(Narrator:) EYES ARE AS VARIED AND AS MYSTERIOUS
AS ANIMALS THEMSELVES.
SOME ARE ILLUSIONS,
OTHERS ALLOW A CREATURE TO SEE THE WORLD
IN A DIFFERENT LIGHT.
HOW HAVE THESE ANIMALS EVOLVED TO SEE AND BE SEEN?
(♪♪♪)
PENGUINS ARE FOUND ON EVERY CONTINENT
IN THE SOUTHERN HEMISPHERE.
THEY HAVE EVOLVED THROUGH LIFE ON LAND AND UNDERWATER.
THEY THRIVE IN BOTH ENVIRONMENTS,
LARGELY DUE TO THE STRENGTH OF THEIR EYES.
BUT UNLIKE OTHER BIRDS, PENGUINS DON'T FLY.
THEY LOST THIS TRAIT MILLIONS OF YEARS AGO.
BUT WHY HAVE THEY LOST THIS ABILITY
AND WHAT DO THEY NOW DO INSTEAD?
THE ANSWER BEGINS WITH THE EVOLUTION OF FLIGHT
AND ENDS WITH A LOOK IN THEIR EYES.
(Brown:) THE EVOLUTION OF POWERED FLIGHT HAS EVOLVED FOUR TIMES
INDEPENDENTLY AMONG ANIMALS.
THE INSECTS, BIRDS, OF COURSE,
THE REPTILES IN TERMS OF PTEROSAURS
AND AMONG MAMMALS, THE BATS.
WE LOOK AT THE CONSEQUENCE ON EVOLUTION,
FLIGHT HAS LED TO A GREAT DEGREE OF SUCCESS
IN TERMS OF DIVERSIFICATION,
CREATING A GREAT NUMBER OF SPECIES.
AND IT'S LARGELY DUE TO THIS NEW WAY
TO TAKE ADVANTAGE OF ECOLOGICAL NICHES
THAT ARE AVAILABLE EXCLUSIVELY TO THEM.
(Narrator:) BUT SOME SPECIES LIKE THE PENGUIN
HAVE LOST THEIR ABILITY TO FLY.
A PHENOMENON IN THE HISTORY OF EVOLUTION
THAT SEEMS LIKE A STEP BACKWARDS.
WHY GO UP, JUST TO GO DOWN AGAIN?
ONE STUDY SUGGESTS THAT THE ENERGY COSTS OF FLIGHT
FOR PENGUINS BECAME HIGHER THAN THE ENERGY COSTS OF DIVING.
IN TURN, THE PENGUIN TURNED ITS WINGS INTO FLIPPERS.
(Brown:) IF WE WERE TO LOOK AT THE ADAPTIVE MECHANISMS
THAT WOULD LEAD TO THE LOSS OF FLIGHT
BECAUSE OF A REQUIREMENT TO DO SOMETHING ELSE,
WELL, THAT CAN BE A GOOD EXPLANATION
FOR WHAT WE SEE IN THE PENGUINS.
AS PENGUINS BECAME INCREASINGLY AQUATIC,
THEIR COLOR FOLLOWED SUIT.
THEIR DABBER TUXEDO PRINT WITH BOLD HUES OF BLACK AND WHITE,
MIGHT HAVE EVEN EVOLVED FOR A REASON,
AS A FORM OF CAMOUFLAGE.
(Herren:) PENGUINS HAVE THIS, KINDA, WEIRD CAMOUFLAGE, YOU KNOW,
YOU THINK IT'S COUNTER-INTUITIVE.
THAT WHITE UNDERSIDE IS SO THAT IF ANY PREDATOR WAS SWIMMING
BELOW THEM, WHEN THEY LOOK UP, THEY BLEND IN
AND YOU WON'T BE ABLE TO DISTINGUISH THEM
FROM THE SUNLIGHT.
IF YOU'RE A PREDATOR LOOKING DOWN BELOW,
BECAUSE OF THEIR DARK COLORATION ON THEIR BACK,
THEY BLEND IN WITH THE DARK COLOR OF THE WATER BELOW.
(Narrator:) BUT NEW RESEARCH REVEALS
THAT PENGUINS HAVE NOT ALWAYS BEEN BLACK AND WHITE.
THIRTY-SIX MILLION YEARS AGO, LIVED AN ANCIENT PENGUIN
NAMED THE "WATER KING".
STANDING AT FIVE FEET TALL,
THIS BIRD REACHED THE HEIGHTS OF SMALL HUMANS,
DWARFING PENGUINS OF TODAY.
FEATHERS FOUND FROM A FOSSIL OF THE WATER KING
HAVE PROVEN THAT THIS MAN-SIZED BIRD HAD GREY AND RED COLOURING.
THE CAMOUFLAGE THEORY SUGGESTS
THAT THESE RED AND GREY FEATHERS CHANGED COLOR
IN RESPONSE TO NEW PENGUIN PREDATORS LIKE SEALS.
AN ALTERNATE THEORY POINTS OUT THAT CHANGING PIGMENT PACKETS
IN THESE FEATHERS MIGHT HAVE MADE PENGUINS MORE STIFF,
TURNING THEIR WINGS INTO NARROW FLIPPERS.
TODAY, MODERN PENGUINS WADDLE WITH DILIGENCE,
USING OTHER USEFUL TRAITS TO HELP THEM SURVIVE.
THEIR BODIES ARE SMOOTH AND STREAMLINED,
MADE FOR FAST AND EFFICIENT SWIMMING.
THEIR FEATHERS ARE WATERPROOF,
COATED WITH OIL FROM A GLAND NEAR THEIR TAIL.
BUT WHAT IS ESPECIALLY FASCINATING ABOUT PENGUINS
ARE THEIR EYES.
THESE ADAPTATIONS ARE IMPORTANT FOR THEIR SURVIVAL.
PENGUINS CAN SEE EQUALLY AS WELL UNDERWATER AS ON LAND.
THEIR CORNEA IS FLAT LIKE A WINDOWPANE
AND ALTERS THE ANGLE AT WHICH LIGHT CAN ENTER THEIR EYE.
THIS IS AN IMPORTANT ADAPTATION FOR SEEING UNDERWATER
WHERE LIGHT ENTERS THE EYES INDIRECTLY THROUGH WATER
WITH A DENSITY THAT IS DIFFERENT FROM THE DENSITY OF AIR.
THEIR IRIS IS CONTROLLED BY A POWERFUL MUSCLE
THAT DRASTICALLY CHANGES THE SIZE OF THE PUPIL,
AS A PENGUIN MOVES FROM LAND TO UNDERWATER.
THEY ALSO HAVE A SECRET GLAND NEAR THEIR EYE
THAT HELPS THEM AS THEY NAVIGATE SALT WATER.
(Herren:) WELL, AS YOU CAN IMAGINE, LIVING IN THE SEA,
THINGS GET A LITTLE SALTY,
SO PENGUINS ACTUALLY HAVE A GLAND THAT'S NEAR THEIR EYES
THAT HELPS THEM EXCRETE THE EXCESS SALT FROM THEIR BODIES.
(Narrator:) ACTING LIKE A KIDNEY,
THIS GLAND REMOVES SALT FROM THE BLOOD STREAM
AND ALLOWS PENGUINS TO SURVIVE WITHOUT ACCESS TO FRESHWATER.
AS AWKWARD AS THEY SEEM,
PENGUINS HAVE ADAPTED TO SURVIVE FOR LIFE IN THE WATER.
THEY CHANGE THEIR COLOR, THEIR WINGS
AND THEIR SIZE TO DIVE AND FORAGE IN THE SEA.
AND LAST BUT NOT LEAST, THEY ADAPTED EFFICIENT EYES
FOR CLEAR VISION ON LAND AND UNDERWATER.
THE RED-EYED TREE FROG'S COLORFUL EYES
HAVE HELPED IT SURVIVE FOR MILLIONS OF YEARS
AND IT MAY STILL BE EVOLVING.
BUT IN WHAT WAY?
(♪♪♪)
ITS BLOOD-RED EYES REALLY MAKE IT STAND OUT,
WHICH IS NOT ALWAYS A GOOD THING FOR SOMETHING SO BITE-SIZED.
BUT THE RED-EYED TREE FROG HAS BEEN AROUND
FOR MILLIONS OF YEARS.
SO, HOW HAS IT MADE IT THIS FAR?
WHAT ADAPTATIONS HAVE ALLOWED IT TO THRIVE?
AND WHAT NEW ADAPTATIONS MIGHT THIS FROG HAVE UP ITS SLEEVE.
THE RED-EYED TREE FROG IS FOUND MOSTLY IN CENTRAL AMERICA,
IN THE CANOPY OF LOW-LAND RAIN FORESTS NEAR STREAMS.
BUT IT DIDN'T ALWAYS LOOK AS IT DOES NOW.
250 MILLION YEARS AGO,
THE ANCESTOR OF THE RED-EYED TREE FROG WAS BIGGER
AND HAD A SMALL TAIL.
FACING THE CHALLENGES OF QUICK MOVING PREDATORS, LIKE SNAKES,
IT EVOLVED INTO A SMALLER VERSION
AND LOST THE TAIL.
NO TAIL AND A SMALLER BODY MEAN IT CAN JUMP BETTER
TO EVADE THOSE SNEAKY PREDATORS.
STAYING ALIVE IS JOB ONE
AND ITS EYES HAVE SPECIAL ADAPTATIONS
TO HELP IT DO JUST THAT.
THOSE FIERY EYES ARE LIKE TWO LITTLE LIGHTHOUSES
THAT SIT HIGH ON ITS HEAD
AND HAVE AN ALMOST 360° VIEW TO SPOT PREDATORS.
THE BIG RED IRISES MAYBE AN ADAPTATION
CALLED "STARTLE COLORATION".
WHEN A RED-EYED TREE FROG SUDDENLY OPENS ITS EYES,
IT MIGHT STARTLE PREDATORS LONG ENOUGH
TO ALLOW FOR THE FROG TO GET AWAY.
ANOTHER DEFENSE IS THE EASIEST AND HARDEST TO SEE,
ITS COLORS.
THOUGH IT'S MOSTLY BRIGHT GREEN,
IT HAS BLUE AND YELLOW STRIPES ON ITS SIDES
AND, OF COURSE, THOSE SHOCKING RED EYES.
THE COLORS FUNCTION IN TWO COMPLETELY DIFFERENT WAYS;
IT ADAPTED THE LEAFY GREEN COLOR
TO HELP IT DISAPPEAR WHILE IT IS SLEEPING.
(Brown:) THE BENEFITS OF CAMOUFLAGE ARE ESSENTIALLY NOT TO BE SEEN.
ALRIGHT, IT'S TO BE ABLE TO HIDE IN PLAIN SIGHT.
THIS CAN BENEFIT EITHER THOSE
THAT ARE TRYING TO HIDE FROM PREDATORS
OR THOSE THAT ARE MAYBE PREDATORS THEMSELVES
AND TRYING TO HIDE FROM THEIR PREY.
SO, THE IDEA OF CAMOUFLAGE
IS TO LOOK LIKE ONE'S BACKGROUND.
IN THE DAY TIME, IT HAS ITS EYES CLOSED
AND IT'S ARMS AND LEGS TUCKED IN
AND MASKING ALL OF THAT BRIGHT COLOR
AND IT BASICALLY HANGS OUT IN THE UPPER CANOPY,
LOOKING VERY GREEN LIKE THE REST OF EVERYTHING AROUND THERE
THAT'S PRETTY WELL GREEN.
CAMOUFLAGED, HIDDEN.
AN ALTERNATIVE TO BEING CAMOUFLAGED
IS ACTUALLY STANDING OUT FROM THE BACKGROUND.
AT NIGHT, IT HAS THIS BRIGHT WARNING COLORATION,
RED EYES, BRIGHTLY COLORED FLANKS AND LEGS,
IT IS TO SAY, "I'M QUITE CONSPICUOUS, YES,
I KNOW YOU CAN SEE ME."
THIS MAY ACT TO DETER THE PREDATORS
EITHER BECAUSE IT'S, LIKE, A FLASH OF COLOR THAT MAY STARTLE
AND GIVE MAYBE THE TREE FROG A BRIEF SECOND OR TWO
TO AVOID BEING EATEN
OR, IN FACT, IT COULD BE A MIMICRY.
(Narrator:) BUT CAN THE RED-EYED TREE FROG TRICK PREDATORS IN OTHER WAYS?
ONE THEORY IS THAT AFTER JUMPING AWAY,
IT'S COLORS LEAVE AN IMAGE OF ITSELF BEHIND
CAUSING THE ATTACKER TO LUNGE AT A GHOST.
HOW COULD THE RED-EYED TREE FROG KNOW TO JUMP AWAY
IN THE FIRST PLACE?
IT HAS A BUILT-IN WARNING SYSTEM.
FROGS LACK AN OUTER EAR,
THEIR EAR DRUM OR TYMPANUM IS EXPOSED.
THIS SMALL CIRCULAR MEMBRANE IS VISIBLE JUST BEHIND THEIR EYE.
THIS MEMBRANE CONNECTS THE INNER EAR TO THE LUNGS.
AS A RESULT, WHEN A SNAKE MOVES UP A BRANCH,
THE FROG WILL HEAR THE VIBRATIONS
COMING THROUGH ITS OWN CHEST.
SENSITIVE HEARING IS JUST ONE WAY
IT CAN PROTECT ITSELF FROM PREDATORS.
MULTI-COLORED SKIN, STARTLING EYES AND LUNGS
THAT HELP THEM HEAR ARE ALL NEAT ADAPTATIONS
BUT THIS SPECIES MAY STILL BE EVOLVING.
SCIENTISTS THINK THEY HAVE OBSERVED
DEVELOPMENTAL PLASTICITY
IN THE EMBRYOS OF THE RED-EYED TREE FROG.
(Standen:) DEVELOPMENTAL PLASTICITY IS THE ABILITY OF AN ORGANISM
TO CHANGE IN DIFFERENT WAYS
DEPENDING ON THE ENVIRONMENT IT'S DEVELOPING IN.
(Narrator:) THIS THEORY SUGGESTS AN ORGANISM HAS THE ABILITY
TO TRANSLATE ITS GENES INTO ACTIONS.
IF THERE IS A TREAT LIKE A SNAKE,
AN EMBRYO CAN DROP OUT OF ITS EGG
TO AVOID DYING BEFORE IT EVEN HATCHES.
USING VIBRATIONAL CUES IN ITS ENVIRONMENT,
UNHATCHED EMBRYOS ARE ABLE TO DETERMINE
WHETHER THEY ARE UNDER ATTACK FROM A PREDATOR
AND RESPOND ACCORDINGLY.
LEAVING THEIR EGG EARLY
INCREASES THEIR CHANCE OF SURVIVAL
BUT IT COMES WITH A PRICE.
THE EMBRYO IS MAKING A TRADE-OFF
HATCHING PREMATURELY AND GIVING UP THE OPPORTUNITY
TO DEVELOP LONGER INSIDE OF THE EGG.
THIS COLORFUL LITTLE CREATURE HAS SURVIVED
FOR MILLIONS OF YEARS
AND IT'S NOT ABOUT TO GIVE UP NOW.
A ZEBRA'S STRIPES ARE CERTAINLY EYE CATCHING AND CURIOUS
BUT IT'S THEIR VISION AND HEARING
THAT HELPS KEEP THEM ALIVE.
IF THERE IS ONE THING EVERY ZEBRA IN THE WORLD
DOES NOT HAVE IN COMMON, IT'S THEIR STRIPES.
SURE THEY ALL HAVE THOSE BLACK AND WHITE GENETIC MARKERS
BUT LIKE A FINGERPRINT, EVERY PATTERN IS UNIQUE.
THE STRIPES ARE CLEARLY
ONE OF THE ZEBRA'S MOST OBVIOUS ADAPTIONS.
BUT WHY DO THEY HAVE STRIPES IN THE FIRST PLACE?
TO MANY, THEY ARE ONE OF EVOLUTION'S GREAT MYSTERIES.
FOUND IN EAST AND SOUTH AFRICA,
ZEBRAS EVOLVED FROM OLD WORLD HORSES
OVER 3 MILLION YEARS AGO.
THOUGH IT WAS GRADUAL, THEY ALL EVOLVED BOLD STRIPES
BUT THE WIDTH AND SPACING OF THESE STRIPES
VARIED AMONG SPECIES.
STILL TODAY, THE FURTHER SOUTH YOU GO IN AFRICA,
THE FARTHER APART THE STRIPES ARE.
WHAT YOU CAN'T SEE IS HOW THE STRIPES DEVELOPED
IN THE FIRST PLACE.
THE STRIPES ARISE FROM SPECIAL SKIN CELLS
THAT DETERMINE THE COLOR OF FUR.
A ZEBRA'S BLACK STRIPES ARE ACTUALLY A TRANSFER
OF THE PIGMENTATION FROM THEIR BLACK SKIN INTO THE FUR.
BUT FOR THE ZEBRA, IT'S NOT ALL BLACK AND WHITE.
THE STRIPE RIDDLE HAS PUZZLED SCIENTISTS
FOR HUNDREDS OF YEARS.
CAMOUFLAGED TO CONFUSE PREDATORS WAS THE PREVAILING THEORY
FOR MANY YEARS
BUT OTHER STUDIES HAVE SUGGESTED ALTERNATIVES.
DR. ANTHONY SINCLAIR HAS STUDIED WILDLIFE BEHAVIOUR
IN THE SERENGETI FOR 50 YEARS.
(Sinclair:) THERE ARE A NUMBER OF THEORIES ABOUT THE STRIPES.
ONE OF THEM, FOR EXAMPLE,
WAS THAT IT PLAYED A PART
IN THERMAL REGULATION.
(Narrator:) WHEN A BREEZE HITS THE BLACK STRIPES,
IT FLOWS FASTER BECAUSE BLACK ABSORBS HEAT
BUT ITS SLOWS OVER THE COOLER WHITE STRIPES.
THE COLLISION OF THESE CURRENTS CAUSES TINY SWIRLS OF AIR,
WHICH ACT LIKE MINI FANS KEEPING THE ZEBRA COOL.
(Sinclair:) ANOTHER ONE PLAYED A PART IN ATTRACTING OR NOT ATTRACTING
TSETSE FLIES, WHICH ARE BITING FLIES THAT ARE A REAL PEST.
(Narrator:) THE TSETSE FLY THEORY IS ONE OF THE MORE RECENT AND COMPELLING.
DISEASE CARRYING INSECTS MAY NOT LIKE LANDING
ON THE CONFUSING TONES OF THE STRIPES,
AS THEY ARE USED TO A SOLID COLORED HIDE LIKE A WILDEBEEST.
THIS SUGGESTS THE ZEBRA'S MANY ADAPTATIONS
ARE NOT ALL ABOUT AVOIDING PREDATORS
BUT ALSO AVOIDING DEATH BY DISEASE.
BUT MAYBE, IT'S ABOUT WHO THEY HANGOUT WITH.
ONE THEORY IS THAT HE STRIPES HELP WITH SOCIAL INTERACTION.
THEIR UNIQUE PATTERNS ARE WHAT IDENTIFY THEM TO EACH OTHER
AND HELP THEM BOND AS A GROUP.
(Sinclair:) NONE OF THESE STORIES ARE REALLY VERY CONVINCING
AND NOR DO I KNOW OF ANY ADEQUATE DATA
THAT WOULD SUPPORT THIS.
(Narrator:) THOUGH NEVER CAPTURED ON CAMERA,
DR. SINCLAIR HAS HIS OWN THEORY ON THE STRIPES,
BASED ON FIELD RESEARCH IN THE SERENGETI.
BUT IT'S, KIND OF, A SHOT IN THE DARK.
DURING THE DAY, THE ZEBRA'S BOLD STRIPES STICK OUT
BUT DR. SINCLAIR REALIZED
IT'S A VERY DIFFERENT STORY AT NIGHT.
(Sinclair:) I WAS WATCHING WILDEBEEST
AND, OF COURSE, IF THERE'S WILDEBEEST, THERE'S ZEBRAS.
I WAS STUDYING THESE ANIMALS AT NIGHT
AND TO DO THIS, I NEEDED A PARTICULAR SCOPE
WHICH WAS CALLED A "STARLIGHT INTENSIFIER".
I COULD SEE THE WILDEBEEST REASONABLY WELL
BECAUSE THEY WERE BLACK SHAPES AGAINST THE GRASS
WHICH COMES OUT RELATIVELY PALE.
HOWEVER, EVERY NOW AND AGAIN AS I WAS WATCHING A WILDEBEEST,
IT WOULD JUST VANISH BEFORE MY EYES.
FINALLY, I REALIZED THAT IT WAS A ZEBRA
WALKING IN FRONT OF A WILDEBEEST AND I COULDN'T SEE THE ZEBRA.
THE ZEBRA WAS EXACTLY THE SAME INTENSITY OF LIGHT
AS THE BACKGROUND.
NOW, THIS SAID TO ME THAT MAYBE THE STRIPES ARE ALL ABOUT
BEING INVISIBLE AT NIGHT,
WHICH, IN FACT, IS WHEN THE PREDATORS HUNT
'CAUSE THE PREDATORS CAN SEE SO MUCH BETTER
THAN THE PREY AT NIGHT.
(Narrator:) THOUGH THE STRIPES ARE THE ZEBRA'S MOST
OBVIOUS ADAPTATION FOR SURVIVAL,
THERE IS ANOTHER USEFUL TRAIT.
THEY HAVE EYES IN THE BACK OF THEIR HEAD- ALMOST.
(Rajala:) INSTEAD OF HAVING EYES ON THE FRONT OF THEIR HEAD,
THEY HAVE THEM ON THE SIDES OF THEIR HEAD.
THIS INCREASES THEIR FIELD OF VISION,
SO THAT AS SOON AS THEY SEE SOMETHING,
ALMOST EVEN BEHIND THEM,
THEY CAN SEE THAT MOVEMENT AND REACT TO IT.
(Narrator:) BUT SINCE YOU CAN'T ALWAYS SEE WHAT'S COMING,
ZEBRAS HAVE A CO-PILOT ON DEFENSE.
THEIR HEARING HAS EVOLVED
TO BE A BIG PART OF THEIR EARLY WARNING SYSTEM.
INTRICATE MUSCLE MOVEMENTS ALLOW THEM TO ROTATE THEIR EARS
INDIVIDUALLY, LIKE A RADAR DISH.
(Rajala:) IF THERE'S ANY NOISE IN ANY OTHER DIRECTION,
YOU CAN JUST SEE EVEN ONE EAR POINT TOWARDS IT,
JUST TO KINDA CHECK OUT WHAT'S GOING ON.
(Narrator:) THE ZEBRA IS A SURVIVOR.
IT HAS ADAPTED PRACTICAL DEFENSE TOOLS
LIKE ITS EYES AND EARS THAT GIVE IT A JUMP ON PREDATORS.
YET DESPITE THE MANY THEORIES,
THOSE STRIPES SEEM TO REMAIN A MYSTERY.
NOT EVERYTHING IS AS IT APPEARS IN NATURE.
CLEVER DEFENCE OFTEN USES ILLUSION TO WARD OFF PREDATORS,
THEN IT'S ALL ABOUT HOW A CREATURE IS SEEN
MORE THAN HOW IT SEES.
(CAMERA CLICKING)
THE ANIMAL KINGDOM IS FILLED WITH EXOTIC EYES.
BUT SOME CREATURES WITH CLEAVER DECEIT
HAVE ADAPTED FAKE EYES TO TRICK THE REAL EYES OF OTHERS.
SEEN IN SEVERAL SPECIES, IT IS A MATTER OF MIMICRY.
PRETENDING TO BE SOMETHING YOU ARE NOT IN ORDER TO SURVIVE.
BUT WHY HAVE EYES SPOTS DEVELOPED IN THE FIRST PLACE?
THE ANSWER UNFOLDS AS WE EXPLORE EACH CULPRIT.
THE GREAT MORMON CATERPILLAR, A COMMON SOUTH ASIAN SPECIES
HAS BEEN ONTO SOMETHING FOR QUITE SOME TIME NOW.
WITH FAKES EYES ON THE TOP OF ITS HEAD,
IT APPEARS TO GLARE THAT ENEMIES ABOVE LIKE BIRDS
IN SEARCH OF THEIR NEXT MEAL.
(Hossie:) CATERPILLAR EYE MIMICRY IS A WIDESPREAD PHENOMENON,
IT OCCURS TAXONOMICALLY IN GROUPS ALL OVER THE WORLD.
(Narrator:) THESE CATERPILLARS ARE PRETENDING TO BE CREATURES
MORE DANGEROUS THAN THEY ARE, LIKE SNAKES.
(Hossie:) WE THINK CATERPILLARS WANNA MIMIC SNAKES
BECAUSE THEY ARE AN INCREDIBLY DANGEROUS THREAT TO BIRDS
AND BIRDS ARE THE MAIN PREDATOR OF CATERPILLARS,
IT DETERS THE BIRDS FROM ATTACKING.
(Narrator:) BUT HOW DO WE KNOW THAT THESE EYESPOTS ARE MIMICKING EYES
IN THE FIRST PLACE?
(Hossie:) SO, WE THINK THAT THESE EYESPOTS ARE ACTUALLY MIMICKING EYES
BECAUSE OF WHERE THEY'RE PLACED AND WE'VE DONE SOME EXPERIMENTS
THAT SHOW THAT WHEN EYESPOTS ARE ACTUALLY IN A PLACE
WHERE YOU WOULDN'T EXPECT EYES TO BE,
THEY'RE NOT EFFECTIVE DETERRENT.
(Narrator:) BUT FAKE EYES ALONE ARE NOT ENOUGH TO EVADE PREDATORS,
THE BEHAVIOR OF A CATERPILLAR IS ALSO IMPORTANT.
A CATERPILLAR'S BODY ACTUALLY INFLATES
WHEN THEY TAKE THEIR DEFENSIVE POSTURE
AND IT MAKES THE FRONT OF THAT CATERPILLAR
LOOK MORE LIKE A SNAKE-- HEAD OF SNAKE.
ANOTHER LINE OF DEFENSE IS THEIR FAKE TONGUE,
A DEFENSIVE ORGAN, RED AND SLIMY WITH A FLESHY FORK ON THE END.
THIS ORGAN RESEMBLES THE TONGUE OF A SNAKE,
WHEN RELEASED, IT FRIGHTENS PREDATORS
WHILE EMITTING AN AWFUL-SMELLING ODOR.
BUT WHAT IT MOST INTERESTING IS THAT CATERPILLARS WITH EYESPOTS
DO NOT ALWAYS BRING THESE EYES WITH THEM
WHEN THEY GROW UP TO BE BUTTERFLIES.
THERE'S MANY, MANY CATERPILLARS THAT HAVE EYES SPOTS
AND MANY BUTTERFLIES AND MOTHS THAT HAVE EYESPOTS
BUT THERE'S NO DIRECT RELATIONSHIP BETWEEN THE TWO.
BUT EYESPOTS OFTEN DO LINE THE WINGS OF THE BUTTERFLY.
SOME SCIENTISTS BELIEVE THAT THESE MARKERS TRICK PREDATORS
INTO ATTACKING THE EDGE OF THEIR WINGS,
ALLOWING FOR A QUICK GETAWAY.
OTHER BELIEVE THAT LIKE IN CATERPILLARS,
LARGE AND CONSPICUOUS EYESPOTS ARE USED
TO INTIMIDATE PREDATORS,
TO MAKE THEM THINK THE BUTTERFLY IS BIGGER AND SCARIER
THAN IT ACTUALLY IS.
ANIMALS WITH EYESPOTS ARE NOT ONLY ON LAND,
UNDERWATER LIVES ANOTHER CREATURE THAT IS PRETENDING.
BUTTERFLY FISH, FOUND IN REEFS AROUND THE WORLD,
HAVE A SIMILAR STRATEGY.
EYESPOTS NEAR THE TAIL OF THE FISH
GIVE THE IMPRESSION OF A HEAD AT THE WRONG END.
SOME SCIENTISTS THINK THAT THIS ACTS AS A DECOY,
TELLING PREDATORS TO ATTACK THEIR TAIL
INSTEAD OF THEIR HEAD.
UNDERWATER, EYESPOTS ARE DIFFERENT THAN ON LAND.
EYESPOTS ON LAND ANIMALS HAVE A GLOSS OR A SHINE,
A CERTAIN SPARKLE
THAT MIMICS THE REFLECTION OF SUNLIGHT ON A REAL EYE.
BUT EYESPOTS ON THESE FISH HAVE NO SPARKLE.
THEY ARE FLAT IN COLOR AND HAVE NO SHINE.
WITH NO SUN UNDERWATER,
THEIR PRETENDING DOES NOT NEED TO GO THAT FAR.
BIG OR SMALL, ON LAND OR UNDERWATER,
EYESPOTS ARE A CLEVER EVOLUTIONARY PATTERN
THAT INCREASES THE ODDS OF SURVIVAL
FOR SOME VULNERABLE CREATURES.
PROTECTED BY PRETENDING, THESE TRICKSTERS VENTURE ON.
SOME ANIMALS EVOLVE TO BE MASTERS OF ILLUSION
AND DECEPTION TO HELP THEM SURVIVE.
THE PENGUIN, THE RED-EYED TREE FROG,
THE ZEBRA AND CREATURES WITH EYESPOTS
HAVE ALL BEEN ABLE TO THRIVE
BECAUSE OF HOW THEY SEE AND ARE SEEN.
(♪♪♪)