Green Seas Blue Planet II


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WIND HOWLS

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ICE CREAKS AND GROANS

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In the far north,

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after three dark months of winter...

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..a world is waiting...

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..for a trigger.

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The sunshine of spring.

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Starfish are the first to respond.

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They race for the highest point...

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..and sensing changes in the water,

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with the tips of their tube feet...

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..they spawn.

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Sea cucumbers,

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with only their mouths exposed,

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now emerge.

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They collect as many starfish eggs as they can.

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Which is quite a lot, when you've got ten arms.

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Now sea pens rise up to claim a share.

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The creatures here must grab what they can of this annual banquet.

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For the light has also set in motion the greatest transformation of all.

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Fronds of kelp, a marine alga,

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rise towards the surface,

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lifted by their gas-filled bladders.

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Soon, a marine forest has materialised...

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..teeming with life of all kinds.

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These green seas are some of the most productive,

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but fiercely competitive, waters

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in all the oceans.

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The southern tip of Africa.

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Here, two great oceans collide.

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SEA ROARS

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In the shallows, fed by rich currents,

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are bountiful forests of kelp.

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Barely visible except for the pulsating siphon

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through which it breathes, a common octopus,

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waiting for prey to pass by.

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A crab will do.

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The octopus sets off in pursuit.

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And then lurks...

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..with the patience of an ambush hunter.

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But the octopus shares the Cape waters

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with a great concentration of other predators.

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Fur seals...

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..and sharks.

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They all eat octopus...

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..if they can find one.

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And pyjama sharks are experts...

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..at hunting in the undergrowth.

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Time to disappear.

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But these tough-skinned little sharks

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are small enough to reach deep into crevices.

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But the octopus is far from finished.

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She slips her tentacles into the shark's gills.

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That prevents the shark from breathing.

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So, the shark has to let go.

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When caught out in the open, and vulnerable,

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this octopus does something truly extraordinary...

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..and never recorded before.

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She disguises herself...

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..with a protective armour of shells.

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She's hiding...in plain sight.

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The shark can sense its prey...

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..but the shells confuse it.

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In a forest full of hungry mouths,

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superior wits allow this octopus to stay alive.

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Forests of kelp flourish in seasonal waters around the globe...

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..particularly along the Pacific Coast of North America.

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Here, the biggest kelps of all

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grow in vast forests,

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stretching for hundreds of miles.

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In some places, the giant fronds

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rise up to 60 metres tall.

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The thickets they create are crowded with life.

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Competition here, for space and food, is intense.

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A challenging problem for the Garibaldi fish.

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He tends to his patch of seaweed,

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filled with tiny creatures that he eats.

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As with most farmers, his work never ends.

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He removes snails and any other grazers

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that come to eat his algae...

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..no matter how big they are.

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He has to deal with pests of all kinds.

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This can be the worst of them -

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sea urchins that can scrape off every vestige of algae from a rock.

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Its spines are needle-sharp.

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Somehow, the Garibaldi must remove it.

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But the problem with sea urchins...

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..is that they just keep coming.

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When evening arrives and the light fades, he has to stop.

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He not only needs a rest, he needs to hide.

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Because at night, predators prowl through these forests.

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A torpedo ray,

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capable of stunning its victim with 45 volts of electricity.

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While the Garibaldi hides...

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..the urchins can feed without interruption.

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The light returns...

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..and he finds his farm is once again under attack.

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Urchins, like locusts,

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have the ability to swarm.

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And this can be disastrous, not just for the Garibaldi,

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but for the kelp forest itself.

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All the vegetation is now under attack.

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The urchins move through the forest,

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cutting through the kelp fronds

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and leaving behind vast barrens.

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These urchin armies have felled many kelp forests

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along the Pacific Coast of North America.

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But help is at hand.

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Sea otters.

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All other kinds of otters spend much of their lives on land,

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but sea otters rarely leave the water.

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At first, a newly-born pup is not a very good swimmer,

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so its mother spends hours grooming its fur to make it buoyant.

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But to provide her youngster with milk and keep herself warm,

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she must eat up to 30% of her body weight every day.

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She does that by eating shellfish.

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And urchins are among a sea otter's favourite delicacies.

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In the past, sea otters were hunted so intensively for their fur

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that they came close to extinction.

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With them gone, many kelp forests were replaced with urchin barrens.

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Today, sea otters are protected...

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..and as their numbers slowly return,

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many of the kelp forests are recovering, too.

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Now, in some remote places,

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sea otters are so numerous

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they assemble in huge rafts...

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..something that hasn't been seen for over a century.

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In the sun-drenched shallows off Australia...

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..kelp is replaced by the sea's only flowering plants,

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sea grass.

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The most extensive of these marine grasslands

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can stretch for over 3,000 square miles.

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All across the tropics, they're patrolled by tiger sharks.

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They can grow up to five metres in length...

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..and have powerful crushing jaws.

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Green turtles are their prey.

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The turtles feed almost entirely on sea grass.

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A single one can consume up to two kilos of it in a day.

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But they can never rest easy.

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Healthy turtles will keep well away from an approaching shark.

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And just by keeping the turtles on the move,

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the sharks prevent any one patch of sea grass from being overgrazed.

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And that has benefits for us all.

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A patch of sea grass can absorb and store

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35 times as much carbon dioxide

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as the same area of a rainforest.

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So, the prairies and their sharks are surprising allies

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in the fight against a warming climate.

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The struggle to survive in our green seas

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can have far-reaching consequences.

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Once a year, one particular meadow in Australia is transformed.

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Around the first full moon of winter,

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an army materialises.

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Spider crabs.

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For the past year, they've been feeding in deeper waters.

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Now they march across the sea-grass plains.

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Hundreds of thousands of them.

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They clamber over one another...

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..creating great mounds...

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..nearly 100 metres long...

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They're not seeking mates, neither are they laying eggs.

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They have come here in order...

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to grow.

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Like all crabs,

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their bodies are enclosed

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in a hard, un-expandable shell.

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So, to grow, they have to break out of it...

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..and that allows the soft one that has developed beneath to expand.

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It will take days for the new shell to harden.

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Its legs are so limp that they won't work properly.

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The crab is unprotected and in great danger.

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A smooth stingray.

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It's huge - about four metres long.

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It wants a soft, freshly-moulted crab

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that will be easier to eat.

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The crabs try to stick together.

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But now, disturbed by the ray,

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they're scattering.

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A newly-moulted crab

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is too weak to keep up with the crowd.

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GRINDING

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The safest place is right in the middle of the pile.

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That is why they have all assembled here.

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There is safety in numbers.

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The vast majority of the crabs escape...

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..and within the next few days,

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they will be ready to return to the depths

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and resume their lonely wanderings in search of food.

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This is no graveyard...

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..but the triumph of a 100,000 crabs successfully moulted.

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The green seas of Southern Australia

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are particularly rich in such spectacular assemblies...

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..but most of the creatures come together

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for a very different reason.

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To breed.

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The giant cuttlefish,

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the largest of all cuttlefish.

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They live for just one or two years.

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Now, as the Australian summer draws to an end,

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they have one last act to complete.

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To find a mate.

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But there are over 100,000 males,

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competing for the arriving females in this one bay.

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Among them a giant - a true Goliath.

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He probably weighs about ten kilos.

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Bands of colour sweep across his skin.

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That's how cuttlefish communicate.

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This smaller male couldn't possibly take him on.

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Beside Goliath, and under his protection,

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a female who has just mated with him.

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But other rivals are still interested.

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It seems a small male wouldn't stand a chance.

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The female is now displaying a white stripe

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along her side nearest Goliath.

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It's a clear signal that she no longer wants to mate with him.

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It's all the encouragement that the little male needs.

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He's going to have to use trickery.

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He tones down his colours

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and tucks in his arms.

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He's just the right size to mimic a female.

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Goliath is deceived.

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The small male now displays a white stripe,

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just like the real female, to deter his advances.

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He slips beside her...

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..and they mate.

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By mating with multiple partners...

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..the female ensures the greatest genetic diversity for her young.

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The sneaky male leaves,

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his final act complete.

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So, even among giant cuttlefish, it seems...

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..it's not all about size.

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Other males in these Australian green pastures,

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take greater responsibility for their young.

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A weedy sea dragon.

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This is a male and he's carrying a precious cargo.

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While mating with the female,

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he collected the eggs and attached them to his underside.

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Now, he's leaving these seaweed thickets...

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..and travelling into more open waters

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where elaborate camouflage is less effective.

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And there are many predators out here.

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And this is what the fathers risk their lives for.

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Dense clouds of minute shrimp.

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Mysids, one of a sea dragon's favourite foods.

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They're drawing other sea dragons out here, too.

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Finally, it's time for the young to break free.

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But algae has grown over these developing eggs...

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..and it risks smothering them.

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Nonetheless, the babies are emerging.

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They've hatched successfully.

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The fathers return to the tangle of kelp,

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where they're virtually invisible...

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..while the young remain out here.

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But they will grow quickly,

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surrounded as they are by their ideal food.

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Vast numbers of the oceans' young fish

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start their lives in the green seas.

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One of the richest nurseries of all are the mangrove forests.

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Fringing the coastline of the tropics,

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they form a natural protective barrier between land and sea...

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..and are some of the world's most productive forests.

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Below the water, their arching aerial roots

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give them a firm footing.

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Here, there's abundant food for baby fish.

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While the tangled roots protect them from bigger fish

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and other predators that haunt the channels.

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But in Northern Australia,

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with the receding tide...

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..the little fish are forced to leave their shelter.

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And now, they are vulnerable.

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It's the most deadly assassin in the green seas.

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The zebra mantis shrimp -

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a male, almost 40 centimetres long.

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But he's not hunting just for himself.

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He's collecting food for his mate.

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She may have been his partner for 20 years.

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She relies on him to bring her food...

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..and puts her energy into her eggs instead.

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In a world so full of food,

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this would seem a sensible strategy.

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But it's also a risky one.

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Were her male to disappear,

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she could starve.

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Something has caught this male's attention.

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Perhaps an irresistible odour...

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..or a distant call.

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Whatever the reason,

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a male will leave his burrow

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and his lifelong mate.

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An even larger hole.

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Females who have lost their mates

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appear to send out distress signals to call in a new male.

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A larger female will produce more eggs.

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So by mating with her, he will father more offspring.

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But infidelity comes at a price.

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A larger partner demands more food.

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The richer a sea, the greater the competition..

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..and there is one green sea

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that supports more life than all the rest combined.

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Unlike the mangrove forests and the sea-grass prairies,

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its location is in the open seas

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and only temporary and unpredictable.

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This greenness comes not from rooted plants...

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..but from clouds of floating ones.

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Billions of microscopic phytoplankton are proliferating.

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And in such numbers that they fuel one of the greatest feasts of all.

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Off America's Pacific Coast,

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hundreds of common dolphins are rushing to a banquet.

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HIGH-PITCHED CLICKING

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They're not the only ones homing in.

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So are sea lions.

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They're heading for Monterey Bay, California,

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where algal blooms have caused an explosion

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in plankton feeders.

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Anchovies - millions of them.

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The dolphins herd the anchovies towards the surface.

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Sea birds and sea lions take advantage of the shoal's appearance.

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It's a race to grab a share before others arrive.

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DEEP RUMBLING

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Humpback whales,

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hundreds of them.

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With every upward lunge,

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they sieve out up to 100 kilos of fish.

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They're claiming the biggest share

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of one of the biggest feasts on Earth.

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So crucial are these tiny plankton,

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that almost all marine life ultimately depends upon them.

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It's the green seas, not the blue...

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..that are the basis of almost all life in the world's oceans.

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To capture the magnificence of the undersea forests

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and the surprising creatures living here, the Blue Planet II team

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have developed a series of specialist camera rigs.

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From the mega-dome recording half-in-half-out shots

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at the top of the towering canopy...

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..to state-of-the-art time-lapse equipment

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that speeds up time to reveal the secret life of the forest floor.

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But, of all the creatures living in these forests,

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filming one in the waters off the Cape of South Africa

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was to prove the greatest challenge of all.

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Naturalist Craig Foster has developed a fascination

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for its most secretive resident, a common octopus.

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There are almost 100 species of shark in these waters,

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but that doesn't deter Craig,

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who's swum here every morning for the past six years.

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When you find that really small, tiny, little oval hole,

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then you know it's been killed by an octopus.

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And then if you look very, very carefully,

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they're often in the vicinity of that.

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Craig has witnessed the antics of these octopuses

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and wants to share his remarkable discoveries

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with Blue Planet cameraman Roger Horrocks.

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Roger is immediately charmed by the strength of their personalities.

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It's really been astounding to see how individual these characters are.

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The common octopus all display different behaviours.

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Some were extremely timid,

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some were very, very bold,

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they have variety and it's really endeared me to them.

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After weeks of filming different individuals,

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they finally meet one octopus

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that's not only seemingly unafraid of the camera,

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but willing to perform for it.

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She just came right up - whoop!

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And then came right through underneath the tripod

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in between my legs.

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Yeah, that's cool, amazing.

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She very quickly just completely accepted both of us.

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So, we've actually been getting these really intimate behaviours.

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It's amazing.

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I've watched this octopus for many months,

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it's just trusting us in the water,

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carrying on with normal activity which is just so fantastic.

0:53:440:53:47

Months later, the team finally film their star octopus on the hunt.

0:53:550:54:00

But then discover the grave consequences of sharing the forest

0:54:170:54:21

with so many other predators -

0:54:210:54:23

pyjama sharks.

0:54:230:54:25

Pound for pound, these sharks are far more brazen

0:54:260:54:29

and aggressive than a Great White.

0:54:290:54:31

They're like guided missiles.

0:54:310:54:33

The slightest smell that octopus gives off, that shark will find it.

0:54:330:54:38

The pyjama shark actually got hold of the octopus

0:54:430:54:45

and, I mean, I just assumed that was it.

0:54:450:54:48

After spending so much time with this animal,

0:54:510:54:54

it was just so difficult watching her get attacked.

0:54:540:54:57

Then, to their amazement, she fights back!

0:55:040:55:07

She put her tentacles down,

0:55:130:55:14

you can see them coming through the gill, basically,

0:55:140:55:17

closed the mouth. The shark couldn't breathe,

0:55:170:55:19

and that's what enabled her to escape.

0:55:190:55:21

And just witnessing that whole thing was,

0:55:210:55:24

you know, it was an incredibly intense moment.

0:55:240:55:27

The team are relieved by her escape.

0:55:290:55:32

But when caught out in the open,

0:55:440:55:47

her next trick astonishes them even more.

0:55:470:55:50

It lifted its arms and legs over its head,

0:55:530:55:56

and, at the same time, pulled the shell material with it

0:55:560:56:00

and created this extraordinary armoury.

0:56:000:56:03

Octopus had armoured up and then, when that guy came

0:56:050:56:08

through from the back, he could kind of smell something.

0:56:080:56:11

He's not seeing an octopus shape,

0:56:110:56:13

he's seeing that strange armoury.

0:56:130:56:16

Then he was bumping the octopus,

0:56:160:56:19

and it was just incredible to see how that octopus

0:56:190:56:22

outwitted that shark using the armour,

0:56:220:56:24

using all his, his knowledge,

0:56:240:56:26

it's just...absolutely phenomenal.

0:56:260:56:29

She's a rock star, man. A proper little rock star.

0:56:340:56:37

Thanks to Craig's and Roger's dedication,

0:56:380:56:41

the octopuses' astonishing behaviours are now known to science.

0:56:410:56:45

What else might we find as we continue to explore

0:56:480:56:51

these fascinating undersea forests?

0:56:510:56:55

Next time on Blue Planet II...

0:57:000:57:03

we meet the creatures that live where two worlds collide...

0:57:030:57:06

..and discover how they cope with the demands

0:57:090:57:11

of the ever-changing coasts.

0:57:110:57:14

To find out more about our oceans with this free poster,

0:57:240:57:27

call 0300 303 3520

0:57:270:57:32

or go to bbc.co.uk/blueplanet2

0:57:320:57:37

and follow the links to the Open University.

0:57:370:57:40

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