Planet Dinosaur (2011): Season 1, Episode 3 - Last Killers - full transcript

We're living through THE golden age
of dinosaur discoveries.

From all over the world,

a whole new generation
of dinosaurs has been revealed.

From the biggest giants
and the deadliest killers...

to the weird and the wonderful.

From the Arctic... to Africa.

From South America to Asia.

Using the latest evidence,
for the first time...

we have a truly global view
of these incredible animals.

In this episode,

we explore the last generation
of killer dinosaurs...



carnivores that took
killing to a new level.

At the end of the Cretaceous period,
75 million years ago,

these hunter-killers
had spread throughout the globe.

In the southern continents,

it was the powerful and muscular
Abelisaurids that reigned supreme.

Whereas in the north, it was the
famous Tyrannosaurs that dominated.

75 million years ago,
the Dinosaur Park formation in Canada

was home to two of
the largest Tyrannosaurs.

The biggest and heaviest
was Daspletosaurus.

In 2009, medical scanners were used

to look inside the brain cases
of these killers.

Of all the dinosaur groups,
Tyrannosaurs were discovered

to have one of the largest areas
devoted to smell...

something that would give them
a clear hunting advantage.



Back then, Cretaceous Alberta

was a vast coastal river plain
covered in forests...

the perfect hunting grounds
for Daspletosaurus.

At nine metres and three tonnes,

it's the dominant predator
in these forests.

Here, it relies on its acute
sense of smell and hearing,

as much as its sight,
to hunt its prey.

Chasmosaurus,

a rhino-sized behemoth,
bristling with defensive horns...

and an opponent befitting
a killer like Daspletosaurus.

Of all the tyrannosaurs,
T Rex might be the most famous,

but the evolutionary blueprint
for these predators

was laid down 10 million years
earlier, with Daspletosaurus.

Tyrannosaurs' effectiveness as
killers is clear from their anatomy.

They're massive, with huge, strong
skulls, and powerful muscular necks.

Forward-facing eyes
make tracking moving prey easy.

They've famously short arms,

but with these giant Tyrannosaurs,
it's all about the bite.

They had the most powerful bite
of any dinosaur with teeth that,

unlike the thin,
flesh-tearing blades of Carnosaurs,

are thick and strong,
easily able to crush bone and kill.

However, this Daspletosaurus
has lost the element of surprise.

The odds are now stacked
in the Chasmosaur's favour.

Even the most deadly predators
fail more often than they succeed.

Tyrannosaurus appeared locked
in a deadly evolutionary arms race

with the horned dinosaurs.

As one got bigger, so did the other.

It's a predator-prey relationship
that endured

for more than 65 million years.

Most striking are the head frills
of the horned dinosaurs.

The imposing frill of Chasmosaurus
is actually made of thin bone

and wouldn't stop
the bite of a Tyrannosaur.

But by making it look much bigger,
it had the desired effect.

The horns and frills of these
dinosaurs acted as visual deterrents,

even if they offered
little physical protection.

It meant that a fully grown
Chasmosaurus

would usually be safe
from most predators.

This Daspletosaurus
is just a youngster.

Even two Daspletosaurs
pose little threat.

But in 2005, a remarkable discovery
was announced.

In the Two Medicine Formation
of Montana,

a new dig revealed had unearthed
something quite extraordinary...

a collection
of Daspletosaurus fossils,

all buried at the same place
at the same time.

The implication is that
Daspletosaurus hunt in gangs.

Tyrannosaurs, like Daspletosaurus,
were so successful that,

by the late cretaceous, they were
the apex predator across virtually

all of North America and Asia.

In Asia, there was Alectrosaurus,
Alioramus and Tarbosaurus.

In America, Albertosaurus,
Gorgosaurus,

Daspletosaurus and T Rex.

But moving further north,
evidence of Tyrannosaurs

becomes increasingly rare.

In Alaska, fossils have been
excavated close to the Arctic Ocean.

It's the richest source of dinosaurs
that lived in the polar regions...

and it seems here, a different
type of killer dominated.

The most common plant-eater
in this region

is the highly social Edmontosaurus.

They're the largest duck-billed
dinosaur in North America...

and they are the perfect prey for
a very different type of predator.

Troodon may not look
as lethal as a Tyrannosaur,

but fossil evidence suggests
that these too were deadly hunters

surviving entirely on a diet of meat.

At first sight, it appears the adult
Edmontosaurus have little to fear.

12m in length
and weighing 3.5 tonnes,

they physically dwarf
this diminutive predator.

Troodon were usually small,
two-metre dinosaurs...

but the teeth from the Alaskan
Troodon showed something remarkable.

These Arctic predators were
almost twice as big as normal.

Troodon not only survived here,
they positively thrived.

And that's because
their hunting prowess

comes into its own after sunset.

This is a land where,
after late summer,

there are more hours
of darkness than light.

Troodon famously
have the largest brains

relative to their body size
of any dinosaur...

although what appears
more important are their eyes.

Not only are they forward facing,
making them active hunters,

but they are exceptionally large.

These are predators that can hunt
equally well after dark.

Although the group offers protection,

predators always choose
the easiest prey,

so it's the juvenile Edmontosaurs
that are at risk.

Separated from the group,

this youngster has made
a dangerous mistake.

The Alaskan dinosaur bone beds
are dominated

by juvenile Edmontosaurus remains.

Some show clear evidence
of Troodon bite marks.

It seems, despite its small size,
Troodon thrived here

by exploiting the vulnerability
of the juveniles

throughout the long,
dark, winter months.

With a steady food supply,

it means Troodon can survive
the harsh Arctic winters.

And, in doing so,
grew to almost double the size

of their cousins further south.

But these were the exception.

Wherever else Tyrannosaurs lived,
they were the largest predator,

living in groups that consist
of both youngsters and adults.

In these deadly packs, youngsters
provide the speed, adults the power.

It's a hunting strategy
that they use to deadly effect.

But despite appearances, this mob
attack isn't carefully planned.

There is no strategy
behind the actions of the gang.

It's merely opportunism.

And when the kill has been made,
the next battle soon begins.

In many Tyrannosaurs, we find holes
and gouges on the skulls,

injuries which turn out to be bite
marks made by other Tyrannosaurs.

In one Daspletosaurus fossil,
the tooth marks indicate

that an individual had been subject
to several attacks.

In another, the tip of a tooth

was left embedded
in the bone of its skull.

From this evidence,
we can assume that such groups

were far from harmonious...

and they certainly
aren't democratic.

In this world,
the strongest takes all.

Tyrannosaurs' domination of
the globe might have been total,

had it not been for a strange quirk
in the arrangement of the continents.

75 million years ago, the planet
had a clear north-south divide,

with no physical link
between the parts of the globe.

It meant the Tyrannosaurs couldn't
spread to the southern continents.

Here, a different type
of killer reigned supreme.

These were Abelisaurids.

In the last ten years,
Madagascar has provided

the most comprehensive evidence
about these predators.

70 million years ago,
Madagascar was already an island.

But its climate was much hotter
and drier than today.

In the Cretaceous period, Madagascar
was subject to devastating droughts.

And big predators like Majungasaurus

are especially vulnerable
to starvation.

Scavenging is the only way
to survive.

We thought Majungasaurus
was the top predator here.

But then, in 2003, some bones
of a number of Majungasaurs

were reported gouged
with teeth marks.

It appeared there was a bigger,
more brutal killer at large.

Majungasaurus also shares the plains

with smaller dinosaurs
like Rahonavis.

Being smaller means Rahonavis
needs less food to survive.

A carcass will attract
every big predator for miles around.

A male Majungasaurus,

attracted to the feast.

It is more than capable
of challenging for the carcass.

Majungasaurus has short arms
and can't grasp.

Like Tyrannosaurs,
it's all about the bite.

The shape of Majungasaurus'
skull and teeth

suggests a very different biting
style to the flesh-tearing dinosaurs.

With a broad, short
and muscular skull...

it was a dino better adapted
to biting and gripping,

rather than slashing its prey.

This fight is about more

than just winning
the feeding rights to a carcass.

When the bite marks
on the mauled Majungasaurus remains

were studied more closely...

the marks on the bones
were found to match

the only large carnivore
in the region.

There is no bigger killer
in these lands than Majungasaurus.

This is the first, irrefutable
evidence of dinosaur cannibalism.

It might seem shocking, but it's
a behaviour that clearly shows

the most successful killers

will exploit any situation
to their maximum advantage.

Daspletosaurus.

With a bite force unmatched
by any other dinosaur in the region,

these are killers
in a completely different league.

And this group have congregated
to take advantage of an annual event.

In Dinosaur Provincial Park,

thousands of bones
have been discovered,

scattered across the same rock layer.

They belong to the horned
dinosaur Centrosaurus...

and they appear to be the bone
beds of vast killing fields,

sites of wholesale slaughter.

This vast herd of Centrosaurus
are on the move...

from their nesting sites
on coastal lowlands to the east.

Unwittingly, they're moving towards
almost certain death.

Seasonal monsoons drives
the Centrosaurs inland,

away from coastal flooding.

It's what the Daspletosaurus
have been waiting for.

Herding behaviour
protects the many...

but at the expense of the few.

And things are about to get worse
for the Centrosaurs.

With a flooded river ahead
and the Daspletosaurus behind,

the stage is now set for a massacre.

But despite the rich pickings,
it's not the Daspletosaurs

that are responsible
for the scale of the slaughter.

There's an even more deadly
killer at work here.

Severe monsoon rains have transformed
shallow rivers into lethal torrents.

The real killer
is the weather itself.

Recent studies of this dense bone bed
indicate that 96% of the bones

are of a single species -
Centrosaurus...

and relatively few of the bones
display any bite marks.

The fossil evidence suggests
that this was a mass drowning...

the result of widespread
seasonal flooding...

an event that we have seen repeated
in over 20 different sites.

And when the waters recede,
new opportunities emerge.

Events like these provide
easy pickings for predators.

But even in the fight
for rotting flesh,

Daspletosaurus's authority
is absolute.

Tyrannosaurs in the north
and Abelisaurids in the south

were the supreme killers
of their age.

They dominated every continent
where they were found.

And together, they were
the last of the killer dinosaurs.