BBC Dinosaur Planet (2011) s01e06 Episode Script

The Great Survivors

We are 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 .
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and the deadliest killers, to the weird and 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 dinosaur's extraordinary ability to survive.
And witness how they have transformed over millions of years into some of the most alien-looking animals the world has ever seen.
This astonishing capacity to evolve into ever more diverse and bizarre forms meant that it helped them not only spread throughout the world, but also dominate life upon it.
Dinosaurs lived for on Earth for more than 160 million years, most famously throughout the Jurassic period.
But it was during the later Cretaceous period that the biggest, baddest and most bizarre dinosaurs lived.
By the end of the Cretaceous, dinosaurs were flourishing on every continent.
Even dinosaurs that had been around for over 100 million years, like the giant, plant-eating sauropods, were still thriving.
Back then, Europe was a series of large islands.
On one of these, Hateg Island, a giant dinosaur showed a most surprising adjustment to island life.
Cut off from everywhere else, Hateg Island has its own unique collection of animals.
Bradycneme is one of the predators here.
Magyarosaurus, a plant-eater, is the potential prey.
And it's the youngest which are in greatest danger from predators.
Hateg is a island where much is not as it first appears.
This is a world turned upside down.
They may look like giants but the Magyarosaurus from Hateg Island actually stood no taller than a pony.
Weighing around one tonne, they are fraction of the size of their mainland relatives.
And weigh at least 70 times less than their cousin Argentinosaurus.
On the island of Hateg, there simply wasn't enough food to support a plant-eating giant.
So, over many tens of thousands of years, they adapted, creating a world were many of the dinosaurs were pocket-size versions of their relatives.
But some animals are still huge.
This is the largest flying vertebrate ever known.
A pterosaur with a ten-metre wingspan.
It's as tall as a giraffe, standing over five-and-a-half metres.
Discovered in 2002 .
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its skull alone is three metres long.
This is Hatzegopteryx.
A giant that we assumed hunted from the skies.
That was until the discovery of a series of fossil footprints, unlike any found before.
The footprints were those of a giant pterosaur, and they showed that these creatures did not just fly, but could comfortably walk on all fours.
It seems these monsters actually hunt on the ground.
Hunting with impunity, Hatzegopteryx are the top predators.
SHORT SCREECH THEY SCREECH Able to fly from island to island, this is their kingdom.
Hateg island is one example of the strange paths evolution can take.
But all over the world, bizarre-shaped dinosaurs continually evolved throughout their long reign.
Perhaps the strangest of all dinosaurs is one particularly weird group, Therizinosaurs.
And the best example of these peculiar animals was announced in 2009.
The skeleton revealed the secrets of this strange creature that lived in New Mexico 92 million years ago.
These swamps are home to zuni-tyrannus, a mid-sized tyrannosaur.
GROWLING And they're also home to this weird creature, Nothronychus.
It's actually a close relative of the tyrannosaur, but with one major difference.
Nothronychus has given up eating meat.
Here, the tyrannosaur is the top predator.
GROWLING AND SNARLING Therizinosaurs had been a mystery for decades, known only from tantalising fragments.
That all changed with the discovery of Nothronychus.
It gave us our clearest look at this strange group of dinosaurs.
It walked upright on short, stocky legs.
It had wide hips, and a long neck.
Its teeth showed that these weren't the teeth of a killer.
Far from its ferocious tyrannosaur cousins, this pot-bellied dinosaur had evolved into a strict vegetarian.
But armed with viciously long claws on its forearms, it was by no means defenceless.
GRUNTING AND GROWLING By becoming a plant eater, Nothronychus has easy access to food.
And because it walks on two legs, it can use its claws to pull down branches to reach leaves.
Nothronychus thrives here because it doesn't compete with the tyrannosaurs for food.
GROWLING But just because you're not competing for food doesn't mean you're not seen AS food.
These are dangerous places to be at the bottom of the food chain.
Unable to run, Nothronychus relies on brute strength.
GROWLING AND SNARLING Tyrannosaurs are predators that will eat anything, even one of their own, whether they've killed it or not.
And a discovery found in Montana of a number of meat-eating dinosaurs appeared to show that being such an unfussy eater could have dramatic consequences.
It seems scavenging can hold hidden dangers.
This tyrannosaur wasn't killed by Nothronychus.
There's a more deadly killer at work here.
All the predator's bones were found alongside the edge of an ancient stagnant lake.
And all of them died at the same time.
Similar mass killings have been found today among birds.
And the killer - a fast-acting, naturally occurring deadly disease.
Botulism.
Botulism is caused by bacteria that can thrive in rotting carcasses.
We think that the dinosaurs too might have been victims of this lethal and invisible killer.
Once a carcass is poisoned, it is quickly passed on to any animal that eats it.
With lethal results.
But plant-eaters, like Nothronychus, are usually safe from such deadly killers.
By completely changing its diet, Nothronychus shows the extraordinary adaptability of the group known as the theropod dinosaurs.
These two-legged dinosaurs were the most diverse of all the dinosaur groups.
From predators like Mapusaurus and Majungasaurus to the bizarre Therizinosaurs .
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the extraordinary tree-living Microraptor, to the weird Gigantoraptor.
They evolved into an incredible range of shapes and sizes.
The tyrannosaurs were the most successful of the theropod predators.
And once tyrannosaurs dominated in an area, many other meat-eating dinosaurs simply disappeared.
But those that had changed their diets flourished.
Mongolia, 85 millions years ago.
One group of dinosaurs thrives here despite the fact that they live in the shadow of a deadly tyrannosaur.
These are Oviraptorids, omnivores that eat animals and plants, and so don't compete directly for food with the biggest of killers.
And the benefits are clear, because some of these creatures become huge, like the eight-metre Gigantoraptor.
But this group have another trick to help them survive, the way they nest.
In Mongolia in 1994, a nest of very large dinosaur eggs was discovered.
An array of more than 20 eggs arranged in pairs around the edge of a shallow pit.
They were the biggest dinosaur eggs ever found.
When an embryo was found preserved within an egg, it proved that the nest, eggs and embryo were almost certainly those of Gigantoraptor.
But nesting makes an animal vulnerable.
Alectrosaurus.
But against a pair of Gigantoraptors, a five-metre tyrannosaur has little chance of success.
As Mongolia has given up it secrets, we have learnt more and more about these extraordinary creatures.
In 2005, one particular fossil was found to contain two eggs within its body cavity, ready to be laid.
Even more amazing were a number of other finds that revealed the nesting behaviour of these dinosaurs.
Three dinosaurs were discovered, all sitting on top of nests of eggs - the dinosaurs sitting in the centre of the nest with their long arms spread out to protect the pairs of eggs arranged around them.
These dinosaurs were brooding.
Looking after their eggs increases the chance of them hatching.
And having large eggs means the hatchling is more developed, making it less vulnerable to predators.
But it takes longer to hatch - up to 80 days for Gigantoraptor.
A time when both egg and the brooding parent are permanently at risk.
Smaller Oviraptors are no more than a nuisance.
Larger predators are a different story.
Unwilling to leave the nest, the adult protects its offspring, first, by hiding .
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and if that fails, it goes on the offensive.
Protecting the nest means Gigantoraptors' young are more likely to survive.
It now seems clear that the instinct to nurture and care for a nest of eggs had its origins with the dinosaurs.
It's a behaviour that was so successful, it's still widespread today with birds.
But the fossils show something else.
These animals all died sitting on their nests.
It seems that the threats don't always come from predators.
Sometimes the real danger comes from the most unlikely places.
These dinosaurs were all buried alive.
Planet Dinosaur was an incredibly diverse and varied place, with these creatures able to colonise every continent on Earth.
Continually evolving and changing, their dominance of life on Earth was absolute.
Yet, they were doomed.
Their downfall was caused by an asteroid smashing into the Earth.
Travelling 20 times faster than a speeding bullet, 15 kilometres across, it slammed into The Gulf of Mexico.
The impact released more energy than a billion atomic bombs.
The initial impact triggered wild fires, massive earthquakes and tsunamis.
But most devastating was the debris blasted high into the atmosphere.
This shrouded the planet in a cloak of darkness that lasted for months, cutting off sunlight.
The Earth was thrown into almost permanent night.
Animals that survived the blast were now faced with their greatest ordeal, as a devastating chain of events was set in motion.
Deprived of light, many plants died.
Plant-eaters like this Magyarosaurus are the first to be affected.
With no food, the biggest succumb first.
Fresh growth of plants offers a glimmer of hope, allowing smaller plant-eaters to scratch out a living.
But these aren't enough to sustain anything for long.
Scavengers initially have an easier time of it.
As the plant-eaters succumb to starvation, there is a glut of food.
But this surplus is an illusion.
Once gone, scavengers will starve, too.
The impact resulted in the collapse of whole food chains, and the extinction didn't just affect dinosaurs.
Virtually all life on Earth was affected.
More than 60% of all species were wiped out.
Yet the extinction wasn't a lottery.
One factor more than any other determined the dinosaur's fate.
Size.
On land, no animal weighing more than 25 kilograms survived.
There just isn't enough food to sustain large animals.
Ironically, it's the very thing that make dinosaurs so iconic that condemns them to extinction.
The finds and discoveries of recent years have painted a staggering picture.
Dinosaurs were incredibly adaptable, with an astonishing capacity for survival.
Enduring the break-up of continents, sea-level rises and countless changes in climate, they continued to diversify and thrive.
On land, in water, among the trees and even in the skies.
They conquered every continent, dominating life on Earth for more than 150 million years.
The most successful animals the world has ever known.
It was only with an unprecedented extraterrestrial impact that finally saw the end of Planet Dinosaur.