| This is a transcript of the Walking with Dinosaurs (1999) episode "Spirits of the Ice Forest". |
| Please do not edit this transcript unless you have a copy of the episode to transcribe from, or have spotted an obvious spelling mistake. |
NOTE: Applicable species names will be marked in italics.
Intro[]
Dawn over a silent forest a few hundred miles from the South Pole. It is the end of months of total darkness, and as the sun's rays filter down through the trees, they reveal a cold, harsh world. Here, there are polar dinosaurs, adapted to cope with extreme conditions, but even they struggle to stay alive.
This far south, the first day of spring lasts only a few minutes, but it triggers the start of an astonishing story of survival through the polar year.
Story[]
ANTARCTICA - 106,000,000 BC
It is the Mid-Cretaceous period, and dinosaurs are now more widespread than ever, reaching every part of the globe. But one place is a special challenge - the South Pole. Here, a giant continent made up of South America, Australia and Antarctica is kept warm by ocean currents that are forced down from the equator to encircle it.
Instead of ice caps, there are lush forests. But unlike the unchanging tropical climate elsewhere, Antarctica has seasons - from hot summers under midnight sun to cold winters of total darkness.
Leaellynasaura is a dinosaur that has adapted to this extreme climate.
Throughout the winter, they survive in the warm, sheltered heart of the thick forest, but now, in spring, they emerge to feed on the fresh plant growth.
They are just two metres long, and their most distinctve feature is their large eyes, which help them find food in the dark winter.
These dinosaurs are sociable little animals that live in small clans, enabling them to make the most of scarce resources. The clan is dominated by one breeding pair, and the hierarchy ensures that a Leaellynasaura is always on lookout duty. He regularly issues reassuring clicks, as long as the coast is clear.
The sentry has spotted a giant amphibian, Koolasuchus. He has massively powerful jaws, weighs about half a tonne, and is a carnivore.
In the water, Koolasuchus is lethal, but on land, his legs have trouble dragging his bulk around, and he is no threat to the lithe little dinosaurs. He has been hibernating over winter in the forest, and now faces what, for him, is an arduous journey of 200 metres to get back to the river where he will spend his summer.
This bizarre-looking creature is a relic from a time before dinosaurs. In most parts of the world, competition from crocodiles has driven these magnificent amphibians to extinction. But here, the waters get too cold for crocodiles, and the world's last Koolasuchus survive, still patrolling the waterways, just as their ancestors did 150 million years before them.
As spring takes hold and the days grow longer, the forest bursts into life.
Many of the plants in these unique conifer and fern forests have specially adapted to lie dormant during the dark of winter, and only with the spring light do they start to photosynthesise again.
For the clan, it is also a time of feverish activity. Having mated with the first spring sunrise, they are now building nests.
It is a team effort, with the dominant pair building in the centre and other subordinate animals working around them.
Many of these piles of leaves will never hold eggs, but act as decoys to help protect the main nest.
But no matter how busy these little dinosaurs are, they always have to remain alert to danger.
A Polar Allosaur - a summer visitor from warmer lands to the north.
He is a one-tonne ambush predator.
The allosaur is the largest and fiercest killer in the forest, but he was spotted early enough by the sentry. And as the clan melt into the undergrowth, he is no match for their speed and agility.
Spring across the polar forests brings the movement of many animals. In the sky, lines of pterosaurs head south for their summer roosts. And among the trees, there is the echo of unnfamiliar sounds. The largest of all the summer migrants is coming to the forest.
These unusual calls signal the arrival of huge herds of Muttaburrasaurus from the north. For the last two months, they have been migrating 800 kilometres down the coast of Australia, following the sun to the south. These dinosaurs move towards the pole every year to strip the lush vegetation and find secure sites to lay their eggs.
The herds have a major impact on the forest. Each massive adult weighs about 3 tonnes and can pluck food from branches several metres off the ground. While feeding, the dinosaurs keep in touch using their specially adapted noses to produce a range of trumpeting calls.
As the forest becomes more crowded, the clan's nests need constant attention. The lead female treats her pile of rotting leaves like an incubator, and uses her sensitive beak to monitor the temperature. Then she adds and removes vegetation to keep the eggs at about 30 degrees centigrade. Aready, the baby Leaellynasaura can be heard inside, responding to their mother's clicks.
The nests also have to be protected round the clock. Fur-coated mammals thrive in these Antarctic forests, and some are easily large enough to steal a dinosaur egg.
But the Leaellynasaura has an unusual defence.
It is enough to see off this egg thief, but the little dinosaur knows there will be others.
The Muttaburrasaurus continue to arrive on the flood plains, and are watched from the forest edges by hungry eyes.
The Allosaur is testing the herd, probing for sick or old animals. These herbivores are slow, but find safety in size and numbers.
The Allosaur is no match for a healthy bull Muttaburrasaurus, and he is forced to back down.
By late spring, the tree ferns and conifers are in full flush and have formed a thick canopy, soaking up every bit of sunlight.
Many of the nests have now fallen victim to predators, but the clan has ensured that at least the dominant pair's has survived. Secure within are three hatchlings. For the first two weeks of their lives, they will stay in the nest while the adults take turns collecting food and bringing it back to them.
The lead female takes great care to maintain the nest. To stop predators sniffing out her brood, she removes the old eggshells and eats the unhatched eggs. This also recycles the nutrients.
At this stage, the hatchlings are vulnerable and can easily become lost on the forest floor if they stray. All the adults watch out for wanderers, in case a predator moves in. Within weeks, this little hatchling will be strong enough to keep up with the adults, but for now, he is promptly returned to the safety of the nest.
It is now full summer and permanently light. The sun will not set for another five months. At this time of year, the forest floor around the nests comes alive with polar insects, like this Weta, out hunting for food among the leaf litter.
They themselves are food for larger animals, like the Tuatara. It is a reptile, but one surviving from a time long before the dinosaurs. it will remain long after them, too, clinging on in the land that will become the islands of New Zealand.
Out in the open, the Muttaburrasaurus herd is being tormented by bloodsuckers. Summer brings out swarms of biting flies, and although dinosaurs are covered in tough, scaly skin, they do have softer parts. The insects concentrate on areas like the inside of the ear, where their mouths can pierce the skin and suck out a meal.
These swarms can drive their gigantic hosts wild, and soon the herd has to move away from the river.
Inside the forest, the Leaellynasaura enjoy the summer bounty and, despite the dangers around them, sleep. During these long months of sun, they rely heavily on their patterned skin to camouflage them among the ferns.
Sleep is the last thing on the minds of the hatchlings that are playing nearby. They have grown and are now practising the sort of agile moves which may one day save their lives.
Wherever the young are, their mother is not far away, acting as lookout for her increasingly active brood.
On the banks of the river, an old Muttaburrasaurus has been brought down, and a male Allosaur feeds off the rotting flesh.
The Polar Allosaur is a smaller descendant of the great carnivores of the Jurassic, 50 million years before. His type are rare in the Cretaceous, but they survive here at the South Pole.
Although there is enough meat at this kill for 20 Allosaurs, it is unlikely the approach of a rival female will be tolerated.
She is driven away by the hungry male.
A fully-grown Polar Allosaur needs needs about 100 kilos of meat a week. She will have to come back once the male has eaten his fill.
Later, under the light of the midnight sun, one of the young Leaellynasaura ventures down to the river alone.
Saved by his lightning reactions.
But the young Leaellynasaura has much to learn about the dangers of his forest home.
In the time of dinosaurs, Antarctica suffers regular summer thunderstorms that sweep across the polar forest, causing widespread flooding.
These floods drive forest creatures together, and this can lead to confrontation.
The Leaellynasaura have spotted a rival clan, and it is enough to trigger an aggressive response. Each clan must defend its area of forest, so it does not face competition for food. It is crucial that the interlopers are put off by a convincing show of strength.
It has worked. The rivals retreat and, for the moment, the clan's territory is safe.
After the rains, the floodwaters quickly subside, and dinosaurs can return to the riverbanks to feed.
When there is plenty of food, herbivores can be very tolerant of each other. As the Muttaburrasaurus pluck and tear at the podocarp trees, the Leaellynasaura scamper among them, gathering up the red fruit that gets scattered on the ground.
Although a risky harvest, the clan must take every opportunity the forest offers, because time is running out.
The seasons draw on, and for the first time in four months, the sun sets. Autumn has arrived, and the forest prepares for a polar winter.
Up and down the river valleys, the Muttaburrasaurus sense the change, and begin their long trek north.
Occasionally, some of these giant migrants get lost in the forest. But what for them is a minor problem can mean life or death for the Leaellynasaura clan. The noise these huge herbivores make prevents the Leaellynasaura sentry from hearing other, more threatening sounds.
The giant carnivore has killed the dominant female.
It is a bitter blow.
Winter is coming, and without a lead female, there will be tension in the clan.
In the gathering gloom, the Koolasuchus senses the drop in temperature and reluctantly leaves his summer home.
Once again, he lumbers into the forest in search of a suitable shelter to hibernate through the cold, dark months that lie ahead.
The low light also triggers a change in the forest plants. They stop growing and photosynthesis grinds to a halt. Some will shed their leaves, others will just lie dormant.
The Leaellynasaura now have to work extra hard to find food, searching for fungus and nutritious roots beneath the forest floor.
At this time of year, their survival strategy is to move to the heart of the forest, where it rarely freezes and to keep active to maintain their body temperature. But as the clan gathers round a waterfall, it is clear the summer predators have taken their toll - only one hatchling has survived, and they still have no lead female.
Towards the end of autumn, the last day passes within a few minutes, and the long twilight begins.
Life in the polar forest faces its biggest killer - freezing temperatures.
Some polar creatures, like the weta, have learned to cope with the cold by allowing themselves to become frozen.
In the winter sky, the Southern Lights whip and flicker over the silent forest.
Under the sleeping trees, it is almost pitch-black, but with image-enhancement, it is possible to get a Leaellynasaura's-eye view of the clan.
The dinosaurs are still active, but this year the ground has frozen, and it has become almost impossible to scrape a living out of the soil.
Even pond water is frozen, and the Leaellynasaura resort to using their hard beaks.
Temperatures this low don't usually last long in the forest, but facing this harsh time with their strict social order in tatters means the fate of this clan hangs in the balance. They push deeper into the forest.
There has been no light for two months, and another cold snap forces the clan to take drastic action. They have evolved one further adaptation to the cold - as a group, they huddle together and drift into a state of torpor. In this suspended animation, their bodies can resist the effects of the cold, but they cannot stay like this for more than a couple of days.
The first hints of salvation are small. Under his rock, the weta is revived from his deep freeze by a slight, but sustained, rise in temperature.
On the horizon, the sun's rays grow stronger, and there is the promise of spring.
The forest silence is shattered by an agitated clan. Two males are fighting. This is the mating season for the Leaellynasaura, and the males are competing for dominance.
These fights are short, but can sometimes be vicious.
Having asserted his authority, the victorious male chooses a mate and, at last, the clan can start to re-establish round a dominant pair. Their annual struggle to survive can begin again.
Life at the poles is a remarkable evolutionary achievement for the dinosaurs. But eventually, a slight cooling in the world's climate will spell doom for these lush Antarctic forests, and without them, all these unique dinosaurs will also disappear.
Next Time...[]
Away from the poles, the dinosaurs continue to thrive for another 40 million years before extinction. In the final programme, we will see how, just before the end of their reign, they evolved the most terrifying predator that has ever walked the Earth.