Introduction The Blue Planet


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Introduction

David Attenborough narrates a natural history of the oceans. We travel to the depths of the seas to reveal a spectacular variety of life, some never filmed before.


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Dwarfed by the vast expanse of the open ocean,

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the biggest animal that has ever lived on our planet.

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A blue whale, 30m long and weighing over 200 tonnes.

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It's far bigger than even the biggest dinosaur.

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Its tongue weighs as much as an elephant,

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its heart is the size of a car

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and some of its blood vessels are so wide you could swim down them.

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Its tail alone is the width of a small aircraft's wings.

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Its streamlining, close to perfection,

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enables it to cruise at 20 knots.

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It's one of the fastest animals in the sea.

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The ocean's largest inhabitant

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feeds almost exclusively on one of the smallest -

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krill, a crustacean just a few centimetres long.

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Gathered in a shoal, krill stain the sea red.

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A single blue whale in a day can consume 40 million of them.

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Despite the enormous size of blue whales

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we know very little about them.

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Their migration routes are still a mystery

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and we have no idea where they go to breed.

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They are a dramatic reminder of how much we still have to learn

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about the ocean and the creatures that live there.

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Our planet is a blue planet.

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Over 70% of it is covered by the sea.

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The Pacific Ocean alone covers half the globe.

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You can fly across it for 12 hours

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and still see nothing more than a speck of land.

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This series will reveal the complete natural history of our ocean planet,

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from its familiar shores to the mysteries of its deepest seas.

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THEY SHRIEK

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By volume, the ocean makes up 97% of the Earth's inhabitable space.

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Its marine life far exceeds that which inhabits the land.

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But life in the ocean is not evenly spread.

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It's regulated by the path of currents carrying nutrients

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and the varying power of the sun.

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In this first programme we'll see how these two forces interact

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to control life from the coral seas...

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..to the polar wastes.

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SEA LION ROARS

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The sheer physical power of the ocean dominates our planet.

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It profoundly influences the weather of all the world.

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Water vapour rising from it forms the clouds

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and generates the storms that ultimately will drench the land.

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The great waves that roar in towards the shores

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are dramatic demonstrations of its power.

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Waves originate far out at sea.

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There, even gentle breezes can cause ripples

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and ripples grow into swells.

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Out in the ocean, unimpeded by land, such swells can become gigantic.

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It's only when an ocean swell eventually reaches shallow water

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that it starts to break.

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As it approaches the coast,

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the bottom of the swell is slowed by contact with the sea bed.

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The top of the swell, still going fast, starts to roll over

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and so the wave breaks.

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The ocean never rests.

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Huge currents such as the Gulf Stream,

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keep its waters on the move all round the globe.

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These currents, more than any other factor,

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control the distribution of nutrients and life in the seas.

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A tiny island lost in the midst of the Pacific.

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It's the tip of a huge mountain that rises from the sea floor below.

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The nearest land is 300 miles away.

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Isolated sea mounts like this one create oases

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where life can flourish in the comparatively empty expanses of the open ocean.

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But the creatures that swim beside it would not be here were it not for one key factor -

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the deep ocean currents.

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Far below the surface,

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they collide with the island's flanks and are deflected upwards,

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bringing from the depths, a rich soup of nutrients.

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Such upwellings attract great concentrations of life.

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Most of the fish here are permanent residents feeding on the plankton,

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tiny plants and animals nourished by richness brought from the depths.

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They in turn attract visitors from the open ocean.

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Tuna.

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The plankton feeders are easy targets.

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All this action attracts even larger predators.

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Sharks.

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Hundreds of sharks.

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These silky sharks are normally ocean-going species,

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but the sea mounts in the eastern Pacific,

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like Cocos, Malpelo and the Galapagos,

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attract silkies in huge groups, up to 500 strong.

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Silkies specialise in taking injured fish

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and constantly circle sea mounts looking for the chance to do so.

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But silkies are not the only visitors.

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Hammerheads gather in some of the largest shark shoals to be found anywhere in the ocean.

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Sometimes thousands will circle over a single sea mount.

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But these sharks are not here for food.

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They have come for another reason.

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Some of the locals provide a cleaning service.

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Following the last El Nino year,

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when a rise in water temperatures caused many sharks to suffer from fungal infections,

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the number of hammerheads at the sea mounts reached record levels.

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Nutrients also well up to the surface along the coasts of the continents.

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This is Natal on South Africa's eastern seaboard.

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It's June, and just offshore

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strange, black patches have appeared.

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They look like immense oil slicks up to a mile long.

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But this is a living slick -

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millions of sardines on a marine migration

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that in sheer biomass rivals that of the wildebeest on the grasslands of Africa.

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Most of the time these fish live in the cold waters south of the Cape.

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But each year, the coastal currents reverse.

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The warm Agulhas current that flows from the north has been displaced

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by cold water from the south and has brought up rich nutrients.

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They in turn have created a bloom of plankton

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and the sardines are now feasting on it.

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As the sardines travel north, a caravan of predators follow them.

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Thousands of Cape gannets track the sardines.

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They nested off the Cape

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and timed their breeding so their chicks can join them in pursuing the shoals.

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Below water, hundreds of sharks have also joined the caravan.

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These are bronze whaler sharks,

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a cold-water species that normally lives much further south.

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These three-metre sharks cut such swathes through the sardine shoals

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that their tracks are clearly visible from the air.

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Harried by packs of predators and swept in by the action of the waves,

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the sardine shoals are penned close to the shore.

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Common dolphin are coming in from the open ocean to join the feast.

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There are over a thousand of them in this one school.

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When they catch up with the sardines, the action really begins.

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Working together, they drive the shoal towards the surface.

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It's easier for the dolphins to snatch fish up here.

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Now the sardines have no escape.

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Thanks to the dolphins, the sardines have come within the diving range of the gannets.

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Hundreds of white arrows shoot into the sea

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leaving long trails of bubbles behind each dive.

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Next to join the frenzy are the sharks.

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Sharks get very excited around dolphins,

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maybe because they can feed well,

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once the dolphins drive the sardines into more compact groups near the surface.

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As the frenzy continues, walls of bubbles drift upwards.

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They are being released by the dolphins, working together in teams.

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They use the bubbles to corral the sardines into ever tighter groups.

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The sardines seldom cross the wall of bubbles

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and crowd closer together.

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Bubble netting enables the dolphins to grab every last trapped sardine.

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Just when the feasting seems to be almost over, a Bryde's whale.

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The survivors head on northwards

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and the caravan of predators follows them.

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Nutrients can also be brought up, though less predictably, by rough weather.

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Particularly near the Poles, huge storms stir the depths

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and enrich the surface waters.

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And here in the south Atlantic, the seas are the roughest on the planet.

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And very rich seas they are too.

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The cold Falklands current from the south

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meets the warm Brazil current from the north.

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At their junction, there is food in abundance.

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These black-browed albatross are diving for krill that has been driven up to the surface.

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Like all albatross, black-brows are wanderers across the open ocean.

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A feeding assembly on this scale is a rare sight.

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Usually, the birds of the open sea are widely dispersed.

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But these feeding grounds are close to an albatross breeding colony,

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and a very special one.

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This is Steeple Jason, a remote island in the west of the Falklands.

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It has the largest albatross colony in the world.

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There are almost half a million albatross here,

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an astonishing demonstration of how fertile the ocean can be

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and how much food it can give even to creatures that don't live in it.

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LOUD CAWING OF BIRDS

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Not only nutrients generate these vast assemblies.

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The heat and light that the sun brings

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is essential for the growth of microscopic floating plants,

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the phytoplankton.

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And it's the phytoplankton that is the basis of all life in the ocean.

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Every evening, the disappearance of the sun below the horizon

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triggers the largest migration of life that takes place on our planet.

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1,000 million tonnes of sea creatures rise from the deep ocean

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to search for food near the surface.

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They graze on the phytoplankton under cover of darkness.

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Even so, they're far from safe.

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Other marine hunters follow them,

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some travelling up from hundreds of metres below.

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At dawn, the whole procession returns to the safety of the dark depths.

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The moon too has a great influence on life in the oceans.

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It's gravitational pull creates the advances and retreats of the tide.

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But the moon has more than a daily cycle.

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Each month it waxes and wanes as it travels round the Earth.

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This monthly cycle also triggers events in the ocean.

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The Pacific coast of Costa Rica, on a very special night.

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It's just after midnight and the tide is coming in.

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The moon is in its last quarter,

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exactly halfway between full and new.

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For weeks the beach has been empty, but that is about to change.

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At high tide, turtles start to emerge from the surf.

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At first they come in ones and twos.

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But within an hour, they are appearing all along the beach.

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They are all female Ridleys turtles

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and over the next six days or so, 400,000 will visit this one beach

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to lay their eggs in the sand.

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At the peak time, 5,000 are coming and going every hour.

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The top of the beach gets so crowded that they have to clamber over one another

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to find a bare patch where they can dig a nest hole.

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A quarter of the world's population of Ridleys turtles come to this one beach

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on a few key nights each year.

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The rest of the time, they're widely distributed, searching for food,

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most hundreds of miles from here.

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This mass nesting is called an arribada.

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How it's coordinated is a mystery

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but we do know that arribadas start

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when the moon is in its first or its last quarter.

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40 million eggs are laid in just a few days.

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By synchronising their nesting in this way,

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the females ensure that six weeks later their hatchlings will emerge in such enormous numbers

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that predators on the beach are overwhelmed and a significant number of baby turtles will survive.

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But why do the females use a cue from the moon to help them synchronise their nesting?

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Part of the answer to that becomes clear at dawn,

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on the following morning.

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The day shift of predators are arriving for their first meals.

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Vultures have learnt that the returning tide

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can wash freshly-laid eggs out of the sand.

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The risk of eggs being exposed by the surf

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may be part of the reason why turtle arribadas tend to occur

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around the last or first quarter of the moon.

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It's on days such as this, when the moon is neither full nor new,

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that the tides are weakest and the sea is likely to be calmer.

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So at these times it's easier for the female turtles

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to make their way through the surf

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and there's less chance of their eggs

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being washed out of the sand and being taken by the vultures.

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The moon's monthly cycle, and its influence on the tides,

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triggers many events in the ocean,

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from the spawning of the corals to the breeding cycles of fish.

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But an even longer rhythm has the most profound effect of all -

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the annual cycle of the sun.

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The sun's position relative to the Earth changes through the year

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and this produces the seasons.

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In the north, Spring comes as the sun rises higher in the sky.

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Off the coast of north-west America, the seas are transformed

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by the increasing strength of the sunshine.

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Here in Alaska, the coastal waters turn green

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with a sudden bloom of phytoplankton.

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Herring that have spent the winter far out to sea,

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time their return to the shallow waters

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to coincide with this bloom.

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Their vast numbers start one of the oceans' most productive food chains.

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Humpback whales are at the top of that food chain.

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They spent the winter breeding in warmer tropical waters off Hawaii.

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But there was little food for them there.

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This herring bonanza provides the majority of their food for the year.

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Stellar and Californian sea lions also return from the open ocean each year to feast off the herring.

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The herring themselves, however, have not come here for food.

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They are about to breed.

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Nothing deters them as they head for even shallower waters.

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Now the waters are so shallow that glaucous-winged gulls

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snatch live fish from the surface.

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In spite of these attacks and losses, the herrings swim on

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until they reach the vegetation the females need if they are to lay.

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Each female produces around 20,000 eggs.

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And they're very sticky.

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The males arrive soon after the females have spawned

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and release their sperm in vast milky clouds.

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Soon the excesses of the herrings' sexual spree

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creates a thick white scum on the surface.

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Through the season,

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curds of sperm clog the shores for hundreds of miles,

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from British Columbia in the south all the way to Alaska in the north.

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After a few days, this gigantic spawning ends

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and the herring head back out to deeper waters,

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leaving behind them fertilised eggs plastered on every rock and strand of vegetation.

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They time their spawning

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so that two weeks later, when these eggs start to hatch,

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the annual plankton bloom will have reached its height and the new-born fish fry will have plenty to eat.

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Meanwhile, all these eggs provide food for armies of animals

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both below and above the surface.

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Millions of birds arrive to collect a share of the herrings' bounty.

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Some of it is easily gathered, for millions of eggs have been washed up onto the shore.

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This encapsulated energy is particularly valuable to migrating birds.

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These surf birds are on the way to breeding grounds in the Arctic

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and they had to come down to refuel.

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Stranded herring eggs are just what they need.

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Bonaparte's gulls collect the eggs just below the surface of the water.

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Further out in the bay,

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huge flocks of ducks gather. They're mostly surf scoters -

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diving ducks that can feed off the bottom several metres down.

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There are such huge quantities of eggs,

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that even such a big animal as a bear finds it worthwhile to collect them.

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The spawning of the herring is a crucial event in the lives of many animals all along the coast.

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The whole event coincides with the plankton bloom

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and within three weeks it's all over.

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The migratory birds leave to continue their journey north.

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They will not come back until the herring also return next year.

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As the herring spawning finishes,

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other migrants are starting to arrive, just off shore.

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Grey whales.

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They have followed the sun north

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and they too are seeking the food generated by the bloom of the phytoplankton.

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Krill are feeding off it

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and these whales are feeding on the krill,

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skimming it from the surface with the filter plates of baleen

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that hang from their upper jaws.

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Grey whales make one of the longest migrations of any marine mammal -

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a round trip of 12,000 miles or so,

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from their breeding grounds off Mexico, along the entire coast of North America to the Arctic Ocean.

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They travel close to the coast, with the males and non-breeding females leading the way.

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The last to start are the cows that have just given birth.

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They have to wait until their new-born calves are sufficiently big and strong.

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Their progress is necessarily slow.

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The mothers must stay alongside their young and even a strong calf can only travel at two knots.

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They stick even closer to the shore,

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often within just 200 metres.

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Killer whales.

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They have learnt that grey whales follow traditional routes.

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The killers have no trouble in overtaking a calf and its mother.

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Normally, they continually call to one another

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but now they have fallen silent.

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The mother grey whale and her calf have no idea

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that they've been targeted.

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Catching up with the grey whales is the easy part for the killers.

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They have to be cautious for they are only half the size

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of the grey whale mother. She can inflict real damage with her tail.

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But the killers are not after her. They're after her calf.

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As long as the mother can keep it on the move, it will be safe.

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She does her best to hurry it along.

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At first, the killers avoid getting too close to the mother, but just keep pace alongside.

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They know that the calf, going at this speed, will eventually tire.

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After three hours of being harried in this way,

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the calf is too exhausted to swim further. The mother has to stop.

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This is the moment the killers have been waiting for.

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They try to force themselves between mother and calf.

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A calf separated from its mother will not be able to defend itself.

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Time and again, the black fins of the killers appear

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between the mottled backs of the grey whales.

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At last, the killers succeed,

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and now that they have the calf on its own, they change their tactics.

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They leap right onto the calf and try to push it under.

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They're trying to drown it.

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The calf snatches a desperate breath.

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The mother becomes increasingly agitated.

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Frantically she tries to push her calf back to the surface so that it can breathe.

0:39:470:39:53

But now it's so exhausted that it has to be supported by its mother's body.

0:39:550:40:02

The killers won't give up.

0:40:170:40:20

Like a pack of wolves, they take turns in harassing the whales.

0:40:200:40:25

Now the whole pod is involved.

0:40:430:40:47

One of them takes a bite.

0:40:570:41:00

Soon the sea is reddened with the calf's blood

0:41:110:41:16

and the killers close in for the final act.

0:41:160:41:19

The calf is dead.

0:41:390:41:43

After a six-hour hunt, the killer whales have finally won their prize.

0:41:460:41:51

The mother, bereft, has to continue her migration north on her own.

0:41:570:42:03

She leaves behind the carcass of a calf that she cherished

0:42:070:42:11

for 13 months in her womb, for which she delayed her own journey to find food.

0:42:110:42:17

The pod of 15 killer whales spent over six hours trying to kill this calf, but now, having succeeded,

0:42:200:42:27

they've eaten nothing more than its lower jaw and its tongue.

0:42:270:42:33

Valuable food like this will not go to waste in the ocean.

0:42:380:42:43

Before long, the carcass will sink to the very bottom of this deep sea.

0:42:430:42:49

But even there, its flesh will not be wasted.

0:42:490:42:52

Over a mile down, in the total darkness of the deep ocean,

0:42:550:42:59

the body of another grey whale, a 30-tonne adult.

0:42:590:43:04

It settled here only a few weeks ago.

0:43:040:43:07

Already it has attracted hundreds of hackfish.

0:43:070:43:12

These scavengers, over half a metre long and as thick as your arm,

0:43:170:43:22

are only found in the deep sea.

0:43:220:43:25

They have been attracted by the faint whiff of decay suffusing through the water for miles around.

0:43:250:43:31

With their heads buried in the whale's flesh,

0:43:340:43:38

they breathe through gill openings on their sides.

0:43:380:43:42

They're very primitive creatures,

0:43:420:43:44

not even true fish for they lack jaws.

0:43:440:43:48

They feed not by biting,

0:43:480:43:50

but by rasping off flesh with two rows of horny teeth.

0:43:500:43:55

In just a few hours, a hackfish can eat

0:43:550:43:59

several times its own weight of rotting flesh.

0:43:590:44:04

Next to arrive, a sleeper shark.

0:44:040:44:08

It moves so slowly to conserve energy -

0:44:130:44:18

an important strategy for so large an animal surviving in such a poor habitat.

0:44:180:44:24

Sleeper sharks live over a mile down

0:44:290:44:33

and grow to over seven metres long.

0:44:330:44:36

They can go for months without food, cruising along the bottom, waiting for rare bonanzas,

0:44:370:44:44

such as this one, to arrive from above.

0:44:440:44:48

A whole range of different deep-sea scavengers

0:44:530:44:59

will feast on this carcass for a long time, before all its nutriment has been consumed.

0:44:590:45:06

18 months later, all that is left is a perfect skeleton stripped bare.

0:45:060:45:11

The sun's energy that was captured and turned into living tissue by the phytoplankton

0:45:110:45:17

has been transferred from one link to another in the food chain

0:45:170:45:22

and ended up as far away from the sun as possible on this planet,

0:45:220:45:27

at the bottom of the deep sea.

0:45:270:45:30

But some energy also returns from the deep.

0:45:300:45:35

Millions of opalescent squid

0:45:390:45:42

are on their way to the shallows. They've come up here to mate.

0:45:420:45:47

As the males grab the females, their tentacles flush red.

0:45:470:45:52

For most of the year, these squid live at a depth of about 500 metres.

0:45:530:45:59

They only come together for a few weeks.

0:45:590:46:03

Just one school was estimated to contain animals that weigh around 4,000 tonnes.

0:46:030:46:10

Wave after wave rise from the depths,

0:46:190:46:23

and soon the sea-bed and shallows are strewn with dense patches of egg capsules several metres across.

0:46:230:46:30

As each female adds another capsule to the pile,

0:46:340:46:39

the males fight to fertilise its contents.

0:46:390:46:43

The squid make their huge journey into the shallows

0:46:560:47:01

because their eggs will develop faster in the warmer water here.

0:47:010:47:06

When the young emerge, they will find food more easily than they would in the ocean depths.

0:47:060:47:13

Dawn the next morning,

0:47:140:47:17

and the sea-bed for miles around is covered in egg capsules.

0:47:170:47:21

The squid themselves have all gone.

0:47:210:47:24

Many will have died but some have returned to their home in the deep.

0:47:240:47:29

They will not return to the light of the sun

0:47:290:47:33

until the next time they are driven up by the urge to spawn.

0:47:330:47:38

The enormous size of the oceans,

0:47:480:47:51

and the fact that we know so little about many of the creatures there,

0:47:510:47:54

have presented the film makers behind the Blue Planet series with difficult challenges.

0:47:540:48:00

None more so than the mighty blue whale.

0:48:000:48:02

Despite their massive size, blue whales have hardly ever been filmed.

0:48:020:48:07

And there are good reasons for that. They're among the fastest marine creatures. Faster than many boats.

0:48:070:48:15

Except for a few minutes to breathe, they stay submerged.

0:48:150:48:19

Even when they surface, they're timid and difficult to approach.

0:48:190:48:24

So, to capture blue whales on film is very difficult,

0:48:240:48:28

and it took the team many months and some ingenuity,

0:48:280:48:32

just to get these few rare images.

0:48:320:48:35

Just finding and keeping up with blue whales is a real challenge.

0:48:410:48:47

One of the largest blue whale populations migrates back and forth,

0:48:480:48:52

along the coast of California and Mexico each year.

0:48:520:48:56

For three seasons our camera teams were on standby,

0:48:560:49:00

waiting for passing whales.

0:49:000:49:02

In theory, a microlite is perfect for filming. It's inexpensive,

0:49:060:49:11

it doesn't disturb the whales and it's possible to land and dive in the water.

0:49:110:49:17

But as the migration continued south,

0:49:180:49:21

the whales were soon out of range and another strategy was called for.

0:49:210:49:27

We followed the whales south to Mexico and the Gulf of California.

0:49:280:49:32

On several consecutive years recently, blue whales have been regularly sighted here,

0:49:320:49:39

and the Gulf's calm waters seemed an ideal location for filming.

0:49:390:49:44

However, getting close enough to get film images wasn't going to be easy,

0:49:440:49:48

as experienced cameraman, Rick Rosenthal explains.

0:49:480:49:53

Filming whales around the world, I think that they are like either

0:49:530:49:58

a large aeroplane or... Very streamlined and it's difficult

0:49:580:50:02

to get an image. You're going to have to be very patient, if you're gonna get any behaviour whatsoever.

0:50:020:50:09

'Mary Lee, Mary Lee, Santa Emily, come back?'

0:50:090:50:13

The first problem was to find the whale

0:50:130:50:16

in 30,000 square miles of water.

0:50:160:50:19

OK, yes, you're just turning around the moon for us,

0:50:190:50:22

that's beautiful.

0:50:220:50:23

Using the locations of previous sightings, the team enlisted

0:50:230:50:28

the help of experienced pilot Sandy Lanham, who had a trained eye for spotting blue whales from the air.

0:50:280:50:35

I've been working with scientists for whale research for 10 years.

0:50:350:50:40

We're convinced that the only way to cover a body of water this large, is to use an aeroplane.

0:50:400:50:47

Without directions from the air,

0:50:500:50:52

the team would have found it far harder to catch up with the whales.

0:50:520:50:57

Once the boat had gained visual contact with the blue whale,

0:51:010:51:06

they aimed to get a good shot as it came up for air.

0:51:060:51:10

It was essential not to cause any disturbance.

0:51:100:51:14

The trick was to try and sneak ahead of the whale, predicting where it would surface next.

0:51:140:51:21

You need special permission and a good deal of experience to get this close to whales.

0:51:240:51:31

I dove down

0:51:330:51:34

and could see a white glowing body and turned the camera on

0:51:340:51:39

and the result was, you know,

0:51:390:51:42

a nice image of a huge blue whale

0:51:420:51:46

gliding by me like a giant torpedo.

0:51:460:51:49

Getting close to blue whales in a small boat

0:51:490:51:53

without causing disturbance

0:51:530:51:55

requires a good understanding of their behaviour.

0:51:550:51:57

You NEVER chase whales.

0:51:570:52:00

When they come up for air, their tails leave a smooth patch of water called a footprint.

0:52:020:52:08

These indicate its speed and direction.

0:52:080:52:11

If you're lucky, you can gauge where it will surface in about 15 minutes.

0:52:110:52:16

After countless attempts at this guessing game,

0:52:180:52:22

Rick was finally in the right place at the right time.

0:52:220:52:26

The whale was surfacing near the boat. At one time it came up close,

0:52:260:52:31

we were able to manoeuvre the boat quietly so we were on top of it,

0:52:310:52:37

looking down at it - enormous tail and the entire body stretched out,

0:52:370:52:43

maybe 50-60 feet long.

0:52:430:52:45

It's one of those Captain Ahab, Moby Dick tales

0:52:500:52:54

when you are looking down at the entire whale

0:52:540:52:57

and it was very quiet and not concerned about us.

0:52:570:53:01

It took some breaths and submerged and came up again

0:53:010:53:04

and we manoeuvred again and got in the same position.

0:53:040:53:07

We were looking down at the entire whale underneath us.

0:53:070:53:11

That's an extraordinary feeling for anybody.

0:53:110:53:13

Subtitles by Gabby De Gregorio and Nick Holmes - 2001

0:53:520:53:55

E-mail subtitling@bbc.co.uk.

0:53:550:53:58

Although 70 per cent of our planet is covered by water, the oceans and many of their inhabitants - such as the blue whale - remain an unexplored mystery. This edition travels to the very depths of the seas to reveal a spectacular variety of life - from alien monsters of the deep to pack-hunting killer whales attacking a grey whale calf.