BBC Yellowstone (2009) s01e03 Episode Script
Autumn
NARRATOR: Yellowstone, volcanic wonderland.
Two million acres of wild space right in the heart of North America.
The heat of the summer has unveiled the full extent of the Yellowstone wilderness and, for a few precious months, it has blossomed.
But, now, Yellowstone is changing.
In just a few weeks, the snow and ice of winter will be back.
(BUGLING) As the animals of Yellowstone now turn to face perhaps the biggest challenges of their year, the true value of the world's first national park is about to become clearer than ever.
It's late August and on Yellowstone's peaks there is already a dusting of fresh snow.
Now, a new sound marks the new season.
(BUGLING) Fuelled by testosterone, the bugle call of this male elk is a boast of his strength.
(SHRILL BUGLING) All over Yellowstone, male elk are challenging each other for dominance.
(BUGLING) The sound of Yellowstone's autumn.
(SHRILL BUGLING) They are trying to win the admiration of females and gather them into a harem.
Only then do they stand a chance at mating with them before winter.
But the females are not yet in season, so they are not really that interested.
And, for now, they have a more practical concern.
Winter will soon be here.
They are eager to head down to lower ground before the snow comes in earnest.
Some will move down into nearby valleys, whilst others will journey much further, even beyond the boundaries of Yellowstone itself.
Yellowstone is deep in the Rocky Mountains of North America, an isolated high plateau defended by rugged peaks.
In the middle is the National Park.
The park and the surrounding mountains form one of the most important and spectacular wilderness areas on Earth.
In just two months, this great plateau will become a deep freeze once more.
Before then, the animals of Yellowstone will have to get ready or get out.
But, for now, below the snow-dusted peaks, summer still lingers in the heart of Yellowstone.
(GRUNTING) The sun has revitalised this place and, now, there are more living things here than at any time of the year.
The summer has brought visitors too, who are enjoying Yellowstone at its most vibrant.
As the sun now starts to get lower in the sky, the rich colours make this one of the best times to see the geysers.
On the grasslands, the good times are already over.
These bison are making the most of the grazing, but it is now dry and parched.
From now on, they will have to rely heavily on stored fat to keep them going, as these meadows become covered in more than four feet of snow.
Others are already thinking of leaving.
Pronghorn evolved to outrun a now-extinct North American cheetah and, so, are the fastest antelope on Earth.
But, unlike bison, their lightweight bodies can't store enough energy to keep them here through the winter.
So, now they must head out.
Their journey will be the longest of all.
But as many are preparing to get out, some have no choice but to stay.
In the remote north east of the Yellowstone wilderness are the Beartooth Mountains.
Here, surviving above 8,000 feet, a tree now welcomes the change of season, the whitebark pine.
All summer, these trees have been soaking up the energy of the Sun preparing for this moment.
Now, they offer the animals of Yellowstone a bumper crop of pine cones.
The whitebark pine is gambling on the fact that animals now need all the food they can get before winter, and is hoping it can entice them to spread its seeds far and wide across Yellowstone.
So, inside the cones, it has put tasty, nutritious pine nuts.
A pine squirrel.
It snacks on a few of the nuts to keep going and then buries them, one by one, in a sheltered hollow beside the tree.
If it hides them well and packs them carefully, they should last through the winter.
But this is not much good for the tree.
Its seeds have gone nowhere.
A grizzly bear mother and cubs.
It's unusual for a grizzly to have so many cubs.
This mother has found two orphans and adopted them.
But now she has four cubs to fatten up before they go into the den to hibernate this winter.
She's after pine nuts, too.
They are 50% fat.
In a good year, a grizzly bear can put on five pounds a day eating nuts alone.
If squirrels have done the hard work, it doesn't matter that grizzlies can't climb trees.
(SQUEAKS) The squirrel will just have to start again.
Luckily, this year, the trees are being particularly generous.
A Clark's Nutcracker.
This is what the tree has been waiting for.
With its perfectly-shaped beak, it prises the nuts from the cones and tucks them one by one into a special pouch under its tongue, up to 1 50 at a time, a fifth of its entire body weight.
Then it flies as much as 1 5 miles away and drills the nuts into the ground in sets of 1 0, placing a stone on top of the stash to mark the site.
It goes back for more and more.
Over the autumn, a single bird can bury 30,000 nuts across an area of 1 00 square miles.
When the winter comes, it will manage to remember the location of a staggering 70% of these seeds, even when hidden beneath the snow.
But as the Clark's Nutcracker remembers its way into surviving the winter, it becomes the whitebark's greatest ally.
Although its feat of memory is extraordinary, for every 1,000 seeds it buries, it still forgets 300.
From all those missed seeds carried far and wide across Yellowstone, new whitebark pines will germinate next spring.
It's now September and the elk have made their way down to graze where the grass on the river banks is still green and they can browse the nutritious shoots of young willow trees.
The males are now upping their game.
This bull urinates on himself to increase his masculine appeal and by thrashing his antlers to decorate them, he hopes to make himself look more impressive.
(ELK BUGLING) The females are paying a little more attention now.
(SHRILL BUGLING) The bull has succeeded in gathering a fair-sized harem.
(SQUEALING) But the females are still not quite ready to mate.
They are now focused on feeding as much as they can before moving lower still.
But the elk are being watched.
(WOLF hOWLING) Over the summer, wolves have been less mobile because of their young pups but their strength is building again.
The elk get twitchy and head for the cover of trees.
They may be a little safer here but the food in the forest is far less nutritious than on the river banks.
If they want to eat well and avoid wolves this winter, they'll need to keep on moving.
(BARKING) As the elk move gradually downwards, they follow the rivers out of Yellowstone's central plateau.
The rivers, in turn, follow the path of glaciers that flowed from this great bowl in the last ice age and carved their way right through the barrier of surrounding mountains.
Today, these valleys are escape routes for animals from the returning ice of winter.
Lower down, the valleys broaden, the rivers slow and a richer variety of trees grows in the alluvial soils, the perfect home for Yellowstone's most industrious creature.
(SPLINTERING AND CRACKING) A beaver can fell a cottonwood tree in just a few hours, hundreds in a year.
The beaver doesn't chew through the whole trunk, just enough to make the tree unstable.
It then retreats and lets the wind do the rest.
(CREAKING) (WIND BLOWING) It cuts branches into more manageable lengths and then swims them down a network of purpose-built canals towards the dam.
The pond gives this beaver protection from predators and the canals allow it to forage far into the forest, carrying many times its own weight with ease.
Autumn is the busiest time of year for beavers.
It won't be so easy to make repairs when the pond is frozen over.
The sound of running water is their stimulus to shore up gaps with timber and plug leaks with mud.
But the dam not only serves the beavers.
Moose come here from the forests around to feed on weeds that thrive in the beaver's shallow pond.
The weed is rich in vital sodium that the forest can't easily provide.
But now that winter is approaching, another essential role for the dam is revealed.
These smaller branches are not for fixing the dam, they're for eating.
The beaver secures them to the mud in the lake bottom.
In just a few weeks, this lake will be frozen and the beavers won't be able to cut and move trees.
But they will be able to swim right under the ice to feed from this underwater larder.
Moose also eat twigs and branches and often try to take advantage of the beaver's hard labour.
This young male is getting a little too close to the beaver's larder.
Autumn is not a time for sharing.
(OWLS hOOTING) It's mid-September.
As the sun drops further in the sky, the aspens, cottonwoods and maples start shutting down for the winter.
They now digest the green pigments in their leaves to claw back what nutrients they can into the trunk and roots.
What's left behind make the colours of autumn.
Groves of aspen all turn at the same time.
Each grove descended from one tree, interconnected by roots, colour-coordinated.
As cold air sinks further down from the mountains, it brings autumn mist to Yellowstone's valleys.
It was in the autumn of 1 870 that the first official exploration party to Yellowstone began to plan for the creation of the world's first national park, the beauty of Yellowstone's autumn inspiring a complete change in the way we value the wild.
(BUGLING) For the last six weeks of strutting and herding, male elk have eaten almost nothing.
They are exhausted.
This bull has done well.
He has successfully held on to his harem.
And now the females are finally coming into season.
But they are being distracted by another male.
(SHRILL BUGLING) If a bull elk can't dominate all rivals, he can't have access to the females and all his effort will have been in vain.
Now he must gather the last of his strength.
The rival wants to take him on.
The aim is to get an antler point into his neck.
But they are evenly matched.
Neither can penetrate the other's guard.
Now it's all about power.
A well-aimed thrust or a broken neck will kill.
This challenger is lucky to get off with just a parting stab in the rump.
(SHRILL BUGLING) The victor returns to his females.
His young will be born next spring.
(SQUEALING) But the prospects are not so good for a defeated bull.
After all this effort, he will now have to wait until next autumn to try his luck again.
That's if he even makes it.
Bull elk, exhausted by the rut, struggle to survive the Yellowstone winter.
It's now October and the winter is catching up with the elk once more.
An early flurry of snow is a sign that it's time to make a decision.
To stay is to face the certainty of snow and wolves.
To go offers the chance of an easier life, but the uncertainty of the world beyond Yellowstone.
(BUGLING) Every autumn, thousands of elk do leave Yellowstone.
And, as they go, they cross an invisible line out of the protection of the National Park.
Here they confront new danger.
Dressed in orange to avoid each other, but a colour that elk can't see, hunters come to the forests just around Yellowstone in October to shoot elk.
(GUNShOT) (ELK BLEATING) Elk, of course, have no understanding of park boundaries or of Yellowstone.
To them, this is simply an instinctive migration to find more hospitable land, so they just keep going.
Beyond the ring of hunting lands, the natural mosaic of forest and grass is replaced by an alien geometry.
Circles of irrigated grass, squares of maize, golf courses, the signature patterns of mankind.
It's unlikely they'll be welcome here.
By now, the pronghorn have pushed further than any of the Yellowstone's animals.
Out of forests, through farmland and down into the wide prairies at the foot of the Rocky Mountains themselves.
Their search for winter grazing takes them over 1 00 miles to the south of Yellowstone, the longest migration of any American mammal.
They have made this journey every year since the last ice age.
But, nowadays, they have a problem.
(TRUCK hONKING) Their traditional winter refuges lie right above some of the richest natural gas deposits in America.
The wells are no direct threat to pronghorn.
But pronghorn are timid.
(TRUCK hONKING) At the slightest noise they run and when they run, they run at 60 miles per hour.
They evolved to avoid cheetahs, not juggernauts.
Trucks, fences and the disturbance from the wells have put pronghorn at risk.
There are 1.
2 million acres here, but 75% of it has now been earmarked for gas and oil.
Back in the farmland, the elk have found food.
But this grass is not meant for them.
(COWS LOWING) Ranchers will tolerate elk as long as they don't compete too much with their cattle.
But, as the elk move in, their old enemy follows them out of Yellowstone, an animal that's more difficult for ranchers to accept.
In their minds, fear of the wolf runs deep.
Even Yellowstone lost its wolves.
They were wiped out over 80 years ago.
After years of prejudice, they were reintroduced in 1 995, brought back by the authorities to restore Yellowstone's natural balance.
But the wolves have done so well, that now they are moving out of the park looking for new territories and prey.
Out here, it's clearer to see why wolves have a bad reputation.
If ranchers' cattle are at risk, by law, wolves can be shot.
As wolves come back, ranchers are being forced to return to the old ways, to get back into the saddle and protect their herds.
(BEEPING) (BEEPING RISES IN PITCh) But opinion is changing.
Working with scientists who have radio-collared the Yellowstone wolves, ranchers can now keep track of them and when they know they are near, shoot not to kill but to scare them away.
(CATTLE LOWING) The return of the wolf will always be controversial.
But evidence is now emerging that wolves are far more important than anyone imagined, especially back in the heart of Yellowstone.
It's nearly the end of October.
The cold autumn nights have brought a thin crust of ice to a beaver's pond.
Unlike in the river valleys below, up here, there are not many tall cottonwood trees.
So this beaver has built his dam from the shoots of young willows sprouting all along the side of his pond.
But he is something of a novelty.
Even by the time Yellowstone was made a national park, beavers had been virtually hunted to extinction by fur trappers.
They only began to reappear here in 1 995, the year the wolves came back.
Now wolves are chasing elk again, elk have had less time to eat willows, so willows are sprouting everywhere.
Today, as winter approaches, all over Yellowstone beavers are using those willows to put the finishing touches to a dam-building renaissance.
And for every dam, there is a new habitat for new life and a richer, more diverse Yellowstone.
(hONKING) But just as Yellowstone reveals the complexity of life, it also exposes its fragility.
On its lofty ridges, there are signs that all is not well with the whitebark pine.
From above, it looks like autumn colours have come to an evergreen world.
But these trees are dying.
Small eruptions of resin dot the trunk of the tree, evidence of an invasion.
Tiny beetles are chewing through the tree's outer defences.
Once inside, they lay eggs that turn into larvae that eat the tree.
Each tree that is lost threatens all the animals that rely on its autumn bounty.
The only thing that can stop the beetles is extreme cold.
But, recently, the climate here has been getting warmer and warmer.
No national park can protect against that.
This is a tree that needs a cold winter.
It's now November and the elk have found their feeding grounds just in time, the snows of winter at their heels.
Here they join other herds who come to this place every year, where the snow will be less deep and life a little easier.
But, today, they graze on an island of grass surrounded by development.
As they run from the winter, the fate of Yellowstone's animals outside the national park is decided not by the cold, but by people.
(SQUAWKING) These elk are lucky.
This refuge has been kept aside to give them some degree of sanctuary.
So, although the park isn't big enough to protect all its animals all the time, its influence can spread beyond its boundaries and if even ranchers can come to tolerate wolves, then anything is possible.
In the mountains of Yellowstone, where the elks' bugles signalled the beginning of autumn just two months ago, all seems deserted.
But, now, the final act of the season is about to take place.
From out of apparently nowhere, come the bighorn sheep.
The toughest of all Yellowstone's animals, they can stay here all winter on slopes and crags that the biting wind keeps clear of snow.
Now they are coming together to rut.
Like elk, the males battle for females.
But where elk do their best to avoid fights, bighorn relish them.
A quick test of horn size and of other important bits of anatomy, and the males get straight to the point of sorting out who is toughest.
As the sound of their battles echoes across the Yellowstone wilderness, it marks the end of autumn.
Now the great change is coming again.
Winter is here.
As the snow returns to Yellowstone, it seems like the clock is turning back.
All traces of the human world are covered up.
A reminder that when the heart of this great wilderness was made a national park, nearly 1 40 years ago, it was one of the most remote places on Earth.
But as the human world has crept up on Yellowstone, the true value of this remarkable space has become ever clearer.
Though, in many ways, Yellowstone is not big enough, its influence reaches far beyond its boundaries.
Not just to the land around, but wherever there is a wilderness preserved for its own sake.
Here, in the heart of America, the first national park was born.
An idea that has led the way in redefining our relationship with the wild all over the world.
Some say America's best idea.
Bringing Yellowstone's unique natural beauty to the screen would have been impossible without the tireless help of the local experts that know it like the back of their hand.
Each has their own story to tell.
howdy.
My name's Mike Kasic.
I'm the sound recordist for the Yellowstone programmes.
I live in Livingston, Montana, just north of the Yellowstone National Park, right by the Yellowstone River.
MIKE: Being a sound recordist isn't the only thing that I do.
My friends say that I'm half fish.
Yeah, he's half fish.
MIKE: I like to spend my day swimming in the Yellowstone River.
I just let the current take me.
And, sometimes, when I want to stop I catch an eddy,just like the fish.
This is the Yellowstone River.
This is the same river that flows out of the heart of Yellowstone past geysers and bison, to just outside my door.
This is heavy traffic.
Sometimes I have to share the water.
Brrr! This is the heart of the wild.
A lifeblood that courses through wilderness and ends in the prairie.
Not a single dam holds back its waters.
It is the longest free-flowing river around.
It's what many rivers long to be, unstoppable.
This is the West as it was meant to be.
One of the reasons I love to do this is because beneath the waves swims a creature that I've grown fond of.
The Yellowstone cutthroat trout.
They just have aura about them.
With big red slits under their jaws, they are simply unmistakable.
The Yellowstone cutthroat trout is the soul of this river.
It's been here for thousands of years.
They're a wild animal.
They're in an underwater wilderness that is spectacular and amazing and I think it's the best part of Yellowstone.
I know it's a little quirky.
But looking for fish is what I like to do.
When I'm in the river, I see the world from a fish's point of view.
When they look up, what they're looking for is food.
This is the Mother's Day caddis fly hatch.
Trout food.
This is another of the Yellowstone's amazing events.
I'm swimming along and there's not a fly to be seen.
And, suddenly, there's millions.
A few hours later, it's back to nothing.
Caddis flies are not the only food in this river.
Many animals need the cutthroat trout to survive.
Ospreys, grizzly bears, otters, the list goes on.
But the more I see this world like the cutthroat sees it, the more I see that things are not quite right.
Long ago, the U.
S.
Fish Commission wanted more fish in Yellowstone for sport fishing.
So they stocked 3 1 0 million fish from Scotland and the Great Lakes.
And one of the fish they chose was the lake trout.
The trouble with lake trout is they like to eat cutthroat.
In fact, 80-90% of their diet is cutthroat trout.
I'm not sure how cutthroats like these stand a chance.
The cutthroat are up against a lot of things besides lake trout.
Warming river temperatures, pollution, industrial development and if they can survive all these things, will they then survive being gobbled up by lake trout? This is Yellowstone Lake.
It's nearly 2,200 metres.
Right here is Carrington Island, which is the primary spawning grounds for the lake trout.
And it's the kind of site of the big battle that the biologists and the National Park Service have going against these fish.
So, this is the National Park Service boat.
It's a drift gillnet boat.
And they are out here gilling, fishing for lake trout.
By the end of the season, they'll have taken about 350,000 lake trout out of Yellowstone Lake.
It's hard to see so many fish die, but watching a species disappear would be even harder.
They caught this fish before she had time to spawn this year.
They're getting many more fish every year.
So they're making progress, but they haven't won the war by any means.
But now the cutthroat trout are spawning, one of the natural world's most fantastic spectacles.
These fish swim up this creek every year to spawn and it is here, in their native gravel, that more fish will begin the cycle again.
With that, there's hope.
There's hope that, against all odds, these fish will survive.
In 1,000 years, I hope the cutthroat trout will swim these waters.
The river is more than just its water.
The Yellowstone is a river flowing fast and free like no other.
A wilderness under water.
I need this kind of wilderness.
I need it for my heart to beat right.
Take it away, I think we all lose the ability to understand the world.
The secret to swimming in the river is to let go.
Let the river take you, wherever that may be.
I think that is a lesson we could all learn from.
I guess, for now, I just feel lucky that I've had the chance to swim in a wild river with the Yellowstone cutthroat trout.
Two million acres of wild space right in the heart of North America.
The heat of the summer has unveiled the full extent of the Yellowstone wilderness and, for a few precious months, it has blossomed.
But, now, Yellowstone is changing.
In just a few weeks, the snow and ice of winter will be back.
(BUGLING) As the animals of Yellowstone now turn to face perhaps the biggest challenges of their year, the true value of the world's first national park is about to become clearer than ever.
It's late August and on Yellowstone's peaks there is already a dusting of fresh snow.
Now, a new sound marks the new season.
(BUGLING) Fuelled by testosterone, the bugle call of this male elk is a boast of his strength.
(SHRILL BUGLING) All over Yellowstone, male elk are challenging each other for dominance.
(BUGLING) The sound of Yellowstone's autumn.
(SHRILL BUGLING) They are trying to win the admiration of females and gather them into a harem.
Only then do they stand a chance at mating with them before winter.
But the females are not yet in season, so they are not really that interested.
And, for now, they have a more practical concern.
Winter will soon be here.
They are eager to head down to lower ground before the snow comes in earnest.
Some will move down into nearby valleys, whilst others will journey much further, even beyond the boundaries of Yellowstone itself.
Yellowstone is deep in the Rocky Mountains of North America, an isolated high plateau defended by rugged peaks.
In the middle is the National Park.
The park and the surrounding mountains form one of the most important and spectacular wilderness areas on Earth.
In just two months, this great plateau will become a deep freeze once more.
Before then, the animals of Yellowstone will have to get ready or get out.
But, for now, below the snow-dusted peaks, summer still lingers in the heart of Yellowstone.
(GRUNTING) The sun has revitalised this place and, now, there are more living things here than at any time of the year.
The summer has brought visitors too, who are enjoying Yellowstone at its most vibrant.
As the sun now starts to get lower in the sky, the rich colours make this one of the best times to see the geysers.
On the grasslands, the good times are already over.
These bison are making the most of the grazing, but it is now dry and parched.
From now on, they will have to rely heavily on stored fat to keep them going, as these meadows become covered in more than four feet of snow.
Others are already thinking of leaving.
Pronghorn evolved to outrun a now-extinct North American cheetah and, so, are the fastest antelope on Earth.
But, unlike bison, their lightweight bodies can't store enough energy to keep them here through the winter.
So, now they must head out.
Their journey will be the longest of all.
But as many are preparing to get out, some have no choice but to stay.
In the remote north east of the Yellowstone wilderness are the Beartooth Mountains.
Here, surviving above 8,000 feet, a tree now welcomes the change of season, the whitebark pine.
All summer, these trees have been soaking up the energy of the Sun preparing for this moment.
Now, they offer the animals of Yellowstone a bumper crop of pine cones.
The whitebark pine is gambling on the fact that animals now need all the food they can get before winter, and is hoping it can entice them to spread its seeds far and wide across Yellowstone.
So, inside the cones, it has put tasty, nutritious pine nuts.
A pine squirrel.
It snacks on a few of the nuts to keep going and then buries them, one by one, in a sheltered hollow beside the tree.
If it hides them well and packs them carefully, they should last through the winter.
But this is not much good for the tree.
Its seeds have gone nowhere.
A grizzly bear mother and cubs.
It's unusual for a grizzly to have so many cubs.
This mother has found two orphans and adopted them.
But now she has four cubs to fatten up before they go into the den to hibernate this winter.
She's after pine nuts, too.
They are 50% fat.
In a good year, a grizzly bear can put on five pounds a day eating nuts alone.
If squirrels have done the hard work, it doesn't matter that grizzlies can't climb trees.
(SQUEAKS) The squirrel will just have to start again.
Luckily, this year, the trees are being particularly generous.
A Clark's Nutcracker.
This is what the tree has been waiting for.
With its perfectly-shaped beak, it prises the nuts from the cones and tucks them one by one into a special pouch under its tongue, up to 1 50 at a time, a fifth of its entire body weight.
Then it flies as much as 1 5 miles away and drills the nuts into the ground in sets of 1 0, placing a stone on top of the stash to mark the site.
It goes back for more and more.
Over the autumn, a single bird can bury 30,000 nuts across an area of 1 00 square miles.
When the winter comes, it will manage to remember the location of a staggering 70% of these seeds, even when hidden beneath the snow.
But as the Clark's Nutcracker remembers its way into surviving the winter, it becomes the whitebark's greatest ally.
Although its feat of memory is extraordinary, for every 1,000 seeds it buries, it still forgets 300.
From all those missed seeds carried far and wide across Yellowstone, new whitebark pines will germinate next spring.
It's now September and the elk have made their way down to graze where the grass on the river banks is still green and they can browse the nutritious shoots of young willow trees.
The males are now upping their game.
This bull urinates on himself to increase his masculine appeal and by thrashing his antlers to decorate them, he hopes to make himself look more impressive.
(ELK BUGLING) The females are paying a little more attention now.
(SHRILL BUGLING) The bull has succeeded in gathering a fair-sized harem.
(SQUEALING) But the females are still not quite ready to mate.
They are now focused on feeding as much as they can before moving lower still.
But the elk are being watched.
(WOLF hOWLING) Over the summer, wolves have been less mobile because of their young pups but their strength is building again.
The elk get twitchy and head for the cover of trees.
They may be a little safer here but the food in the forest is far less nutritious than on the river banks.
If they want to eat well and avoid wolves this winter, they'll need to keep on moving.
(BARKING) As the elk move gradually downwards, they follow the rivers out of Yellowstone's central plateau.
The rivers, in turn, follow the path of glaciers that flowed from this great bowl in the last ice age and carved their way right through the barrier of surrounding mountains.
Today, these valleys are escape routes for animals from the returning ice of winter.
Lower down, the valleys broaden, the rivers slow and a richer variety of trees grows in the alluvial soils, the perfect home for Yellowstone's most industrious creature.
(SPLINTERING AND CRACKING) A beaver can fell a cottonwood tree in just a few hours, hundreds in a year.
The beaver doesn't chew through the whole trunk, just enough to make the tree unstable.
It then retreats and lets the wind do the rest.
(CREAKING) (WIND BLOWING) It cuts branches into more manageable lengths and then swims them down a network of purpose-built canals towards the dam.
The pond gives this beaver protection from predators and the canals allow it to forage far into the forest, carrying many times its own weight with ease.
Autumn is the busiest time of year for beavers.
It won't be so easy to make repairs when the pond is frozen over.
The sound of running water is their stimulus to shore up gaps with timber and plug leaks with mud.
But the dam not only serves the beavers.
Moose come here from the forests around to feed on weeds that thrive in the beaver's shallow pond.
The weed is rich in vital sodium that the forest can't easily provide.
But now that winter is approaching, another essential role for the dam is revealed.
These smaller branches are not for fixing the dam, they're for eating.
The beaver secures them to the mud in the lake bottom.
In just a few weeks, this lake will be frozen and the beavers won't be able to cut and move trees.
But they will be able to swim right under the ice to feed from this underwater larder.
Moose also eat twigs and branches and often try to take advantage of the beaver's hard labour.
This young male is getting a little too close to the beaver's larder.
Autumn is not a time for sharing.
(OWLS hOOTING) It's mid-September.
As the sun drops further in the sky, the aspens, cottonwoods and maples start shutting down for the winter.
They now digest the green pigments in their leaves to claw back what nutrients they can into the trunk and roots.
What's left behind make the colours of autumn.
Groves of aspen all turn at the same time.
Each grove descended from one tree, interconnected by roots, colour-coordinated.
As cold air sinks further down from the mountains, it brings autumn mist to Yellowstone's valleys.
It was in the autumn of 1 870 that the first official exploration party to Yellowstone began to plan for the creation of the world's first national park, the beauty of Yellowstone's autumn inspiring a complete change in the way we value the wild.
(BUGLING) For the last six weeks of strutting and herding, male elk have eaten almost nothing.
They are exhausted.
This bull has done well.
He has successfully held on to his harem.
And now the females are finally coming into season.
But they are being distracted by another male.
(SHRILL BUGLING) If a bull elk can't dominate all rivals, he can't have access to the females and all his effort will have been in vain.
Now he must gather the last of his strength.
The rival wants to take him on.
The aim is to get an antler point into his neck.
But they are evenly matched.
Neither can penetrate the other's guard.
Now it's all about power.
A well-aimed thrust or a broken neck will kill.
This challenger is lucky to get off with just a parting stab in the rump.
(SHRILL BUGLING) The victor returns to his females.
His young will be born next spring.
(SQUEALING) But the prospects are not so good for a defeated bull.
After all this effort, he will now have to wait until next autumn to try his luck again.
That's if he even makes it.
Bull elk, exhausted by the rut, struggle to survive the Yellowstone winter.
It's now October and the winter is catching up with the elk once more.
An early flurry of snow is a sign that it's time to make a decision.
To stay is to face the certainty of snow and wolves.
To go offers the chance of an easier life, but the uncertainty of the world beyond Yellowstone.
(BUGLING) Every autumn, thousands of elk do leave Yellowstone.
And, as they go, they cross an invisible line out of the protection of the National Park.
Here they confront new danger.
Dressed in orange to avoid each other, but a colour that elk can't see, hunters come to the forests just around Yellowstone in October to shoot elk.
(GUNShOT) (ELK BLEATING) Elk, of course, have no understanding of park boundaries or of Yellowstone.
To them, this is simply an instinctive migration to find more hospitable land, so they just keep going.
Beyond the ring of hunting lands, the natural mosaic of forest and grass is replaced by an alien geometry.
Circles of irrigated grass, squares of maize, golf courses, the signature patterns of mankind.
It's unlikely they'll be welcome here.
By now, the pronghorn have pushed further than any of the Yellowstone's animals.
Out of forests, through farmland and down into the wide prairies at the foot of the Rocky Mountains themselves.
Their search for winter grazing takes them over 1 00 miles to the south of Yellowstone, the longest migration of any American mammal.
They have made this journey every year since the last ice age.
But, nowadays, they have a problem.
(TRUCK hONKING) Their traditional winter refuges lie right above some of the richest natural gas deposits in America.
The wells are no direct threat to pronghorn.
But pronghorn are timid.
(TRUCK hONKING) At the slightest noise they run and when they run, they run at 60 miles per hour.
They evolved to avoid cheetahs, not juggernauts.
Trucks, fences and the disturbance from the wells have put pronghorn at risk.
There are 1.
2 million acres here, but 75% of it has now been earmarked for gas and oil.
Back in the farmland, the elk have found food.
But this grass is not meant for them.
(COWS LOWING) Ranchers will tolerate elk as long as they don't compete too much with their cattle.
But, as the elk move in, their old enemy follows them out of Yellowstone, an animal that's more difficult for ranchers to accept.
In their minds, fear of the wolf runs deep.
Even Yellowstone lost its wolves.
They were wiped out over 80 years ago.
After years of prejudice, they were reintroduced in 1 995, brought back by the authorities to restore Yellowstone's natural balance.
But the wolves have done so well, that now they are moving out of the park looking for new territories and prey.
Out here, it's clearer to see why wolves have a bad reputation.
If ranchers' cattle are at risk, by law, wolves can be shot.
As wolves come back, ranchers are being forced to return to the old ways, to get back into the saddle and protect their herds.
(BEEPING) (BEEPING RISES IN PITCh) But opinion is changing.
Working with scientists who have radio-collared the Yellowstone wolves, ranchers can now keep track of them and when they know they are near, shoot not to kill but to scare them away.
(CATTLE LOWING) The return of the wolf will always be controversial.
But evidence is now emerging that wolves are far more important than anyone imagined, especially back in the heart of Yellowstone.
It's nearly the end of October.
The cold autumn nights have brought a thin crust of ice to a beaver's pond.
Unlike in the river valleys below, up here, there are not many tall cottonwood trees.
So this beaver has built his dam from the shoots of young willows sprouting all along the side of his pond.
But he is something of a novelty.
Even by the time Yellowstone was made a national park, beavers had been virtually hunted to extinction by fur trappers.
They only began to reappear here in 1 995, the year the wolves came back.
Now wolves are chasing elk again, elk have had less time to eat willows, so willows are sprouting everywhere.
Today, as winter approaches, all over Yellowstone beavers are using those willows to put the finishing touches to a dam-building renaissance.
And for every dam, there is a new habitat for new life and a richer, more diverse Yellowstone.
(hONKING) But just as Yellowstone reveals the complexity of life, it also exposes its fragility.
On its lofty ridges, there are signs that all is not well with the whitebark pine.
From above, it looks like autumn colours have come to an evergreen world.
But these trees are dying.
Small eruptions of resin dot the trunk of the tree, evidence of an invasion.
Tiny beetles are chewing through the tree's outer defences.
Once inside, they lay eggs that turn into larvae that eat the tree.
Each tree that is lost threatens all the animals that rely on its autumn bounty.
The only thing that can stop the beetles is extreme cold.
But, recently, the climate here has been getting warmer and warmer.
No national park can protect against that.
This is a tree that needs a cold winter.
It's now November and the elk have found their feeding grounds just in time, the snows of winter at their heels.
Here they join other herds who come to this place every year, where the snow will be less deep and life a little easier.
But, today, they graze on an island of grass surrounded by development.
As they run from the winter, the fate of Yellowstone's animals outside the national park is decided not by the cold, but by people.
(SQUAWKING) These elk are lucky.
This refuge has been kept aside to give them some degree of sanctuary.
So, although the park isn't big enough to protect all its animals all the time, its influence can spread beyond its boundaries and if even ranchers can come to tolerate wolves, then anything is possible.
In the mountains of Yellowstone, where the elks' bugles signalled the beginning of autumn just two months ago, all seems deserted.
But, now, the final act of the season is about to take place.
From out of apparently nowhere, come the bighorn sheep.
The toughest of all Yellowstone's animals, they can stay here all winter on slopes and crags that the biting wind keeps clear of snow.
Now they are coming together to rut.
Like elk, the males battle for females.
But where elk do their best to avoid fights, bighorn relish them.
A quick test of horn size and of other important bits of anatomy, and the males get straight to the point of sorting out who is toughest.
As the sound of their battles echoes across the Yellowstone wilderness, it marks the end of autumn.
Now the great change is coming again.
Winter is here.
As the snow returns to Yellowstone, it seems like the clock is turning back.
All traces of the human world are covered up.
A reminder that when the heart of this great wilderness was made a national park, nearly 1 40 years ago, it was one of the most remote places on Earth.
But as the human world has crept up on Yellowstone, the true value of this remarkable space has become ever clearer.
Though, in many ways, Yellowstone is not big enough, its influence reaches far beyond its boundaries.
Not just to the land around, but wherever there is a wilderness preserved for its own sake.
Here, in the heart of America, the first national park was born.
An idea that has led the way in redefining our relationship with the wild all over the world.
Some say America's best idea.
Bringing Yellowstone's unique natural beauty to the screen would have been impossible without the tireless help of the local experts that know it like the back of their hand.
Each has their own story to tell.
howdy.
My name's Mike Kasic.
I'm the sound recordist for the Yellowstone programmes.
I live in Livingston, Montana, just north of the Yellowstone National Park, right by the Yellowstone River.
MIKE: Being a sound recordist isn't the only thing that I do.
My friends say that I'm half fish.
Yeah, he's half fish.
MIKE: I like to spend my day swimming in the Yellowstone River.
I just let the current take me.
And, sometimes, when I want to stop I catch an eddy,just like the fish.
This is the Yellowstone River.
This is the same river that flows out of the heart of Yellowstone past geysers and bison, to just outside my door.
This is heavy traffic.
Sometimes I have to share the water.
Brrr! This is the heart of the wild.
A lifeblood that courses through wilderness and ends in the prairie.
Not a single dam holds back its waters.
It is the longest free-flowing river around.
It's what many rivers long to be, unstoppable.
This is the West as it was meant to be.
One of the reasons I love to do this is because beneath the waves swims a creature that I've grown fond of.
The Yellowstone cutthroat trout.
They just have aura about them.
With big red slits under their jaws, they are simply unmistakable.
The Yellowstone cutthroat trout is the soul of this river.
It's been here for thousands of years.
They're a wild animal.
They're in an underwater wilderness that is spectacular and amazing and I think it's the best part of Yellowstone.
I know it's a little quirky.
But looking for fish is what I like to do.
When I'm in the river, I see the world from a fish's point of view.
When they look up, what they're looking for is food.
This is the Mother's Day caddis fly hatch.
Trout food.
This is another of the Yellowstone's amazing events.
I'm swimming along and there's not a fly to be seen.
And, suddenly, there's millions.
A few hours later, it's back to nothing.
Caddis flies are not the only food in this river.
Many animals need the cutthroat trout to survive.
Ospreys, grizzly bears, otters, the list goes on.
But the more I see this world like the cutthroat sees it, the more I see that things are not quite right.
Long ago, the U.
S.
Fish Commission wanted more fish in Yellowstone for sport fishing.
So they stocked 3 1 0 million fish from Scotland and the Great Lakes.
And one of the fish they chose was the lake trout.
The trouble with lake trout is they like to eat cutthroat.
In fact, 80-90% of their diet is cutthroat trout.
I'm not sure how cutthroats like these stand a chance.
The cutthroat are up against a lot of things besides lake trout.
Warming river temperatures, pollution, industrial development and if they can survive all these things, will they then survive being gobbled up by lake trout? This is Yellowstone Lake.
It's nearly 2,200 metres.
Right here is Carrington Island, which is the primary spawning grounds for the lake trout.
And it's the kind of site of the big battle that the biologists and the National Park Service have going against these fish.
So, this is the National Park Service boat.
It's a drift gillnet boat.
And they are out here gilling, fishing for lake trout.
By the end of the season, they'll have taken about 350,000 lake trout out of Yellowstone Lake.
It's hard to see so many fish die, but watching a species disappear would be even harder.
They caught this fish before she had time to spawn this year.
They're getting many more fish every year.
So they're making progress, but they haven't won the war by any means.
But now the cutthroat trout are spawning, one of the natural world's most fantastic spectacles.
These fish swim up this creek every year to spawn and it is here, in their native gravel, that more fish will begin the cycle again.
With that, there's hope.
There's hope that, against all odds, these fish will survive.
In 1,000 years, I hope the cutthroat trout will swim these waters.
The river is more than just its water.
The Yellowstone is a river flowing fast and free like no other.
A wilderness under water.
I need this kind of wilderness.
I need it for my heart to beat right.
Take it away, I think we all lose the ability to understand the world.
The secret to swimming in the river is to let go.
Let the river take you, wherever that may be.
I think that is a lesson we could all learn from.
I guess, for now, I just feel lucky that I've had the chance to swim in a wild river with the Yellowstone cutthroat trout.