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[somber cymbal crash]

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[David Attenborough] In 2021,

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the world watched as a family
of wild Chinese elephants slept,

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exhausted after an epic
400-kilometer journey.

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[poignant music playing]

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Forced from their ancestral forests

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by the worst drought on record,

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the family had gone in search
of a new home.

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[music becomes hypnotic]

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Having traveled
through huge swathes of farmland,

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there was still no sign of them stopping.

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But what they did next surprised everyone.

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[music climaxes, fades out]

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Crossing under a five-lane highway,

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the family approached the city of Kunming.

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[elephant growls]

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[siren in distance]

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[dog barking]

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Within days,

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the elephants had reached the city limits.

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[elephant roars]

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[sirens wailing]

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And they quickly found themselves
in a frightening new world.

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[elephant trumpets]

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[horn honking]

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[siren wails]

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[elephant roars]

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[elephant growls]

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Scared and disorientated,

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the family had no choice

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but to turn around
and begin the long march home.

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[poignant music playing]

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Remarkably, despite the damage
they caused,

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the elephants were not just tolerated
by the local people

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but helped,

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with hundreds of thousands of dollars
spent guiding them safely home.

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After almost two years

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and more than a thousand kilometers
on the road,

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the weary caravan
arrived back in the southern forests,

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where the drought had eased.

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Against all odds,

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this part of the family's story
had a happy ending.

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But it showed that when animals are faced
with dramatic change,

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the urge to move away can be overwhelming.

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[music climaxes]

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[music fades out]

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[theme tune playing]

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[music fades out]

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[optimistic music fades in]

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Our planet,
traveling around the sun, is tilted.

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And in January,

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this means it's summer
at the southern end.

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Though, at the bottom of the world,
that isn't always obvious.

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[music fades out]

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[lively string music playing]

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Even in the summer's peak,

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temperatures in Antarctica
barely rise above freezing.

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But with 24-hour daylight,

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there's now just enough warmth
to melt the sea ice around the continent.

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[music climaxes]

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[music becomes livelier]

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And that is important for gentoo penguins,

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who need to reach land in order to breed.

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[music intensifies]

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For the last few weeks,
their lives have been driven

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by a 30-kilometer daily commute

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to their feeding grounds out at sea.

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Now, with bellies full,
they're heading back to their chicks.

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[quacks, trills]

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[quacking, trilling]

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[chirping]

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[chirps softly]

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After a day in the water,

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it takes a while
to get their land legs back.

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-[quirky music playing]
-[squawks]

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[cheeps]

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[squawks]

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Gentoos need rocks free of ice

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on which to lay their eggs
and raise their young.

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So the home straight
is often an uphill waddle

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to the windblown clifftops.

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[music abates]

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[twittering]

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Their chicks hatched eight weeks ago
and are now nearly fully grown.

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In Antarctica's short summer window,

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they're right on target
to fledge before winter returns.

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[quirky music playing]

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The chubbier the chick,
the greater their demand for food.

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[chicks cheeping]

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And some parents
seem reluctant to indulge them.

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-[music accelerates]
-[chirruping]

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But there is value in this behavior.

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By making the chicks work for their meal,

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the adults are able
to assess their strength…

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[incoming chick caws loudly]

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…their stamina,

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and their coordination.

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[chick 1 chirps]

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[chick 2 chirps]

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[music intensifies]

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The prospect of food
entices the chicks down to the water.

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[music stops]

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Though not quite into it.

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It seems that even for a penguin,

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the first step into cold water requires

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a little courage.

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[quacks softly]

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[optimistic music playing]

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But it just takes one to lead

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for others to follow.

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Shallow, sheltered pools are a safe way
of testing their waterproof coats.

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[quacking]

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And with summers so short here,

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they'll need them very soon.

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[wind howling]

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Before long,

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the seas around Antarctica
will be covered by ice once more.

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[ethereal music playing]

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So the young chicks must head
for open water now if they are to feed.

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But they're nervous.

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[caws]

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And for good reason.

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[music becomes menacing]

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Who wants to share the water
with a three-meter leopard seal?

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[squawking softly]

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[snorts]

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And not just one of them.

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But three.

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[warbling]

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Like their namesake,
they hunt by ambushing their prey.

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And gentoo chicks make easy targets.

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[squawks]

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But regardless of the danger,

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the penguins' need to feed is great.

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[frantic string music playing]

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Gentoos are the world's fastest penguins.

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[music becomes sweeping]

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[music becomes dramatic]

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If they can avoid being ambushed,
they have a chance.

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The young penguins
stick together for safety.

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[music abates]

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But in the confusion,
a chick becomes separated.

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It's now one-on-one.

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[music reprises]

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[music intensifies]

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[music intensifies]

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[music intensifies]

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[music abates]

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The penguin's only hope

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is to rely on its great agility
and stamina.

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So the longer the chase,
the better its chances.

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[music reprises]

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[music climaxes]

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[music rapidly fades out]

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[gentle classical music fades in]

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This very lucky young penguin
can now join the others.

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And the open ocean awaits.

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[music fades out]

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[ambient music playing]

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[music fades out]

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[insects chirping]

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In February,

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the northern end of the planet
points away from the sun.

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-[hypnotic music playing]
-[star whooshes]

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[star whooshes]

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So in the Arctic midwinter,

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darkness is almost continuous,

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with the only light
coming from the aurora.

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[music becomes spiritual]

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These ethereal displays are created

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as electrically charged particles
from the sun

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collide with the Earth's magnetic field.

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This is the time when countless animals
begin their long journeys

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to these northern regions.

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[music fades out]

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[chirping]

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Five thousand kilometers to the south,

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snow geese have just started
their annual migration.

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[optimistic music playing]

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[quacking]

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Led by the older, experienced adults,

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they follow the thaw
as it spreads northwards.

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00:12:14,024 --> 00:12:16,402
And fly from the Gulf of Mexico

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to their breeding grounds in the Arctic.

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They will reach the tundra

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just as the long days of summer
create the perfect conditions

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in which to raise their chicks.

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[music intensifies]

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They use natural landmarks,
like lakes and rivers,

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to prevent them straying off course.

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But today,

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the world beneath them is very different

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from the one over which
their ancestors flew.

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Where there was once endless savanna,

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there's now industrial farmland.

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[chorus of squawking]

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[music ends]

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But that is not necessarily a bad thing
for the geese.

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To reach the Arctic,

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the flocks need to refuel regularly
along the way,

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so the fields
of America's breadbasket country

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have become vital pit stops.

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[hypnotic music playing]

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This near-endless supply of food

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has meant that the snow geese population

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has doubled in the last 50 years.

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00:13:48,619 --> 00:13:53,290
But there's a cost to becoming
one of the world's most numerous goose.

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[squawking]

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[squawking stops]

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00:14:02,049 --> 00:14:06,387
Not everything in this modern world
is as it seems.

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-[tense music playing]
-[metallic ticking]

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[squawking]

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00:14:26,407 --> 00:14:27,783
[music intensifies]

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00:14:33,330 --> 00:14:34,790
-[gunshot]
-[music fades out]

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00:14:34,874 --> 00:14:38,127
A quarter of a million are shot each year.

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[stillness]

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00:14:44,258 --> 00:14:45,926
[jaunty music fades in]

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00:14:46,010 --> 00:14:51,181
Snow geese have to run the gauntlet
of hunters along much of their route.

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00:14:51,265 --> 00:14:55,728
But sandwiched between
two of America's migratory flyways

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lies a patch of wetland,
where they're protected.

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[music intensifies]

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00:15:05,696 --> 00:15:07,823
Missouri's Loess Bluffs.

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00:15:10,034 --> 00:15:12,703
It's one of the most important
stop-off points

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on their long journey north.

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00:15:14,705 --> 00:15:16,290
[chorus of squawking]

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00:15:17,124 --> 00:15:20,169
How long they will stay
depends on the weather.

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00:15:25,382 --> 00:15:28,719
In February, icy winds blowing down
from the Arctic

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can cause temperatures to suddenly fall.

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00:15:38,354 --> 00:15:40,147
And if it's freezing here,

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conditions will be far worse
where they're headed.

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00:15:45,819 --> 00:15:49,698
So, for now,
all flights north are suspended.

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[quirky music playing]

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00:15:57,957 --> 00:15:59,708
They may be snow geese,

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00:16:01,293 --> 00:16:04,254
but they don't seem to be
at home on the ice.

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00:16:04,338 --> 00:16:05,506
[falling goose squawks]

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00:16:14,223 --> 00:16:16,183
With the lake's margins frozen,

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the birds become concentrated
in the center.

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00:16:20,688 --> 00:16:24,108
The busier it gets,
the less room there is for maneuver.

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[chorus of chirping]

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00:16:28,487 --> 00:16:30,739
And that suits another visitor.

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00:16:32,074 --> 00:16:33,826
[menacing music playing]

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00:16:38,038 --> 00:16:40,040
Bald eagles come here…

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[screeching]

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00:16:41,500 --> 00:16:43,502
…from across North America.

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00:16:45,629 --> 00:16:50,384
And they time their arrival
to coincide with that of the snow geese.

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00:16:50,467 --> 00:16:52,094
[music becomes unsettling]

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[jarring violins playing]

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[honks]

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00:16:55,556 --> 00:16:57,558
[violins become more frantic]

250
00:17:00,644 --> 00:17:02,396
[music becomes dramatic]

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00:17:06,316 --> 00:17:09,570
The geese are far too big
to be snatched on the wing,

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00:17:09,653 --> 00:17:12,656
so the eagles use
a different hunting strategy.

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00:17:16,285 --> 00:17:19,955
Flying at the flock,
they scare the birds into the air.

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00:17:26,211 --> 00:17:30,049
The tighter the geese are packed,
the better it is for the eagles.

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00:17:31,133 --> 00:17:32,551
[music intensifies]

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00:17:44,938 --> 00:17:48,067
In their panic,
geese collide with one another,

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00:17:48,817 --> 00:17:50,694
and limbs are broken.

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00:17:52,988 --> 00:17:55,949
Injured birds are left high and dry
on the ice

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00:17:57,159 --> 00:17:59,620
or unable to escape underwater.

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00:17:59,703 --> 00:18:00,704
[music stops]

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00:18:04,792 --> 00:18:05,834
[eagles squawk]

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00:18:06,460 --> 00:18:11,757
All will remain vulnerable
for as long as this cold snap lasts,

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00:18:12,591 --> 00:18:16,887
their onward migration
still blocked by ice and snow.

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00:18:22,810 --> 00:18:24,645
[ambient music fades in]

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00:18:26,063 --> 00:18:30,234
Back in the Arctic,
the sun is slowly beginning to strengthen.

266
00:18:32,361 --> 00:18:33,737
But in late February,

267
00:18:33,821 --> 00:18:36,824
its rays still barely show
above the horizon.

268
00:18:39,034 --> 00:18:42,162
In such frigid conditions,
there's little to eat,

269
00:18:42,246 --> 00:18:44,957
and most animals retreat southwards

270
00:18:45,040 --> 00:18:46,959
or shut down altogether.

271
00:18:54,007 --> 00:18:56,260
But this one does neither.

272
00:18:57,886 --> 00:19:01,807
A lynx, the most northerly cat
in the world.

273
00:19:03,559 --> 00:19:05,394
[music becomes ethereal]

274
00:19:08,647 --> 00:19:12,568
It's well protected from the cold,
so it doesn't retreat.

275
00:19:15,654 --> 00:19:20,033
But it may have to travel
huge distances to find food.

276
00:19:23,829 --> 00:19:25,664
[music becomes hypnotic]

277
00:19:28,125 --> 00:19:30,002
One was even recorded

278
00:19:30,085 --> 00:19:33,881
walking more than 3,000 kilometers
in just one year,

279
00:19:35,382 --> 00:19:37,593
further than anyone thought possible.

280
00:19:47,311 --> 00:19:52,649
This cat relies almost entirely
on just one kind of prey.

281
00:19:54,401 --> 00:19:58,030
And right now, there are very few around.

282
00:19:59,406 --> 00:20:00,866
[sinister music playing]

283
00:20:02,367 --> 00:20:04,119
Snowshoe hares.

284
00:20:09,583 --> 00:20:12,461
Spotting one is only half the challenge.

285
00:20:13,837 --> 00:20:15,631
[music becomes dramatic]

286
00:20:26,767 --> 00:20:28,018
[music fades out]

287
00:20:28,101 --> 00:20:29,311
[purring]

288
00:20:31,271 --> 00:20:33,190
[soft whimsical music playing]

289
00:20:35,692 --> 00:20:36,526
[purrs]

290
00:20:36,610 --> 00:20:39,988
Lynx need to eat every few days,

291
00:20:40,072 --> 00:20:42,074
so his search never ends.

292
00:20:56,129 --> 00:20:57,214
He's in luck.

293
00:20:57,297 --> 00:20:58,257
[sniffs]

294
00:20:58,340 --> 00:21:00,801
He has detected another scent.

295
00:21:00,884 --> 00:21:02,386
[music becomes tense]

296
00:21:10,560 --> 00:21:12,646
[in hushed tone] The hare holds its nerve

297
00:21:14,439 --> 00:21:16,733
and trusts its camouflage.

298
00:21:20,320 --> 00:21:23,573
The lynx can't outpace his prey
over a long run,

299
00:21:23,657 --> 00:21:25,742
so he needs to get close.

300
00:21:41,717 --> 00:21:44,052
[music becomes dramatic]

301
00:21:44,136 --> 00:21:45,429
[music climaxes]

302
00:21:45,512 --> 00:21:47,097
[music ends]

303
00:21:47,180 --> 00:21:49,182
A meal at last.

304
00:21:53,478 --> 00:21:55,230
[ambient music playing]

305
00:21:58,984 --> 00:22:00,902
[music becomes optimistic]

306
00:22:00,986 --> 00:22:04,448
As the Earth's Northern Hemisphere
tilts back towards the sun,

307
00:22:04,531 --> 00:22:07,117
bringing the longer days of March,

308
00:22:07,617 --> 00:22:11,413
pronghorn antelope
start their annual migration.

309
00:22:16,918 --> 00:22:20,964
Their journey will take them
from the snowy plains of southern Wyoming

310
00:22:21,048 --> 00:22:24,468
to the lush valleys
of the Rocky Mountains,

311
00:22:24,551 --> 00:22:26,178
where they will give birth.

312
00:22:27,888 --> 00:22:29,181
[music fades out]

313
00:22:30,432 --> 00:22:31,600
[snorting]

314
00:22:34,353 --> 00:22:38,440
But today, their path has changed
beyond recognition.

315
00:22:40,150 --> 00:22:44,571
And to start with, they have to find a way
through oil and gas fields.

316
00:22:46,365 --> 00:22:47,866
[sprightly music playing]

317
00:22:47,949 --> 00:22:49,785
A male tries his luck.

318
00:22:53,663 --> 00:22:55,040
[music intensifies]

319
00:23:03,882 --> 00:23:04,925
[music abates]

320
00:23:05,717 --> 00:23:06,718
[snorts]

321
00:23:06,802 --> 00:23:09,012
Pronghorn are cautious,

322
00:23:09,763 --> 00:23:12,474
especially when encountering humans.

323
00:23:14,434 --> 00:23:16,937
[woman speaking over two-way radio]

324
00:23:21,608 --> 00:23:23,610
[pipe clanking softly]

325
00:23:27,864 --> 00:23:29,991
[tense music playing]

326
00:23:30,617 --> 00:23:32,411
[in hushed tone] So far, so good.

327
00:23:33,537 --> 00:23:35,747
Now for the rest of the herd.

328
00:23:39,292 --> 00:23:40,127
And…

329
00:23:41,002 --> 00:23:41,837
go!

330
00:23:42,337 --> 00:23:43,880
[dramatic music playing]

331
00:23:52,931 --> 00:23:54,307
[music fades out abruptly]

332
00:23:55,642 --> 00:23:57,394
Over the next couple of months,

333
00:23:57,477 --> 00:23:59,438
they will travel 200 kilometers

334
00:23:59,521 --> 00:24:02,190
to reach their calving grounds
in the north.

335
00:24:03,316 --> 00:24:07,028
A journey that gets
more challenging every year.

336
00:24:11,116 --> 00:24:14,119
Fences that were designed
to keep livestock in

337
00:24:14,202 --> 00:24:18,206
are equally effective
at keeping pronghorn out.

338
00:24:18,290 --> 00:24:19,958
[moos loudly]

339
00:24:21,626 --> 00:24:23,753
[horse whinnies, snorts]

340
00:24:28,508 --> 00:24:30,177
[dog barking]

341
00:24:33,472 --> 00:24:36,183
But this is the route
their ancestors took,

342
00:24:37,017 --> 00:24:38,477
so they persevere.

343
00:24:38,560 --> 00:24:40,312
[Western music playing]

344
00:24:41,855 --> 00:24:42,814
[moos]

345
00:24:45,984 --> 00:24:47,360
[music intensifies]

346
00:24:52,741 --> 00:24:57,621
Recently, one pronghorn
crossed nearly 150 fences…

347
00:24:57,704 --> 00:24:58,580
[snorts]

348
00:24:58,663 --> 00:25:00,373
…on its migration north.

349
00:25:02,417 --> 00:25:04,336
[music becomes rousing]

350
00:25:08,298 --> 00:25:09,674
[music abruptly fades out]

351
00:25:09,758 --> 00:25:12,761
But pronged horns and barbed wire

352
00:25:14,095 --> 00:25:16,723
can be an unhappy combination.

353
00:25:22,020 --> 00:25:25,232
And fences are far from the only problem.

354
00:25:25,315 --> 00:25:26,942
[dramatic Western music playing]

355
00:25:30,237 --> 00:25:34,324
More perilous are the highways
that now cut across their path.

356
00:25:39,454 --> 00:25:40,956
[horn blares]

357
00:25:49,047 --> 00:25:50,924
-[brakes shriek]
-[music abates]

358
00:25:51,007 --> 00:25:54,469
They may be the fastest land animal
in the Americas…

359
00:25:55,303 --> 00:25:56,513
[music reprises]

360
00:25:58,473 --> 00:26:00,767
…but they can't always dodge a car.

361
00:26:03,478 --> 00:26:04,354
[music fades out]

362
00:26:04,437 --> 00:26:05,730
[horn beeps]

363
00:26:05,814 --> 00:26:08,650
The changes brought by the last 200 years

364
00:26:09,192 --> 00:26:13,405
have reduced pronghorn numbers
by over 90%.

365
00:26:16,199 --> 00:26:18,577
But there is some good news.

366
00:26:18,660 --> 00:26:20,829
[poignant music playing]

367
00:26:22,497 --> 00:26:25,333
The pronghorn's loyalty
to ancestral routes

368
00:26:25,417 --> 00:26:30,046
has made it possible to build overpasses
at key crossing points,

369
00:26:30,714 --> 00:26:34,426
and that has almost eliminated
road deaths in the area.

370
00:26:39,222 --> 00:26:44,019
As the herd continues north,
they reach the real wild west.

371
00:26:46,730 --> 00:26:50,483
Here, they must face
not human-made obstacles

372
00:26:50,567 --> 00:26:52,068
but natural ones.

373
00:27:04,956 --> 00:27:07,083
The snow is now melting,

374
00:27:07,167 --> 00:27:10,629
showing that they're on schedule
to reach their calving grounds

375
00:27:10,712 --> 00:27:13,381
just in time to give birth there.

376
00:27:19,763 --> 00:27:20,889
[music climaxes]

377
00:27:20,972 --> 00:27:21,973
[music ends]

378
00:27:22,057 --> 00:27:25,185
But the seasonal changes
also bring problems.

379
00:27:25,935 --> 00:27:31,066
Ahead lies Wyoming's Gros Ventre River,
now swollen with meltwater.

380
00:27:33,401 --> 00:27:36,696
The pronghorn must cross it
to get to their breeding grounds,

381
00:27:36,780 --> 00:27:38,948
but they seem nervous.

382
00:27:39,032 --> 00:27:40,617
[apprehensive music playing]

383
00:27:40,700 --> 00:27:43,244
Not about the river itself

384
00:27:43,328 --> 00:27:46,581
but what predators
may be hiding on the opposite bank.

385
00:27:47,165 --> 00:27:48,416
[bird shrieks]

386
00:28:04,224 --> 00:28:05,225
In the water,

387
00:28:05,809 --> 00:28:09,562
their speed over land
will be of little relevance.

388
00:28:14,901 --> 00:28:17,696
But predators, such as wolves and cougars,

389
00:28:17,779 --> 00:28:20,615
have now been hunted almost to extinction,

390
00:28:20,699 --> 00:28:23,410
so the chances of an attack here are slim.

391
00:28:26,204 --> 00:28:28,915
It's just that
the pronghorn don't know that.

392
00:28:33,920 --> 00:28:36,089
It still pays to be cautious.

393
00:28:37,215 --> 00:28:39,175
[music becomes optimistic]

394
00:28:39,259 --> 00:28:40,677
It's got them this far.

395
00:28:51,730 --> 00:28:53,815
Several weeks after setting off,

396
00:28:54,315 --> 00:28:57,569
they, at last,
reach their breeding grounds.

397
00:28:58,069 --> 00:29:00,947
The fertile valleys
of the Rocky Mountains.

398
00:29:01,698 --> 00:29:03,992
[music climaxes, fades out]

399
00:29:04,075 --> 00:29:06,119
[chorus of insects chirping]

400
00:29:06,202 --> 00:29:08,246
[spiritual music fading in]

401
00:29:08,830 --> 00:29:11,249
Mexico's Baja peninsula

402
00:29:11,332 --> 00:29:14,502
doesn't experience the cold winters
of the north.

403
00:29:16,755 --> 00:29:20,425
So the mild temperatures of its seas
at this time of the year

404
00:29:20,925 --> 00:29:23,595
make it an excellent seasonal retreat

405
00:29:23,678 --> 00:29:27,265
for one of the world's greatest
long-distance travelers.

406
00:29:32,771 --> 00:29:34,522
Gray whales.

407
00:29:40,236 --> 00:29:41,196
It's mid-March,

408
00:29:41,988 --> 00:29:46,242
and six weeks ago,
this female gave birth here.

409
00:29:50,079 --> 00:29:54,000
The sheltered waters
are warm and free from predators.

410
00:29:54,793 --> 00:29:57,003
It's an excellent nursery.

411
00:30:00,381 --> 00:30:03,384
But such perfection comes at a cost.

412
00:30:06,387 --> 00:30:10,975
There's no food for this mother,
and she's been here since December.

413
00:30:14,312 --> 00:30:16,856
So as soon as her calf is strong enough,

414
00:30:16,940 --> 00:30:19,943
she will lead him 8,000 kilometers north

415
00:30:20,026 --> 00:30:23,571
to their feeding grounds
in Alaska's Bering Sea.

416
00:30:25,114 --> 00:30:28,159
The longest migration made by any mammal.

417
00:30:35,583 --> 00:30:38,837
Fortunately, her youngster
is growing fast.

418
00:30:44,717 --> 00:30:47,887
Nourished by more than
200 liters of milk a day,

419
00:30:47,971 --> 00:30:51,099
the one-ton baby is full of energy.

420
00:30:56,729 --> 00:31:01,317
Luckily, Mother knows just the place
for him to let off steam.

421
00:31:01,401 --> 00:31:02,277
[music fades out]

422
00:31:04,320 --> 00:31:05,446
And this is it.

423
00:31:07,031 --> 00:31:09,117
[quirky string music playing]

424
00:31:14,414 --> 00:31:17,834
A shallow sandbar
in the middle of the lagoon.

425
00:31:19,377 --> 00:31:22,463
And it's clearly the place to be.

426
00:31:25,174 --> 00:31:28,094
As the tide rolls in
over the shallow bank,

427
00:31:28,177 --> 00:31:30,346
it creates a gentle current

428
00:31:30,430 --> 00:31:33,600
attracting whales from across the lagoon.

429
00:31:37,478 --> 00:31:40,940
It's the calf's first introduction
to whale society.

430
00:31:41,941 --> 00:31:43,985
And he seems a little shy.

431
00:31:45,653 --> 00:31:48,114
-[bellowing]
-Best stay close to Mother.

432
00:31:51,242 --> 00:31:52,911
[calf chirps]

433
00:31:54,621 --> 00:31:58,249
The sandbar is a good place
to practice the swimming skills

434
00:31:58,333 --> 00:32:00,752
he'll need for the long journey north.

435
00:32:02,795 --> 00:32:05,590
Jellyfish are carried along
with the current,

436
00:32:05,673 --> 00:32:07,926
but he swims against it.

437
00:32:11,179 --> 00:32:15,058
Using it like an underwater treadmill
to build up his stamina.

438
00:32:15,141 --> 00:32:16,643
[bellowing]

439
00:32:24,150 --> 00:32:29,322
Every year, over a thousand gray whales
migrate to this one lagoon.

440
00:32:32,116 --> 00:32:35,078
But not all are females with calves.

441
00:32:38,247 --> 00:32:41,793
Many are large males
that make the long journey here

442
00:32:41,876 --> 00:32:44,087
in the hope of finding a mate.

443
00:32:48,841 --> 00:32:51,761
Females with young
are definitely not interested,

444
00:32:52,470 --> 00:32:55,056
though that doesn't put off
this amorous male.

445
00:33:01,813 --> 00:33:05,483
And swimming away
only seems to encourage him.

446
00:33:15,493 --> 00:33:17,829
Rejection is clearly hard to take

447
00:33:17,912 --> 00:33:21,124
when you've traveled
half the length of the planet to get here.

448
00:33:21,207 --> 00:33:22,792
[somber music playing]

449
00:33:24,544 --> 00:33:28,506
And now, he seems
to take out his frustration on the calf,

450
00:33:28,589 --> 00:33:31,342
forcing him down, away from the surface.

451
00:33:32,010 --> 00:33:33,469
[music intensifies]

452
00:33:39,684 --> 00:33:40,977
[music abates]

453
00:33:41,060 --> 00:33:43,688
Finally, the male gets the hint.

454
00:33:45,231 --> 00:33:47,358
[ethereal music playing]

455
00:33:49,110 --> 00:33:51,863
It's time for the pair to head north.

456
00:33:53,322 --> 00:33:55,199
Since arriving three months ago,

457
00:33:55,283 --> 00:33:58,327
the female has lost
a third of her body weight.

458
00:33:59,746 --> 00:34:03,499
So now she must begin
the long trek back to her feeding grounds.

459
00:34:05,752 --> 00:34:09,047
Her youngster will need luck
to complete the journey.

460
00:34:11,466 --> 00:34:13,926
One in three gray whale calves

461
00:34:14,927 --> 00:34:16,804
never reach their destination.

462
00:34:27,607 --> 00:34:31,402
The Earth's tilt drives all migrations.

463
00:34:31,903 --> 00:34:35,990
But even at the equator,
where the tilt has little seasonal effect,

464
00:34:36,491 --> 00:34:40,745
there are some animals
that are constantly on the move.

465
00:34:40,828 --> 00:34:42,622
[chorus of insects, creatures]

466
00:34:43,289 --> 00:34:45,500
[rapid dramatic music playing]

467
00:34:51,714 --> 00:34:53,049
Army ants.

468
00:34:57,929 --> 00:35:01,974
Every day, each runs the equivalent
of a human marathon

469
00:35:02,058 --> 00:35:03,810
in order to collect food.

470
00:35:04,477 --> 00:35:05,853
[music intensifies]

471
00:35:13,111 --> 00:35:18,491
These particular ants specialize
in capturing the larvae of other insects.

472
00:35:28,000 --> 00:35:29,836
Workers loaded with their prey

473
00:35:29,919 --> 00:35:33,089
are helped to cross gaps
in the leaf litter by others,

474
00:35:33,172 --> 00:35:34,632
forming living bridges.

475
00:35:37,802 --> 00:35:39,095
[music continues]

476
00:35:41,389 --> 00:35:46,811
Trails of pheromones
lead them to their temporary headquarters.

477
00:35:51,899 --> 00:35:52,775
A bivouac.

478
00:35:52,859 --> 00:35:53,693
[music abates]

479
00:35:53,776 --> 00:35:58,531
A nest built entirely
from the bodies of the ants themselves.

480
00:35:59,323 --> 00:36:00,616
[music trails off]

481
00:36:01,909 --> 00:36:03,953
Hidden behind this living wall

482
00:36:04,036 --> 00:36:06,956
lies the control center of the colony,

483
00:36:07,039 --> 00:36:09,667
the queen and her most recent young.

484
00:36:10,877 --> 00:36:14,630
The whole bivouac
has hung here for the last two weeks.

485
00:36:15,131 --> 00:36:17,300
But that is about to change.

486
00:36:19,010 --> 00:36:20,761
[ambient music playing]

487
00:36:31,981 --> 00:36:34,275
Day turns to night,

488
00:36:34,358 --> 00:36:37,278
and a signal ripples through the colony.

489
00:36:40,489 --> 00:36:44,619
A chemical cue
coming from deep within the bivouac.

490
00:36:45,369 --> 00:36:47,371
[high-pitched electronic music playing]

491
00:36:47,455 --> 00:36:48,831
The message is clear.

492
00:36:50,124 --> 00:36:51,876
It's time to move.

493
00:36:51,959 --> 00:36:54,086
[rapid hypnotic music playing]

494
00:36:59,175 --> 00:37:02,011
These little insects have large appetites.

495
00:37:03,429 --> 00:37:06,265
And having cleared the surrounding forest
of living prey,

496
00:37:07,391 --> 00:37:11,187
they must now move
and find new feeding grounds.

497
00:37:16,359 --> 00:37:19,654
Following one of the main foraging trails,

498
00:37:19,737 --> 00:37:22,782
workers transport
the newly hatched larvae…

499
00:37:25,451 --> 00:37:27,703
while soldiers guard the edges.

500
00:37:30,164 --> 00:37:31,415
[music abates]

501
00:37:31,499 --> 00:37:34,710
There could be as many
as half a million ants in this colony.

502
00:37:34,794 --> 00:37:35,920
[music reprises]

503
00:37:36,462 --> 00:37:38,673
And none will be left behind.

504
00:37:41,884 --> 00:37:43,177
[music speeds up]

505
00:37:44,512 --> 00:37:47,056
The reason they proceed
under the cover of darkness

506
00:37:47,139 --> 00:37:48,516
now becomes clear.

507
00:37:49,100 --> 00:37:51,102
[music becomes high-pitched]

508
00:37:54,021 --> 00:37:56,565
The queen herself is on the move.

509
00:37:58,859 --> 00:38:01,737
She's bigger than any other individual.

510
00:38:01,821 --> 00:38:03,406
And for the past two weeks,

511
00:38:03,489 --> 00:38:06,117
she's been laying an egg
every minute or so

512
00:38:06,200 --> 00:38:08,369
and, therefore, unable to travel.

513
00:38:08,452 --> 00:38:09,453
[music abates]

514
00:38:15,293 --> 00:38:18,963
Now, with her reproductive duties
temporarily suspended,

515
00:38:19,046 --> 00:38:22,133
she's able to move
to fresh hunting grounds.

516
00:38:24,093 --> 00:38:28,556
This is the only time she's ever visible
out in the open.

517
00:38:30,808 --> 00:38:34,645
And the queen
is not the army's only important traveler.

518
00:38:37,106 --> 00:38:40,693
In a rare event
that only happens every few years,

519
00:38:41,319 --> 00:38:45,281
supersized larvae appear,
carried by the workers.

520
00:38:47,408 --> 00:38:49,493
[lively hypnotic music playing]

521
00:38:51,329 --> 00:38:54,874
These are the young males
and future queens

522
00:38:54,957 --> 00:38:59,211
who will soon leave this colony
and establish their own dynasties.

523
00:39:06,844 --> 00:39:08,262
[music intensifies]

524
00:39:10,848 --> 00:39:14,685
Before daylight returns,
the army makes camp.

525
00:39:22,360 --> 00:39:27,198
They will continue to travel every night
until they reach fresh hunting grounds.

526
00:39:29,950 --> 00:39:33,662
By then, the queen will be ready
to lay more eggs

527
00:39:33,746 --> 00:39:36,499
and add more workers to her empire.

528
00:39:37,500 --> 00:39:38,417
[music trails off]

529
00:39:39,126 --> 00:39:40,878
[ambient music playing]

530
00:39:45,758 --> 00:39:47,134
Back in the north,

531
00:39:47,218 --> 00:39:49,428
the mother gray whale and her calf

532
00:39:49,512 --> 00:39:52,598
are now four weeks
into their epic migration.

533
00:39:56,477 --> 00:40:00,564
Since leaving, the youngster has put on
over a thousand kilos,

534
00:40:01,440 --> 00:40:04,485
but his mother hasn't eaten for months.

535
00:40:07,655 --> 00:40:09,782
And there is still a lot of ocean to cover

536
00:40:09,865 --> 00:40:13,327
before she can begin
her banquet in the Bering Sea.

537
00:40:15,371 --> 00:40:16,914
[vocalizing]

538
00:40:20,543 --> 00:40:25,423
They keep close to the coast,
using visual cues to guide them.

539
00:40:28,634 --> 00:40:32,179
She's made this journey many times
during the last 30 years,

540
00:40:33,139 --> 00:40:36,225
and a lot has changed
since her first trip.

541
00:40:40,104 --> 00:40:43,607
Still, she doesn't shy away
from human attention.

542
00:40:43,691 --> 00:40:45,025
[men shouting]

543
00:40:49,071 --> 00:40:53,451
And the calf appears
to positively relish the limelight.

544
00:40:57,746 --> 00:40:59,039
[music trails off]

545
00:41:00,332 --> 00:41:04,211
The crowded Californian coast
seems a million miles

546
00:41:04,295 --> 00:41:06,213
from their sheltered bay in Mexico.

547
00:41:07,756 --> 00:41:10,968
And it's only going to get busier
from here on.

548
00:41:17,349 --> 00:41:21,228
Soon, the pair reach
the port of Los Angeles,

549
00:41:21,937 --> 00:41:23,898
the biggest in North America.

550
00:41:31,947 --> 00:41:33,324
[engine chugging]

551
00:41:33,407 --> 00:41:36,619
Nearly 2,000 ships use it every year.

552
00:41:39,955 --> 00:41:44,627
The constant engine noise
disrupts the underwater soundscape,

553
00:41:44,710 --> 00:41:49,298
disorientating the whales
and increasing the risk of a collision.

554
00:41:50,883 --> 00:41:52,092
[vocalizes]

555
00:41:53,344 --> 00:41:58,265
Scores of whales die every year
in ship strikes in these waters.

556
00:41:59,558 --> 00:42:00,809
[music fades out]

557
00:42:01,602 --> 00:42:02,853
[poignant music playing]

558
00:42:02,937 --> 00:42:04,396
This gray whale

559
00:42:04,980 --> 00:42:07,107
was one of the unlucky ones.

560
00:42:13,113 --> 00:42:18,035
Mother and calf have avoided
the busiest shipping lanes.

561
00:42:18,869 --> 00:42:20,579
[music becomes ethereal]

562
00:42:20,663 --> 00:42:24,500
But the most dangerous part of the trip
lies just ahead.

563
00:42:26,877 --> 00:42:28,170
Monterey Bay.

564
00:42:28,712 --> 00:42:31,215
Thirty-five kilometers of open water.

565
00:42:31,298 --> 00:42:32,883
[music intensifies]

566
00:42:32,967 --> 00:42:34,969
[music becomes apprehensive]

567
00:42:39,598 --> 00:42:43,477
Staying close to the shore here
would cost valuable time.

568
00:42:44,520 --> 00:42:45,771
[music becomes menacing]

569
00:42:45,854 --> 00:42:49,650
So she leads her calf
across the deep water of the bay.

570
00:42:51,277 --> 00:42:52,945
But it's a risk.

571
00:42:56,699 --> 00:42:58,701
She knows what's out there.

572
00:43:04,206 --> 00:43:06,750
She goes into stealth mode,

573
00:43:08,127 --> 00:43:10,588
stopping her regular contact calls

574
00:43:10,671 --> 00:43:13,591
and surfacing as infrequently as possible.

575
00:43:15,009 --> 00:43:16,844
[music becomes expectant]

576
00:43:25,060 --> 00:43:25,936
[hushed tone] Orca.

577
00:43:28,522 --> 00:43:29,690
Killer whales.

578
00:43:31,442 --> 00:43:33,152
They know these waters well,

579
00:43:34,153 --> 00:43:36,071
and they are on the hunt.

580
00:43:36,614 --> 00:43:38,449
[music becomes dramatic]

581
00:43:49,710 --> 00:43:51,712
[vocalizing]

582
00:43:59,261 --> 00:44:00,638
[music intensifies]

583
00:44:03,932 --> 00:44:04,975
[music abates]

584
00:44:05,059 --> 00:44:06,393
[birds squawking]

585
00:44:07,478 --> 00:44:10,356
Mother and calf have been discovered.

586
00:44:14,068 --> 00:44:18,030
An adult gray
weighs ten times as much as an orca

587
00:44:18,113 --> 00:44:20,574
and can be a formidable opponent.

588
00:44:22,618 --> 00:44:26,497
So the pod circle warily,
looking for a chance.

589
00:44:26,580 --> 00:44:28,415
[menacing music playing]

590
00:44:32,503 --> 00:44:33,754
They don't want her.

591
00:44:35,422 --> 00:44:37,049
They want her calf.

592
00:44:37,132 --> 00:44:39,051
[unsettling music playing]

593
00:44:39,134 --> 00:44:41,220
[urgent string music playing]

594
00:44:44,556 --> 00:44:46,392
[dramatic music playing]

595
00:44:52,272 --> 00:44:53,774
[music intensifies]

596
00:44:58,654 --> 00:45:02,282
They surge up onto his back
and force him underwater,

597
00:45:02,366 --> 00:45:04,076
trying to drown him.

598
00:45:04,993 --> 00:45:06,578
[music becomes somber]

599
00:45:10,374 --> 00:45:12,376
[music gradually getting higher]

600
00:45:16,046 --> 00:45:17,506
[music abates]

601
00:45:17,589 --> 00:45:19,007
Supported by his mother,

602
00:45:19,091 --> 00:45:21,593
he has survived the first attack.

603
00:45:21,677 --> 00:45:23,470
[poignant music playing]

604
00:45:26,181 --> 00:45:27,266
[music abates]

605
00:45:28,559 --> 00:45:30,310
But he's been wounded.

606
00:45:30,894 --> 00:45:32,271
[unsettling music playing]

607
00:45:32,354 --> 00:45:33,856
[music becomes tense]

608
00:45:34,606 --> 00:45:37,901
And now, the pod
call in their reinforcements.

609
00:45:41,488 --> 00:45:43,991
A massive five-ton male.

610
00:45:54,042 --> 00:45:55,461
[music intensifies]

611
00:45:56,295 --> 00:45:57,337
[music abates]

612
00:46:00,632 --> 00:46:02,718
Bolstered by this extra muscle,

613
00:46:02,801 --> 00:46:05,512
the orca switch to an all out attack.

614
00:46:16,940 --> 00:46:18,817
There's little the mother can do.

615
00:46:21,487 --> 00:46:23,238
At full ramming speed,

616
00:46:24,364 --> 00:46:26,325
it's like being hit by a bus.

617
00:46:26,408 --> 00:46:29,077
[music climaxes, fades away]

618
00:46:31,580 --> 00:46:33,373
[poignant music playing]

619
00:46:37,628 --> 00:46:40,047
The outcome is inevitable.

620
00:46:52,810 --> 00:46:57,105
This mother will have to continue
her journey alone.

621
00:47:05,072 --> 00:47:06,406
[music fades out]

622
00:47:06,490 --> 00:47:08,116
[optimistic music fades in]

623
00:47:08,200 --> 00:47:09,535
For many animals,

624
00:47:10,369 --> 00:47:13,497
the instinct to move is overwhelming,

625
00:47:14,665 --> 00:47:16,416
despite the dangers.

626
00:47:18,710 --> 00:47:20,921
But for every trip that ends in tragedy,

627
00:47:21,713 --> 00:47:24,424
countless millions
reach their destination.

628
00:47:24,508 --> 00:47:26,176
[music becomes hypnotic]

629
00:47:33,559 --> 00:47:36,687
Allowing them to reap the rewards
of better conditions

630
00:47:38,230 --> 00:47:39,898
and fresh opportunities.

631
00:47:42,901 --> 00:47:46,405
And these migrations
are crucial for others too.

632
00:47:46,488 --> 00:47:47,906
[music intensifies]

633
00:47:54,371 --> 00:47:57,541
However, we have now changed the planet.

634
00:47:58,292 --> 00:48:00,043
[music becomes poignant]

635
00:48:02,379 --> 00:48:04,506
Cutting off ancestral routes…

636
00:48:06,508 --> 00:48:07,801
[squeaking]

637
00:48:07,885 --> 00:48:11,805
…and impacting even the most remote
corners of the globe.

638
00:48:13,557 --> 00:48:15,100
[chirrups]

639
00:48:16,560 --> 00:48:17,895
But there is hope.

640
00:48:17,978 --> 00:48:19,187
[squawking]

641
00:48:21,565 --> 00:48:24,776
We know more about these journeys
than ever before.

642
00:48:24,860 --> 00:48:26,111
[music continues]

643
00:48:30,616 --> 00:48:31,783
And with our help,

644
00:48:31,867 --> 00:48:36,496
many animals are now overcoming
the challenges of our modern world.

645
00:48:39,041 --> 00:48:40,208
[music becomes rousing]

646
00:48:40,292 --> 00:48:45,547
For a healthy and connected planet,
we must preserve the freedom to move.

647
00:48:50,260 --> 00:48:51,553
And if we do,

648
00:48:51,637 --> 00:48:54,890
the vital journeys
of each and every animal

649
00:48:54,973 --> 00:48:57,392
will continue for years to come.

650
00:49:07,235 --> 00:49:08,654
[music intensifies]

651
00:49:12,449 --> 00:49:14,451
[music climaxes, fades out]

652
00:49:14,534 --> 00:49:15,994
[theme tune playing]

653
00:50:04,167 --> 00:50:06,169
[music crescendoes]

654
00:50:41,413 --> 00:50:42,706
[music fades out]