Original subtitles

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.