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Somewhere on the edge
of a Jurassic forest,

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a mother dinosaur
is laying her eggs

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(Deep grunting)

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She is a 25-tonne Diplodocus

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Each football-sized object

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is carefully placed
in a deep trench

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Tenderly, she buries her clutch

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and then abandons them

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Out on the fern plains, the rest
of her gigantic herd grazes

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She is one of a family
of dinosaurs called the sauropods

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that dominate this period
in Earth's history

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They are the largest animals

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that will ever walk the planet

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This is the Jurassic period,

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and the giant continent of Pangaea

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that stretched from pole to pole
is now breaking up

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It is much wetter
than the earlier Triassic period

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and where there were once deserts,

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there are now vast forests
of conifer trees

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It is 70 million years since
dinosaurs first appeared on Earth

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and in this greener world,

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they have evolved into a myriad
of different forms

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Three months ago,
a mother Diplodocus laid 100 eggs

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in this clearing in the forest

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Now they are hatching,

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but there are signs they have been
discovered by an egg thief

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The culprit is an Ornitholestes
- a two-metre long carnivore,

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closely related to dinosaurs
that will evolve into birds

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Normally, he hunts small lizards
and mammals in the forest

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This is an extra treat

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(Squawks)

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Only 10 metres
away from the carnivore,

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the forest floor moves

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(Squeaks)

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(Squawks)

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Right under the predator's gaze,

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a baby Diplodocus, or sauropodlet,
has hatched

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Her brothers and sisters
are also struggling free

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from their buried eggs
beneath the surface

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And there is safety in numbers

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The Ornitholestes is too busy
eating to chase more sauropodlets

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He has had his fill

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A little female rests
for an instant

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and then,
along with the other survivors,

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heads for the deep forest
as fast as she can

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(Cheeping and squawking)

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Their mother laid them
at the edge of the forest

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because she was too big
to go deeper

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But the sauropodlets
need the cover of the deep forest

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For the next few months,
their only chance for survival

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is to remain hidden from predators
amongst the vegetation

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Between the trunks
of huge redwood trees,

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the forest floor is covered
in a dense layer of ferns

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Beneath these,

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the sauropodlets start their
lifelong obsession with eating

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Newly hatched,
they only weigh a few kilograms,

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but they must grow
by one tonne a year until adults -

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an astonishing 2-3kg a day

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(Distant roaring)

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However, the forest
is not a perfect sanctuary

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When faced with danger,
the sauropodlets lie very still

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and depend on their camouflage
for protection

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It may have worked this time,

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but very often, the sharp-eyed
predator gets his meal

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Not all of the landscape
is covered in forest

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There are vast open fern prairies,

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and this is where
the titans of the Jurassic roam

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Dinsoaurs like Stegosaurus,

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with its distinctive row
of spinal plates

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(Rumbling growl)

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These prairies
are kept clear of trees

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by the constant grazing
of such giant herbivores,

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and none have a larger impact
on this environment

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than the biggest dinosaurs of all-
the sauropods

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There are many different types

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of these gigantic,
long-necked creatures

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These are Diplodocus -
the longest of them all

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For protection,
they move in herds of 30 or more

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Some older ones
are over 40 metres long

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They use their very strong
but stiff necks

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to graze over large areas
with little effort

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To balance their necks,

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they have long tails
with whip-like ends,

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that are used for communication
between members of the herd

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Such a huge herd moving attracts
an array of smaller animals

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As they eat the vegetation,
insects swarm around them,

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and insect hunters,
like these damselflies,

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use the dinosaurs
as gigantic feeding platforms

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There is even a tiny flying reptile,
or pterosaur,

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called Anurognathus

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that specialises
in life amongst these giants

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These pterosaurs feed on insects,

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and spend their entire lives
hanging onto the Diplodocus

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They fight, feed and breed

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on creatures that are 150,000 times
heavier than they are

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Each Diplodocus drops over a tonne
of dung every day

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This attracts yet more insects

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especially the dung beetles

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Millions of years from now,
descendants of these beetles

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will clear elephant dung
off the African grasslands,

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but their peculiar lifestyle
started here

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in the Jurassic with the dinosaurs

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The herd of giants moves on,

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carrying its own unique habitat
with it

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After the rain, the redwoods steam
in tropical temperatures

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and a dinosaur's dawn chorus
fills the air

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(Bellows and screeches)

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A year has passed since the
sauropodlets fled into the forest,

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and deep in a canyon,
the little female grazes

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She is already over 3m long

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She feeds with other yearlings,

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sticking together
in a creche for safety

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They are here because
the canyon walls drip with moisture,

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creating a thick layer
of moss and fern

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But the canyon runs down
to the prairie

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and all this greenery
attracts larger dinosaurs

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A seven-tonne male Stegosaurus

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He too is a herbivore,
but very dangerous

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The large plates
are primarily there for display

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It's the metre-long spikes
on his tail that are lethal

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These he can wield
with devastating effect,

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despite having a very small brain
for his size

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The creche moves down the canyon,

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away from the Stegosaurus

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But two Allosaurus
have been drawn here -

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by the smell of prey

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(Low growling)

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(Squeaks)

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(Roaring)

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(Snarling)

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The Stegosaurus
flushes blood into his plates,

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creating a frightening
display of colour

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(Roars)

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Confused and intimidated
by the herbivore's display,

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the Allosaurus backs down

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Sauropodlets are small prey
for the Allosaurus

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These are the lions
of the Jurassic -

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the top predators of their age

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The creche once again seek
the sanctuary of the ferns,

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even though,
weighing half a tonne now,

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they are not as well hidden
as they used to be

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As they grow, their teeth
become more like the adults'

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These are perfect for stripping
ferns of their leaves

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Nearby, the vast skeleton
of a Diplodocus lies where it fell

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Such huge, weight-bearing bones

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are too large
for any forest creature to remove

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The female sauropodlet
can have little idea

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that in ten years,
she will be almost as large

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But the creche realise they are
too near the edge of the forest,

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and retreat into its green depths

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Elsewhere, an adult Diplodocus herd
is clearing forest

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This is how they have shaped
the landscape around them

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Vast areas of prairies
and open forests are kept that way

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because sauropods flatten trees
in search of food

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The Diplodocus are after the ferns
that grow between the trees

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Their teeth are more suited
to soft green leaves

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than woody branches

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One of the reasons
these creatures are so massive

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is because it allows them
to have a hugely long gut

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that can digest
the toughest Jurassic vegetation

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Whole leaves pass into their guts

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where stones
the dinosaurs have swallowed

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help grind their food down,

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so that bacteria ferment it
and release nutrients

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It is a process
that produces a lot of excess gas

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(Phwrrrrrt!)

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While the gut digests,

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the body is free to continue
its remorseless search for food

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(Squawking)

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In the forest,
an Anurognathus is hunting

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but not for insects

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He is looking for a host

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He finds it
in an immature Diplodocus

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This is the female sauropodlet
that hatched five years ago

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She is now 12 metres long
and weighs over 5 tonnes

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She has started to develop

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the spines and long whip tail
of adulthood

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Old predators in the forest
are no longer a threat

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Ornithalestes displays
his long quills

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in a futile gesture of aggression

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(Grating squawks)

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The Diplodocus have remained
in a creche,

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but they're getting too large
for the forest

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Food is short
and the trees restrict them

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Soon they must join
the adults on the plains

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There is more room
by the banks of a river

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that runs through the forest,

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but nature is about to take charge
of these dinosaurs' future

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Drifting through the trees
comes the scent of woodsmoke

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It is a smell that terrifies
every forest dinosaur

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There is a huge forest fire
to the south

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The Diplodocus flee,

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but to support their weight,

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they always need three legs
on the ground

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00:19:07,892 --> 00:19:12,523
So, despite the danger,
they can only manage to amble

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(Low howling)

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The blaze, however, moves faster

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00:19:21,332 --> 00:19:26,282
and that night,
a huge firestorm hits the area

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(Distant howling)

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00:19:33,452 --> 00:19:36,126
Above the sound of the blaze

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come the panicked cries
of trapped dinosaurs

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00:19:41,692 --> 00:19:45,527
These Jurassic fires are rare,
but can be devastating

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00:19:59,572 --> 00:20:04,442
Morning light reveals the bodies
of forest-dwelling dinosaurs

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00:20:04,532 --> 00:20:07,092
that have perished in the flames

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00:20:14,130 --> 00:20:17,285
Three members of the creche
have survived

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00:20:17,370 --> 00:20:21,000
They have been driven out
onto the prairies

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00:20:21,090 --> 00:20:23,559
This is exposed territory for them

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00:20:23,650 --> 00:20:28,008
They are not large enough to repel
an attack from an adult Allosaurus

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00:20:34,090 --> 00:20:39,085
To the young Diplodocus, the other
dinosaurs here are unfamiliar

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00:20:39,170 --> 00:20:42,049
and huge

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00:20:54,770 --> 00:20:59,640
This is Brachiosaurus -
a 13-metre high sauropod

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00:20:59,730 --> 00:21:04,088
that specialises in grazing
on the tree tops

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00:21:05,690 --> 00:21:09,730
His kind can effortlessly harvest
cones and fresh leaves

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00:21:09,810 --> 00:21:15,010
no other dinosaur can reach,
and they have grown enormous

215
00:21:15,090 --> 00:21:18,322
These adults weigh over 70 tonnes,

216
00:21:18,410 --> 00:21:23,007
making them the largest
land animals that have ever existed

217
00:21:23,090 --> 00:21:28,040
The juvenile Diplodocus do not have
the same size advantages

218
00:21:28,130 --> 00:21:32,966
and urgently need the protection
of an adult herd

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00:21:34,690 --> 00:21:37,728
(Wailing)

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00:21:39,930 --> 00:21:42,047
Across a conifer heathland

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00:21:42,130 --> 00:21:45,407
come the plaintive calls
of the young sauropods

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00:21:45,490 --> 00:21:49,689
It is a cry adult animals
are programmed to react to

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00:21:52,410 --> 00:21:55,164
There are only two youngsters now

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00:21:55,250 --> 00:21:57,321
and they need help

225
00:22:01,570 --> 00:22:03,926
(Growling)

226
00:22:08,570 --> 00:22:13,361
A herd of gigantic adults
responds to their calls

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00:22:16,570 --> 00:22:21,247
One elderly female sizes up
the two newcomers

228
00:22:23,570 --> 00:22:26,005
She accepts them

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00:22:27,170 --> 00:22:32,086
They fall into line behind an adult,
safe at last

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00:22:55,490 --> 00:22:58,130
The herd is at full strength

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00:22:58,210 --> 00:23:02,966
It contains a range of members -
from 12-metre long adolescents

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00:23:03,050 --> 00:23:05,963
to adults three times their size

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00:23:06,050 --> 00:23:10,010
It is the mating season,
and for the first time,

234
00:23:10,090 --> 00:23:13,686
the female that hatched
ten years ago

235
00:23:13,770 --> 00:23:18,287
is old enough and large enough
to reproduce

236
00:23:18,370 --> 00:23:21,602
The males have started to display

237
00:23:21,690 --> 00:23:26,765
They rock back on their tails
to impress potential mates

238
00:23:29,330 --> 00:23:31,845
Occasionally, fights break out

239
00:23:31,930 --> 00:23:33,967
With creatures this size,

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00:23:34,050 --> 00:23:38,522
the forces at work during
these confrontations are colossal-

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00:23:38,610 --> 00:23:42,889
enough to shatter ribs
and shake the ground

242
00:23:44,970 --> 00:23:47,280
(Growling and bellowing)

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00:23:56,970 --> 00:23:59,929
The victor wins the right to mate

244
00:24:10,090 --> 00:24:14,209
Our female is approached
by a young male

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00:24:14,290 --> 00:24:18,489
She responds to his calls
first by stamping

246
00:24:18,570 --> 00:24:23,247
and then generating
very low frequency mating calls

247
00:24:23,330 --> 00:24:28,086
This infrasound is too low
for most animals to hear

248
00:24:28,170 --> 00:24:31,402
He picks these signals up
through the ground,

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00:24:31,490 --> 00:24:35,200
and responds by walking close to
her, rubbing his body down hers

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00:24:42,650 --> 00:24:44,687
She shows she is receptive

251
00:24:46,850 --> 00:24:51,845
Mating is a dangerous activity
for the female

252
00:24:51,930 --> 00:24:55,162
She'll carry at least
an extra 10 tonnes on her back

253
00:24:56,740 --> 00:24:59,933
As she has grown older,

254
00:25:00,020 --> 00:25:04,776
the vertebrae over her hips
have become fused and reinforced

255
00:25:04,860 --> 00:25:07,819
to help her cope with this ordeal

256
00:25:22,925 --> 00:25:27,078
After a few days,
the Diplodocus have calmed

257
00:25:28,725 --> 00:25:32,799
The female feeds
on the edge of the herd,

258
00:25:32,885 --> 00:25:37,641
but is not large enough
to be immune from attack,

259
00:25:37,725 --> 00:25:42,197
and she is unaware
she is being watched

260
00:25:43,725 --> 00:25:48,197
An Allosaurus knows
she is vulnerable

261
00:25:54,285 --> 00:25:59,121
The predators wait for her
to become distanced from the herd

262
00:26:39,285 --> 00:26:41,242
(Roars)

263
00:26:48,125 --> 00:26:52,244
Saved by the huge tail
of a larger Diplodocus

264
00:26:58,125 --> 00:27:01,914
She rejoins the herd
with deep wounds on her side,

265
00:27:02,005 --> 00:27:04,520
but she will recover

266
00:27:05,685 --> 00:27:08,757
Diplodocus can live for 100 years,

267
00:27:08,845 --> 00:27:11,485
and above a certain size,

268
00:27:11,565 --> 00:27:14,160
they have no natural predators

269
00:27:17,565 --> 00:27:21,036
Sauropods dominate
the late Jurassic

270
00:27:21,125 --> 00:27:25,404
It'll be millions of years
before new dinosaur herbivores

271
00:27:25,485 --> 00:27:27,442
evolve to replace them

272
00:27:27,525 --> 00:27:32,475
With their passing,
life will never again be this large

273
00:28:19,045 --> 00:28:22,243
Eventually, the mighty sauropods
went into decline

274
00:28:22,325 --> 00:28:24,681
Their lowland prairies
became flooded

275
00:28:24,765 --> 00:28:27,644
because the sea levels
began to rise

276
00:28:27,725 --> 00:28:30,081
This created vast inland seas

277
00:28:30,165 --> 00:28:31,838
In the next programme,

278
00:28:31,925 --> 00:28:35,475
we will meet the giant carnivores
that patrolled them