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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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Life is at its harshest

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in the far north and south
of planet Earth.

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Dinosaurs, however, have managed
to colonize these polar regions.

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In the far north of America,
this tiny hunter, a dromaeosaur,

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has managed to survive three months
of near-total darkness.

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And now, at last, spring has come.

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She has a coat of feathers,

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for she's able to generate heat
in her body

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and needs to retain all she can.

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A challenge for all dinosaurs
in these cold latitudes.

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As she moves quickly
over the surface of the snow,

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she checks on the places
where she has found food in the past.

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In this icy world,
no opportunity is too small to be ignored.

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And to succeed, as usual,

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you need good… timing.

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Although at this time in Earth's history,

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the polar regions are relatively warm,

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these lands are, nonetheless,
ruled by extreme seasonal change.

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When the sun rises for the first time
in almost three months,

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every animal must be ready
to make the most of the daylight

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and the warmer days that are to come.

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The little dromaeosaurs
must work together,

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if they are to take on big prey.

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And here comes
their first chance of the season.

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A herd of hadrosaurs.

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These duck-billed dinosaurs
pass through here every year.

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Nomads in search of the fresh vegetation
brought by the spring.

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They're huge.

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The only chance the dromaeosaurs will have
is to work as a team.

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There's a river ahead,
which the herd will have to cross.

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And the dromaeosaurs know
that some never make it.

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As winter slackens its grip,
meltwater begins to flow with great power.

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The herd must wade through this deep,
fast-flowing water.

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The leaders try to select
the safest crossing.

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The herd follow cautiously.

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Young keep close to their parents.

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Putting a foot wrong here
could cost them their life.

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The adults, awaiting their turn,
grow nervous.

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And this bottleneck
gives the dromaeosaurs a chance.

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Their target will be the young.

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Panic begins to spread through the herd.

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What should have been
an orderly crossing turns to chaos.

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Parents and young are separated.

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A lucky escape.

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The column re-forms
and continues its journey.

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The dromaeosaurs
seem to have missed their chance…

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but the river
has done their work for them.

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There are always casualties.

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It's a feast. And more food
than these hunters have had all winter.

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In the ice world,
seasonal opportunity is brief.

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Spring is short,
and summer will soon be over.

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There's a lot to be done
before the challenges of winter return.

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Downstream, as the rivers broaden
and begin to slow,

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they start to drop their loads of silt,

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and a network of islands appears.

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Some animals have
already seized the moment

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to assemble for the spring rituals.

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Spring, at last, has truly arrived.

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Dozens of male Ornithomimus are preparing

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for the most important moment
of their year.

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These strange ostrich-like dinosaurs
choose the safety of these islands

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to scrape out shallow craters,
the first stage in making a nest.

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When the females arrive,

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they will choose to mate with the males
who've made the best one.

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Late arrivals find that space
is already in short supply.

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The only space left
is on the island's margin.

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And finding a place to nest
is only just the start.

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When eggs are eventually laid,

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they will need to be kept warm
in a bed of vegetation.

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Finding enough nesting material
is not easy…

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which is why some Ornithomimus
resort to thievery.

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One advantage of arriving late

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is that your neighbors
have already done the hard work.

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An unguarded nest
is too much of a temptation.

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In colonies like this,
thievery can be so common

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that some nesting material,
at one time or another,

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will have been part
of almost every nest on the island.

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But robbery is risky.

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Caught in the act.

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A couple of hadrosaurs wander by.

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They will eat leafy branches.

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So, you have to be able
to defend your property.

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It can take several years
to perfect nest-building skills.

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But success doesn't only rely
on experience.

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In a crowded colony,
there's always another potential victim.

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For Ornithomimus,
these river islands will provide sanctuary

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for both the eggs
and the young when they hatch.

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Further north, temperatures are lower
and conditions are tougher.

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Yet that's where these enormous
crested hadrosaurs are heading

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to take advantage
of one site in particular.

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One that has something special to offer.

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The long necks of these dinosaurs
are particularly elegant

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and give them their name.

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Olorotitan, "Giant Swan."

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Their calls are amplified
by their head crests, which are hollow.

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They're heading for one of the world's
largest volcanic regions.

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It's a dangerous and hostile place.

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But the Olorotitans return to it,
year after year…

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because the volcanoes
keep the ground particularly well-heated.

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So, this is where they nest.

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The warm volcanic sand
serves as an incubator for their eggs.

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And a few weeks after
the arrival of the herd, the eggs hatch.

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Hadrosaurs look after
their young with care.

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They bring mouthfuls of plants
for them to eat.

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Each nest may contain over 20 youngsters.

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The babies have arrived at a time
of brief but rich summer plenty.

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Fueled by a sun that for weeks never sets,

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horsetails here grow fast

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and in sufficient numbers
to feed the whole herd.

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These plants contain more nutrients
than the lushest grass.

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And in the long summer days,
the hadrosaur babies grow quickly.

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They can reach half their adult size
in their first year.

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Right now, these volcanic wetlands

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are the most productive places
on the planet.

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Both above…

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and below the surface of the water.

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But that very productivity
brings problems for the hadrosaurs.

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Warm, shallow pools are an excellent
breeding ground

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for mosquitoes.

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Every year, this paradise
turns into a living hell.

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Hadrosaurs have surprisingly thin skin,

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and so, have little defense
against bloodsucking insects.

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Constant irritation makes it hard to feed,

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and they become dangerously weakened.

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And babies can lose blood
in life-threatening quantities.

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Eventually, the herd is forced to move on
to escape the plague.

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If the young can't keep up,
their mothers abandon them.

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As they go higher,
stronger winds bring some relief.

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But only for those able to walk that far.

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Of the hundreds of hadrosaur babies born,
only one in ten survives their first year.

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But those that do have a good chance
of reaching adulthood.

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By nesting in this volcanic valley,

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the parents give their young
the best possible start in life.

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Although the short and warm polar summer
is a time of great plenty,

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it can also bring perils.

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Warm air rises
and becomes charged electrically.

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And that creates frequent
and violent lightning storms.

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In the north of America,

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the lush growth
fueled by constant sunlight

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has now been baked tinder-dry.

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Most animals flee from the flames.

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But for some,
the disaster creates opportunities.

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This six-foot-long dinosaur, a troodontid,

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is one of the smaller members
of the theropod group.

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Its huge eyes give it acute sight,
even in this smoky gloom.

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And for its size, its brain is one
of the largest on the planet.

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It's the most intelligent, adaptable,
and successful hunter in the Arctic.

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At the fire's edge,

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troodontids gather to prey on animals
that are trying to escape the flames.

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Anything that spreads the fire
creates more opportunities

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for the most ingenious arctic hunter
of its time.

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Success.

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With the short summer over,

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the forests that survived the summer fires
start to change color.

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It is autumn's final flourish
before the months of darkness begin.

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In the Antarctic,
ice clings to the highest mountains

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even in the summer months.

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But now, with temperatures falling
and the day's shortening,

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the polar winter is spreading once more
across the land.

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Animals must now prepare for its return.

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The southern hemisphere
has its own species of dinosaurs.

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These three are young Antarctopelta,
small plant-eating dinosaurs.

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They're also one of this world's
most heavily armored animals.

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Even so, youngsters are safer together.

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This far south,

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the plants on which they depend
stop growing for months on end.

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As winter approaches,
these juveniles spend more time resting.

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Sheltering together conserves heat
and, therefore, energy.

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With powerful front limbs,
they can enlarge this winter den.

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But each time they return,
they've grown a little bigger.

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Their den seems a little smaller,

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and the brotherly bond
starts to wear a little thin.

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For every growing animal,
this is a vulnerable time.

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A time when they need to separate

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and each take its first tentative steps
to find a territory of its own.

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00:28:50,105 --> 00:28:54,401
Herds of hadrosaurs
are once again on the move.

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00:28:58,071 --> 00:29:01,867
With little to eat,
these huge herbivores return

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to look for food in warmer lands…

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leaving others to endure
the freezing polar winter.

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00:29:32,481 --> 00:29:34,316
Finding a suitable territory

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can take animals far from
the place where their lives began.

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00:29:39,988 --> 00:29:43,492
It's a search that many will not survive.

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00:29:55,379 --> 00:29:59,424
A good territory must have a place
in which to shelter.

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A cave, perhaps.

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00:30:11,854 --> 00:30:14,273
Even in the coldest months,

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the temperature in most caves
hardly varies.

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But he is not the first
to be attracted by this one.

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This cave glows.

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00:30:46,763 --> 00:30:51,476
These are the tiny lures
of fungus gnat larvae

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that produce light
to attract their insect prey.

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This is the perfect place

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for an Antarctopelta to escape
the worst winter weather.

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He will be safe
beneath these strange living stars…

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while outside, snow begins to fall.

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00:31:39,024 --> 00:31:43,695
In the coldest months,
the far north of the Arctic can freeze

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into a spectacular winter wonderland.

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00:31:50,327 --> 00:31:54,831
Not all dinosaurs choose to leave
or to seek shelter.

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00:31:56,291 --> 00:31:59,503
The largest have the strength
to tough it out.

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Pachyrhinosaurs.

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Two-ton herbivores
with extravagantly armored heads.

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They seek refuge in the forest,

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stripping the last leaves
from dormant trees

220
00:32:18,188 --> 00:32:20,899
and rooting through ferns
for fallen fruit.

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The autumn rut is over,

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but less dominant males still try
to push their way up the social hierarchy.

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00:32:36,582 --> 00:32:38,876
But they've forgotten who's in charge.

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This old bull is still a formidable force

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and one that few dare to challenge.

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Battling males barely have time
to eat or rest.

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With food now scarce,
it's hard to rebuild strength,

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and injuries take longer to heal.

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To make matters worse…

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the Arctic's most powerful predator
is always on the prowl.

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Nanuqsaurus.

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00:33:45,234 --> 00:33:47,861
A smaller relative of T. rex,

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it's still just big enough
to tackle a pachyrhinosaur.

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For these ancient adversaries,
in these conditions,

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the battle will be resolved
not by surprise, but by strategy.

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Amongst the trees,
it's hard for the herd to stand as one.

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Individuals could be quickly isolated.

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00:34:38,996 --> 00:34:45,918
The nervous herd makes a tactical retreat
to open ground.

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00:34:48,922 --> 00:34:51,049
The nanuqsaurs follow.

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Out here,
the herd will be able to close ranks

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and form an impenetrable wall
of armored heads and muscle.

242
00:35:40,432 --> 00:35:42,643
The blizzard worsens.

243
00:35:47,147 --> 00:35:48,982
It's an uneasy standoff.

244
00:35:51,443 --> 00:35:54,780
These confrontations can last for days.

245
00:36:11,588 --> 00:36:15,300
The herd should be safe
as long as they stick together.

246
00:36:18,720 --> 00:36:21,974
But the nanuqsaurs bide their time…

247
00:36:24,184 --> 00:36:27,479
and occasionally test for weakness.

248
00:36:42,494 --> 00:36:45,581
The blizzard now brings a temporary truce.

249
00:37:07,352 --> 00:37:13,901
But as soon as it's over, battle resumes.

250
00:37:21,783 --> 00:37:23,744
In this test of nerve,

251
00:37:24,453 --> 00:37:28,123
all it takes is for one animal
to break ranks…

252
00:37:30,667 --> 00:37:33,837
and panic quickly spreads.

253
00:37:38,842 --> 00:37:42,513
With the herd on the run,
the predators have a chance.

254
00:37:54,858 --> 00:37:56,568
As the chase goes on,

255
00:37:56,652 --> 00:38:00,489
one tiring bull fails
to keep up with the rest.

256
00:38:05,661 --> 00:38:11,500
Until all he can do is turn
and face his attackers.

257
00:38:33,647 --> 00:38:37,651
One pachyrhinosaur has lost the battle.

258
00:38:41,864 --> 00:38:44,950
But the war will go on all winter.

259
00:38:50,122 --> 00:38:53,083
The animals here
now face months of total darkness

260
00:38:53,166 --> 00:38:58,714
before the sun returns and brings relief
to the extraordinary creatures

261
00:39:00,215 --> 00:39:02,926
in the world of ice.

262
00:39:11,810 --> 00:39:13,770
Next on Prehistoric Planet,

263
00:39:13,854 --> 00:39:17,983
a flying giant the size of a giraffe
hunts its prey

264
00:39:18,066 --> 00:39:21,695
amongst the tangled trees
of a prehistoric forest.

265
00:39:22,988 --> 00:39:25,532
And under the canopy on this green planet,

266
00:39:25,616 --> 00:39:31,246
dinosaurs ambush, display,
and even journey underground.

267
00:39:31,330 --> 00:39:34,416
To discover the science
behind the stories,

268
00:39:34,499 --> 00:39:38,921
go now
to the Prehistoric Planet show page.