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Surely, one of the most remarkable animals
that has 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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For millions of years,
the lands of planet Earth

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have been carved by water.

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And the rivers that flow here
are still shaping these great canyons.

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Such places are the home
of flying reptiles.

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Pterosaurs.

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Their wings of skin stretch
from finger to ankle.

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And they can fly
for hundreds of miles in a day.

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Each evening,

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they come to this canyon in huge numbers
to roost on its narrow ledges.

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There is safety in numbers.

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And anyway,
few land-living hunters venture here.

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But one does.

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A type of dinosaur. Velociraptor.

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Their bodies are kept warm by feathers,
but they can't fly.

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They are, however, exceptionally agile.

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And just as well.

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One false step here could bring disaster.

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The pterosaurs are skittish.

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They will take to the air
at the first sign of danger.

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If the Velociraptors are to get a meal,
the element of surprise will be crucial.

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Lightweight bodies
and feathered arms help them

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to control their descent.

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And their broad tails assist them
in keeping their balance.

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Those pterosaurs
that are resting on the margins

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of the colony will be the easiest targets.

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The roar of the waterfall drowns the sound
of slipping rocks.

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The female goes high.

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The two males stay low.

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A few pterosaurs are almost
within striking distance.

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She has one,
but now the whole colony is alarmed.

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In the chaos,
her victim slips from the ledge.

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The female puts the effectiveness
of her feathered tail to the test.

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And, in the end, she gets her meal.

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The males are left to face the pterosaurs.

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The power of fresh water
is at work all around the planet.

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Global temperatures are high.

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There are violent storms
and torrential rains.

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Much of North America is covered
by thick, lush forest.

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Here live some of the most gigantic
plant-eaters that have ever existed.

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And they, in turn, are prey
for the most ferocious of hunters.

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Tyrannosaurus rex.

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This old male has just brought down
a Triceratops.

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But in doing so, he's been injured.

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T. rex are built
for hunting large herbivores…

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though many of those have evolved
heavy defensive weapons.

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Decades of battling armored prey
has scarred his body.

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One battle even cost him
the tip of his tail.

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These new injuries are more serious.

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At his great age,
infection is a real risk.

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River water could help
to clean his wounds.

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He stands a good chance of living
to fight another day.

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But that day could come sooner
than expected.

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Another T. rex.

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A stranger.

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But this newcomer has a different smell.

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It's a female.

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She's younger and smaller.

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But nonetheless,
she might also be a rival.

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He, however, makes it clear
that he's not interested in fighting.

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He would prefer to mate.

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She seems to approve.

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The facial area of a tyrannosaur
is very sensitive to touch,

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and they nuzzle.

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His great size and his battle scars
are evidence that he is a survivor.

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And that perhaps, in her eyes,
makes him an attractive partner.

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So, they stay together.

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And in the coming weeks,
they mate frequently.

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Eventually, she'll lay up to 15 eggs.

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And with them comes the promise
of the next generation.

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Habitats that depend on fresh water
can change rapidly and radically.

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In parts of central Asia,

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heavy seasonal rains
fill the rivers until, eventually,

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they overflow their banks.

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The surrounding plains are flooded.

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And through the water wades one
of the most bizarre of all dinosaurs.

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Deinocheirus.

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It's even taller than T. rex.

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And its massive duck-bill snout
is very effective

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in gathering water plants.

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This male feeds voraciously,

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having eaten very little
during the long dry season.

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Water plants are rich in nutrients.

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And his huge, curved claws,
eight inches long,

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enable him to dredge them up
from deep beneath the surface.

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He himself is a source of food
for smaller creatures.

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Bloodsucking flies, which infest his coat.

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They're irritating and even painful.

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And while his huge claws enable him
to have a good scratch…

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there are always some spots
that are just out of reach.

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To get to them, he needs assistance.

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A dead tree. That could be the answer.

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That's much better.

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And now he can get back to feeding.

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But a diet that consists almost entirely
of wet vegetation

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does have one inevitable consequence.

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What was food for one becomes fertilizer
for many others.

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And a giant as big
as Deinocheirus can produce

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over 20 tons of dung every year.

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Southern Africa.

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Here, too, the annual rains create floods.

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And the land
turns into a maze of narrow channels

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running between countless small islands.

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This is now a swamp forest.

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And it attracts one of the largest
flying animals that has ever lived

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on planet Earth.

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A giant pterosaur. Quetzalcoatlus.

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This is a female.

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Her wings are over 30 feet across.

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And she's come here
for one particular reason.

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The small islands
created by the rising waters

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are just the place
for her to lay her eggs.

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Quetzalcoatlus are certainly masters
of flight.

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But they're also, perhaps surprisingly,
very competent on the ground.

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Each wing is supported by the single
greatly elongated bone

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of her fourth finger.

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By turning her wings upwards,

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she can walk very effectively
on all fours.

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She's come here to make a nest.

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She chooses to do so on damp, swampy soil

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that will prevent her soft-shelled eggs
from drying out.

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These first two are just the start.

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For the next three weeks,
she will guard the open nest…

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and add two more eggs every few days.

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Producing eggs takes a lot
of effort and energy.

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Each one is huge, weighing around a kilo.

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Eventually, she produces a clutch
of a dozen or so.

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She covers them with vegetation
to conceal them.

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Now, she needs to eat.

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There should be enough food on this island
to sustain her youngsters when they hatch.

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But there's nothing substantial
enough here to satisfy her own hunger.

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She must leave to hunt for prey elsewhere…

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and trust that the isolation of her nest
will keep her unhatched young safe

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while she's away.

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Another, much older Quetzalcoatlus female.

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She, too, is looking for a safe place
to lay her eggs.

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And there may not be enough food here
for two sets of giant nestlings.

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But there is a way to solve that problem.

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And eggs, after all, are very nutritious.

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The owner of the nest is back.

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The older female is driven off.

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But the younger female's nest is wrecked.

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Out of the dozen eggs that she laid,
only three have survived.

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The success of her breeding season
now rests on these three fragile eggs.

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She will protect them as best she can
until they hatch in a few months' time.

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But after that, her young will have
to fend for themselves.

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As river water flows downstream,

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it scours out billions of tons of sand
and gravel and even shifts great boulders.

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The finer sediments may be transported
for hundreds of miles,

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but as the river broadens, it slows.

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And as a consequence,
it begins to drop some of its load.

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And animals whose ancestors lived
in the sea begin to appear.

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Crabs.

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In some places,
there may be dozens per square meter.

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This is Masiakasaurus.

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A female, six feet long.

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And she has a mouthful
of needle-sharp teeth.

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Just what you need
to deal with awkward, multi-legged prey.

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Crabs may have hard shells,
but they're full of protein.

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Too good an opportunity to miss.

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And not only for her.

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She has three young.

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Only four inches tall.

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And not quite ready
to take on large crabs.

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They still rely
on their mother's leftovers.

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But some youngsters
develop hunting instincts early.

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Very tempting.

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The smallest crabs can be swallowed whole.

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Unfortunately, what they lack in size,
they make up for in speed.

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It's best for the young
not to stray too far.

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Beelzebufo, the devil toad.

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One of the largest frogs
that has ever existed.

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He won't need to feed again for a month.

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These sandbars may be
a rich feeding ground,

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but there can be a high price
to pay for living here.

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The river water
is now approaching the sea.

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A taste of salt
in its waters is already detectable.

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At high tide,

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visitors come in from the open sea
to explore these channels.

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Elasmosaurs.

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These are true oceangoing reptiles.

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But some come to estuaries
to explore the brackish waters.

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Now, the millions of tons
of sediment carried here

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by rivers is finally delivered
into the sea.

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The river water takes time to mix
with the ocean, and, for a while,

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the two waters flow side by side.

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Nonetheless,

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great shoals of fish find plenty
on which to feed in these waters.

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The clouds of sediment conceal the fish,
if they're any distance away.

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But the Elasmosaurs don't hesitate
to swim into the murkiest of waters

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to pursue their prey.

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There is no escape for the fish…

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even above the water.

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These Elasmosaurs
collect the last of the river's gifts

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before its traces are finally lost
in the oceans of the prehistoric planet.

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Next on Prehistoric Planet,

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the bond between mother and young
is tested to the limit

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as they struggle to survive.

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00:37:40,802 --> 00:37:44,932
Ancient foes battle each other
and freezing blizzards.

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00:37:46,141 --> 00:37:49,978
And feathered dinosaurs
rule the ice worlds.

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To discover the science
behind the stories,

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00:37:53,732 --> 00:37:58,070
go now to the Prehistoric Planet
show page.