Original subtitles

David Attenborough:\NDWARFED BY THE VAST EXPANSE

OF THE OPEN OCEAN,

THE BIGGEST ANIMAL THAT HAS EVER\NLIVED ON OUR PLANET.

A BLUE WHALE, 30 METERS LONG\NAND WEIGHING OVER 200 TONS.

IT'S FAR BIGGER\NTHAN EVEN THE BIGGEST DINOSAUR.

ITS TONGUE WEIGHS\NAS MUCH AS AN ELEPHANT.

ITS HEART IS THE SIZE OF A CAR,

AND SOME OF ITS BLOOD VESSELS\NARE SO WIDE

THAT YOU COULD SWIM DOWN THEM.

ITS TAIL ALONE IS THE WIDTH\NOF A SMALL AIRCRAFT'S WINGS.

ITS STREAMLINING,\NCLOSE TO PERFECTION,

ENABLES IT TO CRUISE\NAT 20 KNOTS.

IT'S ONE OF THE FASTEST ANIMALS\NIN THE SEA.

THE OCEAN'S LARGEST INHABITANT

FEEDS ALMOST EXCLUSIVELY\NON ONE OF THE SMALLEST --

KRILL, A CRUSTACEAN\NJUST A FEW CENTIMETERS LONG.

GATHERED IN A SHOAL,

KRILL STAIN THE SEA RED,

AND A SINGLE BLUE WHALE IN A DAY\NCAN CONSUME 40 MILLION OF THEM.

DESPITE THE ENORMOUS SIZE\NOF BLUE WHALES,

WE KNOW VERY LITTLE ABOUT THEM.

THEIR MIGRATION ROUTES\NARE STILL A MYSTERY,

AND WE HAVE ABSOLUTELY NO IDEA\NWHERE THEY GO TO BREED.

THEY ARE A DRAMATIC REMINDER

OF HOW MUCH WE STILL HAVE\NTO LEARN ABOUT THE OCEAN

AND THE CREATURES\NTHAT LIVE THERE.

OUR PLANET IS A BLUE PLANET.

OVER 70 PERCENT OF IT\NIS COVERED BY THE SEA.

THE PACIFIC OCEAN ALONE\NCOVERS HALF THE GLOBE.

YOU CAN FLY ACROSS IT NON-STOP\NFOR 12 HOURS

AND STILL SEE NOTHING MORE\NTHAN A SPECK OF LAND.

THIS SERIES WILL REVEAL

THE COMPLETE NATURAL HISTORY\NOF OUR OCEAN PLANET

FROM ITS FAMILIAR SHORES

TO THE MYSTERIES\NOF ITS DEEPEST SEAS.

BY VOLUME,

THE OCEAN MAKES UP\N97 PERCENT

OF THE EARTH'S\NINHABITABLE SPACE,

AND THE SHEER QUANTITY\NOF MARINE LIFE IT CONTAINS

FAR EXCEEDS THAT\NWHICH INHABITS THE LAND.

BUT LIFE IN THE OCEAN IS NOT\NEVENLY SPREAD.

IT'S REGULATED

BY THE PATH OF CURRENTS\NCARRYING NUTRIENTS,

AND THE VARYING POWER\NOF THE SUN.

IN THIS FIRST PROGRAM,\NWE WILL SEE

HOW THESE TWO FORCES INTERACT

TO CONTROL THE DISTRIBUTION\NOF LIFE

FROM THE CORAL SEAS\NTO THE POLAR WASTES.

THE SHEER PHYSICAL POWER\NOF THE OCEAN

DOMINATES OUR PLANET.

IT PROFOUNDLY INFLUENCES\NTHE WEATHER OF ALL THE WORLD.

WATER VAPOR RISING FROM IT\NFORMS THE CLOUDS

AND GENERATES THE STORMS

THAT ULTIMATELY\NWILL DRENCH THE LAND.

THE GREAT WAVES THAT ROAR IN\NTOWARDS THE SHORES

ARE DRAMATIC DEMONSTRATIONS\NOF ITS POWER.

WAVES ORIGINATE FAR OUT AT SEA.

THERE, EVEN GENTLE BREEZES\NCAN CAUSE RIPPLES,

AND RIPPLES GROW INTO SWELLS.

OUT IN THE OPEN OCEAN,\NUNIMPEDED BY LAND,

SUCH SWELLS CAN BECOME GIGANTIC.

IT'S ONLY WHEN AN OCEAN SWELL\NEVENTUALLY REACHES SHALLOW WATER

THAT IT STARTS TO BREAK.

AS IT APPROACHES THE COAST,

THE WATER AT THE BOTTOM\NOF THE SWELL

IS SLOWED BY CONTACT\NWITH THE SEABED.

THE TOP OF THE SWELL,\NSTILL TRAVELING FAST,

STARTS TO ROLL OVER,

AND SO THE WAVE BREAKS.

THE OCEAN NEVER RESTS.

HUGE CURRENTS,\NSUCH AS THE GULF STREAM,

KEEP ITS WATERS CONSTANTLY\NON THE MOVE ALL ROUND THE GLOBE.

IT'S THESE CURRENTS,\NMORE THAN ANY OTHER FACTOR,

THAT CONTROL THE DISTRIBUTION\NOF NUTRIENTS

AND LIFE IN THE SEAS.

A TINY ISLAND LOST\NIN THE MIDST OF THE PACIFIC.

IT'S THE TIP OF A HUGE MOUNTAIN

THAT RISES PRECIPITOUSLY\NFROM THE SEA FLOOR

THOUSANDS OF METERS BELOW.

THE NEAREST LAND\NIS 300 MILES AWAY.

ISOLATED SEAMOUNTS\NLIKE THIS ONE

CREATE OASES\NWHERE LIFE CAN FLOURISH

IN THE COMPARATIVELY EMPTY\NEXPANSES OF THE OPEN OCEAN.

BUT ALL THE CREATURES THAT SWIM\NBESIDE IT WOULD NOT BE HERE

WERE IT NOT\NFOR ONE KEY FACTOR --

THE DEEP OCEAN CURRENTS.

FAR BELOW THE SURFACE, THEY\NCOLLIDE WITH THE ISLAND'S FLANKS

AND ARE DEFLECTED UPWARDS,

BRINGING WITH THEM\NFROM THE DEPTHS

A RICH SOUP OF NUTRIENTS.

SUCH UPWELLINGS ATTRACT\NGREAT CONCENTRATIONS OF LIFE.

MOST OF THE FISH HERE\NARE PERMANENT RESIDENTS

FEEDING ON THE PLANKTON --

THE TINY\NFLOATING PLANTS AND ANIMALS

THAT ARE NOURISHED\NBY THE RICHNESS

BROUGHT UP FROM THE DEPTHS --

AND THEY IN TURN ATTRACT\NVISITORS FROM THE OPEN OCEAN.

TUNA.

THE PLANKTON FEEDERS\NARE EASY TARGETS.

ALL THIS ACTION ATTRACTS\NEVEN LARGER PREDATORS.

SHARKS.

HUNDREDS OF SHARKS.

THESE SILKY SHARKS ARE NORMALLY\NOCEAN-GOING SPECIES,

BUT THE SEAMOUNTS\NIN THE EASTERN PACIFIC,

LIKE COCOS, MAPELO,\NAND THE GALAPAGOS,

ATTRACT SILKIES IN HUGE GROUPS

UP TO 500 STRONG.

SILKIES SEEM TO SPECIALIZE\NIN TAKING INJURED FISH

AND CONSTANTLY CIRCLE SEAMOUNTS

ON THE LOOKOUT FOR THE CHANCE\NTO DO SO.

BUT SILKIES ARE NOT\NTHE ONLY VISITORS.

HAMMERHEADS GATHER IN SOME OF\NTHE LARGEST SHARK SHOALS

TO BE FOUND\NANYWHERE IN THE OCEAN.

SOMETIMES, THOUSANDS WILL CIRCLE\NOVER A SINGLE SEAMOUNT.

BUT THESE SHARKS ARE NOT HERE\NFOR FOOD.

THEY HAVE COME\NFOR ANOTHER REASON.

SOME OF THE LOCALS\NPROVIDE A CLEANING SERVICE.

FOLLOWING THE LAST EL NIÑO YEAR,

WHEN A RISE\NIN WATER TEMPERATURES

CAUSED MANY SHARKS TO SUFFER\NFROM FUNGAL INFECTIONS,

THE NUMBER OF HAMMERHEADS\NVISITING THE SEAMOUNTS

REACHED RECORD LEVELS.

Attenborough: NUTRIENTS ALSO\NWELL UP TO THE SURFACE

ALONG THE COASTS\NOF THE CONTINENTS.

THIS IS NATAL ON SOUTH AFRICA'S\NEASTERN SEABOARD.

IT'S JUNE,\NAND JUST OFF-SHORE,

STRANGE BLACK PATCHES\NHAVE APPEARED.

THEY LOOK LIKE IMMENSE\NOIL SLICKS UP TO A MILE LONG.

BUT THIS IS A LIVING SLICK --

MILLIONS AND MILLIONS

OF SARDINES\NON A MARINE MIGRATION

THAT, IN TERMS OF SHEER BIOMASS,

RIVALS THAT OF THE WILDEBEEST\NON THE GRASSLANDS OF AFRICA.

THESE FISH LIVE\NFOR MOST OF THE TIME

IN THE COLD WATERS\NSOUTH OF THE CAPE,

BUT EACH YEAR\NTHE COASTAL CURRENTS REVERSE.

THE WARM AGULHAS CURRENT

THAT USUALLY FLOWS DOWN\NFROM THE NORTH

HAS BEEN DISPLACED BY COLD WATER\NCOMING UP FROM THE SOUTH,

AND THAT HAS BROUGHT UP\NRICH NUTRIENTS.

THEY IN TURN HAVE CREATED\NA BLOOM OF PLANKTON,

AND THE SARDINES\NARE NOW FEASTING ON IT.

AS THE SARDINES TRAVEL NORTH,

A WHOLE CARAVAN OF PREDATORS\NFOLLOW THEM.

THOUSANDS OF CAPE GANNETS\NTRACK THE SARDINES.

THEY NESTED OFF THE CAPE\NAND TIMED THEIR BREEDING

SO THAT THEIR NEWLY FLEDGED\NCHICKS CAN JOIN THEM

IN PURSUING THE SHOALS.

BELOW WATER, HUNDREDS OF SHARKS\NHAVE ALSO JOINED THE CARAVAN.

THESE ARE BRONZE WHALER SHARKS,

A COLD-WATER SPECIES\NTHAT NORMALLY LIVES

MUCH FURTHER SOUTH.

THESE THREE-METER SHARKS

CUT SUCH GREAT SWATHES\NTHROUGH THE SARDINE SHOALS

THAT THEIR TRACKS ARE CLEARLY\NVISIBLE FROM THE AIR.

HARRIED BY PACKS OF PREDATORS

AND SWEPT IN\NBY THE ACTION OF THE WAVES,

THE SARDINE SHOALS ARE PENNED\NCLOSE TO THE SHORE.

COMMON DOLPHIN ARE COMING IN\NFROM THE OPEN OCEAN

TO JOIN THE FEAST.

THERE ARE OVER A THOUSAND\NOF THEM

IN THIS ONE SCHOOL.

WHEN THEY CATCH UP\NWITH THE SARDINES,

THE ACTION REALLY BEGINS.

WORKING TOGETHER, THEY DRIVE\NTHE SHOAL TOWARDS THE SURFACE.

IT'S EASIER FOR THE DOLPHINS\NTO SNATCH FISH UP HERE.

NOW THE SARDINES HAVE NO ESCAPE.

THANKS TO THE DOLPHINS,

THE SARDINES HAVE COME WITHIN\NTHE DIVING RANGE OF THE GANNETS.

HUNDREDS OF WHITE ARROWS\NSHOOT INTO THE SEA,

LEAVING LONG TRAILS OF BUBBLES\NBEHIND EACH DIVE.

NEXT TO JOIN THE FRENZY\NARE THE SHARKS.

SHARKS GET VERY EXCITED\NWHEN DOLPHINS ARE AROUND.

THAT MAY BE BECAUSE THEY\NCAN FEED PARTICULARLY WELL

ONCE THE DOLPHINS\NHAVE DRIVEN THE SARDINES

INTO MORE COMPACT GROUPS\NNEAR THE SURFACE.

AS THE FRENZY CONTINUES,

WALLS OF BUBBLES DRIFT UPWARDS.

THEY ARE BEING RELEASED\NBY THE DOLPHINS,

WORKING TOGETHER IN TEAMS.

THEY USE THE BUBBLES

TO CORRAL THE SARDINES\NINTO EVER TIGHTER GROUPS.

THE SARDINES SELDOM CROSS\NTHE WALL OF BUBBLES

AND CROWD CLOSER TOGETHER.

BUBBLE NETTING IN THIS WAY

ENABLES THE DOLPHINS TO GRAB\NEVERY LAST TRAPPED SARDINE.

JUST WHEN THE FEASTING\NSEEMS TO BE ALMOST OVER,

A BRYDE'S WHALE.

THE SURVIVORS HEAD ON\NNORTHWARDS,

AND THE CARAVAN OF PREDATORS\NFOLLOWS THEM.

Attenborough: EVERY EVENING,

THE DISAPPEARANCE\NOF THE SUN BELOW THE HORIZON

TRIGGERS THE LARGEST\NMIGRATION OF LIFE

THAT TAKES PLACE ON OUR PLANET.

ONE THOUSAND MILLION TONS\NOF SEA CREATURES

ASCEND FROM THE DEEP OCEAN

TO SEARCH FOR FOOD\NNEAR THE SURFACE.

THEY GRAZE ON THE PHYTOPLANKTON\NUNDER COVER OF DARKNESS.

EVEN SO, THEY ARE FAR FROM SAFE.

OTHER MARINE HUNTERS\NFOLLOW THEM,

SOME TRAVELING UP\NFROM HUNDREDS OF METERS BELOW.

AT DAWN,\NTHE WHOLE PROCESSION RETURNS

TO THE SAFETY\NOF THE DARK DEPTHS.

THE PACIFIC COAST OF COSTA RICA

ON A VERY SPECIAL NIGHT.

IT'S JUST AFTER MIDNIGHT,\NAND THE TIDE IS COMING IN.

THE MOON IS IN ITS LAST QUARTER,

EXACTLY HALFWAY\NBETWEEN FULL AND NEW.

FOR WEEKS,\NTHE BEACH HAS BEEN EMPTY,

BUT THAT IS ABOUT TO CHANGE.

AT HIGH TIDE, TURTLES\NSTART TO EMERGE FROM THE SURF.

AT FIRST, THEY COME\NIN ONES AND TWOS,

BUT WITHIN AN HOUR,

THEY ARE APPEARING\NALL ALONG THE BEACH.

THEY ARE ALL FEMALE\NRIDLEY'S TURTLES,

AND OVER THE NEXT\NSIX DAYS OR SO,

400,000 WILL VISIT\NTHIS ONE BEACH

TO LAY THEIR EGGS IN THE SAND.

AT THE PEAK TIME, 5,000\NARE COMING AND GOING EVERY HOUR.

THE TOP OF THE BEACH\NGETS SO CROWDED

THAT THEY HAVE TO CLAMBER\NOVER ONE ANOTHER

TO FIND A BARE PATCH

WHERE THEY CAN DIG A NEST HOLE.

A QUARTER OF THE WORLD'S\NPOPULATION OF RIDLEY'S TURTLES

COME TO THIS ONE BEACH\NON A FEW KEY NIGHTS EACH YEAR.

THE REST OF THE TIME,

THEY ARE WIDELY DISTRIBUTED\NTHROUGH THE OCEAN,

SEARCHING FOR FOOD,

MOST, HUNDREDS OF MILES AWAY\NFROM HERE.

THIS MASS NESTING IS CALLED\NAN ARRIBADA.

HOW IT'S COORDINATED\NIS A MYSTERY,

BUT WE DO KNOW THAT ARRIBADAS\NSTART

WHEN THE MOON IS EITHER IN\NITS FIRST OR ITS LAST QUARTER.

FORTY MILLION EGGS ARE LAID\NIN JUST A FEW DAYS.

BY SYNCHRONIZING THEIR NESTING\NIN THIS WAY, THE FEMALES ENSURE

THAT SIX WEEKS LATER,\NTHEIR HATCHLINGS WILL EMERGE

IN SUCH ENORMOUS NUMBERS\NTHAT PREDATORS ON THE BEACH

ARE OVERWHELMED,

AND A SIGNIFICANT PROPORTION\NOF THE BABY TURTLES

WILL GET PAST THEM\NAND MAKE IT TO THE WATER.

BUT WHY DO THE FEMALES\NUSE A CUE FROM THE MOON

TO HELP IN SYNCHRONIZE\NTHEIR NESTING?

PART OF THE ANSWER TO THAT

BECOMES CLEAR AT DAWN\NON THE FOLLOWING MORNING.

THE DAY SHIFT OF PREDATORS

ARE ARRIVING\NFOR THEIR FIRST MEALS.

VULTURES HAVE LEARNT\NTHAT THE RETURNING TIDE

CAN WASH FRESHLY LAID EGGS\NOUT OF THE SAND.

THE RISK OF EGGS' BEING EXPOSED\NBY THE SURF

MAY BE PART OF THE REASON WHY\NTURTLE ARRIBADAS TEND TO OCCUR

AROUND THE LAST OR FIRST QUARTER\NOF THE MOON.

IT'S ON SUCH DAYS AS THIS,

WHEN THE MOON IS NEITHER FULL\NNOR NEW,

THAT THE TIDES ARE WEAKEST

AND THE SEA IS LIKELY\NTO BE CALMER.

SO AT THESE TIMES IT'S EASIER\NFOR THE FEMALE TURTLES

TO MAKE THEIR WAY\NTHROUGH THE SURF,

AND THERE'S LESS CHANCE OF THEIR\NEGGS' BEING WASHED

OUT OF THE SAND\NAND BEING TAKEN BY THE VULTURES.

Attenborough: THE SUN'S POSITION\NRELATIVE TO THE EARTH

CHANGES THROUGH THE YEAR,

AND IT'S THIS\NTHAT PRODUCES THE SEASONS.

IN THE NORTH, SPRING COMES

AS THE SUN BEGINS TO RISE\NHIGHER IN THE SKY.

OFF THE COAST\NOF NORTHWEST AMERICA,

THE SEAS ARE TRANSFORMED

BY THE INCREASING STRENGTH\NOF THE SUNSHINE.

HERE IN ALASKA,\NTHE COASTAL WATERS TURN GREEN

WITH A SUDDEN BLOOM\NOF PHYTOPLANKTON.

HERRING THAT HAVE SPENT\NTHE WINTER FAR OUT TO SEA

TIME THEIR RETURN\NTO THE SHALLOW WATERS

TO COINCIDE WITH THIS BLOOM.

THEY COME IN VAST NUMBERS\NAND INITIATE

ONE OF THE MOST PRODUCTIVE\NFOOD CHAINS IN ALL THE OCEANS.

HUMPBACK WHALES ARE AT THE TOP\NOF THAT FOOD CHAIN.

THEY HAVE SPENT THE WINTER

BREEDING IN THE WARMER\NTROPICAL WATERS OFF HAWAII,

BUT THERE WAS LITTLE FOOD\NFOR THEM THERE.

THIS HERRING BONANZA\NPROVIDES THE VAST MAJORITY

OF THEIR FOOD FOR THE YEAR.

STELLAR AND CALIFORNIAN\NSEA LIONS

ALSO RETURN FROM THE OPEN OCEAN

EACH YEAR\NTO FEAST OFF THE HERRING.

THE HERRING THEMSELVES, HOWEVER,\NHAVE NOT COME HERE FOR FOOD.

THEY ARE ABOUT TO BREED.

NOTHING DETERS THEM

AS THEY HEAD\NFOR EVEN SHALLOWER WATERS.

NOW THE WATERS ARE SO SHALLOW

THAT GLAUCOUS-WINGED GULLS

ARE ABLE TO SNATCH LIVE FISH\NFROM JUST BELOW THE SURFACE.

IN SPITE OF THESE ATTACKS\NAND LOSSES,

THE HERRING SWIM ON\NUNTIL THEY REACH THE VEGETATION

THAT THE FEMALES NEED\NIF THEY ARE TO LAY.

EACH FEMALE PRODUCES\NAROUND 20,000 EGGS,

AND THEY'RE VERY STICKY.

THE MALES ARRIVE SOON AFTER\NTHE FEMALES HAVE SPAWNED

AND RELEASE THEIR SPERM\NIN VAST, MILKY CLOUDS.

SOON, THE EXCESSES\NOF THE HERRINGS' SEXUAL SPREE

CREATES A THICK WHITE SCUM\NON THE SURFACE.

THROUGH THE SEASON,\NCURDS OF SPERM CLOG THE SHORES

FOR HUNDREDS OF MILES

FROM BRITISH COLUMBIA\NIN THE SOUTH

ALL THE WAY\NTO ALASKA IN THE NORTH.

AFTER A FEW DAYS, THIS GIGANTIC\NSPAWNING COMES TO AN END,

AND THE HERRING\NHEAD BACK OUT TO DEEPER WATERS,

LEAVING BEHIND THEM\NFERTILIZED EGGS

PLASTERED ON EVERY ROCK\NAND STRAND OF VEGETATION.

THEY TIME THEIR SPAWNING

SO THAT TWO WEEKS LATER,\NWHEN THESE EGGS START TO HATCH,

THE ANNUAL PLANKTON BLOOM

WILL HAVE REACHED ITS HEIGHT,

AND THE NEWBORN FISH FRY\NWILL HAVE PLENTY TO EAT.

BUT IN THE MEANTIME,\NALL THESE EGGS PROVIDE FOOD

FOR ARMIES OF DIFFERENT ANIMALS

BOTH BELOW AND ABOVE\NTHE SURFACE.

MILLIONS OF BIRDS ARRIVE

TO COLLECT A SHARE\NOF THE HERRINGS' BOUNTY.

SOME OF IT IS EASILY GATHERED,

FOR MILLIONS OF EGGS HAVE BEEN\NWASHED UP ONTO THE SHORE.

THIS ENCAPSULATED ENERGY

IS PARTICULARLY VALUABLE\NTO MIGRATING BIRDS.

THESE SURFBIRDS ARE ON THEIR WAY

TO THEIR BREEDING GROUNDS\NIN THE ARCTIC,

AND THEY HAD TO COME DOWN\NTO REFUEL.

STRANDED HERRING EGGS\NARE JUST WHAT THEY NEED.

BONAPARTE GULLS COLLECT THE EGGS

JUST BELOW THE SURFACE\NOF THE WATER.

FARTHER OUT IN THE BAY,

HUGE FLOCKS OF DUCKS\NHAVE GATHERED.

THEY'RE MOSTLY SURF SCOTERS --

DIVING DUCKS THAT CAN FEED\NOFF THE BOTTOM

SEVERAL METERS DOWN.

THERE ARE SUCH HUGE QUANTITIES\NOF EGGS

THAT EVEN SUCH A BIG ANIMAL\NAS A BEAR

FINDS IT WORTHWHILE\NTO COLLECT THEM.

THE SPAWNING OF THE HERRING\NIS A CRUCIAL EVENT

IN THE LIVES OF MANY ANIMALS\NALL ALONG THE COAST.

THE WHOLE EVENT COINCIDES\NWITH THE PLANKTON BLOOM,

AND WITHIN THREE SHORT WEEKS,\NIT'S ALL OVER.

THE MIGRATORY BIRDS LEAVE\NTO CONTINUE THEIR JOURNEY NORTH.

THEY WILL NOT COME BACK

UNTIL THE HERRING ALSO RETURN\NNEXT YEAR.

Attenborough: GRAY WHALES.

THEY HAVE FOLLOWED THE SUN\NNORTH,

AND THEY TOO ARE SEEKING\NTHE FOOD

THAT IS GENERATED BY THE BLOOM\NOF THE PHYTOPLANKTON.

KRILL ARE FEEDING OFF IT,

AND THESE WHALES ARE FEEDING\NON THE KRILL,

SKIMMING IT FROM THE SURFACE\NWITH THE FILTER PLATES OF BALEEN

THAT HANG FROM THEIR UPPER JAWS.

GRAY WHALES MAKE\NONE OF THE LONGEST MIGRATIONS

UNDERTAKEN BY ANY\NMARINE MAMMAL --

A ROUND TRIP\NOF 12,000 MILES OR SO

FROM THEIR BREEDING GROUNDS\NOFF MEXICO

ALONG THE ENTIRE COAST\NOF NORTH AMERICA

RIGHT UP TO THE ARCTIC OCEAN.

THEY TRAVEL CLOSE TO THE COAST,

WITH THE MALES AND NON-BREEDING\NFEMALES LEADING THE WAY.

THE LAST TO START ARE THE COWS\NTHAT HAVE JUST GIVEN BIRTH.

THEY HAVE TO WAIT\NUNTIL THEIR NEWBORN CALVES

ARE SUFFICIENTLY BIG AND STRONG

TO TACKLE\NSUCH AN IMMENSE JOURNEY.

THEIR PROGRESS\NIS NECESSARILY SLOW.

THE MOTHERS MUST STAY\NALONGSIDE THEIR YOUNG,

AND EVEN A STRONG CALF CAN ONLY\NTRAVEL AT A COUPLE OF KNOTS.

THEY STICK EVEN CLOSER\NTO THE SHORE,

OFTEN WITHIN JUST 200 METERS.

KILLER WHALES.

THEY HAVE LEARNT\NTHAT GRAY WHALES

FOLLOW TRADITIONAL ROUTES.

THE KILLERS HAVE NO TROUBLE

IN OVERTAKING A CALF\NAND ITS DEVOTED MOTHER.

NORMALLY, THEY CONTINUALLY CALL\NTO ONE ANOTHER,

BUT NOW THEY HAVE FALLEN SILENT.

THE MOTHER GRAY WHALE\NAND HER CALF

HAVE NO IDEA\NTHAT THEY'VE BEEN TARGETED.

CATCHING UP WITH THE GRAY WHALES

IS THE EASY PART\NFOR THE KILLERS.

THEY HAVE TO BE CAUTIOUS,

FOR THEY ARE ONLY\NABOUT HALF THE SIZE

OF THE GRAY WHALE MOTHER.

SHE CAN INFLICT REAL DAMAGE\NWITH HER TAIL.

BUT THE KILLERS\NARE NOT AFTER HER.

THEY'RE AFTER HER CALF.

AS LONG AS THE MOTHER CAN KEEP\NIT ON THE MOVE, IT WILL BE SAFE,

AND SHE DOES HER BEST\NTO HURRY IT ALONG.

AT FIRST, THE KILLERS AVOID\NGETTING TOO CLOSE TO THE MOTHER

BUT JUST KEEP PACE ALONGSIDE.

THEY KNOW THAT THE CALF,\NGOING AT THIS SPEED,

WILL EVENTUALLY TIRE.

AFTER THREE HOURS\NOF BEING HARRIED IN THIS WAY,

THE CALF BECOMES TOO EXHAUSTED\NTO SWIM ANY FURTHER.

THE MOTHER HAS TO STOP.

THIS IS THE MOMENT THE KILLERS\NHAVE BEEN WAITING FOR.

THEY START TO TRY AND FORCE\NTHEMSELVES

BETWEEN MOTHER AND CALF.

A CALF SEPARATED FROM ITS MOTHER

WILL NOT BE ABLE\NTO DEFEND ITSELF.

TIME AND AGAIN,\NTHE BLACK FINS OF THE KILLERS

APPEAR BETWEEN THE MOTTLED BACKS\NOF THE GRAY WHALES.

AT LAST THE KILLERS SUCCEED,

AND NOW THAT THEY'VE GOT\NTHE CALF ON ITS OWN,

THEY CHANGE THEIR TACTICS.

THEY LEAP RIGHT ONTO THE CALF

AND TRY TO PUSH IT UNDER.

NOW, THE WHOLE POD IS INVOLVED.

ONE OF THEM TAKES A BITE.

SOON, THE SEA IS REDDENED\NWITH THE CALF'S BLOOD,

AND THE KILLERS CLOSE IN\NFOR THE FINAL ACT.

THE CALF IS DEAD.

AFTER A SIX-HOUR HUNT,

THE KILLER WHALES\NHAVE FINALLY WON THEIR PRIZE.

THE MOTHER, BEREFT,

HAS TO CONTINUE HER MIGRATION\NNORTH ON HER OWN.

SHE LEAVES BEHIND\NTHE CARCASS OF A CALF

THAT SHE CHERISHED FOR 13 MONTHS\NIN HER WOMB,

FOR WHICH SHE DELAYED\NHER OWN JOURNEY TO FIND FOOD.

Attenborough: OVER A MILE DOWN,

IN THE TOTAL\NDARKNESS OF THE DEEP OCEAN,

THE BODY OF ANOTHER GRAY WHALE,\NA 30-TON ADULT.

IT SETTLED HERE\NONLY A FEW WEEKS AGO.

ALREADY, IT HAS ATTRACTED\NHUNDREDS OF HAGFISH.

THESE SCAVENGERS,\NOVER HALF A METER LONG

AND AS THICK AS YOUR ARM,\NARE ONLY FOUND IN THE DEEP SEA.

THEY HAVE BEEN ATTRACTED\NBY THE FAINT WHIFF OF DECAY

SUFFUSING THROUGH THE WATER\NFOR MILES AROUND.

WITH THEIR HEADS BURIED\NIN THE WHALE'S FLESH,

THEY BREATHE THROUGH\NGILL OPENINGS

ALONG THE SIDES OF THEIR BODIES.

THEY'RE VERY\NPRIMITIVE CREATURES --

NOT EVEN TRUE FISH,\NFOR THEY LACK JAWS.

THEY FEED, NOT BY BITING,

BUT BY RASPING OFF FLESH\NWITH TWO ROWS OF HORNY TEETH.

IN JUST A FEW HOURS,\NA HAGFISH CAN EAT

SEVERAL TIMES ITS OWN WEIGHT

OF ROTTING FLESH.

NEXT TO ARRIVE,\NA SLEEPER SHARK.

IT MOVES SO SLOWLY\NTO CONSERVE ENERGY --

AN IMPORTANT STRATEGY\NFOR SO LARGE AN ANIMAL

SURVIVING IN SUCH\NA POOR HABITAT.

SLEEPER SHARKS LIVE\NOVER A MILE DOWN

AND GROW\NTO OVER SEVEN METERS LONG.

THEY CAN GO FOR MONTHS\NWITHOUT FOOD,

SLOWLY CRUISING\NALONG THE BOTTOM,

WAITING FOR RARE BONANZAS\NSUCH AS THIS ONE

TO ARRIVE FROM ABOVE.

A WHOLE RANGE OF DIFFERENT\NDEEP-SEA SCAVENGERS

WILL FEAST ON THIS CARCASS\NFOR A LONG TIME

BEFORE ALL ITS NUTRIMENT\NHAS BEEN CONSUMED.

18 MONTHS LATER,

ALL THAT IS LEFT IS A PERFECT\NSKELETON STRIPPED BARE.

THE SUN'S ENERGY,\NTHAT WAS CAPTURED

AND TURNED INTO LIVING TISSUE\NBY THE FLOATING PHYTOPLANKTON,

HAS BEEN TRANSFERRED\NFROM ONE LINK TO ANOTHER

IN THE FOOD CHAIN\NAND HAS ENDED UP

AS FAR AWAY FROM THE SUN

AS IT IS POSSIBLE TO BE\NON THIS PLANET --

AT THE BOTTOM OF THE DEEP SEA.

BUT SOME ENERGY\NALSO RETURNS FROM THE DEEP.

MILLIONS OF OPALESCENT SQUID

ARE ON THEIR WAY\NTO THE SHALLOWS.

THEY'VE COME UP HERE TO MATE.

AS THE MALES GRAB THE FEMALES,\NTHEIR TENTACLES FLUSH RED.

FOR MOST OF THE YEAR,

THESE SQUID LIVE\NAT A DEPTH OF AROUND 500 METERS.

THEY ONLY COME TOGETHER

IN THESE GREAT BREEDING SCHOOLS\NFOR A FEW WEEKS.

JUST ONE SCHOOL WAS ESTIMATED\NTO CONTAIN ANIMALS

THAT WEIGH AROUND 4,000 TONS.

WAVE AFTER WAVE\NRISE FROM THE DEPTHS,

AND SOON THE SEABED\NIN THE SHALLOWS

IS STREWN WITH DENSE PATCHES\NOF EGG CAPSULES

SEVERAL METERS ACROSS.

AS EACH FEMALE ADDS ANOTHER\NCAPSULE TO THE PILE,

THE MALES FIGHT\NTO FERTILIZE ITS CONTENTS.

THE SQUID MAKE THEIR HUGE\NJOURNEY INTO THE SHALLOWS

BECAUSE THEIR EGGS WILL DEVELOP\NFASTER IN THE WARMER WATER HERE,

AND WHEN THE YOUNG EMERGE,

THEY WILL FIND MORE FOOD\NMORE EASILY

THAN THEY WOULD\NIN THE OCEAN DEPTHS.

DAWN THE NEXT MORNING,

AND THE SEABED FOR MILES AROUND\NIS COVERED IN EGG CAPSULES.

THE SQUID THEMSELVES\NHAVE ALL GONE.

MANY WILL HAVE DIED,

BUT SOME WILL HAVE RETURNED\NTO THEIR HOME IN THE DEEP.

THEY WILL NOT RETURN\NTO THE LIGHT OF THE SUN

UNTIL THE NEXT TIME THEY ARE\NDRIVEN UP BY THE URGE TO SPAWN.