THURMAN: It's your first day in the world, your first step into a vast and daunting landscape... ...full of possibilities... wonder... and peril.
[ Wind whistling ] You've just been born in the Rockies, an untamed wilderness in the heart of North America.
And you have much to learn.
Each new challenge will test your resolve.
Every new opportunity will hone your skills.
♪♪ You will need to grow up fast... ...if you hope to take on the Rockies' most formidable challenge... your very first winter.
♪♪ ♪♪ [ Wind whistling ] THURMAN: In the shadow of the Teton Range, summer is drawing to a close.
And one grizzly mother and her four chubby cubs are making their way across the valley.
It's remarkable for a mother grizzly to still have four healthy cubs this late in the season.
But she's no ordinary mother.
This is Grizzly 399, the matriarch of Grand Teton National Park.
Her cubs are playfully sparring with each other as they bound about.
But 399 is on a mission.
♪♪ Her family is in a state of hyperphagia, driven by the need to fatten up for winter.
♪♪ ♪♪ During this time, she can easily double her body weight.
♪♪ Her cubs will pack it on, as well.
♪♪ Even as they'll rely on mom's support for a few more years.
♪♪ She huffs to collect her cubs as she has done countless times in her life.
For 399 isn't just a mother, but a grandmother many times over.
And at the age of 24, she's one of the oldest living wild grizzlies we know of.
And among the oldest wild creatures to call the Rockies their home.
The Rocky Mountains stretch over 2,000 miles across North America.
Bringing together some of the most diverse and vital habitats on the continent.
And for every creature born in the Rockies, this next crucial step of growing up has its own speed and path, filled with the unexpected.
But one thing is for certain, in just a few weeks, these strangely wild sanctuaries... ...will be plunged back into winter once again.
♪♪ ♪♪ Across the Teton Range, sandhill cranes have already begun the long journey south, to their wintering grounds in New Mexico.
Riding thermals across high mountain passes, cranes make their way across Colorado's Rocky Mountains.
Here, the Rockies reach their zenith with 58 peaks above 14,000 feet, the tallest mountains in the entire stretch of the Rockies.
As the cranes continue south, a magical transformation is unfolding beneath them.
Green hillsides are turning gold as vibrant autumn colors wash across the Rockies like ocean waves.
♪♪ Trees are preparing for the trials of winter by entering a state of dormancy.
♪♪ ♪♪ And many animals are preparing for the scarcity of food that comes with winter.
Squirrels are plucking off the most promising pinecones before they've dropped their seeds to the forest floor.
They will cache as many cones as they can before snow covers the ground.
And while many are preparing for winter, bull elk have other things on their minds.
It's mating season in Rocky Mountain National Park.
Cows are preoccupied with their young and grazing before the snows comes.
[ Calling ] But our bull is intent on holding the reins tight on his harem of 20 or so cows.
[ Calling ] His bugle is a warning to other males, and it can be heard for miles around.
It's a vocal display of dominance meant to ward off rivals and attract mates.
There are plenty of other bulls out there, but so far, his strategy is working.
[ Calling ] This stretch of wilderness butts up to the city of Estes Park.
So males will compete on the golf course while cows graze on the putting greens.
[ Horns honking ] But keeping ahold of your harem is hardly that easy.
♪♪ While some animals learn to adapt to city life using stealth, for a thousand-pound bull elk, it's more about brawn.
[ Calling ] As the herd migrates through the city, he'll spend more time corralling them away from traffic... than from other males.
[ Horn honking ] [ Elk calling ] The bull has staked his claim to this intersection, and is trying hard to keep his harem in check.
[ Horns honking ] ♪♪ City dwellers everywhere understand the trade-offs of a lack of privacy.
But this group will stick through it together, all in the name of love.
Roughly 85% of Colorado's population lives along the Eastern edge of the Rocky Mountains, in some of the fastest growing cities in the nation.
With increasingly fragmented habitat, city parks have become the new home for some stealthy hunters.
[ Barking ] It may not be the most ideal place to make a living, but there is opportunity here.
Hunting is a skill honed over time, one-part instinct, two parts, experience.
But holding on to your dinner is just as important as the hunt itself.
And that's what makes growing up in the Rockies such a challenge It's all about learning what it takes to survive, and that's not just about catching your next meal.
It's about learning the rules of your tribe... ♪♪ ...finding a mate... and ultimately, successfully raising your young.
And as winter approaches, all of those lessons come more sharply into focus.
Childhood is a journey.
Sandhill cranes have finally arrived to Colorado's San Luis Valley.
Fields of wheat and barley have become an important source of food for the cranes, especially with an ever-dwindling wetlands.
This all you can eat buffet is the perfect time to socialize.
For young ones, it's an opportunity to practice your dance moves.
Sandhill cranes will spend years learning to dance before they're ready to choose a life-long partner.
But these days of plenty may not last.
Drought continues to plague the west.
And the fate of both cranes and farmers are linked.
All life here depends on the snowpack that accumulates in the high mountain peaks of the Southern Rockies.
But that snowpack is dwindling.
The sand dunes that lie at the base of the Sangre De Cristo Mountains are a stark reminder of a much wetter past.
Sand from ancient lakes that once covered the valley, now form the tallest sand dunes in North America.
Reaching over 740 feet above the desert floor.
♪♪ It's an ocean of sand, shaped by the forces of wind and water.
This is an environment of extremes.
Surface temperatures can reach 150 degrees in summer and minus-25 degrees on a winter's night.
♪♪ ♪♪ And here, at the base of the dunes, one tiny creature is just beginning his day.
It's a kangaroo rat.
Timid by nature, this nocturnal rodent hops like a kangaroo and has the appearance of a rat, but he is neither.
He is, however, uniquely adapted to desert life.
And this young kangaroo rat is hunting for seeds blown across the sand.
He's not eating the seeds, but rather storing them in his cheek pouches, and bringing them back to his burrow for safe keeping.
It's a complex burrow system with separate chambers for sleeping and others for storing food.
And this underground home is his castle, which he'll vigorously defend from any intruder.
♪♪ Our young kangaroo rat is back on the hunt for seed.
But his search takes him farther and farther from his home.
And while he's away, his curious neighbor, drawn by the smell of seeds, infiltrates his burrow.
Our young kangaroo rat finally returns from his foray.
He doesn't know it yet, but his neighbor is already inside.
♪♪ He springs into action... ...chasing the intruder out of his burrow and into the night.
It's the end of a long night for our kangaroo rat, but now he's safely tucked away inside his home.
As autumn comes to a close, the cranes begin the last leg of their journey.
They are following an ancient flight path to their wintering grounds in New Mexico.
Sandhill cranes are as much a part of the Rockies as the stones themselves.
Unearthly sandstone formations rise up from the rolling badlands of New Mexico.
The Navajo peoples call these pillars "De-Na-Zin", meaning "Standing Crane".
A natural monument to the North America's most ancient bird.
♪♪ ♪♪ In the Colorado Rockies, winter is getting a head start.
The first snow flurries of the season leave behind a dusting of snow.
And by sunrise, the dunes have been transformed.
♪♪ ♪♪ For bighorn sheep the end of autumn marks a turning point.
And for lambs, it's their first introduction to a hallmark event, a time when they begin to see what all this jockeying for position is really about.
It's rutting season, and males are competing for the right to mate.
Rank is constantly reinforced and often contested.
Their ultimate weapons are their curled horns that can weigh up to 30 pounds.
They are literal battering rams.
In spring, 2-week-old ram lambs will begin to butt heads in mock battles.
In the early development of a social order they will be part of for the rest of their lives.
Most of the year these rams live in bachelor groups that adhere to a ridged hierarchy largely determined by age and size.
Their life has a singular focus, and this is what they've been preparing for all year long.
A male can determine if a female is ready to mate, simply by smelling her urine.
He takes in her scent by tilting his head back so her pheromones can reach a sense organ in the roof of his mouth.
Females are in estrus for just 48 hours.
♪♪ And during this time, the rule book rams have lived by is thrown out the window.
A higher ranking male is guarding this female.
But he's up against a reckless youngster willing to risk it all.
♪♪ ♪♪ The lower ranking male knows he can't win in a head-to-head fight.
So his goal is to separate the female from the higher ranking male just long enough to mate.
In these early years, it may be his only chance.
♪♪ ♪♪ ♪♪ As the late autumn sun slowly begins to melt away the snow, things are becoming heated.
[ Horns crack ] For most young, it's the closest they've been to so many large males.
And for ram lambs, it's a window into their future.
[ Horns crack ] Rams are tuned into every movement on this mountainside.
[ Horns crack ] A distant clash of horns will draw males from a mile away.
[ Horns crack ] Half a dozen males are now in pursuit of this female, including the dominant ram.
With this many males bearing down on her, she makes a break for the one place that has always meant safety.
Here, she has the advantage.
But the rams are relentless, and weighing in at 300 pounds, dangerous.
So, she makes a break for the open field, in an attempt to shake them.
The males are following close behind, knocking each other off course as they try and gain ground.
The dominant ram tries to keep the others at bay while maintaining his lead.
But the competition is fierce.
She's exhausted and surrounded once again.
She makes one last attempt to flee, but this youngster seizes an opening.
♪♪ In the end, it is the higher ranking males that have the greatest success.
Her offspring, will likely be from him.
♪♪ ♪♪ ♪♪ The winter solstice marks the shortest day of the year and the official beginning of winter.
♪♪ ♪♪ But across most of the Northern Rockies, winter is well underway.
♪♪ ♪♪ A deep freeze has settled in, and it's here to stay.
[ Wind whistling ] The first big storm of the season is building over Yellowstone Valley.
Our bison herd is heading across their range, into the storm.
Bison, unlike cattle, face storms head on, knowing they will pass through it quicker.
But that doesn't make winter any less brutal.
The Rockies are clearly living up to their reputation.
It's our young calf's first winter, and he already seems out of his depth as he struggles to keep up with mom.
It's a serious time of year, and mom is completely focused on the task at hand, using her head like a plow to uncover grasses beneath the snow.
But the storm is making that task more difficult, burying the grasses the minute she's uncovered them.
She'll need every morsel she can dig up.
She's not only nursing the calf, but like many of the females in the herd, she's also pregnant.
The calf is learning, but he still lacks the broad head needed to plow snow, so he relies on the adults to help unearth grasses.
As difficult as his first winter may be, he is not alone and will rely on the strength of the herd to support him.
Others must endure winter on their own.
It's this young fox's first winter, and it's already proven to be a difficult one.
Foxes must grow up fast, from childhood to adulthood in the span of just six months.
♪♪ ♪♪ His winter coat will keep him warm enough in the storm, but it won't keep him fed.
Foxes use their ears to detect their prey under the snow.
But now, with the storm bearing down on him, that's become impossible.
♪♪ He seems unwilling to give up just yet.
But conditions are getting worse.
Every minute he spends stalking prey in the storm is energy spent.
It's a costly endeavor.
♪♪ Finally, the fox decides to give up the hunt.
♪♪ ♪♪ The morning only brings more snow, and now our herd is buried.
♪♪ [ Wind whistling ] December is among the coldest months in Yellowstone, with average temperatures lingering well below freezing.
Bison are built for the cold.
Their winter coat is so thick, snow accumulates on their back without melting away.
♪♪ Once the skies clear, temperatures plummet.
It's so cold that water vapor begins to crystalize in the air, creating a magical phenomenon known as Diamond Dust.
♪♪ ♪♪ ♪♪ As we enter the frigid depths of winter, the landscape appears eerily barren.
Most bears would have been denned up long ago, but in the shadow of the Tetons, one legend has yet to call it quits.
Grizzly 399 and her four chubby cubs are wading through the deep snow in the final days of December.
It's incredibly late in the season for any bear to still be out, especially a mother with four cubs.
♪♪ But if anyone was going to redefine what it means to be a grizzly, it would be 399.
She has beaten all the odds and charted her own path.
399 is the undisputed Queen of the Tetons.
And who, after all, would be foolish enough to question a Queen's decision.
♪♪ She pauses to take one last look over her domain.
Now she's ready.
399 makes her way up slope.
She's heading to her winter den.
Somewhere in the vastness of the Teton range.
♪♪ ♪♪ Farther north, in the depths of Yellowstone, our bison family has sought refuge from the storm among the thermal vents.
It's a welcome reprieve for the herd, especially our young bison.
These hot springs not only provide warmth, but less snow cover and easier forage.
An important bit of knowledge when you weigh in at 2,000 pounds and subsist almost entirely on grasses.
Little by little, he's absorbing an ancient reservoir of knowledge passed down from generation to generation.
For predators, winter brings opportunity.
[ Howling ] Coyotes evolved alongside wolves.
[ Howling ] And their canid cousin helped shaped them into the highly flexible predator we know today.
[ Crows cawing ] A pack of coyotes has discovered the remains of a bison carcass.
And they are picking the meat clean from the bones.
During these cold winter months, competition is fierce.
[ Screeching ] And any meal is meal worth defending.
[ Snarling ] [ Wind whistling ] But perhaps the deadliest predator of all is winter itself.
A casualty of the most recent storm has now become a feast for eagles.
[ Screeching ] While eagles may rule the carcass by day... ...the night belongs to other predators.
♪♪ ♪♪ A mountain lion has discovered the carcass.
And it's not just one... it's a family.
♪♪ [ Growling ] Mom settles down for a meal.
At about 6 years of age, she's in the prime of her life.
Her kittens are fully grown now and the same size as mom.
One of the kittens attempts to join her.
But mother is reluctant to share the carcass.
But, as always, persistence pays off.
This will likely be the kittens last winter travelling with mom.
By spring, they will be on their own.
There's not much to this meal, especially for three grown lions.
♪♪ They try to drag the carcass away, but end up in a game of tug of war.
This thin strip of hide is not much of a prize.
♪♪ [ Wind whistling ] ♪♪ Our young fox is back on the hunt.
And this time, the weather is on his side.
He learned the basics of stalking and pouncing when he was just a pup.
But the real trick to this hunt is finding your prey.
How do you hunt an animal you cannot see?
The fox's quarry lies deep under the snow.
It's a meadow vole.
And this snow cave is it's igloo.
The snow forms an insulating layer, protecting the vole from the harshest winter weather and keeping him safe from predators.
♪♪ Although he may lack experience, this fox has all the tools he needs.
Foxes have incredible hearing and can detect prey under more than 3 feet of snow.
The tiniest movement can set the fox in motion.
♪♪ He's located the vole.
And with a pounce, he strikes.
This technique is called mousing, and it's something foxes are supremely good at.
The rest is just practice.
But there's far more going on here than meets the eye.
♪♪ ♪♪ It's believed that foxes can see magnetic north.
♪♪ And by aligning their prey in a northward direction, along with the sound of the prey... ♪♪ ...they can triangulate the precise distance of their attack.
♪♪ ♪♪ He's off to a good start, but he'll need more than a single vole to keep him fed.
It's just before dawn in Western Montana's Bitterroot Valley.
A lioness is taking a familiar path through the forest.
But she's not on the hunt.
She's already caught her quarry, and managed to take down a cow elk and her calf.
A meal that should last her several weeks.
The lioness has covered her kill in a pile of sticks and grass to conceal it from scavengers.
And there are plenty lurking in this forest.
A pine martin eagerly awaits his turn.
The lioness has had her fill for the day, but she'll return soon enough.
[ Howling ] Night envelops the forest.
A fox has discovered the kill.
A carcass like this a pretty big score when you've been subsisting on tiny rodents.
[ Twig snaps in distance ] A young mountain lion has discovered the carcass.
It's her first winter on her own, and this is a welcome meal.
But now the owner has returned.
Yet instead of chasing her off, the older lion shares the kill with the youngster.
These two lions are only distantly related, yet the older female tolerates this youngster.
This kind of resource sharing was once thought improbable among solitary predators like mountain lions.
But now it seems these solitary cats are far more social than previously imagined.
♪♪ [ Hooting ] ♪♪ Over the coming weeks, the young lion returns to these kills again and again.
This freezer full of meat has proven to be a vital source of food and will help this young lioness get through the winter.
And because of this experience, our young lioness is far more likely to share one of her own kills in the future.
With the last big storm of winter now upon her... snow is quickly burying the carcass.
But she is reluctant to concede her meal in the middle of this storm.
♪♪ ♪♪ This young lioness is lucky.
She has made her home in a protected area of Western Montana, free from development and safe from hunting.
This land, once a working ranch, has now been returned to the wild.
And this kind of re-wilding is happening across Western Montana.
♪♪ After decades of logging, forests, now protected, have become home to lynx... and wolverine.
♪♪ ♪♪ ♪♪ The last days of winter have finally arrived.
Rivers and lakes once again flow free.
♪♪ ♪♪ With the return of warm sunny days, western painted turtles clamber to sun themselves on floating logs.
And a family of bears, escaping from the heat of the day, cool off in their favorite swimming hole.
Many of the families that now call this forest home are drawn by the opportunities this restored habitat provides.
♪♪ And it appears our lone fox has found a mate and now has a thriving family of his own.
♪♪ [ Birds calling ] Across the Rockies, new families are taking their first tentative steps into the world.
And in the heart of Grand Teton National Park, crowds gather in anticipation of the Rockies' most famous bear.
Everyone is holding their breath.
♪♪ And they don't have long to wait.
♪♪ [ Camera shutter clicks ] This remarkable bear has defied the odds once again and triumphantly wades out into a sea of adoring fans with all four cubs.
[ Camera shutters clicking ] 399 has made their home in the northern portion of Grand Teton National Park.
And spends much of the spring close to the road.
It's one reason why this family has become so famous.
But that's not the only reason.
At least 22 grizzlies are the direct descendants of 399.
And the fact that they are here at all is remarkable in itself.
Just decades ago, there were fewer than 1,000 grizzlies left in the lower 48, in just 2% of their former range.
Today, thanks to grizzly bear recovery efforts, those numbers have more than doubled.
♪♪ ♪♪ 399 has become a symbol of grizzly bear recovery.
And shows us what is possible when we provide the minimal protection for wildlife.
And it provides a glimmer of hope that we can undo some of the damage we have done.
We can provide a safe home for all our Rocky Mountain families.
♪♪ ♪♪ ♪♪ ♪♪ ♪♪ To learn more about what you've seen on this "Nature" program, visit pbs.org.