All language subtitles for Great Snakes 720p EN

Narrator: FOR CENTURIES,
THEY'VE BEEN SEEN

AS NATURE'S OUTCASTS...

SLY, SLINKING CREATURES
POISED AND DANGEROUS.

RUTHLESS, COLD-BLOODED KILLERS.

EVIL INCARNATE.

[RATTLING]

BUT THE TRUTH IS, SNAKES
ARE VERY MUCH MALIGNED.

DESPITE A REPUTATION
THAT SPREADS FEAR AND LOATHING,

THEY'RE ONE OF NATURE'S
MOST AMAZING SUCCESS STORIES.

Man: SNAKES ARE VERY RESILIENT.

NO GROUP OF ANIMALS
IS GOING TO BE ABLE TO SURVIVE

FOR 150 MILLION YEARS

UNLESS THEY'VE BECOME MASTERS
AT ADAPTATION AND SURVIVING.

Narrator: SINCE THE TIME
OF THE DINOSAURS,

THESE REPTILES
HAVE SLITHERED THEIR WAY

ALONG THE PATH OF EVOLUTION.

SECRETIVE...SINUOUS...
CARNIVOROUS...

EMBRACING THE ONE ESSENTIAL
TRUTH OF LIFE ON EARTH:

ADAPT OR DIE.

¶

IN THE BEGINNING,
SOME 150 MILLION YEARS AGO,

SNAKES WERE LIZARDS...

RESEMBLING THESE
REPTILIAN COUNTERPARTS.

THE EARTH WAS
FAR DIFFERENT THEN.

VIRTUALLY EVERYWHERE THE CLIMATE
WAS WARM AND TROPICAL.

GIGANTIC DINOSAURS
PROWLED THE EARTH.

[ROARING]

MEANWHILE, A GROUP
OF LIZARD-LIKE CREATURES

ENTERED A BURROWING STAGE
IN THEIR EVOLUTION,

WHICH LED
TO A PHYSICAL TRANSFORMATION.

Kevin Barrett:
THESE ANIMALS WERE MOST LIKELY
CHASING AFTER PREY

THAT WAS MORE READILY AVAILABLE
UNDERGROUND.

AND WITH THAT IN MIND,

LIMBS, MOVEABLE EYELIDS

AND EXTERNAL EAR OPENINGS

BECAME MORE OF A HINDRANCE

AS OPPOSED TO
AN EVOLUTIONARY ADVANTAGE.

Narrator:
A HUNDRED MILLION YEARS LATER,

WHEN THESE CREATURES EMERGED
FROM UNDERGROUND,

A SLENDER, TUBE-LIKE ANIMAL
APPEARED--

WHAT WE NOW CALL A SNAKE.

BY THE TIME THE DINOSAURS WENT
EXTINCT 65 MILLION YEARS AGO,

SNAKES HAD DIVERSIFIED
AND BECOME MORE WIDESPREAD.

SOME SPECIES WOULD DIE OUT,

BUT OTHERS CONTINUED
TO EVOLVE...

RELENTLESSLY ADAPTING...

CHANGING TO FIT
THE CIRCUMSTANCES

OF CLIMATE, HABITAT
AND ACCESS TO FOOD.

TODAY, THERE ARE SOME 3,000
SPECIES OF SNAKES...

SHARING MANY ANATOMICAL FEATURES
WITH OTHER VERTEBRATES,

INCLUDING HUMANS.

Barrett: SNAKES HAVE PRETTY MUCH
ALL THE SAME ORGANS

THAT HUMANS DO.

THEY HAVE STOMACHS, INTESTINE,
LUNGS, HEARTS, KIDNEYS,

ALL THOSE ORGANS ARE STILL
PRESENT INSIDE THE SNAKE.

BUT MANY OF THEM ARE HIGHLY
MODIFIED TO FIT THEIR BODY TYPE.

ONE EXAMPLE OF THAT
IS THEIR LUNGS.

ONE IS MUCH MORE OUTSIZED
THAN THE OTHER

AND TAKES UP THE MAJORITY
OF ITS RESPIRATION.

[BIRDS CALLING]

Narrator: THE SNAKE'S
UNIQUE BODY TYPE

HASN'T KEPT IT FROM ADAPTING
TO A VARIETY OF HABITATS.

Barrett: THEY LIVE
IN THE FORESTS, UNDERGROUND,

UP IN TREES, IN THE OCEANS,
IN FRESHWATER.

AND THERE'S REALLY
NO OTHER VERTEBRATE

THAT HAVE BEEN ABLE TO EXPLOIT

ALL THOSE DIFFERENT
ENVIRONMENTS.

ANOTHER FEATURE SHARED
BY ALL SNAKES

IS THAT THEY ARE ECTOTHERMIC,

OR OFTEN REFERRED TO
AS COLD-BLOODED.

SO THIS MEANS
THAT THEY GET THEIR HEAT

FROM THE ENVIRONMENT...

AS OPPOSED TO MAMMALS,
WHO HAVE INTERNAL METABOLISMS

THAT HELP MAINTAIN
BODY TEMPERATURE.

Narrator: SNAKES ARE
NATURAL-BORN PREDATORS,

BUT THEIR VISION IS NOT
A PRIMARY WEAPON IN THE HUNT.

THAT'S BECAUSE,
AS BURROWING ANIMALS,

THEY HAD LITTLE USE FOR EYES.

Barrett: SO SNAKES' EYESIGHT
IS HIGHLY VARIABLE

ACROSS DIFFERENT SPECIES.

SOME ARE VERY ADEPT
AT SEEING THEIR PREY,

SOME ARE ONLY ABLE TO SEE
BLURRY MOTIONS.

SOME OF HAVE EVOLVED TO HAVE
EXCELLENT EYESIGHT,

ESPECIALLY AT NIGHT.

Narrator: AS FOR HEARING,
SNAKES LACK EXTERNAL EARS,

BUT CAN PERCEIVE SOUNDS

BY PICKING UP VIBRATIONS
IN THE GROUND

THROUGH A BONE IN THEIR JAW.

Barrett: THEY DON'T HAVE
EXTERNAL EAR OPENINGS

OR EVEN AN EARDRUM.

BUT THEY HAVE RETAINED
INNER EAR STRUCTURES

THAT ARE CONNECTED
TO THEIR JAW BONE.

SO SINCE SNAKES OFTEN HAVE
THEIR JAW TOUCHING THE GROUND,

IT'S VERY IMPORTANT FOR THEM

TO BE ABLE TO SENSE
THOSE VIBRATIONS.

Narrator: GIVEN THEIR BODY TYPE
AND HABITAT,

A SNAKE'S WORLD IS RICH
IN TACTILE CUES.

THEY RELY ON TOUCH TO MOVE
FROM PLACE TO PLACE,

HAVING RECEPTORS ON THEIR SKIN
THAT GUIDE THEM OVER THE GROUND,

UP A TREE,

OR IN THE WATER.

THEIR SENSE OF SMELL
IS ANOTHER STORY.

IT BEGINS WITH
THE FLICKERING FORKED TONGUE

WHICH PICKS UP SCENTS
FROM THE AIR.

WHEN DRAWN BACK, THE TWIN TIPS
TRANSFER THE SCENT PARTICLES

TO THE ROOF OF THE MOUTH,

NEAR A CHAMBER CALLED
THE JACOBSON'S ORGAN,

WHERE THE PARTICLES
ARE IDENTIFIED

AND THE INFORMATION
PASSED ON TO THE BRAIN.

SO, WHILE SNAKES DO HAVE
NOSTRILS FOR BREATHING,

IT'S THIS SOPHISTICATED
SENSE OF SMELL

THAT ENHANCES THEIR ABILITY
TO TRACK PREY, FIND MATES

AND ELUDE PREDATORS
WHEN NAVIGATING THE WORLD.

RESEARCHERS HAVE FOUND,
IN THE PAST,

SOME SNAKES REACHED
INCREDIBLE SIZES...

AS MUCH AS 43 FEET LONG
AND 2,500 POUNDS.

TODAY, GIANT SNAKES
ARE A MORE MODEST SIZE,

BUT THEY'RE STILL BIG.

THE INDIAN PYTHON, NATIVE
TO SOUTHERN ASIA, IS ONE.

AVERAGING ABOUT 12 FEET
AND WEIGHING 100 POUNDS,

THESE GIANTS LIVE
IN TROPICAL REGIONS

SO THEY CAN WARM UP
THEIR BODIES QUICKER.

OTHER LARGE SNAKES INCLUDE
THE ANACONDA,

THE BURMESE PYTHON

AND THE BOA CONSTRICTOR.

THESE SPECIES ARE KNOWN
FOR KILLING BY CONSTRICTION...

GRASPING PREY
WITH THEIR SHARP TEETH,

COILING THEIR BODIES AROUND IT,

AND SQUEEZING UNTIL
THE VICTIM'S CHEST COLLAPSES,

LUNGS DEFLATE
AND HEART STOPS PUMPING.

THEN, THE PROCESS
OF EATING BEGINS.

THANKS TO STRETCHY LIGAMENTS
IN THEIR JAWS,

SNAKES SWALLOW THEIR FOOD WHOLE.

Barrett: THIS IS ENABLED BY LOTS
OF DIFFERENT ADAPTATIONS

THAT THEY HAVE IN THEIR JAW
AND IN THEIR SKULL.

THEY HAVE
VERY HIGHLY FLEXIBLE LIGAMENTS

THAT ENABLE THEM
TO BE VERY FLUID

WHEN THEY'RE SWALLOWING PREY.

IT'S THESE HIGHLY FLEXIBLE
JOINTS THAT THEY'VE EVOLVED

TO BE ABLE TO EXPAND
AND CONTRACT

AND ACCEPT THIS VERY LARGE PREY.

[SCREECHING]

Narrator: A SNAKE'S FLEXIBLE JAW

MAKES IT CAPABLE
OF UNUSUAL CAPTURES.

THIS RAT SNAKE HAS
A BABY MAGPIE IN ITS MOUTH...

WHILE ITS MOTHER SCREECHES
IN PROTEST.

RAT SNAKES OFTEN CLIMB TREES
TO PLUNDER BIRD NESTS,

SEARCHING FOR EGGS
OR YOUNG HATCHLINGS.

THIS TIME, THE MOTHER
FREES HER BABY.

BUT THERE ARE OTHERS
STILL AT RISK.

[SCREECH]

[SCREECH]

WITHOUT THE ELEMENT OF SURPRISE,
THE SNAKE MUST DECIDE

WHETHER TO PURSUE
ANOTHER CHICK...

[SCREECH]

OR LOOK ELSEWHERE.

[SCREECHING]

REGARDLESS OF THEIR SIZE,

MOST SNAKES KILL
BY CONSTRICTION...

AND IT'S NOT LONG BEFORE
THIS SNAKE FINDS A VICTIM.

FIRST, THE BITE...

THEN THE STRUGGLE.

¶

CONSTRICTION IS GENERALLY
MORE EFFECTIVE

ON MAMMALS AND BIRDS,
WHICH BREATHE FREQUENTLY,

THAN ON CREATURES
LIKE REPTILES OR FISH.

BUT ONCE IN THE SNAKE'S GRIP,
DEATH IS MOMENTS AWAY.

¶

[BIRDS CHIRPING]

¶

DESPITE BEING LEGLESS,

SNAKES HAVE EVOLVED
WAYS OF GETTING AROUND,

DEPENDING ON THEIR
MUSCULAR SYSTEM

AND THE SCALES ON THEIR BODY.

THERE'S THE FAMILIAR
SIDE-TO-SIDE WAVE-LIKE MOTION...

THE STRAIGHTFORWARD,
CATERPILLAR-LIKE CRAWLING,

TYPICAL OF
HEAVIER-BODIED SNAKES...

THE STRETCH-AND-FOLD
ACCORDION MOTION...

AND SIDEWINDING,

USED BY THOSE SPECIES TRAVELING
LOOSE, WINDBLOWN SAND.

SNAKES ARE FOUND ON EVERY
CONTINENT EXCEPT ANTARCTICA,

WITH DIFFERENCES IN CLIMATE
AND HABITAT

INFLUENCING THE EMERGENCE
OF DIFFERENT SPECIES.

MILLIONS OF YEARS OF EVOLUTION

HAVE PRODUCED SNAKES
OF ASTONISHING VARIETY...

INCLUDING SOME WHO'VE DEVELOPED

A HIGHLY SPECIALIZED METHOD
OF CAPTURING PREY

THAT'S LIGHTNING QUICK...

AND DEADLY.

Narrator:
ABOUT 70% OF SNAKE SPECIES
KILL BY CONSTRICTION,

LITERALLY SQUEEZING THE LIFE
OUT OF THEIR PREY.

MOST OF THE REMAINING 30%

USE A MORE RECENTLY EVOLVED
DELIVERY SYSTEM...

THE SNAKE BITE...

WHICH INJECTS TOXIC VENOM
INTO THE VICTIM.

VENOM IS A NEWER WEAPON,
AN ADAPTATION THAT AROSE

BETWEEN 60 AND 80 MILLION
YEARS AGO.

IT CONSISTS OF TOXIC SECRETIONS

PRODUCED IN THE SNAKE'S
ORAL GLAND--

A KIND OF MODIFIED SALIVA--

THAT ENTERS
THE VICTIM'S BLOODSTREAM,

PARALYZING OR KILLING IT.

Barrett: SNAKE VENOM DELIVERY
DEPENDS ON THE SPECIES.

SOME ANIMALS ACTUALLY BITE
AND HOLD ON TO THEIR PREY

AND INJECT VENOM
OVER A LONG PERIOD OF TIME.

A LOT OF THOSE SPECIES
HAVE TOXINS IN THEIR VENOM

TO IMMOBILIZE THEIR PREY,

TO PREVENT THAT ANIMAL FROM
ACTUALLY HURTING THE SNAKE.

OTHER SNAKES
HAVE ACTUALLY EVOLVED

A DIFFERENT DELIVERY SYSTEM

WHERE THEY'RE ABLE TO ENVENOMATE
VERY QUICKLY WITH A QUICK BITE

AND RETRACT.

THAT ACTUALLY ALLOWS THE PREY
TO RUN AWAY,

BUT THE SNAKE IS ABLE
TO TRACK DOWN THAT PREY

AND CONSUME IT.

Narrator: THERE ARE TWO
MAIN TYPES OF SNAKE VENOM--

NEUROTOXIC, AFFECTING
THE VICTIM'S NERVOUS SYSTEM...

OR HEMOTOXIC, AFFECTING
THE CIRCULATORY SYSTEM.

BUT REGARDLESS OF ITS TYPE,

EACH INDIVIDUAL SNAKE PRODUCES
ITS OWN SPECIFIC VENOM.

OF THE ROUGHLY 600 KINDS
OF VENOMOUS SNAKES,

30 OR SO ARE COBRAS--

ONE OF THE MOST RECOGNIZABLE
SPECIES KNOWN.

ALL COBRAS ARE LARGE,
MEASURING UP TO TEN FEET LONG.

ON THE HUNT, THEY'LL CAPTURE
PREY BY STEALTH,

STAYING LOW TO THE GROUND,
WAITING TO AMBUSH THEM.

AND THEY HAVE SMALL, HOLLOW
FANGS FOR INJECTING VENOM.

WHILE COBRAS USE VENOM
FOR KILLING,

IT CAN ALSO BE USED
AS A DEFENSIVE WEAPON.

WHEN THREATENED, A COBRA
WILL TYPICALLY REAR UP,

FLARE OUT THE RIBS IN ITS NECK,

FLASHING ITS HOOD TO APPEAR
MORE MENACING.

SOME OF THEM GO EVEN FURTHER.

INSTEAD OF TANGLING
WITH A LARGER ENEMY CLOSE UP,

THE SPITTING COBRA WILL FORCE
AIR FROM ITS LUNGS,

WHILE A MUSCLE CONTRACTION
PROJECTS A TOXIC STREAM OF VENOM

OUT THROUGH ITS FANGS.

Barrett:
THEIR FANGS ACTUALLY HAVE
FORWARD-POINTING SLITS IN THEM

THAT ENABLE THEM
TO ACTUALLY DIRECT VENOM

OUT AWAY FROM THEIR BODY,

WHICH THEY USE TO SPRAY AT
THE EYES OF POTENTIAL PREDATORS.

[HISSING]

Narrator: THE COBRA CAN SPRAY
VENOM UP TO EIGHT FEET.

IF IT HITS THE EYES, IT CAUSES
SEVERE PAIN AND IRRITATION.

WITHOUT QUICK TREATMENT,

THE VICTIM'S CORNEA
MAY BE DESTROYED,

LEADING TO BLINDNESS.

THIS WEAPON IS
AN EVOLUTIONARY DEVELOPMENT

MILLIONS OF YEARS IN THE MAKING.

EVEN NEWBORN COBRAS COME
EQUIPPED TO SPIT VENOM.

¶

BUT THERE ARE OTHER SNAKES

WHOSE USE OF VENOM
IS MORE CONVENTIONAL.

FAR EASTERN EUROPE AND ASIA

IS HOME TO SEVERAL SPECIES OF
VENOMOUS SNAKES CALLED MAMUSHIS.

¶

Barrett:
THE MAMUSHI IS VERY ADAPTED
TO BEING A NOCTURNAL HUNTER.

ONE OF THE THINGS YOU'LL FIRST
NOTICE ABOUT THESE SNAKES

IS THAT THEY HAVE
A VERTICAL EYE SLIT,

WHICH HELPS THEM
TO BETTER TAKE IN

THE LOW LIGHT CONDITIONS
AT NIGHT.

Narrator: IN ADDITION, MAMUSHIS
HAVE INFRARED FACIAL PITS

ALLOWING THEM TO DETECT THE
PRESENCE OF WARM-BLOODED PREY.

Barrett: ESSENTIALLY THIS PIT
IS TO RECOGNIZE

THE HEAT SIGNATURE
COMING OFF OF AN ANIMAL.

THIS ABILITY HAS PROVEN
VERY ADVANTAGEOUS

TO PIT VIPERS IN GENERAL.

THEY'RE ALSO ABLE TO SENSE
ANIMALS WITHOUT ANY LIGHT.

RESEARCH HAS SHOWN THAT EVEN
WITH TAKING AWAY THEIR SIGHT

AND THEIR SENSE OF SMELL,

THEY'RE STILL ABLE
TO EFFECTIVELY HUNT.

Narrator: MAMUSHIS ARE KNOWN FOR
THEIR AGGRESSIVE DISPOSITION,

PREFERRING TO CONFRONT, RATHER
THAN FLEE FROM ADVERSARIES.

AND THIS CAN INDUCE
AN UNWELCOMED RESPONSE.

IN JAPAN, THE MAMUSHI IS OFTEN
CALLED THE SEVEN-STEP VIPER

BECAUSE ITS VENOM IS BELIEVED
TO IMMOBILIZE VICTIMS

WITHIN SEVEN STEPS
OF BEING BITTEN.

EACH YEAR IN THE COUNTRY,

THE MAMUSHI BITES
ABOUT 2,500 PEOPLE.

THOUGH FEW FATALITIES RESULT,

THE CONSEQUENCES ARE STILL
PAINFUL AND DEBILITATING,

WITH HOSPITAL RECOVERIES
TAKING AT LEAST A WEEK.

IN THE WILD,
MAMUSHIS ARE HUNTERS

THAT USE CAMOUFLAGE
TO DISGUISE THEIR APPROACH.

THERE'S A PAUSE TO ASSESS
THE SITUATION...

THEN A SLOW CRAWL
TOWARDS ITS PREY...

CONTINUALLY FLICKING ITS TONGUE,

ITS PITS PROVIDING
THERMAL CUES.

IN AN INSTANT
IT BITES THE VICTIM,

QUICKLY DELIVERING
A LOAD OF VENOM.

THEN ANOTHER BITE.

AND WITHIN MOMENTS,
THE VENOM IS AT WORK,

LEAVING THE ANIMAL BREATHING
ITS LAST BREATHS,

DESTINED TO BE
THE MAMUSHI'S MEAL.

[BIRDS CHIRPING]

OF ALL THE VENOMOUS SNAKES
IN THE WORLD,

THE BLACK MAMBA IS PERHAPS THE
MOST FEARED FOR ITS DEADLY BITE.

THIS LONG, SLENDER SNAKE
IS FOUND IN AFRICA--

IN TREES AND ALSO ON THE GROUND.

ALERT AND GRACEFUL,

IT HAS EXCELLENT VISION
AND IS EXTREMELY FAST...

CAPABLE OF SPEEDS
UP TO TEN MILES AN HOUR.

¶

DESPITE ITS NAME,
THE SNAKE IS USUALLY

GUN-METAL GRAY OR BROWN
IN COLOR, NEVER BLACK.

Barrett: BLACK MAMBAS ARE ONE

OF THE MOST STIGMATIZED
SNAKE SPECIES.

THEY ACTUALLY GET THEIR NAME NOT
FROM THE COLOR OF THEIR SCALES,

BUT THE DEEP INKY BLACK INSIDES
OF THEIR MOUTHS.

Narrator: THE BLACK MAMBA'S
VENOM HAS ADAPTED

TO SUIT THE PREDATOR'S NEEDS.

SINCE THE SNAKE'S DIET CONSISTS
MAINLY OF RODENTS

AND OTHER MAMMALS
WITH SHARP TEETH AND CLAWS,

IT REQUIRES A HIGHLY TOXIC,
FAST-ACTING VENOM

TO SUBDUE ITS PREY
WHILE AVOIDING INJURY.

AS A RESULT,
IT DELIVERS ITS VENOM

THROUGH A SERIES OF RAPID
STAB-AND-RELEASE BITES

IN ORDER TO ASSURE
ITS OWN SURVIVAL...

AND LIVE TO BITE ANOTHER DAY.

[BIRDS CHIRPING]

[RATTLING]

SNAKES USE VENOM BOTH
FOR KILLING AND FOR DEFENSE.

[RATTLING]

IT'S EVOLVED TO BE A TOXIC
COCKTAIL THAT, OVER TIME,

CAN ALSO CHANGE IN COMPOSITION

TO SUIT THE SNAKE'S
HABITAT AND PREY.

¶

BUT BEFORE ANY SNAKES CAN INJECT
VENOM, THEY MUST FIRST BE BORN.

AND THAT'S A STORY
WITH SOME VERY UNIQUE TWISTS.

Narrator:
THE PLACE IS MANITOBA, CANADA,

AN HOUR NORTH OF WINNIPEG.

IT'S EARLY SPRING,
AND A MALE GARTER SNAKE

EMERGES INTO THE WARMTH
FROM A DEN UNDERGROUND

AFTER WINTER HIBERNATION.

HIS TONGUE PROBES THE AIR
FOR A TELLTALE SCENT.

BUT HE'S NOT ALONE.

SOON, OTHER MALES SURFACE,

AND A RITUAL OF SURVIVAL
MANY MILLIONS OF YEARS OLD

IS ABOUT TO BEGIN.

IT'S CALLED SEX.

THE GARTER SNAKE'S
SEXUAL BEHAVIOR

INVOLVES AN INTENSE PHASE
ARISING IN THE SPRING.

AND DURING IT,
THOUSANDS OF MALES APPEAR,

SEARCHING FOR A FEMALE.

Barrett: IN MANITOBA,
THE UNIQUE COMBINATION

OF THEIR CLIMATE AND GEOLOGY

ENABLES THESE LARGE
CONGREGATIONS OF SNAKES.

TEMPERATURES IN MANITOBA
CAN GET AS LOW AS NEGATIVE 50,

AND THEY HAVE A NATURAL
LIMESTONE BEDROCK,

WHICH PROVIDES FEW OPPORTUNITIES
FOR THESE SNAKES

TO ACTUALLY OVER-WINTER
BELOW THE FROST LINE.

SO THE COMBINATION
OF VERY COLD TEMPERATURES

AND LIMITED PLACES
TO OVER-WINTER

CAUSES THESE HUGE NUMBERS
OF SNAKES,

AS MANY AS 10,000 IN ONE SPOT,
TO HAPPEN.

Narrator: THIS MASSIVE
CONGREGATION OF MALES

WAITS FOR THE FEMALES
TO EMERGE FROM THE DEN.

WHEN THEY DO,
THE FEMALES EMIT PHEROMONES,

WHICH TRIGGERS A FRENZY
OF EXCITEMENT,

RESULTING IN WHAT'S CALLED
A MATING BALL.

MOUNDS OF MALES
SWARM THE LARGER FEMALES.

THEY RUB THEIR HEADS
ON HER BACK,

WINDING AROUND HER,
TRYING TO MATE.

MANITOBA'S SPECTACULAR
GARTER SNAKE MATING BALL

IS A UNIQUE EVENT, OCCURRING
NOWHERE ELSE IN THE WORLD.

¶

DESPITE APPEARANCES HERE,

AMID THE SLITHERING
AND SLINKING,

THERE ARE NO SEXUAL
OR TERRITORIAL BATTLES

BEING FOUGHT.

WHEN THE FEMALE IS READY,
SHE'LL RAISE HER TAIL

AND THE NEAREST MALE
WILL MATE WITH HER.

THE UNION CAN LAST
FROM UNDER AN HOUR

TO SOMETIMES A WHOLE DAY.

THE OTHER MALES
WILL LOSE INTEREST IN HER

AND SEEK ANOTHER FEMALE.

¶

THE SUCCESSFUL SNAKE HAS A PLOY

TO KEEP THE FEMALE FROM BEING
IMPREGNATED BY OTHER MALES.

DURING MATING, HE DEPOSITS
A FLUID INTO HER

THAT HARDENS INTO A PLUG

AND ACTS AS A BARRIER
AGAINST OTHER MALE SPERM--

AN ENFORCED CHASTITY
THAT LASTS FOR SEVERAL DAYS.

THE MALE CAN TURN HIS ATTENTION
TO OTHER FEMALES,

KNOWING HIS SPERM CANNOT
BE REPLACED BY A RIVAL'S.

THE FEMALE WILL EJECT
THE PLUG LATER,

BUT DEPENDING ON HOW LONG
SHE'S RECEPTIVE TO MATING

AND HOW MANY ACTIVE MALES
ARE AROUND,

A SECOND OPPORTUNITY
MAY HAVE PASSED.

IN THE WORLD
OF THE MALE GARTER SNAKE,

ANY SCHEME THAT LEADS
TO SUCCESSFUL MATING

IS A GOOD SCHEME.

THREE MONTHS LATER,
THE IMPREGNATED FEMALE

WILL GIVE BIRTH TO AS MANY
AS 50 BABY GARTER SNAKES.

BUT THERE'S ALWAYS HOPE
FOR THOSE MALES

WHO MISS THEIR CHANCE THIS YEAR,

BECAUSE, LIKE CLOCKWORK,

THE MATING CYCLE
WILL HAPPEN AGAIN,

SAME TIME AND SAME PLACE,
NEXT YEAR.

¶

70% OF ALL SNAKE SPECIES
LAY EGGS

THAT EMERGE FROM THE FEMALE
WITH A HARD SHELL.

THE MOTHER WILL SEEK OUT
A SECLUDED SITE

THAT'S MOIST AND WARM
TO DROP HER EGGS,

LAYING AS MANY AS 40 AT A TIME.

¶

AFTER PLACING THE EGGS,

MOST FEMALE SNAKES
WILL ABANDON THE NEST.

BUT IN SOME INSTANCES,
LIKE RAT SNAKES,

THE MOTHER STAYS CLOSE BY.

SHE DOES THIS TO PROTECT
THE EGGS FROM PREDATORS

WHILE ALSO PROVIDING WARMTH,
WHICH HELPS THEM INCUBATE.

THIS MATERNAL BEHAVIOR
IS NOT TYPICAL

THROUGHOUT THE SNAKE WORLD.

ASIDE FROM GOING OUT TO HUNT,

THE RAT SNAKE MOTHER
WILL GUARD THE EGGS

FOR UP TO THREE MONTHS
BEFORE THEY HATCH.

¶

WHEN THE DAY ARRIVES,

A SNAKE'S HEAD CUTS OPEN
THE EGGSHELL

USING A SHARP GROWTH
ON ITS SNOUT,

CALLED AN EGG-TOOTH.

AFTER BREAKING THROUGH,

A FULLY DEVELOPED CREATURE
EMERGES FROM THE EGG...

AND LIFE BEGINS IN EARNEST.

THE NEWBORN RAT SNAKE CAN EXPECT
LITTLE PARENTAL PROTECTION

AND LITTLE IN THE WAY
OF PREDATOR TRAINING.

THERE'S ALSO LITTLE CONTACT
WITH ITS SIBLINGS.

IT MUST BE READY TO FACE
THE WORLD ON ITS OWN--

TO SURVIVE OR PERISH ALONE.

SOME 30% OF SNAKE SPECIES,
INCLUDING THE MAMUSHI,

GIVE BIRTH TO LIVE YOUNG,

WHERE THE EGGS ARE HELD
INSIDE THE FEMALE'S BODY

UNTIL THEY HATCH.

THE BABIES THEN EMERGE
FROM THE MOTHER

COVERED BY A THIN MEMBRANE

THAT SUPPLIED NUTRIENTS
DURING THEIR DEVELOPMENT.

BUT ONCE BORN, THE BABIES
BREAK FREE FROM IT.

SCIENTISTS HAVE FOUND

THAT SNAKES GIVING BIRTH
TO LIVE YOUNG

TEND TO INHABIT EXTREME
LATITUDES AND ELEVATIONS.

THIS SUGGESTS THAT LIVE BIRTHS
OCCUR IN COOLER CLIMATES

AND SERVE AS AN ADAPTATION
ENSURING THE YOUNG

RECEIVE CONSTANT HUMIDITY AND
TEMPERATURE FROM THEIR MOTHER.

JUST AS IMPORTANT, EGGS HIDDEN
INSIDE THE MOTHER'S BODY

ARE LESS VULNERABLE TO PREDATORS

THAN THOSE NESTING
ON THE GROUND.

LIKE THEIR EGG-HATCHING COUSINS,

MOST NEW LIVE-BORN SNAKES
ARE INDEPENDENT

AND STRIKE OUT ON THEIR OWN
SOON AFTER THEY EMERGE.

EXPERTS SAY THAT SOME 50%
OF YOUNG SNAKES

WON'T REACH THEIR FIRST YEAR,

DYING FROM STARVATION,
FREEZING DURING HIBERNATION

OR BEING KILLED BY A PREDATOR.

THIS IS A FAR DIFFERENT WORLD
THAN THE ONE IN THE WOMB...

AND IT'S A WORLD THEY'LL HAVE TO
ADAPT TO QUICKLY...OR ELSE.

Narrator: SNAKES CRAWL, SLITHER,
SLIDE OR WRIGGLE

OVER VIRTUALLY ANY BIT
OF DRY LAND ON EARTH,

HAVING ADAPTED
OVER MILLIONS OF YEARS

TO SURVIVE
IN A RANGE OF HABITATS.

BUT MANY SPECIES ALSO INHABIT
RIVERS, PONDS AND WETLANDS...

THEIR UNDULATING TERRESTRIAL
MOTION TRANSFERRING TO SWIMMING.

THE ASIAN TIGER SNAKE LURKS
AROUND STREAMS AND PONDS,

SEEKING OUT FROGS,
A STAPLE OF ITS DIET.

BORN NONVENOMOUS,
THE TIGER SNAKE ADAPTS

BY ALSO EATING POISONOUS TOADS,

CONVERTING THE TOXIC CHEMICALS
ON THEIR SKIN INTO VENOM

AND USING IT AGAINST PREDATORS--

BIOLOGICAL PROOF
THAT WHAT DOESN'T KILL YOU

MAKES YOU STRONGER.

THIS ASIAN SNAKE, CALLED
THE DOG-FACED WATER SNAKE,

IS FOUND IN SLOW-MOVING,
BRACKISH RIVERS,

TROPICAL MUDFLATS,
AS WELL AS FRESHWATER STREAMS.

THEY'RE STRONG SWIMMERS,
MOST ACTIVE DURING THE EVENING.

AND WHILE OCCASIONALLY
APPEARING ON LAND,

IT'S NOT THEIR COMFORT ZONE.

THE WATER IS WHERE THEY HUNT...

AND FISH ARE
THEIR MAIN FOOD SOURCE.

ITS NAME COMES
FROM THE PROMINENT EYES,

WITH ROUND PUPILS,
SITTING HIGH ON ITS HEAD,

SIMILAR TO A DOG.

IN ADAPTING TO THE ENVIRONMENT,

THE SNAKE HAS DEVELOPED
VALVED NOSTRILS,

WHICH CLOSE UNDERWATER,

AND LONG LUNGS
THAT HELP THEM FLOAT.

FINDING ITS PREY
IN THE SHALLOWS,

THE SNAKE IS RELENTLESS
IN PURSUIT.

¶

DOG-FACED SNAKES HAVE VENOM,

BUT IT'S RARELY POWERFUL ENOUGH
TO SUBDUE VICTIMS.

ITS FANGS ARE SMALL AND LOCATED
AT THE BACK OF ITS MOUTH--

NOT ALWAYS EFFICIENT FOR A KILL.

THIS TIME, A BATTLE ENSUES.

HERE, THE SNAKE SQUEEZES
THE STRUGGLING FISH IN ITS JAWS

AND SUBMERGES IT UNDERWATER,
IN AN EFFORT TO TIRE IT OUT.

¶

ONCE THE FISH BEGINS TO FALTER,

THE SNAKE WILL WRAP
SEVERAL COILS AROUND IT...

CONSTRICTING...
TO FINISH THE JOB.

¶

NEXT, THE SNAKE WILL BEGIN
SWALLOWING THE FISH--

A LABORIOUS TASK REQUIRING
PATIENCE AND DETERMINATION.

Barrett: SNAKES HAVE
A COUPLE ADAPTATIONS

TO BE ABLE TO HELP SWALLOW
LARGE PREY.

THEY'RE ABLE TO USE THEIR TEETH
A LITTLE BIT

TO GET TRACTION ON THIS ITEM
AND HELP WALK IT BACK.

THEIR HIGHLY FLEXIBLE JAWS
ENABLE THEM TO MOVE

DIFFERENT SIDES OF THEIR JAW
AT DIFFERENT TIMES

AND ACTUALLY BE ABLE TO HELP
FORCE IT DOWN INTO THEIR THROAT.

ONCE IT'S DOWN,
PARASTOLSIS TAKES PLACE,

WHICH ACTUALLY
IS THE MUSCLE ACTION

THROUGHOUT THE THROAT AREA

THAT HELPS PUSH IT DOWN
INTO THE STOMACH.

Narrator: IT'LL TAKE
ABOUT 30 MINUTES

FOR THE SNAKE
TO SWALLOW THE FISH,

WITH THE VENOM HELPING TO
BREAK DOWN AND DIGEST THE BODY

BEFORE IT REACHES THE STOMACH.

ONCE THIS MEAL IS DONE,
IT'LL BE AT LEAST A WEEK

BEFORE HUNGER WILL RETURN
THE SNAKE TO THE HUNT.

¶

[BIRDS CHIRPING]

IN THAILAND'S
HOT AND HUMID RAINFOREST...

DEEP IN THE MURK
OF THE WETLANDS...

A STRANGE AND WILY HUNTER
SKULKS...

A SNAKE THAT LIVES
ALMOST ENTIRELY ON FISH

AND HAS EVOLVED A DECEPTIVE
STRATEGY FOR CATCHING THEM.

¶

IN THE WATER, IT APPEARS
RIGID AND TWIG-LIKE.

ON ITS HEAD ARE TWO
ANTENNA-LIKE TENTACLES,

INSPIRING ITS NAME--
THE TENTACLED SNAKE.

¶

THE SNAKE ANCHORS ITSELF
TO PLANTS,

RIGIDLY EXTENDING
ALMOST THREE FEET.

BUT LIKE ANY SNAKE,
IT'S AN AIR-BREATHING REPTILE.

SO ABOUT TWICE AN HOUR IT'LL
NEED TO COME UP TO THE SURFACE.

THE TENTACLES AREN'T
MERELY DECORATIVE.

THEY DETECT WATER MOTION
AND, COMBINED WITH VISUAL CUES,

HELP THE SNAKE SEIZE ITS PREY.

IN THIS WORLD, FISH
ARE ESPECIALLY ELUSIVE.

WHEN SENSING A DISTURBANCE
IN THE WATER,

THEY SWIFTLY CHANGE DIRECTION,

DOING A C-SHAPED CURL
IN FIVE MILLISECONDS,

TO ESCAPE A THREAT.

BY CONTRAST, THE TENTACLED SNAKE
IS SLOWER,

TAKING AS MUCH
AS 15 MILLISECONDS

TO REACT TO THE FISH.

Barrett: FISH HAVE EVOLVED
TO BE QUICKER THAN SNAKES.

THE SNAKE GOES TO STRIKE
THAT FISH,

THE FISH HAS ALREADY
BEEN ABLE TO FLEE.

SO THE SNAKE HAS TO
FIGURE OUT A WAY

TO BE ABLE TO CATCH ITS PREY.

Narrator: IN THIS CONTEST
BETWEEN PREDATOR AND PREY,

THE CRAFTY TENTACLED SNAKE
HAS DONE JUST THAT.

Barrett: ONE OF THE COOLEST
ADAPTATIONS THAT THEY HAVE

IS A FISHING TECHNIQUE.

THEY'RE ABLE TO ANCHOR
THEMSELVES WITH THEIR TAIL

AND REMAIN VERY, VERY STILL.

AND WHAT THEY DO
IS CURL THEIR HEAD

INTO ALMOST AN UPSIDE-DOWN
J PATTERN.

Narrator: THE SNAKE USES
THE FISH'S ESCAPE RESPONSE,

THE C-SHAPED CURL,
TO ITS ADVANTAGE.

AS A FISH SWIMS NEARBY,

THE SNAKE'S TENTACLES FEEL
THE RIPPLE OF THE WATER,

AND IT REACTS.

Barrett: WHAT THAT SNAKE DOES IS
IT ACTUALLY TWITCHES ITS MUSCLES

ON THE OPPOSITE SIDE
OF ITS HEAD.

SO AS THAT FISH PULLS A 180,
THE SNAKE IS ALREADY THERE

AND HAS ANTICIPATED
WHERE IT'S GOING TO FLEE.

Narrator: THE SNAKE'S STRATEGY

SENDS THE STARTLED FISH
INTO ITS WAITING JAWS.

Barrett: AND SO THE SNAKE
IS ACTUALLY ABLE TO STRIKE,

KNOWING WHERE THE FISH
IS GOING TO BE

RATHER THAN WHERE
IT CURRENTLY IS.

AND THAT ANTICIPATION IS WHAT
GIVES IT A MUCH BETTER CHANCE

AT SUCCESS
OF CATCHING THAT FISH.

Narrator: THE TENTACLED SNAKE
HAS FOUND ITS NICHE

IN THE WATER.

BUT MANY OTHER SNAKE SPECIES

IN TROPICAL
AND SUBTROPICAL REGIONS

SPEND THEIR LIVES ABOVE GROUND,

LITERALLY IN THE TREES.

[BIRDS CHIRPING]

IN THIS LUSH WORLD,

WARM TEMPERATURES
AND HIGH ANNUAL RAINFALL

CREATE THICK, DENSE VEGETATION,

GIVING ARBOREAL SNAKE SPECIES

PLENTY OF COVER
AND ABUNDANT FOOD.

MANY OF THESE TREE-DWELLERS

HAVE ADAPTED TO THIS HABITAT
IN SPECIFIC WAYS.

THEY HAVE LONG,
SLENDER FOREPARTS

AND THICKER HIND ENDS,

AND IN SOME CASES

BRANCH-GRABBING
PREHENSILE TAILS.

THEY ALSO HAVE EXTRA MUSCULAR
RIGIDITY ON THEIR SIDES,

ALLOWING THEM TO SCALE
HIGH UP IN TREES...

AND STRETCH BETWEEN BRANCHES.

MOST ARBOREAL SNAKES
ARE GREEN OR BROWN IN COLOR

TO HELP THEM BLEND IN
WITH THE FOLIAGE

AND CONCEAL THEM
FROM PREDATORS OR PREY.

HERE, THEY'VE ALSO EVOLVED
A KEY ANATOMICAL ADAPTATION.

COMPARED TO TERRESTRIAL
OR AQUATIC SNAKES,

THE ARBOREAL SNAKE'S HEART
IS CLOSER TO ITS HEAD.

THIS COUNTERS THE EFFECTS
OF GRAVITY

ON THEIR CIRCULATORY SYSTEM,

WHICH OTHERWISE COULD LEAD
TO BLOOD POOLING DANGEROUSLY

IN THEIR LOWER BODY

AS THEY CLIMB UP A TREE
OR NAVIGATE HIGH BRANCHES.

BUT FOR SOME ARBOREAL CREATURES,

CLIMBING IS NOT
THE ONLY MODE OF TRAVEL.

THE RAIN FORESTS
OF SOUTHEAST ASIA

ARE THE SETTING
FOR A UNIQUE AIRSHOW.

AMONG THE FLIERS,
WALLACE'S FLYING FROG,

WHICH GOES AIRBORNE REGULARLY,

USING ITS WEBBED FEET TO LEAP
FROM PLACE TO PLACE.

¶

¶

SOME LIZARDS ALSO TAKE ADVANTAGE
OF THIS WAY OF GETTING AROUND,

FLYING AS MUCH AS 60 FEET
BETWEEN LANDING SPOTS.

¶

NOT TO BE OUTDONE, FIVE SPECIES
OF SNAKES IN THIS REGION

ALSO TAKE TO THE AIR...

INCLUDING THE PARADISE
FLYING SNAKE.

IT'S CAPABLE OF HURLING ITSELF
FROM A TREE BRANCH,

LIKE A RELEASED SPRING,
AND FLOATING THROUGH THE AIR.

BUT ITS NAME IS A MISNOMER.

Barrett:
THE PARADISE FLYING SNAKE

IS NOT ACTUALLY FLYING.

IT'S ONE OF THE GREAT GLIDERS
OF THE ANIMAL WORLD.

WHAT IT'S ABLE TO DO IS SPREAD
ITS RIBS AND CATCH THE AIR

AS THEY PROPEL THEMSELVES
OFF OF THESE HIGH BRANCHES.

¶

Narrator:
WHAT HAPPENS IN MIDAIR

IS A MATTER OF SHEER
ADAPTIVE GENIUS.

IN GLIDE MODE, THE SNAKE SPREADS
ITS RIBCAGE LIKE A PARACHUTE,

WHILE COMPRESSING ITS BACK
INTO ITS STOMACH.

TO INCREASE BUOYANCY,
THE SNAKE FLATTENS ITS FRAME,

WHICH ACTS
AS LIFT-GENERATING WINGS...

AND BY RIPPLING ITS BODY
BACK AND FORTH,

IT CAN ACTUALLY STEER IN MIDAIR.

Barrett: SO WHEN THESE SNAKES
LAUNCH THEMSELVES

OUT OF THE TREE,

THEY'RE ACTUALLY FALLING
AT A FAIRLY STEEP ANGLE,

ABOUT 62 DEGREES.

BUT AS THEY'RE ABLE
TO FLATTEN THOSE RIBS OUT

AND CATCH THE AIR,

THEY'RE ABLE TO SLOW
THEIR DESCENT

TO ABOUT A 13-DEGREE ANGLE

AND MAKE IT MUCH MORE SOFT
AS THEY LAND.

Narrator:
THE PARADISE FLYING SNAKE

CAN GLIDE OVER 300 FEET
IN THE AIR.

BUT THE GLIDING IS NOT JUST
FOR GETTING AROUND.

IT'S USED TO HUNT.

¶

THIS TIME A LIZARD, SEEMINGLY
BLENDED INTO THE FOLIAGE.

THE SNAKE QUIETLY INCHES
ALONG A BRANCH.

THE LIZARD SENSES
ITS PRESENCE...

AND PARACHUTES TO SAFETY.

¶

THE SNAKE SPRINGS FROM THE TREE
AND ATTACKS.

¶

IT CURLS ITS BODY
AROUND THE HAPLESS PREY

AND SQUEEZES THE LIFE OUT OF IT.

¶

SOON, THE SNAKE BEGINS
SWALLOWING IT,

ENDING ANOTHER SUCCESSFUL HUNT.

AQUATIC AND TREE-DWELLING SNAKES

HAVE DEVELOPED
MANY ADAPTIVE SOLUTIONS

TO SURVIVE
IN THEIR ENVIRONMENTS.

BUT IN ANOTHER HABITAT,

A REMARKABLE SPECIES OF SNAKE
HAS EVOLVED,

HAVING SOME OF THE MOST POTENT
VENOM IN THE WORLD.

Narrator:
WITH 71% OF THE EARTH'S SURFACE

COVERED BY WATER,

IT'S NO SURPRISE THAT
THE EVER-ENDURING SNAKE

ADAPTED TO LIFE IN THE DEEP.

IN THESE OCEAN CURRENTS,

OVER 60 SPECIES,
KNOWN AS SEA SNAKES,

HAVE EVOLVED TO BECOME
ADEPT SWIMMERS AND HUNTERS.

Barrett: SEA SNAKES ARE FOUND
PREDOMINANTLY IN THE PACIFIC,

AND THESE SNAKES EVOLVED
FROM LAND SNAKES

THAT FOUND ADAPTATIONS TO
SURVIVE IN A MARINE ENVIRONMENT.

SOME OF THESE ADAPTATIONS
THAT THEY HAVE

ARE THE FLATTENING
OF THEIR BODY,

ESPECIALLY THE TAIL,
THAT MAKES THEM

MUCH MORE EFFECTIVE
AT SWIMMING THROUGH THE WATER.

THEY'VE ALSO LOST
THEIR VENTRAL SCALES,

WHICH LAND SNAKES USE
TO LOCOMOTE ACROSS TERRAIN.

Narrator: TRUE SEA SNAKES
WILL NEVER SLITHER ON LAND.

EVERYTHING THEY NEED--
FOOD, SHELTER, A MATE--

IS ON THE OCEAN FLOOR,
AT DEPTHS UP TO 200 FEET.

¶

SOME SWIMMING SPECIES EVOLVED

INDEPENDENTLY
OF TRUE SEA SNAKES,

LIVING IN BOTH MARINE
AND TERRESTRIAL ENVIRONMENTS.

SEA KRAITS HAVE KEPT MANY OF
THEIR ANCESTRAL CHARACTERISTICS.

Barrett: SEA KRAITS SEEM TO BE
THE LEAST EVOLVED

OF ALL DIFFERENT SPECIES
OF SEA SNAKES.

THEY STILL RETAIN
THE LATERAL SCALATION

THAT ALLOWS THEM TO BE
FUNCTIONAL ON LAND.

THEY'RE STILL OCCASIONALLY FOUND
ON LAND,

AND UNLIKE OTHER SEA SNAKES,

THEY'RE STILL TIED TO LAND
FOR BREEDING,

AND THAT'S WHERE
THEY LAY THEIR EGGS AS WELL.

Narrator:
ALTHOUGH SIDE AND BELLY SCALES

MAY SLOW SEA KRAITS DOWN
IN THE WATER,

THEY CAN STILL SWIM 60% FASTER

THAN THEIR LAND-BOUND
COBRA RELATIVES.

AND THEIR VENOMOUS FANGS
PACK A FATAL PUNCH...

MORE TOXIC
THAN A DEADLY KING CORBA.

THEY NEED THAT POTENCY
TO QUICKLY IMMOBILIZE PREY...

SO THAT THEIR MEALS
CAN'T SWIM AWAY.

BUT SEA KRAITS ARE RARELY
AGGRESSIVE TOWARDS HUMANS.

IN FACT, THEY'RE QUITE DOCILE.

ULTIMATELY, ALL SNAKES
ARE JUST TRYING TO SURVIVE...

AND USUALLY,
IT'S IN THEIR BEST INTEREST

TO AVOID CONFRONTATION.

BUT AS RESILIENT AS SNAKES ARE,

THEY CAN'T ALWAYS STAY
OUT OF OUR WAY.

POPULATIONS OF SNAKE SPECIES
WORLDWIDE ARE IN DECLINE.

THOUGH THE EXACT REASONS
ARE UP FOR DEBATE,

HABITAT LOSS IS A FACTOR.

SNAKES COMPLETELY ADAPTED
TO THEIR HABITATS OVER MILLENNIA

AND NOW PERFORM AN IMPORTANT
ROLE IN OUR ENVIRONMENT.

Barrett: SNAKES FILL A CRITICAL
ROLE IN OUR ECOSYSTEM.

THEY ARE PRIMARILY
RODENT HUNTERS

AND CAN KEEP A LOT
OF OUR PEST SPECIES DOWN.

JUST A SINGLE SNAKE
IS RESPONSIBLE

FOR KEEPING THOUSANDS
OF PESTS, LIKE MICE,

OUT OF OUR HABITATS.

Narrator:
KEEPING THEM OUT OF FARMLANDS
AND AWAY FROM HOMES.

RODENTS ARE RESPONSIBLE FOR
SPREADING OVER 35 HUMAN DISEASES

ACROSS THE GLOBE,

FROM THE HANTAVIRUS
TO THE PLAGUE.

¶

THERE ARE OTHER WAYS SNAKES
SERVE A USEFUL PURPOSE,

ASIDE FROM PEST CONTROL.

SNAKE VENOM HAS LONG PLAYED
A THERAPEUTIC ROLE

IN PLACES LIKE CHINA AND INDIA,

TREATING EVERYTHING
FROM ASTHMA TO HEADACHES.

BY THE 1960s,
VENOM HAD MADE ITS WAY

INTO WESTERN MEDICAL PRACTICE
AND RESEARCH.

TODAY, THE KILLER COCKTAIL
MAY ACTUALLY PROVE A WEAPON

IN THE FIGHT AGAINST DISEASE.

AT TEXAS A&M'S NATURAL TOXINS
RESEARCH CENTER IN KINGSVILLE,

SCIENTISTS COLLECT AND STUDY
VARIOUS TYPES OF SNAKE VENOM.

THEY'RE EXPLORING HOW
PURIFIED VENOM MOLECULES

MAY BE USED IN TREATING STROKES
AND HEART ATTACKS

AND EVEN STOP THE SPREAD
OF CANCEROUS TUMORS.

OVERALL, SNAKES HAVE
A GREAT TRACK RECORD,

THOUGH FEARED, SCORNED,
AND KILLED INDISCRIMINATELY.

GENERATION AFTER GENERATION,

THEY'VE PROVEN THEY HAVE WHAT IT
TAKES TO PREVAIL ON EARTH.

Barrett:
SNAKES ARE VERY RESILIENT.

FROM THE FOSSIL RECORD,
WE'VE SEEN THAT SNAKES

HAVE BEEN EVOLVING
FOR 150 MILLION YEARS.

NO GROUP OF ANIMALS

IS GOING TO BE ABLE TO SURVIVE
FOR 150 MILLION YEARS

UNLESS THEY'VE BECOME MASTERS
AT ADAPTATION AND SURVIVING.

Narrator: FROM ONE COMMON
ANCESTOR LONG AGO

TO THOUSANDS OF SPECIES TODAY...

FROM EVIL INCARNATE...

TO ONE OF EVOLUTION'S
GREATEST SUCCESS STORIES...

THE SNAKE CONTINUES MOVING
FORWARD ON THE PATH OF SURVIVAL.