All language subtitles for Coastal Africa - 01x02 - Sanctuary of the Indian Ocean Eng

In a vast ocean...

along a wild continent.

An incredible place
of sanctuary.

These pristine beaches,
the tidal forests

and the most southerly submerged
reef are a hotspot of diversity.

A crowded home
to thousands of species,

where some inhabitants
work together...

and others are solitary hunters.

And for two of the ocean's
nomadic giants,

this coast is the key to
the survival of their species.

This is the Indian
Ocean's secret refuge.

This is Africa's
ocean sanctuary.

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Spanning two hemispheres
and touching three continents,

The Indian Ocean covers over
28 million square miles.

Here, off the east coast
of Southern Africa,

it washes up against
a shoreline

of subtropical bush
and golden beaches.

A lush, abundant landscape.

Where mangrove forests and dune
fields meet an inviting ocean.

With a climate created
by the warm Agulhas current,

its warm waters are a sanctuary
for a diverse collection

of marine species.

And yet, the apparent abundance
of this world is deceptive.

This African shoreline
is gentle and warm,

but life here
is a relative struggle

compared to that
enjoyed by species

just six hundred miles
down the coast,

where these azure waters
give way

to the violent Atlantic washing
up on a semi-desert world.

Southern Africa's Atlantic coast
is pounded by huge surf

whipped up by constant winds.

But those winds also draw water
up from the depths,

bringing with it
vast amounts of nutrients

from a millennia of
decomposing plant matter.

This bonanza of food
supports massive populations

of marine species
on the west coast -

over two million Cape fur seals
jostle for space

in large breeding colonies.

They are fed by enormous shoals
of pelagic fish such as sardines

that are drawn here by the cold,
nutrient-rich water.

But along the east coast,

the prevailing winds
are gentler.

Without the battering gales,

there is no upwelling of
nutrients from the depths.

The water might be warm
and tranquil,

but it doesn't have the benefit
of the west coast's

endless conveyor belt of food
brought up from the deep.

What it does have, though,
is coral:

a living landscape thriving
on a symbiotic relationship

between coral polyps
and single-celled algae.

As the algae photosynthesize and
give off oxygen for the polyps,

and the polyps give off carbon
dioxide for the algae,

they create
a solar-powered oasis,

offering food and shelter
for the creatures

that are drawn here.

It's a vibrant concentration
of life,

a safe zone created
by a unique confluence

of geography and climate;

where Africa's marine animals
gather together

to form a vibrant community

in one of the last great
wilderness strongholds.

Out in the open ocean, some
of this region's great migrants

are ending long journeys.

Drawn to the warm waters and
relative safety of the coast,

turtles and Ragged-tooth sharks

make an annual journey
to gestate.

This Ragged-tooth shark
is pregnant.

She has come to these waters to
bring her pups closer to term.

The Hawksbill turtle, too,
is returning to these waters,

but her nesting grounds
are further up

the African coast
in Mozambique.

She knows these waters well.

She has travelled this way
every two years

since she was old
enough to breed.

Now she is gathering her
strength for the last leg

of our journey.

It's been a long trek.

One young Hawksbill was found to
have swum from the Cocos Islands

southwest of Sumatra
to Tanzania -

a journey of 3,800 miles.

She's not alone.

Somewhere out beyond the reef,
other female turtles

are reaching the end
of their own epic journeys.

Now, though,
she's focused on her meal.

She's tired.

The current is powerful.

But it's worth persevering.

The reef hides her favorite meal
- soft sponges.

The coral reef is built
on ancient foundations.

Millions of years ago, sand
dunes on a prehistoric beach

solidified into something
like sandstone.

Slowly swallowed up
by the ocean,

they became the bedrock
upon which this coral reef grew.

Coral is a living creature,

a soft-bodied organism

that attaches to bedrock
and grows,

creating hard
calcium carbonate tubes.

Colonies are formed,
creating reefs

and in turn,
entire habitats.

They grow slowly -

just four inches per year -

but when they are left
undisturbed for millennia,

their colonies can build up into
entire landscapes like this one.

This is the southernmost
submerged reef

along the African coast.

It's also deep.

Its shallowest outcrop is still
33 feet below the surface.

The deeper the reef, the less
sunlight reaches the algae

on which it depends.

And yet,
enough filters down here

to make this one of the most
diverse ecosystems

on the planet.

The location of the reef
might seem arbitrary:

these corals could have settled
on any rocky outcrop

anywhere along the hundreds
of miles of this shore.

And yet, it owes its success
as a center of diversity

to a quirk of geography
that makes it part

of a uniquely interlocking
ecosystem.

Just beyond the dunes, an
estuary winds towards the sea.

At the head
of its mysterious waterways

lies a forest unlike
any other along this shore.

A mangrove forest,

able to survive
in the salt water

that floods it
with every high tide.

Every day, this unique forest
drops tons of plant matter

into the waterlogged mud
around its roots.

Much of that waste
is dragged underground

by the mangrove's
composter-in-chief,

the Red-claw mangrove crab.

Alerted by the soft vibrations
of an impact on the mud,

these tireless recyclers keep
the forest floor clean -

and keep the entire estuary
system flooded with nutrients.

Tons of pods and leaves
quickly become tons of compost.

As the tide comes in, flooding
the forest with salt water,

the water fills
with dissolved nutrients.

When it retreats, all of that
food is washed out into the sea,

bringing a feast to the filter
feeders of the nearby reef.

The ebb and flow of the tides
in the mangrove forest

keeps the reef well fed.

But it provides more than food
to the fish of this coast.

It also provides a nursery.

At high tide,
an unbroken passage

stretches from ocean to forest.

Now these beaches are no longer
a barrier between worlds,

as channels open
for new visitors.

A waterway deep
into the mangrove forest

is an invitation
to the reef's baby fish.

Young reef fish have
evolved to follow

the incoming tide upstream.

The journey from coral to coast
is a long one for a small fish,

but it's worth the effort.

Submerged mangrove roots:

the fish have reached
the outskirts of the forest,

where salt- and fresh water
are mingling.

Pulled together by the promise
of the mangroves,

a new community forms.

An underwater nursery
for young fish.

They come in the thousands.

The mangroves are a sanctuary,

offering a few vital months
of abundant food

and safety from
the reef's predators.

Here the fish will mature,
growing bigger and stronger

until they're ready
to take on the challenges

of the open ocean.

For a world
struggling for sustenance,

the nutrient-rich
water of the forest is a bonanza

and its effects are dramatic:

tropical fish species
have been found to be

up to twice as abundant

on reefs bordering mangroves
on this coast.

But not all of
the reef's inhabitants

have access
to a convenient nursery.

They cannot disappear
for a few months

until they are ready
to compete.

Instead, they disappear right
where they are - in plain sight.

On an exposed reef
offering few places to hide,

the art of camouflage becomes
a vital weapon

in the battle for survival.

Indistinguishable
from the textured backdrop

of the rocks and coral,

a predator waits for a catch.

The Frogfish is a type
of Anglerfish,

using a lure attached to its
head to attract hungry victims.

It's easy to miss him.

His unique skin makes him
a master of disguise.

Instead of scales, Frogfish
are covered with fleshy spines,

hairy extensions
and tiny skin flaps

to blur any recognizable
features.

All the better to be mistaken

for a piece of
algae-covered sponge.

Since his camouflage depends
on him being motionless,

the Frogfish doesn't move much.

When he does, he reveals
a unique waddling walk,

as he makes his way
along the seabed

using his jointed pelvic fins.

He's not a strong swimmer,

but these feet-like fins

brace him against the current
as he waddles across the reef.

When he finds
his next hiding place,

he will settle down
and become invisible

against the rock, biding his
time until his next meal.

He's not the only undetectable
hunter lying in wait.

The Crocodile fish is
intricately marked and textured,

and pressed against the reef,
it all but disappears.

Even its eyes are camouflaged.

All is not what
it seems on this reef.

To unsuspecting passersby
this may look like

just another dead
leaf waving in the current.

But this dead leaf
is very much alive.

Paper fish snap up any small,
unsuspecting fish

and crustaceans
that venture too close.

Most of these predators
are prey as well.

Camouflage not only allows them
to ambush their prey,

but it also hides them from
the animals that prey on them.

For some,
it's not about being invisible.

Instead, it's about looking
like the fish next to you.

This cloud of yellow fish
is made up of several

similar-looking species.

Most of them
are Blue banded snapper,

but mixed in among them

are a number of
Yellow stripe goatfish.

For both the snapper
and the goatfish,

there's safety in numbers.

The more similar-looking
the fish in the group,

the better the odds to survive
an attack by a predator.

Shoaling increases
the chance of survival

for each individual fish.

More eyes means
more surveillance

on potential threats.

Should they be attacked,

the swirling mass
of yellow bodies

might disorientate
or distract a predator,

making individual fish
less likely to be picked out.

It's a relationship that
benefits both species.

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But one famous fish has taken
interspecies co-operation

to an extreme level -

happily living in a death-trap.

Clownfish find safety among
the fronds of sea anemones.

It seems like
an unlikely refuge.

The anemone's stinging nettles
make a meal

of anything small and unwary
enough to venture close.

But for the Clownfish,
the tentacles aren't killers -

they're home.

It's a unique "exchange
of services" arrangement.

While the anemone provides
shelter, food and protection

for its little keeper,
the Clownfish returns the favor

by keeping its
home clean and healthy.

The Clownfish are able
to survive the stings,

thanks to a life-saving layer
of mucus that covers their body.

This mucus is up to
four times thicker

than that produced
by other fish.

More importantly, it's laced

with traces of
the anemone's own venom.

Each anemone
houses its own Clownfish

and it is believed that
the fish tailor-makes

its own specific anti-venom
by rubbing against the anemone -

literally taking the sting
out of these nettles.

This death-defying performance
has an audience:

a group of baby
Domino damsel-fish.

These territorial animals
are also able

to withstand anemone stings;

they've been using this one
as a hideout.

But while the bigger Clownfish
is having a turn,

they keep a
respectful distance.

Turtles are the great nomads
of the planet's oceans.

Covering huge distances
to feed or to breed,

they spend most of
their lives away from land.

Africa's Indian Ocean coast
is 4,000 miles long,

spanning five countries
and two hemispheres.

And yet when they migrate here,

they are heading for one special
place on one specific beach.

The place where they were born.

The females know exactly
where they need to go.

Turtles are highly sensitive
to the Earth's magnetic field.

They use it to navigate
in the open ocean,

following tiny
fluctuations or gradients

as if they were lines on a map.

This beach, too,
has its own magnetic markers,

like invisible
GPS co-ordinates.

But this female Hawksbill
will swim on.

Her inner compass
is directing her to a beach

far north of here.

She knows exactly where
she will find it:

the beach's co-ordinates
were imprinted on her

when she was born.

The beaches of this African
sanctuary, however,

are calling to other turtles.

They were born here,
many years ago

and are now returning
to complete an ancient cycle.

This Loggerhead female has
followed her magnetic signal

back to the beach
where she was born.

This moment has been
a long time coming.

It can take up to 35 years
for Loggerheads

to reach breeding age.

Now ready to lay, she begins
to excavate her nest.

Up here, above the high-water
mark,

her eggs will be safe.

Her babies will have
a fighting chance.

The sex of baby turtles
is heavily influenced

by the temperature in the nest.

In warmer nests, most embryos
develop into females.

Cooler clutches are more likely
to produce males.

Nearby, another long-distance
nomad is also nesting.

A female Leatherback has dragged
herself ashore,

hauling her huge
weight up the dunes.

These massive turtles can grow
to be over six feet long

and weigh almost a ton.

Her migrations are vast -

sometimes over 4,300 miles
each way -

and she can reach depths
of almost 4,000 feet

down into the abyss.

But none of her journeys
have been as important

as this short one
from the surf to the dunes,

to lay her hundred eggs
and start a new generation

of ocean wanderers.

The Loggerhead female
has laid her eggs

and covered up her nest.

Exhausted by
the night's exertion,

she drags herself back
towards the surf.

But she's not alone.

Out in the night,
eyes are watching.

Ghost crabs.

The mortal enemy of her babies.

But for tonight,
her work is done.

She will return to this beach
three or four more times

in the coming weeks
to lay more eggs in new nests.

But the hatchlings will
have to fend for themselves.

As silently and secretly as she
arrived, she slips out of sight.

A new day
and under coral overhangs

away from strong currents,

fish are gathering to get
a much-needed clean-up

from one of this reef's most
industrious workers:

the Cleaner shrimp.

This is a safe place,
where predators and prey alike

put aside their differences
in the quest

for the perfect
full-body treatment.

For the weary and worn,
it's a welcome relief

to get rid of parasites
and damaged skin.

For the team
it means a hearty meal.

Waving their white legs
and antennae,

the shrimp flag down
interested customers.

The usually dangerous Rock cod
are not here to cause trouble,

and move in slowly to show
they mean no harm,

changing colors
and gently opening their mouths.

A Cleaner leaps to work.

A stingray approaches
hoping to secure a slot.

Like the Rock cod,
she too comes

waving the proverbial
white flag.

She lifts her body off the sand
with undulating movements.

But she's come too late.

The shrimps are busy now
and like it or not

she'll have to
come back later to try again.

The Cleaner shrimp's cousin,
the Harlequin shrimp,

has more refined tastes.

Not for these refined diners
is scraping together meals

consisting of dead skin and
scraps stuck between teeth.

They are hunters.

And today's target is their
favorite delicacy: starfish.

They're dressed for dinner,
suited up in magnificent shells.

They can afford to be showy,

since their prey will not be
able to escape them.

Starfish have hundreds of
tubular feet that allow them

to move smoothly, but slowly,
across the ocean floor.

A slow-moving target
is an easy target

and some starfish have
developed hard bodies

to protect themselves

But not this one.

The Harlequin shrimp have used
their delicate sensory antenna

to smell out their prey.

Now, they climb on top of it
and get to work

trying to turn it over.

If they are going to get
to its vulnerable underbelly,

they need to immobilize it.

And then,
with chilling precision,

they will set about
slicing off its tender feet

with their specialized claws,

working slowly towards to the
starfish's juicy central body.

The starfish will feed these
meticulous killers for days.

Elsewhere on the reef,
other predators

are starting their day,

or recovering
from the night's hunt.

A Leopard shark has spent
the night prowling the reef,

stalking crabs and shrimp.

They are small morsels,
but they are abundant.

With enough food,
these placid sharks

can grow up to six feet long.

Tired after the night's hunt,
it rests on the sandy bottom,

keeping exertion to a minimum.

Sharks have ancient origins,

going back hundreds
of millions of years,

but next to these
silent hunters,

drifting over the reef,
they are relative newcomers.

The first jellyfish floated
through the world's oceans

500 million years ago,

long before there were even
plants on land.

They are the oldest
multi-organ animal on Earth.

But they are not quite
as primitive as they seem.

Instead of being passive
drifters,

they move by contracting
the rims of their bells

in subtle pulsing movements
that displaces the water

they're moving through.

They also have
a complex nervous system

that helps them adapt and
react to the environment,

sensing current flows,

identifying other jellyfish,

and even testing the salinity
of seawater.

The bodies of jellyfish
are soft and fragile,

but they can be lethal.

When they encounter their prey,

they react with
overwhelming force,

pumping their victim
full of neurotoxins.

Most animals in this ocean
give them a wide berth,

but for turtles,
they're a staple diet.

Leatherbacks gorge on jellyfish
in the open ocean,

in summer sometimes eating
up to 70% of their body weight

every day.

This predator chooses
to stay close to the reef

rather than roam the open ocean
like the jellyfish.

The Honeycomb moray eel coils
itself in and among the crevices

of the reef, venturing out
occasionally for a stop

at the cleaning station
or to hunt.

Often mistaken
for a of type sea-snake,

the moray is actually a fish.

Its open mouth looks
intimidating,

but this is less a show of force
than simple respiration.

An open mouth allows a constant
stream of water

to flow through
its gills -

little holes
situated behind its head.

They may look frightening
and anti-social,

but eels are relatively
peaceful neighbors -

when they're well fed.

Where nooks and crannies are
scarce on the reef,

they might even live
side by side with other eels:

a fearsome-looking pair

that is just trying to get by
like everyone else.

These fish can swim close
to the eels' open mouths

with little to fear...

until feeding time.

Another ancient creature
of the ocean

has made her way
to the coast.

Female Ragged-tooth sharks

migrate to these warm waters
to gestate.

They are extremely sensitive to
temperature changes

and will move along the
coastline to warmer waters

when they are carrying young.

She has two wombs
and will produce eggs

as long as she's gestating.

She will give birth to two pups
- one from each womb.

Most of her energy is going into
growing her pups.

And yet during this time
she eats very little.

Algae on her mouth and teeth
is testament to her fast.

Almost nothing has passed
through these jaws for weeks.

But just because
she's not eating,

it doesn't mean her pups
are going hungry.

The unborn sharks
are building their strength -

by eating their siblings.

The biggest pups eat their
weaker brothers and sisters -

inside their mother's body.

First the embryos
and then any unfertilized eggs

in their reach.

The extra eggs are a vital
source of baby food.

As their mother cruises
in the warm water,

her unborn pups have
already learnt

their first lesson in life:

only the strongest survive.

She will spend two months here
in this sanctuary,

but as the time comes
for her to give birth,

she will swim south
toward cooler waters.

It will take up to 9 months
for them to be born.

When they enter the world, her
pups will be up to 3 feet long

- half her size - and already
formidable predators.

But for now they are growing.

Two months have passed

since the Loggerhead
laid her eggs on this beach.

Up above the high-water mark,
the dunes are stirring.

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The first of the brood
makes its way out of the nest.

Instinct tells the rest
to stay motionless for now,

but this one is precocious.

It's a bad move.

Dangers lurk in the darkness.

Ghost crabs are waiting
at the water's edge,

gathering for the kill.

These opportunists are
one of the key predators

of baby turtles.

If the babies are going to reach
the safety of the ocean,

they will have to
avoid being caught.

The rest are staying put.

There is safety in numbers.

But their impatient
sibling is on his way.

Out in the open, alone,
there is nowhere to hide.

A crab closes in
for the easy kill.

Unaware of the tragedy
on the beach,

the rest of the brood
is surfacing.

Up to 120 babies are pushing up
out of the nest,

all intent on one,
all-important dash

down the dunes
and across the beach.

For the tiny, soft,
awkward babies,

not made for moving on land,

it will be
a monumental struggle.

Even small dune plants
present major obstacles.

The journey is just
a few dozen yards,

but for the hatchlings
it's an exhausting trek

across an apparently
endless desert.

A desert full of dangers.

A life-and-death struggle.

A baby has been snared
by a ghost crab under the sand.

The unlucky do not survive,
but this baby is tough.

It battles on through the night,

rejoining its brothers and
sisters as the march goes on.

This is the first and last time
the males will walk on land.

The rest of their lives
will be spent at sea.

At last, they reach
the water's edge.

They are together for now,

but they are starting
solitary lives.

Turtles are self-sufficient
from the moment they hatch

and already they are going their
separate ways,

beginning decades of wandering
across the world's seas.

The magnetic signature
of this beach

has already imprinted
on them

and one day, twenty or thirty
years from now,

the females will begin to return
here to lay their own eggs.

Now, they will let the currents
guide them.

The warm Mozambique current
will take them south,

skirting the African continent

and then out
into the Southern Ocean.

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A new day over the reefs
of Southern Africa.

The baby turtles are gone.

The secret ritual of the night
before has passed

as mysteriously as it started.

But life on the reef goes on,
as urgently as always.

There are fish to be scrubbed.

Dangers to be avoided.

The daily work of survival
in the Indian Ocean.

The Raggies will linger here
for many weeks more,

drifting in these warm waters
as their pups reach full term.

And then they too
will leave this coast,

to swim south to give birth.

Another migration in an ocean
full of ancient nomads.

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Life in the Indian Ocean
might be challenging,

but here, off the coast
of Southern Africa,

it flourishes in a natural
sanctuary like no other.

A protected area,
made abundant by the interplay

between subtropical reef
and life-giving mangroves.

From its sweeping beaches
to its coral landscapes...

safe nurseries...

to secret nesting sites.

This is a place
that offers shelter

and abundance to those
that throng here.

Whether they call it home,
or are just passing through.

A hideaway.

A stronghold.

An island of diversity
in the great Indian Ocean.

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