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This is the story
of the great wildebeest trek.

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It began with the birth of a calf.

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He was soon faced with many dangers.

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The calf even crossed a soda lake.

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A variety of spy-cams
tracked his journey.

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These recorded his adventures
in many new ways.

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They filmed him surviving an attack
by cheetahs.

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They even withstood
the full force of the rut.

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They then staked-out
the Grumeti river...

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..where Africa's biggest crocodiles
stalked the calf.

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This was his closest shave so far.

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Now, even greater tests await
the calf as the herd
continues its epic trek.

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The Mara River in Kenya, the most
northerly point of the migration.

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It's late July and the march
of the wildebeest stalls

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as it faces
this fast-flowing barrier.

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But there's no turning back.

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The wildebeest arrive
in tens of thousands,

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a unified mob on a frantic mission.

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For the adults,
it's an annual event.

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For the calf, it's the biggest
threat so far in his young life.

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The crossing points are traditional,

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but that doesn't make them
any easier,

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particularly when the river
is in full flood.

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Ferocious rapids lie
just below the crossing point.

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Each year,
they claim hundreds of lives.

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The calf faces
other unfamiliar hazards.

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It will be a major test, one
that others have recently failed.

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A gazelle seems remarkably
indifferent to the obvious dangers.

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The calf waits but, for the herd,

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the gazelle's impulsiveness
is a sign that all is well.

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As the first ones leap,

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it's like pressure
being released from a bottle.

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Mother and calf wait their turn.

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The front-runners leap wildly,

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a technique that probably scares
the crocodiles waiting in the water.

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But the same splashes also sound the
dinner-bell to those still asleep.

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The one that took the greatest risk
paid the price.

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Although nervous,

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the calf is pressurised by herds
massing behind him.

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They force him to take the plunge.

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At six months old, he is strong
enough to tackle most challenges,

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but this will test his stamina
to the limit.

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The rapids lie just downstream.

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The teeming throng force the mother
and her calf towards the maelstrom.

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The pressure builds still more.

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The calf stumbles on hidden rocks
and loses his footing.

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Mother and calf are both
swept away by the current.

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The whole herd is
being washed downstream.

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Many retreat,
but most are caught in the torrent.

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For the calf and his mother,
going back is not an option.

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Briefly, he finds a foothold...

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Then, panic sets in.

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Crocodiles deliberately select
particular victims.

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Mother and calf
have no room to manoeuvre.

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The mother is grabbed...

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The calf is swept away.

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The current is so strong
that the crocodiles can't fight it.

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Only a rock stops their struggles.

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The calf, too,
is battling for his life.

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But the crocodile's hold is awkward.

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Reinforcements arrive.

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The crocodile is tiring
and has to change its grip.

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Miraculously, the mother
is relatively unharmed.

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The calf
tries to keep his head above water.

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The crocodile is exhausted.

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It has to let her go.

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Mother and calf
rejoin below the rapids.

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Together, they make it ashore.

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Others are not so lucky.

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Every river claims its victims, but
each must nonetheless be crossed.

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Cheetahs love
these open grasslands, too.

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There's plenty of space for hunting.

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The wildebeest will eat most
of the grass before moving on.

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The grass reacts by growing.

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The more grazing and
trampling by the herd,

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the more it's stimulated to grow.

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But paradise comes at a price.

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As well as cheetahs, the migration
supports some heavyweight predators.

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Lions live here in higher densities
than most other places on earth...

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And the days of the migration
are the best days of their lives.

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The wildebeest will stay here
for the next three months,

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so the threat is something
they must learn to live with.

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The middle of the herd
is the safest place to be.

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This cheetah cub
is just one week old.

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Like all youngsters,
play is always on his mind...

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But his mother has work to do.

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The wildebeest have
fellow travellers.

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Thousands of gazelle
accompany the migration.

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Each kind of animal
grazes different lengths of grass.

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Thompson gazelles eat the shoots
left by the wildebeest.

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The long red-oat grass
provides perfect cover,

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but it's too long
for the wildebeest to eat.

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Given the choice,

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wildebeest prefer pastures that
have been grazed down by zebra.

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The calf runs.

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But this time he is not
the prime target.

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Tortoise-cam investigates.

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This apparently harmless creature
is of no interest to the cheetah.

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The cub is not old enough
to eat meat,

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but it is risky for him
to be alone.

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He looks for his mother.

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There is plenty to be nervous about.

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These are halcyon days
for the hyenas, a time of plenty.

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A ready-made meal is never far away.

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At this age, the calf makes
a more challenging proposition.

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Hyenas look for signs of weakness.

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Despite their reputation,
they hunt more than they scavenge.

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But when someone else
has done the work,

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they soon sniff out an easy meal.

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Her cub is in mortal danger.

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But even for a hyena,

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a protective mother
is a force to be reckoned with.

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He looks for an easier option.

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Among the multitudes, there's
always one that is sick or injured.

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When they reached the Mara,

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the population that peaked
at one and a half million

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on the calving grounds has lost
a quarter of a million animals.

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Most of those that died were calves.

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Black-backed jackals
also benefit from the daily cull.

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They are expert at snatching food
from under the noses of the hunters.

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They live on their wits,
but are rarely caught.

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They also give other scavengers
the run-around.

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Like a gigantic living lawn-mower,
the migration slowly eats its way

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across the plains,
consuming 6,000 tons of grass a day.

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Here the calf will spend a
quarter of its year-long journey.

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With the herd staying in one place,
our spy-cams can be everywhere.

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Even a tree stump spies on
the calf's every movement.

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Boulder-cam, was first used
in a film that spied on lions.

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Now, it finds a new
generation to entertain.

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As always, the lions' first reaction
is curiosity...

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But these cats are more
inquisitive than most.

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One cub has taken to it
in a big way.

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Boulder-cam doubles up
as a baby-walker.

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But then the mood changes.

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Boulder-cam captures
perhaps the closest shot ever taken

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of a stalking lioness.

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Every day,
the wildebeest go down to drink.

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In the Mara, the river provides
a source of drinking water

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the herds can rely on.

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The calf joins the midday throng.

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Wildebeest must drink at least every
other day to stay in condition.

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This is a risky time for the calf.

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Nearby, tortoise-cam
investigates the remains

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of a previous visitor to the river.

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The scavengers
are experiencing a glut.

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Carcasses can remain
uneaten for days.

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At the river's edge,
the biggest risk is from crocodiles.

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For the calf, danger can come
from an unexpected direction.

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This is the perfect
ambush situation.

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The prey are facing away
from the threat.

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It's chaos
and she's missed her target.

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But there are plenty
of others to choose from.

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They panic onto the plain and,
there, other lions wait in ambush.

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One is taken.

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Then another.

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Two kills,
within a bound of each other.

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Mother and calf keep running.

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They can never be sure where
the next lions might be hiding.

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Two carcasses
is just what a large pride needs.

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The cubs' births have coincided
with this super-abundance of food.

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But the Mara is so full of predators

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that existing cheek by jowl with
other hunters becomes unavoidable.

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If they are faced
with a large clan of hyenas,

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lions often avoid a confrontation.

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But these hyenas seem more intent
on fighting one another

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and that seems to intrigue
the lions.

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The victim is almost certainly
an intruder from another clan.

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The lions can't resist
making an advance,

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but it seems more
from curiosity than aggression.

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Without further bloodshed,
the hyenas call it a day.

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The weeks pass,

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and the calf is stronger and fitter
than he has ever been.

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But soon he must leave this
grassland paradise and travel south,

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back into Tanzania.

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He has survived the Mara's minefield
of predators unscathed

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but soon, he'll have
to cross the river again.

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His next challenge
is quite unexpected.

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Hippo-cam is spying on one
of the many hippo pods

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found along the length
of the river.

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The hippo seem to accept the strange
family member in their midst.

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Unfortunately for the hippos,
they live at the place

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where wildebeest traditionally
cross the river.

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The herds are already massing
on the banks.

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Motivated by a common urge, the
individual herds have joined forces

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to form a giant army,
several thousand strong.

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For the calf,
so much is still unfamiliar.

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Hippos are noisy and intimidating,

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especially when their
youngsters are play-fighting.

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Undeterred,
the wildebeest push forward.

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The mother and calf get their first
close look at the problem.

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But this blockade must be more
than any of them bargained for.

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Hippos are notoriously unpredictable

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and this pod
has a new and boisterous baby.

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Even the Thompson gazelles
seem more nervous than usual.

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For the calf, the excitement
seems dangerously infectious.

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Luckily, he has second thoughts.

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00:30:10,300 --> 00:30:14,540
But this was just the
encouragement the gazelles needed.

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Once they seem confident,
the wildebeest are reassured.

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The hippos' peace is shattered.

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They don't like
having their space invaded.

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The calf's turn arrives.

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He takes the plunge,
along with his mother.

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00:31:10,220 --> 00:31:13,020
The hippos are vanishing fast.

204
00:31:22,300 --> 00:31:26,580
They may be out of sight
but they shouldn't be out of mind.

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Their mood hasn't improved one bit.

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They discharge dung into the water.

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Like hidden depth charges,
their eruptions break the surface.

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The swimmers
steer a course around them.

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00:32:46,860 --> 00:32:51,940
The front-runners reach the shore,
pursued by an angry bull hippo.

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00:32:54,740 --> 00:32:58,340
Another hippo even makes a grab
at one of the swimmers.

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But it escapes.

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In the turmoil, the calf
has got himself into trouble.

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00:33:07,380 --> 00:33:11,420
He's been separated from his mother
and is being carried downstream.

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00:33:23,020 --> 00:33:26,380
The hippo's anger hasn't subsided.

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00:33:30,340 --> 00:33:34,740
The calf is nearly exhausted
but worse is to come.

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00:33:34,740 --> 00:33:36,620
This is unusual behaviour.

217
00:33:36,620 --> 00:33:39,860
Hippos are supposed to
munch grass, not meat.

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00:33:44,780 --> 00:33:47,820
But the hippo doesn't attack.

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Crocodiles aren't so merciful.

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00:34:10,940 --> 00:34:15,020
But the calf had a good head start.

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He may have survived
but now he's on his own.

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Wildebeest are disappearing
away on the opposite bank.

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The calf is separated and alone.

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There is only one way out
and he finds it.

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He's back where he started
and he has no-one to protect him.

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A band of foraging mongooses
looks on curiously.

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Hating to be alone, lost calves
will join any herd they come across.

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Others have the same idea.

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This impala fawn
has also lost her mother.

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Like the wildebeest calf,
she's desperate for company.

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The young impala calls,
but the calf ignores her.

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00:36:31,140 --> 00:36:34,860
But then something
remarkable happens -

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the meeting of two lost souls.

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The calf is curious.

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00:36:53,660 --> 00:36:56,260
The fawn seems to think
he's her mother.

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Then, the fawn hears a familiar
call - his real mother returns.

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This is normal behaviour.

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00:37:24,580 --> 00:37:28,900
Impala deliberately leave
their camouflaged young unattended

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when they move away to graze.

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Wildebeest calves are conspicuous

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00:37:33,300 --> 00:37:37,620
and need to stay with the herd to
avoid being targeted by predators.

242
00:37:44,460 --> 00:37:48,180
The herd also shares sentry duties.

243
00:37:48,180 --> 00:37:51,140
Alone,
it's easy to run into trouble.

244
00:37:54,420 --> 00:37:59,460
This mother cheetah and her
large cub are taken by surprise.

245
00:38:08,140 --> 00:38:10,380
The calf takes the prudent option

246
00:38:10,380 --> 00:38:13,900
but one that proves irresistible
to the cheetahs.

247
00:38:26,580 --> 00:38:29,180
He can now run like the wind.

248
00:38:29,180 --> 00:38:31,980
The cheetahs are too slow
off the mark

249
00:38:31,980 --> 00:38:35,220
to catch up
with this 45-mile-an-hour sprint.

250
00:38:38,700 --> 00:38:42,940
Across the river, the wildebeest
masses haven't gone far.

251
00:38:46,220 --> 00:38:50,740
The mother returns
looking for her lost calf.

252
00:38:58,580 --> 00:39:02,020
She hesitates.

253
00:39:02,020 --> 00:39:05,260
Then she makes a brave decision.

254
00:39:13,820 --> 00:39:16,540
She crosses back to the other side.

255
00:39:58,140 --> 00:40:01,380
Crossing alone
has the advantage of surprise.

256
00:40:01,380 --> 00:40:04,580
The crocodiles
had little time to prepare.

257
00:40:14,900 --> 00:40:17,740
The cheetahs seem game
to chase anything,

258
00:40:17,740 --> 00:40:21,020
even though the mother
is far too large for them.

259
00:40:26,580 --> 00:40:29,940
The calf hears her call.

260
00:40:35,860 --> 00:40:39,540
Once more, the two are together.

261
00:40:47,260 --> 00:40:48,980
Another herd appears.

262
00:40:52,780 --> 00:40:57,380
Adult wildebeest show no
particular attachment to each other,

263
00:40:57,380 --> 00:41:02,540
so mothers and calves are instantly
accepted into any new group.

264
00:41:17,340 --> 00:41:22,020
At one-year-old, the cheetah's cub
is able to hunt on her own,

265
00:41:22,020 --> 00:41:24,940
but she still enjoys
playing with Mum.

266
00:41:29,740 --> 00:41:32,220
The calf likes
his playful moments too.

267
00:42:22,540 --> 00:42:25,980
Play is good practice for hunting.

268
00:42:25,980 --> 00:42:28,820
The mood can change very quickly.

269
00:42:31,460 --> 00:42:34,580
Nearby are the mother and her cub.

270
00:42:34,580 --> 00:42:37,740
The Mara supports a lot of cheetahs!

271
00:42:44,700 --> 00:42:46,980
The others spot them.

272
00:42:53,420 --> 00:42:55,260
The tiny cub is vulnerable

273
00:42:55,260 --> 00:42:58,660
and the pair are acting
as if they've seen prey.

274
00:43:04,780 --> 00:43:06,580
The cub is nervous.

275
00:43:06,580 --> 00:43:10,340
Such encounters are rare and it's
difficult to predict the outcome.

276
00:43:30,180 --> 00:43:32,220
The mother sounds a warning.

277
00:43:36,260 --> 00:43:39,460
She yelps in distress.

278
00:43:42,980 --> 00:43:45,580
The cub runs for his life.

279
00:43:57,820 --> 00:44:02,260
It's a stand-off
as the cub's fate is decided.

280
00:44:02,260 --> 00:44:06,340
Neither seems to know
quite what to do.

281
00:44:09,780 --> 00:44:11,780
A reprieve.

282
00:44:15,500 --> 00:44:19,100
It may be that these cheetahs
are related, so the competition

283
00:44:19,100 --> 00:44:22,460
from the new arrival
is something they can tolerate.

284
00:44:24,540 --> 00:44:28,660
Anyway,
the encounter is soon forgotten.

285
00:44:36,140 --> 00:44:37,540
The calf and his mother

286
00:44:37,540 --> 00:44:40,860
have settled back into the herd
still left on the Mara.

287
00:44:40,860 --> 00:44:45,340
Migration happens in waves
over a period of several weeks.

288
00:44:45,340 --> 00:44:48,580
For those yet to leave,
there's still plenty to eat.

289
00:45:18,420 --> 00:45:20,460
Because of the rich pasture,

290
00:45:20,460 --> 00:45:24,140
around half a million wildebeest
enter the Mara

291
00:45:24,140 --> 00:45:26,140
at some point on their journey.

292
00:45:26,140 --> 00:45:28,460
Back in the midst of the herd,

293
00:45:28,460 --> 00:45:32,740
the calf relies on safety
of numbers for protection.

294
00:45:34,860 --> 00:45:37,620
Predators make daily assaults.

295
00:45:37,620 --> 00:45:40,540
Their days of easy hunting
will soon be over.

296
00:45:46,300 --> 00:45:51,740
As many as six lionesses may work
together, staging these attacks.

297
00:46:03,620 --> 00:46:07,900
While the grass is long,
it's easy to surround the herd.

298
00:46:19,780 --> 00:46:23,900
The lion that has stalked closest
initiates the charge.

299
00:46:30,540 --> 00:46:33,980
One misses,
but the others still have a chance.

300
00:46:40,900 --> 00:46:42,540
She's got one.

301
00:46:42,540 --> 00:46:44,980
It's a zebra.

302
00:46:44,980 --> 00:46:49,020
Lions seem to prefer them
to any other prey.

303
00:46:56,340 --> 00:47:02,460
The productivity of the Mara
depends on frequent downpours.

304
00:47:02,460 --> 00:47:06,660
The mother and calf
turn their back on the driving rain.

305
00:47:08,260 --> 00:47:12,740
The whole vast herd
stands motionless, like statues.

306
00:47:42,260 --> 00:47:46,700
The cub copes with the deluge
in his own way.

307
00:47:55,700 --> 00:47:58,820
Although the rain
refreshes the grass,

308
00:47:58,820 --> 00:48:01,340
it also triggers mass movement.

309
00:48:01,340 --> 00:48:04,180
The herds are leaving the Mara.

310
00:48:17,380 --> 00:48:20,900
They mass once more
on the banks above the river.

311
00:48:26,180 --> 00:48:31,180
They have arrived at the most
forbidding crossing point
in the Mara.

312
00:48:54,060 --> 00:48:57,100
Opposite them
is a sheer vertical wall

313
00:48:57,100 --> 00:49:00,860
and the water below
is patrolled by crocodiles.

314
00:49:11,020 --> 00:49:14,300
There are few more difficult
crossing points on the river,

315
00:49:14,300 --> 00:49:16,500
but year after year,

316
00:49:16,500 --> 00:49:20,980
the wildebeest choose this place as
their final gateway from the Mara.

317
00:49:26,260 --> 00:49:29,900
A gazelle is the first
to attempt the challenge.

318
00:49:35,300 --> 00:49:38,660
She reaches the notorious wall

319
00:49:40,860 --> 00:49:43,060
but pays the price.

320
00:49:55,940 --> 00:49:59,780
Zebra are the next
to try their luck.

321
00:49:59,780 --> 00:50:03,340
And wherever they go,
the wildebeest are quick to follow.

322
00:50:14,420 --> 00:50:18,060
Once the crossing is underway,

323
00:50:18,060 --> 00:50:22,300
the herd's impulse to join in
is almost suicidal.

324
00:50:24,780 --> 00:50:29,620
The urge to migrate is so strong,
nothing quenches it.

325
00:50:31,660 --> 00:50:37,140
Mother and calf once again
wait their turn to join the mayhem.

326
00:50:41,660 --> 00:50:45,260
The mother leaps, the calf follows.

327
00:50:58,660 --> 00:51:01,500
The calf is now a strong swimmer,

328
00:51:03,420 --> 00:51:07,980
but hundreds of wildebeest
are putting pressure from behind.

329
00:51:20,220 --> 00:51:24,860
In front stands
the sheer 20-foot wall

330
00:51:24,860 --> 00:51:26,900
and still they keep coming.

331
00:51:46,980 --> 00:51:52,300
For the calf,
there is no turning back.

332
00:51:52,300 --> 00:51:56,140
The zebra are the first
to meet the dangers.

333
00:52:01,660 --> 00:52:04,460
They're the favourite
food of crocodiles

334
00:52:04,460 --> 00:52:06,660
but their kick can be crippling.

335
00:52:19,740 --> 00:52:24,740
Mother and calf
approach the danger zone.

336
00:52:24,740 --> 00:52:28,020
The crocodile finds
a zebra foal instead.

337
00:52:35,300 --> 00:52:39,020
But many more crocodiles
lurk beneath the surface.

338
00:52:46,500 --> 00:52:49,340
The calf is singled out.

339
00:52:58,700 --> 00:53:00,940
Missed!

340
00:53:06,500 --> 00:53:09,140
But the danger is not over.

341
00:53:09,140 --> 00:53:12,540
The calf and mother
have reached the wall.

342
00:53:14,060 --> 00:53:17,260
The build-up
from behind is relentless.

343
00:53:21,100 --> 00:53:24,300
And crocodiles
prepare to pick off stragglers.

344
00:53:43,420 --> 00:53:47,260
The calf
tries to climb the vertical wall.

345
00:53:51,580 --> 00:53:53,740
Others fall.

346
00:53:57,420 --> 00:53:58,860
He follows.

347
00:54:04,260 --> 00:54:07,380
The crocodile tries again

348
00:54:07,380 --> 00:54:10,820
but the calf
is a fast-moving target.

349
00:54:14,100 --> 00:54:17,300
He gradually works his way
along the wall.

350
00:54:27,260 --> 00:54:31,660
Yet more wildebeest are arriving.

351
00:54:35,420 --> 00:54:39,420
They use each others' bodies
as steps.

352
00:54:53,860 --> 00:54:56,300
And still they keep coming.

353
00:54:59,660 --> 00:55:04,860
The calf is being pushed
further along the wall.

354
00:55:13,780 --> 00:55:18,260
Then, suddenly, the pressure eases.

355
00:55:18,260 --> 00:55:20,700
The bottleneck has an opening.

356
00:55:22,940 --> 00:55:24,860
The calf finds it.

357
00:55:30,260 --> 00:55:34,300
The pressure
at this one exit is now intense.

358
00:55:38,380 --> 00:55:43,860
The calf and mother make it
to the top but the edge is slippery.

359
00:55:51,260 --> 00:55:55,620
The mother tries again,
so does the calf.

360
00:55:55,620 --> 00:55:58,140
So near yet so far.

361
00:55:59,860 --> 00:56:03,140
The calf slips.

362
00:56:03,140 --> 00:56:05,860
He struggles to get up.

363
00:56:16,140 --> 00:56:18,580
He finds his feet...

364
00:56:23,500 --> 00:56:26,620
..and manages to reach the top.

365
00:56:26,620 --> 00:56:28,300
His mother is there to greet him.

366
00:56:42,940 --> 00:56:45,340
Mother and calf have survived

367
00:56:45,340 --> 00:56:48,820
some of the most challenging
tests in nature.

368
00:56:50,580 --> 00:56:52,620
They will now travel south,

369
00:56:52,620 --> 00:56:56,340
back to the short-grass plains
of the Serengeti.

370
00:56:58,180 --> 00:57:01,460
It was here that the calf was born

371
00:57:01,460 --> 00:57:04,580
and it was here
that our story began.

372
00:57:10,220 --> 00:57:15,100
And, on these plains,
another generation will be born.

373
00:57:15,100 --> 00:57:18,940
They too are destined
to make the same epic journey,

374
00:57:18,940 --> 00:57:22,020
one that has been made
for a million years.

375
00:57:22,020 --> 00:57:25,980
Undoubtedly, the greatest
natural trek on earth.

376
00:57:25,980 --> 00:57:28,020
Subtitles by Red Bee Media Ltd