All language subtitles for Equator 6 Challenge Of Change 2005 1080p

The sun...

giver of light and life,
shines most powerfully at the Equator.

Here, it powers
an extraordinarily rich zone of life.

Brilliant and bizarre species from
three continents... three oceans.

More than a line on a map...
Equator is a powerful force of nature.

EQUATOR

Challenge of Change

The Equator meets
the western edge of Africa

on the coast of Gabon.

It's one of few places
in all of Africa

where forests grow down
to the shore...

and where forest animals come
in search of new opportunity...

To change or adapt can be
a successful survival tactic.

And survival may depend on
exploring unfamiliar frontiers.

Where are these Hippopotami going...
and why?

Venturing into the unknown is

a recurring survival story here
on a continent

that has undergone huge upheaval.

Animals have had to meet
the 'challenge of change'... or perish.

In Equatorial East Africa
is the arid savanna...

such landscape is rare at the Equator.

Equator lands around the world are
mostly forest covered... and wet.

Here, on the savanna,
it hasn't rained for months...

The unrelenting heat of the sun
has sucked the earth dry...

none but a few animals
can endure it.

Riding powerful heat waves
are vultures.

They are winged
harbingers of death.

...In the dry season,
survival is all that matters.

In the dry season, lions are
forced to steal from vultures.

Lions remain on the savannah
throughout the long drought.

Hunger is a constant companion

and they can only gaze out
on depleted hunting grounds.

A Thomson's gazelle
will not satisfy their needs...

but it will help.

Day after day,
the pursuit ends in failure.

Each hunt saps energy,
especially for females with young.

Mothers have little milk...
and their cubs are weak.

An adult lion must eat
10 kilograms of meat a week...

any less, and they and their young
will be in peril.

In the dry season,
90% of cubs may starve to death.

And death comes in other guises.

Hyenas are also desperately hungry,
and they are cub Killers.

Lions remain on this arid plain
during the dry season

because their fate is linked to
protecting their hunting domain...

and their fate is linked to
a drama that is about to unfold...

In November, cool trade winds
begin to blow from the south...

Animals can sense a change long
before it happens.

Great herds are on the move,

millions of animals begin
a long journey toward the savanna.

As they approach,
so do dark heavy clouds,

clouds that bring a much
needed gift to the dry plain.

The change is sudden and dramatic...
and so are showers.

It pours for less than an hour...
and stops...

At least it's cooler
after these brief downpours,

and animals can drink,
there is water everywhere.

Every day grasslands flood,
then slowly dry out...

this will be the pattern for
several weeks...

The rains come as the region
approaches it's hottest time of year...

as the sun advances to
its highest point...

The sun that parched and
cracked the land for months

now brings clouds and rain

to quench the deep thirst
of the dusty plain.

The herds of
the great migration

time their journey to coincide with
this abundance.

As far as the eye can see,

new growth is feasted on by
close to 2 million wildebeests,

other gazelles and zebras.

Animals not only time their
migration to the coming of the rains...

it's quickly followed by
a frenzy of births and babies.

All wildebeest calves are
born within just one month

and they must quickly
find their feet

to keep up with their mothers.

The birth bonanza further
swells animal numbers.

Parts of Equatorial East Africa
now contain

some of the greatest aggregations
of animals on the planet...

Equatorial Africa hasn't always

hosted such spectacular
animal numbers...

in the past it was
a very different place.

For a long time, Africa was isolated

from other land masses
and mostly covered in forest...

in these forests lived ancient animals
whose descendants survive today...

Perhaps the most famous of
these early Africans is the elephant.

It is descended from
a much smaller creature thought

to be related to the hyrax...

is it possible the mighty elephant
once looked like this?

Primates also look nothing like
their African ancestors...

Where as the strange,

termite eating aardvark has
changed little in 60 million years.

About 20 million years ago,

Africa underwent
a dramatic transformation.

Land and sea level changes brought
Africa and Eurasia closer together,

until they finally connected.

The joining of continents brought
an influx of strange new animals.

Most were forest dwellers...

among them were hogs
and strange horse like animals,

as well as ancient antelopes...

and with them came predators...

including cats of many kind...

...Some of these ancient species
brought secrets

that they handed on
to their descendants...

This is the Okapi,
a name that means 'forest horse'.

Although it's the size
and shape of a horse,

it shares a common ancestor...
and a secret, with the giraffe.

African Bush Bucks retain

the primitive shape of
their European forbears...

but they also inherited
a very special gift

from their forest
dwelling ancestors.

The first antelopes
had multi chambered stomachs.

They contained bacteria,

that allowed them to
digest low-nutrient plants

that other herbivores could not eat.

This 'secret weapon'
stomach would

one day transform life
near the Equator...

but while forests
covered the continent,

there was little opportunity
for these animals.

However their fate would be
determined by other events in Africa

and one was
particularly earth shattering.

About 30 millions years ago,
East Africa was torn apart.

Slowly, a great valley opened
and highlands

were thrust up by
enormous volcanic forces.

Over millions of years
The Great Rift Valley spread north

and south for over four thousand
five hundred kilometers.

The Ethiopian Highlands
rose up to 3,000 meters...

blocking rain bearing clouds
from the west,

creating a rain shadow area
in East Africa.

As the land became drier,
rain forests slowly vanished...

and grasslands appeared.

Grasses slowly covered
the drier parts of East Africa...

These new grasslands would
profoundly change life at the Equator.

And first change was to
the plants themselves...

Being close to the Equator,

the intense power of
the sun favoured a group of grasses

called "Carbon 4" or C4 plants.

These grasses possess

a revolutionary pathway
for changing sunlight

and carbon dioxide gas
into sugars.

In most grasses,

the cells that carry out
photosynthesis,

are near the leaf's upper surface.

In C4 plants, they are packed
tightly around sheath cells.

...and as CO2 enters the leaf,

the outer cells of this bundle,
concentrate the carbon dioxide.

This is the CA plant's secret weapon...

the leaf's like an engine
with a turbocharger...

It rapidly manufactures sugars

and growth rates are up to 8 times
faster than other grasses.

...and as the power of
Equatorial sunlight increases,

so photosynthesis can
increase almost indefinitely...

The whole system is
encased in a tough outer core,

and this made these grasses
very difficult to digest.

CA grasses out competed

and replaced other grasses
in the hottest parts of East Africa...

But these new "grasslands”
were tough,

inedible wastelands for
many grass eaters...

however,
the new plants proved to be

highly desirable for
one group of animals...

For millions of years,

these animals had been
forest dwellers,

but as the new grasslands spread,

they emerged to graze
on these tough,

nutrient poor plants.

The animals are called ungulates,
a name that means 'hoof'...

but being able to digest grasses...

gave rise to another name...
ruminants.

They're called ruminants,
in honor of their 'super stomachs'...

They'd inherited a 3 chambered
stomach from their ancestors...

but even this was not adequate
for the job of digesting CA grasses.

These tough plants required
more powerful digestion...

It's probable that it was
on the dry grasslands

that grazers evolved
a new model of stomach...

It had a large extra chamber
called the rumen,

where the grass
is first broken down.

The agents of digestion
are microbes.

They attack the grass's
tough cell walls,

releasing sugars and vitamins...

but this is only the first stage.

Partly digested grasses are pumped
from the second stomach

back to the mouth and
chewed again to speed up the next stage

that takes place in the 3rd stomach.

Here, the grassy broth feeds bacteria
that multiply quickly and dramatically.

Finally, the contents move to

the last chamber
which are the true stomach...

This is where final digestion
takes place...

By now, the animal
is not only digesting grass,

it's also digesting
a high protein diet of bacteria.

The ruminant 'super stomach"

has allowed some herbivores to
grow large... and powerful...

Modern ruminants arose in Africa
about 2 million years ago.

The buffalo has grown to
be one of the biggest

and most lumbering
of ruminants...

but others differ hugely
in size and speed.

Thomson's gazelles
are lightly built sprinters.

Wildebeests are marathon runners,

but there are many
other swift athletes of the savanna.

The biggest of all is the giraffe...

Ruminants now occupy
many different habitats and lifestyles.

Klippspringers keep to
steep rocky outcrops...

Areas of low bush and shrubs
are favoured by Gerunuks.

Tiny Dik Dik feed deep inside
the thickest bush.

Fast, agile Impala are
one of many open plain gazelles.

Reedbucks are
secretive wetland dwellers...

as are waterbucks

The preferred range of Nyara
is semi desert...

whereas, Oryx inhabit
the very driest desert areas.

There are 125 species of antelope
in Africa...

almost 90% of the world total.

They've conquered the grasslands
in spectacular fashion...

animals range in size from
half a meter to 5 meter giants;

from loners to herds of millions...

The ruminant stomach
has other advantages...

grass is digested more slowly
and thoroughly,

and because it is more efficient,

Antelopes don't have to
graze constantly...

When an approaching enemy
is detected...

escape is swift and sudden.

The herd has many eyes,
ears and noses to sense danger...

and this has shaped the evolution of
their main predators, the cats.

As antelopes evolved,

so cats changed to become
more deadly predators.

A leopards spies its prey
from the treetops.

Its ancestors were
probably tree dwellers too.

In the grass,
it's silent as a shadow...

slowly working its way into range.

The leopard
doesn't kill immediately...

there may be others
that would steal it...

the home tree is the safest place.

The leopard has developed stealth

to outwit the antelope's finely
tuned sense of danger.

The cheetah is
a cat of the open savanna...

out here, there's nowhere to hide...

it uses a different tactic to
hunt prey... it uses speed.

If it can begin the chase
before its prey sees it,

the cheetah has the advantage.

In Africa, the cheetah's body shape

became adapted to run down small,
fast antelopes.

Exploding to reach speeds of
110 kilometers per hour,

it's the fastest land animal
in the world.

It's body became streamlined,

its claws work as spikes,
it is light, flexible and powerful.

The grasslands have boosted
the number of small fast gazelles...

and cheetahs use blinding
speed to outrun them.

Of all Africa's cats,

the lion has been most shaped
by the Equatorial sun.

Lions live in family groups
called prides...

they are the only truly social cats
in the world.

They are also the biggest cats
on the savanna.

Males stand over a meter high
and weigh 260 kilograms...

yet, despite their size,

males remain on the margins
of lion society.

A lion pride is
an extended family of several

to dozen females and their young.

It is a society of females...

all are equal, all breed at
around the same time...

The oldest female in this pride
wears a radio tracking collar.

She's the leader; she has much
useful experience and knowledge...

The male's role is to defend

the pride's territory
and father the cubs.

The lion's imposing size

and unique social structure
exists for a reason...

the biggest cats in Africa,

work in groups to hunt some of
the largest plant eaters...

Yet, even working together
does not guarantee success...

prey animals often see lions
from a long distance...

so most hunting is done after dark.

Night is the killing time...
when many animals are active.

Darkness restricts the vision of
prey animals

allowing lions to get closer...

but they hunt at night mainly
because it is cooler.

Hunting uses a lot of energy...

lions easily overheat
under the blazing sun...

night kills are preferred.

A lion hunting party
is highly organized.

Once a group of prey animals
is identified,

they are slowly
and quietly surrounded...

When all lions are in position,

one or two will
make themselves visible.

The gazelles move quickly away...

but the trap is set...

they run into the waiting jaws
of the group.

The Kill is shared
among members of the pride...

Each pride has a hunting territory,

and the constant mission for
the male is to protect both pride

and territory against other males
that would overthrow him.

The territory can extend
over 100 sq kilometers...

And his loud roar
can be heard over most of it.

As he patrols, he leaves
scent marks along the borders.

A successful hunt does not
always mean enjoying the Kill...

As they feed, the females are
surrounded by a band of hyenas.

For their size, hyenas have
the strongest jaws in Africa...

they're not to be taken lightly...
and they outnumber the lions.

The females have no choice
but to give up their hard won meal.

But now the male returns...

The Hyenas victory is short lived...

superior numbers are
no match for an angry male lion.

And when he returns,
his mood has not improved...

The price of protection is
that he takes over the Kill.

One of the hunting females
now departs.

She returns to the Kill
with the nursing females

who are caring for
all the cubs of the pride.

The male allows the young cubs
to feed alongside him...

It's a privilege he is not prepared to
extend to the female.

For the male, the safety and
survival of the cubs is most important

as they carry his genes.

The male may bully his way
to first helping of the Kkill,

but the females control the pride...

Their major imperative
is a strong society...

and to retain their hunting territory.

The lions hunting territory is passed
from females to their daughters...

Young males must leave
the pride once they reach maturity...

this keeps the pride strong by
removing the risk of inbreeding.

Male blood moves
from pride to pride.

Young lone males are called Nomads...

this nomad has
spent the previous month

wandering and hunting by himself...

He's just 2 years of age,
with just the beginnings of a mane.

He's still far too young to
challenge a full grown male.

Nomads often lurk
on the fringes of prides...

They mount frequent challenges,

to test the strength and
speed of the dominant males.

One day, the pride male will not be fast
or strong enough to defend himself...

but that day is not today.

This nomad will return,
he will keep trying...

if he can survive out there
on his own.

The "Nomad"” strategy ensures that
strength is bred into all lions...

strength to face
the hardships of the dry season...

and strength to hunt large
herbivores on the savanna.

There's one plant eater
that's taller than all the rest...

Giraffe are so big;
they're rarely attacked by Lions.

The giraffe has a ruminant stomach
but it does not graze the savanna...

Its long neck gives it
access to acacia trees,

one of very few trees that
can survive these conditions.

Acacia leaves are rich in nutrients...

but they're well protected...
eating is a delicate art.

Giraffes can easily
reach high into the trees...

but they experience some difficulty
bending to graze or drink.

One problem from having such a long neck
is controlling blood pressure...

specifically,
the pressure of blood to the brain.

When standing upright,

the giraffe's heart
must raise blood pressure to

more than twice human pressure

in order to push the blood up
the neck and into the head.

But when it bends down,

all that pressure should suddenly
rush blood to the head and potentially

cause fatal hemorrhage...

but it doesn't.

That's because, a giraffe has a
special blood pressure control organ

just beneath its brain.

The structure, called a "wondernet”,
is a network of blood vessels.

As blood rushes to the head,

the wondernet absorbs
the increased flow

and swells like a sponge.

As it swells,
arteries between wondernet

and brain bend and crimp
like a water hose,

further reducing blood flow.

The wondernet enabled
the giraffe to become

the tallest animal of the Equator
and reach for the richest food...

but how did it come about?

It is likely that as grasslands spread,

the giant giraffe evolved from

a short necked forest ancestor
very quickly...

because of a secret it
brought from the forest...

And that secret is still found

in the remotest parts
of Eastern Congo...

it lives on in
the giraffe's forest relative.

This relative stands only
one third of the giraffe's height

and is the forest horse,
the Okapi.

The short necked okapi

doesn't need to regulate
it's blood pressure,

yet, it also has a wondernet...

and this could explain
how the giraffe evolved.

Okapi and giraffe have
a common ancestor... the Paleotragus.

If it could be proved that
it too had a 'wondernet',

it would solve the mystery of how
the Paleotragus of the forest

could so rapidly become
the giraffe of the savanna...

It's possible that the Giraffe was
pre adapted to life on the savanna...

but one of Africa's original inhabitants
went down aquite different path

to survive life on
this arid region of the Equator...

It changed its brain
as well as its body.

Elephants don't
have ruminant stomachs...

so, how do they beat the heat...
and the dry?

They do it by being
'super sized'.

In dry seasons,
smaller animals will starve whereas,

larger animals, like elephants,

eat less food per unit of body weight,
and are more likely to survive.

But elephants also
grew their brains.

They use their tusks as a tool to
peel away tree bark for nutrients.

In the dry season,

they remember where
the best feeding grounds are...

and pass this knowledge
on to their offspring.

Elephants might be less efficient

than ruminants at turning plants
into energy...

their survival is
based on brain power and size.

Hippopotomi are also giants.

They spend much of the day
in rivers and lakes,

to protect themselves from
the sun's powerful rays...

the pink colour is not sunburn

but a form of sunblock that
they exude onto their skins...

The water also saves energy,

it helps support the enormous weight
of their thick skinned bodies...

Like elephants,
they don't have ruminant stomachs.

They too have increased body size

to improve energy efficiency
and their chances of survival.

Hippos have never shaken off
their strong bond with water...

they cannot survive
beyond rivers and lakes.

Yet unlike many animals of the savanna,

they are meeting
the challenge of change...

far beyond the dry plains
of East Africa.

Moving west on the Equator,

between the savanna and
Africa's Atlantic sea coast,

there's a mosaic of forest,
wetland and grassland...

This is what much of Equatorial Africa
looked like before the savanna existed.

...And helping maintain
this patchwork landscape

is an animal called
the farmer of the forest.

Red river hogs regularly commute
between forest and grassland.

From the forest, they bring seeds
that they spread on the grass...

Red River Hogs not only eat
the seedlings that grow up...

but they also spread the forest.

Forest elephants are half the size
of those on the savanna...

life in the forest is cooler,
food is more abundant,

they do not need to be giants...

But they are always
seeking new sources of food...

and during the rainy season,

their appetite draws them
toward the sea.

In their path, is a tangled
forest of mangrove trees?

These trees with long seed pods,
fringe the edges of lagoons...

and in these lagoons,
there are hippopotami.

These Hippos may look just
the same as those on the savanna,

but their behavior is very different...

they too are drawn to the sea...

but for reasons that
remain a mystery.

Animals come to the sea shore,

where the Equator meets
the western coast of Africa, in Gabon...

Why do forest buffalo come here?

They come here for food.

The rain washes vegetation
from the coastal forest

out into the ocean
and back onto the beaches...

animals seek out Mangrove seed pods

that contain high concentrations
of minerals.

Elephants also know of
this special food source...

and they pass this knowledge
onto their young.

But there is another surprise
appearance at the beach.

Hippos come to the coast...
but not to eat mangrove pods.

A Hippo mother and baby
seem attracted to the ocean.

It's strange to see them
away from rivers and lakes.

Yet, they seem at home here,

the baby is completely
submerged by the surf.

What draws them to the sea?

Perhaps they swim in
the ocean to wash off parasites.

...do they use the buoyancy of
salt water to travel along the coast?

...or do they feed on sea plants
that grow in the surf zone?

No one knows why they come here.

Only the hippos of Loango
in Gabon swim in the ocean.

In ancient times,

hippopotamus like animals went
down to the sea and became whales...

Perhaps swimming hippos,
on this unfamiliar frontier,

are the beginning of what could
become totally different animals,

tens of thousands years from now.

Are we are seeing evolution
in action in the surf of Gabon?

And are there
other evolutionary experiments

happening elsewhere
on Africa's Equator.

The jungles of Gabon and Congo
are dark and impenetrable...

but in places they open out into
broad wetlands called "bai".

Succulent grasses and bulbs rich
in minerals grow here...

and forest animals emerge to
search out these plants...

among them, west lowland gorillas.

These gorillas don't like the water
and will avoid it if possible...

but the drive to
get these precious plants

leads some gorillas to
overcome this dislike.

Not only is this gorilla
immersing itself in the water

but it is walking upright...

The buoyancy of water
helps it stay upright...

and it walks, arms raised,

like a reluctant bather,
not wanting to get wet.

It's tempting to imagine that this is

how our African ancestors
began walking on two legs...

...and if climate or other conditions
change here in the future...

perhaps a walking gorilla
will be better able to survive.

But change is already happening...

further east, animals are already
changing to cope with extreme heat.

Tsavo National Park Kenya,

is at low altitude and
has very high temperatures.

Here, lions live
at their limit of survival.

The earth is cooler
beneath the surface...

they try to avoid heat
as temperatures soar.

In the shade it is nearly 40...

out in the open it's close to
50 degrees Celsius.

Lions here, usually hunt at night,

but if prey wanders too close,
they cannot resist their instincts.

To bring down a buffalo in this heat
is hugely taxing of energy...

Lions overheat very easily...

if their body temperatures rise
they risk heat exhaustion and death.

Death comes quickly for the buffalo,

a throat bite constricts air
and blood flow.

After the Kill,

the lions must seek shade and rest
before they can begin to eat.

A daytime hunt can induce heat
exhaustion among these animals...

but in Tsavo, male lions have
another strategy for beating the heat.

Male lions here have
greatly reduced manes.

A lion's mane raises body temperature...

So, they have adapted to be

without their traditional symbols
of dominance.

Dominant males can still be identified
their short manes are darker.

If it gets even hotter at the Equator,

lions with short manes could
become a more familiar sight...

Dawn on the savanna...

A new day,
after another night of killing.

Over millions of years,

Equatorial East Africa has
undergone profound changes...

its animals have adapted...
and survived...

and every day that struggle
to survive continues

in battles between predator and prey.

East Africa is like no other place
on the Equator...

The incredible diversity of life
on the savanna has arisen

from merciless seasons of
dryness and thirst...

inflicted by the intense heat of
the Equatorial sun.