Donated by SergeiKThis little mammal is a scavenger.
Called Didelphodon,she is a marsupial
and specialises in raidingabandoned dinosaur nests.
This evening, she could be in luck.
Unfortunately, the smell of the nestblinds her senses to danger.
The end of the Cretaceous.
The continentsare taking their modern forms.
But this movementof the Earth's crust
has produced a surgein volcanic activity.
Massive eruptionsthat have lasted for centuries
have laid waste to landscapes,
filling the atmospherewith gases and debris.
This desolate worldis still ruled by dinosaurs,
as it has beenfor 160 million years,
but they are nearing the endof their reign.
Life on earth is choking to death.
Yet in the last two million years,
the dinosaurs'most infamous predator has appeared.
Tyrannosaurus, a five-tonne,13-metre long carnivore,
specifically evolvedto kill other giant dinosaurs.
This is a male.
He's been drawn to this volcanoby the smell of food.
The area is fullof geothermal springs
and the air thickwith sulphurous fumes.
But there is another smell here.
In one small valley,there is the stench of death.
Unwittingly, the Tyrannosaurushas been drawn into a natural trap.
Volcanic vents are producingpoisonous carbon monoxide,
and because it is heavier than air,
it has formed a suffocating layerclose to the ground.
The giant predatorstands above the layer,
but as he putshis head down to feed
he begins to feel the effects.
If he topples over now,he will never get up.
Eventually,his sheer size is his salvation.
As he stands up with his prize,his head just clears the gas layer.
There are still islands of greenerybetween the lava flows.
In the warm, moist climateof the late Cretaceous,
the vegetation has transformed.
Instead of conifers,
broad-leaved treesfill the forest canopy.
Driving this quiet revolutionamong the plants
is the remarkableevolution of flowers.
Their secret lies in theirintimate relationship with insects,
so close that some flowerscan only be pollinated by insects
and some insects, like butterflies,can only feed on flowers.
Among these new plants,the birds are flourishing,
and their calls forman ever-present chorus.
Millions of years of evolution
have also createdintimate relationships
among different types of dinosaurs.
Especially the delicate balancebetween predator and prey.
One dinosaurthat specialises in defence
is the extraordinary Ankylosaurus.
They are evolved to withstand attackeven from giant predators
like Tyrannosaurus.
At seven tonnes, Ankylosaurusare so heavily armoured
that even their eyelidsare hardened.
And if that wasn't enough,they have a formidable club
on the end of their tails.
Sadly, not even these magnificentcreatures have any defence
against the natural forcesthat are suffocating their world.
Nearby lies the Tyrannosaurus nest.
These are usuallyclosely guarded by the mother,
but this nest has been abandoned,
and a Didelphodonhas burrowed into the side.
Dinosaurs are vulnerable becausethey lay their eggs on the ground.
But size helps,
and the egg is a challengefor this marsupial.
Soon the age of the mammalswill dawn,
and they will grow massive,
but this is as bigas Cretaceous mammals get.
The Tyrannosaurus embryo insidethe abandoned egg is already dead.
The scent is a lureto another Didelphodon.
Many dinosaur embryos cannotsurvive in this volcanic environment
because acidic pollution
prevents their eggshellsfrom forming properly.
The mother is callingfor a new mate.
Tyrannosaurus have huge territoriesof hundreds of square kilometres.
Her challenge is to attracta wandering male.
She may have to calllike this for weeks.
One of the Tyrannosaurus'sprincipal sources of prey
are these bulky Torosaurus.
In the late Cretaceous, herds ofhorned herbivores are very common
and attract many predators.
It is rutting season. To display,males flush blood into their crests,
creating vivid patterns.
These displays helpto avoid physical contact.
With one-metre-long horns,
fighting can easily resultin bad injuries.
The best and the brightest crest
is all that is neededto settle arguments.
Occasionally,showing off is not enough
and males resort to brute force.
For this old Torosaurus,this was one fight too many.
He will never againchallenge for the right to mate.
The mating callof the Tyrannosaurus
continues to echoacross the volcanic slopes.
And it has been heard.
A male has killeda young Triceratops.
It's not just to satisfy his hunger.It is a gift.
Female Tyrannosaurusare larger and more aggressive,
and he courts her with food
to stop her attacking him on sight.
The female arrives.
She is wary.
The primary weaponof a Tyrannosaurus is its mouth.
The primary weaponof a Tyrannosaurus is its mouth.
Its arms are tinyso it can carry a massive jaw
and remain balanced.
This jaw can crush boneand tear off up to 70 kg of meat
with one bite.
The male keeps his distance.
Later that evening, they mate.
This is the first of many couplings
as the male stays by the femalewhile she is receptive -
ready to see off any other males.
On the lava flows,a group of Anatotitan
wanders between islands of greenery.
These animals are membersof the hadrosaur family,
the most common group of dinosaursin the Late Cretaceous.
But their kind has evolved
to thrive in lush lowland swamps,not in an ash wilderness.
Three days have passed.
The Triceratops carcasshas been stripped
and the female Tyrannosaurusis beginning to tire of her mate.
The male knows better than to stay.
Gliding in from the coast,
a magnificent pterosaur,Quetzalcoatlus, is hunting for food.
This is now a rare sight.
For 20 million years, these flyingreptiles have been in decline.
These 13-metre giantsare the only ones left.
And this is a dangerous place to be.
One-tonne crocodileslive in the lake,
and could easily dragthe delicate glider to his death.
Driven on to extinction.
The skies of the futurebelong to the birds
that already flourish around him.
Months have passed,and the female Tyrannosaurus
has built a new nest,camouflaged in the forest.
Mother keeps watch.
For the full two monthsof the eggs' incubation,
she will not leave or even eat.
She knows her nestis a magnet to scavengers.
Like this Dromaeosaur.
His cautious approachis watched by the Tyrannosaurus.
She judges exactlywhen he has got too close.
As the sun sets, another threatcomes out to haunt the mother.
With food becoming scarce,the mammals are getting bolder.
She checks to make suremore have not burrowed in,
then returns to her vigil.
The weeks pass, and abovethe brilliant volcanic sunsets,
there are signs of an even moredestructive natural disaster.
Showers of shooting starsherald the approach of a giant comet
on a collision coursewith the Earth.
Far below,the dinosaurs are oblivious.
The Torosaurus herdcontinues to feed.
The Torosaurus herdcontinues to feed.
Nervous of moonlight predators,
younger animals seek protectionamong the larger adults.
Using the darkness, a pairof Dromaeosaurs unsettle the herd
and isolate one of the youngsters.
Safe. But the predators have tastedblood and will not give up easily.
Morning revealsthe results of last night's tussle.
The little Torosaurus lost his fightwith the predators.
For the herd, it is a blow.Too few young are being born
in this polluted environment.
A Didelphodonis already at the carcass.
These little opportunists are aboutthe only animals that are thriving.
During their reign, dinosaurshave adapted to huge changes
but now they facea combination of events
that will spell their doom.
After trekkingacross the ash fields,
Anatotitans gather rounda stagnant pool to drink and feed.
Huge batteries of chewing teeth
make short work of the vegetation.
Once again, the predators makethe water's edge a dangerous place.
The group senses dangerand starts to break up.
The mother Tyrannosaurushas broken her fast
and is back with a vengeance.
Nearby is the reason for her hunger.Three Tyrannosaurus chicks.
The only survivorsfrom a clutch of twelve.
The moment they hear the kill,
they start calling for food.
The mother deliversa slab of Anatotitan meat.
Only four weeks oldand less than a metre high,
competition is intense between them.
One is already picked onby the others.
They'll remain under their mother'sprotection for another two months.
Soon after that,she will abandon them,
or worse, view them as food.
It is unlikelythe outcast will last that long.
A few days laterand the mother rests
in the warm afternoon sun.
There is no signof the smaller runt.
He may have been killedby his siblings.
Increasingly, the bickering pair arehappy to wander from their mother
to explore their surroundings.
From the undergrowth,a snake watches.
These reptileshave only recently evolved
from the same family as lizards,
but they specialise in huntingwarm-blooded creatures like mammals.
They use sensory pitson their snouts
as a way of detecting the heatsignatures of other animals.
It doesn't like what it sees.
While the chicks play, they areoblivious to approaching danger.
The mother is caughtcompletely by surprise.
The Ankylosaurus has very littlebrain inside its reinforced skull,
so when faced with danger, it reactsautomatically and aggressively.
Normally,Tyrannosaurus would retreat,
but she will not abandon her young.
The blow has crackedthe mother's femur
and ruptured internal organs.
She limps away in agony.
That night, the usual evening chorus
is joined by the whimperof a dying giant.
By morning, she lies lifelesson the baking ash fields.
The chicks stand expectantly bythe colossal corpse of their mother.
Hours pass, and still they wait.
But their fate will now be settled,
along with all the othergiant dinosaurs of the Cretaceous.
3,000 km to the south, the massivecomet crashes into Earth.
The light from the impactfades in silence.
Then the shock waves arrive.
Next comes the blast front.
Finally a rain of molten rock startsto fall out of the darkening sky -
Finally a rain of molten rock startsto fall out of the darkening sky -
this is the endof the age of the dinosaurs.
The comet struck the Gulf of Mexico
with the force of 10 billionHiroshima bombs.
In the catastrophic climate changesthat followed,
65% of life died out.
It took millions of yearsfor Earth to recover,
and when it did,the giant dinosaurs were gone,
never to return.
In their place have emerged otherpowerful and beautiful creatures.
We now know one small groupof dinosaurs
did survive the extinction -
and they are all around us today -
the birds.