Original subtitles

♪♪

Garrod: 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 IT'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 HAIR ON 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 EXTRA-SENSORY ABILITIES.

WE'RE EVEN DISCOVERING THE COMPLEX ECOSYSTEM

LIVING ON OUR SKIN.

JIM, THAT'S AWFUL.

IT REALLY IS.

IN THIS EPISODE, I'LL LEARN WHY RHINOS

HAVE THE MOST HEAVILY-ARMORED SKIN OF ANY LIVING MAMMAL...

[ RHINO GROWLS ]

...WHY THE SMALLEST PORCUPINE QUILLS

ARE OFTEN THE MOST DANGEROUS...

♪♪

...AND DISCOVER WHY CUTTLEFISH CAMOUFLAGE IS TRANSFORMING

THE WAY SCIENTISTS THINK ABOUT SKIN...

♪♪

...TO DELVE INTO THE INGENIOUS WAYS

SKIN DEFENDS ANIMALS FROM PHYSICAL ATTACKS.

♪♪

I'M GOING TO REVEAL THE SECRETS OF SKIN.

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

CAPTIONS PAID FOR BY DISCOVERY COMMUNICATIONS

THIS IS A MEMBER OF ONE OF THE MOST TOXIC GROUPS

OF ANIMALS ON THE PLANET.

♪♪

SHE'S A YELLOW-BANDED POISON DART FROG.

THESE TINY FROGS SECRETE A VERY POTENT POISON

THROUGH THEIR SKIN.

DIRECT CONTACT WITH SOME SPECIES

CAN CAUSE NAUSEA, PARALYSIS...

AND EVEN DEATH.

♪♪

THERE ARE ALMOST 200 KNOWN SPECIES OF POISON DART FROG

IN THE FORESTS OF CENTRAL AND SOUTH AMERICA.

EACH ONE COMBINES TOXIC SKIN WITH VIVID COLORS,

AND THE MORE TOXIC A SPECIES,

THE BRIGHTER COLORS IT HAS EVOLVED.

A SINGLE GOLDEN POISON DART FROG

HAS ENOUGH POISON IN ITS SKIN TO KILL 10 PEOPLE,

MAKING IT THE MOST TOXIC ANIMAL ALIVE.

THESE BRIGHT COLORS ARE A STARK WARNING FOR PREDATORS

TO BACK OFF.

BUT IF A HUNGRY BIRD DOES DECIDE TO IGNORE THIS WARNING

AND TAKES A NIBBLE,

THEN IT WON'T BE MAKING THAT MISTAKE AGAIN.

EACH FROG SPECIES DEPLOYS A DIFFERENT RANGE OF TOXINS,

BUT THEY ALL BELONG TO A GROUP OF CHEMICALS CALLED ALKALOIDS.

THE FROGS DON'T MAKE THESE TOXINS FROM SCRATCH.

THEY'RE DERIVED FROM DEFENSIVE CHEMICALS IN THE ANTS, BEETLES,

AND MILLIPEDES THEY EAT.

THE TOXINS ARE STORED IN GLANDS IN THE DERMIS

AND RELEASED ONTO THE SURFACE VIA PORES.

POISON DART FROGS ARE ACTIVE DURING THE DAY

WHEN PREDATORS CAN SPOT THEIR WARNING COLORS AND AVOID THEM.

MOST OTHER FROG SPECIES TEND TO COME OUT AT NIGHT.

THESE FROGS GOT THEIR NAME BECAUSE THEIR TOXINS WERE ONCE

USED BY FOREST HUNTERS TO TIP THEIR DARTS.

TODAY, WE'RE FINDING OTHER USES FOR THEM.

NOW SCIENTISTS ARE STUDYING THE DEADLY CHEMICALS

THESE FROGS DEPLOY

IN ORDER TO DESIGN NEW PAINKILLING DRUGS AND MEDICINES.

ONE TOXIN, EPIBATIDINE, ATTACKS NERVES,

CAUSING NUMBNESS AND PARALYSIS.

RESEARCHERS HOPE

THAT BY UNPICKING EPIBATIDINE'S STRUCTURE AND CHEMISTRY,

THEY MAY BE ABLE TO SEPARATE ITS BENEFICIAL PAINKILLING EFFECTS

FROM ITS DEADLY TOXICITY.

RIGHT, YOU.

BACK IN YOUR TANK.

♪♪

NOW, YOU MIGHT THINK THIS IS A VERY SILLY THING TO DO.

BUT CAPTIVE BRED DART FROGS...

AREN'T TOXIC AT ALL.

♪♪

FROGS BRED IN CAPTIVITY ARE FED HARMLESS INSECTS

LIKE FRUIT FLIES, WHICH MEANS THEY NEVER GO ON

TO DEVELOP THE DANGEROUS TOXICITY

OF THEIR WILD RELATIVES.

♪♪

WHAT WE STILL DON'T FULLY UNDERSTAND

IS HOW WILD FROGS CAN EAT AND STORE THESE TOXIC COMPOUNDS

WITHOUT COMING TO HARM.

A POISON DART FROG'S SKIN IS A WEAPON AND A WARNING.

THIS IS JUST THE START OF THE EXTRAORDINARY WAYS

ANIMALS USE THEIR SKIN TO DEFEND THEMSELVES.

ONE ANIMAL IS INFAMOUS FOR THE WARNING SOUND IT MAKES

WITH A SPECIALIZED PART OF ITS EPIDERMIS.

[ RATTLE]

THIS IS A RATTLESNAKE'S RATTLE.

♪♪

IT'S MADE FROM THE FINAL FEW SCALES

THAT COVER THE TIP OF THE SNAKE'S TAIL.

THEY FORM A SERIES OF HOLLOW

INTERLOCKING SEGMENTS OF KERATIN.

THE SAME PROTEIN AS MY HAIR AND NAILS.

THE SEGMENTS AREN'T FUSED TO ONE ANOTHER.

THEY'RE FREE TO MOVE.

SO IF I GIVE THIS LITTLE STRUCTURE A GOOD SHAKE...

[ RATTLE ]THE INTERLINKED CAPSULES

RATTLE AGAINST ONE ANOTHER.

RATTLESNAKES SHAKE THEIR RATTLES TO PRODUCE A LOUD BUZZ.

THIS ALERTS LIVESTOCK AND PREDATORS

THAT THERE'S A VENOMOUS SNAKE NEARBY

THAT WANTS TO AVOID TROUBLE.

[ RATTLING ]

NOW, I CAN MANAGE...[ RATTLING ]

COUPLE OF RATTLES A SECOND.

THAT'S NOT REALLY ENOUGH TO GRAB ANYONE'S ATTENTION.

TO SEE HOW A RATTLESNAKE USES THE KERATIN

ON THE TIP OF ITS TAIL

AS A BRILLIANT DEFENSE MECHANISM,

I NEED TO FIND A WAY TO SHAKE IT MUCH FASTER.

♪♪

I'M VISITING AN ENGINEERING LAB

TO GET HELP FROM THE REASSURINGLY TITLED

LECTURER IN NON-DESTRUCTIVE TESTING, DR ROB HUGHES.

HEY, ROB. WHAT HAVE WE GOT HERE?

HOW ARE WE GOING TO TEST THIS?

SO, HERE WE HAVE A VIBRATION STAGE.

NOW, THIS WORKS IN THE SAME WAY THAT A STEREO SPEAKER DOES,

SO WE CAN, THEREFORE, ESSENTIALLY

EXCITE SOMETHING UP AND DOWN AT WHATEVER FREQUENCY WE WANT.

WE DO THAT USING THIS FUNCTION GENERATOR HERE,

THROUGH AN AMPLIFIER, TO THEN GET SENT TO THE SPEAKER.

USING ROB'S SETUP, WE'LL BE ABLE TO SHAKE

THE RATTLE MUCH FASTER THAN I COULD DO IT MYSELF.

THIS WILL ALLOW US TO FIND THE RIGHT SPEED

TO GET THE BEST SOUND OUT OF THESE KERATIN CAPSULES.

I THOUGHT WE'D START OUT BY MOVING IT

AT FIVE TIMES PER SECOND.

THAT'S 5 HERTZ.

SO, IF WE SEND THE IMPULSE SIGNAL IN AND START VIBRATING --

YOU CAN SEE THAT NOT MUCH IS REALLY HAPPENING.

BUT WHAT WE CAN DO IS CYCLE THROUGH THE FREQUENCIES,

INCREASING THE PITCH.

OKAY. UM, SO...

[ TAPPING SPEEDS UP ]

SO THIS IS 10 HERTZ, SO 10 TIMES A SECOND.

AND THEN WE'RE GOING TO RAMP UP WITH MORE NOW.

SO WE'LL GO TO 20.[ RATTLING SLOWLY ]

OH, IT ALREADY...

STARTING TO SOUND LIKE IT....SOUNDS LIKE A RATTLESNAKE,

BUT IT DOESN'T SOUND LIKE AN ANGRY RATTLESNAKE JUST YET.

THAT'S A SLIGHTLY DISGRUNTLED SNAKE.

DEPENDS HOW ANGRY YOU WANT IT TO BE.

THIS IS 30 HERTZ.

40 HERTZ.OH, IT'S GETTING THERE.

AND 50 HERTZ.

[ HUMMING, RATTLING ]

OKAY, IT LOOKS LIKE A RATTLE FROM A RATTLESNAKE NOW,

THAT WEIRD, DISJOINTED, CHAOTIC RATTLE.

BUT THAT SOUND -- OH, IT MAKES

THE HAIR ON THE BACK OF YOUR NECK GO UP, DOESN'T IT?

YEAH.

WITH THE CLAMP VIBRATING AT 50 TIMES A SECOND,

REPLICATING THE ACTION OF SPECIALIZED TAIL-SHAKER MUSCLES,

THE FRAGILE CAPSULES OF SKIN REACH THEIR FULL POTENTIAL.

THE WARNING IS LOUD AND CLEAR.

IT'S DONE ITS JOB. THERE IS ABSOLUTELY NO DOUBT RIGHT NOW

THAT IF I HEARD THAT IN THE WILD,

I'D BE STEPPING AWAY.

THAT'S A RATTLESNAKE TO ME.

♪♪

WHILE A RATTLER'S NOISY WARNING

HELPS KEEP HUNTER AND HUNTED APART,

SOME ANIMALS' SKIN DEFENSES ARE SHAPED BY CLOSE CONTACT.

[ RHINO GROWLS ]

RHINOS ARE SOME OF THE BIGGEST ANIMALS ON THE PLANET,

REACHING AT LEAST A TON IN WEIGHT.

THEY ALSO HAVE THE MOST HEAVILY-ARMORED SKIN

OF ANY LIVING MAMMAL.

♪♪

THICK ARMOR, UP TO 4 CENTIMETERS IN PLACES,

COMBINED WITH A HUGE BODY SIZE

AND A TOP SPEED OF 50 KILOMETERS PER HOUR,

MAKES THEM ALL BUT INVULNERABLE TO PREDATORS.

♪♪

OF THE THREE SPECIES LIVING IN ASIA

AND TWO LIVING IN AFRICA, THE AFRICAN WHITE RHINO

IS THE LARGEST AND BEST-DEFENDED OF ALL.

I'VE COME TO SEE THIS ARMORED SKIN CLOSE-UP

WITH THE HELP OF RHINO KEEPER MARK GODWIN.

♪♪

Garrod: MARK, HE'S BLOWN ME AWAY.

THIS GUY IS HUGE!

LOOK AT HIM. WHAT'S THIS ONE'S NAME?

THIS IS MONTY. HE'S ABOUT 3 1/2 TON.

AND I'M GONNA SAY HE'S OVER 6 FOOT TO THE SHOULDER.

IF YOU WANT TO HAVE A STROKE, FEEL FREE.

OKAY, I CAN INSTANTLY FEEL THERE'S NO GIVE HERE.

THIS SKIN IS -- I MEAN, IT'S COVERED IN MUD,

BUT THIS IS INCREDIBLY TOUGH SKIN.

IT REALLY IS.

DO WE KNOW HOW THICK THIS SKIN CAN BECOME ON MONTY?

IT'S SUPPOSED TO BE ABOUT TO 1 1/2 INCH THICK.

SO YOU'RE TALKING, WHAT'S THAT, 4 CENTIMETERS OF SKIN THERE.

THAT IS AN IMPRESSIVE ANIMAL.

WITH AN EPIDERMIS OF ONLY ABOUT 1 MILLIMETER THICK,

MONTY'S SKIN GETS ITS STRENGTH AND THICKNESS

FROM DENSELY-PACKED LAYERS

OF COLLAGEN FIBERS IN THE DERMIS.

NOW, IN THE WILD, I CAN'T IMAGINE

EVEN THE MOST DETERMINED BUNCH OF LIONS

AND HYENAS ARE GOING TO TRY AND TAKE MONTY DOWN.

HIS MAIN THREAT, REALLY, IS OTHER RHINOS.

SO MOST OF THE ARMAMENT AND THAT IS FOR DEALING WITH OTHER BULLS

WHEN THEY COME INTO CONTACT OVER FEMALES.

RHINOS CHARGE EACH OTHER, USING THEIR HORNS AS BATTERING RAMS

IN BATTLES OVER TERRITORY AND MATING.

RESEARCHERS BELIEVE THIS AGGRESSIVE BEHAVIOR

HAS DRIVEN THE EVOLUTION OF THE RHINO'S THICK ARMOR.

IT'S FAR TOUGHER THAN IT NEEDS TO BE

TO SIMPLY FEND OFF PREDATORS.

♪♪

EVEN IF YOU JUST LOOK AT THE WAY THE LEGS ARE FORMED --

THE FRONT LEGS ARE VERY HEAVY,

SO IT'S ALL PROTECTION AROUND THE FRONT.

THEY TEND TO LIKE TO FACE THEIR PROBLEMS,

SO, THEREFORE, THAT'S WHERE THE THICKER, DENSER SKIN DEVELOPS.

IT'S HELPING HIM GET TERRITORY,

HELPING HIM BE A BIG, DOMINANT BULL,

JUST BY THE THICKNESS OF THE SKIN.

WHILE ADULT RHINOS ARE PROTECTED AGAINST ALL-COMERS

BY THEIR THICK ARMOR,

IT'S A DIFFERENT STORY FOR CALVES.

MARK, THESE ARE LOVELY. WHO HAVE WE GOT HERE?

THIS IS RUBY, AND THE LITTLE ONE'S STELLA.

SHE'S ABOUT 10 WEEKS OLD NOW COMING UP.

AND I GUESS BEING THIS SMALL AND HAVING SKIN

THAT'S, WELL, NOWHERE NEAR AS THICK AS MUM'S,

SHE'S, IN THE WILD, VULNERABLE.DEFINITELY.

AND THAT'S WHY THE MUMS ARE AS POSSESSIVE AS THEY ARE.

ONCE THEY GET TO FULL SIZE, REALLY NOT MUCH CAN TOUCH THEM,

BUT WHEN THEY'RE THIS SIZE AND SEPARATED FROM MUM,

THEY'RE VERY MUCH AT RISK.

STELLA'S SKIN IS PROBABLY ABOUT A CENTIMETER THICK,

AND WHILE THAT'S FIVE TIMES THICKER

THAN A 10-WEEK-OLD HUMAN BABY'S,

IT'S NOWHERE NEAR THICK ENOUGH TO PROTECT HER FROM PREDATORS,

SO RHINO MOTHERS HAVE TO BE VIGILANT.

WHAT SORT OF PREDATORS WOULD HAVE A GO

AT A BABY RHINO LIKE STELLA IN THE WILD?

LIONS, HYENAS.

IT WOULD HAVE TO BE THE BIG ONES OR ORGANIZED ONES.

THEY'D HAVE TO DEAL WITH MUM, AS WELL.

YEAH.OBVIOUSLY, WHILE SHE'S WITH MUM,

SHE'S VERY WELL PROTECTED,

BUT IF ANYTHING HAPPENED, SHE GOT SEPARATED,

SHE REALLY WOULD BE AT THE MOST VULNERABLE.

IT'S AN INCREDIBLY RARE EVENT AND EVEN MORE RARELY WITNESSED,

BUT PREDATORS THAT HUNT IN GROUPS, LIKE HYENAS OR LIONS,

ARE THE ONLY ANIMALS THAT WILL EVEN ATTEMPT

TO TACKLE A RHINO MOTHER AND CALF.

♪♪

IT TAKES AROUND TWO YEARS FOR A RHINO CALF

TO GROW THICK-ENOUGH SKIN

AND A BIG-ENOUGH BODY TO BE ABLE TO DEFEND ITSELF

AND FINALLY LEAVE ITS MOTHER'S PROTECTION.

♪♪

SOME BABIES ARE WELL DEFENDED FROM THE DAY THEY'RE BORN.

♪♪

IN THE FORESTS OF MADAGASCAR'S EAST COAST,

A MOTHER TENREC IS LEADING HER CLUTCH OF BABIES

OUT OF THE NEST TO FORAGE FOR INSECTS.

THEIR STRIPES HELP THEM HIDE IN THE DAPPLED LIGHT

OF THE FOREST FLOOR.

THEY MAY LOOK SMALL AND VULNERABLE,

BUT THE SKIN ON THEIR BACKS

IS A FOREST OF SHARP, BLACK AND YELLOW SPINES.

THEIR MOTHER HAS THEM, TOO,

BUT THEY'RE HIDDEN BY HER LONGER HAIR.

♪♪

♪♪

THE BABIES WERE BORN WITHOUT SPINES

BUT STARTED TO GROW THEM IN THE FIRST 24 HOURS AFTER BIRTH.

TOUGH AND SHARP, EACH SPINE IS A MODIFIED HAIR MADE OF KERATIN

AND GROWING OUT OF THE SKIN.

AND THEY'RE AN EXCELLENT FORM OF DEFENSE.

IF A PREDATOR TRIES TO BITE A TENREC,

THEY GET A MOUTHFUL OF SPINES AS A PAINFUL DETERRENT.

♪♪

SPINES AND QUILLS ARE SUCH AN EFFECTIVE WEAPON

THAT THEY'VE EVOLVED SEVERAL TIMES

IN THE SKIN OF DIFFERENT FAMILIES OF VERTEBRATES

IN DIFFERENT PARTS OF THE WORLD.

HEDGEHOGS ARE FOUND ACROSS EUROPE, AFRICA, AND ASIA.

IN AUSTRALIA, YOU GET ECHIDNAS.

♪♪

BUT FOR ME, THE CHAMPIONS ARE PORCUPINES.

THERE ARE TWO FAMILIES OF PORCUPINE --

NEW-WORLD PORCUPINES, FOUND IN NORTH AND SOUTH AMERICA,

AND OLD-WORLD PORCUPINES,

FOUND IN EUROPE, ASIA, AND AFRICA.

IN BOTH FAMILIES, THE BACKS AND SIDES OF THE PORCUPINE

ARE COVERED WITH THOUSANDS OF QUILLS.

IF A PREDATOR GETS TOO CLOSE, THEY ERECT

AND SPREAD THE QUILLS,

TURNING SO THEIR DANGEROUS REAR ENDS FACE THE WOULD-BE ATTACKER.

EVEN AN EXPERT HUNTER LIKE A LEOPARD,

CAPABLE OF TAKING DOWN A 900-KILOGRAM ELAND,

IS NO MATCH FOR 30 KILOGRAMS OF WELL-DEFENDED PORCUPINE.

♪♪

NOT ONLY DO PORCUPINES HAVE THESE LONG, STRONG QUILLS

GROWING OUT OF THEIR SKIN,

BUT THEY'VE EVOLVED TO BE DETACHABLE.

AND JUST LIKE HAIR, THEY FALL OUT FROM THE SKIN

WITHOUT HARMING THE OWNER AT ALL.

IF A PORCUPINE IMPALES AN ATTACKER,

THE LOST QUILLS WILL GROW BACK IN A MATTER OF MONTHS,

WHILE THE PREDATOR LEARNS A VALUABLE LESSON.

♪♪

AFRICAN PORCUPINE QUILLS ARE BIG AND IMPRESSIVE,

AND THEY CAUSE LOTS OF DAMAGE TO ANY WOULD-BE ATTACKER.

I CAN DEMONSTRATE THIS WITH A PIECE OF CHICKEN,

'CAUSE WHEN I STAB THE POINTY END INTO THE CHICKEN,

IT GOES IN NICE AND EASILY,

BUT ALSO IT COMES OUT NICE AND EASILY, TOO.

WHEN A PREDATOR LIKE A LION IS IMPALED

BY AN AFRICAN PORCUPINE,

GROOMING BY A PRIDE MEMBER CAN OFTEN HELP REMOVE THE QUILLS,

ALLOWING THE WOUNDS TO HEAL.

HERE, I'VE GOT THREE QUILLS FROM A NORTH AMERICAN PORCUPINE.

COMPARED TO THE AFRICAN QUILLS, THESE LOOK A BIT UNDERWHELMING.

THEY'RE FINER AND MUCH SHORTER.

BUT APPEARANCES CAN BE DECEPTIVE.

AND WHEN I STAB THIS QUILL INTO THE CHICKEN...

IT GOES IN NICE AND EASILY.

BUT WHEN I TRY AND PULL IT OUT...

IT'S EMBEDDED. IT'S STUCK FAST.

AND, ACTUALLY, TO REMOVE THE QUILL...

I'VE REALLY GOT TO PULL IT.

[ CLICK ]

AND YOU COULD HEAR THE FLESH TEARING AS I RIPPED THIS OUT.

IT'S NOT NICE.

THIS IS HAPPENING BECAUSE NORTH AMERICAN PORCUPINE QUILLS

HAVE BACKWARD-FACING MICROSCOPIC BARBS,

AS YOU CAN SEE HERE IN THIS ELECTRON MICROGRAPH.

THE BARBS DO TWO THINGS.

THEY SNAG ON MUSCLE AND SKIN,

MAKING THE QUILLS HARD TO PULL OUT.

BUT RESEARCH IN 2012 REVEALED

THE BARBS ALSO HALVE THE PENETRATION FORCE

NEEDED TO GET THE QUILLS INTO THE FLESH.

EVERY YEAR, MANY HUNDREDS OF NORTH AMERICAN DOGS

LEARN ABOUT THE DANGERS OF BARBED PORCUPINE QUILLS

THE HARD WAY.

♪♪

USING YOUR SKIN TO DEFEND YOURSELF

CAN BE EXTREMELY EFFECTIVE.

BUT CONCOCTING DEADLY SKIN TOXINS, CARRYING HEAVY ARMOR,

AND DROPPING AND REPLACING QUILLS TAKE TIME AND EFFORT.

♪♪

OVER MILLIONS OF YEARS, SOME VERTEBRATES HAVE EVOLVED

A CHEAPER AND MORE SOPHISTICATED WAY OF STAYING SAFE --

CAMOUFLAGE,

HIDING IN PLAIN SIGHT, USING THEIR SKIN AS A DISGUISE.

♪♪

HAIR, FEATHERS, AND SKIN

CAN ALL HELP ANIMALS BLEND INTO THEIR ENVIRONMENT.

♪♪

HOW EFFECTIVE THAT CAMOUFLAGE IS DEPENDS ON WHO'S LOOKING.

♪♪

UNLESS YOU'RE VERY, VERY LUCKY,

YOU'VE PROBABLY ONLY EVER SEEN A TIGER

IN A ZOO OR WILDLIFE PARK.

AND AGAINST THIS SORT OF BACKDROP,

IT'S HARD TO IMAGINE HOW SUCH VIVID STRIPES

COULD EVER ACT AS CAMOUFLAGE.

IN THEIR NATURAL ENVIRONMENT,

THE DISGUISE IS A BIT MORE EFFECTIVE,

BUT THERE'S STILL NO MISTAKING A DEADLY PREDATOR.

BUT LOOK AT THE WORLD THROUGH A PREY ANIMAL'S EYES,

AND A TIGER'S CAMOUFLAGE FINALLY MAKES SENSE.

CHITAL DEER, THE TIGER'S MAIN PREY,

HAVE WHAT IS KNOWN AS DICHROMATIC VISION.

THEY CAN'T TELL THE DIFFERENCE BETWEEN REDS AND GREENS.

SO, TO A DEER, THE PREDATOR

BLENDS INTO ITS BACKGROUND PERFECTLY.

♪♪

THIS MAKES IT EASIER FOR THE TIGER

TO GET WITHIN STRIKING DISTANCE.

♪♪

♪♪

THERE'S ONLY ONE FLAW IN THE TIGER'S STRATEGY.

♪♪

CHITAL HERDS ARE OFTEN FOUND WITH GROUPS OF LANGURS.

♪♪

THE MONKEYS DROP FRUIT AS THEY FEED.

BUT THAT'S NOT THE ONLY REASON THE CHITAL STAY CLOSE.

LANGUR MONKEYS HAVE FULL COLOR VISION.

♪♪

CHITAL HAVE LEARNED TO RECOGNIZE LANGUR ALARM CALLS

AND RUN FOR THEIR LIVES.

[ MONKEYS CHIRPING ]

♪♪

♪♪

THE TIGER'S COVER IS BLOWN.

♪♪

IF THOSE PESKY MONKEYS ARE GIVING THE GAME AWAY,

WHY DON'T TIGERS GO THE WHOLE HOG AND JUST HAVE GREEN HAIR?

♪♪

THAT'S BECAUSE MAMMALS, INCLUDING HUMANS, USE MELANIN

TO COLOR THEIR EPIDERMIS AND HAIR, AND MELANIN

CAN ONLY MAKE BLACKS, ORANGES, AND BROWNS.

ONLY ONE GROUP OF MAMMALS HAS MASTERED THE ART

OF GREEN JUNGLE CAMOUFLAGE --

THE TWO- AND THREE-TOED SLOTHS.

THESE SLOW-MOVING MAMMALS HAVE GREEN HAIR,

HELPING THEM BLEND INTO THEIR FOREST HOME.

BUT THAT COLOR ISN'T MADE BY THE SLOTH'S SKIN.

IT COMES FROM TINY GREEN ALGAE THAT COLONIZE THEIR HAIR.

♪♪

EACH STRAND HAS CRACKS IN IT,

WHICH TRAP THE MOISTURE THE MICROSCOPIC PLANTS NEED TO GROW.

♪♪

MOTHS LIVING IN THE SLOTH'S HAIR EVEN HELP TO FERTILIZE

THE ALGAE WITH THEIR NITRATE-RICH FECES.

♪♪

EVOLVING CAMOUFLAGED SKIN TO HELP YOU BLEND INTO

A PARTICULAR HABITAT IS PRETTY IMPRESSIVE,

BUT SOME ANIMALS HAVE TAKEN A REVOLUTIONARY NEXT STEP.

I'VE COME TO PLYMOUTH TO FIND OUT MORE

FROM MARINE BIOLOGIST ALIX HARVEY.

AND WHILE THE ANIMALS SHE STUDIES AREN'T VERTEBRATES,

YOU CAN'T TALK ABOUT EXTRAORDINARY SKIN DEFENSES

WITHOUT INCLUDING THEM.

HI, ALIX. HI, BEN.

LOOK AT THESE! I LOVE THESE LITTLE ANIMALS.

THEY'RE AMAZING, AREN'T THEY?

THEY'RE ABSOLUTELY FANTASTIC.

SO THESE ARE THE COMMON CUTTLEFISH, SEPIA OFFICINALIS.

THIS IS A SPECIES WE FIND ALL AROUND THE U.K.

THEY'RE ONE OF THE BIGGEST SPECIES OF CUTTLEFISH WE GET.

AND THEY'RE ABOUT 5 MONTHS OLD, THESE INDIVIDUALS,

SO THEY'RE STILL BABIES.I WAS GOING TO SAY,

I'VE SEEN MUCH BIGGER THAN THIS.

THESE ARE TINY BY COMPARISON, AREN'T THEY?

THAT'S RIGHT. SO, THEY HATCH OUT FROM EGGS ABOUT 1 CENTIMETER,

ABOUT THIS BIG, AND THEN

OVER THEIR LIFE CYCLE OF ABOUT 2 YEARS,

THEY GET REALLY, REALLY BIG, UP TO ABOUT THIS SIZE,

SO THESE ARE ALL STILL KIND OF BABIES IN MY EYES.

ALIX HAS CUTTLEFISH IN THREE DIFFERENT TANKS.

SO, WE'VE GOT SAND HERE, WE'VE GOT ROCKS,

AND THEN, WE'VE GOT SEAWEED.

SO THESE ARE ALL THE NATURAL ENVIRONMENTS

THEY WOULD EXPERIENCE IN THE WILD.

AND IN EACH TANK,

THE CUTTLEFISH ARE BEAUTIFULLY CAMOUFLAGED.

I'M JUST LOOKING AT THIS LITTLE ONE HERE,

AND IT'S BLENDED IN PERFECTLY WITH THE SANDY SURROUNDING.

YOU CAN REALLY SEE JUST HOW WELL IT'S BLENDED IN.

IT'S MANAGED TO PUT SOME SAND ON ITS BODY

AND IT'S REALLY BROKEN UP THE OUTLINE.

THE CUTTLEFISH IN TANK TWO, THE ROCKY TANK,

HAS VERY DIFFERENT SKIN COLORS AND PATTERNS.

AND SO YOU FIND HERE, IN THIS ROCKY KIND OF HABITAT,

THAT THEY WILL GET A VERY DISRUPTIVE BODY PATTERN.

IT'S JUST SLIGHTLY DIFFERENT.

AND, THEN, AT THE END, WE'VE GOT A MUCH DARKER ONE.

SO HE'S REALLY ADAPTED TO THE SEAWEED.

AND YOU CAN IMAGINE IF HE WAS SITTING IN AMONGST THE WEEDS,

IT WOULD BE VERY, VERY DIFFICULT TO TELL WHERE HE WAS,

PARTICULARLY AS HE'S USING HIS TENTACLES,

ACTUALLY LIFTING HIS TENTACLES OUT OF THE WATER,

IN ORDER TO KIND OF DISRUPT HIS BODY

AND REALLY PRETEND TO BE A PIECE OF SEAWEED.

ALIX'S CUTTLEFISH ARE ALL THE SAME SPECIES,

SO HOW HAVE THEY ENDED UP LOOKING COMPLETELY DIFFERENT?

THE ANSWER IS ADAPTIVE CAMOUFLAGE.

A CUTTLEFISH'S SKIN CAN RAPIDLY CHANGE COLOR

TO HELP IT BLEND SEAMLESSLY INTO ITS SURROUNDINGS

IN THE BLINK OF AN EYE.

ONE LITTLE ANIMAL WILL CHANGE FROM SANDY TO WEEDY TO STONY,

BUT HOW DO THEY DO THAT?

SO, CUTTLEFISH ACTUALLY

HAVE THREE DIFFERENT COLOR-CHANGING CELLS,

BUT THE ONES THAT ALLOW THEM TO DO THESE DIFFERENT

COLOR PATTERNS ARE CALLED CHROMATOPHORES.

AND THESE ARE BASICALLY CELLS THAT ARE PACKED FULL OF PIGMENT.

FOUND IN THE DERMIS,

EACH CHROMATOPHORE HAS MUSCLES ATTACHED TO ITS OUTER WALL.

WHEN THE MUSCLES CONTRACT, THE CHROMATOPHORE IS PULLED OPEN,

AND THE PIGMENT SPREADS OUT.

WHEN THE MUSCLES RELAX, THE CHROMATOPHORE SHRINKS DOWN,

COMPRESSING THE PIGMENT.

♪♪

SO WHEN IT'S PACKED REALLY, REALLY TIGHT,

IT'S VERY DIFFICULT TO SEE,

AND IT'S WHAT ALLOWS THEM TO HAVE A NICE WHITE COLOR,

AND WHEN IT'S SPLAYED OUT, IT BECOMES A NICE DARK SPLOTCH,

AND WHEN EXTRAPOLATED OVER THE WHOLE BODY OF THE CUTTLEFISH,

THIS IS WHAT ALLOWS THEM TO ACHIEVE

ALL KINDS OF BODY PATTERNS.

ALL CEPHALOPODS, INCLUDING OCTOPUS AND SQUID,

HAVE THIS AMAZING SKIN.

AND AS WELL AS CHANGING COLOR,

IN SOME SPECIES, IT CAN CHANGE TEXTURE, TOO.

♪♪

MUSCLES IN THE DERMIS PUSH THE SKIN INTO BUMPS CALLED PAPILLAE,

WHICH BREAK UP THE OUTLINE OF THE BODY,

HELPING THEM TO HIDE.

WHY ARE THEY HIDING? I'M GUESSING FROM PREDATORS, RIGHT?

THAT'S RIGHT. THEY ARE VERY SOFT-BODIED ANIMALS.

THEY DON'T HAVE ANY EXTERNAL HARD PIECES.

THEY CAN'T REALLY PROTECT THEMSELVES.

SO THE BEST THING FOR THEM IN ORDER TO AVOID BEING A MEAL

FOR SOMETHING ELSE IS JUST NOT TO BE SEEN IN THE FIRST PLACE.

ADAPTIVE CAMOUFLAGE IS AN AMAZING DEFENSIVE STRATEGY,

BUT THERE'S A CONUNDRUM.

A CUTTLEFISH'S EYES ARE ON THE TOP OF ITS BODY.

SO HOW DOES IT GATHER ENOUGH INFORMATION

ABOUT THE SURFACE HIDDEN BENEATH ITS BODY

TO MATCH ITS COLOR AND TEXTURE SO WELL?

SO, WE ALWAYS USED TO THINK THIS WAS BASICALLY

THAT THEY'RE SEEING THEIR ENVIRONMENT

AND THEN RELAYING THAT INFORMATION

TO THEIR CHROMATOPHORES BY THEIR BRAIN.

WE NOW THINK THERE MAY BE SOMETHING

EVEN MORE ASTOUNDING GOING ON, WHICH IS THAT THEY HAVE ACTUALLY

LIGHT-SENSING-CAPABILITIES WITHIN THEIR SKIN.

RESEARCHERS HAVE DISCOVERED TRACES OF A PROTEIN

CALLED RHODOPSIN IN THE CUTTLEFISH DERMIS.

EXACTLY THE SAME PROTEIN

IS FOUND IN THE RETINA OF A CUTTLEFISH'S EYES.

IT'S A LIGHT-SENSITIVE PIGMENT

THAT FORMS THE BASIS OF CUTTLEFISH VISION.

VERTEBRATES USE SIMILAR PROTEINS IN THEIR EYES.

THE RESEARCH IS IN ITS EARLY STAGES,

BUT THE PRESENCE OF RHODOPSIN IN THE SKIN

SUGGESTS CUTTLEFISH SKIN MAY BE ABLE TO SEE.

THIS IS SOMETHING THAT'S VERY, VERY NEW,

AND WE'RE ACTUALLY HOPING TO CONDUCT SOME EXPERIMENTS

THIS YEAR LOOKING AT THAT, LOOKING WHETHER,

IF THEY CAN'T SEE WHAT THE REST OF THEIR BODY'S DOING,

ARE THEY STILL ABLE TO ADAPT

AND COLOR-CAMOUFLAGE TO THEIR ENVIRONMENT?

IF ALIX'S RESEARCH REVEALS

THAT CUTTLEFISH CANSENSE LIGHT AND DARK WITH THEIR SKIN,

THEN WE'LL HAVE TO COMPLETELY REDEFINE CEPHALOPOD SKIN

AS NOT JUST AN AMAZING MEANS OF DEFENSE

BUT AN EXTRAORDINARY SENSORY ORGAN, TOO.

THESE CRYPTIC CUTTLEFISH ARE FURTHER PROOF

THAT SKIN STILL HAS SECRETS

WE'RE ONLY JUST BEGINNING TO UNDERSTAND.

♪♪

WHEN IT COMES TO DEFENDING YOURSELF FROM OTHER ANIMALS,

SKIN PROVIDES AN INCREDIBLE SELECTION OF WEAPONS AND ARMOR,

FROM DEADLY TOXINS AND PIERCING QUILLS,

RIGHT THROUGH TO CRYPTIC COLORATION.

FOR VERTEBRATES AND A FEW VERY SPECIAL INVERTEBRATES,

SKIN WILL KEEP YOU SAFE.

♪♪

♪♪

♪♪