All language subtitles for BBC.Natures.Microworlds.09of13.Namib.Desert.720p.HDTV.x264.AAC.MVGroup.org Eng

Our planet is the greatest
living puzzle in the universe.

A collection of worlds
within worlds.

Each one, a self-contained ecosystem

bursting with life.

But how do they work?

The intricate web of relationships

and the influence of natural forces

makes each microworld
complex and unique.

So, to discover their secrets,

we need to explore them one by one.

Untangle their interlocking pieces

and, ultimately,
reveal the vital piece,

the key to life itself,

hidden deep within

each of nature's microworlds.

Running down Africa's south-west
flank lies the Namib Desert.

2,000 kilometres long

and 200 kilometres wide,

this is not Africa's largest desert,

but it is its oldest.

Created by an 80-million-year feud

between the African coastline

and the full force
of the Atlantic Ocean,

it's a startling place.

The rugged coast and its sea
of dunes is the stuff of legend.

The wrecks of ships swamped by sand

show how treacherous this place is,

blinded by the regular sea fogs,

dashed on the rocks
by the pounding ocean.

Even though it's been
shaped by brutal forces,

the Namib is one of the greatest
natural wonders on Earth -

but it's not for the faint-hearted.

And that's because the Namib
seems to be missing

one of the fundamental
building blocks of life -

water.

Some years, it doesn't rain at all.

So it would take some truly
hardy creatures

to be able to survive
in this barren, waterless place.

In fact, the only thing more
extraordinary than the landscape

are the surprising creatures
that call it home.

Sea lions sprawling in desert sands.

A chameleon, normally a tree
dweller, but with no tree in sight.

And a blind mole

with no soil in which to dig.

In fact, the Namib is home

to over 180 species

found nowhere else on Earth.

To understand how
this ecosystem works,

we're going to first
have to understand

how life succeeds here at all.

We must take a closer look
at these creatures,

explore their unique adaptations,

understand their interactions,

so that we can discover the secret

that allows life to tough it out

in the most inhospitable desert
on Earth.

Let's start at the edge
of the desert - the coast.

The freezing Antarctic waters
are the key to the success

of one particular coastal species.

Where hot desert sands
meet these icy waters,

the South African fur seal reigns,

in giant colonies

several thousand strong.

The cold currents flowing northward
from Antarctica

bring with them deep, rich waters,

which, in contrast to the desert,

are teeming with life.

Seawater is far too salty to drink,

so fish provide the fur seals

with both food and water.

This saves them
from the dryness of the desert.

But they are not immune to something
else this desert has a lot of...

..heat.

They may be perfectly adapted
for hunting in the breakers,

but they can't spend
all their life at sea.

They have to come to shore
to rest and to breed.

Out of the water,
the seals are vulnerable.

The blubber that keeps them
warm in the cold water

is now more of a hindrance
than a help.

SEAL GROANS

But the seals have developed
a behaviour to combat overheating.

Flipper sailing.

Their flippers are the only part
of their bodies

not covered by blubber and fur

and so, by exposing them
to the breeze, they can lose heat.

And, of course, if it gets
too hot to bear,

like holiday makers,

the adults make a dash
for the cold water to cool off.

But they have to come ashore
to give birth

and their pups are too young
to swim.

The effects of extreme
heat can be lethal.

One in four fur seal pups

just won't make it.

But then, why with
such a high death rate,

are the seals here
in the first place?

The lethal heat and wind
that helped create the dunes

act as an impassable barrier,

protecting them
from the rest of Africa,

with all its deadly predators.

So the desert acts
like a defensive wall,

and the loss of a few pups
is a small price to pay

for the success of the whole colony.

But they're not completely isolated.

Black-backed jackals
are one of the few animals

that have managed
to reach the coast.

And now, they are heavily dependent
on the seal colonies for survival.

A mutually beneficial
relationship's developed

between these beach dwellers.

The dogs are not capable
of taking healthy pups,

but, by scavenging
on the dead and dying,

they clean up the colony,
preventing the spread of disease.

It's a practical, if not a little
morbid, arrangement.

But with the beach
littered with pups,

the difference between
the sick and the sleeping

is sometimes hard to spot.

PUP SQUEALS

Jackals are adapted to desert life,

having kidneys designed
to handle water deprivation.

But, without the seal
feast on the beach,

even they would struggle
to survive out here.

The seals rely entirely
on the ocean,

not just for food and water,

but as a means to escape
the desert heat.

So understanding how they cope
does not reveal

how the rest of life
can survive here

with little to no water.

But the coast does hold the key

to how this desert was formed
in the first place.

The sand grains
that are continually deposited

on to the Namib's beaches
by Atlantic waves

are blown into the interior
by relentless winds...

creating a desert with some
of the largest dunes in the world.

The grains of sand
that shape these giants

may have journeyed here
over 5,000 years ago.

These dunes are actually dynamic.

Like waves in very slow motion,

the winds are constantly
shifting and changing them.

Bone-dry sand forms
arcing crescents -

a back slope piled up
against the prevailing wind

and a shorter, steeper slip face.

As more sand builds up
on the back slope,

the angle of the slip face
becomes critical.

It's only a matter of time
before gravity takes hold

and the slip face crashes down.

In this way, each dune moves along
slowly but surely.

The shifting sands
are searingly hot.

Midday temperatures regularly
exceed 60 degrees.

If a seafarer was lucky enough
to escape the wrecking coast,

they wouldn't last long out here.

But there are animals
and plants that survive here,

where humans have failed.

A few tough species have managed
to find a foothold

in this constantly
shifting environment.

They may be small, but they are
the true giants of survival.

All properly built
to handle the heat.

The shovel-snouted lizard's dance

may look bizarre,

but it has a purpose.

It looks like it's simply
getting some respite

from the burning sand,

but there's more to it than that.

It's cleverly taking advantage

of the heat dynamics

of the dune surface.

The air temperature is
a whole ten degrees cooler

just millimetres above the sand,

so a raised foot can cool down

just enough to bring relief.

This desert lizard is so highly
adapted to this environment,

its behaviour so specific
to the Namib,

that it's found nowhere else
on Earth.

It's one of 23 species of reptile
endemic to the Namib,

each with their own unique way

to combat the blistering heat.

We know chameleons as tree dwellers,

but, clearly, the Namaqua
is not your average chameleon.

To survive here,

it too has developed an
extraordinary heat-avoidance tactic.

Like all chameleons,

it can change its skin colour.

However, its colour changes

are not just about communication
or camouflage.

Here, the Namaqua uses colour

to regulate its body temperature.

Following a cool desert night,

the cold-blooded chameleon

flattens its dull, grey body,

angling itself towards
the rising sun,

absorbing the warmth
of the early rays.

But, as the sun grows higher
and hotter,

and with nowhere to hide,

the Namaqua undergoes
a colour transformation.

By turning a brilliant white,

it now no longer absorbs the sun

but can reflect it.

An efficient thermostat.

This astounding animal has taken
an ability to change colour

and adapted it to regulate
its temperature.

A neat example of evolution at work.

But this is not the only
way in which the Namaqua differs

from its forest-dwelling relatives.

Rather than the fused feet used
by tree climbers to grip branches,

this lizard is able
to splay its toes wide.

Not only does this prevent the
indignity of sinking into the sand,

but it also affords this chameleon

something that its relatives lack -

speed.

And when the ground below you
is searingly hot,

it doesn't do any good
to hang around.

So, even in a world without shade
or cover,

with supremely clever
temperature controls,

or thermo-regulation as it's known,

life has learnt to survive.

But there is shade,

if you know where to look.

And so far, we've only scratched
the surface of ingenuity here.

The desert ecosystem
doesn't just exist on the surface.

There's more to discover
by looking in the dune itself.

Sand is not nearly as densely
packed as hard earth.

Between the grains,
there's enough air to breathe.

And, as we can see
on this thermal image,

the sand can be

up to 20 degrees cooler

just centimetres below the surface.

So it's the perfect bolt hole
to keep cool.

Or to lay a trap.

The Namibian spoor spider is tough -

it can withstand higher temperatures

than any other spider in the world.

And its ability to tolerate the heat

is the key to how it gets food

in this lonely place.

It sets its trap
near an isolated grass tuft,

then weaves sand grains together

to create a sunshade

that doubles as a trapdoor.

While the spider tunnels below,

it provides perfect camouflage.

Only a single strand of silk

reveals a more sinister agenda.

Dune ants, on patrol,

investigate the grass for food...

..and trigger the spider's
warning systems.

Gotcha!

Now, the spider uses its tolerance
to high temperatures

to its advantage.

Pinned to the burning sand,

the ant overheats rapidly.

Within seconds,

the ant's core temperature
will have increased by two degrees,

enough to kill it.

Using the hot sand

to do its dirty work

is a brilliant technique.

And with food so scarce,

when it does come along,

the spider can't afford to miss.

While some sit and wait,

others have to hunt for food.

The sand shows evidence of another
bizarre creature that lives here.

Like its arachnid neighbour,

it too makes use of the cooler,
deeper sand.

But it takes advantage of the quirk
of deserts around the world -

the days are hot, ferociously hot.

The nights are cold.

Temperatures drop by 40 degrees.

Now, it's cool enough
for the golden mole,

in its thick fur coat,

to move around.

Having spent the day
deep in the cool sand,

it emerges to hunt
for termites at night.

Air trapped between the grains
allows the mole to breathe,

but also makes the sand unstable.

And so, the golden mole
leaves no tunnel.

He is a sand swimmer,

ploughing through the dunes

as his trail collapses behind him.

Despite its appearance,

this little mammal is not related
to our European mole.

Instead, it's descended from
an ancient group of African mammals

dating back over 40 million years.

So the mole has had plenty of time
to adapt to life in the dunes.

He is entirely blind.

Sensible, really -

eyes would only be damaged
by the sand.

With such little rain,
plants are few and far between.

But termites are most reliably found
around plant roots,

so the mole may have to travel

over five kilometres a night
in search of food.

Without eyes, how does the mole
find its insect prey

in this featureless desert?

Well, grasses blowing in the wind

send percussive vibrations

through the sand.

The golden mole

has an extraordinarily developed
middle ear bone -

proportionally, 6,000 times
bigger than our own.

It's not sight, but sound

that guides this remarkable
little mammal.

It can detect the slightest
movement of grass or insect.

By dipping his head into the sand,

the mole uses his super hearing

to navigate between grass clumps...

..and secure himself a meal.

It is perfectly evolved
for hunting in the sand.

Well, most of the time.

And so, all of the Namibian
desert's inhabitants

have developed unique ways in which
to deal with this microworld.

But these adaptations

by the insects, reptiles and mammals

are because of this extreme
environment.

Clever avoidance tactics, yes,

but not the reason
why this system works.

It's not enough just to avoid
the climate.

In order for an ecosystem
to sustain,

its animals and plants must live
long enough to grow, to reproduce.

And to do that,
they MUST have water.

It's one of the most fundamental
elements of life.

So where is it in this desert?

Well, the Namib is harbouring
a life-giving secret.

The key to this puzzle
has been created

by a meteorological quirk

as old as the desert itself.

Like our golden mole,

the secret to this desert success
avoids the day's heat.

It comes by night.

Fog creeps through the dunes.

But a dense fog in one of the most
arid environments on Earth -

how is this possible?

Well, the ocean knows.

The freezing cold currents

that support those seals
and pound the Namib coast

have another role to play
in life in the interior.

The cold, wet, heavy air

riding the winds above
these currents meet the land

and are forced under the drier
and lighter air from the desert.

Under normal atmospheric conditions,

cold air would sit
high in the atmosphere,

above the warmer surface air.

Instead, these layers are reversed.

This quirk is known
as an inversion layer.

Once trapped, the moisture within
this cold layer forms a dense mist.

And it's this mist, this sea fog

that forms the life blood
of the Namib Desert.

For fog is, in its essence,
just suspended water,

an airborne reservoir.

You just need to know
how to harvest it.

The few plants drip with it.

The desert crickets drink it
from their stems.

A gecko collects water droplets

that have condensed
on its warm eyeballs.

The sidewinding adder licks
water droplets from its skin.

But perhaps the cleverest
adaptation of all

can be attributed to a beetle

or, more accurately, to its back.

The settling fog triggers

the most unusual beetle behaviour.

They're not known as fog baskers
without a reason.

They emerge from the sand
in the early mornings

and, by standing on their heads,

present their backs
to the rolling fog.

The beetle's back is riddled

with peaks that attract the fog,

encouraging droplets to form

which then roll down waxy troughs

into their open mouths.

This peculiar water harvesting
tactic is highly productive.

By the time the fog has been broken
by the sun,

a beetle might have consumed

40% of its body weight in water.

This fog is reliable enough

to allow the beetles to keep topping
up with this vital fluid...

..becoming like walking
water bottles

to other thirsty dune dwellers.

And forming the base
of a complex fog web

in which water is passed through
the ecosystem from prey to predator.

The beetle provides the chameleon

with enough water to live on

for several days.

The sidewinding adder,

a master of desert camouflage,

is also on the hunt for water.

Eyes positioned on top of its head

allow the adder to bury itself
in the sand,

becoming almost
completely invisible.

The adder may have to lie in wait
for several hours

before the right target appears.

By twitching the tip of its tail,

the snake mimics a small insect
in distress.

The perfect lure

for a nearby lizard.

The lizard,

full of water from the morning fog,

becomes a precious resource

to larger predators.

The adder is quick...

..but, on this occasion,

the lizard is faster.

So these fog harvesters
act as both a food and water source

in this arid environment.

But, if these are the very bottom
rung of the food chain,

what are they eating to survive?

In other ecosystems,

plants provide the most basic
food source.

But, even with the fog,

the sand is too dry and unstable

to support any but the hardiest
of plants

and they're not
in sufficient numbers

to support this amount of life.

The Namib Desert has another trick
up its sleeve.

The winds that bring the fog
also bring another lifeline.

They blow in bits of dead plants,

the odd insect and droppings,

known collectively as detritus,

which is deposited on the dunes.

This collection
of environmental scraps

may not seem like rich pickings,

but, for the species that form the
lowest rung of the food chain,

it's manna from heaven.

Fog-basking beetles
are detritovores,

feeding on dead and decomposing
organic matter.

But this is fast food.

The beetles must work quickly

before their meal is once more
blown away by the winds.

the energy from the detritus will be
transferred to the predator,

making the success

of this entire ecosystem

dependent on the winds

that blow across this amazing land.

At first glance, Namibia's coastal
desert might seem lifeless...

..but by looking closely

and examining the life here,

in this microworld,

where species succeed

because of their unique adaptations

that protect them against

the very climate in which they live.

We've discovered the true secret
to life.

Not in the desert itself,

not in the structure of the dunes

or hidden in the coastal sands.

This ecosystem relies entirely
on external forces.

Without cold ocean currents

and the winds that rush
along this coast

bringing the key ingredients
for life,

this desert would be truly barren.

Instead, animals forge
an existence here

that cannot be found

anywhere else on the planet.

The secret to survival is in the
very air of the Namib Desert...

..and the extraordinary creatures

that have evolved to harvest it.