Original subtitles

Over 66 million years ago...

SCREECHING

..our world was ruled...

SNARLS

ROARS

..by dinosaurs.

GROWLS

BELLOWING

The largest animals that have ever walked the Earth.

SCREECHES

Today, dinosaur experts across the globe

are uncovering the bones they left behind...

..allowing us to imagine how these extraordinary creatures

may have lived...

..so that we can tell their stories...

..and they...

..can walk again.

ROARS

Deep in the ancient forests of Alberta, Canada...

LOW CONVERSATION

..a team of dinosaur hunters

has come to unearth an astonishing find.

We've got at least three bones sticking out here.

Discovered on the edge of a creek...

..are the bones of a pachyrhinosaurus...

..a unique horned dinosaur.

Lying here is a toddler...

It's such a tiny little bone.

..they call Albie.

Don't think I've seen one that small before.

And he's not alone.

He's part of one of the largest dinosaur herds ever found...

..numbering in the thousands.

We have big adults, we have little babies,

we have every age in between.

This was a huge herd of animals.

Why so many are buried here is a mystery.

But by studying the bones,

we can begin to tell their extraordinary story.

73 million years ago.

What will one day be north-western Canada

is part of a landmass called Laramidia.

Mountain ranges extend for thousands of miles...

WIND WHISTLES

..towering over a wilderness of dense forested valleys.

BIRDSONG

BELLOWING

This vast terrain is roamed by gigantic groups

of plant-eating dinosaurs...

..that, like today's caribou or elk,

migrate each season.

And by far the largest of these prehistoric herds...

..are the pachyrhinosaurus.

A close relative of triceratops,

these social dinosaurs have spent the winter in the south.

But with the land now almost completely bare...

..staying here would mean starvation.

So the herd is setting out on an epic 400-mile trek north...

..where, by summer,

the vegetation should be abundant.

SNORTING AND GRUNTING

It will be a gruelling journey...

..especially if you're one of the youngest...

..like Albie.

At less than a year old, he's only half a metre tall...

..which makes keeping up...

..a bit of a challenge.

HE YOWLS

Even so, he must stay close to his mother...

HE YOWLS

..because the herd aren't the only ones that are hungry.

SQUAWKING

Following in their wake,

an azhdarchid pterosaur.

With a six-metre wingspan and estimated speed of 60mph...

..a young pachyrhinosaurus makes for an easy target.

HE CALLS

BELLOWS

A close call.

But it's only the start of the challenges they will face...

..as the search for food takes them across

the prehistoric wilderness.

LOW CONVERSATION

73 million years later...

..the work to understand this enormous herd

is well under way.

There's a pretty large cluster of bones there.

Seem to belong, potentially, to a large animal.

It's a painstaking process...

..led by Dr Emily Bamforth...

..who is piecing together

the journey that brought the herd here.

And in one corner of the site...

Is that a little vertebra?

..something has caught her eye.

Oh, man, that is so little!

Right in this corner.

Baby bone, baby bone, baby bone.

Emerging from the rock are not just Albie's bones,

but those of other youngsters.

And comparing their size...

Juvenile vertebra is 7cm.

That's another really young animal.

..reveals something significant.

All of the juveniles here, these are all about a year old. Wow.

They're all the same age...

..born around the same time.

They have to have been born

on the previous summer's migration.

That, to me, is interesting.

Emily's findings suggest the herd was making

its yearly journey for more than just food.

They were returning to their summer nesting ground.

And joining them are thousands more...

..as every pachyrhinosaurus on the continent...

..heads north...

..merging into one of the greatest spectacles

of the prehistoric world.

BELLOWS

But with such a colossal gathering...

..tension is in the air.

Breeding season is upon them...

..so bulls in the herd must compete

for their right to mate.

BELLOWS LOUDLY

From old veterans...

..to their younger rivals.

And there's only one way...

..to prove their worth.

In a contest as brutal as this...

ALBIE SQUEAKS

..Albie's mother must keep a watchful eye...

..making sure he isn't trampled, or even killed.

But as one of the youngest,

curiosity gets the better of him.

ALBIE SQUEAKS

Using their thick armoured noses...

..each male seeks to deliver a bone-shattering blow.

And the ultimate target...

..is behind the other's horned armour.

The young rival...

BELLOWS

..gains the upper hand.

GRUNTS

That is weird.

At the dig site, uncovering what appears to be

the rib of a huge bull...

Seems like the rib trends this way

but then starts back up that way.

..Emily and her teammate Max Scott

are finding evidence of a punishing injury.

This part of the rib and that part of the rib are slightly offset,

so it looks as if this rib

has actually been broken in the middle.

Gosh. It seems like it was almost shoved off to one side.

The rib is twice as thick as a bear's.

The fact it snapped

means this bull suffered a potentially-fatal blow.

It would have to be a considerable impact,

so either the opponent striking it really hard,

or when it fell sideways.

Whatever happened, it would have been very painful.

Like, with an impact this size,

the rib could puncture the lung.

But examining the fossil reveals something curious.

It's really bulgy there.

So I think that's a bone callus.

Bone calluses form over a break as part of the healing process.

The bone has broken

and has actually shifted sideways while the animal was alive,

and this big bony bump

healed around it and set it.

Would have been very painful for the animal,

but they would have survived it.

It's really quite an impressive feat.

Really shows just how tough he really was.

The healed injury is important evidence.

LABOURED BREATHS

It suggests the strongest bulls in the herd...

..were capable of taking severe punishment...

BELLOWING

..and getting back on their feet.

BELLOWS

An ability they'd need...

..to come out on top.

BELLOWS

GRUNTS

With a winner firmly established...

..the monumental herd continues its journey to the fertile north.

ALBIE SQUEAKS

But though the fighting may have subsided...

..for Albie, the danger is only just beginning.

HE WHINES

In the chaos,

he has become separated from his mother...

..and lost in the crowd.

In a herd of this magnitude...

..finding her won't be easy.

Look at this.

But at the dig site,

evidence is emerging that suggests every one of this enormous herd

may have looked unique.

It looks like it's relatively complete

and this is a big one.

Buried in the rock is an incredibly rare find -

an adult's bony headdress...

..known as the frill.

This might be the front and that's the back.

Yeah, that's what I was thinking too.

So, like, the nose is over here somewhere,

and, like, the body is back there.

I don't think I've ever seen any

where one of the middle horns

is going the opposite direction of the other.

Given this frill's highly unusual shape,

Emily is keen to compare it with others found in the creek.

So, on this individual,

the horns that stick out the side of the frill,

they're straight,

whereas this one is interesting.

This is an asymmetrical frill,

so this horn is straight

and that one is curled.

Each frill is distinct from the other.

It is very striking that these frills,

despite being from almost exactly the same place

in the bone bed, from the same community of animals,

like, they're still very different from one another.

Remarkably, no two frills found at the site

have ever looked the same...

..leading the team to think their variation

served a crucial purpose.

Based on the differences in these frill horns,

it would be very easy for the individuals

to recognise each other.

Yeah. In a herd environment like this,

it's very important to be able to recognise

your friends and your family easily.

With every member of the herd displaying their own unique frill...

ALBIE YOWLS

..it could help a youngster like Albie...

..pick out his mother from the masses...

..by scanning each and every one...

..for her familiar features.

HE CALLS

But in the sea of pachyrhinosaurus streaming past...

..she is still...

..nowhere to be seen.

HE YOWLS

Without his mother's protection...

..he has little chance of surviving the long journey...

..alone.

PLAINTIVE BELLOWS

FOLIAGE SNAPPING

Until...

GENTLE GRUNT

..finally...

..the distinctive outline of a frill...

..he knows better than any other.

And a mother relieved to have found her young.

YOWLS AND GRUNTS

BOTH GRUNT SOFTLY

But though reunited...

..there is much danger still ahead.

30 miles from the main dig site...

..Emily and palaeontologist Jackson Sweder...

..have travelled to the edge of a forest.

Here, ancient footprints follow the herd's route.

That's a toe. Yeah.

And that's a toe. You seen the third one here?

See it again, missing that toe? Maybe... Yeah, missing. Yeah.

Once you get your eye in,

they're actually all over the place. LAUGHING: They're everywhere.

And one stands out from all the others.

Clearly a carnivore.

And you can even see the claws.

That's a point.

Big, big animal as well.

What, eight metres? Yeah.

To confirm the identity of this large predator...

..Emily and Jackson use liquid rubber

to make a cast that reveals how it moved.

The back of the track is shallower than these toes here.

The toes are super deep.

So it's moving on the front of its feet,

sort of like the fast animals today, like cheetahs, would do.

Definitely wider than it is deep,

so it can move side to side if it has to.

So probably a very agile animal as well.

This kind of speed and agility

belongs to only one predator in the region.

A terrifying relative of T-rex

that hunted in packs.

Those pachyrhinosaurus

definitely would have had to worry about this animal. Yeah.

It's very efficient at moving long distances.

It could follow them for miles

and just wait for an opportunity.

The gorgosaurus.

QUIET SNARLING

With exceptional hearing...

..and a sense of smell more powerful than any other dinosaur...

..it's thought they could track their prey

from up to ten miles away...

..allowing them to ambush at a moment of their choosing.

Unaware of the approaching threat,

the herd moves deeper into the forest.

Surrounded by its narrow pathways...

..an attack could come from any direction.

HE SNUFFLES

BRANCH SNAPS

But there is no sign of the danger...yet.

SNORING

DISTANT BELLOWING

SNORTS

QUIET THUDDING

DISTANT FOLIAGE SNAPPING

The sound of intruders...

..draws Albie away from the herd.

FOLIAGE SNAPPING

But these aren't the stealthy footsteps of a gorgosaurus.

Something else is closing in.

Take care with your footing.

Journeying along the herd's migration route,

Emily and her team have discovered evidence

of another mysterious dinosaur...

..which has emerged on the edge of what is now a river.

Oh!

Yeah, it's a little chilly. Oh, yeah, it's cold.

Exposed by receding water,

its fossilised remains are all along the river bank.

It's huge.

It's just packed with stuff.

It's crazy that it's just kind of sitting out here on the surface.

Man, that's big.

It definitely seems to be in a layer here...

Whatever this is.

And it isn't long before the team hits the jackpot.

Oh, my goodness!

That's a huge bone.

Buried in the rock is part of its gigantic hind limb.

Do you have a measuring tape?

Yeah, let's just take a quick measurement.

They can use this to estimate the animal's full size.

It's really long.

Even if it's only to there,

that's still definitely over a metre.

Yeah. I would say, with legs like this,

it's probably about the size of a school bus,

around nine metres long or so. That's huge.

There's not much that gets bigger than this.

Even larger than a gorgosaurus...

..its nine-metre length means it could be only one dinosaur.

And the forest is the ideal place

for it to find its next meal.

FOLIAGE SNAPS

SNORTING

MUNCHING

But this isn't a killer.

ALBIE SQUEAKS

It's an Edmontosaurus...

THUDDING STEPS

MUNCHING

..which, along with its herd, is on the same migration north.

BELLOWS

As plant-eaters, they pose no threat...

..but these six-tonne giants...

FOLIAGE SNAPS

..make a lot of noise.

FOLIAGE SNAPS

FOLIAGE SNAPPING

DISTANT SQUAWKING

DISTANT ROARING

RUMBLING GRUNTS

..and it's drawing the pack of hungry gorgosaurus

straight towards them.

GRUNTS

BELLOWS

BELLOWING

SNARLING

IT ROARS

FOLIAGE SNAPPING

MUNCHING

For Albie, it's another narrow escape.

And as the herd pushes on,

the aurora lighting up the skies above...

..is a sign their journey north is almost over.

Do you have a chisel? Yep.

Not far from the main dig site...

..Emily and Jackson are finding evidence

of exactly what the herd was looking for.

That's huge. Yeah.

An abundance of food just waiting to be discovered.

There's so many different plants here,

just on this one slab.

Not just big leaves like this.

Also lots of flowering plants as well.

All these things would be really great food for pachyrhinosaurus.

The plants in these rocks

would have flourished in the summer...

..in time for the herd's nesting season.

Looking at all of these plants,

there's enough food for the adults and the juveniles.

More than enough to draw the pachyrhinosaurus up here.

And when the babies hatch,

there's food for the babies as well.

This place would mark the end of the herd's long migration.

A haven

where they could settle

and begin to nest.

BIRDSONG

LOWING AND GRUNTING

But while the exhausting 400-mile walk...

..may finally be over...

..there is one problem they haven't left behind.

NEARBY SNARLING

The gorgosaurus have stayed close.

BELLOWING

And with the pachyrhinosaurus backed up against the river...

..it gives these ferocious predators

the perfect opportunity...

..to pick off one of the herd's more vulnerable members.

SQUEAKING

ALBIE SQUEAKS

SNARLS

ROARS

HE SQUEAKS

But Albie is not alone.

SHE BELLOWS

His mother's instinct is to fight.

But their confrontation is about to pale into insignificance.

THUNDER CRASHES

Both predator...

..and prey

face a far greater threat.

Investigating what happened at the end of the herd's journey...

OK, move to the next point.

..and why so many are buried here...

..Emily's team is mapping the bones.

We've obviously got a pretty large cluster in that corner.

Those two are so close together... They are so, so close together, man.

It's pretty much, like, right up against... Yeah.

All right. Let's go.

They can then scan to create a full 3D model of the site.

It's coming through really well.

Yeah. You can see the patterning on the surface of the bone.

The imaging allows them to see exactly how the fossils are laid out.

You can see how the bones are stacked

on top of each other.

Everything here is bone.

There's actually very little rock in between there.

It's just a solid mass of bone material.

You can kind of see ribs of just about every size,

just even in this one pocket here.

And they're clearly all from different individuals,

cos they're all different sizes.

The bones of young and old are jumbled together.

And there's even more in the ground

than the team first realised.

You think of the sheer density of bones

in just this little area that we've scanned

and then put that together with the grid mapping

Perfect. Perfect.

..there's something like 100 to 300 bones per square metre.

And then we know the bone bed goes back into the hill

for another kilometre.

Good for now.

Their findings bring their estimate of pachyrhinosaurus

preserved at the site...

..into the tens of thousands.

To have died in such large numbers,

they must have faced a catastrophic event.

SAW BUZZES

Looking for answers...

..Emily and Max cut deep into the rock that encases the herd.

EMILY STRAINS

Tilt it up.

I just want to take a look at the cross-section.

It reveals a vital clue.

Look at this piece! All of that black,

it's plant material that's been shredded.

Something has picked up the mud

and has, like, twisted it with enough energy

to move the amount of material

and to shred the plants up like that.

And that's right in with the bones.

And all these swirls in here?

Something dramatic has happened that's involved water.

You can see where it's actually cut down

into the rock underneath it, like a fossilised wave.

And so this was a huge energy event.

The evidence all points to one thing.

THUNDER CRASHES

PANICKED BELLOWING

A devastating flash flood...

..triggered by huge storms...

..raging over the mountains.

Water cascades into the valley...

..swelling into an unstoppable torrent...

..that destroys everything in its path.

DEEP RUMBLING

GRUNTING AND BELLOWING

HE SQUEAKS

As the floodwaters near...

..the herd begins to panic.

Mother and child...

..waiting by each other's side.

ALBIE YOWLS

HE SQUEAKS

WATER RUSHING

Little could have withstood a flood on this scale.

And for Albie and much of his herd...

..it marks a tragic end.

But despite the devastation,

this was perhaps not the end for them all.

Just under 30 miles north of the main dig site...

Come on, Esther.

..Emily and Jackson

have travelled out into the hills of Canada's Grande Prairie...

..to investigate an incredible find.

So, there's three sites that have been identified.

Right. I think that's one of them.

And the other two...

I think there's one over there

and there's one behind us as well.

Across the area, a series of fossils has been unearthed...

..that point to an extraordinary possibility.

Looks like a toe bone.

But absolutely tiny.

That also is from a very, very small animal.

Like, that, to me, looks like it's from an animal

that has either just hatched, like a hatchling,

or is actually still in the egg,

an embryonic dinosaur.

An animal this size has to have been born here.

The young belong to both pachyrhinosaurus

and Edmontosaurus.

Dinosaurs that were heading for the same destination.

To me, it's not a coincidence that they're both here.

We're only 30 or 40km away from the site of the flood

so surviving animals could eventually

have made their way here.

This might have been the nesting ground

for both of these megaherbivores after the flood.

Emily and Jackson are continuing to look for more evidence.

But this remarkable discovery...

SQUAWKING

..means that maybe...

..despite all the odds...

..some of the herd did survive...

..continuing on to find another place to nest.

Survivors...

BELLOWS

..with a chance to pave the way...

..for the next generation to thrive.

So that one day...

..their herd can rise again.

BELLOWS

One of the largest dinosaurs ever to walk the Earth...

..goes looking...

..for love.

A quest...

..that will become a life-and-death struggle.