01x03 - Freshwater

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

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

Tyrannosaurus rex.

An animal to spark the imagination
for all of us.

What kind of an animal was it?

What did it look like? How did it live?

Now, scientific research has answered
such questions.

And not just about T. Rex,

but the other species
that lived alongside it.

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

Planet Earth, 66 million years ago.

The skies are filled with flying giants.

In the seas,
monstrous reptiles patrol the depths.

And on land, dinosaurs of every kind,

all facing the struggle to survive.

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

This is their story.

For millions of years,
the lands of planet Earth

have been carved by water.

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

Such places are the home
of flying reptiles.

Pterosaurs.

Their wings of skin stretch
from finger to ankle.

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

Each evening,

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

There is safety in numbers.

And anyway,
few land-living hunters venture here.

But one does.

A type of dinosaur. Velociraptor.

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

They are, however, exceptionally agile.

And just as well.

One false step here could bring disaster.

The pterosaurs are skittish.

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

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

Lightweight bodies
and feathered arms help them

to control their descent.

And their broad tails assist them
in keeping their balance.

Those pterosaurs
that are resting on the margins

of the colony will be the easiest targets.

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

The female goes high.

The two males stay low.

A few pterosaurs are almost
within striking distance.

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

In the chaos,
her victim slips from the ledge.

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

And, in the end, she gets her meal.

The males are left to face the pterosaurs.

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

Global temperatures are high.

There are violent storms
and torrential rains.

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

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

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

Tyrannosaurus rex.

This old male has just brought down
a Triceratops.

But in doing so, he's been injured.

T. Rex are built
for hunting large herbivores…

Though many of those have evolved
heavy defensive weapons.

Decades of battling armored prey
has scarred his body.

One battle even cost him
the tip of his tail.

These new injuries are more serious.

At his great age,
infection is a real risk.

River water could help
to clean his wounds.

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

But that day could come sooner
than expected.

Another T. Rex.

A stranger.

But this newcomer has a different smell.

It's a female.

She's younger and smaller.

But nonetheless,
she might also be a rival.

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

He would prefer to mate.

She seems to approve.

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

and they nuzzle.

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

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

So, they stay together.

And in the coming weeks,
they mate frequently.

Eventually, she'll lay up to 15 eggs.

And with them comes the promise
of the next generation.

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

In parts of central Asia,

heavy seasonal rains
fill the rivers until, eventually,

they overflow their banks.

The surrounding plains are flooded.

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

Deinocheirus.

It's even taller than T. Rex.

And its massive duck-bill snout
is very effective

in gathering water plants.

This male feeds voraciously,

having eaten very little
during the long dry season.

Water plants are rich in nutrients.

And his huge, curved claws,
eight inches long,

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

He himself is a source of food
for smaller creatures.

Bloodsucking flies, which infest his coat.

They're irritating and even painful.

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

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

To get to them, he needs assistance.

A dead tree. That could be the answer.

That's much better.

And now he can get back to feeding.

But a diet that consists almost entirely
of wet vegetation

does have one inevitable consequence.

What was food for one becomes fertilizer
for many others.

And a giant as big
as Deinocheirus can produce

over 20 tons of dung every year.

Southern Africa.

Here, too, the annual rains create floods.

And the land
turns into a maze of narrow channels

running between countless small islands.

This is now a swamp forest.

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

on planet Earth.

A giant pterosaur. Quetzalcoatlus.

This is a female.

Her wings are over 30 feet across.

And she's come here
for one particular reason.

The small islands
created by the rising waters

are just the place
for her to lay her eggs.

Quetzalcoatlus are certainly masters
of flight.

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

Each wing is supported by the single
greatly elongated bone

of her fourth finger.

By turning her wings upwards,

she can walk very effectively
on all fours.

She's come here to make a nest.

She chooses to do so on damp, swampy soil

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

These first two are just the start.

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

And add two more eggs every few days.

Producing eggs takes a lot
of effort and energy.

Each one is huge, weighing around a kilo.

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

She covers them with vegetation
to conceal them.

Now, she needs to eat.

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

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

She must leave to hunt for prey elsewhere…

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

while she's away.

Another, much older Quetzalcoatlus female.

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

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

But there is a way to solve that problem.

And eggs, after all, are very nutritious.

The owner of the nest is back.

The older female is driven off.

But the younger female's nest is wrecked.

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

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

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

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

As river water flows downstream,

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

The finer sediments may be transported
for hundreds of miles,

but as the river broadens, it slows.

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

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

Crabs.

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

This is Masiakasaurus.

A female, six feet long.

And she has a mouthful
of needle-sharp teeth.

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

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

Too good an opportunity to miss.

And not only for her.

She has three young.

Only four inches tall.

And not quite ready
to take on large crabs.

They still rely
on their mother's leftovers.

But some youngsters
develop hunting instincts early.

Very tempting.

The smallest crabs can be swallowed whole.

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

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

Beelzebufo, the devil toad.

One of the largest frogs
that has ever existed.

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

These sandbars may be
a rich feeding ground,

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

The river water
is now approaching the sea.

A taste of salt
in its waters is already detectable.

At high tide,

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

Elasmosaurs.

These are true oceangoing reptiles.

But some come to estuaries
to explore the brackish waters.

Now, the millions of tons
of sediment carried here

by rivers is finally delivered
into the sea.

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

the two waters flow side by side.

Nonetheless,

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

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

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

to pursue their prey.

There is no escape for the fish…

Even above the water.

These Elasmosaurs
collect the last of the river's gifts

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

Next on Prehistoric Planet,

the bond between mother and young
is tested to the limit

as they struggle to survive.

Ancient foes battle each other
and freezing blizzards.

And feathered dinosaurs
rule the ice worlds.

To discover the science
behind the stories,

go now to the Prehistoric Planet
show page.