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Surely one of the most remarkable animals
that had ever existed,

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and certainly one of the most famous,
is a dinosaur.

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Tyrannosaurus rex.

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An animal to spark the imagination
for all of us.

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What kind of an animal was it?

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What did it look like? How did it live?

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Now, scientific research has answered
such questions.

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And not just about T. rex,

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but the other species
that lived alongside it.

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And the latest imaging technology
enables us to bring them all to life.

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Planet Earth, 66 million years ago.

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The skies are filled with flying giants.

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In the seas,
monstrous reptiles patrol the depths.

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And on land, dinosaurs of every kind,

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all facing the struggle to survive.

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We now know so much about a world
that was ruled by the dinosaurs.

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This is their story.

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The southern shores
of the great inland sea

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that splits North America.

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And the tracks of the land's top predator.

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A Tyrannosaurus rex taking a swim.

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Hollow, air-filled bones
and powerful hind limbs

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make T. rex very effective swimmers.

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This is an adult male
with his young family.

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His offspring are now just old enough
to follow him on a journey

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to one of the many offshore islands
that fringe this coast.

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It's a short enough crossing,
but it can still be a dangerous one.

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A mosasaur.

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A giant marine lizard over twice the size
of a tyrannosaur

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and weighing over 15 tons.

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It's the largest predator on the planet.

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Turtles are normally on a mosasaur's menu.

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But this brood would make a welcome snack.

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An adult T. rex, even in water,

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could still defend itself
very effectively.

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But the young must stay close.

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Tyrannosaurus rex often lose
at least two-thirds

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of their original brood of 15 or so
in the first year.

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Now there are only four.

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The island offers safety
and the promise of food.

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Giant two-ton turtles are here to nest.

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But this is the one
that has drawn him here.

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It's dead, and the tyrannosaur
has smelled its rotting body.

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If he can just get to the underbelly,

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he will have over 2,000 pounds
of easy meat.

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T. rex has the most powerful jaws
in nature.

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And can bite
with the force of over five tons.

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The young are keen for a taste,
but he's not sharing it.

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It's time for them to learn
to hunt for themselves.

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The beach, however,
doesn't look very promising.

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But as the evening approaches,
things start to change.

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Baby turtles are beginning to hatch
from the sand and rush down to the sea.

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The young T. rex have been brought
to an ideal training ground.

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Hatchling turtles are the perfect size
for a novice to tackle.

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It pays for any hunter to be inquisitive.

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There's a lot to learn.

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And there's enough food here
to satisfy both parent and young.

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And if all else fails,

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you can always steal supper
from someone else.

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Across the globe,

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these shallow coastal seas cover an area
of 25 million square miles.

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Far more than even the largest continent.

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That, combined with the richness
of the waters,

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makes them very important habitat.

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Wherever land meets sea,

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nutrients rise from the deep,
fueling an abundance of life.

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It's especially rich here
in the North Atlantic,

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where huge shoals of fish
come close to the shore.

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One kind of animal thrives in such places
and forms immense colonies.

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Flying reptiles. Pterosaurs.

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Here, on the beaches of North Africa,
there are seven different species of them.

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They come here to feed, to rest,
and to raise their young.

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Tethydraco are well-adapted
to spend time on the ground

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and not only make their nests here
but stay to protect their brood.

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And their young certainly need protection.

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The dagger beak of Phosphatodraco.

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A nine-foot-tall predator
that stalks through these colonies,

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looking for a chance
to snatch an unguarded hatchling.

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But some types of pterosaurs
are less well-adapted to life on land.

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They have a slightly different
nesting strategy.

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They make their nests where they will
attract less attention from predators.

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Isolated cliffs like this are ideal.

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Pterosaur eggs are leathery
and can easily dry out,

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so they need to be covered.

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Beneath this pile of seaweed,
something is stirring.

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A tiny Alcione hatchling,
just a few inches high

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and weighing less than two ounces.

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Their mothers left the eggs here
about two months ago.

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Calling to each other
synchronizes hatching.

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There is safety in numbers.

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Their first instinct is to climb.

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Hatchlings from hundreds of nests
gather on the cliff-top

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to prepare for their first flight.

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But their wings are still unformed.

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The bones of the long finger
that supports their wing membrane

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must first straighten and lock together,
and that will take some hours.

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But they can't stay here for long.

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Their bones are extremely light,
up to 90% air,

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and that makes the effort needed
to take off much easier.

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Even so, test flights are essential.

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There will only be one chance
to get it right

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when the time comes to launch.

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The cliff edge creates updrafts,
and they can help.

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So, it pays to gather there
facing into the prevailing winds

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and towards the mainland.

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But no one seems quite ready
to take the plunge.

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Until, at last,
one youngster sets them all on their way.

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They're not heading for the beach
and its colony.

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They need to get to the mist forest
that lies beyond.

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Barbaridactylus.

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Powerful, predatory pterosaurs
that normally catch fish.

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But the hatchlings are too good to miss.

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One way to take evasive action is
to simply fold their wings and drop.

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But losing height will make it harder
for them to reach the forests.

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A crash landing in the colony.

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It's no place for a hatchling on its own.

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A lucky survivor
from the first wave of hatchlings…

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still heading in the right direction.

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Sanctuary.

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Of the hatchlings that left the stack,
few get as far as this.

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But for them,

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this forest offers all the shelter
and food that a young pterosaur needs.

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For the next five years,
this will be their home.

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Then, they will be large enough
to join the adults,

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catching fish out on the open ocean.

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Some marine animals that spend
all their lives fishing out at sea

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must occasionally visit the coast
for a very particular purpose.

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In the waters off the drowned continent
of Zealandia,

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a long journey is coming to an end.

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These are tuarangisaurs,

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a type of huge marine reptile
nearly 30 feet long.

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This female is accompanied by her calf,
about six months old.

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At most, she'll have only one youngster
every two years or so.

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It's a huge investment,

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and one that makes the bond
between mother and young very important.

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She has brought her young calf many miles
to this one bay.

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And they're not alone.

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Tuarangisaurs come here
from across the South Pacific.

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Males also gather here
to display to females.

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But for now, courtship is not
the female's first priority.

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This bay has something
that few others can provide.

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Pebbles that are particularly smooth,
hard, and rounded.

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They've been worn by the action
of river water, but they're hard to find.

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Here, however, in the pool
at the bottom of a waterfall,

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there are plenty of them.

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And the tuarangisaurs can take their pick.

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They then do something rather remarkable.

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They swallow them.

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They need the stones to act both
as ballast and as gizzard stones.

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Gastroliths which will remain
in their stomachs

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to grind up their unchewed food.

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For a youngster,

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learning to swallow pebbles
for the first time isn't easy.

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It takes a little practice.

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But it's also a chance for his mother
to find a suitable mate amongst the males.

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For the calf, at last, success.

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Now, he will swallow as many as he can.

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And, as he grows,
he'll return here for more.

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It's time for the family
to leave the coast

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and head back out to sea to feed.

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And for the young tuarangisaur,

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that is an important step
on the road to adulthood.

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In southern Europe,

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where the Atlantic meets
the great Tethys Sea,

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coastal life reaches
perhaps its greatest diversity.

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Rising sea level means that
there are countless submerged islands

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covered with sponges, clams and corals.

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Corals take advantage
of the sunshine in these shallows,

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forming partnerships with algae
that grow within their tissues.

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They collect tiny particles of food
floating in the ocean currents.

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Myriads of these marine creatures
encrust the solid rock.

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But one rock here
appears surprisingly bare.

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Beyond is a sheer drop-off
and the deep sea,

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home to oceanic predators…

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and danger for unwary reef fish.

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But this pycnodont fish
has little to fear.

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This is Hoffman's mosasaur,
the ocean's deadliest predator.

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But he's not here to eat.
He's come to be cleaned.

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Mosasaurs are giant lizards
and have both a lizard's forked tongue,

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and during the mating season,
a lizard's colorful skin.

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Now it's time to shed old skin.

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And when you need to look your best,

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nothing but an all-over body scrub
will do.

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Fish and shrimp pick scales
shed from his body.

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Resting at the surface allows
this sea-going, air-breathing lizard

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to fill his lungs,

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and relax.

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A rival.

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A younger male,
challenging for this territory.

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00:28:37,135 --> 00:28:40,680
The old male is heavier, over 15 tons.

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00:28:40,764 --> 00:28:43,183
But his rival is more nimble.

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00:28:56,655 --> 00:29:01,243
When they are as evenly matched as this,
these battles can be lethal.

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00:29:03,620 --> 00:29:07,499
Mosasaurs have been found
with the shattered teeth of rivals

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embedded in their skulls.

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00:29:16,508 --> 00:29:18,593
The old male snatches a breath.

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00:29:26,601 --> 00:29:28,937
Now he has the advantage.

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00:29:34,067 --> 00:29:37,487
By dragging his rival down,
he could drown him.

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00:30:24,326 --> 00:30:26,870
The old male has triumphed.

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00:30:27,704 --> 00:30:31,958
For now, at least,
this reef is still his territory.

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A crescent moon
off the coast of North America.

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The calm, dark nights that follow
trigger a rare and beautiful event.

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00:31:04,783 --> 00:31:08,828
Tonight, even in the deep, there is light.

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00:31:21,841 --> 00:31:25,887
Glowing ammonites rise from the abyss.

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00:31:34,813 --> 00:31:38,942
Ammonites are mollusks,
related to octopus and squid.

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00:31:39,651 --> 00:31:43,947
These scaphitids are no bigger
than a human hand.

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00:31:52,163 --> 00:31:55,917
For weeks, they've been gathering
in the coastal depths.

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00:32:02,382 --> 00:32:06,845
In the deep, these lights
may help lure plankton as food.

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00:32:07,554 --> 00:32:11,016
But tonight,
they serve a different purpose.

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00:32:13,643 --> 00:32:17,105
They've been drawn to the surface to mate.

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00:32:17,188 --> 00:32:21,151
And soon there are thousands
in each shoal.

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00:32:34,331 --> 00:32:39,753
Neighbor triggers neighbor,
creating waves of bioluminescence.

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00:32:49,095 --> 00:32:51,723
They have complex nervous systems,

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00:32:51,806 --> 00:32:55,268
controlling light-producing cells
called photocytes.

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00:33:04,236 --> 00:33:09,115
The males jostle for a place
around the larger females.

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00:33:10,659 --> 00:33:16,623
Clues from their displays tell her who is
the fittest and who is the best mate.

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00:33:21,503 --> 00:33:25,966
As couples entwine,
they coordinate their light displays.

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00:33:32,597 --> 00:33:37,060
If he can't match her precise rhythm,
he'll be rejected.

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But there is perfect synchrony.

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00:33:47,737 --> 00:33:51,992
This pair will now spawn
and help produce the next generation.

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After fertilization,

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the females enter the shallows
to release their eggs.

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As with most cephalopods,

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breeding is the final act
of their short lives.

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By morning, these lights
will have flickered and died.

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This magical night will be their last.

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00:34:54,596 --> 00:34:58,975
All over the globe,
the coast provides an ideal place

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for countless animals to mate,
raise their young, and to feed.

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00:35:11,988 --> 00:35:14,449
Back in the shallow waters of Zealandia,

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large groups of tuarangisaurs
have come together.

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They propel themselves with all four fins
and travel almost effortlessly

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to find the fish shoals
that gather here in summer.

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00:35:44,938 --> 00:35:47,857
Occasionally,
they break the surface to gulp air

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00:35:47,941 --> 00:35:51,278
before continuing
on their underwater flight.

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00:36:00,078 --> 00:36:04,457
But one female is not swimming
with her usual grace.

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00:36:05,709 --> 00:36:10,922
She and her two-year-old calf are lagging
behind the rest of the group.

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00:36:14,843 --> 00:36:17,679
She's moving rather laboriously.

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And that has not gone unnoticed.

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00:36:26,396 --> 00:36:30,025
A deadly hunter, Kaikaifilu.

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00:36:35,864 --> 00:36:39,993
The apparently stricken female
is a tempting target.

240
00:36:43,705 --> 00:36:47,375
Diving to deeper water
might make her less vulnerable.

241
00:36:53,215 --> 00:36:57,761
For the calf, trying to distract
the mosasaur is a dangerous game.

242
00:36:59,679 --> 00:37:01,848
But it's buying time.

243
00:37:07,312 --> 00:37:10,774
The mother and calf
are not entirely alone.

244
00:37:21,534 --> 00:37:23,995
These individuals may be related,

245
00:37:24,079 --> 00:37:28,667
and it's in all their interests
to drive Kaikaifilu away.

246
00:37:53,191 --> 00:37:57,737
This is the reason
for the female's apparent distress.

247
00:37:58,780 --> 00:38:00,323
She's pregnant.

248
00:38:24,890 --> 00:38:28,643
And now,
after a one-and-a-half year pregnancy,

249
00:38:29,519 --> 00:38:30,812
a baby.

250
00:38:36,902 --> 00:38:41,740
Over ten feet long,
nearly half the length of its mother.

251
00:38:42,407 --> 00:38:45,660
One of the biggest babies of all time.

252
00:38:53,710 --> 00:38:58,590
It needs to get to the surface
to take its very first breath.

253
00:39:19,819 --> 00:39:24,199
This young tuarangisaur could live
for 80 years.

254
00:39:26,243 --> 00:39:28,954
Now, supported by her family,

255
00:39:29,037 --> 00:39:32,040
she can take her place as a predator…

256
00:39:35,126 --> 00:39:38,004
in one of the richest habitats on Earth,

257
00:39:39,130 --> 00:39:44,052
the seas around the coasts
of our prehistoric planet.

258
00:39:59,276 --> 00:40:01,820
Next on Prehistoric Planet,

259
00:40:01,903 --> 00:40:07,284
giant dinosaurs wrestle to win a mate
in baking-hot deserts.

260
00:40:08,243 --> 00:40:09,661
And across the globe,

261
00:40:09,744 --> 00:40:14,583
remarkable specialists
must use every trick they can to survive

262
00:40:14,666 --> 00:40:17,878
in the most inhospitable places on Earth.

263
00:40:18,879 --> 00:40:21,923
To discover the science
behind the stories,

264
00:40:22,007 --> 00:40:26,469
go now
to the Prehistoric Planet show page.