Defying Gravity

NARRATOR: 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.

[CHIRPING] 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.

[GROWLS] YOU COULD FORGIVE A BIRD FOR BELIEVING IT WAS SAFE AND SOUND...

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 MAXIMIZES THE CARACAL'S SPEED ON TAKE-OFF.

AND THE FASTER IT'S TRAVELING WHEN IT LEAVES THE EARTH, THE HIGHER IT WILL GET.

MAN: ...15 SECONDS.

NARRATOR: CARACALS ARE BUILT FOR A VERTICAL LAUNCH.

MAN: IGNITION SEQUENCE STARTS.

5... 4... 3... 2... 1.

LIFT OFF.

WE HAVE A LIFT OFF.

NARRATOR: 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 AROUND... AND PREPARE FOR LANDING.

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.

[SNIFFLES] GAZELLES LEAP TO SHOW PREDATORS THAT THEY'RE 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 122 DEGREES FAHRENHEIT.

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 KILOMETERS 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.

THE SECRET LIES IN THE TENDONS AT THE BASE OF THE ANKLE, WHICH CONNECT BONE TO MUSCLE.

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 MUSCLES BUT FROM ENERGY RECYCLED BY THESE TENDONS.

BY TAKING TO THE AIR, KANGAROOS HAVE EVOLVED THE MOST EFFICIENT WAY OF TRAVELING 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 TAKE-OFF, 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, 10 METERS EVERY SECOND, OVER 4 METERS WITH EVERY STRIDE, AND NEVER GET TIRED.

FOR MILE AFTER MILE AFTER MILE AFTER MILE AFTER MILE AFTER MILE AFTER MILE.

TO REACH THIS.

A SHEEP STATION OASIS... WHERE THERE'S ALWAYS WATER.

WHILE THE SHEEP COULD NEVER LEAP OVER 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 4 MILLIMETERS 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 IS GONNA NEED IT SOON.

THIS FIELD WON'T BE EMPTY FOR LONG.

[COWS MOOING] AFTER A LONG WINTER, THE DAY FINALLY ARRIVES WHEN THE COWS ARE RELEASED FROM MONTHS OF HOUSE ARREST.

THEY ARE SO EXCITED, THEY FROLIC LIKE LAMBS.

[COWS MOOING] NOT SO EXCITING FOR THE HOPPERS.

NOW THEY HAVE POTENTIALLY LETHAL NEIGHBORS.

BUT WHEN IN DANGER, THIS INCREDIBLE, LITTLE INSECT DOES SOMETHING WHICH LOOKS IMPOSSIBLE.

THEY SIMPLY DISAPPEAR.

200 TIMES FASTER THAN THE BLINK OF AN EYE.

REWINDING, THEN SLOWING THE ACTION 700 TIMES REVEALS THE TRUTH.

FLEAS MAY BE KNOWN AS THE GREATEST LEAPERS, BUT PLANTHOPPERS REWRITE THE RECORD BOOKS WHEN IT COMES TO ONE OF THE FASTEST TAKE-OFFS IN THE NATURAL WORLD.

HAVING THE ULTIMATE EJECTOR SEAT MEANS THEY NEED SOMETHING FOUND NOWHERE ELSE IN NATURE.

COGS.

JUST BEFORE TAKE-OFF, 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 THE FORCE OF 56 TONS.

[COWS MOOING] 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.

[COWS MOOING] EACH LAUNCH IS A LEAP OF FAITH INTO THE UNKNOWN.

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 OFF GUARD.

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, THERE'S AN ANIMAL THAT'S GOT IT ALL FIGURED OUT.

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 DAD IS CONSIDERED BY SOME THE MOST ATTRACTIVE BIRD IN NORTH AMERICA, BUT IT STILL TOOK TIME TO WIN HIS PARTNER'S AFFECTION.

[SCREECHING] AND THIS IS THE MOST IMPORTANT DAY SINCE THEY PAIRED UP 6 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 THE 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 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 SKY DIVER IN FREE FALL.

SECONDLY, ITS FLUFFY BODY MAKES IT HARD FOR THAT AIR TO GET PAST.

THIS IS 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 BECOME BITE-SIZED SNACKS.

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 NORTHERN MAINE.

TEMPERATURES NOSE DIVE TO -40 DEGREES... COLDER THAN THE AVERAGE AT THE NORTH POLE.

IT BRINGS BIG PROBLEMS FOR THE ANIMALS LIVING HERE--SQUIRRELS.

IN THE DAY, THERE ARE TOO MANY PREDATORS.

NIGHT IS THE ONLY TIME THEY DARE TO COME OUT.

BUT IN THE WINTER, FOOD IS SCARCE... AND DEEP SNOW MAKES IT IMPOSSIBLE TO MOVE ON THE GROUND.

THEY NEED TO FIND A SHORTCUT BETWEEN THE TREES.

THEIR ONLY OPTION IS TO JUMP FOR IT.

THIS IS A MOMENT MOST SQUIRRELS WOULD START TO WORRY.

BUT THESE ONES HAVE SOMETHING SPECIAL TUCKED UP THEIR SLEEVES... AND THOSE ARE REALLY BIG SLEEVES.

THEY'RE FLYING SQUIRRELS.

WHEN CLIMBING TREES, MUSCLES RETRACT THEIR FLYING GEAR, BUT ONCE AIRBORNE, A LITTLE 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 PLANES.

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 IT 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 THAT ALLOWS IT TO GO SHOPPING.

IT FREEZES ITS KILLS, THEN THAWS OUT ITS FROZEN DINNERS 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 AT UP TO 19 MILES PER HOUR.

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 4 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.

A SHAPE WE'LL FIND HERE.

THE TROPICAL RAINFORESTS OF BORNEO... HOME TO THE PARADISE TREE SNAKE.

WHEN IT COMES TO FLYING, YOU HAVE 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 GOT A LONG JOURNEY AHEAD.

ALL THE WAY DOWN ONE TREE BEFORE YOU CAN CLIMB UP THE NEXT.

AND THE FOREST FLOOR IS NOT A PLACE TO LINGER.

IT'S FULL OF PREDATORS JUST WAITING FOR PASSING PREY.

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 SLINKY 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 FLYING SNAKE.

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 AND 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 TAKE-OFF, 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 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 INTO THE MIDDLE OF THE ATLANTIC.

THIS OCEAN STRETCHES OVER 7,000 MILES 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 CENTER OF CONSIDERABLE ATTENTION.

IN AN UNFORGIVING OCEAN, IT OFFERS SHELTER, AND INEVITABLY LIFE COMES RUNNING, OR SWIMMING, AS THE CASE MAY BE.

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.

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 FERTILIZE THEM.

IN THE HAZE, IT'S HARD TO SEE APPROACHING PREDATORS.

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 WHEN ITS BODY IS 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 FOR OVER 100 METERS AT SPEEDS OF 37 MILES PER HOUR.

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 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 IS THE KEY TO CONQUERING THE SKIES.

[HONK] MOST WILD FLYERS 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 2/3 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 MILES TO FIND AND FOLLOW THEIR MIGRATING FOOD.

THE WILDEBEEST HERDS TRAVELING ACROSS THE AFRICAN CONTINENT.

THIS ANIMAL'S GREAT SKILL IS TAKING ADVANTAGE OF THE FACT THAT AIR IS CONSTANTLY IN MOTION.

THEY...ARE VULTURES.

A VULTURE'S HUGE WINGS GENERATE SO MUCH LIFT THAT IN A GLIDE, THEY LOSE HEIGHT AT LESS THAN A METER PER SECOND.

SO, IN THEORY, IF THEY CAN FIND AIR 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 WARMS 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 HARBOR WALL, IT'S DRIVEN FURTHER UPWARDS.

ACROSS THE PLAINS, AREAS OF LAND THAT ABSORB MORE HEAT CREATE COLUMNS OF WARM RISING AIR ABOVE IT--THERMALS.

THESE ARE THE SKY'S ELEVATORS AND THE VULTURES RIDE THEM IN THE 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 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 HELP STOP THOSE NEGATIVE SPIRALS OF AIR FROM FORMING.

THIS UNIQUE DESIGN MAKES THE VULTURE A TRUE RECORD-BREAKER.

WHEN CONDITIONS ARE RIGHT, HUNDREDS GATHER, USING A THERMAL TO GAIN HEIGHT.

AND THOSE INCREDIBLE WINGS TO EFFORTLESSLY GLIDE ONWARDS IN SEARCH OF THE NEXT THERMAL.

HOPPING ACROSS THE AFRICAN PLAINS BETWEEN ISLANDS OF RISING AIR, THEY CAN FLY HUNDREDS OF MILES A DAY IN SEARCH OF FOOD, AND REACH ALTITUDES OF OVER 11,000 METERS, MAKING THEM THE WORLD'S HIGHEST-FLYING BIRD.

AND THEY DO IT ALL WITH BARELY A FLAP OF THEIR HUGE WINGS.

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 AIR SPEED OVER ITS SURFACE, CAN STAY IN FLIGHT FOR LONGER.

BUT ONLY THE VERY BEST COMBINE ALL THESE SKILLS TO EFFORTLESSLY BEAT GRAVITY AND TRULY MASTER LIFE IN THE AIR AS "SUPERNATURE"'S WILD FLYERS.

IN THIS SERIES, THE TEAM'S MISSION WAS TO REVEAL THE INCREDIBLE ABILITIES OF AIRBORNE ANIMALS IN MORE DETAIL THAN EVER BEFORE.

[CHIRPING] REVEALING THE SCIENCE BEHIND HOW THESE ANIMALS MASTER THE SKIES REQUIRED ADDITIONAL TRICKS AND SOME INCREDIBLE INDIVIDUALS WHO WOULD ALLOW THE TEAM TO CAPTURE THEIR UNIQUE BEHAVIOR.

BUT OF ALL THE ANIMALS IN THE PROGRAM, NONE PRESENTED MORE OF A CHALLENGE THAN THE FLYING SNAKE.

THEY GLIDE EFFORTLESSLY, BUT CAPTURING THEIR NATURAL BEHAVIOR WOULD HAVE BEEN IMPOSSIBLE WITHOUT SOME INGENIOUS FILMMAKING TECHNIQUES.

THE CREW HEADS TO TENOM AGRICULTURAL PARK IN BORNEO.

THEY NEEDED THE HELP OF PROFESSOR JAKE SOCHA, THE WORLD'S EXPERT ON FLYING SNAKES.

HE'S STUDIED THEM FOR ALMOST 20 YEARS AND BEFORE HIS RESEARCH, THESE ANIMALS 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.

I FOUND IT COMPELLING TO SOLVE THIS MYSTERY.

WHAT IS THE SNAKE DOING AND THEN HOW DOES IT DO IT?

NARRATOR: JAKE IS REALISTIC ABOUT HOW THE CREW CAN FILM THE SNAKE'S BEHAVIOR.

JAKE: TO PUT A CAMERA IN THE TREES, AND HOPE THAT, THAT YOU HAVE AN ANIMAL GLIDE ON BY, THAT'S IMPOSSIBLE TO DO.

YOU HAVE TO SET UP AN EXPERIMENTAL SITUATION.

NARRATOR: THE CREW'S BEST HOPE OF FILMING SNAKE FLIGHT IS TO USE A TECHNIQUE JAKE PIONEERED WITH A FEW MODIFICATIONS FOR THE JUNGLE.

THEY NEED 3 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.

THE CREW PREPARE THE CAMERA WHILE SPECIALISTS START CONSTRUCTING A 50-FOOT TOWER, DOING THEIR BEST TO KEEP COOL IN THE HEAT.

FOR HIS RESEARCH, JAKE NEEDS TO CONTROL THE EXACT HEIGHT OF THE SNAKE'S FLIGHT, SO, A TOWER IS THE ONLY OPTION.

BUT THERE IS STILL ONE VITAL THING MISSING.

JAKE: THERE ARE TENS OF THOUSANDS OF THIS PARTICULAR SNAKE ON BORNEO.

THEY'RE NOT EASY TO FIND.

I'VE NEVER BEEN IN THE FOREST AND SPOTTED ONE AND BEEN ABLE TO CATCH IT.

NARRATOR: BUT AS THE CREW PUT THE FINISHING TOUCHES TO THE TOWER, THEY GET SOME GOOD NEWS.

SNAKES HAVE BEEN FOUND CLOSER TO HOME THAN ANYONE IMAGINED.

JAKE'S EXPERIMENT CAN FINALLY GET UNDER WAY.

TREES IN BORNEO CAN BE WELL OVER 250 FEET HIGH.

FOR A FLYING SNAKE, A 50-FOOT TOWER IS CHILD'S PLAY.

IF ONLY IT WERE THE SAME FOR THE SCIENTISTS.

JAKE: I'M GENERALLY BAD WITH HEIGHTS.

I THINK THAT, THAT'S A GOOD PLACE TO BE.

IT JUST KEEPS YOU AWAY FROM TALL THINGS THAT YOU MIGHT FALL OFF.

I'M NOT, 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!

NARRATOR: JAKE KNOWS THAT HOISTING SNAKES SLOWLY IN A SOFT BAG IS THE BEST WAY TO ENSURE THEY ARRIVE RELAXED AND RARING TO FLY.

SNAKE ARRIVAL BY PULLEY.

NARRATOR: AT LEAST, THAT'S THE THEORY.

ALL RIGHT.

NARRATOR: TO FILM NATURAL BEHAVIOR, YOU CAN'T RUSH THE WORLD'S MOST IMPRESSIVE FLYING STARS.

COME ON, BABY.

THANK YOU.

NARRATOR: THE CREW MUST STAY ALERT, BECAUSE WHEN A SNAKE DECIDES TO FLY, YOU DON'T GET MUCH WARNING.

JAKE: GOING RIGHT AWAY, NOW!

WHOO, WHOOOO.

PHENOMENAL, JUST PHENOMENAL.

NARRATOR: FROM THIS HEIGHT, THE SNAKES CAN EASILY REACH THE CLEARING'S TARGET TREE.

IT'S A GREAT RELIEF, AND ALL EYES TURN TO CAMERAMAN PETE.

READY.

NOW.

PETE: YEAH, THAT WAS REALLY GREAT.

I COULDN'T EVEN SEE IT.

ALL RIGHT, THE SNAKE IS OUT.

NARRATOR: THE SNAKES ARE REALLY TAKING TO THE EXPERIMENTAL SETUP.

JAKE: DROPPING, NOW!

NARRATOR: ALL THE PRESSURE IS NOW ON PETE.

JAKE: PETE, THERE ARE SOME BIT WHERE IT'S GOING THIS WAY.

YEAH.

JAKE: DID YOU GET ANY OF THAT?

NO.

NARRATOR: BUT WITH THE SNAKES FLYING SO WELL, PETE IS LEARNING TO KEEP UP WITH THEM.

MAN: WELL DONE, PETE, WELL HELD, THAT'S AMAZING.

JAKE: I THINK THAT'S THE FIRST TIME I'VE EVER SEEN THIS.

THIS IS BRAND-NEW DATA.

I'M REALLY EXCITED TO GET THIS.

NARRATOR: AFTER NEARLY 20 YEARS OF STUDY, JAKE IS STILL DISCOVERING NEW THINGS ABOUT THE ANIMAL HE LOVES.

JAKE: WHAT I GOT OUT OF THIS TRIP IS A NEW APPRECIATION FOR THIS ANIMAL.

SOME PEOPLE LOOK AT ME AND THINK THAT I'M, I'M INSANE.

THEY SAY, "WHY WOULD YOU WANT TO DO THAT?"

ANYTIME YOU CAN LEARN SOMETHING THAT IS NEW TO SCIENCE AND NEW TO THE WORLD, YOU KNOW, THAT, THAT'S, THAT'S PRETTY EXCITING.

THIS IS FANTASTIC.