Earth's Seasonal Secrets (2016-2017): Season 1, Episode 2 - Autumn - full transcript

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Every year, spectacular seasons
transform our planet.

They're the driving force of all
life on Earth...

bringing opportunities and huge
challenges.

Spring bursts with new life...

but it's a race to grab fleeting
chances.

Summer brings glorious abundance,

but the heat can push animals to
their limits.

Autumn is nature's great gold
rush...

but competition is fierce.

Winter creates a frozen
wonderland...

but only the most resourceful will
survive.



In every corner of the planet,

animals rise to overcome the
seemingly impossible...

to thrive against the odds...

as the seasons create the greatest
shows on Earth.

Autumn - the season when nature puts
on its most flamboyant displays.

It's as generous with its bounty as
it is with its beauty.

But the good times won't last.
The clock is ticking.

For many animals, it's their last
chance to get ready before the cold

closes in.

And the first challenge is to fatten
up and fill the larder.

The great Northwoods of North
America...

26 million acres of forest.

In autumn, as the days get shorter
and the light fades...

the trees go through a stunning
transformation.



They draw all the goodness out of
their leaves...

and then they let them go.

In a Canadian forest, along with the
falling leaves,

the trees are releasing a seasonal
feast...

acorns.

For a chipmunk, it's manna from
heaven.

He's stockpiling acorns for winter,

and the quickest way to carry them
is cramming as many into his mouth

as possible.

He can get six in, at a push.

There's no time to waste.

Within a couple of weeks, the forest
could be under half a meter of snow.

He needs to gather at least 100
acorns

to see him through the lean months
ahead.

A chipmunk keeps his store of nuts
hidden away in his winter burrow,

a meter underground, and for good
reason.

There are thieves around.

As soon as the coast is clear,

a light-fingered neighbour takes his
chance.

With winter coming,
pinching someone else's supplies

is a serious business.

The precious pile is starting to
look very thin...

and that could mean starvation for
the rightful owner.

The honest chipmunk is still
slogging away, gathering acorns...

but, when he returns, he's in for
a shock -

there's almost nothing left of the
store.

Retribution is swift.

CHATTERING AND SQUEAKING

With the thief sent packing, it's
straight back to work.

When winter comes, every nut will
count.

Autumn's abundance
will be a lifeline.

Chipmunks aren't the only ones
getting ready.

In Yellowstone in North America,
the trees are turning gold.

This moose has spent the summer
fattening up on greenery.

She'll stand up to her knees in
water for hours at a time,

feasting on pond weed.

When there's good food underwater,
a long nose comes in useful,

and she can close her huge nostrils
to keep the water out.

But the good times are coming to an
end.

Once winter takes hold,
the lake will freeze

and she'll be reduced to eating bare
twigs from trees.

So she's packing away more than 10kg
of greens a day...

while she still can.

But there's another animal in this
neck of the woods with a more

radical approach to gathering food.

TREE CRACKS

A beaver - the only animal capable
of chopping down an entire tree.

He'll fell a cottonwood in a couple
of hours, using only his teeth.

He chews away just enough to make it
unstable...

and lets the wind do the rest.

TREE CRACKS

And then the real hard work starts.

He chops the branches into
manageable chunks to eat later...

and the best way to get them back
home is by water.

So he and his partner have built a
network of waterways

especially for the job.

While he's busy bringing in the
supplies,

she's doing some maintenance to the
dam.

In a couple of weeks, their canal
system will freeze up,

so they're gathering food now, while
they still can.

They'll survive all winter eating
nothing but these branches.

He drags them one at a time to his
underwater larder.

He might bring in several hundred of
them...

so even when the pond
has frozen over,

there will still be plenty of food.

All this industry has caught the
attention of a young moose.

A beaver's pond could be the perfect
place to find something to eat.

But he can forget that idea.

This is no time for sharing.

Autumn might be the season of
glorious color,

but it can be a wild time, too.

THUNDER RUMBLES

As the temperature starts to fall,

changes in air pressure cause
massive storms.

THUNDER RUMBLES

In the river in southern Alaska,

the storms are about to bring in one
of autumn's biggest feasts,

and on the river bank, a hungry
crowd is gathering...

grizzly bears.

If they're going to survive the
coming winter,

they need to build up their weight by
more than half in just a few weeks.

It's the wettest time of the year

but all this rain is good news for
the bears.

It's flooding the rivers...

opening the way for millions of
fish to start heading their way.

Pacific salmon.

They've traveled thousands of miles
of sea and now they're swimming

inland to spawn.

They're returning to the very rivers
where they were born.

And the bears are lining up to meet
them.

They're gathering at a waterfall.

They know that the salmon must pass
through this bottleneck in the river.

It will be the best fishing for
miles around.

BEARS GRUNT

The biggest males start to fight
over the prime spots.

BEARS ROAR

The salmon are starting to collect
in a whirlpool at the bottom of

the falls.

With one almighty push, the first
fish starts its ascent.

It uses its whole body to leap more
than two metres in the air...

and if it's lucky, past the
waiting bears.

But eventually, the migration hits
its peak.

There are so many salmon, the bears
can hardly miss.

A big male bear can catch as many as
30 fish a day.

But it's not always as easy as it
looks.

This is a tough neighbourhood.

A female with three young cubs
nervously approaches the river.

She's desperate to fish, but these
big males could attack her family...

BEARS ROAR

so it's dangerous.

BEARS ROAR

BEARS ROAR

After a long summer nursing three
cubs, she's skin and bone.

Unless she can eat soon, she'll
struggle to get them through winter.

The big males carry on bingeing...

but one by one, they haul themselves
out of the river for an afternoon nap.

They're so full, they can hardly
move.

It's the young mother's big chance.

She climbs to the top of the falls,
but she'll have to be quick.

SHE GROWLS

SHE GROWLS

SHE GROWLS

Finally!

The salmon run is vital to every
bear on the river.

They'll sleep for six months, all
through the bitter Alaskan winter...

so the fat they lay down now will
help guarantee

their survival.

If this young mother can keep
fishing...

she'll give her family the best
chance of making it through till spring.

But not everywhere offers such rich
autumn pickings.

For animals across the planet, sometimes,
the only option is to leave home

and look for better times elsewhere.

In North America every autumn,

hundreds of pronghorn trek across
Yellowstone...

to escape the advancing snow.

They leave their summer pastures and
race to the safety of the lowlands,

where they can graze all winter.

In the Arctic, birds that came here
in spring are starting to make

an exit.

The seas have provided a bounty all
summer, but as autumn creeps in,

food is getting harder to find.

The bonanza is over.

Hundreds of thousands of birds are
heading south.

SQUAWKING

Snow geese spend the short summer in
the Canadian Arctic,

raising their families,

but in autumn,
they travel 3,000 miles south

to the warmth of the Gulf of Mexico.

The birds fly together in enormous
flocks.

There may be more than five million
of them,

all making this vast round trip.

But for some animals, these journeys
are fraught with danger.

On the Norwegian island of Svalbard,

100,000 Brunnich's guillemots have
been here since spring,

nesting on the safety of the sea
cliffs.

Now their food's running out

and it's time for these young
families to go.

But these parents face the worst
possible mission.

SQUAWKING

Each pair have one precious chick

and they've spent all summer looking
after it.

Now they must persuade it to jump
off the cliff, down to the sea.

It's a drop of 150 metres.

The chicks are only three weeks
old...

and they can't fly properly.

It's a terrifying leap of faith.

And there's worse.

There's a family of hungry Arctic
foxes waiting on the beach.

The chicks must make it all the way
to the sea without touching land.

The first dad encourages his chick
over the edge.

Not far enough.

He makes a desperate dash for the
sea.

FOX GROWLS

CHICK SQUEAKS

The next family step up to take
their turn.

Anxious to save his offspring from
the same fate,

his dad goes with him.

But they both fall short.

So close and yet so far.

FOX BARKS

A third family has witnessed the
grim fate of the neighbours,

but there's no other way down.

SPLASHING

It may not be the most graceful
landing, but they're all down safe.

When parents fly with their chicks,

they have a much better chance of
survival.

THEY CHIRP

But this is only the start of their
journey.

Now they have to travel south to the
coast of Greenland,

where they will spend the winter.

And because they're not strong
enough to fly,

the chicks are going to have to swim
there...

and it's 600 miles.

But Mum and Dad will be with them
all the way.

Even when you can fly, these autumn
journeys are an enormous challenge.

In the skies above Central Asia,

it's the start of one of the
toughest migrations on the planet.

THEY SQUAWK

Demoiselle cranes.

They've spent the summer in Mongolia
and Kazakhstan, but now winter is

breathing down their necks, so
they're flying south to India.

But first, they must cross the
world's highest mountain range,

the Himalayas.

In places, these peaks tower five
miles high.

The cranes can't go round them

because this mountain range spans
five countries.

They have to find a way through.

And to make things worse,

autumn brings treacherous storms to
this part of the world.

The cranes gain height, trying to
break through the clouds,

but strong headwinds force them
back.

They're beaten, for now...

so they set up camp for the night.

SQUAWKING

But they dare not linger.

There'll be more storms on the way.

SQUAWKING

At dawn, there's a window of clear
weather.

SQUAWKING

It's now or never.

But to get any further, the cranes
must cross Sniper Alley.

The golden eagles that live here
have been expecting them.

The eagles know the cranes will be
coming this way in autumn.

Normally, they'd be too fast to
catch...

but, right now, they're flying
tired...

and the eagles work in pairs.

One eagle picks out a young bird and
sets up an ambush.

BIRD SQUAWKS

He drives it into the talons of his
partner.

The exhausted crane never stood a
chance.

One man down, the rest of the flock
pushes on.

They use rising columns of air to
help them gain height.

They may reach altitudes of 26,000
feet.

And finally, they're across this
vast mountain barrier and heading

south towards India.

Many of them won't make it, but this
monumental journey is the only way

to stay ahead of a brutal winter.

They'll fly a distance of more than
1,000 miles and, in spring,

they'll fly all the way back.

For another animal, autumn starts a
migration

of a totally different kind...

and it happens under the sea.

The oceans cool more slowly
than the land,

but as the temperature
starts to change,

it triggers an unusual autumn
spectacle.

In the Southern Ocean
of South Australia,

there's a big crowd starting to
gather.

Giant spider crabs are marching in
unison across the sea floor.

They spend most of the year
offshore...

but, in the autumn, these big
orange crabs head to the shallows.

They're getting ready to moult.

They've outgrown their shells and
they need to grow a new one.

It can take them up to an hour to
crack open their old Armour plating

and wriggle out.

But it takes a couple of weeks for
their new shells to develop...

and waiting naked on the sea
floor...

is dangerous.

A stingray.

The crabs scatter in a panic.

There may be 250,000 to choose from,
but the ray is particular.

The softer the crabs, the easier
they are to swallow.

But the ray barely makes a dent in
the population.

There's safety in numbers.

And with so many crabs gathered
together,

some take the opportunity to look
for a partner.

With the party over,

the crabs step over the discarded
remains of their old wardrobe

and head back to the deep.

For lots of animals, autumn is
the season for finding a mate.

But it's an intense time of year.

And with winter round the corner,

the search for a partner is
full of challenges.

Only the toughest will succeed.

Male wild ass, fueled with
testosterone,

tear up the Tibetan plains as they
compete for mares.

Timing is critical.

They need to mate now so their foals
will be born next summer,

when there is plenty to eat.

Off the coast of Britain, Grey seal
bull fights are a bloody affair.

Only the biggest and bravest will
get to breed...

and he'll mate with every female
on the beach.

In North America, male elk live
quiet lives until autumn,

when they come together for the rut.

They grow a new set of antlers
every year,

weighing almost 20kg.

The bigger the antlers,
the stronger the bull.

ELK GRUNTS

But for one animal, the battle to
breed is not only about brute force,

it's also about technique.

Patagonia, South America.

Autumn is approaching

and a male Darwin's beetle is
looking for a partner.

His success will be down
to the size of his jaws...

and how he uses them.

He heads off to the forest
to start his search.

The females will be in the trees,

probably feeding somewhere on
the trunk.

They should be easy enough to find.

But when the trees are
more than 25 metres tall,

it's a long way to climb.

There she is.

Unfortunately for him,

all the other males in the
neighbourhood are also after her.

He has no choice but to fight them
off.

But it's not just about strength.

It's about...

grappling.

He reaches over the rival's head and
hooks his enormous jaws under

his wing covers.

He gets a grip,

lifts...

and chucks.

He climbs onwards.

There are other males standing in
his way,

but nothing will stop him now.

They meet at last.

She doesn't appear to be totally
smitten.

But she finally allows him to wrap
his great big jaws around her...

and they get intimate.

But then,

he throws HER out of the tree.

Beetle Armour is tough and, luckily,

she's just where she needs to be to
lay her eggs on the forest floor,

among the roots.

For many animals, these fights
to breed

are triggered by the shortening
days.

It's a race to get ahead of
your rivals before time runs out.

In Alaska, the tundra is
turning red

and the stage is set for
an almighty showdown.

A musk ox.

He's spent the last few weeks

fighting to keep control of a harem
of females.

Over the few weeks that they are in
season, he'll mate with all of them.

But he needs to be on his guard

because he has competition.

Another bull is trying to muscle in.

The dominant bull is going to have
to fight him off.

The interloper turns his back

and the king charges.

These bulls have a layer of horn
across their heads

ten centimetres thick,

which helps protect their brains.

But the impact is so loud...

it can be heard a mile away.

CRUNCHING

The dominant male tries to turn
his challenger around.

If he can strike at his flank,
it will all be over.

With the competition seen off,
the male returns to his females.

If he can keep other bulls away,

it will be his calves born on
these pastures next spring.

With winter just around the corner,

this is a critical time for
young animals, too.

They've grown up through summer's
good times and now they must start

learning to fend for themselves.

For some, it's a steep learning
curve.

This Grey seal pup on the coast of
Norfolk is only two weeks old,

but his mother is already teaching
him to swim.

In another week, she'll be off

starting another family and
the pup will

have to face winter completely
on his own.

In North America, grizzly bear cubs

stay with their mother for
two years,

but it's never too early to start
tackling your first fish.

These young stoats in a
British meadow

have only one summer to grow up.

By autumn, they have to have learned
the art of hunting for themselves.

The stalk...

the chase...

the ambush - deadly skills all
learned through play.

These young animals rush towards
independence

as the world changes around them.

But for some,

the shifting of the seasons brings
unexpected advantages.

In the northern hemisphere,
as the days shorten,

the trees are almost bare.

With less life and
the temperature dropping,

the leaves can no longer
produce food.

So the trees get rid of them.

Nearer the equator, autumn is
the beginning of the dry season.

The leaves are falling, but it's not
because of lack of light.

There's not enough water.

Zimbabwe in southern Africa.

The trees are getting ready for
seven months with no rain.

Trees lose moisture through
their leaves

so it's better to drop them now.

And that's a great opportunity for
two young cheetah cubs just on

the brink of adulthood.

These sisters are 18 months old
and they are ready to leave home.

But first, they must learn how to
hunt,

and autumn is the perfect time to
practice.

With fewer leaves on the trees,
their prey has nowhere to hide.

They pick out a target.

GRUNTING

A male impala is tricky prey,

but they've spent weeks fighting
during the autumn rut.

They're exhausted

and visible.

The cheetah sisters
have their chance.

They'd usually hunt in the open.

When they're hunting among trees,

it'll be more about agility
and speed.

If they can start their chase
close to the impala,

they'll have a better chance of
running him down.

But they'll need to work together.

The sisters creep as close as
they dare.

The trap is set.

But she loses her stride and
the impala gains ground.

That's when her sister makes her
move.

This is a dangerous moment.

As long as the impala is still
on his feet,

he could inflict
some serious injuries.

But the young cheetahs deliver
the killing bite.

With this first success,
they've entered adulthood.

By next autumn, they'll be experts.

For some animals, the race to
independence

takes place in one of the most
hostile places on Earth.

This is autumn in Antarctica.

The snow is already falling

and temperatures are plunging to
minus 20 degrees centigrade.

A colony of Adelie penguins

is rushing to get their chicks to
adulthood.

They only have a few weeks before
winter is back in full force.

The chicks are only three weeks old.

Their downy coats aren't waterproof,

so they huddle together
to keep warm,

while their parents are out at sea.

They may be gone for days...

and the chicks can hardly wait for
them to come back

with something to eat.

The adults work round the clock to
keep their ravenous chicks fed.

When they return,
it's an excited dash for food.

SQUAWKING AND CHITTERING

There are two chicks in
these families,

but there's probably only enough
food for one.

Most Adelie couples only manage to
raise a single chick in a season.

In a place like this...

there's just not enough
for everyone.

Meanwhile, chick number one is
getting bigger by the day.

He'll pack away 30kg of food
while he's growing up.

A month on, and the chicks are
losing the last of their baby down.

Now they have their feathers, it's
time for their next rite of passage.

The adults go first.

They make it look effortless.

But the chicks don't seem so sure.

Apparently, penguins aren't born
with a love of water.

Even when they're in, they're having
problems staying submerged.

They're going to have to practice
their buoyancy control.

They might seem awkward,
but they're just about ready.

Now they'll drift off with
their parents,

out into the Southern Ocean,

where they'll spend the next five
months

fishing and avoiding the worst of
the Antarctic winter.

As autumn moves on, changing ocean
currents

can bring a wealth of food
to some parts of the world.

And off the coast of South Africa,

there is a perfect opportunity for
one animal

to make a spectacular leap into
adulthood.

Bird Island, the world's largest
colony of Cape gannets.

The parents have been feeding
their young for three months.

Now it's time the chicks learned to
fend for themselves.

But first, they must learn how
to fly.

They flap their wings to build up
muscle strength.

Gradually, they lift themselves off
the rocks.

Some are up and away first time.

Others end up floundering in
the breaking waves.

But they all have to make the leap.

The fledglings leave the nest

with enough fat reserves to last
only ten days.

So now, they need to learn how
to fish.

Fast.

Luckily for them,
as winter approaches,

the seas are about to fill
with food.

Billions of sardines are moving in,

following seasonal currents of
cold water,

running along
the South African coast.

The young gannets have mastered
their wings

and they've joined the hunt.

They're following a super pod of
dolphins,

who are also chasing the sardines.

The dolphins drive the shoal to
the surface

and round them up into a ball.

And the gannets make their move.

They climb to 30 metres above
the surface

and plunge into the feast.

They hit the surface at 60mph.

So they must enter the water with
their bodies perfectly streamlined.

Get it wrong and it's like hitting
concrete.

For the young gannets, it's a skill
they have to master first time.

These birds have had a steep
learning curve.

Chasing the seasonal bounty

has given them a dramatic start
to adulthood.

Life has one chance to take
advantage of autumn's opportunities.

It's a race against the clock

to prepare for the challenges of
winter.

Battles for partners are over.

Migrants have escaped the cold.

And young animals have learned what
they need to know

to begin their adult lives.

Autumn's survivors are ready.

The world is changing.

There's a chill in the air and the
last leaves are caught up in frost.

For a chipmunk,

winter won't be such a hardship.

With a full store of nuts...

he can rest easy

until spring.

In Yellowstone, the waterways are
starting to freeze over.

CRACKING

But the beavers are still active.

Their underwater lodge is
well insulated, and inside

there's a young family depending on
the hard-earned larder of branches.

On Alaska's frozen tundra,
the musk ox are toughening it out.

For the pregnant females, it
will be a game of endurance,

as they wait until spring,
when their calves will be born.

As winter takes over, autumn's glory
is finished for another year.