All language subtitles for BBC.Life.In.The.Air.Series.1.1of3.Defying.Gravity.720p.HDTV.x264.AAC.MVGroup.org

The sky is one of
the most challenging places to live.

But all across the world,

extraordinary animals do
something we can only dream of.

Take to the air.

Some spend their whole lives up here.

Others only visit for a moment.

We'll discover how many incredible
animals thrive in the sky...

..and what clever tricks they use
to get airborne.

With the help of
some specially trained animals,

the latest technology

and special effects techniques,

we'll reveal brand-new discoveries

that explain
how animals take to the skies.

This is Life In The Air.

So, how do animals take to the air
in the first place?

In this episode, we'll meet
incredible creatures,

each with
their own special techniques.

But they must all overcome
one of our planet's

most powerful and universal forces.

Gravity.

It takes a very special animal
to defy gravity.

But in Namibia, Southern Africa,

there's one that's mastered it
like no other.

The caracal.

A cat with a unique ability
to leave the earth.

It does something remarkable.

It catches birds in flight.

What looks like a misplaced haystack

is the largest nest
in the natural world.

Home to 100 sociable weavers.

An irresistible target
for a hungry cat.

CARACAL GROWLS

You could forgive a bird for
believing it was safely out of reach.

But the caracal is perfectly designed
to catch it.

Its front is smaller and lightweight

But its back legs are built
as a booster rocket -

30% longer and with
twice the muscle mass.

This design maximises
the caracal's speed on takeoff.

And the faster it's travelling
when it leaves the earth,

the higher it will get.

Caracals are built
for a vertical launch.

DRAMATIC MUSIC PLAYS

But what goes up must come down.

And come down in the right way.

We know that cats always land
on their feet,

but how?

This mystery kept scientists arguing
for over a century.

It needs to turn around,

but to do that, it has to push
against something else.

But there's nothing there.

This caracal is about to do something
that would seem impossible.

All cats have a remarkable design.

A flexible spine which allows them
to rotate their front and back ends

in different directions
at the same time.

As it falls back to earth,

the caracal creates
a clockwise rotation

in the front half of its body,

but the back spins
in the opposite direction.

By spinning in two different
directions at the same time,

the caracal is effectively
pushing against itself.

But it does even more.

Like a spinning ice-skater,

it pulls its front legs close

which makes the front half of
its body spin faster.

This creates a twist in its spine

allowing it to swing
the back legs round...

..and prepare for landing.

NEIL ARMSTRONG:
Houston, The Eagle has landed.

This cat not only defies gravity

but lands again safely,

and it all happens...

..in under a second,

something all cats can do.

Catching food is just
one of the many reasons

why animals leap into the sky.

Gazelles leap to show predators
that they are too difficult to catch.

Tree-living lemurs leap
to move quickly

across dangerous open ground.

The perfect way to make
a rapid escape.

But while all leaping animals
must overcome gravity,

there's one that uses the power of
gravity itself to take to the skies.

The Australian outback is one
of the toughest places to live.

Temperatures can reach
50 degrees centigrade.

A kangaroo can only survive
by wetting its body to stay cool.

An extravagant use of water in one of
the driest continents on the planet.

They need a constant supply of water
to replace what they lose.

In a desert over
a million kilometres square...

..how does a kangaroo
travel huge distances

without breaking a sweat?

They've developed the most efficient
form of travel found on land.

And it all relies on the unique
design of those enormous legs.

FAST-TEMPO MUSIC PLAYS

The secret lies in the tendons
at the base of the ankle

which connect muscle to bone.

Normally tendons are
tough and strong.

But a kangaroo's are curiously
weak and stretchy.

So when gravity brings it
back to earth

their special tendons act
like huge elastic bands

absorbing the energy
but then releasing it again.

Almost half the power
for the next leap

comes not from the muscles...

..but from the energy
recycled by these tendons.

By taking to the air,

kangaroos have evolved
the most efficient way

of travelling on earth.

But it only works because
they take to the air.

When we run, our legs
have to move faster,

and we use more energy.

But hopping, like this, is unique.

When a kangaroo speeds up

its legs don't move faster.

Simply by altering
the angle of takeoff,

it can increase the distance it flies
with each hop.

It means no matter how fast

a cruising kangaroo
decides to travel,

its muscles do almost exactly
the same amount of work.

They can fly along at
the speed of an Olympic sprinter,

ten metres every second,

over 4m with every stride

and never get tired.

For mile after mile,

after mile, after mile,
after mile, after mile...

..to reach this.

A sheep station oasis.

Where there's always water.

SHEEP BAA

While the sheep could never leap
their fence,

the kangaroo still has enough energy
to tackle it with ease.

It's only because of
their energy-recycling tendons

and their ability to take off at
the perfect angle

that kangaroos can not only survive

one of the most hostile environments
on the planet,

but make it look easy.

But if you thought kangaroos had
the ultimate launch mechanism,

you'd be wrong.

Early spring in an English field.

It looks empty,
but down in the grass,

something extraordinary
is about to happen.

One of the greatest acrobatic acts
in nature.

Meet the planthopper.

Barely 4mm long.

This one is not yet fully grown,

but even though it has no wings,

it has an incredible ability
to get airborne.

And it's going to need it soon.

This field won't be empty for long.

COWS MOO

Cows have spent the winter
sheltering in barns.

For months, they wait to be
out in the fields again.

MUSIC: The Blue Danube
by Johann Strauss II

But in early spring,

the day finally arrives

when they are let loose once again.

They're so excited,
they gambol like lambs.

COWS MOO

Not so exciting for the hoppers.

Now they have potentially
lethal neighbours.

But when in danger,

this incredible little insect does
something which looks impossible.

They simply...disappear.

Rewinding then slowing the action
700 times reveals the truth.

Fleas may be known as
the greatest leapers,

but plant hoppers rewrite
the record books

when it comes to one of the fastest
takeoffs in the natural world.

Having the ultimate ejector seat

means they need something
found nowhere else in nature.

Cogs.

COGS CLANK
Just before takeoff,

between their legs rows of
tiny teeth intermesh,

locking them together.

It's quite literally
a clutch in their crotch.

These cogs ensure that
when one leg moves

the other has to

within 30 millionths of a second,

accelerating the hopper to 700g.

If you were in that rocket,

you'd be pushed into your seat
with a force of 56 tonnes.

But this record-breaking leap
has one major flaw.

If it fires those legs
on unstable ground,

that much power can spin the hopper
hopelessly out of control.

Each launch is a leap of faith
into the unknown.

MUSIC: The Blue Danube
by Johann Strauss II

Hoppers, kangaroos and caracals
defy gravity

with an incredible launch,

and they're not alone.

The animal kingdom is full
of fabulous leapers.

But even the greatest leap
inevitably ends

with gravity bringing you
crashing back to earth.

A moment's lapse in concentration...

..and it can catch you
completely unawares.

You might be
the world's greatest leaper,

but you can't let it
go to your head.

If you want control in the air
and to manage your fall,

you need another strategy.

And in the flooded forests
of North Carolina, USA,

there's an animal that does
just this.

This is a world unchanged
for thousands of years.

But we're here to meet
the swamp's newest arrivals

who are about to be born.

Their proud-looking father
is considered by some

the most attractive bird
in North America.

But it still took time
to win his partner's affection.

And this is the most important day
since they paired up six months ago.

When they decided to start a family,

they had no choice but to make
their nest high in the trees...

..to protect their 12 eggs.

Not only from alligators...

..but from deadly snakes.

The height that kept eggs safe

now creates huge problems

on day one.

Jump day.

Until now, they've kept their nest
a secret.

With all 12 noisy chicks
hatching at once,

they will soon be discovered
by predators.

Their mother has to get them down
in minutes.

But they can't fly.

There's only one thing to do.

Jump for it.

On the day they hatch,
these tiny ducklings must confront

the force that all flying animals
must conquer.

Gravity.

Now the clock is ticking.

Every splash could attract
a predator.

If the fall doesn't injure them
first.

You might think the water
saves them...

..but hit that too fast and
it's like falling onto concrete.

The ducklings save themselves

by altering the invisible air
that surrounds us all.

A falling duckling encounters
air resistance

caused by having to push invisible
air molecules aside.

Even at a day old,

it's using airflow
in two important ways.

First, the duckling instinctively
angles its webbed feet and tiny wings

to make sure it's the right way up.

Like a free-falling parachutist.

Secondly, its fluffy body makes
it hard for that air to get past.

It's known as drag
and slows its fall.

Without this air resistance,
after little more than 30 seconds,

a falling duckling would break
the sound barrier.

By using the air around it,

the duckling ensures
it can control its fall...

..hit the water upright
and at a survivable speed.

In under a minute, all 11 -
make that 12 - ducklings are down,

allowing the mother to lead them
to safety

before they attract the attention
of lurking predators.

These ducklings show that you can
start to beat gravity

by controlling your body in the air

and altering the way
air flows around you.

Surviving a free fall is one thing,

but what if you need more control
to get yourself out of danger?

It's winter in
the far north of America.

Temperatures nose dive
to minus 40 degrees centigrade.

Colder than the average
at the North Pole.

It brings big problems for
the animals that live here.

Squirrels.

In the day,
there are too many predators.

Night is the only time
they dare venture out.

But in the winter, food is scarce.

And deep snow makes it impossible
to move on the ground.

They need to find a short cut
between the trees.

Their only option is to jump for it.

DRAMATIC MUSIC PLAYS

This is the moment that most
squirrels would start to worry.

But these ones have something special
tucked up their sleeves.

And that's really big sleeves.

They are flying squirrels.

When climbing trees,
muscles retract their flying gear,

but once airborne,
a wriggle reveals a simple wing.

Two layers of fur-lined skin
stretched between wrists and ankles.

Just imagine a normal squirrel
inside a furry, elastic duvet cover.

Flying squirrels have long limbs
to create big wings.

A flattened tail
adds more surface area

and steers the squirrel in the air.

And each hand has a second thumb,
giving the wing an upturned tip.

These winglets can reduce drag
by up to 20%

and are now found on most aircraft...

..a few million years after
they first appeared on squirrels.

But how does this furry wing
help the squirrel glide?

The squirrel's body diverts
oncoming air...

..forcing the air downwards.

This generates a force
in the opposite direction

known as lift,

which pushes the squirrel up.

It sounds complicated,

but if you've ever stuck your hand
out of a car window,

you know how this works.

Using this simple wing,

flying squirrels can glide
the length of a football field,

but rarely do.

And the reason is a major predator.

The great horned owl.

For the owl, the ice is an asset.

It freezes its kills,

then thaws out
its frozen ready-meals...

..as and when it's hungry.

In the air, owls are silent killers.

Their feathers evolved
to absorb every sound.

A squirrel is unlikely to hear
an oncoming owl,

so its safest strategy is to always
imagine one might be closing in.

Compared to the owl,

the squirrel's simple wing
makes it a sitting duck.

That's why,
whether an owl is there or not,

these squirrels feel
a need for speed.

Flying up to 30km/h.

But high-speed flying
gives them a new problem.

Hurtling fast towards
solid wooden objects.

Thankfully, emergency stops
are second nature.

Just before landing,
the squirrel tilts backwards.

Its wing becomes a parachute.

The elastic skin billows out...

..trapping air to reduce speed.

An arched back absorbs impact
like a curved suspension spring.

And all four limbs contact at once
for a textbook landing.

The simple wing
has enabled the squirrel

to not only control
the air around it,

but reduce the impact of landing
at speed.

Allowing the flying squirrel
to escape predators

and feed safely,

even in the depths of winter.

But what if you need to glide like
a squirrel from tree to tree

but you don't have any wings?

Your body would need to be
a very special shape.

One, we'll find here.

The tropical rainforests of Borneo.

Home to the paradise tree snake.

When it comes to flying,

you've got to feel sorry for snakes.

Not a leg to stand on,
let alone a wing to flap.

But its body shape can teach us
a lot about how to fly.

Living high in the trees
presents a huge challenge.

If you want to travel across
the jungle...

..you've a long journey ahead.

All the way down one tree

before you can climb the next.

And the forest floor
is no place to linger.

ANIMAL GROWLS

It's full of predators just
waiting for animals passing through.

Perhaps that's why, here in Borneo,

so many things take to the air.

Frogs...

..lizards...

..even flying plants.

Well, seeds.

But how does a snake get around
with so many gaps to be crossed?

This snake has
an ingenious solution.

The bendy snake becomes a rigid rod.

Its body, a bridge.

By holding on with their tail,

tree snakes can cross gaps
with 90% of their body unsupported.

But not even
this incredible core body strength

can prepare them for gaps like this.

Jungle trees in Asia
can be unusually tall.

The distance between them bigger.

There's no way a snake
can bridge gaps like these.

Instead, it does something different.

There are 3,500 species of snake
in the world.

But only one like this.

This is a snake that flies.

What is the secret to
this unique gliding ability?

Remarkably, just after launch,

the snake throws its ribs forward,

flattening its body into
a very special shape.

It's called an aerofoil.

This shape changes the way
air flows around the snake.

Oncoming streams of air
passing over the top

are suddenly forced
to change direction

and speed up.

This faster moving air is strung out,

so the air pressure above drops.

With low pressure air above
and high pressure air below,

the snake is pushed up
and is now gliding.

The snake's flight path
reveals another important way

the aerofoil shape works.

On takeoff, the snake plummets,

gravity takes hold

and the snake picks up speed.

But as it falls faster,
it begins to fly forward.

That's because the faster

that the air flows over
the aerofoil's surface,

the more lift it generates.

And the snake starts to glide.

Inevitably, all gliders come to earth

because they're using gravity
to pick up speed.

They have to drop in height
to fly forward,

so if you want to stay airborne
for longer...

..you need to power your flight.

To discover how animals do that,

we're heading to
the middle of the Atlantic.

This ocean stretches
over 12,000km from pole to pole.

And is almost as deep
as Everest is high.

In this vast wilderness,

even a single palm frond
floating miles from tropical shores

can suddenly find itself
the centre of considerable attention.

In an empty ocean, it offers shelter.

And inevitably,
life begins to gather.

It's a haven,
not just for these fish

but soon for their eggs.

For a handful of days each year...

..thousands of fish meet to give life
to their next generation.

Quite how they choose the perfect
moment is still a mystery.

But once the first fish spawns,
the rest soon follow.

Each female can lay 20,000 eggs.

And before long, the sea turns milky
as males rush in to fertilise them.

In the haze, it's hard to see
approaching predators.

TENSE MUSIC PLAYS

Rapid escape is critical.

And this is when these amazing fish
reveal their true identity.

Flying fish.

Fins become wings.

Unlike the snake, they can't use
gravity to pick up speed...

..which is why their tail
is unique amongst all fish.

The lower half is longer than
the top.

So even with its body in the air,

the tip of the tail
remains submerged.

Thrashing it side to side
provides forward momentum,

and as the fish speeds up,

the aerofoil-shaped pectoral fins
generate lift.

Until, eventually, the force is
enough to send them flying.

Once their special tail
has got them started,

flying fish can glide over 100m

at speeds of 60km/h.

Their fins,
shaped for high-speed flight,

are a match for the fastest falcon.

But that's not all.

Flying fish are held up
by a cushion of air

compressed between
their bodies and the water's surface.

And when they lose height,

their powerful tail can accelerate
them skyward once again.

This is powered flight.

By pushing themselves forward,
the fish create more lift

and can spend longer in the air.

Now we're really flying.

Powered flight opens up the skies
to many animals.

Most do this by flapping their wings.

But it's hard work.

Flapping requires more power
than any other form of movement...

..increasing an animal's energy costs
by up to 20 times.

To stay active,
a hovering hummingbird needs to drink

two-thirds of its body weight
in nectar every day.

But what if an animal
could stay airborne for hours...

..with no effort at all?

It sounds impossible.

But in Africa
there are those that can.

There is one species which needs
to travel hundreds of kilometres

to find and follow
their migrating food.

In this case, the wildebeest herds

travelling across
the African continent.

This animal's great skill
is taking advantage of the fact

that air is constantly in motion.

Meet the vulture.

A vulture's huge wings
generate so much lift

that in a glide they lose height
at less than a metre per second.

So, in theory, if they can find air

that's rising faster
than they are falling,

they could fly forever
without flapping a wing.

In the early morning,
impatient birds take test flights.

They wait for the air
to start moving.

And as the land warms up,
that's just what happens.

Although we can't see it,

moving air flows through
a landscape like water.

As the sun heats the cliff face,

warming air rises

dragging cool air up from
the valley floor.

When this air collides
with the cliff,

just like the sea
hitting a harbour wall...

..it's driven further upward.

Across the plains,

an area of land that absorbs
more heat

creates columns of warm rising air
above it,

thermals.

These are the skies' elevators,

and the vultures ride them
in their hundreds.

It's the need to capture rising air

that explains the shape of
a vulture's wing.

They need to be huge like a sail

to catch as much rising air
as possible.

But big wings can create problems.

As an animal flies,

the higher pressure air below a wing
is sucked over the tip to the top,

creating spirals of unstable air
that slow the vulture

and would make it lose height faster.

Broad wings generate
more of this drag

as there's a wider wing tip
for the air to spill over,

and that's why vultures have
those long single feathers

at the end of their wings.

They effectively turn one wide wing
into several thin ones,

which helps stop those negative
spirals of air from forming.

This unique design makes the vulture
a true record-breaker...

and when conditions are right,
hundreds gather...

..using a thermal to gain height...

..and those incredible wings
to effortlessly glide onward

in search of the next thermal.

Hopping across the African plains
between islands of rising air,

they can fly hundreds of kilometres
a day in search of food,

and reach altitudes of
over 11,000m,

making them the world's
highest-flying bird.

The vulture is just one of
the many extraordinary animals

we've seen that take
to the air to survive.

These animals have some
incredible adaptations

for launching into the skies.

Some have mastered
control in the air.

Others generate forces like drag
to protect them from impact,

and lift to allow them to glide.

Those that go further

take advantage of
a special aerofoil shape,

and by increasing the airspeed
over its surface

can stay in flight for longer.

But only the very best
combine all of these skills...

..to effortlessly beat gravity...

..and truly master life in the air.

In this series, the team's mission

was to reveal the incredible
abilities of airborne animals

in more detail than ever before.

Weeks of patient filming

allowed the team to capture
real-life events,

like the leaping ducklings,
which only occur once a year.

Revealing the science behind how
these animals master the skies

required additional filming tricks
and some incredible individuals

who would allow the team to capture
their unique behaviour -

impossible to achieve
in any other way.

Of all the animals
in the programme

none presented more of a challenge
than the flying snake.

They glide effortlessly,

but capturing their natural
behaviour would have been impossible

without the world's leading expert

and some ingenious
film-making techniques.

To film them, the crew heads to
Tenom Agricultural Park in Borneo -

a known hotspot for flying snakes.

Director Simon Bell
is excited by the prospect.

So, we've got this site that
gives us a beautiful backdrop.

We've got some lovely jungle
in the background,

some mountains in the distance.

It's going to look great.

Cameraman Pete McCowen prepares.

The success of the shoot relies
on a high-speed digital camera

that slows the action 60 times.

Director Simon is aware
of the challenges ahead.

It's really hard to see
these snakes in pristine forest.

They're not uncommon,

but you're never going
to see them in the jungle

unless you work with a guy
who knows them like Jake knows them.

Professor Jake Socha -
the world's expert on flying snakes.

He's studied them
for over 15 years,

and for him,
the chance to observe them

in their native habitat
is an opportunity

to record new behaviour.

He's brought more cameras
than the crew.

Before his studies, flying snakes
had been the stuff of legend.

The literature goes back
into the late 1800s.

What's in there is foreigners
talking to locals

who describe a flying snake,

and the scientists think
the locals are making things up.

Some people say
they're straight in the air,

some people say
they're wiggling around.

I found it compelling
to solve this mystery.

What is the snake doing
and then how does it do it?

With his years of experience,

Jake is realistic about how the crew
can film the snake's behaviour.

To put a camera in the trees

and hope that you have
an animal glide on by,

that's impossible to do.

If you really want to see
what they do in the air,

you have to set up
an experimental situation.

The crew's best hope
for filming snake flight

is to use a technique
Jake pioneered

with a few modifications
for the jungle.

They need three things.

A tower for the snakes to fly from,
a target for them to aim at,

and of course,
the snakes themselves.

This clearing is the perfect spot,

and with some help from the crew,

rope access specialists begin
construction on a 50-foot tower,

carrying everything
into the jungle by hand.

There's a lot that could go wrong.

You know,
we've got some really good guys,

but that tower's only
halfway up right now.

It's going to be twice that height.

The steel cable at the top

will help to compress the tower,
giving it rigidity.

The problem with that is
you then have a potential

for sort of...snaking, we call it.

So, what we then do is
we put in half-height cables

to try and prevent that sort of
S-shape developing within the tower.

That'll hold it nice and straight

and once they're there,
it's a bomber.

While the rope team
worked on Jake's safety,

Simon ensured the ground
was covered in dry grass

for the softest of snake landings.

For his research,
Jake needs to control

the exact height
of the snake's flight,

so a tower is the only option.

Without him,
the crew have little hope

of bringing snake flight
to the screen.

So, we're kind of
in his hands in a way.

You know, this is all his design,
this whole set-up.

When that snake's gliding
from that scaffold tower,

it's going to look spectacular.

Although Simon now feels
more confident,

there's still one
vital thing missing.

There are tens of thousands of
this particular snake on Borneo,

but to tell you the truth,
they're not easy to find.

I've never been in
the forest and spotted one

and been able to catch it.

As day one ends,
success is far from certain.

Day two, and as the crew put
the finishing touches to the tower,

they get some good news.

Snakes have been found closer
to home than anyone had imagined.

What do you think?
Ah, they're beautiful.

But seeing them up close gives
cameraman Pete new concerns.

They're beautiful little snakes,
but like the one Jake's got,

it's a very small little snake,

so trying to capture that
is going to be interesting.

You're going to have a hard time
keeping track,

or maybe not
cos you're a pro, right?

Yeah. That's the impression
I try to give.

Filming worries aside, it's time
to get Jake's experiment underway.

Trees in Borneo can be
well over 75m high.

For a flying snake,
a 15-metre tower is child's play.

If only it were the same
for the scientists.

I'm generally bad with heights.

I don't like 'em.

I think that's a good place
to be, right?

It's keeps you away
from tall things

that you might fall off.

I'm a bit concerned about Jake.

He has revealed that he is
a little bit afraid of heights.

It should be perfectly safe,
but there will be a bit of a sway

when you get to the top
of that thing.

I'm not utterly frightened.

I'm just frightened.

Hey, I'm almost there, right?
Thank God.

It's a nice view, though.

Well done!

With over 15 years of experience,

Jake knows that hoisting snakes
slowly in a soft bag

they can comfortably curl up in

is the best way to ensure they
arrive relaxed and raring to fly.

Snake arrival by pulley.

At least, that's the theory.

He is not having any of it,

so I'm not going to force him
to do anything.

To film natural behaviour,

you can't rush one of the world's
most impressive flying stars.

All right.

The crew are ready...

Come on, baby. Thank you.

..and they must stay alert,

because when a snake decides to fly,
you don't get much warning.

Going right away. Now.

Oooh! Ooh!

Phenomenal. Just phenomenal.

Just as Jake predicted,

from this height
the snakes are landing safely

and reaching the target tree.

They're flying.
They're absolutely flying.

It's a great relief,
and all eyes turn to cameraman Pete.

Ready? Now.

HE MUMBLES

Yeah, that was really great.
I couldn't even see it.

The snakes are really taking
to the experimental set-up.

Dropping now.

All the pressure is now on Pete.

Pete, there are some bits
where it's going this way. Yeah.

Did you get any of that? No.

But with the snakes flying so well,

Pete is learning
to keep up with them.

Woo!

Well done, Pete. Well held.

That's amazing.

Whoa!

I think that's the first time
I've ever seen this,

where you see a phenomenal glide

and then she landed
on the tree there.

This is brand-new data
and it tells us that

when the snake lands
on a natural substrate

that its body is flat.

This is beautiful.
I'm really excited to get this.

With the shots captured,
there's only one thing left to do -

release the stars of Jake's research
back to where they came from.

This is my favourite snake.

It's ready, it's looping down.

OK.

After nearly 20 years of study,

Jake is still discovering new things
about the animal that he loves.

What I got out of this trip is
a new appreciation for this animal.

Some people look at me
and think that I'm insane.

They say, "Why would you
want to do that?"

Any time you can learn something
that is new to science

and new to the world, you know,
that's pretty exciting.

This is fantastic.

The team had revealed
the remarkable flight

of flying snakes in more detail
than ever before,

capturing the beauty of an animal
once thought of as only a myth.

Next time, we discover how nature

has pushed the basic flying
body plan to the limit.

How do the heaviest animals
take off,

the fastest use speed as a weapon

and half a million avert air traffic
disaster in total darkness?