0:00:04 > 0:00:09The sky is one of the most challenging places to live.
0:00:10 > 0:00:12But all across the world,
0:00:12 > 0:00:16extraordinary animals do something we can only dream of.
0:00:18 > 0:00:20Take to the air.
0:00:24 > 0:00:26Some spend their whole lives up here.
0:00:29 > 0:00:33Others only visit for a moment.
0:00:35 > 0:00:39We'll discover how many incredible animals thrive in the sky...
0:00:43 > 0:00:46..and what clever tricks they use to get airborne.
0:00:48 > 0:00:51With the help of some specially trained animals,
0:00:51 > 0:00:53the latest technology
0:00:53 > 0:00:56and special effects techniques,
0:00:56 > 0:00:59we'll reveal brand-new discoveries
0:00:59 > 0:01:02that explain how animals take to the skies.
0:01:05 > 0:01:07This is Life In The Air.
0:01:16 > 0:01:21So, how do animals take to the air in the first place?
0:01:21 > 0:01:24In this episode, we'll meet incredible creatures,
0:01:24 > 0:01:27each with their own special techniques.
0:01:27 > 0:01:30But they must all overcome one of our planet's
0:01:30 > 0:01:33most powerful and universal forces.
0:01:34 > 0:01:35Gravity.
0:01:44 > 0:01:47It takes a very special animal to defy gravity.
0:01:54 > 0:01:57But in Namibia, Southern Africa,
0:01:57 > 0:01:59there's one that's mastered it like no other.
0:02:02 > 0:02:04The caracal.
0:02:05 > 0:02:09A cat with a unique ability to leave the earth.
0:02:11 > 0:02:13It does something remarkable.
0:02:14 > 0:02:17It catches birds in flight.
0:02:19 > 0:02:22What looks like a misplaced haystack
0:02:22 > 0:02:24is the largest nest in the natural world.
0:02:26 > 0:02:28Home to 100 sociable weavers.
0:02:30 > 0:02:34An irresistible target for a hungry cat.
0:02:34 > 0:02:37CARACAL GROWLS
0:02:37 > 0:02:40You could forgive a bird for believing it was safely out of reach.
0:02:42 > 0:02:45But the caracal is perfectly designed to catch it.
0:02:47 > 0:02:49Its front is smaller and lightweight
0:02:51 > 0:02:55But its back legs are built as a booster rocket -
0:02:55 > 0:02:5930% longer and with twice the muscle mass.
0:03:00 > 0:03:04This design maximises the caracal's speed on takeoff.
0:03:06 > 0:03:10And the faster it's travelling when it leaves the earth,
0:03:10 > 0:03:12the higher it will get.
0:03:15 > 0:03:19Caracals are built for a vertical launch.
0:03:21 > 0:03:26DRAMATIC MUSIC PLAYS
0:04:32 > 0:04:34But what goes up must come down.
0:04:38 > 0:04:41And come down in the right way.
0:04:44 > 0:04:48We know that cats always land on their feet,
0:04:48 > 0:04:49but how?
0:04:50 > 0:04:55This mystery kept scientists arguing for over a century.
0:04:55 > 0:04:57It needs to turn around,
0:04:57 > 0:05:01but to do that, it has to push against something else.
0:05:02 > 0:05:04But there's nothing there.
0:05:08 > 0:05:13This caracal is about to do something that would seem impossible.
0:05:15 > 0:05:18All cats have a remarkable design.
0:05:18 > 0:05:23A flexible spine which allows them to rotate their front and back ends
0:05:23 > 0:05:26in different directions at the same time.
0:05:28 > 0:05:30As it falls back to earth,
0:05:30 > 0:05:33the caracal creates a clockwise rotation
0:05:33 > 0:05:35in the front half of its body,
0:05:35 > 0:05:38but the back spins in the opposite direction.
0:05:44 > 0:05:48By spinning in two different directions at the same time,
0:05:48 > 0:05:52the caracal is effectively pushing against itself.
0:05:54 > 0:05:55But it does even more.
0:05:57 > 0:05:59Like a spinning ice-skater,
0:05:59 > 0:06:02it pulls its front legs close
0:06:02 > 0:06:05which makes the front half of its body spin faster.
0:06:08 > 0:06:11This creates a twist in its spine
0:06:11 > 0:06:13allowing it to swing the back legs round...
0:06:14 > 0:06:17..and prepare for landing.
0:06:31 > 0:06:35NEIL ARMSTRONG: Houston, The Eagle has landed.
0:06:37 > 0:06:40This cat not only defies gravity
0:06:40 > 0:06:43but lands again safely,
0:06:43 > 0:06:45and it all happens...
0:06:47 > 0:06:50..in under a second,
0:06:50 > 0:06:52something all cats can do.
0:06:57 > 0:06:59Catching food is just one of the many reasons
0:06:59 > 0:07:01why animals leap into the sky.
0:07:06 > 0:07:10Gazelles leap to show predators that they are too difficult to catch.
0:07:16 > 0:07:19Tree-living lemurs leap to move quickly
0:07:19 > 0:07:21across dangerous open ground.
0:07:23 > 0:07:26The perfect way to make a rapid escape.
0:07:27 > 0:07:32But while all leaping animals must overcome gravity,
0:07:32 > 0:07:38there's one that uses the power of gravity itself to take to the skies.
0:08:07 > 0:08:11The Australian outback is one of the toughest places to live.
0:08:17 > 0:08:20Temperatures can reach 50 degrees centigrade.
0:08:26 > 0:08:31A kangaroo can only survive by wetting its body to stay cool.
0:08:31 > 0:08:35An extravagant use of water in one of the driest continents on the planet.
0:08:40 > 0:08:44They need a constant supply of water to replace what they lose.
0:08:45 > 0:08:48In a desert over a million kilometres square...
0:08:50 > 0:08:53..how does a kangaroo travel huge distances
0:08:53 > 0:08:55without breaking a sweat?
0:08:59 > 0:09:03They've developed the most efficient form of travel found on land.
0:09:05 > 0:09:10And it all relies on the unique design of those enormous legs.
0:09:10 > 0:09:12FAST-TEMPO MUSIC PLAYS
0:09:17 > 0:09:20The secret lies in the tendons at the base of the ankle
0:09:20 > 0:09:22which connect muscle to bone.
0:09:24 > 0:09:27Normally tendons are tough and strong.
0:09:28 > 0:09:32But a kangaroo's are curiously weak and stretchy.
0:09:33 > 0:09:37So when gravity brings it back to earth
0:09:37 > 0:09:41their special tendons act like huge elastic bands
0:09:41 > 0:09:44absorbing the energy but then releasing it again.
0:09:48 > 0:09:50Almost half the power for the next leap
0:09:50 > 0:09:52comes not from the muscles...
0:09:53 > 0:09:57..but from the energy recycled by these tendons.
0:09:57 > 0:09:59By taking to the air,
0:09:59 > 0:10:01kangaroos have evolved the most efficient way
0:10:01 > 0:10:03of travelling on earth.
0:10:08 > 0:10:14But it only works because they take to the air.
0:10:16 > 0:10:20When we run, our legs have to move faster,
0:10:20 > 0:10:21and we use more energy.
0:10:22 > 0:10:25But hopping, like this, is unique.
0:10:28 > 0:10:30When a kangaroo speeds up
0:10:30 > 0:10:31its legs don't move faster.
0:10:33 > 0:10:36Simply by altering the angle of takeoff,
0:10:36 > 0:10:39it can increase the distance it flies with each hop.
0:10:40 > 0:10:42It means no matter how fast
0:10:42 > 0:10:45a cruising kangaroo decides to travel,
0:10:45 > 0:10:49its muscles do almost exactly the same amount of work.
0:10:54 > 0:10:58They can fly along at the speed of an Olympic sprinter,
0:10:58 > 0:11:00ten metres every second,
0:11:00 > 0:11:03over 4m with every stride
0:11:03 > 0:11:06and never get tired.
0:11:07 > 0:11:09For mile after mile,
0:11:09 > 0:11:14after mile, after mile, after mile, after mile...
0:11:24 > 0:11:25..to reach this.
0:11:27 > 0:11:28A sheep station oasis.
0:11:30 > 0:11:31Where there's always water.
0:11:35 > 0:11:37SHEEP BAA
0:11:37 > 0:11:40While the sheep could never leap their fence,
0:11:40 > 0:11:44the kangaroo still has enough energy to tackle it with ease.
0:12:06 > 0:12:10It's only because of their energy-recycling tendons
0:12:10 > 0:12:13and their ability to take off at the perfect angle
0:12:13 > 0:12:16that kangaroos can not only survive
0:12:16 > 0:12:19one of the most hostile environments on the planet,
0:12:19 > 0:12:21but make it look easy.
0:12:23 > 0:12:28But if you thought kangaroos had the ultimate launch mechanism,
0:12:28 > 0:12:29you'd be wrong.
0:12:33 > 0:12:35Early spring in an English field.
0:12:38 > 0:12:41It looks empty, but down in the grass,
0:12:41 > 0:12:45something extraordinary is about to happen.
0:12:47 > 0:12:50One of the greatest acrobatic acts in nature.
0:13:03 > 0:13:06Meet the planthopper.
0:13:06 > 0:13:08Barely 4mm long.
0:13:09 > 0:13:12This one is not yet fully grown,
0:13:12 > 0:13:14but even though it has no wings,
0:13:14 > 0:13:18it has an incredible ability to get airborne.
0:13:20 > 0:13:22And it's going to need it soon.
0:13:25 > 0:13:28This field won't be empty for long.
0:13:28 > 0:13:32COWS MOO
0:13:32 > 0:13:36Cows have spent the winter sheltering in barns.
0:13:39 > 0:13:42For months, they wait to be out in the fields again.
0:13:45 > 0:13:49MUSIC: The Blue Danube by Johann Strauss II
0:14:00 > 0:14:02But in early spring,
0:14:02 > 0:14:04the day finally arrives
0:14:04 > 0:14:07when they are let loose once again.
0:14:12 > 0:14:15They're so excited, they gambol like lambs.
0:14:23 > 0:14:26COWS MOO
0:14:26 > 0:14:29Not so exciting for the hoppers.
0:14:29 > 0:14:32Now they have potentially lethal neighbours.
0:14:32 > 0:14:33But when in danger,
0:14:33 > 0:14:37this incredible little insect does something which looks impossible.
0:14:39 > 0:14:42They simply...disappear.
0:14:54 > 0:15:01Rewinding then slowing the action 700 times reveals the truth.
0:15:04 > 0:15:07Fleas may be known as the greatest leapers,
0:15:07 > 0:15:10but plant hoppers rewrite the record books
0:15:10 > 0:15:14when it comes to one of the fastest takeoffs in the natural world.
0:15:17 > 0:15:19Having the ultimate ejector seat
0:15:19 > 0:15:23means they need something found nowhere else in nature.
0:15:24 > 0:15:25Cogs.
0:15:25 > 0:15:28COGS CLANK Just before takeoff,
0:15:28 > 0:15:32between their legs rows of tiny teeth intermesh,
0:15:32 > 0:15:33locking them together.
0:15:34 > 0:15:38It's quite literally a clutch in their crotch.
0:15:41 > 0:15:44These cogs ensure that when one leg moves
0:15:44 > 0:15:47the other has to
0:15:47 > 0:15:50within 30 millionths of a second,
0:15:50 > 0:15:53accelerating the hopper to 700g.
0:15:54 > 0:15:56If you were in that rocket,
0:15:56 > 0:16:02you'd be pushed into your seat with a force of 56 tonnes.
0:16:04 > 0:16:09But this record-breaking leap has one major flaw.
0:16:09 > 0:16:14If it fires those legs on unstable ground,
0:16:14 > 0:16:19that much power can spin the hopper hopelessly out of control.
0:16:24 > 0:16:28Each launch is a leap of faith into the unknown.
0:16:28 > 0:16:33MUSIC: The Blue Danube by Johann Strauss II
0:16:53 > 0:16:57Hoppers, kangaroos and caracals defy gravity
0:16:57 > 0:16:59with an incredible launch,
0:16:59 > 0:17:00and they're not alone.
0:17:03 > 0:17:06The animal kingdom is full of fabulous leapers.
0:17:07 > 0:17:10But even the greatest leap inevitably ends
0:17:10 > 0:17:14with gravity bringing you crashing back to earth.
0:17:15 > 0:17:17A moment's lapse in concentration...
0:17:20 > 0:17:23..and it can catch you completely unawares.
0:17:29 > 0:17:32You might be the world's greatest leaper,
0:17:32 > 0:17:34but you can't let it go to your head.
0:17:40 > 0:17:44If you want control in the air and to manage your fall,
0:17:44 > 0:17:46you need another strategy.
0:17:48 > 0:17:51And in the flooded forests of North Carolina, USA,
0:17:51 > 0:17:53there's an animal that does just this.
0:17:56 > 0:17:59This is a world unchanged for thousands of years.
0:18:03 > 0:18:07But we're here to meet the swamp's newest arrivals
0:18:07 > 0:18:09who are about to be born.
0:18:12 > 0:18:16Their proud-looking father is considered by some
0:18:16 > 0:18:18the most attractive bird in North America.
0:18:21 > 0:18:24But it still took time to win his partner's affection.
0:18:28 > 0:18:32And this is the most important day since they paired up six months ago.
0:18:36 > 0:18:38When they decided to start a family,
0:18:38 > 0:18:42they had no choice but to make their nest high in the trees...
0:18:44 > 0:18:46..to protect their 12 eggs.
0:18:48 > 0:18:50Not only from alligators...
0:18:55 > 0:18:57..but from deadly snakes.
0:19:02 > 0:19:05The height that kept eggs safe
0:19:05 > 0:19:08now creates huge problems
0:19:08 > 0:19:09on day one.
0:19:10 > 0:19:12Jump day.
0:19:13 > 0:19:16Until now, they've kept their nest a secret.
0:19:18 > 0:19:22With all 12 noisy chicks hatching at once,
0:19:22 > 0:19:24they will soon be discovered by predators.
0:19:25 > 0:19:28Their mother has to get them down in minutes.
0:19:29 > 0:19:30But they can't fly.
0:19:33 > 0:19:34There's only one thing to do.
0:19:36 > 0:19:37Jump for it.
0:19:40 > 0:19:44On the day they hatch, these tiny ducklings must confront
0:19:44 > 0:19:47the force that all flying animals must conquer.
0:19:49 > 0:19:50Gravity.
0:19:55 > 0:19:56Now the clock is ticking.
0:20:00 > 0:20:02Every splash could attract a predator.
0:20:03 > 0:20:05If the fall doesn't injure them first.
0:20:10 > 0:20:11You might think the water saves them...
0:20:13 > 0:20:16..but hit that too fast and it's like falling onto concrete.
0:20:23 > 0:20:25The ducklings save themselves
0:20:25 > 0:20:28by altering the invisible air that surrounds us all.
0:20:30 > 0:20:33A falling duckling encounters air resistance
0:20:33 > 0:20:37caused by having to push invisible air molecules aside.
0:20:38 > 0:20:40Even at a day old,
0:20:40 > 0:20:43it's using airflow in two important ways.
0:20:54 > 0:20:58First, the duckling instinctively angles its webbed feet and tiny wings
0:20:58 > 0:21:00to make sure it's the right way up.
0:21:01 > 0:21:03Like a free-falling parachutist.
0:21:08 > 0:21:13Secondly, its fluffy body makes it hard for that air to get past.
0:21:13 > 0:21:16It's known as drag and slows its fall.
0:21:18 > 0:21:23Without this air resistance, after little more than 30 seconds,
0:21:23 > 0:21:26a falling duckling would break the sound barrier.
0:21:31 > 0:21:34By using the air around it,
0:21:34 > 0:21:36the duckling ensures it can control its fall...
0:21:38 > 0:21:42..hit the water upright and at a survivable speed.
0:21:52 > 0:21:58In under a minute, all 11 - make that 12 - ducklings are down,
0:21:58 > 0:22:01allowing the mother to lead them to safety
0:22:01 > 0:22:05before they attract the attention of lurking predators.
0:22:10 > 0:22:13These ducklings show that you can start to beat gravity
0:22:13 > 0:22:15by controlling your body in the air
0:22:15 > 0:22:18and altering the way air flows around you.
0:22:24 > 0:22:26Surviving a free fall is one thing,
0:22:26 > 0:22:30but what if you need more control to get yourself out of danger?
0:22:39 > 0:22:42It's winter in the far north of America.
0:22:43 > 0:22:47Temperatures nose dive to minus 40 degrees centigrade.
0:22:49 > 0:22:52Colder than the average at the North Pole.
0:22:55 > 0:22:58It brings big problems for the animals that live here.
0:23:01 > 0:23:02Squirrels.
0:23:05 > 0:23:07In the day, there are too many predators.
0:23:11 > 0:23:14Night is the only time they dare venture out.
0:23:20 > 0:23:23But in the winter, food is scarce.
0:23:26 > 0:23:30And deep snow makes it impossible to move on the ground.
0:23:31 > 0:23:35They need to find a short cut between the trees.
0:23:39 > 0:23:43Their only option is to jump for it.
0:23:43 > 0:23:45DRAMATIC MUSIC PLAYS
0:23:52 > 0:23:56This is the moment that most squirrels would start to worry.
0:23:58 > 0:24:02But these ones have something special tucked up their sleeves.
0:24:05 > 0:24:08And that's really big sleeves.
0:24:10 > 0:24:12They are flying squirrels.
0:24:29 > 0:24:34When climbing trees, muscles retract their flying gear,
0:24:34 > 0:24:39but once airborne, a wriggle reveals a simple wing.
0:24:39 > 0:24:44Two layers of fur-lined skin stretched between wrists and ankles.
0:24:46 > 0:24:52Just imagine a normal squirrel inside a furry, elastic duvet cover.
0:24:58 > 0:25:01Flying squirrels have long limbs to create big wings.
0:25:03 > 0:25:07A flattened tail adds more surface area
0:25:07 > 0:25:09and steers the squirrel in the air.
0:25:11 > 0:25:15And each hand has a second thumb, giving the wing an upturned tip.
0:25:17 > 0:25:21These winglets can reduce drag by up to 20%
0:25:21 > 0:25:23and are now found on most aircraft...
0:25:24 > 0:25:28..a few million years after they first appeared on squirrels.
0:25:32 > 0:25:36But how does this furry wing help the squirrel glide?
0:25:41 > 0:25:44The squirrel's body diverts oncoming air...
0:25:45 > 0:25:48..forcing the air downwards.
0:25:49 > 0:25:53This generates a force in the opposite direction
0:25:53 > 0:25:55known as lift,
0:25:55 > 0:25:57which pushes the squirrel up.
0:25:59 > 0:26:01It sounds complicated,
0:26:01 > 0:26:05but if you've ever stuck your hand out of a car window,
0:26:05 > 0:26:07you know how this works.
0:26:10 > 0:26:12Using this simple wing,
0:26:12 > 0:26:15flying squirrels can glide the length of a football field,
0:26:15 > 0:26:17but rarely do.
0:26:17 > 0:26:20And the reason is a major predator.
0:26:27 > 0:26:29The great horned owl.
0:26:32 > 0:26:34For the owl, the ice is an asset.
0:26:36 > 0:26:39It freezes its kills,
0:26:39 > 0:26:41then thaws out its frozen ready-meals...
0:26:43 > 0:26:45..as and when it's hungry.
0:26:49 > 0:26:51In the air, owls are silent killers.
0:26:54 > 0:26:57Their feathers evolved to absorb every sound.
0:26:59 > 0:27:02A squirrel is unlikely to hear an oncoming owl,
0:27:02 > 0:27:08so its safest strategy is to always imagine one might be closing in.
0:27:15 > 0:27:17Compared to the owl,
0:27:17 > 0:27:20the squirrel's simple wing makes it a sitting duck.
0:27:28 > 0:27:32That's why, whether an owl is there or not,
0:27:32 > 0:27:36these squirrels feel a need for speed.
0:27:42 > 0:27:45Flying up to 30km/h.
0:27:50 > 0:27:53But high-speed flying gives them a new problem.
0:27:55 > 0:27:58Hurtling fast towards solid wooden objects.
0:28:03 > 0:28:07Thankfully, emergency stops are second nature.
0:28:08 > 0:28:12Just before landing, the squirrel tilts backwards.
0:28:12 > 0:28:14Its wing becomes a parachute.
0:28:16 > 0:28:18The elastic skin billows out...
0:28:20 > 0:28:22..trapping air to reduce speed.
0:28:24 > 0:28:27An arched back absorbs impact like a curved suspension spring.
0:28:29 > 0:28:33And all four limbs contact at once for a textbook landing.
0:28:37 > 0:28:39The simple wing has enabled the squirrel
0:28:39 > 0:28:42to not only control the air around it,
0:28:42 > 0:28:45but reduce the impact of landing at speed.
0:28:48 > 0:28:51Allowing the flying squirrel to escape predators
0:28:51 > 0:28:52and feed safely,
0:28:52 > 0:28:55even in the depths of winter.
0:28:58 > 0:29:02But what if you need to glide like a squirrel from tree to tree
0:29:02 > 0:29:03but you don't have any wings?
0:29:05 > 0:29:08Your body would need to be a very special shape.
0:29:13 > 0:29:15One, we'll find here.
0:29:18 > 0:29:21The tropical rainforests of Borneo.
0:29:23 > 0:29:27Home to the paradise tree snake.
0:29:30 > 0:29:31When it comes to flying,
0:29:31 > 0:29:34you've got to feel sorry for snakes.
0:29:34 > 0:29:38Not a leg to stand on, let alone a wing to flap.
0:29:40 > 0:29:44But its body shape can teach us a lot about how to fly.
0:29:48 > 0:29:52Living high in the trees presents a huge challenge.
0:29:56 > 0:29:58If you want to travel across the jungle...
0:30:00 > 0:30:02..you've a long journey ahead.
0:30:05 > 0:30:09All the way down one tree
0:30:09 > 0:30:11before you can climb the next.
0:30:12 > 0:30:16And the forest floor is no place to linger.
0:30:16 > 0:30:19ANIMAL GROWLS
0:30:19 > 0:30:23It's full of predators just waiting for animals passing through.
0:30:37 > 0:30:40Perhaps that's why, here in Borneo,
0:30:40 > 0:30:44so many things take to the air.
0:30:47 > 0:30:48Frogs...
0:30:52 > 0:30:53..lizards...
0:30:55 > 0:30:57..even flying plants.
0:30:59 > 0:31:01Well, seeds.
0:31:06 > 0:31:11But how does a snake get around with so many gaps to be crossed?
0:31:14 > 0:31:17This snake has an ingenious solution.
0:31:20 > 0:31:25The bendy snake becomes a rigid rod.
0:31:29 > 0:31:31Its body, a bridge.
0:31:40 > 0:31:42By holding on with their tail,
0:31:42 > 0:31:47tree snakes can cross gaps with 90% of their body unsupported.
0:31:54 > 0:31:57But not even this incredible core body strength
0:31:57 > 0:31:59can prepare them for gaps like this.
0:32:01 > 0:32:05Jungle trees in Asia can be unusually tall.
0:32:05 > 0:32:08The distance between them bigger.
0:32:10 > 0:32:13There's no way a snake can bridge gaps like these.
0:32:15 > 0:32:18Instead, it does something different.
0:32:20 > 0:32:23There are 3,500 species of snake in the world.
0:32:25 > 0:32:27But only one like this.
0:32:30 > 0:32:35This is a snake that flies.
0:33:24 > 0:33:28What is the secret to this unique gliding ability?
0:33:31 > 0:33:33Remarkably, just after launch,
0:33:33 > 0:33:37the snake throws its ribs forward,
0:33:37 > 0:33:41flattening its body into a very special shape.
0:33:43 > 0:33:45It's called an aerofoil.
0:33:46 > 0:33:50This shape changes the way air flows around the snake.
0:33:51 > 0:33:54Oncoming streams of air passing over the top
0:33:54 > 0:33:57are suddenly forced to change direction
0:33:57 > 0:33:58and speed up.
0:34:00 > 0:34:04This faster moving air is strung out,
0:34:04 > 0:34:06so the air pressure above drops.
0:34:09 > 0:34:13With low pressure air above and high pressure air below,
0:34:13 > 0:34:17the snake is pushed up and is now gliding.
0:34:21 > 0:34:24The snake's flight path reveals another important way
0:34:24 > 0:34:26the aerofoil shape works.
0:34:28 > 0:34:32On takeoff, the snake plummets,
0:34:32 > 0:34:33gravity takes hold
0:34:33 > 0:34:35and the snake picks up speed.
0:34:36 > 0:34:40But as it falls faster, it begins to fly forward.
0:34:42 > 0:34:44That's because the faster
0:34:44 > 0:34:46that the air flows over the aerofoil's surface,
0:34:46 > 0:34:49the more lift it generates.
0:34:49 > 0:34:51And the snake starts to glide.
0:34:55 > 0:34:58Inevitably, all gliders come to earth
0:34:58 > 0:35:01because they're using gravity to pick up speed.
0:35:02 > 0:35:06They have to drop in height to fly forward,
0:35:06 > 0:35:08so if you want to stay airborne for longer...
0:35:10 > 0:35:12..you need to power your flight.
0:35:17 > 0:35:20To discover how animals do that,
0:35:20 > 0:35:22we're heading to the middle of the Atlantic.
0:35:26 > 0:35:30This ocean stretches over 12,000km from pole to pole.
0:35:37 > 0:35:41And is almost as deep as Everest is high.
0:35:45 > 0:35:48In this vast wilderness,
0:35:48 > 0:35:53even a single palm frond floating miles from tropical shores
0:35:53 > 0:35:57can suddenly find itself the centre of considerable attention.
0:36:10 > 0:36:14In an empty ocean, it offers shelter.
0:36:16 > 0:36:19And inevitably, life begins to gather.
0:36:29 > 0:36:33It's a haven, not just for these fish
0:36:33 > 0:36:35but soon for their eggs.
0:36:39 > 0:36:41For a handful of days each year...
0:36:43 > 0:36:46..thousands of fish meet to give life to their next generation.
0:36:55 > 0:36:58Quite how they choose the perfect moment is still a mystery.
0:37:00 > 0:37:05But once the first fish spawns, the rest soon follow.
0:37:07 > 0:37:10Each female can lay 20,000 eggs.
0:37:12 > 0:37:18And before long, the sea turns milky as males rush in to fertilise them.
0:37:23 > 0:37:28In the haze, it's hard to see approaching predators.
0:37:28 > 0:37:30TENSE MUSIC PLAYS
0:37:36 > 0:37:38Rapid escape is critical.
0:37:40 > 0:37:45And this is when these amazing fish reveal their true identity.
0:37:48 > 0:37:49Flying fish.
0:37:54 > 0:37:57Fins become wings.
0:38:04 > 0:38:07Unlike the snake, they can't use gravity to pick up speed...
0:38:09 > 0:38:13..which is why their tail is unique amongst all fish.
0:38:15 > 0:38:17The lower half is longer than the top.
0:38:18 > 0:38:21So even with its body in the air,
0:38:21 > 0:38:23the tip of the tail remains submerged.
0:38:28 > 0:38:32Thrashing it side to side provides forward momentum,
0:38:32 > 0:38:34and as the fish speeds up,
0:38:34 > 0:38:38the aerofoil-shaped pectoral fins generate lift.
0:38:39 > 0:38:42Until, eventually, the force is enough to send them flying.
0:38:50 > 0:38:53Once their special tail has got them started,
0:38:53 > 0:38:56flying fish can glide over 100m
0:38:56 > 0:38:59at speeds of 60km/h.
0:39:06 > 0:39:09Their fins, shaped for high-speed flight,
0:39:09 > 0:39:11are a match for the fastest falcon.
0:39:15 > 0:39:16But that's not all.
0:39:20 > 0:39:22Flying fish are held up by a cushion of air
0:39:22 > 0:39:25compressed between their bodies and the water's surface.
0:39:29 > 0:39:30And when they lose height,
0:39:30 > 0:39:34their powerful tail can accelerate them skyward once again.
0:39:40 > 0:39:43This is powered flight.
0:39:46 > 0:39:50By pushing themselves forward, the fish create more lift
0:39:50 > 0:39:52and can spend longer in the air.
0:39:56 > 0:39:58Now we're really flying.
0:40:11 > 0:40:14Powered flight opens up the skies to many animals.
0:40:18 > 0:40:21Most do this by flapping their wings.
0:40:25 > 0:40:27But it's hard work.
0:40:34 > 0:40:38Flapping requires more power than any other form of movement...
0:40:41 > 0:40:45..increasing an animal's energy costs by up to 20 times.
0:40:51 > 0:40:54To stay active, a hovering hummingbird needs to drink
0:40:54 > 0:40:57two-thirds of its body weight in nectar every day.
0:41:01 > 0:41:04But what if an animal could stay airborne for hours...
0:41:06 > 0:41:08..with no effort at all?
0:41:09 > 0:41:10It sounds impossible.
0:41:13 > 0:41:16But in Africa there are those that can.
0:41:20 > 0:41:24There is one species which needs to travel hundreds of kilometres
0:41:24 > 0:41:27to find and follow their migrating food.
0:41:27 > 0:41:29In this case, the wildebeest herds
0:41:29 > 0:41:32travelling across the African continent.
0:41:35 > 0:41:38This animal's great skill is taking advantage of the fact
0:41:38 > 0:41:40that air is constantly in motion.
0:41:43 > 0:41:46Meet the vulture.
0:41:51 > 0:41:55A vulture's huge wings generate so much lift
0:41:55 > 0:41:59that in a glide they lose height at less than a metre per second.
0:42:02 > 0:42:05So, in theory, if they can find air
0:42:05 > 0:42:07that's rising faster than they are falling,
0:42:07 > 0:42:12they could fly forever without flapping a wing.
0:42:15 > 0:42:18In the early morning, impatient birds take test flights.
0:42:20 > 0:42:23They wait for the air to start moving.
0:42:24 > 0:42:28And as the land warms up, that's just what happens.
0:42:30 > 0:42:33Although we can't see it,
0:42:33 > 0:42:36moving air flows through a landscape like water.
0:42:39 > 0:42:41As the sun heats the cliff face,
0:42:41 > 0:42:44warming air rises
0:42:44 > 0:42:46dragging cool air up from the valley floor.
0:42:55 > 0:42:59When this air collides with the cliff,
0:42:59 > 0:43:01just like the sea hitting a harbour wall...
0:43:03 > 0:43:05..it's driven further upward.
0:43:18 > 0:43:19Across the plains,
0:43:19 > 0:43:22an area of land that absorbs more heat
0:43:22 > 0:43:25creates columns of warm rising air above it,
0:43:25 > 0:43:27thermals.
0:43:40 > 0:43:43These are the skies' elevators,
0:43:43 > 0:43:46and the vultures ride them in their hundreds.
0:44:27 > 0:44:29It's the need to capture rising air
0:44:29 > 0:44:31that explains the shape of a vulture's wing.
0:44:33 > 0:44:35They need to be huge like a sail
0:44:35 > 0:44:37to catch as much rising air as possible.
0:44:41 > 0:44:44But big wings can create problems.
0:44:46 > 0:44:48As an animal flies,
0:44:48 > 0:44:53the higher pressure air below a wing is sucked over the tip to the top,
0:44:53 > 0:44:58creating spirals of unstable air that slow the vulture
0:44:58 > 0:45:01and would make it lose height faster.
0:45:01 > 0:45:04Broad wings generate more of this drag
0:45:04 > 0:45:08as there's a wider wing tip for the air to spill over,
0:45:08 > 0:45:11and that's why vultures have those long single feathers
0:45:11 > 0:45:13at the end of their wings.
0:45:13 > 0:45:18They effectively turn one wide wing into several thin ones,
0:45:18 > 0:45:21which helps stop those negative spirals of air from forming.
0:45:27 > 0:45:32This unique design makes the vulture a true record-breaker...
0:45:35 > 0:45:38and when conditions are right, hundreds gather...
0:45:40 > 0:45:42..using a thermal to gain height...
0:45:45 > 0:45:49..and those incredible wings to effortlessly glide onward
0:45:49 > 0:45:50in search of the next thermal.
0:45:53 > 0:45:58Hopping across the African plains between islands of rising air,
0:45:58 > 0:46:03they can fly hundreds of kilometres a day in search of food,
0:46:03 > 0:46:07and reach altitudes of over 11,000m,
0:46:07 > 0:46:10making them the world's highest-flying bird.
0:46:20 > 0:46:23The vulture is just one of the many extraordinary animals
0:46:23 > 0:46:25we've seen that take to the air to survive.
0:46:31 > 0:46:34These animals have some incredible adaptations
0:46:34 > 0:46:36for launching into the skies.
0:46:40 > 0:46:42Some have mastered control in the air.
0:46:44 > 0:46:51Others generate forces like drag to protect them from impact,
0:46:51 > 0:46:53and lift to allow them to glide.
0:46:57 > 0:46:58Those that go further
0:46:58 > 0:47:02take advantage of a special aerofoil shape,
0:47:02 > 0:47:05and by increasing the airspeed over its surface
0:47:05 > 0:47:07can stay in flight for longer.
0:47:12 > 0:47:15But only the very best combine all of these skills...
0:47:16 > 0:47:19..to effortlessly beat gravity...
0:47:20 > 0:47:24..and truly master life in the air.
0:47:43 > 0:47:45In this series, the team's mission
0:47:45 > 0:47:48was to reveal the incredible abilities of airborne animals
0:47:48 > 0:47:51in more detail than ever before.
0:47:53 > 0:47:54Weeks of patient filming
0:47:54 > 0:47:57allowed the team to capture real-life events,
0:47:57 > 0:48:02like the leaping ducklings, which only occur once a year.
0:48:02 > 0:48:06Revealing the science behind how these animals master the skies
0:48:06 > 0:48:11required additional filming tricks and some incredible individuals
0:48:11 > 0:48:15who would allow the team to capture their unique behaviour -
0:48:15 > 0:48:17impossible to achieve in any other way.
0:48:19 > 0:48:22Of all the animals in the programme
0:48:22 > 0:48:26none presented more of a challenge than the flying snake.
0:48:26 > 0:48:28They glide effortlessly,
0:48:28 > 0:48:31but capturing their natural behaviour would have been impossible
0:48:31 > 0:48:34without the world's leading expert
0:48:34 > 0:48:37and some ingenious film-making techniques.
0:48:37 > 0:48:42To film them, the crew heads to Tenom Agricultural Park in Borneo -
0:48:42 > 0:48:44a known hotspot for flying snakes.
0:48:47 > 0:48:51Director Simon Bell is excited by the prospect.
0:48:51 > 0:48:53So, we've got this site that gives us a beautiful backdrop.
0:48:53 > 0:48:56We've got some lovely jungle in the background,
0:48:56 > 0:48:57some mountains in the distance.
0:48:57 > 0:48:59It's going to look great.
0:48:59 > 0:49:02Cameraman Pete McCowen prepares.
0:49:02 > 0:49:06The success of the shoot relies on a high-speed digital camera
0:49:06 > 0:49:08that slows the action 60 times.
0:49:10 > 0:49:14Director Simon is aware of the challenges ahead.
0:49:14 > 0:49:17It's really hard to see these snakes in pristine forest.
0:49:17 > 0:49:19They're not uncommon,
0:49:19 > 0:49:21but you're never going to see them in the jungle
0:49:21 > 0:49:25unless you work with a guy who knows them like Jake knows them.
0:49:25 > 0:49:29Professor Jake Socha - the world's expert on flying snakes.
0:49:29 > 0:49:32He's studied them for over 15 years,
0:49:32 > 0:49:34and for him, the chance to observe them
0:49:34 > 0:49:36in their native habitat is an opportunity
0:49:36 > 0:49:38to record new behaviour.
0:49:40 > 0:49:42He's brought more cameras than the crew.
0:49:44 > 0:49:48Before his studies, flying snakes had been the stuff of legend.
0:49:50 > 0:49:53The literature goes back into the late 1800s.
0:49:53 > 0:49:56What's in there is foreigners talking to locals
0:49:56 > 0:49:58who describe a flying snake,
0:49:58 > 0:50:03and the scientists think the locals are making things up.
0:50:03 > 0:50:05Some people say they're straight in the air,
0:50:05 > 0:50:07some people say they're wiggling around.
0:50:07 > 0:50:10I found it compelling to solve this mystery.
0:50:10 > 0:50:13What is the snake doing and then how does it do it?
0:50:13 > 0:50:15With his years of experience,
0:50:15 > 0:50:18Jake is realistic about how the crew can film the snake's behaviour.
0:50:18 > 0:50:21To put a camera in the trees
0:50:21 > 0:50:25and hope that you have an animal glide on by,
0:50:25 > 0:50:26that's impossible to do.
0:50:26 > 0:50:30If you really want to see what they do in the air,
0:50:30 > 0:50:34you have to set up an experimental situation.
0:50:34 > 0:50:36The crew's best hope for filming snake flight
0:50:36 > 0:50:38is to use a technique Jake pioneered
0:50:38 > 0:50:42with a few modifications for the jungle.
0:50:43 > 0:50:45They need three things.
0:50:45 > 0:50:49A tower for the snakes to fly from, a target for them to aim at,
0:50:49 > 0:50:52and of course, the snakes themselves.
0:50:52 > 0:50:55This clearing is the perfect spot,
0:50:55 > 0:50:57and with some help from the crew,
0:50:57 > 0:51:01rope access specialists begin construction on a 50-foot tower,
0:51:01 > 0:51:04carrying everything into the jungle by hand.
0:51:06 > 0:51:08There's a lot that could go wrong.
0:51:08 > 0:51:10You know, we've got some really good guys,
0:51:10 > 0:51:12but that tower's only halfway up right now.
0:51:12 > 0:51:14It's going to be twice that height.
0:51:17 > 0:51:18The steel cable at the top
0:51:18 > 0:51:21will help to compress the tower, giving it rigidity.
0:51:21 > 0:51:23The problem with that is you then have a potential
0:51:23 > 0:51:28for sort of...snaking, we call it.
0:51:28 > 0:51:31So, what we then do is we put in half-height cables
0:51:31 > 0:51:34to try and prevent that sort of S-shape developing within the tower.
0:51:34 > 0:51:35That'll hold it nice and straight
0:51:35 > 0:51:38and once they're there, it's a bomber.
0:51:38 > 0:51:40While the rope team worked on Jake's safety,
0:51:40 > 0:51:43Simon ensured the ground was covered in dry grass
0:51:43 > 0:51:45for the softest of snake landings.
0:51:48 > 0:51:51For his research, Jake needs to control
0:51:51 > 0:51:53the exact height of the snake's flight,
0:51:53 > 0:51:56so a tower is the only option.
0:51:56 > 0:51:58Without him, the crew have little hope
0:51:58 > 0:52:01of bringing snake flight to the screen.
0:52:01 > 0:52:03So, we're kind of in his hands in a way.
0:52:03 > 0:52:07You know, this is all his design, this whole set-up.
0:52:07 > 0:52:09When that snake's gliding from that scaffold tower,
0:52:09 > 0:52:11it's going to look spectacular.
0:52:11 > 0:52:14Although Simon now feels more confident,
0:52:14 > 0:52:16there's still one vital thing missing.
0:52:17 > 0:52:22There are tens of thousands of this particular snake on Borneo,
0:52:22 > 0:52:26but to tell you the truth, they're not easy to find.
0:52:26 > 0:52:29I've never been in the forest and spotted one
0:52:29 > 0:52:30and been able to catch it.
0:52:32 > 0:52:35As day one ends, success is far from certain.
0:52:40 > 0:52:44Day two, and as the crew put the finishing touches to the tower,
0:52:44 > 0:52:45they get some good news.
0:52:45 > 0:52:49Snakes have been found closer to home than anyone had imagined.
0:52:51 > 0:52:54- What do you think? - Ah, they're beautiful.
0:52:55 > 0:52:59But seeing them up close gives cameraman Pete new concerns.
0:52:59 > 0:53:02They're beautiful little snakes, but like the one Jake's got,
0:53:02 > 0:53:03it's a very small little snake,
0:53:03 > 0:53:05so trying to capture that is going to be interesting.
0:53:05 > 0:53:07You're going to have a hard time keeping track,
0:53:07 > 0:53:09or maybe not cos you're a pro, right?
0:53:09 > 0:53:13Yeah. That's the impression I try to give.
0:53:13 > 0:53:17Filming worries aside, it's time to get Jake's experiment underway.
0:53:19 > 0:53:22Trees in Borneo can be well over 75m high.
0:53:24 > 0:53:28For a flying snake, a 15-metre tower is child's play.
0:53:28 > 0:53:31If only it were the same for the scientists.
0:53:31 > 0:53:33I'm generally bad with heights.
0:53:33 > 0:53:35I don't like 'em.
0:53:35 > 0:53:38I think that's a good place to be, right?
0:53:38 > 0:53:40It's keeps you away from tall things
0:53:40 > 0:53:41that you might fall off.
0:53:43 > 0:53:45I'm a bit concerned about Jake.
0:53:45 > 0:53:48He has revealed that he is a little bit afraid of heights.
0:53:48 > 0:53:51It should be perfectly safe, but there will be a bit of a sway
0:53:51 > 0:53:53when you get to the top of that thing.
0:53:55 > 0:53:58I'm not utterly frightened.
0:53:58 > 0:54:00I'm just frightened.
0:54:00 > 0:54:04Hey, I'm almost there, right? Thank God.
0:54:04 > 0:54:06It's a nice view, though.
0:54:06 > 0:54:07Well done!
0:54:07 > 0:54:09With over 15 years of experience,
0:54:09 > 0:54:13Jake knows that hoisting snakes slowly in a soft bag
0:54:13 > 0:54:14they can comfortably curl up in
0:54:14 > 0:54:19is the best way to ensure they arrive relaxed and raring to fly.
0:54:19 > 0:54:21Snake arrival by pulley.
0:54:21 > 0:54:23At least, that's the theory.
0:54:23 > 0:54:25He is not having any of it,
0:54:25 > 0:54:28so I'm not going to force him to do anything.
0:54:28 > 0:54:30To film natural behaviour,
0:54:30 > 0:54:35you can't rush one of the world's most impressive flying stars.
0:54:35 > 0:54:36All right.
0:54:38 > 0:54:39The crew are ready...
0:54:39 > 0:54:42Come on, baby. Thank you.
0:54:42 > 0:54:45..and they must stay alert,
0:54:45 > 0:54:49because when a snake decides to fly, you don't get much warning.
0:54:49 > 0:54:51Going right away. Now.
0:54:51 > 0:54:52Oooh! Ooh!
0:54:52 > 0:54:56Phenomenal. Just phenomenal.
0:54:56 > 0:54:58Just as Jake predicted,
0:54:58 > 0:55:00from this height the snakes are landing safely
0:55:00 > 0:55:03and reaching the target tree.
0:55:03 > 0:55:06They're flying. They're absolutely flying.
0:55:06 > 0:55:09It's a great relief, and all eyes turn to cameraman Pete.
0:55:10 > 0:55:12Ready? Now.
0:55:14 > 0:55:16HE MUMBLES
0:55:16 > 0:55:19Yeah, that was really great. I couldn't even see it.
0:55:20 > 0:55:25The snakes are really taking to the experimental set-up.
0:55:25 > 0:55:26Dropping now.
0:55:26 > 0:55:30All the pressure is now on Pete.
0:55:30 > 0:55:33- Pete, there are some bits where it's going this way.- Yeah.
0:55:33 > 0:55:35- Did you get any of that?- No.
0:55:36 > 0:55:39But with the snakes flying so well,
0:55:39 > 0:55:41Pete is learning to keep up with them.
0:55:45 > 0:55:46Woo!
0:55:48 > 0:55:49Well done, Pete. Well held.
0:55:49 > 0:55:51That's amazing.
0:55:51 > 0:55:53Whoa!
0:55:53 > 0:55:55I think that's the first time I've ever seen this,
0:55:55 > 0:55:58where you see a phenomenal glide
0:55:58 > 0:56:01and then she landed on the tree there.
0:56:01 > 0:56:04This is brand-new data and it tells us that
0:56:04 > 0:56:07when the snake lands on a natural substrate
0:56:07 > 0:56:08that its body is flat.
0:56:08 > 0:56:11This is beautiful. I'm really excited to get this.
0:56:11 > 0:56:15With the shots captured, there's only one thing left to do -
0:56:15 > 0:56:18release the stars of Jake's research back to where they came from.
0:56:20 > 0:56:21This is my favourite snake.
0:56:24 > 0:56:26It's ready, it's looping down.
0:56:26 > 0:56:27OK.
0:56:31 > 0:56:34After nearly 20 years of study,
0:56:34 > 0:56:38Jake is still discovering new things about the animal that he loves.
0:56:40 > 0:56:44What I got out of this trip is a new appreciation for this animal.
0:56:44 > 0:56:47Some people look at me and think that I'm insane.
0:56:47 > 0:56:49They say, "Why would you want to do that?"
0:56:52 > 0:56:56Any time you can learn something that is new to science
0:56:56 > 0:56:59and new to the world, you know, that's pretty exciting.
0:56:59 > 0:57:01This is fantastic.
0:57:01 > 0:57:03The team had revealed the remarkable flight
0:57:03 > 0:57:07of flying snakes in more detail than ever before,
0:57:07 > 0:57:11capturing the beauty of an animal once thought of as only a myth.
0:57:17 > 0:57:19Next time, we discover how nature
0:57:19 > 0:57:23has pushed the basic flying body plan to the limit.
0:57:24 > 0:57:27How do the heaviest animals take off,
0:57:27 > 0:57:30the fastest use speed as a weapon
0:57:30 > 0:57:34and half a million avert air traffic disaster in total darkness?