Nature (1982–…): Season 40, Episode 12 - American Arctic - full transcript

The Arctic has always
been the toughest test,

no more so than
in the far corner of Alaska

called the Arctic National
Wildlife Refuge.

Thousands
of caribou face the cold...

the terrain...

and formidable predators
to reach one special place

at just the right time...

a vast, beautiful plain
on the edge of the Arctic Ocean.

Here, they give birth.

This is the story of the last
great land migration

in North America.



And of how every Arctic creature
is now on a daunting journey

from a timeless past
into a vastly different future.

On the top
of the world,

it is still the ice age.

It's northern Alaska in winter.

The temperature drops
to 50 below.

Frozen rivers curl north
from the Brooks Range

and down to a plain
stretching to the Beaufort Sea

and the Arctic Ocean,
now locked in ice.

This vast stretch of white
mountains,

tundra, and icy rivers,

forms one of the world's
most important wildernesses...

The Arctic National
Wildlife Refuge.

It's a home for courageous
creatures from another time.



This wildlife community
will face a year

of difficult decisions.

Hundreds of miles southeast,
bravest of all perhaps,

is a pregnant caribou.

She's part of
the Porcupine caribou herd

and will undertake the longest
annual land migration

on the planet.

In her lifetime, she's likely
to walk the same distance

as a complete circuit
of the globe.

It's December, and the caribou
are waiting,

eating lichen in the twilight.

The journey ahead needs
precise timing.

She'll march through forests,

over mountains, across rivers,

to the coastal plain.

It's a round trip
of almost a thousand miles.

Some 160,000 caribou

will walk from their
wintering grounds

in the Yukon
and Northwest Territories

to their calving grounds
in the Wildlife Refuge.

The Brooks Range
stands in their way,

running parallel to the coast.

The sun sets for the last time
until the New Year.

The only sunlight is reflected
by a wintry moon.

Hundreds of miles above,

solar radiation fires
up the ionosphere,

and the ghostly aurora.

This is a world
of huge planetary

forces in constant flux.

This is nature at its most
spectacular and extreme.

A dawn twilight returns
in January.

Blizzards blast the tundra.

Most animals have left or are
hibernating under the deep snow,

but musk ox remain.

They are loyal to a home range
and won't leave.

They rarely visit the valley.

The snow is too deep,

and they can't dig out
the frozen grass.

Even up here, it's hard work.

Winters seem to be
more erratic recently,

on average more
than eight degrees warmer

than 50 years ago,
which sounds better,

but now there's freezing rain
on top of heavier snowfall.

The caribou are becoming
restless.

Her belly is beginning to swell
with her unborn calf.

She's searching for reindeer
lichen, her winter food.

She's a reindeer
as much as a caribou.

They are the same species.

She digs through snow
like the musk ox.

For a prospective mother,

finding enough food
is her principal focus.

But it's not her only worry.

It's a lone wolf.

The caribou's instinct
is to stay on the move.

Somewhere has to be better
than this.

But migration is not
blind instinct.

It's a series of collective
decisions based on subtle clues

to weather patterns
and journey times.

Every year is different.

The wolf has choices
to make, too.

He can follow the caribou,
but they move fast,

and the journey is too far.

The first birth of spring.

It's not a caribou,

but a newborn musk ox,
a 30-pound baby,

delivered straight
onto the snow.

The family surrounds her,

a protection from dangers
outside their circle.

But within hours,
the calf wants out.

There's a beautiful new world
to explore.

Every calf is precious.

Musk ox were hunted
to extinction in Alaska

in the 1860s,

but were brought back
in the 1930s.

There are now a few thousand
here in Alaska.

A little river gully is a new
adventure for the calf.

Once in, getting back out
is harder.

The mother won't follow.

She doesn't know
how deep the snow is

and could easily get stuck.

She tracks her calf
from the bank.

The calf discovers...

ice.

There's a physical urgency
to find your feet here...

...but perhaps a greater
mental urgency for the calf

to figure out her world.

The patient mother waits...

and her calf finds a way out.

She's got maybe
another two years

looking after this youngster.

The herd of about 15
will protect the calves

and search for food around their
large home range until summer.

The caribou have left
the winter woodland far behind,

and are heading north.

By April,
the snow is starting to melt,

and many rivers run earlier
than a decade ago.

Spring is moving north faster,
and the caribou need to keep up.

The herd heads on for about
a hundred miles,

then will turn west

towards the Arctic National
Wildlife Refuge.

It's the end of April.
They are over halfway.

The mothers will all give birth

within days of
the third of June.

Six weeks to go.

Golden eagles nest
along the route.

They came up from the south

and established territories
in March,

feeding on hares,
ptarmigan, or marmots.

The eagle pair returns to the
same spectacular nest each year.

They are loyal to a site
decided over a decade ago.

But the calendar has changed
a lot since then.

By early May, the chicks
are near fledging,

and the caribou herd
has already passed.

A ground squirrel is breakfast.

It will take a new generation
of eagles

to make the huge adjustment
to the changes unfolding here.

A lone wolf has stuck with
the herd for many miles.

Caribou from a broad area either
side of the Canadian border

are converging
on the same route.

They'll navigate around the
eastern end of the Brooks Range,

about 40 miles
from the Arctic shore.

In a few places,
the route has bottlenecks

around rivers and lakes.

This migration of Arctic caribou
is compared to wildebeest

on the African savanna,
and so the coastal plain

is sometimes called
America's Serengeti.

As the herd funnels
through the foothills

of the Brooks Range,

the wolf briefly gains
an advantage.

The weaker calves from last year
are struggling to keep up.

There's been little time
to stop and eat.

As long as the herd stays
watchful

and maintains a distance,
they're safe.

Caribou are faster.

The wolf is a tactician,

but tactics
are hard if you work alone.

Here is an unparalleled amount
of food on the hoof,

but to this lone wolf, it might
as well not be here at all.

By May, spring has reached the
Arctic National Wildlife Refuge.

Life here has slept under snow
for eight months.

Plovers and redpolls
arrive to nest,

part of a massive
aerial migration.

Millions of snow geese
leave California or Texas

and are on their way
to the Arctic Islands of Canada.

They'll stop off here
on their way back.

Sandpipers are part of
the worldwide event.

Golden plovers set off
from Argentina.

Terns, loons, and songbirds
come from Antarctica

or Africa or East Asia.

Hundreds of species
cross the planet

on their way
to the Arctic north.

A world of birds is heading to
the summer paradise of Alaska.

The golden plover couple have
arranged a nest on the ground,

laid their eggs,
and are raising their chicks.

The parents provide some
protection against Arctic foxes

or predatory birds,

but it's mainly just warmth
under a camouflaged wing.

Once thawed out, the chicks have
to get back to finding food

for themselves.

The mother leaves after
a couple of weeks,

and the father follows a week
or so later.

But the chicks stay longer

and have to find their own way
back to South America.

In the meantime,
the chicks catch insects

for as long as they can,

then come running back
to warm up again.

Their mother knows it's not just
the cold that will get them.

Arctic foxes live in tunnels in
the layer above the permafrost.

The parents returned
a few months ago

from their winter wanderings
in snowy white coats

to give birth
and turn brown for summer.

The cubs were born here
in early May.

Now, a few weeks later,

they enjoy
the remarkably warm days.

They need to grow up fast.

The cubs are already eating meat

and seem constantly hungry.

Ground squirrels
and nesting birds are here

in large numbers
in May and June.

One delivery is not enough
for them all.

The others don't notice
the mother's return

until it's almost too late.

Oh, well.

Dad will be back soon with more.

It's a constant meal service
during days

that never quite seem to end.

Nesting on the ground
is dangerous,

but there is one bird that would
fight off any fox... the jaeger.

Jaeger means hunter in German.

The caribou are beginning
to arrive.

They are tired, hungry,
many are about to give birth,

and they could so easily tread
on a bird's nest.

The jaegers are not going
to let that happen.

They start with some gentle
warnings,

but the caribou ignore them.

Yet the jaegers are fearless.

The caribou mother has come
hundreds of miles,

faced raging torrents,

been jammed by lakes,
escaped wolves,

and now there's
a determined parent bird

that doesn't want
her here at all.

The caribou respond to
the swooping bird ballet

with strange dance
moves of their own.

As more of the herd arrives,

the jaegers battle tirelessly
to keep their eggs safe.

For the birds, and for all life
here, there's little rest.

Even the sun keeps going,

skimming above the horizon
for most of June.

This midnight sun warms
the caribou

as they all finally reach
their destination.

These are their calving grounds,

in the heart of the Arctic
National Wildlife Refuge.

She must arrive precisely,
so that she's in the right place

when, a week to 10 days
after the snow melts,

the sedges and grasses
are at their most nutritious.

Somewhere is a mother
giving birth...

one new calf among 160,000,
anonymous to all but each other.

Almost all the mothers
give birth within a few days.

The calf doubles in size
in two weeks.

The first green flush of sedges
is briefly high in protein

and sugars
and coincides within a few days

of when the calf
needs most milk.

A week or so later, the grass
will become coarser,

bitter, and indigestible.

The caribou slowly spread out,

surfing a wave of melting snow
and growing grass.

The successful flood of energy

transforms
the character of the caribou.

The first people here
feel part of it.

Humans and caribou were created
as one, they believe,

and each still contains
a piece of each other's heart.

To the Gwich'in,
this is the sacred place

where life begins.

It's late June, and paradise
suddenly closes in.

A plague of mosquitoes emerges.

Each one may take just
a drop of blood,

but the warmer summers
favor the insects.

They emerge earlier
and breed faster.

The mosquitoes take
so much blood

and distress the caribou
mothers so much

that the herd spends
the rest of the summer

attempting to avoid them

by searching
for somewhere cooler.

Life becomes a daily
balancing act of finding

food for yourself

and not being food
for mosquitoes.

The consequences of the hotter
summers may be subtle

and complex for the caribou,

but the effects to the north
are much more obvious.

Over the last 40 years,
the decline of sea ice

in the Beaufort Sea

is one of the most
dramatic changes anywhere.

One of the animals affected most
is the polar bear.

During the last ice age,

they would probably spend
all year on the frozen sea.

Since the ice age ended,
polar bears hunted seals

on the Arctic ice
in winter and spring,

and in late summer,
rested on land,

snoozing and living
off their fat.

Nowadays the ice on
the Beaufort Sea is erratic.

It melts faster, and the bears
arrive early and thinner.

By July, they are hunting
for food along the shore.

They're not a huge threat
to the caribou herd.

They are lumbering on land,
and easily overheat.

Years are more variable now,

and polar bears are showing
unexpected flexibility.

They search for smaller prey

and scavenge
or fight over scraps.

The Arctic Refuge
is a safe home,

but there is no refuge
from the outside world.

It's too hot for them.

The July record here is now
85 degrees Fahrenheit.

It's often hardest for a mother.

Polar bear cubs are born
in midwinter.

This coast is one of the most
important onshore denning areas

in North America.

These cubs are almost
two years old

but still need
their mother's milk.

Polar bears have declined
in the southern Beaufort Sea.

There are about half of how many
were here 35 years ago.

These are desperate times.

North Alaska has the largest
oil field in America.

The base at Prudhoe Bay
is next to

the Arctic National
Wildlife Refuge.

It's a stark reminder

of the cause of
the changing seasons.

Pipelines extend south

and cross several caribou
migration routes.

The polar bears search for food
across land

now scarred by oil exploration.

For the caribou,
the green surge is over,

and they are eating willow shrub

and searching for anywhere
cooler and mosquito free.

For some, that means the coast.

Others head south into the
foothills of the Brooks Range.

After enduring the heat of July,
by late August, it's cooler.

A mother and calf turn south,
with the protection of the herd.

Waiting for them is a grizzly.

Grizzlies and caribou
meet each year.

The herd is named after the
Porcupine River they must cross.

The bear's journey here
is equally hazardous.

In summer, grizzlies hunt
all the way to the Arctic Ocean.

The Porcupine caribou herd

is heading south
into the Brooks Range.

Away from the water,
the caribou start to relax.

It's a mistake.

Caribou may be faster than bears
on the open plain,

but they must also
rest the calves.

Grizzlies and polar bears
are almost the same species

and increasingly overlap
and interbreed,

but grizzlies are a more
serious threat to the herd.

The bear has learned
to chase off the mothers

and then search for calves
hiding in the scrub.

He's found two.

In a moment of indecision...

he loses both.

The calf's mother gallops
to his side.

It's a huge victory
after so much hardship.

Though not for the bear.

The journey south crosses
the Brooks Range in fall.

In spring, this route
is blocked by snow,

but now they can return
straight over the mountains.

For the calf, this is his
first taste of the wider world,

with some new characters...
Dall sheep.

They are cousins of bighorns,
little bighorns,

and mountain specialists.

Like musk ox,
they don't migrate,

but they do move around
the mountains looking for grass

and shrubs between the rocks.

The ewes give birth to a single
lamb in late May.

By September, they are all
enjoying the last of the summer.

The mothers gather in flocks
and watch for wolves and eagles.

This is the migration route
south,

familiar to more
than just caribou.

The fledged golden eagle

has been shadowing
the caribou herd south.

As the herd turns east,

the caribou face
the mountains' wolves.

In a small valley,
the herd slows to rest.

A lone female plans her hunt.

She doesn't try to hide.

The mountains
are on her side now.

A calf becomes separated.

To its mother,

almost home, the trek has
lost its meaning, its purpose.

The snow geese arrive here from
the northernmost Arctic islands.

This is an important stopover
on their way back to California,

Texas, and Mexico.

Snow geese numbers have grown
over the last 20 years.

There are now
20 million of them.

In a world of so much decline,

it's good to know
some species are doing well.

The autumn storms
are sweeping in.

The weather changes
very quickly.

Ptarmigans have been caught
in their summer plumage.

They'll turn white to
an out-of-date schedule.

As long as the snow
isn't too deep,

they can feed on willow buds
and birch.

Ptarmigans are here all year.

That makes them a reliable
target for a red fox.

The many eyes of a flock

and their sharp calls
protect them for now.

Red foxes are thriving
in the Arctic

and out-compete Arctic foxes
if the weather is milder.

By October,
the rivers are frozen

and are buried under snow.

The musk ox have to dig
for vegetation again.

The male musk ox
have other concerns.

Before winter arrives,

they must sort out mating rights
to the harem.

The rut started in August

and a clear victor
has yet to emerge.

The musk ox are also related
to bighorn sheep,

but are much bigger.

Males weigh in at 800 pounds,

and their closing speed
is close to 60 miles an hour.

Their skulls are
heavily reinforced

and the brain
protected by fluid.

They back away,
but only to prepare for combat.

On the right, the older waits,

then charges.

There's probably no other animal
on Earth

that could survive this battle.

The winner will now mate
with the herd.

By October,
the land is frozen solid.

Two polar bear cubs
have survived the summer

thanks to their mother.

The sea won't freeze solid
until November,

but some coastal bays and river
estuaries freeze earlier.

It's their playground
while they wait.

On warm days the surface

starts to melt
and becomes slippery

and tides weaken the new ice.

The surface is still fragile.

By midwinter, they'll be
sniffing out seals

in a freezing twilight
far from land.

This is their ice age home
at last,

a timeless scene that leaves
behind a world of change.

Then the ice breaks,
and reality returns.

The sea melts and refreezes

and will melt again
for two frustrating months.

The polar bears of the southern
Beaufort Sea are doing better

than many others
around the Arctic.

The Arctic National Wildlife
Refuge protects the dens,

and mothers have become
expert scavengers.

Their sense of smell is probably
the best of all animals.

And look what they've found.

It's a bowhead whale...
What's left of it.

With unpredictable
winter ice ahead,

this bowhead carcass is
a salvation for the family

and for all the local
polar bears.

They will feed for weeks.

Bowhead whales are increasing,
maybe thanks to longer summers.

Everything is changing,
and everything is connected.

There is regulated whale
hunting here,

and this carcass
has actually been left

on the beach for the wildlife.

For the polar bears,
it's a lifeline,

but maybe little more.

They are ice bears,
evolved in another world.

Across millions of years,
the Earth has seen huge changes

many times.

The most recent was the end of
the Ice Age, 12,000 years ago.

This extraordinary wilderness

protects these Ice Age
survivors...

The polar bears,
musk ox, arctic foxes,

and the spectacular caribou,

holding out
on the top of the world.

Now, even for them,
the ice age may, finally,

be coming to an end.

To learn more about what you've
seen on this "Nature" program,