Our Planet (2019) s02e04 Episode Script

In 2021,
the world watched as a family
of wild Chinese elephants slept,
exhausted after an epic
400-kilometer journey.
Forced from their ancestral forests
by the worst drought on record,
the family had gone in search
of a new home.
Having traveled
through huge swathes of farmland,
there was still no sign of them stopping.
But what they did next surprised everyone.
Crossing under a five-lane highway,
the family approached the city of Kunming.
Within days,
the elephants had reached the city limits.
And they quickly found themselves
in a frightening new world.
Scared and disorientated,
the family had no choice
but to turn around
and begin the long march home.
Remarkably, despite the damage
they caused,
the elephants were not just tolerated
by the local people
but helped,
with hundreds of thousands of dollars
spent guiding them safely home.
After almost two years
and more than a thousand kilometers
on the road,
the weary caravan
arrived back in the southern forests,
where the drought had eased.
Against all odds,
this part of the family's story
had a happy ending.
But it showed that when animals are faced
with dramatic change,
the urge to move away can be overwhelming.
Our planet,
traveling around the sun, is tilted.
And in January,
this means it's summer
at the southern end.
Though, at the bottom of the world,
that isn't always obvious.
Even in the summer's peak,
temperatures in Antarctica
barely rise above freezing.
But with 24-hour daylight,
there's now just enough warmth
to melt the sea ice around the continent.
And that is important for gentoo penguins,
who need to reach land in order to breed.
For the last few weeks,
their lives have been driven
by a 30-kilometer daily commute
to their feeding grounds out at sea.
Now, with bellies full,
they're heading back to their chicks.
After a day in the water,
it takes a while
to get their land legs back.
Gentoos need rocks free of ice
on which to lay their eggs
and raise their young.
So the home straight
is often an uphill waddle
to the windblown clifftops.
Their chicks hatched eight weeks ago
and are now nearly fully grown.
In Antarctica's short summer window,
they're right on target
to fledge before winter returns.
The chubbier the chick,
the greater their demand for food.
And some parents
seem reluctant to indulge them.
But there is value in this behavior.
By making the chicks work for their meal,
the adults are able
to assess their strength
their stamina,
and their coordination.
The prospect of food
entices the chicks down to the water.
Though not quite into it.
It seems that even for a penguin,
the first step into cold water requires
a little courage.
But it just takes one to lead
for others to follow.
Shallow, sheltered pools are a safe way
of testing their waterproof coats.
And with summers so short here,
they'll need them very soon.
Before long,
the seas around Antarctica
will be covered by ice once more.
So the young chicks must head
for open water now if they are to feed.
But they're nervous.
And for good reason.
Who wants to share the water
with a three-meter leopard seal?
And not just one of them.
But three.
Like their namesake,
they hunt by ambushing their prey.
And gentoo chicks make easy targets.
But regardless of the danger,
the penguins' need to feed is great.
Gentoos are the world's fastest penguins.
If they can avoid being ambushed,
they have a chance.
The young penguins
stick together for safety.
But in the confusion,
a chick becomes separated.
It's now one-on-one.
The penguin's only hope
is to rely on its great agility
and stamina.
So the longer the chase,
the better its chances.
This very lucky young penguin
can now join the others.
And the open ocean awaits.
In February,
the northern end of the planet
points away from the sun.
So in the Arctic midwinter,
darkness is almost continuous,
with the only light
coming from the aurora.
These ethereal displays are created
as electrically charged particles
from the sun
collide with the Earth's magnetic field.
This is the time when countless animals
begin their long journeys
to these northern regions.
Five thousand kilometers to the south,
snow geese have just started
their annual migration.
Led by the older, experienced adults,
they follow the thaw
as it spreads northwards.
And fly from the Gulf of Mexico
to their breeding grounds in the Arctic.
They will reach the tundra
just as the long days of summer
create the perfect conditions
in which to raise their chicks.
They use natural landmarks,
like lakes and rivers,
to prevent them straying off course.
But today,
the world beneath them is very different
from the one over which
their ancestors flew.
Where there was once endless savanna,
there's now industrial farmland.
But that is not necessarily a bad thing
for the geese.
To reach the Arctic,
the flocks need to refuel regularly
along the way,
so the fields
of America's breadbasket country
have become vital pit stops.
This near-endless supply of food
has meant that the snow geese population
has doubled in the last 50 years.
But there's a cost to becoming
one of the world's most numerous goose.
Not everything in this modern world
is as it seems.
A quarter of a million are shot each year.
Snow geese have to run the gauntlet
of hunters along much of their route.
But sandwiched between
two of America's migratory flyways
lies a patch of wetland,
where they're protected.
Missouri's Loess Bluffs.
It's one of the most important
stop-off points
on their long journey north.
How long they will stay
depends on the weather.
In February, icy winds blowing down
from the Arctic
can cause temperatures to suddenly fall.
And if it's freezing here,
conditions will be far worse
where they're headed.
So, for now,
all flights north are suspended.
They may be snow geese,
but they don't seem to be
at home on the ice.
With the lake's margins frozen,
the birds become concentrated
in the center.
The busier it gets,
the less room there is for maneuver.
And that suits another visitor.
Bald eagles come here
from across North America.
And they time their arrival
to coincide with that of the snow geese.
The geese are far too big
to be snatched on the wing,
so the eagles use
a different hunting strategy.
Flying at the flock,
they scare the birds into the air.
The tighter the geese are packed,
the better it is for the eagles.
In their panic,
geese collide with one another,
and limbs are broken.
Injured birds are left high and dry
on the ice
or unable to escape underwater.
All will remain vulnerable
for as long as this cold snap lasts,
their onward migration
still blocked by ice and snow.
Back in the Arctic,
the sun is slowly beginning to strengthen.
But in late February,
its rays still barely show
above the horizon.
In such frigid conditions,
there's little to eat,
and most animals retreat southwards
or shut down altogether.
But this one does neither.
A lynx, the most northerly cat
in the world.
It's well protected from the cold,
so it doesn't retreat.
But it may have to travel
huge distances to find food.
One was even recorded
walking more than 3,000 kilometers
in just one year,
further than anyone thought possible.
This cat relies almost entirely
on just one kind of prey.
And right now, there are very few around.
Snowshoe hares.
Spotting one is only half the challenge.
Lynx need to eat every few days,
so his search never ends.
He's in luck.
He has detected another scent.
The hare holds its nerve
and trusts its camouflage.
The lynx can't outpace his prey
over a long run,
so he needs to get close.
A meal at last.
As the Earth's Northern Hemisphere
tilts back towards the sun,
bringing the longer days of March,
pronghorn antelope
start their annual migration.
Their journey will take them
from the snowy plains of southern Wyoming
to the lush valleys
of the Rocky Mountains,
where they will give birth.
But today, their path has changed
beyond recognition.
And to start with, they have to find a way
through oil and gas fields.
A male tries his luck.
Pronghorn are cautious,
especially when encountering humans.
So far, so good.
Now for the rest of the herd.
And
go!
Over the next couple of months,
they will travel 200 kilometers
to reach their calving grounds
in the north.
A journey that gets
more challenging every year.
Fences that were designed
to keep livestock in
are equally effective
at keeping pronghorn out.
But this is the route
their ancestors took,
so they persevere.
Recently, one pronghorn
crossed nearly 150 fences
on its migration north.
But pronged horns and barbed wire
can be an unhappy combination.
And fences are far from the only problem.
More perilous are the highways
that now cut across their path.
They may be the fastest land animal
in the Americas
but they can't always dodge a car.
The changes brought by the last 200 years
have reduced pronghorn numbers
by over 90%.
But there is some good news.
The pronghorn's loyalty
to ancestral routes
has made it possible to build overpasses
at key crossing points,
and that has almost eliminated
road deaths in the area.
As the herd continues north,
they reach the real wild west.
Here, they must face
not human-made obstacles
but natural ones.
The snow is now melting,
showing that they're on schedule
to reach their calving grounds
just in time to give birth there.
But the seasonal changes
also bring problems.
Ahead lies Wyoming's Gros Ventre River,
now swollen with meltwater.
The pronghorn must cross it
to get to their breeding grounds,
but they seem nervous.
Not about the river itself
but what predators
may be hiding on the opposite bank.
In the water,
their speed over land
will be of little relevance.
But predators, such as wolves and cougars,
have now been hunted almost to extinction,
so the chances of an attack here are slim.
It's just that
the pronghorn don't know that.
It still pays to be cautious.
It's got them this far.
Several weeks after setting off,
they, at last,
reach their breeding grounds.
The fertile valleys
of the Rocky Mountains.
Mexico's Baja peninsula
doesn't experience the cold winters
of the north.
So the mild temperatures of its seas
at this time of the year
make it an excellent seasonal retreat
for one of the world's greatest
long-distance travelers.
Gray whales.
It's mid-March,
and six weeks ago,
this female gave birth here.
The sheltered waters
are warm and free from predators.
It's an excellent nursery.
But such perfection comes at a cost.
There's no food for this mother,
and she's been here since December.
So as soon as her calf is strong enough,
she will lead him 8,000 kilometers north
to their feeding grounds
in Alaska's Bering Sea.
The longest migration made by any mammal.
Fortunately, her youngster
is growing fast.
Nourished by more than
200 liters of milk a day,
the one-ton baby is full of energy.
Luckily, Mother knows just the place
for him to let off steam.
And this is it.
A shallow sandbar
in the middle of the lagoon.
And it's clearly the place to be.
As the tide rolls in
over the shallow bank,
it creates a gentle current
attracting whales from across the lagoon.
It's the calf's first introduction
to whale society.
And he seems a little shy.
Best stay close to Mother.
The sandbar is a good place
to practice the swimming skills
he'll need for the long journey north.
Jellyfish are carried along
with the current,
but he swims against it.
Using it like an underwater treadmill
to build up his stamina.
Every year, over a thousand gray whales
migrate to this one lagoon.
But not all are females with calves.
Many are large males
that make the long journey here
in the hope of finding a mate.
Females with young
are definitely not interested,
though that doesn't put off
this amorous male.
And swimming away
only seems to encourage him.
Rejection is clearly hard to take
when you've traveled
half the length of the planet to get here.
And now, he seems
to take out his frustration on the calf,
forcing him down, away from the surface.
Finally, the male gets the hint.
It's time for the pair to head north.
Since arriving three months ago,
the female has lost
a third of her body weight.
So now she must begin
the long trek back to her feeding grounds.
Her youngster will need luck
to complete the journey.
One in three gray whale calves
never reach their destination.
The Earth's tilt drives all migrations.
But even at the equator,
where the tilt has little seasonal effect,
there are some animals
that are constantly on the move.
Army ants.
Every day, each runs the equivalent
of a human marathon
in order to collect food.
These particular ants specialize
in capturing the larvae of other insects.
Workers loaded with their prey
are helped to cross gaps
in the leaf litter by others,
forming living bridges.
Trails of pheromones
lead them to their temporary headquarters.
A bivouac.
A nest built entirely
from the bodies of the ants themselves.
Hidden behind this living wall
lies the control center of the colony,
the queen and her most recent young.
The whole bivouac
has hung here for the last two weeks.
But that is about to change.
Day turns to night,
and a signal ripples through the colony.
A chemical cue
coming from deep within the bivouac.
The message is clear.
It's time to move.
These little insects have large appetites.
And having cleared the surrounding forest
of living prey,
they must now move
and find new feeding grounds.
Following one of the main foraging trails,
workers transport
the newly hatched larvae
while soldiers guard the edges.
There could be as many
as half a million ants in this colony.
And none will be left behind.
The reason they proceed
under the cover of darkness
now becomes clear.
The queen herself is on the move.
She's bigger than any other individual.
And for the past two weeks,
she's been laying an egg
every minute or so
and, therefore, unable to travel.
Now, with her reproductive duties
temporarily suspended,
she's able to move
to fresh hunting grounds.
This is the only time she's ever visible
out in the open.
And the queen
is not the army's only important traveler.
In a rare event
that only happens every few years,
supersized larvae appear,
carried by the workers.
These are the young males
and future queens
who will soon leave this colony
and establish their own dynasties.
Before daylight returns,
the army makes camp.
They will continue to travel every night
until they reach fresh hunting grounds.
By then, the queen will be ready
to lay more eggs
and add more workers to her empire.
Back in the north,
the mother gray whale and her calf
are now four weeks
into their epic migration.
Since leaving, the youngster has put on
over a thousand kilos,
but his mother hasn't eaten for months.
And there is still a lot of ocean to cover
before she can begin
her banquet in the Bering Sea.
They keep close to the coast,
using visual cues to guide them.
She's made this journey many times
during the last 30 years,
and a lot has changed
since her first trip.
Still, she doesn't shy away
from human attention.
And the calf appears
to positively relish the limelight.
The crowded Californian coast
seems a million miles
from their sheltered bay in Mexico.
And it's only going to get busier
from here on.
Soon, the pair reach
the port of Los Angeles,
the biggest in North America.
Nearly 2,000 ships use it every year.
The constant engine noise
disrupts the underwater soundscape,
disorientating the whales
and increasing the risk of a collision.
Scores of whales die every year
in ship strikes in these waters.
This gray whale
was one of the unlucky ones.
Mother and calf have avoided
the busiest shipping lanes.
But the most dangerous part of the trip
lies just ahead.
Monterey Bay.
Thirty-five kilometers of open water.
Staying close to the shore here
would cost valuable time.
So she leads her calf
across the deep water of the bay.
But it's a risk.
She knows what's out there.
She goes into stealth mode,
stopping her regular contact calls
and surfacing as infrequently as possible.
Orca.
Killer whales.
They know these waters well,
and they are on the hunt.
Mother and calf have been discovered.
An adult gray
weighs ten times as much as an orca
and can be a formidable opponent.
So the pod circle warily,
looking for a chance.
They don't want her.
They want her calf.
They surge up onto his back
and force him underwater,
trying to drown him.
Supported by his mother,
he has survived the first attack.
But he's been wounded.
And now, the pod
call in their reinforcements.
A massive five-ton male.
Bolstered by this extra muscle,
the orca switch to an all out attack.
There's little the mother can do.
At full ramming speed,
it's like being hit by a bus.
The outcome is inevitable.
This mother will have to continue
her journey alone.
For many animals,
the instinct to move is overwhelming,
despite the dangers.
But for every trip that ends in tragedy,
countless millions
reach their destination.
Allowing them to reap the rewards
of better conditions
and fresh opportunities.
And these migrations
are crucial for others too.
However, we have now changed the planet.
Cutting off ancestral routes
and impacting even the most remote
corners of the globe.
But there is hope.
We know more about these journeys
than ever before.
And with our help,
many animals are now overcoming
the challenges of our modern world.
For a healthy and connected planet,
we must preserve the freedom to move.
And if we do,
the vital journeys
of each and every animal
will continue for years to come.