All language subtitles for Yellowstone Wildest Winter to Blazing Summer 3of3 The Blazing Summer 720p HDTV

Stretching out before me is
the magnificent Yellowstone.

This is one of the most dynamic...

..unpredictable and
exciting environments on Earth.

Deep in the Rocky Mountains,

this vast wilderness is home
to North America's

most iconic wildlife.

But every year,
Yellowstone's animals are pushed

to their absolute limits.

Temperatures can swing from
-40 in winter

to approaching plus 40 in summer.

And at the heart of this change
is the thaw.

The melt can last from
March to July...

..and it's one of the most
dramatic, natural events on Earth.

How do the animals cope with
such extremes of temperature?

We're here to find out.

I'm joined by biologist
Patrick Aryee...

That's intense.

..and a team of wildlife cameramen
and expert scientists.

Previously, we've witnessed
how animals survive

Yellowstone's extremes.

Starting in winter,
it was well below freezing

and some animals really struggled.

Then, in spring, temperatures jumped
nearly 30 degrees in a fortnight

and wildlife had to cope with the
thaw coming three weeks early.

Now, summer is here
and there are new challenges.

The meltwater will dry up fast,

food becomes scarce...

..and if there's no rain,

wildfires will threaten to destroy
the habitats animals rely on.

SQUEAKING

Welcome to
Yellowstone's Blazing Summer.

So far in 2016,

every month has been hotter than
average in Greater Yellowstone.

If the trend continues,

summer could reach
record temperatures

and push animals
to the brink of survival.

Yellowstone lies over 600 miles

from the Pacific
and has a continental climate,

which means summers
can be relentlessly hot.

Now, at the moment it's all
still looking quite lush and green,

but in the coming weeks as the
temperatures continue to rise,

the vegetation will start to wither,

valleys will become dust bowls and
lakes and streams

will start to dry up.

Wildlife must travel further
in search of food,

drinking water and shelter
from the heat.

Young animals born back in spring
are now entering their first summer.

They're a lot more mobile,
but still need to avoid danger

whilst exploring
on those unsteady legs.

For this latest generation,

the change in climate will make
their lives even more challenging.

In spring, the beaver family was
affected by the

unusually warm temperatures.

Huge volumes of meltwater flooded
into the Snake River,

where the beavers have made their
home in the south

of Greater Yellowstone.

Snow melting from all the way up
there in the Teton Mountains

rushed down in a deluge and
threatened to wash

our beaver dam away.

Beavers dam rivers to create
a series of ponds,

where they live and feed,
safe from predators.

After working flat out on
emergency repairs to the dam,

the beavers just managed to save
their home from the flood.

Now, in summer, the family could
face the opposite challenge -

too little water in the river.

I've come to meet wildlife cameraman
Jeff Hogan

who's been following the beavers.

Hey, Jeff.

How's it going? There you are.
How are you doing?

Jeff was filming great grey owls
in spring.

Now, he'll use his specialist skills
to study the beavers and has

installed an infrared camera
inside their lodge.

SQUEAKING

I've got something to show you.

It was a bit of a surprise.

'This footage looks like the male
and female I saw here in spring.'

You see a couple of big,
fat beavers? Yeah.

SQUEAKING

'But then, something unexpected.'

Oh, my gosh!

PATRICK LAUGHS

They're so adorable.
That's a great shot.

Oh, my goodness. That's amazing.

No way.

Oh man, they're so adorable.

'Baby beavers are called kits
and Mum has given birth to three.'

I would say they're probably
about ten weeks of age, maybe.

'Kits are precocial,

'which means they're mobile
and quite advanced from birth.

'Emerging with a full coat of thick
fur, sharp chisel-like teeth...

'..and a characteristic flat tail.

'This, they use as a rudder
to steer when swimming,

'which they can do within a day
of being born.

'But these three still rely
on their family to bring them food

'from outside the lodge.'

I've got another clip for you.

SQUEAKING

Look at all that willow.

This adult beaver just brought
in three or four branches,

all bundled up.

And the little young ones
will just jump on this.

They'll gobble that right down.

'At ten weeks old, these kits
have stopped drinking

'their mother's milk.

'They now have an adult diet.'

In summer, the ponds
the beavers create

become their vegetable gardens.

The slow, warm waters create
optimal conditions

for edible plants to grow.

Mum, Dad and last year's young are
working overtime collecting food

for the kits and keeping the lodge
clean by washing grassy bedding.

In a matter of days,

the kits will leave the lodge and
learn to forage for their own food,

whilst avoiding predators.

Around 50% of beaver kits don't
survive their first six months.

It's a critical time for this
family, and Jeff

will be following them
every step of the way.

Across Yellowstone, our teams have
been documenting signs

that an early spring thaw
kick-started an early summer.

As icy meltwaters flowing off
the mountains subsided,

streams warmed rapidly in the sun.

And the surface of the water
started to dance.

Rising water temperatures trigger
mayflies to hatch in their millions.

These conditions are the starting
pistol for an important event...

The arrival of cutthroat trout.

Many have spent the winter in
Yellowstone's deep rivers and lakes,

but migrate upstream to feed on
mayflies and spawn

in these shallow waters.

Every year, the arrival of these
protein-rich fish creates a

feeding bonanza
for river otters, mink,

bears and birds of prey,
like eagles and osprey.

Over 20 different species of birds
and mammals.

This year, the early snowmelt has
given these predators a head start

to fatten up.

While summer temperatures have
created a frenzy of activity

on the rivers, Yellowstone's
low altitude grasslands

are eerily quiet.

'In spring, herds of elk and bison
were feeding here,

'but they've moved on as the green
vegetation withers in the heat.

'What the locals call
"the brown-up" has begun.'

Over the course of just a few
months, this ground has gone

from being covered in feet of snow
to lush grass,

which has now scorched, died away
and has very little nutrition.

So grazing animals like bison and
elk need to move further up

the mountains
in search of green shoots.

As the summer continues,
the brown-up will creep higher.

Bison and elk must keep moving.

By July, bison have arrived at
summer grazing grounds

on Yellowstone's high plateau.

This is the only time mature males
and females come together

and herds can
reach a thousand strong.

Scientists think this summer
the bison will look

particularly impressive
after an abundance of grazing

during a warm spring.

So Kate's gone to check out
what kind of condition they're in.

Oh, my goodness!

What a magnificent beast.

The male bison at this time of year
are truly just...

They are in their prime.

'Bulls have piled on up to
150kg of fat and muscle

'and now is their chance to start
throwing that weight around.

'July is rutting season, when
males duel for the right to mate.

'And this year's favourable
conditions mean it will be fierce.

'The largest contenders could be
tipping the scales

'at nearly a tonne.'

You may think, "Isn't it a little
bit early for sex?

"I mean, you know, it's the summer,
they should be chilling out."

But remember that bison
are the first to give birth.

Think back to the spring,
the first calves we saw,

they were bison calves.

'Female bison have one of the
longest pregnancies here,

'lasting over nine months.

'So to time the birth of calves
with the start of next spring...

'..these males need to get
on with it.'

This male bison has found
himself the perfect dust bath.

And, at various times throughout
the day, he will roll in it,

he'll cover himself in dust,
he'll pee in the dust

and roll in that.

Just to make sure that he smells as
virile and ready for it as possible.

LOW GRUMBLE

'Wallowing in dust baths
is a show of strength.

'Each male competes to churn up
the biggest dust cloud

'and intimidate its rivals.

'But when two heavyweights won't
back down, they go head-to-head.

Heavily-muscled necks and thick
skulls covered in a mat of

dense hair help absorb the colossal
forces of each collision.

Only the winner earns the right to
mate.

This ensures the strongest genes
will be passed on.

Whilst I've been following herds of
prey animals on the plateau...

..our camera crews are at lower
altitudes on the trail of

Yellowstone's top predator,
the wolf.

Over 500 wolves roam across
Greater Yellowstone.

The mild winter and spring caused
many packs to go hungry

as the prey was well fed and could
outrun the wolves.

In summer, the stakes are even
higher because there are young pups

to feed.

In the south of Greater Yellowstone,

biologists have been studying one
wolf pack that seems to be defying

the odds and thriving this year -

the Pinnacle Peak pack.

This photo was taken during an
aerial survey.

It reveals the pack has 11 pups.

Unusually, two females have given
birth this year -

a sign this pack is doing well.

All the adults take it in turns to
hunt and return to the den sites

with meat for the pups.

But the elk that make up the
majority of wolves' prey have moved

to higher grazing grounds.

The biologists have been observing
how the pack finds enough food

for all 11 pups. They've directed
wildlife cameraman

Charlie Hamilton James to an area
where they've seen

remarkable behaviour.

They think the key to the wolves'
success here could be down

to human activity.

See it?

I wonder if

she's going to let me get out.

I'm going to give it a go.

Bear with me on this.

WHISPERS: Well, well, well,
well, well!

How beautiful is that?

She can smell me. My scent is going
straight ahead.

She knows I'm here.

She's not bothered at all.

In all his 20 years of filming,

Charlie has never been this close to
a wild wolf.

This female is from the
Pinnacle Peak pack.

And something has drawn her here.

The grass is still green

because it's been watered over the
summer to improve grazing.

You can see all these sprinklers
behind her.

Cos they're watering the grass,

it's created some amazing habitat
for ground squirrels.

There's just tonnes of them.

A huge colony of grass-eating

Uinta ground squirrels is exploiting
this artificial oasis.

Usually, by mid-July, the grass
would be turning brown and inedible.

The squirrels would have started
entering their burrows to hibernate,

but not here.

This female wolf has spotted the
chance of an easy meal.

And it's closer to the pups than the
large elk herds 20 miles away.

They need these ground squirrels
cos they're tied to their territory.

They've got pups here, they can't go
anywhere else,

so they have to find food around
here...

..just to survive and keep those
pups alive.

But catching these burrowing rodents
is tricky.

They spend much of their time
looking for danger,

balancing on their hind legs to see
over the tall grass.

The squirrels also have a range of
alarm calls for different threats.

SQUIRREL TRILLS

A trill means it's a ground-based
predator.

SQUIRREL TRILLS

The entire colony dive for the
safety of their burrows.

Look at that! She's on it. She's on
one. She's on one. Oh!

This female is putting in a lot of
work but without any reward.

Oh, there's another one. There we
go! There's one running.

Ah! Where is it? Where is it?
Where is it?

A long way off.

Another pack member may help turn
the tables.

Wolves' real strength is when they
hunt together.

There's another one.

There's another wolf!

I don't know which one to film now.

SQUIRRELS TRILL

The ground squirrels can't watch all
three wolves at once.

And these newcomers are also trying
a different hunting strategy

to outwit their quarry.

SQUIRREL SQUEAKS

There's a lot of activity and then
they'll lie down.

And you think, well, why are they
suddenly lying down?

Part of their hunting strategy is to
lie down

and essentially just wait for the
ground squirrels to come up to them,

you know, and they're sort of dozing
and they're half asleep, and

a ground squirrel comes up and they
just leap up and grab it.

It's working.

Even the original female is having
more luck.

With animals, you get these peak
moments of activity and they last

for a few days or a few weeks and
then they're gone again.

It's incredibly lucky that we've
been able to be here for this

particular period of peak activity.

I've never seen it before, I don't
know if it'll ever happen again,

but it's amazing to witness it.

These wolves have used all their
intelligence to exploit this
situation.

The food will increase the pups'
chance of survival.

And more wolves means a stronger
pack next year.

It's early July and no rain
has fallen this month

at the Snake River, where the
beavers have their home.

This, combined with the early snow
melt,

means that the river is running 20%
below its average.

If the level of the beavers' main
pond drops too low, it could expose

the entrance to their lodge,
which is usually underwater.

And this would make them easy
pickings for predators.

Jeff is watching them closely to see
how they react.

Oh, look! Wow!

That's Mum.

And it looks like Mum has made an
executive decision.

She's got one of the kits in her
mouth.

She's heading towards the dam.

She's moving one of her kits out of
the pond,

maybe to search for a new home.

This is incredible!

And there they go.

I'm going to go chase them.

Scientists have observed beaver
families relocating,

but Jeff has never witnessed it in
20 years of studying them.

Out in the open, kits are vulnerable
to predators like bald eagles.

It's a tense moment for Mum and her
young.

Here they come.

The beaver family's territory is
large,

with five dams and pools along this
river.

She's going to crawl over this next
dam.

After travelling more than 350
metres...

..and crossing three more dams...

..Jeff films the mum leading her kit
up a small channel that comes off

the main river.

They're going to climb right up
through this cascading stream...

..waddling up through the stones.

You can see that the beavers don't
do quite so well on land,

especially with this river rock.

They do so much better in the water.

Unreal!

Never seen this, ever!

And there they go.

Later, at night, Jeff checks his
camera in the lodge.

Let's see.

It reveals Mum has moved all the
kits and the whole family has

abandoned their home.

Jeff is now on a mission to find out
where the beavers have gone...

..if the kits survive and whether
this huge gamble will pay off.

Whilst the low-lying rivers and
grasslands are sweltering

in temperatures of nearly
30 degrees...

..2,000 metres up, Yellowstone peaks
have a recent dusting of fresh snow.

And the mountain meadows are a riot
of colour.

It is amazing, the contrast up here
to down in the valley.

Down in the valley, summer has
really taken grip -

the temperatures are quite high and
the grass is starting to go brown.

But up here, 800 metres higher, it's
a totally different story.

It's breezy, it's cool, and look at
all these magnificent wild flowers!

Susan Marsh is a naturalist and she
pays very close attention to these

high-altitude wild flowers.

Where most people see pretty petals,

Susan sees a living record of how
this ecosystem is being affected

by this year's weather and the
changing climate.

We've looked a lot
at how animals can indicate

the state of how
a year is progressing,

as far as the weather is concerned.

Are the plants just as valuable
as indicators?

Yes. I think they are

and the one advantage

that they have, in my opinion,

is that they don't run off!

And they don't fly away.

Very true. I can tell by how tall
they are, first of all.

Right. This one is fireweed.

And it, typically, in a really
lush year, will grow head high.

Wow! Even at this elevation.

These particular ones, you can see,
are only a couple of feet tall.

Yeah, yeah. To me that's
an indication of heat and dryness.

The plant needs to set seed and it
has a very short growing season,

so it's not going to waste
its energy making a big, tall stalk,

or making great big leaves.

Right. These leaves are small
this year, smaller than usual.

Through these plants, Susan can
chart this year's erratic weather

but can plants
also indicate larger changes?

Everyone is talking about the fact
that the climate is changing.

Is that something that is becoming
evident in the plants?

It's typically on the mountain tops.

So that's above the tree line.

Above the trees, where there's rocks
and wind and cold.

It's the coldest part
of Yellowstone, above 3,000 metres,

where Susan is seeing the effects of
climate change hit hard.

This is the alpine zone, a realm
of high-altitude specialists.

But as temperatures
keep getting warmer,

non-specialist plants are able to
survive higher up the mountains

and they're invading
this fragile zone.

Does it concern you
that you are seeing

a march towards
a very different climate

and, therefore,
a very different ecosystem?

I think there will be some good
and some bad,

depending on what species you are,
as climate change continues.

But, yes, I don't want to lose
the wildflower parts that I love.

I don't want to lose
the alpine zone.

I don't want to see those go,

but I don't think I can stop it.

Climatologists
studying Greater Yellowstone

have charted temperatures increasing

by nearly
a fifth of a degree every decade.

This seemingly small change
is having far-reaching consequences.

Across Yellowstone,

scientists are seeing how animals
are being forced to adapt.

Even the most iconic species like
the grizzly bear are being affected.

To find out what's going on,

Patrick has gone
to the Gallatin mountain range

in the north-west
of Greater Yellowstone.

I've come to meet our bear expert,
Casey Anderson,

to see how one group
of grizzly bears is coping,

as the changing climate threatens
an important food source.

If you look up at this knob up here,

take a look at the trees
just around the bottom of that.

Those are white bark pines.

Let's have a look.

That entire forest
of white bark pine, ancient trees,

some of them are 300 years old,

they've all died
in the last couple of years.

They're gone.

What's caused it to die off?

There's a pine beetle
that's always existed up there,

but we've had these cold winters

that usually just killed
most of the beetles,

but now, with climate change,
those winters are not as harsh,

we're not having that beetle kill

that we're used to
in the middle of the winter,

so the beetles are really
starting to infest the forest.

Pine beetles are no bigger
than grains of rice

but these small creatures
cause big problems.

Not only do their young eat
the trees' living tissue,

but they also introduce
a destructive fungus.

Eventually, this combination
kills the entire tree.

This is bad news for the animals

that rely upon the food
and shelter this tree provides.

Towards the end of summer,
as other food sources dry up,

these pine nuts usually provide
vital protein for grizzlies.

One aerial survey revealed around
80% of mature white barked trees in

Greater Yellowstone show signs

of moderate-to-severe
beetle infestation.

To survive, the bears must adapt

and Casey has witnessed
some intriguing behaviour.

Grizzlies are leaving the wilderness

to congregate on this cattle ranch
to feed.

What they are eating
is this caraway root

that actually came in
with livestock.

It's actually an introduced species
not native to the area

and they're coming down here
and taking advantage of it.

And all the bears in the area
are starting to migrate
towards this meadow

because there's not a lot of food
out there in the summer but,

right here,
this is like a bear buffet!

It's a race against time.

The bears must pile on enough fat

to see them through
five months of hibernation.

While the root is at its most
abundant in summer and autumn,

the grizzlies gorge throughout
the night,

eating up to 20,000 calories
in a single sitting.

As the day heats up,

the hot sun forces them
back into the shady forest to rest.

But Casey and our mobile camera team

have seen two bears that are
still out in the midday sun.

Hey, Casey, do you copy?

They're, like,
totally tumbling around out there.

Well, they're little playful guys!

These two yearlings are orphans.

Unfortunately, their mum died
last autumn but,

against the odds,
they have turned up in this meadow.

I've joined Casey to see
how they're doing.

Right here, there's two yearling
grizzly cubs,

right out here, digging around.

Oh, yeah, right there.

They're still young
and inexperienced.

Cubs usually stay with their mums
for up to three and a half years

but, even with this protection,

almost a third won't survive
in Yellowstone.

It's a miracle that these two

made it through an entire winter
on their own.

Do you think that having one another

is one of the reasons
why they've made it this far?

I think it's got to be one of
the biggest reasons.

If they didn't have each other,
I don't think there's any chance

that one of them would have
survived.

They've got each other's back.

Whilst feeding on this working
ranch,

there are lots of unusual sights
and sounds.

But without a mum to teach them,

it's hard for the cubs to know
what is and isn't dangerous.

You find yourself
really worrying about them

because they don't have

that notorious Mama Grizzly
looking out for them.

Yeah, they're looking
a little bit nervous.

So they're looking at something
over in the distance.

They've obviously sensed something
in that direction.

I think that these two
have probably been chased,

probably once a day, by something,
whether it's another grizzly,

a pack of wolves, or even cattle.

Surprisingly, the dangers may not
come from the ranchers

or their cattle.

Most have learned to live alongside
their grizzly neighbours.

One of the biggest threats
comes in the form of other bears

close by in the shade
of the forests.

A big male grizzly, known as a boar,
could kill and eat the cubs

but it looks like these two have
found a way to avoid this danger.

The big boars and other bears
are out at night

because when it's hot, like this,

most bears will not
come out and dig,

because it just wears them out.

And as the sun comes up,
they go back to the forest.

With these little guys, they're
kind of on the opposite schedule.

When the danger goes away,
it's time to eat.

Let's do it in the heat of the day
when there's nobody else out here.

Where you don't have to worry
about anything.

That's what they're doing
and it's working for them.

It's an amazing strategy.

The two cubs
are a fantastic indicator

of just how intelligent
bears can be.

Even as climate change kills off
the white bark pine,

the bears are adapting
to exploit the opportunities.

With over 700 grizzlies
in Greater Yellowstone,

the latest data suggests
their population, for now, at least,

has remained stable.

Yellowstone hasn't reached its
record temperature of 36 degrees

but climate data has revealed
that July, this year,

was the seventh month in a row
with above average temperatures.

The relentless heat

and the early thaw
are a dangerous combination.

They may create perfect
conditions...

..for wildfires.

In normal years, the snowmelt
would come down off the mountains,

and it would hang around places,
like this,

soaking into all this dead wood,
but not this year.

What it did was come rushing off
in a great torrent

into the rivers, into the streams,
into the lakes

and it didn't have time to soak into
all of this dead, dry wood.

So this is, basically,
fuel for fires

and having so much
dead, dry wood around

means that there is a danger
this year

of bigger and more intense fires.

A single spark
could set this landscape alight.

Every summer,
an average of 26 wildfires

are started by lightning
across Yellowstone National Park.

Our crews are out, following up
on reports of wildfire.

Flames can reach heights
of 50 metres, exceed 1,200 Celsius,

and rip through the landscape
at up to 40mph.

By mid-August,
the tinder-dry conditions

mean five major fires
have taken hold,

and are raging across the region.

In the Beartooth Mountains
is wildlife cameraman Jeff Hogan.

Oh, no, this is nuts!

He's filming a wildfire that's
consuming a huge area of forest.

And it's headed straight towards the
family of great grey owls

he's been following since spring.

This fire is huge, and it's raging.

It's right in the backyard
of our great grey owl family.

This is really a threat.

So far, the chicks have done
much better than expected.

There was only a 20% chance all
three would make it out of the nest.

Oh, he's going to go,
he's going to go.

Jump, jump!

Oh, wow!

Jeff thought
their biggest challenges were over.

But now, he'll have to wait
until the fire's died down

to see if these young owls survive.

Oh, my goodness.

The aftermath of a fire
might seem devastating,

but it's actually part
of the forest's natural cycle.

It brings growth and new life.

All this ash is actually
really fertile

and as soon as it rains,

new green shoots are going
to start popping up,

and that's going to encourage
grazers like elk and deer

to come into this area and,
eventually, grizzly bears.

But not only that, some plants
have actually evolved

to benefit from fires. These here
are lodgepole pine cones

and they only open up once they
reach a specific temperature

that can only be produced by a fire

and then these seeds
will eventually fall off,

down into the ground

and be fertilised by the ash.

Fires are a natural part
of life here.

But by the time they die down,

they will have burnt nearly
100 square miles of land.

This year's fires will have been
the most destructive

inside Yellowstone National Park
since 1988.

Large-scale fires used
to sweep through the park

around every 300 years.

But scientists now believe that
the warming climate could result

in them happening every 3-5 years
by the end of this century.

This could result in the destruction
of the forest

that's home to the fragile
population of great grey owls.

Jeff is searching the area
at the edge of the burn

for any sign of the owl family.

There's a lot of ground to cover

so Jeff calls in expert
animal tracker Dan Hartman.

After four days' searching,

Dan finally hears
an adult great grey.

OWL CALLS

And close by, one of the young owls.

OWL CALLS CONTINUE

After another few minutes
watching and listening,

he spots the other two siblings.

All of them have survived.

And they're even making
their first attempt at hunting.

The owl chicks have all made it
through their first summer,

but we still don't know the fate of
the beaver mum and her three kits.

I've joined Jeff on a tributary
of the Snake River,

where he's seen signs that the
beavers are making a new home.

He thinks it's a safer location,

as the water level is higher
than at their old pond.

Oh, look.

There's your beaver sitting there.

Oh, my... Is it that beaver there?

That's the beaver, right there.

This is just gold dust.

This looks like Mum.

And in the few weeks since moving,
the family has been busy building.

That is a new lodge
being built right now.

They just make a big pile of sticks,

then they go into it
and start digging it up

and they'll pile mud and stuff up
on top of it.

This is a lodge at its early stages.

This is rare.

Rarely do you see the very early
stages of a whole new beaver pond

with a lodge like this.

They're concentrating on their dam,

strengthening it with rocks
and plugging any leaks

with weeds and mud to
create a deep, wide pond.

The water table here is rising
so that they can reach out

and get more of this food,
the trees that grow around here,

cotton woods, alders, willows.

The beavers can now access
all this untapped food...

..without having to venture far onto
dry land, where they are vulnerable.

'Finally, Jeff spots what we've both
been hoping to see.'

Oh, yeah. There's a young one.

There's the young one. Yes, yes.

We've got our three young beavers
right here, the three kits.

They're getting big. They are.

They're getting big fast.

Mum's risky gamble appears
to have paid off.

This deep pond with a new lodge
and plenty of food

is everything the kits
will need to thrive.

They are so inquisitive,
aren't they?

And they're just...

They're just fabulous to watch.

The kits will stay with their
parents for the next two years.

In that time, they'll learn
the engineering skills needed

to build a dam and a lodge.

The secret to the beavers' success

is adapting the landscape
to suit their needs.

It's engineering on a scale that has
only been surpassed by humans.

Every year, the challenges in
Yellowstone are getting greater,

as climate change results
in more extreme weather.

Yellowstone's residents
have developed

clever strategies to survive.

But the last animal I want to see

is quickly running out of options
as temperatures rise.

I've come up to 3,000 metres
and the fragile alpine zone.

Only one specialist mammal is
active up here all year round -

the pika.

And Kaitlyn Hanley is the hardy
researcher who studies them.

I've got glimpses of pika.

Are they a member of
the rabbit family?

They call them rock rabbits.

SQUEAKING
Oh, there was one. A little call?

Yeah, that was a pika.

Come on, Kaitlyn.

I want you to... He's right there.

Oh, my goodness, there he is!

Pikas are thought to have evolved
from ancestors in Siberia -

one of the coldest places on Earth.

Their odd appearance is
all about keeping warm.

A plump, round shape minimises
surface heat loss

and thick fur covers
their entire bodies,

even their toes.

For pikas, summer is all about
collecting food.

I imagine that up here,

the season where there is any food
at all is pretty short.

Yes, and they don't hibernate
in the winter

so they actually collect hay through
the entire summer.

And they'll use that as their food
source during the winter.

So that's what they're doing now?
Yes, they are haying, yes.

They'll get these huge hay piles
under the rocks

and they'll use that in the winter.

And, yeah, they're the only mammal
that doesn't hibernate up this high.

And they can survive?

Cos the snow must come here,
what, in October?

Yeah, so it would be October...

Through to?

March, May.

So, they've got a matter of months
to collect enough hay

to get them through
the whole of the winter.

Yes. They're busy little bees,
that's for sure.

Pikas love a cool climate.

Just a few hours' exposure

to temperatures of 21 degrees
can prove fatal.

So they can only exist in
Yellowstone above 2,000 metres.

Soon, even here, they may have
nowhere left to go.

Because these animals are
such high alpine specialists,

they can't survive at
the lower elevations.

Does that make them
particularly vulnerable

to things like climatic changes?
Absolutely.

They are very sensitive to heat.

And so as climate change and
the habitat changes for them,

they're going to move upslope.

You're already upslope at this
point, you can't go any further.

And so, for the pika, you know,
they don't have anywhere to move.

They're running into the sky.

Scientists have already
seen pikas disappear

from one-third of
their former strongholds

in warmer states to the south.

But Yellowstone's high country
still provides sanctuary.

At least for now.

I have hope. I don't think
we should lose hope.

Because they're too cute
to go extinct!

That's one very good reason

we should all be there
to save the pika

is they're just too cute
to go extinct!

PIKA CALLS

The arrival of autumn marks the end
of the great thaw.

We've seen
how the dramatic seasonal changes

affected Yellowstone's wildlife.

The mild winter meant
the wolves struggled

to hunt strong, well-fed prey.

And many went hungry.

WOLF HOWLS

But in the summer,
they used their cunning

to find food and
keep their pups alive.

The beavers survived
the spring run-off

and were able to build an entirely
new home to raise their three kits.

Our great grey owl runt
beat all the odds

and fledged with its two siblings...

..giving this vulnerable population
a much-needed boost.

The grizzly bears' race
to fatten up started early

with the mild winter conditions.

The wet spring and early green-up
revealed a bounty of food.

But by summer, they had to use all
their resourcefulness to survive.

This has been a magical window
into the lives of wildlife

in a truly spectacular landscape.

We've also seen a bigger picture
unfold,

as scientists try to predict

what the future for Yellowstone will
look like as the climate shifts.

I think what we do know is
all of it's going to change

and it's changing pretty rapidly

and we don't really know
how it's going to change.

There will be some good
and some bad,

depending on what species you are,
as climate change continues.

There are still
many challenges ahead.

But if there's one thing that all of
Yellowstone's animals share,

it's their incredible ability
to adapt to extreme change.

And this will give them the best
possible chance to survive,

whatever the future brings.