NARRATOR: IN THE BIG PACIFIC...

SOME GIANTS MUST EAT NON-STOP.

AND OTHER GIANTS MAY NOT EAT FOR A YEAR.

AN ARMY OF MOUTHS THAT CAN DESTROY A FOREST, A KILLER WITH A HUNDRED MOUTHS, AND THE BIGGEST MOUTH IN THE OCEANS.

IN THE PACIFIC OCEAN, IT'S EAT OR BE EATEN.

64 MILLION SQUARE MILES.

[SQUAWKING] ONE THIRD OF OUR PLANET.

THE BIGGEST OCEAN ON EARTH... WITH THE LARGEST APPETITE.

[SONAR PINGS] NARRATOR: IN THE SEAS OFF SAN DIEGO, THE LARGEST ANIMAL TO EVER LIVE...

THE BLUE WHALE.

ONE HUNDRED FEET LONG, LONGER THAN A BASKETBALL COURT.

TWO HUNDRED TONS, THE WEIGHT OF 28 AFRICAN ELEPHANTS.

BUT IT FEEDS ON THE TINIEST OF PREY: A CRUSTACEAN ABOUT THE SIZE OF A PAPER CLIP.

EACH KRILL WEIGHS ONLY A FEW HUNDREDTHS OF AN OUNCE.

THE WHALE NEEDS TO SWALLOW 40 MILLION A DAY.

THANKFULLY, KRILL SWARM BY THE BILLIONS... UP TO 60,000 IN A SINGLE CUBIC YARD.

IT TARGETS THE DENSEST PART OF THE SWARM... AND ENGULFS A PATCH OF OCEAN THAT WEIGHS AS MUCH AS THE WHALE ITSELF.

A MOUTH SO LARGE, A HUNDRED PEOPLE COULD FIT INSIDE.

BUT IT'S TOOTHLESS... WITH A TONGUE THE SIZE OF AN ELEPHANT.

IT FORCES THE WATER BACK OUT THROUGH SIEVE-LIKE BALEEN PLATES ATTACHED TO ITS UPPER JAW... FILTERING THE KRILL AND SWALLOWING IT, HALF A TON AT A TIME.

BUT SATISFYING AN APPETITE AS BIG AS THIS IS NOT EASY, EVEN IN THE LARGEST OCEAN ON EARTH.

EVERY YEAR, THE WHALE MUST TRAVEL MANY THOUSANDS OF MILES IN SEARCH OF SWARMS AS GOOD AS THIS.

TO SURVIVE IN THE BIG PACIFIC, YOU NEED TO MAKE THE MOST OF EVERY MOUTHFUL.

[SONAR PINGING] ANOTHER PACIFIC GIANT, THE MANTA RAY.

15 FEET ACROSS, ONE AND A HALF TONS.

IT GROWS HUGE ON PREY EVEN SMALLER THAN THE BLUE WHALE'S... PLANKTON SO TINY, IT'S JUST A HAZE IN THE WATER.

TO SURVIVE ON THIS MICROSCOPIC SOUP, IT FEEDS ALMOST CONSTANTLY.

UNLIKE THE WHALE, IT'S NOT LIMITED BY WHAT FITS IN A SINGLE MOUTHFUL.

A RAY BREATHES BY EXTRACTING OXYGEN FROM WATER FLOWING THROUGH ITS GILLS.

TO KEEP BREATHING, IT KEEPS MOVING, EXPLOITING THE CONTINUOUS FLOW OF WATER TO FEED... FILTERING PLANKTON WITH FEATHER-LIKE "RAKERS" DEEP WITHIN ITS GILLS.

SOMETIMES IT GETS LUCKY, A RICH AGGREGATION OF FOOD.

WHAT LOOKS LIKE A GRACEFUL PIROUETTE IS REALLY A FEEDING FRENZY AMID A DENSE CLOUD OF PLANKTON.

IT'LL WORK THIS SWEET SPOT UNTIL IT'S ALL SCOOPED UP.

ONE PACIFIC GIANT IS SO VORACIOUS, A SINGLE MOUTH WON'T DO.

[SONAR PINGING] IT DOESN'T LOOK LIKE MUCH, A DISK THE SIZE OF A GRAIN OF RICE, DRIFTING THROUGH THE YELLOW SEA.

BUT IN LESS THAN A YEAR, IT'LL GROW BIGGER THAN AN ADULT HUMAN.

RIGHT NOW, HOWEVER, IT'S LITTLE MORE THAN A MOUTH-- A MOUTH JUST 3 HUNDREDTHS OF AN INCH ACROSS.

SMALLER THAN A PIN HEAD...

BUT ITS APPETITE IS ALREADY MONSTROUS.

IT DEVOURS ANYTHING THAT COMES ITS WAY, SO LONG AS IT'S MICROSCOPIC, BUT CALORIE BY CALORIE, ITS DIET ADDS UP.

FOR 6 MONTHS, THE RAMPAGE OF GLUTTONY CONTINUES UNTIL THE TRANSFORMATION IS COMPLETE.

THE NOMURA'S JELLYFISH.

TWO YARDS ACROSS, AS HEAVY AS A MALE LION.

NOT JUST ONE OF THE LARGEST JELLYFISH IN THE PACIFIC, BUT ON THE ENTIRE PLANET.

AND IT'S BUILT TO DO ONE THING-- GROW.

NO BONES TO NOURISH, NO COMPLEX ORGANS TO MAINTAIN, AND VERY LITTLE ENERGY WASTED ON SWIMMING.

IT JUST DRIFTS WITH THE CURRENTS, TRAILING DEATH IN ITS WAKE.

HUNDREDS OF TENTACLES BRISTLE WITH THOUSANDS OF NEMATOCYSTS, TINY BARBS THAT INJECT A PARALYZING BREW INTO ITS PREY.

DEADLY AS IT LOOKS, ONLY 8 PEOPLE HAVE DIED FROM A RUN-IN WITH A NOMURA.

WE AREN'T ON ITS DIET.

EVEN SMALL FISH ARE TOO BIG.

INSTEAD, THEY FIND SHELTER FROM PREDATORS WITHIN ITS TENTACLES, SO LONG AS THEY DODGE THE LETHAL BARBS.

NO, THE NOMURA FEEDS ON MICROSCOPIC PLANKTON... BECAUSE ONE THING ABOUT THE GIANT THAT DOESN'T GET BIGGER IS ITS MOUTH.

TO GET THIS BIG, IT MAKES MORE MOUTHS, EACH AS TINY AS THE ONE IT FIRST STARTED WITH.

BY THE TIME IT'S FULLY GROWN, ITS ARMS BRIM WITH HUNDREDS OF THEM...

SO TINY, THEY'RE VIRTUALLY INVISIBLE TO THE NAKED EYE.

BUT TOGETHER, THEY SWALLOW AN OLYMPIC-SIZE POOL OF PLANKTON-RICH WATER EVERY DAY.

THESE GIANTS BELONG TO ONE OF THE OLDEST LINEAGES ON THE PLANET, SURVIVING UNCHANGED FOR MILLIONS OF YEARS.

BUT EACH LIFE IS BRIEF, JUST 4 SEASONS.

IT'S BORN, IT GROWS, IT BREEDS, IT DIES.

BUT NOT BEFORE EACH FEMALE RELEASES MORE THAN A BILLION TINY EGGS INTO THE PACIFIC... TO RENEW THE VORACIOUS CYCLE OF CHOWING DOWN AND BULKING UP.

BUT SIZE ISN'T EVERYTHING WHEN IT COMES TO FINDING FOOD IN THE BIG PACIFIC.

[SONAR PINGING] ON THIS REMOTE ATOLL IN THE MARSHALL ISLANDS, A CUNNING PREDATOR DEFIES LOGIC...

EMERGING FROM THE DEEP TO HUNT ON DRY LAND.

NO, THIS ISN'T THE PREDATOR.

THESE ARE "LIGHT FOOT" CRABS IN SEARCH OF FOOD.

AS THE TIDE EBBS, IT EXPOSES RICH PICKINGS OF SEAWEED.

AND HERE, AMID THE ISOLATED POOLS, THEY SHOULD BE SAFE FROM PREDATORS OF THE DEEP.

A PEPPERED MORAY EEL, THE MOST AMPHIBIOUS OF ALL MORAYS.

IT LIVES ON THE REEF, BENEATH THE WAVES, BUT ON THIS TINY ISLAND, IT'S LEARNED TO FEED ASHORE... A BEHAVIOR THAT'S NEVER BEEN FILMED BEFORE.

EELS CAN BREATHE AIR FOR SHORT PERIODS, SO LONG AS THEY KEEP THEIR GILLS MOIST...

WHICH IT DOES BY DIPPING IN AND OUT OF THE POOLS.

IT USES BOTH SIGHT AND SCENT TO HUNT.

BUT WILL THE LIGHT FOOT CRAB LIVE UP TO ITS NAME?

NO CONTEST.

BUT HOW DID THIS PHENOMENAL BEHAVIOR COME ABOUT?

THERE'S ANOTHER EEL IN THE SAME POOL.

COULD THESE ANIMALS HAVE LEARNED FROM EACH OTHER?

NOBODY KNOWS FOR SURE, BUT THEY DON'T SEEM TO BE TOO KEEN ON COOPERATION.

THE TIDE IS TURNING.

TIME FOR THE EELS TO SLINK BACK WHERE THEY CAME FROM... THEIR HUNGER SATISFIED UNTIL THE NEXT LOW TIDE.

[SONAR PINGING] THE PACIFIC ALSO HAS ISLANDS YOU RARELY SEE...

UNDERWATER ARCHIPELAGOS OF CORAL... 3/4 OF ALL THE CORAL IN THE WORLD...

SUSTAINING 1/4 OF MARINE ANIMALS.

THE CORAL REEF IS A CONUNDRUM... FULL OF THINGS TO EAT... AND FULL OF PLACES TO HIDE.

NOT EASY TO CATCH A MEAL.

BUT WHAT IF YOU DON'T PLAY BY THE RULES?

THE LIONFISH.

WITH A FLAMBOYANT CLOAK, A LION'S MANE, IT SCORNS STEALTH.

IT LOOKS MORE LIKE A CLOWN THAN A KILLER, AND THAT'S THE SECRET OF ITS SUCCESS.

IT LACKS THE STREAMLINED BODY OF OTHER OCEAN PREDATORS.

ITS LONG FINS AND FEATHERY FRINGE RULE OUT HIGH-SPEED ATTACKS, MAKING THE LIONFISH MORE OF A TROJAN HORSE.

THE SHRIMP SEES THE LIONFISH IN ALL ITS GARISH GLORY, NOT THE PREDATOR WITHIN.

NUDGING CLOSER, IT USES ITS OUTLANDISH FINS TO CORRAL ITS PREY.

THE VICTIM SEEMS MESMERIZED.

GONE IN A GULP.

THE LATEST THEORY IS THAT PREY JUST DON'T PERCEIVE THE LIONFISH AS A THREAT BECAUSE IT DOESN'T BEHAVE LIKE A TYPICAL PREDATOR.

AND WITH VENOM-TIPPED SPINES FOR DEFENSE, THE LIONFISH IS UNSTOPPABLE... ONE OF THE MOST SUCCESSFUL HUNTERS IN THE ENTIRE PACIFIC...

SO SUCCESSFUL THAT SOME RESEARCHERS CALL IT "THE TERMINATOR."

BUT THE LIONFISH ISN'T THE ONLY ONE WITH A TRICK UP ITS SLEEVE.

A BLUESTREAK WRASSE.

THIS TIME, IT'S THE TERMINATOR WHO'S MESMERIZED.

THE WRASSE DOES A JIG TO CALM THE LIONFISH... AND ANNOUNCE IT'S OPEN FOR BUSINESS.

CLEANER WRASSE GET NEARLY ALL OF THEIR FOOD FROM OTHER FISH... RIDDING THEM OF PARASITES, DEAD TISSUE, AND DEBRIS... ON THEIR BODIES, FINS, AND YES, MOUTHS... BECAUSE EVEN TERMINATORS NEED TOOTHPICKS.

[SONAR PINGING] ON THE WILD COASTS OF CALIFORNIA, IT'S PATIENCE THAT REWARDS ONE OF THE PACIFIC'S MOST UNASSUMING CARNIVORES.

TO SURVIVE THE PACIFIC SWELLS, IT SPENDS ITS LIFE ANCHORED TO A ROCK.

NOT A PLANT, BUT A GIANT GREEN ANEMONE.

DESPITE ITS BOASTFUL NAME, THIS RELATIVE OF CORAL GROWS ONLY ABOUT 10 INCHES ACROSS... AND ITS PREY TENDS TO MATCH ITS SIZE-- SMALL FISH AND SHELLFISH.

JUST LIKE ITS JELLYFISH COUSINS, IT PARALYZES AND IMMOBILIZES...

BUT ONCE IN A WHILE, THE ANEMONE HAS EYES BIGGER THAN ITS STOMACH.

IT'S JUST A QUESTION OF HOW TO GET ONE.

[SQUAWKING] NARRATOR: DOUBLE-CRESTED CORMORANTS AND THEIR RAVENOUS YOUNG.

TOO YOUNG TO FEED THEMSELVES.

CORMORANTS ARE SKILLED DIVERS, YET SWIMMING IS STILL HAZARDOUS, BUT NOT BECAUSE OF ANEMONES.

THIS SHORE IS REGULARLY BATTERED BY BIG OCEAN SWELLS...

BUT CORMORANT PARENTS MUST FISH IN ALL WEATHER.

FOR THE ANEMONE, IT'S JUST A MATTER OF TIME.

IT GRASPS THE DEAD CORMORANT AS IT PASSES.

ITS MOUTH IS SO FLEXIBLE, IT CAN OPEN AS WIDE AS ITS ENTIRE BODY TO INGEST PREY.

BEHIND THE MOUTH, POWERFUL SPHINCTER MUSCLES LOCK ONTO THE MEAL.

THE ANEMONE IS A LIVING STOMACH, AND ITS GUT IS AS EXPANDABLE AS ITS MOUTH.

DIGESTION HAS ALREADY BEGUN, EVEN AS THE ANEMONE EATS.

IT WILL EAT THE FLESH AND LATER EXPEL THE BONES.

THE OCEAN SWELL PULLS THE MEAL INTO A SECOND ANEMONE'S GRIP.

A SLO-MO TUG OF WAR.

SOON, ALL THAT REMAINS OF THE CORMORANT... IS A FEATHER.

THE SHORES OF THE PACIFIC ARE SOME OF ITS MOST FERTILE WATERS.

[SONAR PINGING] OFF THE COAST OF MEXICO, EVERY FALL, NUTRIENTS FROM THE DEEP ARE BROUGHT UP TO THE SURFACE... AND THERE'S AN EXPLOSION OF LIFE.

A PLANKTON BLOOM...

CREATING A NURSERY FOR THE SHYEST OF PACIFIC GIANTS.

A WHALE SHARK, THE WORLD'S BIGGEST FISH.

THEY CAN GROW 50 FEET LONG, WITH A MOUTH 5 FEET WIDE.

BUT THIS IS ACTUALLY A YOUNGSTER, A MERE 20 FEET OR SO.

EVERY YEAR, YOUNG WHALE SHARKS RETURN TO A HANDFUL OF SHALLOW BAYS IN THE SEA OF CORTEZ...

APPEARING RIGHT AT THE PEAK OF THE PLANKTON BLOOM.

IT'S A MYSTERY HOW THEY KNOW WHERE TO COME, OR WHEN, BUT SCIENTISTS NOW THINK THEY KNOW WHY.

THEY MAY BE THE WORLD'S LARGEST FISH, BUT WHEN THEY ARE YOUNG, THEY'RE VULNERABLE.

MANY ARE KILLED EACH YEAR BY PREDATORY MAKO SHARKS AND KILLER WHALES.

THEIR SAFETY LIES IN GETTING BIGGER FAST, SO THEY GATHER IN THESE SECLUDED BAYS TO GROW.

WHALE SHARKS ARE THE ULTIMATE FILTER FEEDERS, SURPASSING EVEN THE MANTA RAY.

WHILE CASUALLY SWIMMING, THEY CAN FILTER 1/4 OF AN OLYMPIC SWIMMING POOL EVERY HOUR.

BUT WHEN THEY HIT A PLANKTON MOTHER LODE, THEY STOP AND TURN ON THE PUMPS.

A SHARK THE SIZE OF A SCHOOL BUS, HOVERING IN THE OCEAN, SUCKING UP PLANKTON.

NO OTHER FISH CAN PUMP WATER THROUGH ITS FILTERS LIKE THIS, A TRAIT AS UNIQUE AS IT IS VORACIOUS.

A CLOUD OF PLANKTON GONE IN SECONDS, LIKE A PUFF OF SMOKE.

WITH SUCH A RICH FOOD SOURCE AND SUCH A POWERFUL WAY TO EXTRACT IT, THEY BULK UP LIKE BODYBUILDERS...

GROWING MORE THAN TWO FEET FOR EVERY TIME THEY VISIT HERE.

WHEN THEY REACH A RESPECTABLE 25 FEET LONG, THEY'LL NO LONGER NEED THIS NURSERY FOR OCEAN GIANTS.

WHERE THEY GO FROM HERE AND HOW THEY SURVIVE, NO ONE KNOWS.

BUT SATELLITE TAGS ARE BEGINNING TO SHOW US HOW FAR AND WIDE THEY ROAM.

FROM THE SEA OF CORTEZ, THEY TRAVEL THE OPEN OCEAN, LOOKING FOR THE RICHEST POCKETS OF PLANKTON.

ONE WHALE SHARK CROSSED TO THE OTHER SIDE OF THE PACIFIC, ENDING UP JUST SOUTH OF BIKINI ATOLL, 5,500 MILES AWAY.

THE SIZE OF THE PACIFIC IS HARD TO COMPREHEND.

A LIQUID UNIVERSE, AND WITHIN IT, UNIQUE WORLDS... EACH ONE A NEW OPPORTUNITY FOR FINDING A MEAL.

[SONAR PINGING] THERE'S NO PLACE ON EARTH LIKE THEM-- THE GALAPAGOS ISLANDS-- MORE THAN A HUNDRED VOLCANIC ISLANDS AND OUTCROPPINGS, ONLY 4 INHABITED.

AN EVOLUTIONARY CAULDRON... HARBORING BIZARRE LIFE.

[SQUAWKING] BUT ITS SHORES ARE LAVA-CLAD AND BARREN, SO WHERE DOES A LIZARD FIND FOOD?

THE GALAPAGOS ARE HOME TO THE WORLD'S ONLY MARINE IGUANA.

IT DIVES DOWN TO MORE THAN 50 FEET, WHERE MEADOWS OF RICH ALGAE OFFER ALL THE SUSTENANCE IT NEEDS.

SHARP CLAWS KEEP IT ANCHORED TO THE BOTTOM IN THE STRONG OCEAN SWELL...

WHILE A BLUNT NOSE ALLOWS RAZOR TEETH TO CUT CLOSE TO THE ROCKS, SCRAPING OFF THE NUTRITIOUS COATING OF ALGAE.

THE MARINE IGUANA CAN HOLD ITS BREATH FOR MORE THAN AN HOUR, BUT A TYPICAL DIVE LASTS NO MORE THAN 10 MINUTES.

TO THEIR ANCESTORS, THE SEA WAS HOSTILE.

THEY WERE MOST LIKELY TREE DWELLERS, CAST AWAY HERE ON A RAFT OF DRIFTWOOD FROM SOUTH AMERICA, 600 MILES AWAY.

BUT WITH NOTHING TO EAT ON THIS BARREN ROCK, THEY WERE FORCED TO TAKE UP THE LIFE AQUATIC.

THERE'S A REASON ITS DIVES ARE TYPICALLY BRIEF.

IGUANAS ARE COLD-BLOODED.

BASKING IS VITAL.

THEY GET A DOUBLE DOSE OF HEAT FROM THE SUN'S RAYS AND THE WARM BLACK ROCKS.

SURVIVING ON A DIET OF SALTY SEAWEED WITH NO PERMANENT FRESH WATER WOULD BE IMPOSSIBLE WITHOUT ANOTHER EVOLUTIONARY TRICK.

THE BUILDUP OF SALT IN ITS BLOODSTREAM IS FILTERED BY A GLAND IN ITS NOSE AND THEN EXPELLED.

THE KEY TO SURVIVAL IN A SNEEZE.

BUT THE BEST-KNOWN CREATURE IN THE GALAPAGOS IS THE ONE THE ISLANDS ARE NAMED AFTER.

"GALAPAGOS" IS THE OLD SPANISH WORD FOR "TORTOISE."

WITNESS THE LARGEST TORTOISE ON EARTH, THE WEIGHT OF 3 GROWN PEOPLE.

THEY CAN COVER A THOUSAND FEET IN AN HOUR.

THIS WOULD TAKE A HUMAN ABOUT 4 MINUTES TO WALK.

THEY MAY BE SLOW, BUT LIKE THEIR COUSIN OF FABLE, THEY'RE WINNERS IN A RACE FOR FOOD.

OVER MILLENNIA, THESE GIANT TORTOISES HAVE BECOME MASTERS OF SURVIVAL IN THIS UNFORGIVING LAND... MIGRATING WITH THE SEASONS IN SEARCH OF THE BEST FOOD.

ON THE SUMMIT OF ONE OF THE GALAPAGOS' GREAT VOLCANOES, RECENT RAINS HAVE CREATED A LUSH TORTOISE PARADISE.

[BUZZING] A CHANCE TO FATTEN UP ON THE RICH FLUSH OF NEW GRASS.

BUT GALAPAGOS TORTOISES SPEND THE BULK OF THEIR DAY DOING NOTHING... UP TO 16 HOURS A DAY, FOR MORE THAN A HUNDRED YEARS.

IN LEAN TIMES, THEY CAN LIVE OFF THEIR FAT FOR A WHOLE YEAR, WITHOUT FOOD OR WATER.

LIFE IN THE SLOW LANE CONSERVES ENERGY... A TIME-TESTED STRATEGY IN THIS OTHERWORLDLY OUTPOST... [DISTANT BIRD SQUAWKING] UNTIL THE WORLD BARGED IN.

TODAY, THE GALAPAGOS ARE AN ULTIMATE DESTINATION FOR WILDLIFE TOURISM...

THE LATEST IN 5 CENTURIES OF CONTACT BETWEEN OUTSIDER AND NATIVE.

BUT WITH THE PEOPLE CAME OTHER MAMMALS--GOATS.

[BLEATING] THEY RAVAGED MEADOWS AND FORESTS, DESTROYING THE TORTOISES' FOOD SUPPLY.

A SPECIES MILLIONS OF YEARS OLD WAS ABOUT TO LOSE THE RACE TO SURVIVE.

YET EVEN AS HUMAN INVASION PLUNGED THE TORTOISE INTO PERIL, WE UNWITTINGLY THREW IT A LIFELINE... A FORBIDDEN FRUIT... GUAVA-- SUCCULENT, JUICY, BUT LIKE THE GOATS, BROUGHT HERE BY PEOPLE.

THE SLUGGISH TORTOISE ADAPTED WITH WHIPLASH SPEED.

ON SOME ISLANDS, GUAVA IS NOW THEIR FRUIT OF CHOICE, A MAINSTAY OF THEIR DIET.

GOATS, MEANWHILE, HAVE ALL BUT VANISHED, ERADICATED BY PARK RANGERS BECAUSE OF THE DAMAGE THEY CAUSED.

THINGS ARE LOOKING UP FOR THE TORTOISE.

BUT AS THEY TRAVEL THEIR ANCIENT TRAILS, THEY DEPOSIT THE SEEDS OF THE FOOD THEY EAT...

PLAYING THEIR PART IN NEW CHANGE.

TODAY, MORE THAN HALF THE PLANTS HERE ARE AS FOREIGN AS THE GOATS.

IT MAY BE THAT SLOW AND STEADY IS PAYING OFF FOR THE TORTOISE.

BUT THE GALAPAGOS IS A FINELY TUNED LABORATORY OF EVOLUTION.

NO ONE KNOWS WHO THE FUTURE WINNERS AND LOSERS WILL BE IN THIS RACE OF APPETITES.

BUT IT'S NOT JUST IN EXOTIC CORNERS OF THE PACIFIC WHERE APPETITE HAS SUCH AN IMPACT ON LIFE.

MORE FAMILIAR SHORES CONCEAL EQUALLY RICH AND COMPLEX WORLDS.

[SONAR PINGING] THE CALIFORNIA COAST.

[SEA GULLS CRYING] BENEATH THE WAVES, FORESTS OF GIANT KELP.

THESE GREAT FRONDS RISE 150 FEET FROM THE OCEAN FLOOR AND REACH FOR THE LIGHT.

AN UNDERWATER HABITAT THAT STRETCHES ALMOST UNINTERRUPTED FROM CALIFORNIA TO THE TIP OF ALASKA.

KELP IS SO VIGOROUS, IT CAN GROW TWO FEET IN ONE DAY.

LIKE CORAL REEFS, IT OFFERS SHELTER FOR COUNTLESS SPECIES.

THIS IS ONE OF THE MOST DIVERSE ECOSYSTEMS IN THE PACIFIC.

FOR ONE CREATURE, SEAWEED IS ALSO FOOD.

THE RED URCHIN.

IT LOOKS LIKE AN UNDERSEA PORCUPINE, AND IT'S MORE FORMIDABLE THAN ITS NAME IMPLIES... BRISTLING WITH DEFENSIVE SPINES UP TO 3 INCHES LONG, SPROUTING FROM A HARD SHELL.

THEY'RE DESIGNED TO BREAK OFF IN THEIR ATTACKERS.

THE URCHIN CAN ALWAYS GROW MORE.

THEY HAVE MORE THAN A THOUSAND ALL-TERRAIN FEET... WITH SUCKERS ON THE ENDS, SO THEY CAN PRETTY MUCH GO ANYWHERE.

THOUGH THEY LACK EYES, THEY CAN ACTUALLY SEE THROUGH LIGHT-SENSITIVE CELLS ON THEIR FEET.

BUT THEY FOLLOW THEIR NOSES TO FEED.

THEY ATTACH THEMSELVES TO THE BASE THAT ANCHORS KELP TO THE SEABED.

BUILT TO WITHSTAND VIOLENT STORMS, THESE "HOLD FASTS" ARE STRONG AND FIBROUS.

BUT SOME URCHINS' TEETH CAN CUT THROUGH STONE... AND BEHIND THEM, THE URCHIN IS ALL STOMACH.

AND IT HAS A VORACIOUS APPETITE FOR KELP FLESH.

IN JUST A FEW MONTHS, A FOREST IS REDUCED TO A DESERT.

BUT THE KELP FOREST ISN'T DEFENSELESS.

IT HAS A GUARDIAN...

THE SEA OTTER.

IT MAY BE THE CUTEST CREATURE IN THE OCEAN, BUT IT HAS A VORACIOUS APPETITE FOR URCHINS.

THE OTTER PLAYS SUCH A VITAL ROLE IN THIS ECOSYSTEM, IT'S A KEYSTONE SPECIES OF THE BIG PACIFIC.

AND TO THINK WE NEARLY LOST THEM.

MORE THAN A CENTURY AGO, SEA OTTERS WERE HUNTED TO THE BRINK OF EXTINCTION FOR THEIR PELTS.

BARELY 2,000 REMAINED WHEN THEY WERE PROTECTED IN 1911.

AS OTTERS VANISHED, URCHINS MULTIPLIED, AND NATURE'S BALANCE WAS THROWN WILDLY OUT OF WHACK.

ITS FLATTENED TAIL AND WEBBED FEET PROPEL IT EFFORTLESSLY TO THE BOTTOM... UP TO 300 FEET DOWN.

THE SPINY DEFENSES OF THE SEA URCHIN ARE NO MATCH FOR THE OTTER'S CLAWS.

THEY CRUNCH THROUGH THE HARD SHELL WITH UNIQUELY CHISELED TEETH, BUT IT'S THEIR APPETITE THAT MAKES THEM SO LETHAL.

ONE OTTER CAN DEVOUR 1,500 URCHINS IN A SINGLE DAY, ABOUT 1/3 ITS OWN BODY WEIGHT.

AND WHERE OTTERS THRIVE, SO DO THE GREAT FORESTS OF KELP.

THE KELP, IN TURN, DO ANOTHER VITAL JOB.

EVERY YEAR, THE PACIFIC'S KELP FORESTS ABSORB 40 MILLION TONS OF CARBON FROM THE ATMOSPHERE.

IN THE BIG PACIFIC, THE KEY TO EVERY APPETITE IS BALANCE.

NEXT TIME ON BIG PACIFIC A MISSION TO UNCOVER THE GREAT WHITE'S SECRET MATING HABITS A LOOK AT AN UNLIKELY PARTNERSHIP OF SURVIVAL AND AN ENORMOUS WAVE OF LIFE LANDS ON THE BEACH TO LAUNCH THE NEXT GENERATION PASSION DRIVES THE PACIFIC OCEAN "BIG PACIFIC" IS AVAILABLE ON BLU-RAY AND DVD.

THE COMPANION BOOK IS ALSO AVAILABLE.

TO ORDER, VISIT SHOPPBS.ORG OR CALL 1-800-PLAY-PBS.

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