Original subtitles

SKIN -- WE ALL HAVE IT.

AND SO DOES EVERY VERTEBRATE ON THE PLANET.

IT KEEPS THE OUTSIDE OUT...

AND THE INSIDE IN.

ANIMALS MAY LOOK VERY DIFFERENT ON THE SURFACE,

BUT WE ALL SHARE THE SAME BASIC SKIN BLUEPRINT.

I'M BEN GARROD, PROFESSOR OF EVOLUTIONARY BIOLOGY,

AND I'M FASCINATED

BY THIS OFTEN-OVERLOOKED WONDER OF NATURE.

IT'S NOT JUST A CASE THAT HE'S HAIRLESS.

THE SKIN'S TOTALLY DIFFERENT.

NOW, GROUNDBREAKING NEW SCIENCE...

THIS IS REALLY QUITE REMARKABLE.

IT SHOULD BE A GAME-CHANGER FOR SO MANY PEOPLE.

[ RATTLING ]THAT SOUND, OH!

IT MAKES THE HAIRS AT THE BACK OF YOUR NECK GO UP,

DOESN'T IT?

...IS REVEALING SKIN'S MYSTERIES.

IT REALLY TRANSFORMS OUR UNDERSTANDING OF DINOSAURS.

I'M GOING TO EXPLORE THE NATURAL HISTORY

OF THE BODY'S LARGEST ORGAN,

TO SEE HOW SKIN HAS ALLOWED ANIMALS

TO CONQUER EVERY HABITAT,

DISAPPEAR INTO THEIR SURROUNDINGS,

AND DEVELOP EXTRASENSORY ABILITIES.

WE'RE EVEN DISCOVERING THE COMPLEX ECOSYSTEM

LIVING ON OUR SKIN.

OH, JIM, THAT'S AWFUL. IT REALLY IS.

IN THIS EPISODE, I'LL FIND OUT HOW SKIN ALLOWS ANIMALS

TO HAVE MORE THAN JUST FIVE SENSES...

OH! SO POWERFUL.

...LIKE BEING ABLE

TO DETECT ELECTRICITY OR EVEN SEE HEAT.

THAT WAS INCREDIBLY QUICK, THOUGH.

YEAH.THAT WAS SUCH A STRIKE.

AND I'LL DISCOVER JUST HOW COMPLEX

OUR SENSE OF TOUCH REALLY IS...

THAT MUST BE SO SENSITIVE.

...AS I EXPLORE HOW SKIN HAS EVOLVED

TO GIVE ANIMALS SUPER SENSES.

I'M GOING TO REVEAL THE SECRETS OF SKIN.

IN ALL THE VARIED HABITATS IN WHICH ANIMALS LIVE,

THEIR SKIN HAS COME TO PLAY A KEY ROLE

IN HELPING THEM GATHER INFORMATION

ABOUT THEIR DIFFERENT ENVIRONMENTS.

WE OFTEN THINK ABOUT FIVE MAIN SENSES --

SIGHT, HEARING, TASTE, SMELL, AND TOUCH,

BUT ACROSS THE NATURAL WORLD, SKIN HELPS ANIMALS

SENSE IN WAYS WE FIND HARD TO IMAGINE.

ANIMALS DETECT TOUCH IN VARYING DEGREES OF SENSITIVITY.

BUT SENSITIVE DOESN'T ALWAYS MEAN FRAGILE.

CROCODILES, ALLIGATORS, CAIMAN, AND GHARIALS

ARE COLLECTIVELY KNOWN AS CROCODILIANS.

THERE ARE 23 SPECIES

LIVING IN TROPICAL AREAS ACROSS THE WORLD.

AS ONE OF OUR PLANET'S MOST FORMIDABLE HUNTERS,

THEY SIT AT THE TOP OF THE FOOD CHAIN.

THEIR SKIN HAS AN INCREDIBLE SENSITIVITY

WHICH HAS GIVEN THEM THE EDGE OVER OTHER ANIMALS.

I'VE COME TO THE U.K.'s ONLY CROCODILIAN ZOO,

JUST OUTSIDE OXFORD, TO SEE SOME OF THEM UP CLOSE.

WHAT SPECIES DO WE HAVE IN HERE?

SO, THESE, THIS IS OUR BIG GROUP OF NILE CROCODILES.

WE'VE GOT 35 INDIVIDUALS IN THIS ENCLOSURE,

AND THEY'RE ALL QUITE YOUNG.

I MEAN, THEY GET MUCH BIGGER THAN THIS, DON'T THEY?

THEY DO.

THEY'RE ONE OF THE LARGEST SPECIES

OF CROCODILIAN THAT WE HAVE ON THE PLANET.

AND ADULT MALES CAN REACH LENGTHS OF UP TO FIVE METERS,

SO QUITE A LOT BIGGER THAN THIS.

THAT'S ME WITH YOU ON MY SHOULDERS

AND THEN A BIT MORE, ISN'T IT?YEAH.

SO, WHAT DO NILE CROCODILES EAT IN THE WILD?

WELL, THROUGH THEIR LIFE, THEY EAT DIFFERENT THINGS,

SO, THEY START OFF, WHEN THEY'RE HATCHLINGS,

EATING SMALL INVERTEBRATES, SMALL REPTILES, AMPHIBIANS,

FISH, THINGS LIKE THAT.

AND AS THE CROC GROWS,

THEIR PREY SIZE INCREASES, AS WELL.

I'M SUDDENLY FEELING LESS CONFIDENT STOOD NEAR THE EDGE,

'CAUSE THEY CAN JUMP, AS WELL, CAN'T THEY?

THEY CAN JUMP.

THE PERFECT APEX PREDATOR ON OUR PLANET.

IT'S TIME FOR THESE CROCODILES' MAIN MEAL --

CHICKEN ON A STICK.

[ Chuckling ] OH!

SO POWERFUL.

CROCODILIANS DIDN'T GET TO BE THE APEX PREDATORS THEY ARE

SIMPLY BY USING BRUTE FORCE.

THE REAL SECRET TO THEIR SUCCESS IS HIDDEN IN THEIR SKIN.

IN THE MURKY WATER WHERE THEY HUNT,

CROCODILES CAN'T ALWAYS RELY ON THEIR EYES.

SO, EMBEDDED IN NEARLY EVERY SINGLE SCALE ACROSS THEIR BODIES

ARE HIGHLY SENSITIVE PRESSURE RECEPTORS.

AND THESE ARE ABLE TO DETECT

THE SMALLEST OF RIPPLES IN THE WATER...

...MAKING IT POSSIBLE

TO JUDGE THE DISTANCE AND POSITION OF ANY ANIMAL

WITHOUT USING THEIR EYES.

THE SAFEST WAY TO SEE THESE SENSORY ORGANS UP CLOSE

IS ON A BABY ALLIGATOR.

SHAUN, THIS ONE'S MUCH SMALLER THAN EARLIER.

I FEEL MUCH HAPPIER BEING THIS CLOSE TO THIS LITTLE GUY.

BUT IT'S A DIFFERENT SPECIES, AS WELL, ISN'T IT?

YEAH, THIS ONE'S AN AMERICAN ALLIGATOR.

BUT IT'S A GOOD OPPORTUNITY TO REALLY HAVE A LOOK AT THE SKIN

AND SEE HOW IT WORKS AND ALSO HOW IT HELPS HIM HUNT.

YOU CAN SEE INSTANTLY, ON THE BACK, REALLY STRONG,

THICK SKIN, THAT REALLY ARMORED AREA,

BUT NOT THE SAME AROUND THE MOUTH.

YOU CAN SEE IT'S A DIFFERENT TYPE OF SKIN,

AND LOTS OF LITTLE SPOTS OR HOLES, REALLY.

THAT'S RIGHT.

ALL THOSE LITTLE BLACK DOTS AROUND THE JAW

ARE SENSORY ORGANS.

WHILE ALLIGATORS HAVE THESE PRESSURE RECEPTORS

JUST ON THEIR SNOUT,

CROCODILES HAVE THEM ALL OVER THEIR BODIES.

EACH ONE IS A MILLIMETER-LONG DOME ON THEIR SKIN,

COVERED BY A FLEXIBLE SCALE.

INSIDE ARE HUNDREDS OF NERVE FIBERS.

ANY MOVEMENT ON THE SURFACE OF THE SCALE IS PICKED UP

BY THE NERVE FIBERS UNDERNEATH.

IT'S BEEN ESTIMATED THAT EACH DOME IS

10 TIMES MORE SENSITIVE THAN A HUMAN FINGERTIP.

THEY'RE EFFECTIVELY SEEING, BUT WITHOUT THEIR EYES.

THEY'RE SEEING WHERE THESE VIBRATIONS ARE,

THEY'RE FEELING THESE VIBRATIONS,

AND THAT'S IN ORDER TO HUNT PREY, RIGHT?

THAT'S EXACTLY RIGHT, YEAH.

WE WANT TO SEE HOW THESE SKIN RECEPTORS WORK

BY SETTING UP A SIMPLE TEST INVOLVING OUR BABY ALLIGATOR.

THE TUBES ARE IN PLACE TO MAKE SURE

THE ALLIGATOR CAN'T SEE WHERE THE FOOD IS.

AND TO MAKE SURE IT CAN'T HEAR WHERE THE FOOD IS,

I'VE EVEN ADDED SOME WHITE NOISE.

[ WHITE NOISE WHOOSHES ]

I DROP SOME CHICKEN INTO ONE OF THE PIPES.

FILMED IN SLOW MOTION, AS THE CHICKEN HITS THE WATER,

IT CREATES SMALL RIPPLES.

THESE EXPAND OUT INTO THE POOL.

AND AS THEY TOUCH THE ALLIGATOR, IT TURNS.

THE MOMENT I DROPPED THE CHICKEN INTO THAT TUBE,

IT TURNED AND IT LOOKED,

AND IT DID COME THIS WAY A SECOND OR SO

AFTER THAT CHICKEN HIT THE WATER.

THAT COULD ONLY HAVE HAPPENED

IF IT FELT THE VIBRATIONS THROUGH ITS SKIN.

THIS HAS BEEN SHOWN IN EXPERIMENTS

UNDER LABORATORY CONDITIONS.

ITS SKIN IS SO SENSITIVE, THIS CROCODILE IS ABLE TO REACT

TO THE RIPPLE WITHIN A FRACTION OF A SECOND.

CROCODILIANS HAVE THE MOST POWERFUL JAWS

OF ANY LIVING ANIMAL.

BUT BY USING THE RECEPTORS IN THEIR SKIN,

THESE JAWS ALSO HAVE THE CAPACITY

TO BE SURPRISINGLY GENTLE.

AND THIS SENSITIVITY IS SOMETHING ALL CROCODILIANS HAVE

FROM THE MOMENT THEY HATCH.

THIS FEMALE CAIMAN'S OFFSPRING

ARE JUST EMERGING FROM THEIR EGGS.

[ CAIMANS SQUEAKING ]

HER YOUNG ARE FRAGILE

AND NEED HELP GETTING TO THE WATER.

TO PERFORM THIS KIND OF TASK,

SHE NEEDS A REAL LIGHTNESS OF TOUCH --

SOMETHING ONLY HER SKIN CAN PROVIDE.

LIKE CROCODILIANS, MANY ANIMALS USE THEIR SNOUTS

TO PERFORM ESSENTIAL TASKS.

THIS MAKES THE SKIN ON THE END OF ANY SNOUT

A PARTICULARLY IMPORTANT SENSORY TOOL.

HERE IN NORTH AMERICA LIVES THE STAR-NOSED MOLE.

AT THE END OF ITS SNOUT IS

ARGUABLY THE MOST SENSITIVE PATCH OF SKIN ON THE PLANET.

ITS NOSTRILS ARE SURROUNDED BY 22 FLESHY APPENDAGES

KNOWN AS RAYS.

THE SKIN ON THESE IS COVERED IN 25,000 SENSORY TOUCH RECEPTORS,

FIVE TIMES MORE THAN IN THE HUMAN HAND.

THE MOLE PATS IT TO THE GROUND 10 TO 15 TIMES A SECOND,

SEARCHING FOR A MEAL IN DARK TUNNELS.

IT'S SO SENSITIVE, THE MOLE CAN TELL WHAT'S EDIBLE

IN 227 MILLISECONDS,

FASTER THAN ANY OTHER MAMMAL.

BUT THESE SNOUTS ARE SENSITIVE IN MORE THAN ONE WAY.

THEY CAN ALSO SMELL UNDERWATER.

THE MOLE DOES THIS BY PARTIALLY EXHALING AN AIR BUBBLE

ON THE TOP OF ITS SNOUT.

THIS ABSORBS SURROUNDING ODORS,

WHICH IT BREATHES BACK IN TO SEE IF THERE'S FOOD NEARBY.

IF NOT, IT MOVES ON.

EVERY VERTEBRATE HAS A NETWORK OF NERVES

CONNECTED TO THEIR DERMIS AND EPIDERMIS,

THERE TO RELAY REAL-TIME INFORMATION

FROM ALL OVER THE SURFACE OF THE BODY.

[ CAT PURRING ]

THIS CAN BE A SOURCE OF PLEASURE

AND ACT AS A WARNING SYSTEM AGAINST ATTACKS.

FROM BITING INSECTS, FOR EXAMPLE.

[ HORSE NEIGHS ]

BUT REACTING TO WHAT YOUR SKIN IS TELLING YOU CAN BE TRICKY,

ESPECIALLY WHEN ALL FOUR OF YOUR LIMBS ARE ON THE GROUND.

SKIN IS PRETTY TOUGH,

AND IS GOOD AT PROTECTING US FROM THE OUTSIDE WORLD.

BUT WHEN IT COMES TO BITING INSECTS --

HELLO --

FOR ANIMALS SUCH AS HORSES, THERE ARE AREAS ON THEIR BODY

THEY JUST CAN'T REACH TO DISLODGE PESKY FLIES.

BUT HORSE SKIN HAS ADAPTED TO SOLVE THAT PROBLEM.

JUST BELOW THE SKIN AND THE SUBCUTANEOUS FAT LAYER

IS A THIN SHEET OF MUSCLE CALLED THE CUTANEOUS TRUNCI MUSCLE.

IT'S ANCHORED TO THE DERMIS WITH CONNECTIVE TISSUE,

AND SO ANY MOVEMENT IN THE MUSCLE PULLS THE SKIN WITH IT.

IMAGINE THIS FEATHER IS A FLY,

INTENT ON GETTING A MEAL OUT OF THE HORSE.

FLY LANDS...

AND WE SEE THAT.

NOW, THIS IS A FLINCH IN THE MUSCLE BENEATH THE SKIN.

AND IT'S THAT, THAT WHEN THE HORSE DOES IT,

DISLODGES THE FLY

OR ANY OTHER FLYING, BITING INSECT

THAT WOULD OTHERWISE CAUSE A NUISANCE.

THIS IS AN INVOLUNTARY REACTION.

SENSATION ON THE SKIN TRAVELS THROUGH NERVES,

VIA THE SPINAL CORD, TO THE MUSCLE,

WITHOUT ENGAGING THE HORSE'S BRAIN AT ALL.

USING TOUCH IS CERTAINLY ONE OF THE MOST EFFECTIVE WAYS

OF GETTING A SENSE OF AN OBJECT OR ENVIRONMENT.

BUT ONE GROUP OF ANIMALS HAS ADAPTED THEIR SKIN

TO HELP GATHER INFORMATION FROM A DISTANCE.

VIRTUALLY ALL OF THE 1,300 OR SO SPECIES OF BAT

AROUND THE WORLD ARE NOCTURNAL.

IN ORDER TO NAVIGATE AT NIGHT,

MANY OF THEM EMIT HIGH-FREQUENCY SOUND WAVES

FROM EITHER THEIR NOSE OR MOUTH, BOUNCING THEM OFF NEARBY OBJECTS

TO GET A SENSE OF WHAT'S AROUND THEM --

A SYSTEM CALLED ECHOLOCATION.

BUT IN THE DENSE FORESTS OR CAVES WHERE THEY OFTEN LIVE,

THIS CAN CAUSE A PROBLEM.

WHEN FLYING AROUND A FOREST,

YOU NEED TO BE ABLE TO FOCUS ON WHAT'S AHEAD,

ESPECIALLY IF YOU WANT TO AVOID CRASHING INTO A TREE.

IF YOU WERE TO MAKE A WIDE ECHOLOCATION BEAM,

LIKE THE WIDE BEAM OF THIS TORCH,

THEN YOU'D BE GENERATING TOO MUCH INFORMATION,

WHICH WOULD BE BOUNCING BACK FROM SURROUNDING OBJECTS.

AND FOR A BAT, THIS RISKS BEING OVERWHELMING AND CONFUSING.

MANY BATS HAVE ADAPTED TO OVERCOME THIS SENSORY PROBLEM,

BUT ONE GROUP HAS FOUND A WAY TO ENHANCE THEIR ECHOLOCATION

BY USING THE SKIN ON THEIR FACES,

LIKE THIS PALE SPEAR-NOSED BAT.

IT EMITS ITS ECHOLOCATION BEAM FROM ITS NOSE.

AND IF YOU LOOK, THIS BIZARRE STRUCTURE

ON THE FRONT OF THE FACE, JUST HERE,

IS CALLED THE NOSE-LEAF.

THE NOSE-LEAF IS MADE OF SKIN AND CARTILAGE.

AND BY ADJUSTING ITS SHAPE,

THE BATS CAN MANIPULATE THE SIZE OF THEIR ECHOLOCATION BEAM.

THIS GIVES THEM THE ABILITY TO FOCUS THEIR ECHOLOCATION,

TRANSFORMING A WIDE AND DIFFUSE BEAM

INTO A NARROW AND MORE FOCUSED ONE.

ALL BATS FROM THE NOSE-LEAF AND HORSESHOE BAT FAMILIES

HAVE THIS ABILITY.

BY DIRECTING A MORE FOCUSED BEAM,

THEY ARE ABLE TO CONCENTRATE

ON THE OBJECTS THAT REALLY MATTER --

IMPORTANT WHEN IT COMES TO AVOIDING TREES

AND CRUCIAL FOR HOMING IN ON FOOD.

HOWEVER, THE INFORMATION

ANIMALS ARE ABLE TO GATHER USING THEIR SKIN

ISN'T ALWAYS RELATED TO THEIR NEXT MEAL.

THE SENSITIVITY OF AN ANIMAL'S SKIN

CAN DIRECTLY INFLUENCE HOW THEY INTERACT WITH THE WORLD.

IN FACT, A SMALL PATCH OF SKIN FOUND ON SOME ANIMALS

HAS ARGUABLY HAD MORE OF AN IMPACT ON OUR PLANET

THAN ANY OTHER.

SOME OF THE MOST SENSITIVE SKIN IS FOUND ON OUR FINGERTIPS,

GIVING THEM A HEIGHTENED SENSE OF TOUCH.

THE SKIN ON EACH FINGERTIP CAN DETECT RIDGES

4,500 TIMES SMALLER THAN A HUMAN HAIR.

THIS SENSITIVITY GIVES OUR 10 DIGITS

THE POWER TO GRIP, FEEL, BUILD, CRAFT, AND EVEN READ --

ABILITIES THAT ARE REMARKABLE,

BUT WHICH WE OFTEN TAKE FOR GRANTED.

IN ORDER TO FULLY EXPLORE

JUST HOW OUR SENSE OF TOUCH REALLY WORKS,

WE DON'T NEED A BIOLOGIST, WE NEED AN ENGINEER.

PROFESSOR NATHAN LEPORA MAKES ROBOTS

THAT MIMIC THE HUMAN SENSE OF TOUCH --

RESEARCH THAT SHEDS LIGHT ON THE COMPLEXITY OF OUR SKIN.

HI, NATHAN. HI, BEN.

HOW ARE YOU?NICE TO MEET YOU.

YEAH, YOU TOO. WHAT HAVE WE ACTUALLY GOT HERE?

I CAN SEE CABLES AND I CAN SEE THE BIG BLACK DOME HERE.

WHAT IS THIS?THIS DOMELIKE STRUCTURE IS,

IF YOU LIKE, A VERSION OF OUR FINGERTIP.

AND WHAT HAPPENS IF YOU TOUCH THE FINGERTIP NOW?

GO AHEAD.

AH.

SO, WHAT I'M SEEING, I'M DISPLACING

THOSE LITTLE LUMPS AND BUMPS.YEAH.

THEIR MOVEMENT GIVES INFORMATION ABOUT THE CONTACT ON THE SKIN.

ENGINEERS HAVE BEEN TRYING

TO REPLICATE OUR SENSE OF TOUCH FOR DECADES.

AND THESE BUMPS ON THE INSIDE OF NATHAN'S ARTIFICIAL FINGERTIPS

MIMIC HOW ACTUAL FINGERTIPS WORK.

WHEN YOU TOUCH SOMETHING,

MOVEMENT ON THE SURFACE OF YOUR SKIN

IS PICKED UP BY SENSORS IN YOUR DERMIS AND EPIDERMIS.

CALLED MECHANORECEPTORS,

THESE SEND A SIGNAL VIA NERVES TO YOUR BRAIN.

THERE ARE ABOUT 200 MECHANORECEPTORS

PER SQUARE CENTIMETER IN THE TIPS OF YOUR FINGERS.

AND INSIDE THE ROBOTIC FINGERTIP,

A SMALL CAMERA DOES THIS JOB

BY DETECTING THE MOVEMENT OF THE BUMPS.

IT TRANSMITS THAT FEELING, THAT SENSITIVITY, THAT IMPACT,

THROUGH TO A CENTRAL PROCESSING AREA.

NOT THE BRAIN, BUT THE LAPTOP.EXACTLY.

IN THIS CASE, IT USES VISION AND IMAGE,

WHEREAS IN OUR FINGERTIPS, WE HAVE NERVES

WHICH SEND THAT INFORMATION TO THE BRAIN.

I'M TOUCHING THAT SO GENTLY,

AND YOU CAN SEE ON YOUR SCREEN WHERE IT'S MOVING.

THAT'S INCREDIBLE. IT REALLY IS.

MOST ROBOTS ARE PRE-PROGRAMMED TO DO THE TASKS THEY PERFORM,

BUT NATHAN'S TECHNOLOGY MEANS THAT THE ROBOTS OF THE FUTURE

WILL BE ABLE TO REACT INTELLIGENTLY

TO THE WORLD AROUND THEM.

THIS ROBOT IS GOING TO USE ITS OWN SENSE OF TOUCH

TO FEEL OVER THAT QUITE DELICATE PORCELAIN HEAD

THAT I BORROWED FROM MY WIFE.

NOW, THAT'S AN ESSENTIAL SKILL TO HAVE WITH OUR TOUCH,

'CAUSE WE USE THAT TO FEEL THE SHAPE OF OBJECTS

WHEN WE PICK OBJECTS UP OR TO RECOGNIZE OBJECTS.

THE SENSITIVITY OF THE MECHANORECEPTORS IN OUR SKIN

MEANS OUR FINGERS CAN EASILY TRACE AN OBJECT

WHILE APPLYING CONTINUOUS PRESSURE.

BUT THIS IS ACTUALLY A HIGHLY COMPLICATED TASK.

AND THIS HASN'T BEEN PRE-PROGRAMMED AT ALL, HAS IT?

Lepora: NO, IT'S COMPLETELY AUTONOMOUS.

IT'S FIGURING IT OUT FOR ITSELF AS IT MOVES OVER THE HEAD.

NATHAN KNOWS THAT, IN ORDER TO BE USEFUL,

THESE ARTIFICIAL FINGERTIPS NEED TO BE INCREDIBLY SENSITIVE.

SO HE'S ADAPTED HIS FINGERTIP DESIGN

TO MAKE A ROBOT HAND WITH A SENSE OF TOUCH.

I'LL SHOW YOU ANOTHER EXPERIMENT NOW WHERE WE'LL GET THE HAND

TO PICK UP A VERY DELICATE OBJECT --

THIS ORIGAMI CRANE...[ Chuckling ] RIGHT.

...WITHOUT CRUSHING IT.

HERE IT GOES.

AS THE ROBOT'S FINGERS COME INTO CONTACT WITH THE CRANE,

IT SENSES HOW MUCH PRESSURE TO APPLY

WITHOUT BENDING THE PAPER --

SOMETHING WE CAN DO INSTINCTIVELY

USING THE MECHANORECEPTORS IN OUR SKIN.

OH, LOOK. YEP.

SEE, IT HASN'T EVEN SQUEEZED THE HEAD IN THAT MUCH.

IT'S BARELY TOUCHING IT. I MEAN, THAT --

THAT MUST BE SO SENSITIVE.

THAT'S SO IMPRESSIVE.

IT'S BASICALLY THE LIGHTEST POSSIBLE GRASP IT CAN DO

AND STILL HAVE ENOUGH SECURITY TO HOLD THE CRANE.

THERE MUST BE SO MANY APPLICATIONS

FOR THIS IN THE FUTURE.

WELL, THERE'S A FEW PRESSING NEEDS

FOR THIS TYPE OF TECHNOLOGY -- PROSTHETIC HANDS.

SO, WITH THIS KIND OF TECHNOLOGY,

YOU COULD, IN PRINCIPLE, EMBED TACTILE SENSORS

WITHIN THE PROSTHETIC HAND AND RESTORE A SENSE OF TOUCH

IF YOU WERE ABLE TO CONNECT IT UP TO THE HUMAN NERVOUS SYSTEM.

ENDLESS POSSIBILITIES.YEAH, EXACTLY.

THERE REALLY ARE.

FINDING FOOD IS HIGH ON EVERYONE'S LIST OF PRIORITIES.

BUT WHEN YOUR FOOD DOESN'T WANT TO BE FOUND,

HAVING SHARP SENSES CAN MAKE ALL THE DIFFERENCE.

AND ONE HUNTER'S SKIN HAS ADAPTED

TO GIVE IT A MASSIVE ADVANTAGE,

BECAUSE IT IS ABLE TO SENSE ELECTRICITY.

THIS AMAZING PIECE OF BIOLOGY IS THE SNOUT OF A SAWFISH.

WE CALL IT ITS ROSTRUM.

YOU CAN SEE THESE PROJECTIONS ALL THE WAY ALONG.

THEY'RE MADE OF THE SAME STUFF AS THINGS LIKE HUMAN TEETH,

BUT THEY'RE NOT QUITE TEETH IN THE TRADITIONAL SENSE.

HOWEVER, WHAT'S AMAZING ABOUT THE ROSTRUM OF A SAWFISH

IS THAT NOT ONLY IS IT A DEADLY WEAPON,

BUT IT CAN ALSO DETECT MINUTE ELECTRICAL IMPULSES.

SADLY, SAWFISH ARE CRITICALLY ENDANGERED,

AND SO ARE RARELY SEEN IN THE WILD.

THE SMALL FISH AND SHRIMP THAT THEY LIKE TO FEAST ON

MIGHT TRY AND STAY HIDDEN.

BUT, LIKE ALL FISH, THEY GIVE OFF TINY ELECTRIC CHARGES,

CREATING INCREDIBLY WEAK ELECTRIC FIELDS.

AND THESE ARE A DEAD GIVEAWAY.

ON THE UNDERSIDE OF THIS SAWFISH ROSTRUM

ARE THOUSANDS OF TINY LITTLE PORES IN THE SKIN.

AND IF WE WERE TO PEER INSIDE ONE OF THESE LITTLE PORES,

THEN YOU'D SEE A TINY SENSORY ORGAN

CALLED AN AMPULLA OF LORENZINI.

NAMED AFTER THE 17th-CENTURY ITALIAN PHYSICIAN,

THE AMPULLAE OF LORENZINI CONSIST OF A NARROW TUNNEL

IN THE DERMIS, FILLED WITH A CONDUCTIVE JELLY.

AT THE END IS A ROUND STRUCTURE CALLED AN AMPULLARY BULB,

CONTAINING ELECTROSENSITIVE CELLS.

AND THESE ARE ABLE TO PICK UP WEAK ELECTRICAL SIGNALS --

SOMETHING AS FAINT AS ONE BILLIONTH OF A VOLT.

THE SAWFISH IS ABLE TO SWIM CLOSE TO THE SEABED,

WHERE IT USES ITS ROSTRUM TO FORAGE FOR PREY.

AND WHEN IT DETECTS SOMETHING LIKE A SHRIMP OR SMALL FISH,

IT'LL USE ITS ROSTRUM TO DISLODGE IT BEFORE EATING IT.

BUT SAWFISH HAVE A SECOND SENSORY ABILITY

HIDDEN IN THEIR SKIN --

ONE THEY SHARE WITH EVERY SINGLE FISH ON THE PLANET.

IN THE SOUTHERN PACIFIC OCEAN, A TORNADO IS FORMING.

IT ISN'T MADE OF SWIRLING AIR, BUT MILLIONS OF FISH.

THIS IS A BAIT BALL, A VAST SCHOOL OF FISH

THAT MOVES AS ONE WHEN THREATENED BY PREDATORS.

THEY ARE ABLE TO REACT IN UNISON TO ANY DANGER,

AT LIGHTNING SPEED,

SPLITTING AND RE-FORMING BEHIND ONCOMING STRIKES.

GATHERING TOGETHER LIKE THIS HELPS TO INTIMIDATE

AND CONFUSE POTENTIAL ATTACKERS.

THEIR EYES HELP TO JUDGE THE POSITION OF THEIR NEIGHBORS,

BUT MOVING WITH THIS LEVEL OF PRECISION IS MADE FAR EASIER

BY A SPECIAL SENSORY SYSTEM IN THEIR SKIN

CALLED THE LATERAL LINE.

MADE FROM A SERIES OF CANALS RUNNING THE LENGTH OF THE BODY,

THE LATERAL LINE IS FILLED WITH A JELLYLIKE SUBSTANCE

AND LINKS TO THE SURROUNDING ENVIRONMENT

BY A NETWORK OF PORES.

THE WATER FROM OUTSIDE MOVES THROUGH THE PORES,

STIMULATING TINY HAIRLIKE STRUCTURES

IN THE WALLS OF THE CANALS, CALLED NEUROMASTS.

ALL FISH USE THE LATERAL LINE TO SENSE PRESSURE CHANGES

IN THE WATER AROUND THEM,

ALLOWING THEM TO PERCEIVE THE SMALLEST OF MOVEMENTS

ALL THE WAY AROUND THEIR BODIES

AND ENABLING THEM TO MAINTAIN A CONSTANT DISTANCE

FROM THE OTHER FISH ON EITHER SIDE.

SCIENTISTS THINK THIS HELPS FISH TO MIGRATE

IN HUGE SCHOOLS, LIKE THESE SARDINES.

AS WITH ALL FISH, THEY RELY ON

THEIR ENHANCED PERCEPTION THEY GET FROM THEIR SKIN.

IN THE FORESTS OF SOUTHEAST ASIA,

ONE ANIMAL IS USING ITS SKIN

TO PLAY A FAR MORE CLANDESTINE GAME OF CAT AND MOUSE.

THIS IS AN ASIAN PIT VIPER.

IT'S AN AMBUSH PREDATOR.

IT WAITS MOTIONLESS ON BRANCHES FOR SMALL ANIMALS TO APPROACH.

TO HUNT IN THIS WAY, IT RELIES ON AN INCREDIBLE SENSORY ABILITY

HIDDEN IN ITS SKIN.

JASON SKINNER IS AN EXPERT SNAKE HANDLER.

WHAT A BEAUTIFUL SNAKE. HE'S GORGEOUS, JASON, ISN'T HE?

Skinner: YEAH, GREAT COLORS.

THESE SNAKES HUNT AT NIGHT,

AND THEY DO SO USING SPECIALIZED PITS IN THEIR SKIN,

LOCATED BETWEEN THEIR EYES AND THEIR NOSTRILS.

THESE PITS ARE SO SENSITIVE, THEY ARE ABLE TO PICK UP

THE TINY HEAT SIGNATURE LEFT BY THEIR PREY IN PITCH DARK.

INSIDE EACH PIT IS A MEMBRANE

WHICH HEATS UP WHEN HIT BY INFRARED RADIATION,

LIKE THAT EMITTED BY A WARM RODENT.

THIS HEAT IS CONVERTED INTO ELECTRIC SIGNALS

WHICH ARE SENT TO THE SNAKE'S BRAIN.

PIT VIPERS, PYTHONS, AND BOA CONSTRICTORS

ALL HAVE THIS ABILITY.

AND WE'RE GOING TO TEST JUST HOW SENSITIVE

THESE HEAT-SENSING PITS REALLY ARE.

OKAY, JASON. WHAT HAVE WE GOT HERE?

SO, WE'VE GOT TWO PING-PONG BALLS

ATTACHED TO THESE THREE-FOOT CANES.

[ Chuckling ] RIGHT.

SO WE'RE WELL OUTSIDE THE STRIKING RANGE.

GOOD.

THE PING-PONG BALLS ARE IDENTICAL,

APART FROM ONE CRUCIAL DIFFERENCE.

ONE IS FILLED WITH COLD WATER, THE OTHER WITH WARM.

AND I'VE GOT THE WARM ONE?YES.

OOH, YEAH. YEP.

IF DANGLED IN FRONT OF HIM AT EQUAL DISTANCES,

WILL OUR VIPER BE ABLE TO TELL WHICH IS WHICH?

I'M QUITE NERVOUS, JASON.

I'M NOT GOING TO LIE. [ GULPS ]

EW! [ CHUCKLES ]

AND HE DID! [ CHUCKLES ]

OH. [ CHUCKLES ]

THAT WAS INCREDIBLY QUICK, THOUGH.

THAT WAS SUCH A STRIKE.YEAH.

INSTANTLY, HE WENT FOR THE WARMER ONE.

YEAH.

THERE WAS A VERY DEFINITE RESPONSE THERE.

THE HEAD TURNED AWAY FROM YOURS.

YOURS WAS MOVING AS MUCH AS MINE.

AND IT'S AS CLOSE. YEAH.

THERE'S A VERY DEFINITE PREFERENCE THERE.

EVEN AT NIGHT,

WHEN THE PIT VIPER CAN'T BE SEEN BY ITS PREY,

IT CAN STILL DETECT THEM.

AND WHEN THEY COME WITHIN STRIKING RANGE...

HE DEFINITELY MADE HIS CHOICE.

[ LAUGHS ]

...ONE THING IS CLEAR.

IF THE PING-PONG BALL WAS A MOUSE,

IT WOULDN'T STAND A CHANCE.

SKIN IS CLEARLY ONE OF THE MOST DYNAMIC ORGANS ON THE PLANET

AND A CRUCIAL PART OF EVERY ANIMAL'S SENSES.

WE OFTEN TAKE SKIN FOR GRANTED,

YET WE'VE SEEN THAT IT GOES WAY BEYOND A SIMPLE BARRIER

BETWEEN US AND THE OUTSIDE WORLD.

AND WHAT FASCINATES ME MOST ABOUT SKIN IS

THAT WE STILL HAVE SO MUCH MORE TO FIND OUT.

--Captions by VITAC-- www.vitac.com

CAPTIONS PAID FOR BY DISCOVERY COMMUNICATIONS