chimpanzee relatives behind.

Chimpanzees are still poorly adapted
for savanna life.

Their bodies are too squat
to see over the long grass,

and their limbs
aren't built for speed

like an antelope
that can outrun predators.

But like humans today,
our ancestors walked tall on two legs

and had hands free to carry weapons
for hunting and defence.

More meat in our diet
meant our brains expanded

and our societies grew
ever more complex and powerful.

In time,
we became masters of the savanna.

We owe our extraordinary success
as a species to this place -

the cradle of humanity...

..in Africa's Great Rift Valley.

Filming sleeping chimps in the
forests of Kibale National Park

presented some serious challenges
for the crew.

They had to climb huge tropical trees
in the pitch dark.

But first they had to find
the chimps,

and that meant trekking
for miles through the jungle

with some serious baggage.

Once they found them,
they had to wait until dark,

when the chimps
had picked their nesting spots.

Their mission was to climb
into the canopy
and film the chimps sleeping -

from above.

But this meant climbing in the dark,

which would put the crew
to the test.

Chimps nest anywhere between
4 and 40 metres off the ground,

and never in the same place twice.

The first task is to find a tree
suitable for climbing

without disturbing the chimps.

When darkness falls,

the team use image-intensifying
scopes to look into the canopy.

The final say goes
to tree-climbing expert Tim Fogg.

WHISPERS: It's not good at all.

There are no trees which give us
a view of the nests tonight.

It's just really frustrating,
because they're...they're all here -

there's about six or seven nests
right above us

and a bit off to that side,

but there's no big trees
overlooking them,

so we're stuck...
stuck on climbing tonight.

I think we'll probably just do
ground shots of them.

I can't see anything I can get up
that's any use at all.

Grounded for the night, they set up
the kit on the forest floor.

Cameraman Martin Dohrn has developed
a brand-new night-vision camera

that can see
without any artificial light at all.

It's called a starlight camera

and it uses an image intensifier
that means it can capture

unique animal behaviour not usually
visible to the human eye.

WHISPERS: Amazingly, we have now got
a shot of a sleeping chimpanzee.

It's not a great shot,

it's not a remarkable shot,

but it is probably
the first time ever

that a chimpanzee has been filmed
asleep in its tree nest.

This is actually kind of like Big
Brother, only more interesting.

But the team aren't satisfied
with filming from the ground.

Encouraged by their
terrestrial success,

the next night sees the crew
stalk the chimps

to a much better location
for climbing.

There is a big tree
right in the back there.

It's just whether we'd get
a view through.

The big tree behind that. There's
a much higher tree behind that.

Yeah, I think so.

Tim aims his catapult
at a branch high in the canopy.

OK. I think I got that.

Chimps are super-sensitive
in the night,

and no-one knows how they'll react
to a film crew swinging above them.

CHIMPS SHRIEK

Getting the ropes up is just
the start of the climbing process.

We've got to load-test
the ropes now,

and what I'm dreading
is that when we pull...

We're going to hang two
of us on the ropes

to see
if the branches will hold it,

and if it breaks,

I don't know, well, it's going to
cause mayhem with the chimps.

It's... But we have to try.

Safety-wise, I can't go up there
without seeing

that the branches are strong enough
to take me, so that's it.

Satisfied the ropes
are strong enough,

Tim heads up the tree with no idea
what he might find
in the jungle canopy.

OK, well, it didn't go to plan,
really, because, er...
I started climbing...

The ropes went in really easily,
amazingly, and then
I started to climb,

and as soon as I hit some foliage,
I started getting
the odd little itch.

And by the time I got through
the first bit of foliage,
I was flailing.

I was covered in tiny little ants
that were just on a suicide mission.

They were just eating me alive.

And I tried to climb on,

and I got a bit further up,
and they were still going at me.

They started getting in my sleeves

and then all around my waist,

and then they started getting
all round my neck.

They got in my helmet as well,
so at one point

I had to get my helmet off
and try and shake them out.

Nasty little things.

Undeterred by creepy-crawlies,
Tim and the team head back
to the jungle

hoping for a more successful climb.

CHIMPS BARK

WHISPERS: It's incredibly close.

It's about...maybe six metres
above and just behind me.

The tree I'm going for
is just over that way.

That should give us a good shot
down on him...in his nest.

That's what we're aiming for.

I've noticed that I'm right on
a big pile of elephant-do.

Just putting on some insect
repellent.

Then I'm going to tape my sleeves up

because I want to try and keep
the ants out if they're there
this time.

Geared up once again,
Tim heads up to check the view.

Martin prepares to record from the
ground,

and tree-climbing specialist
cameraman Nick Turner

can finally take to the trees.

And right behind him,
Martin sends up a precious cargo.

The world's only HD starlight camera
is in the bag,

so let's not stand under it
in case it falls.

It's a real mess up here with gear,
I mean, we know where everything is,

but it's just everything has to be
tied on so we don't drop anything.

There's cables and tapes and ropes
and karabiners all over the place.

We're about 15 metres off the deck

and the chimps are about 10 to 12
metres away from us,
down slightly.

The team are close to success.

But before they can even take
a shot...

RATTLING

What's going on?

..the armed ranger has heard
something.

It seems we've got some elephants
coming close to us

and we're not sure what to do
or what they're going to do.

So we're leaving our lights on
so the elephants can see us

and don't get suddenly surprised.

I'm pretty sure they'll just try
and stay away from us...

but you never know.

Elephants have very poor eyesight
in the dark.

If they come across the crew,
they might take fright and attack.

We think that might be an elephant.

ON RADIO: We should have
a B-plan here.

They're probably curious
rather than dangerous, but...

I'm not an expert in elephant
behaviour.

My plan is to run behind the tree
and hide.

Possibly even...

try and climb up into it.

Probably get up there.

I'm afraid that's the best I can
offer.

You're probably quite safe up there.

I don't think they'd be able
to knock the tree down

but what I'll make sure I do
is I'll set the thing in

to record before I go, so...

I can't imagine the chimps will be
too happy about having elephants

running around like that.

With nowhere to hide,
the crew carries on

and the guard comes back with news.

There's a chimpanzee.

It's a chimpanzee. Are you sure?
Yes, of course.

The chimps have been
playing tricks on the crew.

So once the fear of elephants
is passed,

they can get on and film the nesting
chimps from high in the canopy.

Martin's starlight camera gives us
a grainy black-and-white image,

but allows us to see into the night

and watch wildlife
at their most intimate moments.

It showed for the very first time

how these great apes snuggle down
in the treetops

and how it's possible to have
a comfortable night's sleep
in the jungle.

Subtitles by Red Bee Media Ltd

E-mail subtitling@bbc.co.uk