Yellowstone: Wildest Winter to Blazing Summer (2017): Season 1, Episode 1 - The Wildest Winter - full transcript

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
minus 40 in winter

to approaching plus 40 in summer

and at the heart of this change
is the thaw.



This melt can last several months
from March to July,

and is one of the most dramatic
seasonal 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...

Whew! That's intense.

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

I'll be following some of the area's
key wildlife.

We'll be getting to know families

through their highs and lows,
starting right now.

And I'm looking at
the bigger picture,

understanding the science
of the thaw

during each season, across winter,

spring and summer.



That's brilliant.

Living here is tough.

The changing climate
has brought freak storms,

flash floods and raging fires,

making life for the animals
even more extreme.

With unprecedented access
to this remarkable place,

over the next three nights
we're bringing you Yellowstone

as you've never seen it before.

Welcome to Yellowstone:
The Wildest Winter.

WOLF HOWLS

It's early March.

This is a world blanketed
in thick snow and ice.

And after four long,
hard months of winter,

the animals still have more weeks
of brutal cold to endure.

We are in the north-west of the USA,

2,000 meters up in the Rockies.

This is an area known as
the Greater Yellowstone Ecosystem.

It's the size of Scotland,

includes two national parks

and is bounded on three sides
by mountain ranges.

In this programme,

we'll be following the lives
of animals

that have to adapt
to extreme change,

as winter turns into spring.

For many, this is
the ultimate challenge...

..particularly for
Yellowstone's biggest,

and, at this time of year,
hungriest carnivores.

Patrick's heading high up
into the mountains on their trail.

It's amazing to think that somewhere
out there are grizzly bears.

But it's right at the tail end
of winter and it's really cold,

so most of those bears are still
going to be hibernating in dens

deep beneath the snow.

And, for most,
that's a sensible strategy.

Right now the weather
is bitterly cold

and down to minus 21 Celsius
up here.

It's usually later in March

that the majority of grizzlies
start coming out.

I'm in the Gallatin Mountains

in the north-west of Yellowstone.

Our grizzly expert, Casey Anderson,

is out here
monitoring bear activity.

Hello, Casey.
How are you doing, man? Good.

We're looking for any bears that
are emerging from hibernation early,

and the most likely place to find
them is at the higher elevations,

where grizzlies have their dens.

Good view, huh?

Absolutely stunning.

But it does look
completely devoid of life.

How are we even going to start
looking for these bears?

You're right, there's not much
moving around out here.

Right now the only bear
that probably will be out

is those first big males.

Casey believes some grizzlies
are already leaving their dens

because of a recent spell of
unseasonably mild temperatures.

So, just a few days ago
we had really warm weather,

it felt like spring.

It's been so warm you've got to
believe the bears are thinking

it's getting close to spring

and that can be really bad news,
because it's not spring

and they come out here
and winter can hit again

and that could really be devastating
to a lot of animals,

including the bears.

Last week, right here, it was
15 degrees warmer than today.

Now it's back to more typical
March conditions.

Casey, this weather's pretty...

HE COUGHS

Whew!

This is pretty intense.
That's intense.

How do the bears cope with this?

Bears are tough, but this
is difficult for them, too.

Suddenly, Casey sees an opening
that could be a bear den.

You see, like, these natural
rock formations. Oh, yeah.

It's like a little cave. Yeah.

It's perched high on a steep slope.

Not easy going.

The things I'll do for bears.

Would that be a good site
for a bear to hibernate in?

The statistics are this -

70% of bears will dig in
a north-faced slope.

At least 30% of this population
does something else,

and something else
is something like this.

Ready-made, in the sun,

they can get down in there
and trap the heat.

It's perfect.

And it's not all one big sleep.

During hibernation, the pregnant
females also give birth.

It's March now, and those little
guys were born two months ago.

So, just imagine these little guys
that big

and they're going to grow about that
big in about another month.

And then in another month from now

they're going to pop their heads
out, and this is going to be home.

It's just amazing, think about that,
the first view.

It's a pretty good one.

We head off before we disturb
any sleeping bears.

Emerging in these conditions would
mean the odds are against them...

..and 50 miles further east
that's exactly what's happened.

Scientists have tipped off
one of our camera teams

about a grizzly bear that has taken
the risk of emerging early.

It's clearly struggling.

The warmer weather of a week ago

has been followed by plunging
temperatures and more snow.

This could make finding food
impossible.

The grizzly finally makes it down
from the mountains

to the valley floor.

There are plenty of bison here,

but even a starving bear
won't tackle

these formidable beasts.

Bears rely heavily on their
extraordinary sense of smell

to find food.

Their nose bristles with over
a billion nerve cells.

It's their super sense...

..and it's led this bear to a pond.

A dip in the sub-zero water
could zap his precious energy.

Grizzlies are superb
at catching fish...

..but it's not fish he's after.

It's a bison.

Long dead, frozen all winter

and now released from its icy tomb.

This is probably the first meal
the bear's eaten

in over four months.

It offers a huge protein hit...

..but he'll need to hang onto it.

The carcass's smell
attracts scavengers.

These coyotes won't fight the bear -

he's 15 times their weight -

but they will harass him for scraps.

He tries to mask its scent
by covering it with grass.

This will also slow down
the bison's decay.

Having lost up to a third of his
body weight during hibernation,

he's determined to keep these
precious nutrients for himself.

Despite emerging from his den early,

this lone bear
has hit the jackpot...

..but the stakes are high,

and the majority of grizzlies
won't bother venturing out

until the consistent
warm weather of spring.

But that still seems a long way off.

The snow shows no sign
of letting up.

All the animals here face
the same basic challenge -

finding enough food
to survive until spring.

Our crews are out across the region

to capture the stories
of how the wildlife is coping

in these last days of winter.

Yellowstone's elevated position
and horseshoe of mountains

channel and trap the cold air
driving in from the north,

and moisture coming in
from the Pacific Ocean.

This leads to prolonged periods
of extreme weather.

When the snow melts in spring,

it feeds into a thousand rivers
and streams across Yellowstone.

These 2,500 miles of running water
are hugely important,

not just for Yellowstone,

but they provide
an essential resource

for millions of people and animals

right across the
Western United States.

Scientists constantly monitor
how much snow is building up here

during the winter.

To understand what's
going on this year,

I am joining a team up in
the Beartooth Mountains

in the north-east on
their cool commute to work.

This is possibly the best office
I have ever been to.

THEY LAUGH

This looks like a pretty good spot.

Oh, wow.

It's right at about
205 centimeters.

OK.

Lucas Zukiewicz is one of the
hydrologists

who spends the winter carrying
out health checks on the snow.

Our entire history of our snowpack,

starting mid-October,

is really in this snowpack here.

So we are going to dig a hole
down into the ground,

and it is pretty much
the coolest layer cake

that you're ever going to see.

LAUGHING: I love that.

I have a feeling that I might
be here for months.

Right, OK. So...

Yeah, I've hit grass!

That is so cool.

I have to say, coming from
a country where, you know,

if you get four centimeters of snow
it's newsworthy,

to look at that and to kind of
understand

that that is a record of your
winter, that's quite cool, isn't it?

It's amazing. And the best part of
this job is it's never the same.

Every year is different.

It's like hitting the reset button
on it every year.

So it's time for us to analyze
what the snowpack can tell us.

So, looking at it from bottom
to top, here,

we are looking at a time series.

So we have our early season,
October snowfall,

probably our Thanksgiving
and Christmas snowfall

that we have here.
You had a white Christmas?

We had a white Christmas this year,
it was great.

Various measurements enable
Lucas and his team

to work out how much snow is
building up here,

and how dense it is.

The texture of it here
is completely different.

It feels much more compact, exactly
as when we were digging it out.

The density reflects how much water
is contained in each layer

of the snowpack and that varies

depending on the temperature
when the snow fell.

Maybe we see some pretty well bonded
snow in here,

which is generally an indication of
warm temperatures.

OK. Warm temperatures actually bond
the snow pretty well together.

First of all, we're going to stick
one right up here

on the surface of the snow.

Measuring the temperature
is also key in helping to predict

when the bulk of the water will
flood down into the valleys.

The next one at 170,

we are going to stick that
right below

that little crust layer that we saw.

And these readings also
provide clues

as to why some mammals
hibernate deep in the snow.

Stick it right in the ground.

In the grass.

So, we can see here that our snow
surface temperature -

what does that one say?

I would say minus eight.

But as we move further down
the snowpack...

It's warmer! It's warmer,
it's minus three degrees.

That's mad.

OK. And if we go even closer
to the ground...

It's almost on zero.

Yep - so, the ground is generally
close to zero degrees Celsius

through the winter, so the snowpack
is also insulating the soil.

But it also makes sense,

when you look at something like a
grizzly bear

hibernating in the winter
beneath the snow -

I now understand
why it chooses to hibernate there,

because it's warmer.

Snow caves are pretty warm.

That's brilliant.

This insulating effect

not only allows bears to hibernate
in snow dens,

it keeps the grass alive.

Vital food for herbivores

and whilst it may look just like a
white wall,

we're actually looking at
an enormous reservoir.

When the weather warms up enough to
heat the snowpack right through...

..billions of liters of water run
off the mountains

into the rivers and lakes
of Yellowstone.

Is the timing of the thaw
important for you?

It is, because it affects when we
see the bulk of the water

move into our river systems. Right.

This is our reservoir that we have
in our mountains,

this is how we get our water, this
is how it flows through the park.

So, do you think
when the thaw comes,

it's going to be a normal year,

or an abnormal year?

We are slightly below average

with the snowpack that we have here
in place, at this elevation,

but really it is going to be the
next month or two

and the weather that we experience

that is going to dictate what we see
this year in terms of our thaw,

and how that impacts
the bigger ecosystem.

It will be interesting to see
what happens in the coming weeks,

as the weather has already proved
highly volatile this winter.

There was a jump in temperatures

and an unusually warm
period at the end of February.

March has now seen a return
to the colder,

more typical weather
for this time of year.

In recent years,

Yellowstone has experienced milder
winters more often

and this one appears
to be following that trend.

Patrick has headed south to see how
the temperature jumps this year

are affecting
another iconic species.

Snow is a lot more complex
than it looks,

and for one animal, a bird of prey,

the precise depth and type of snow

can literally mean the difference
between life and death.

This is the great Grey owl,

one of the largest owls
in the world,

with a wingspan that stretches up
to 1.5 meters.

It's a winter specialist.

It survives in some of the coldest
forests on earth,

from Siberia to Scandinavia...

..to here, in north-west America.

Researchers believe several hundred
great Grey owls

live in the Jackson Hole Valley,

all within 150 square miles
of forest.

Our cameraman, Jeff Hogan,

has had a lifelong love affair
with this enigmatic bird.

I've been following and filming
the great Grey owls

for just about 30 years now.

It's still just as exciting
and challenging

as it was the very first day.

This is a fantastic place
for owls to be hanging out.

I mean, it is mixed aspens
and conifer forest,

along with these meadows,

provide an incredible habitat for
the prey that the owl feeds upon.

Great greys feed on rodents -

mainly gophers and voles -
that burrow under the snow.

Their huge facial discs
act like satellite dishes,

directing sound to their ears.

Their hearing is exceptional.

They can detect prey
from over 100 meters away,

through snow almost
half a meter deep.

But it is one thing
knowing where to pounce,

another to break through
to reach the meal.

Jeff is out looking for them.

He is concerned that,
with the erratic weather conditions,

the owls face a big challenge.

Earlier this week we got a lot of
snow, and then the skies cleared,

so you can look around here and
see where the sun is beating down

on the surface of this snowpack,
and it really softens it up.

It doesn't melt completely,
but it makes it really soft and wet,

and then at night,
when the temperatures plummet,

it will freeze hard
and turn it to ice.

You can actually see this layer
of crust.

You can really feel that.

Ouch.

This is hard.

And as the temperatures drop
as night approaches,

this is going to get
harder and harder,

and these owls have to bust through
this crust,

and there may be another foot
of snow to get to their prey.

Jeff hasn't seen any great greys,

which could mean they have been
forced further afield to hunt.

So, I guess I'm going to have
to keep on looking.

At this time of year,
eating enough food is critical.

If the great Grey owls can't hunt,
they simply won't lay eggs,

or even nest this season.

Their population is already small
and vulnerable.

Biologist Katherine Gura is keen to
see how current snow conditions

might be impacting the owls'
ability to feed

and that involves
a simple experiment.

Katherine, you are stood out here
with a ruler, a meter rule,

and these flasks of water.

What do these have to do with owls?

So, this is about the same weight
as a great Grey owl.

So, what we are doing
is dropping these,

and we are seeing how far
they penetrate the snow.

Because it in turn can show us
how easy or hard it is

for great Grey owls to penetrate
the snow to get to their prey.

Right, Katherine, can
I give you a hand? Absolutely.

OK, so what do I do?

So you want to drop that
from one meter above the snow.

OK. So that's here.

One meter, that's here. Yeah.

OK, so it hasn't really gone
that far. It's gone about...

17 centimeters.

With their prey often underneath
twice as much snow,

this is why the owls are having
trouble feeding.

Our concern is that it is changing
the timing of their behavior.

So if there's not enough prey,

I mean, that's probably going to
spell disaster.

Are you worried about that?
I definitely am.

I've been working with
these owls for years.

I love watching them throughout
their nesting season,

and it really concerns me

if they are not going to be able to
have enough prey

to even attempt to nest,
or to eventually support the young.

This year, with
the tricky snow conditions,

the owls appear to be suffering.

To find out how they are really
getting on,

or indeed if they are around at all,

Katherine needs to conduct her
survey at night.

The night-time call
of the great Grey owl

is one of the early signs of spring,

and, for scientists,
this is the first time

they will be able to work out
exactly where they are,

what they're up to,
and how they are doing.

If the great greys are going to be
successful in raising chicks,

they should be out there right now,

and we hopefully should be able
to hear them,

but the thing is, this year,
nothing is certain.

Jeff has also joined us.

He is hoping his luck finding owls
will change

under the cover of darkness.

The survey area covers several
square miles.

Now, my top speed in snow shoes
is half a mile per hour.

This could be a long night.

All right, this looks like a good
spot to stop and survey.

OK, so what are we going to do?

So I will do the male
territorial call,

and then we want to be as quiet as
possible,

and we'll listen to see
if one responds.

Right, so, fingers crossed
we get an owl. OK.

I'll do my best.

SHE MIMICS OWL HOOT

OWL RESPONDS

Yep, that's it.

Right here. Yeah, this is great.

OWL HOOTS

It's responding.

So, is that probably a male?

So, that's a male territorial call.

So they will do that,
either to attract a mate,

and also to tell other males that
this is his zone, his territory.

Should I give it a go?

You should do it.

HE HOOTS

No, that's too deep!

See if he likes it.

HE HOOTS

Mine's too manly.

You've scared it off.

He doesn't want to get beat up!

So, given the conditions that
we're having this year,

this is a really good sign,

that we can hear
the great Grey owls. Mm-hm.

I was definitely worried, with kind
of the hard crust that we have had,

that they might not be
on territory yet,

but it is a good sign that they are
here and defending it.

OWL HOOTS

So, there are males out there

and they're defending
their territory.

Given this year's unpredictable
weather, it's a promising sign.

Jeff and Katherine
will continue monitoring,

and we'll be back to see
how the owls are getting on

later in the season.

All across the region,

the challenge for much of
the wildlife

is simply to hang on until spring.

It may appear that animals
like bison

spend the winter stoically
struggling through the snow,

but there is a respite for some...

..and it's thanks to a feature
that is synonymous with Yellowstone.

It's famed not just for its
landscapes and its wildlife,

but also for its geology.

Yellowstone has more geysers
than anywhere else.

In fact, 60% of all the geysers
anywhere in the world are here,

and the reason for that is
a giant magma chamber,

literally a pool,
a sort of lake of molten rock,

sitting just below
the Earth's crust,

literally right under my feet here.

Scientists believe there's
enough magma down below

to fill the Grand Canyon
more than 11 times,

and in West Yellowstone,

there's plenty of evidence
of all this geothermal activity,

particularly with
the dramatic geysers.

These hot springs intermittently
send fountains of water and steam

into the air.

It looks a fairly
inhospitable landscape,

but around 200 bison spend the
winter living and feeding here.

These bison are part of what
is known as the central herd,

and they don't need to work really
so hard to get at the vegetation

beneath the snow.

The earth here is warmed
by that magma chamber

bubbling away beneath the crust,

and that means there's
far less snow,

and the vegetation
is much easier to get at.

But scientists have discovered
that these easy pickings

come at a high price.

The hot water pushing up
from deep underground

dissolves the chemical compound
silica from the volcanic rock,

and deposits it on the grass.

Now, silica coats the vegetation
around geysers and hot springs,

and it's a little bit
like eating something

that has been covered in a very fine
dusting of ground glass.

It's enormously abrasive
and very, very tough on the teeth.

The other issue is the high levels
of fluoride in the water.

This chemical is a by-product
of historic volcanic eruptions.

In low doses, such as in toothpaste,
it's good for your teeth,

but here it's so concentrated
it actually softens,

rather than strengthens, the enamel.

Now, the combination of silica and
an excess of fluoride in their diet,

means that the bison down here
lose their teeth

significantly earlier than the bison
up in the north of the park.

In fact, life expectancy amongst
this herd

is at least five years less.

So, although these bison have an
easier life

than their snowbound cousins,

it's definitely a much shorter one.

Finally, by mid-March,

other parts of Yellowstone also get
a reprieve from deep snow.

It's melting faster
than it's falling.

Warmer air has come up
from the south

and pushed out the cold front
in the north.

Daytime temperatures rise above
freezing, unlocking the rivers...

..and the animals
make the most of it.

Underwater plants
are more nutritious

than those beneath the snow,

and are a vital food
source for this moose,

which needs to pile on
the pounds fast.

This muskrat is enjoying
the vegetation, too.

His double layer of waterproof fur
keeps him warm and dry,

even whilst eating
on an icy platform...

..and, when he dives down,
his lips seal shut

behind his big rodent teeth,

so that he can gather food
without swallowing water.

Even a winter casualty is good news.

This elk carcass will sustain many
scavengers over the coming days...

..and it may be here

thanks to Yellowstone's
most charismatic predator.

HOWLING

SHE GASPS: Oh, my God,
look at the wolves!

This is the most...

This is the most incredible view!

What becomes so evident
when you see a pack of wolves

running across the snow like that

is just how perfectly adapted
they are as winter predators.

There are some things that...

in life that floor you,

and seeing a pack of wolves...

I am completely,
completely overwhelmed by the sight!

To see what effect this year's thaw
is having on these animals,

I'm joining wolf biologist
Doug Smith.

We're on our way up a ridge
on Blacktail Butte

in the Northern Range,

home to a pack of 11 individuals

that lay claim to a territory
of 250 square miles.

Doug and his team constantly monitor
the wolves in Yellowstone.

He's concerned that climate change
is having an impact on them.

They just ooze charisma, don't they?

Even 2km away.

It's true.

There's something enchanting
and mysterious about them

that has gone through the ages.

Usually wolves thrive in the winter.

They are snow specialists.

Their feet fan out,

enabling them to run across
deep snow at over 25mph.

This gives them an advantage over
their prey, elk and bison...

..which struggle
with their cloven hooves.

Wolves generally have even more
of an edge in March,

when Yellowstone's herbivores
are weak and hungry...

..but this year is different.

By Yellowstone's extreme standards,

2016 has been
one of the mildest winters

ever recorded.

Temperatures have fluctuated wildly,

but, overall, they've hovered
three degrees

above the historic average.

A warmer winter is great
for herbivores

as there is less snow,

and they are less likely
to die of cold...

..but for their predators,
Yellowstone's wolves,

it can make life
a lot more difficult.

Because this winter
has been so mild,

do you think that that is going to
have a big impact on these wolves?

It certainly could.

I mean, hard winters
wear your prey down,

and that makes them easier
to kill for wolves.

A mild winter, their prey is going
to do a little bit better.

This winter was warmer
and, with below-average snowfall,

and it is early to tell
what the effect of that is,

but we think that wolf food
consumption rates, kill rates,

are down because of that.

So these milder winters
favor the prey,

and so does that mean fewer pups?

Which leads to smaller packs.

This changing winter weather
could be a huge impact.

Wolf kill rates are down this year,

but our camera teams
across the region

have caught some hunts on film.

Perhaps there will be clues

as to the problems wolves
are facing right now.

Talk me through
what's going on here.

I mean, that's classic
wolf hunting behavior.

What wolves are looking for
are behavioral cues

that indicate to them
that there is a weak bison.

Right. But what's interesting is,
the bison are staying in these areas

where there is either
no snow or little snow,

because they have got firm footing
and they feel confident. Yeah.

And so what the wolves are doing
is trying to bump them into a place

that's more favorable to them,
i.e., deeper snow.

This winter there's less deep
snow... Right.

..so the wolves are having
a harder time.

Plus, these brown places
have forage for the bison to eat

so they're going to be healthier.
Yeah.

That's also bad for the wolves.

The next hunt involves the wolves'
main winter prey, the elk.

Now, here is an elk encounter...
Yeah.

..and this is even more dramatic.

Look at that!
This female elk is very healthy,

and she is actually
attacking the wolf,

but she won't leave the dry ground.
Yeah.

Classic example of the importance
of snow depth and footing.

Look at the elk. Healthy elk will
always outrun a healthy wolf.

So, talking to the old-timers
who lived here in Yellowstone

during the 1960s and 1970s,
every winter was a deep snow winter.

It was the rare winter
that was not much snow.

Now, it's the rare winter
where you have deep snow.

It is more common
to have shallow snow,

and that's switching this balance
between predators and prey.

With so few successful hunts,

scientists have noticed
that some of the wolves

are turning to a summer
feeding strategy.

Instead of working as a pack,
they're hunting alone,

digging into burrows
to catch small mammals.

It's much less rewarding,
much harder work,

and, for this time of the year,
definitely unusual.

The repercussions could be huge.

The female wolves
are pregnant right now,

and poor feeding
may lead to weaker pups.

We won't know until early summer.

It's the end of March.

The signs of spring
are getting stronger every day.

I guess I weigh more than a coyote.

With temperatures warming,

many more grizzlies are coming out
of their dens.

Our bear expert, Casey Anderson,
is out searching for them

up in the Gallatin Mountains.

Sometimes it's not that hard

to work out where
they've passed through.

Hey, look.

You can see, right here,
it's all kind of worn out,

you can see these little claw marks.

Well, sometimes when the bears
come out of the den,

they can be a little mischievous.

If you look right here,

one of the first stops the bear
had made was this snowmobile seat.

Just ripping, clawing, biting,
just playing, really.

It's part of living
in grizzly country.

It is never certain when bears
will emerge in Yellowstone,

but this year has been more
unpredictable than ever.

It's been, really,
a strange year so far.

The spring temperature

has definitely gotten a few
bears up earlier,

we know that one bear has gone down,

pulled that bison carcass
out of the pond.

That was a risk worth taking.

But it was a risk.

Other early grizzlies
may not have been so lucky.

The adaptations animals
make in Yellowstone

to chime with its extreme
seasonal changes

are finely balanced,

and in tune not just
with temperature

and degree of snow cover,

but also with length of day.

Right up here,
there's a long-tail weasel.

It's running around right up here.

So, these long-tail weasels,
as soon as spring actually is here,

they will turn brown,

and they'll be camouflaged
for the spring, summer and fall.

When winter comes again,
they turn white, just like this.

The fact that he's still
completely white

shows that it is very much winter.

The changing color is triggered
by hours of daylight,

not by temperature.

He won't turn brown
until next month.

And just like the fox
and the coyotes,

he's looking for all the rodents
that live underneath the snow cover.

He's just tunneling down,
going and grabbing these things,

and popping up and eating them.

But whilst he is still white,
if the snow melts too quickly,

he'll lose his camouflage advantage,

and could be at risk
from predators himself.

And one mammal who would
happily eat him is a fox.

You can see this, like,
little story unfolding here.

This is a fox doing what they're
so good at in winter time.

A bear's greatest sense
is their sense of smell,

whereas a fox's greatest sense
is their sense of hearing.

And they literally hear a little
rodent way down in the snow,

they'll stop, and you'll see them,

they'll do this thing where they
pitch their head side to side,

and what they are doing
is really triangulating

and zoning in to the exact
location of that rodent,

and then they just do this giant
leap up in the air

and get this momentum
with gravity, and just, poof!

Right down into the snow,

and grab that little guy.

He doesn't even know he's coming.

He thinks he's down there,
all protected.

Little does he know,
up there is a fox.

A missile coming straight
down and getting him

and look at that,
that's quite a ways down.

A little vole is a pretty good snack
for a fox.

Whereas for a bear, it is nothing,

there's no way it could survive on
voles alone through the winter,

so that's why they choose to
hibernate,

there's nothing out here to eat
if you're a big old...

bumbling-around bear.

PATRICK: Down in the south,
there is also still plenty of snow

in the forest habitat
of the great Grey owl.

Cameraman Jeff Hogan has been out
night and day tracking them

to find out whether they're
breeding successfully.

We have an owl.

Jeff's been hearing and seeing
the male owls consistently,

which is a reassuring sign.

He'd feared they might have left
the area due to a lack of food.

We're going to set up here.

This year, the issue
has been icy snow.

It's prevented the great Grey owls
snow-plunging deep enough

to catch their prey.

The owls each need
at least one rodent a day,

and if they don't eat enough now,
they just won't breed.

He didn't catch anything.

There's something right here
underneath him,

because he's back.

He's going to make another attempt.

Oh, he jumped.

Oh, he's on the ground now.

I don't think he got anything.

He just flew up with nothing.

I've been here since dawn and he
hasn't caught anything yet today.

It appears the owls
are still struggling.

Then, at last, a sign of hope.

A female arrives.

This could get exciting. We've got
two great greys right here.

Following one bird is pretty
exciting, but to have two birds...

..it's amazing,
it really is amazing.

Let's see what goes on.

Oh, here, he's flying in.

Oh!

Mating. Mating!

Oh, my.

I've never seen this before.

This is great news.

It's incredible,
absolutely incredible.

For the end of March,

courtship, mating.

The next step is nesting.

Eventually, the pair choose to nest
on an old, broken spruce trunk.

How many eggs are laid will depend
on how much food the owls consumed

earlier in the season.

On average, they lay four,

but this year, it could be less.

We will be following them
to see what happens.

It's now April and the temperatures
are warming up.

This is Jackson Lake in the Tetons,

and normally it would be frozen
well into May,

but already the ice is breaking up.

The arrival of the melt
is a tipping point

for the wildlife of Yellowstone,

and this year,
after an extremely mild winter,

it's three weeks early.

At long last, though,
it's official - spring is here.

As the days get longer,
the sun is higher in the sky,

and its increased energy melts the
snow and raises daily temperatures.

Although there's still snow
on the ground,

the warming temperatures
are actually changing the shape

of the crystals
within the snow pack.

Now, they've turned into
tight little balls,

and there's a lot of water
in between them,

so the packs become a lot slushier.

It's literally at melting point.

All this snow
is just water in waiting.

Millions of tonnes
will gradually melt,

flooding into the lakes and rivers
of north-west America.

It's a process that will
continue until July.

It's the valleys that lose their
snow first,

and then, finally, the mountain
peaks release their huge reservoir.

Soon, these warmer temperatures
will lure the last male grizzlies

out of hibernation...

..and, with the snow retreating,

plants, too, are bursting into life.

A nutritious feast for hungry bears.

Patrick's back in the Gallatin
Mountains with Casey Anderson

to find out why a top predator

sometimes chooses
the vegetarian option.

Look right here.

This is biscuit root.

This is a grizzly favorite.

Bears are omnivores.

They don't just survive on meat.

Their diet also includes insects,
fungi, and lots of vegetation.

Many bears time their emergence

to coincide with biscuit root
coming into flower.

So, that is what they're
looking for, right there.

This bit of root at the bottom.

There's tonnes of calories in it.

So how much biscuit root
do they have to get through?

I've watched them eat hundreds
if not thousands of these roots.

What does it taste like?
You tell me.

I was afraid you were going to say
that, but I'm up to the challenge.

Bottoms up.

It's like carrots. Yeah.

Yeah, like a kind of starchy carrot.

Yeah. To be honest with you,
when I'm hiking around out here,

sometimes I look in my backpack
and see what I have for lunch,

and I look on the ground,
and I'm like,

"I'm going to go grizzly-style
here and start digging away."

As they put on weight
after the winter,

and more grizzlies come out,

they begin to communicate
with each other.

Each male can have a home range of
over several hundred square miles,

and they need to work out who else
is out there on their patch.

So, this is an old backcountry
camp in here,

people come up and camp
from time to time,

there's a little tent over here,

and this old outhouse,

that tree right next
to it is the rub tree

where these big males
will rub their back

and urinate all over the place,
right by the outhouse.

So it's a bear toilet?

It really is.

Look, see these big claws
right here. Wow.

And look right here, Patrick,

where the sap has stuck
all the hair...

Oh, yeah...stuck to the tree.
All down to here.

So, all this here,

this is...

bear hair. Yeah.

So, what they do, they come over,

and they just usually come up
and put their back on the tree,

and they'll rub their scent
all over it,

and they reach up and grab like
this, and they bite the tree.

Then they drop down,
particularly the males,

and they do this thing that
I call the cowboy walk.

So, they just stick it and they
twist their feet like this.

PATRICK CHUCKLES

They have real rigid legs,
and they're just really twisting.

So each bear that comes to this tree
will step in that same exact spot.

And they do it over and over again.

It leaves these big divots
in the ground.

So, if you're a smaller bear

and you really have to reach
for that next foot divot,

you know there's
a bigger bear in town.

This is a well-known rub tree.

We're setting up a camera

to see how many of the big males
are out there.

See this right here? Right.

It's going to take a recording,

and it's going to text me
to my cellphone.

No way. Yeah, real-time.

So, as soon as a bear's there,
I'm getting a text.

So, hang on. You're going
to get a text from a bear?

Exactly, that's exactly
what's going to happen.

A few days later, Casey has called
me in to look at the results.

Right, what have we got? Let's take
a look and see what it's caught.

Uh-oh!

THEY LAUGH

That's just brilliant.

That is an elk.

A cow elk. So, this is something
that always happens.

You set up your camera trap, you
think you've got the right angle,

and then one of the animals comes
along and wants to change the angle.

Oh, man! It's giving it a good go.
She's kicking it.

I think it shows their playfulness.

They come over to something new,
curious, and it's like...

"I think I'm going to play
a little soccer with it."

That's just great.

Let's have a look at a couple
of the other clips.

Whoa, first clip!

Exactly what we wanted. Wow.

That's a big male.

I guess it's what we would expect,

this time of the year,

that these big guys will be the
first ones coming out of the den.

The females and the cubs
are still up high.

Casey, Casey, this is a huge bear.

Remember when we set
this camera trap,

we were anticipating that we would
get the whole bear, but... Mm-hm.

Just missing the head.
He's bigger than that.

He stands at 2.5 meters tall.

He's giving it a real bear hug!

That's a bear hug, for sure.

Wow. And there we go,

doing that kind of cowboy walk
you were talking about, right?

Really trying to grind in his scent,

leave those marks.

That cowboy walk.

That means one thing -
"I'm in town and I'm the boss."

But what are they picking up,

and how do you think that affects
their behavior?

Well, as they emerge, it's the
beginning of the mating season,

so it's important for males to know
if there is a bigger male around.

It's like...
HE SNIFFS

"Oh, this big dude's here,

"maybe I don't want to be here,"
and they'll go the other way.

Equally for the females,
they want to know, you know,

who is going to be the father
of their next offspring.

Yeah. If there's any
big tough guys around.

Although the unusual weather
a few weeks ago

had brought some of them out
of hibernation early,

these males appear fighting fit.

Spring is in the air,
and the bears are getting frisky.

But they're not the only males
getting boisterous.

These elk are shedding
their antlers.

New ones will regrow
over the next few months,

ready for the autumn rutting season.

But perhaps the biggest male
show-offs are down in the south,

and Kate has a front-row seat
for their fabulous performance.

WITTERING

It's mating season
for the sage grouse.

They really like to make a proper
song and dance about it.

GROUSE WITTERS

That sound... It's really
difficult to describe.

It's like a sort of...

popping and a drumming.

It's that, combined with
these wonderful, very showy

puffed-up white chests,

and those fanned-out
black tail feathers,

that will attract the females.

Ooh, there's one.

And they will literally
do a fly past -

they'll sort of fly over
and look down

and say, "Oh, yeah,
I don't mind the look of that one,

"I'll give that one a go."

Greater Yellowstone is a
stronghold for the sage grouse,

a species under threat.

Once numbering tens of millions,

there are now just a few hundred
thousand of these birds left.

Many of them rely on Yellowstone,

where there is still plenty of
their habitat - sage brush.

It is now around 11 degrees,

perfect for breeding.

But success will depend
on how the thaw progresses.

Chicks won't do well if the
temperatures soar too quickly.

So far during the thaw,
some of our animals have done well,

and some haven't.

The jumping around in temperature

at the end of winter
confused some bears

and made life difficult
for the owls.

One of the mildest winters on record
and a lack of snow

prevented the wolves
hunting successfully,

yet the elk and bison emerged
from the season in high numbers,

and with plenty of fighting spirit.

Soon this landscape
will be transformed

from brown and barren
to lush and green,

but the arrival of spring
doesn't necessarily mean

that life will get easier
for our animal families.

All those newborn youngsters

will mean that there's lots of
competition for food,

and the predators
will be ever present,

on the lookout for the young
and the vulnerable.

Tomorrow night,

will the grizzly bear cubs
find enough food to eat

when they venture out
into the big, wide world?

We join a beaver family,

but will they deal with the deluge?

The water level is so much higher.

After a difficult winter
for the wolves,

will their luck turn?

And there is a nest
of great Grey owl chicks,

but will they all survive?

Oh, he is struggling.