All language subtitles for David.Attenboroughs.Galapagos.S01E02.Adaptation.2160p.NOW.WEB-DL.DDP5.1.H.265-RAWR_track3_[eng]

In the vastness of the Pacific,
there's a place unlike any other.

Enchanted volcanic islands
that are home to a remarkable

collection of animals and plants.

Here, evolution is proceeding
at extraordinary speed.

Galapagos.

A place of wonders.

Millions of years ago,

the islands were colonised
by a strange cast of characters.

But to settle in this harsh,
unforgiving landscape,

those new arrivals had to
dramatically adapt their bodies.

Today, revelatory discoveries
are still being made about them.

And from their story,
we can piece together how Galapagos

came to be one of the most diverse
environments on our planet.

It's perhaps surprising that the
Galapagos should have become famous

for its biodiversity,

for the fact is that living
conditions here are very tough.

On the equator, the heat is intense.
There's very little water.

Much of the land is covered
by bare volcanic rock.

And yet,
every species that lives here

is descended from an ancestor
from the continents

that have taken on these conditions
and won.

And the way in which they did so
is extraordinary.

The total land area of the
16 islands and rocky outcrops

that make up Galapagos is less than
half that of Wales.

Yet, for its size,

there are more unique species here
than anywhere else on Earth.

Why should that be?

There are clues hidden
within the landscape.

This crescent-shape strip of cliff,

rising steeply from the Pacific
Ocean, is the island of Tortuga.

And like all the Galapagos Islands,

it's a wonderful place
to see wildlife.

Here and there, there's a sea lion.

Above that, nesting seabirds.

Boobies and Galapagos gulls.

But you only really appreciate
the true character of this island

from the air.

From here,

it's clear that this is the last
fragment of an extinct volcano.

These curving cliffs are all that
remains of what was once

a completely circular crater.

And that's an indication
of something very significant

about all these islands.

They change
with enormous rapidity.

The history of these islands
is very much the same.

Each is born
on the bottom of the sea,

and rises up through the waters
to emerge as a volcano.

(VOLCANO BLASTS)

This is a typical Galapagos island
in its infancy.

But then, after a million years
of eruptions,

volcanic activity ceases.

Two million years
after its first appearance,

the island is approaching
middle age.

It has a moist climate
and is covered by forest.

It begins to sink under
its own weight of ash and lava.

It's battered by erosion,
and after four million years,

it's near the end of its existence.

Low-lying and arid
with little rainfall,

it's surrounded by beaches
of soft sand.

The waves and rain continue
to take their toll,

until all that's left is
a craggy outcrop of rock.

These islands, in geological terms,
are very short-lived.

Today, there are islands
in the Galapagos archipelago

that illustrate every stage
in this history.

The youngest in the west are arid,
black and still breathing fire.

The oldest in the east have
long since ceased to erupt.

But each island provides its
colonists with a range of habitats.

And it's the youngest active islands
that pose the greatest problems

for any animals that
attempt to colonise them.

In the far west of the archipelago
lies Fernandina.

This is the youngest
of the Galapagos Islands.

It's forbiddingly desolate
and inhospitable.

But one animal has colonised
its shoreline.

This creature is a specialist
at surviving in this harsh terrain.

And, in adapting to this place,

it has become like no other animal
on Earth.

Behold the marine iguana.

The ancestors of these iguanas
almost certainly

lived in the jungles
of Central America.

There still today you can see
iguanas in the trees

overhanging the rivers, nibbling
leaves, or on rafts of reeds.

Just occasionally,
some are swept out to sea,

and the vast majority
of course die there.

But just a few, a long time ago,
were fortunate enough to be swept

by a favourable current out
to the ocean and pitched up here.

In their ancestral rainforest
habitat, iguanas are vegetarians.

(IGUANA GROWLS)

Here, they browse on juicy leaves.

But the iguanas that
first appeared in the Galapagos

could find no such things.

So these iguanas, to survive,

had to eat the only kind of leaf
that was available.

Seaweed.

And to get the best of that,

they had to do something
even more radical.

They had to swim.

They even learned to dive.

They acquired the ability to
hold their breath for up to an hour

so that they could swim down
to a depth of 20 metres.

Their claws strengthened,

so they could cling
to the rocks on the seabed.

And under the water, they found
an endless supply of seaweed

which grew in abundance
in the nutrient-rich currents

that flow around the islands.

But that was not all.

Their snouts became flatter
to help them graze.

And their teeth became sharper
to grip the slippery seaweed.

But cold water can be
dangerous for cold-blooded reptiles.

After a few minutes feeding at sea,
the iguanas are seriously chilled

and in urgent need of a warm-up.

And their skin enables them
to get that.

It is black.

Dark objects absorb heat and each
scale in the marine iguana's skin

is like an element
in a miniature solar panel.

Now all a marine iguana needs to do

to bring its body
back up to temperature

is to bask in the hot equatorial
sun for an hour or two.

But eating nothing but seaweed
creates another problem -

too much salt.

The marine iguanas dealt with that
in a very particular way.

They evolved a special gland
in their nose.

They simply sneeze the excess salt
from their blood.

These changes had to happen very
quickly in evolutionary terms

if the iguanas were to survive.

But here,
conditions sometimes change.

And then, even iguanas
struggle to keep up.

Every three to seven years,

the weather becomes very extreme
and irregular.

It's a phenomenon called El Nino.

And it can have a devastating effect
on wildlife.

Evolutionary biologist
Maren Vitousek

has studied the effects of El Nino
on the Galapagos marine iguanas.

She discovered that it decimates
their food.

Pressed as 1.0.

Marine iguanas usually eat red
and green algae, and that algae

dies off completely during El Ninos,
during strong El Ninos.

And it's replaced by a brown algae.

Marine iguanas aren't able to digest
the brown algae,

so they eat it, but it sits in their
stomach, basically in a big lump.

And so you can find iguanas
dead on the beach of starvation

with stomachs full of this brown
algae that they just can't digest.

The marine iguana is worst-affected
of all Galapagos animals

during an El Nino.

As many as 90% of them can perish.

It's bad news for iguanas...

...but good news for scavengers.

And new research has shown that
the iguanas have evolved

a special ability that enables them
to survive the famine.

Their bodies shrink.

They lose not just fat and muscle,
but bone.

The iguanas
can actively reduce their skeletons

over just a few months.

So we saw that the largest animals
were decreasing their body length

by as much as 20%.

And the magnitude of that means
that it can't be simply that they're

changing their cartilage
or connective tissue

or resorbing muscles.

Those things together
count for about 10% of length.

So, instead, 20% of shrinkage really
indicates that it's got to be

the skeleton itself that's
decreasing in length.

This amazing ability to do reabsorb
bone in times of hardship

is unique to these reptiles.

It's most recent discovery
in understanding how marine iguanas

managed to survive on the coastlines
of the youngest Galapagos Islands.

But iguanas were not alone

in adapting
to these desolate volcanic shores.

This is the lava heron.

It's well camouflaged.

It's grey feathers make it
relatively inconspicuous

against the blackened lava rocks.

So, moving stealthily, it
can hunt very effectively.

Its favourite prey
is the Sally Lightfoot crab,

whose striking red shell stands
out against the jet-black lava.

But the adult crabs have
tough shells and sharp pincers

and herons know better
than to attack a full-grown one.

Juvenile crabs will be a much
more attractive prospect.

But they have responded
to the landscape of Fernandina.

They have black shells that
make them far less conspicuous

to prowling herons.

This time, the lava heron

will have to make do
with a really tiny snack -

a Sally Lightfoot hatchling.

On the shorelines
of this infant Galapagos island,

life is tough.

Habitats are limited.

Opportunities are scarce.

But away from the coast,
survival is almost impossible.

There, it's too dry and too hot
for most forms of life.

But, in time, that will change.

As the island ages,

this hostile landscape
will become a little more welcoming.

It will one day
support a rich forest,

full of new places
for animals to live.

This change is driven
by the volcanic hotspot

which brought the island
into existence.

The eruptions continue.

95% of its final bulk
will accumulate

in the next few hundred thousand
years.

By the time the eruptions
have ceased,

it's grown so large
that it has acquired a new power.

It has the ability to create
its own weather.

Humid, oceanic winds
blowing across the Pacific

hit this mountain of lava
and are so forced upwards.

That caused them so that they can no
longer hold their load of moisture,

and it condenses as mist and rain.

And that allows plants to thrive.

Santa Cruz,
in the centre of the archipelago,

is typical of these
middle-aged islands.

(THUNDER RUMBLES)

Its slopes are covered
by a mantle of green.

This might seem to be a forest
of giant trees supporting a rich

population of animals of all kinds.

But, this being Galapagos,
this forest is different.

These plants are not true trees.

Trees tend to have big seeds,

and few of those made it across
the oceans to the Galapagos,

and certainly none up here
into the highlands.

But smaller plants
have smaller seeds.

Some, so small
they can float on the wind.

And one member of the dandelion
family made it up here.

And without competition
from other trees, they grew big.

This, you could say,
is a forest of giant dandelions.

This very special kind of dandelion
is called scalesia.

It's unique to the Galapagos,
and flourishes on the high slopes

of Santa Cruz
and other middle-aged islands.

It's become the host
for a whole community

that could not exist without it.

Because scalesia performs
a conjuring trick that gives life

to the rest of the forest.

There's no ground water
in these thin, volcanic soils,

but the scalesia trees are
tall enough to collect moisture

from the sky -
from clouds and from mist -

and that is sufficient to sustain

a whole community
of plants and animals.

High in the canopy,
mist condenses on the spindly,

crisscrossed branches
of the scalesia.

Water trickles down
their wooded trunks.

Ferns root themselves in the damp
moss that clings to their bark.

The moisture creates conditions
where spiders

and other small creatures can live.

And on the forest floor,
pools appear.

Here, dragonflies thrive and,
once again,

they belong to a species that occurs
nowhere else but here.

But the Galapagos climate
is changeable

and the mists sometimes dry up,

leaving this delicate ecosystem

exposed to the burning
equatorial heat.

Some trees, however, have evolved
a way of protecting themselves.

This tree has developed a mutually
beneficial relationship

with the lichen that grows on it.

The lichen shields the tree
from the sun,

preventing it from getting scorched.

And the tree provides the lichen
with moisture and nutriment.

But if the weather gets really sunny

then the lichen shrivels

and stops taking nutriment
and moisture from the tree

but, at the same time, still
prevents it from getting sunburnt.

And when the moisture returns,
the lichen can grow back.

So, plant and lichen make the best
of the two extremes of climate.

Fresh water anywhere on land
creates opportunities.

But on volcanic islands
like Galapagos,

it gets to some very strange places.

Deep in the rocks beneath
the scalesia forest

there is a network of hundreds
of tunnels called lava tubes.

Here, the species-transforming power
of the Galapagos

is as active as everywhere else.

For scientists like caver Aaron
Addison and biologist Steve Taylor,

these lava tubes are the Galapagos
Islands' new frontier of discovery.

It's difficult to imagine or indeed
believe that there are still

such untouched areas within
a place that's so well-known

as the Galapagos
and so well studied.

But we do find those areas,
and those areas then lead us

to a new species
that are unknown to science,

that haven't been described
by anyone else, ever.

Black volcanic rock
still lies only a few inches down

beneath the forest trees
of Santa Cruz.

It erupted millions of years ago
and flowed down the sides

of the volcano in rivers of molten,
red-hot lava.

As the surface of the lava cooled,

it solidified
and formed a rocky skin.

And when the eruption ceased,
liquid lava continued to flow away,

leaving behind these huge,
empty caverns.

And now, a constant trickle
of life-giving water

drips down into the winding tunnels.

Steve Taylor
is an expert on underground life.

The subterranean world
is full of surprises.

It's just really exciting, cos
these animals are pale and eyeless.

There's no selective pressure
to maintain eyes in a cave,

so they're blind.

And they often have
elongated appendages

so they can either find prey
or avoid prey.

This amblypygid,
half-scorpion, half-spider,

is a predator and a scavenger.

It might seem ungainly, but it's
well adapted to this black habitat.

Eyes are useless down here,
and it's become almost blind.

Instead, it feels its way
through the cave

with great skill and sensitivity.

Two of its eight legs
are greatly elongated

and capable of extending
to twice the length of its body.

This millipede
has lost all its colour.

Why spend precious energy creating
a pigment in a place where

no-one can see it?

Spiders, too, haunt the lava tubes.

And just like the tortoises
and iguanas,

these creatures have evolved
into many different species.

There are 90 of them,
all unique to the Galapagos.

But spiders don't just differ
from island to island.

They do so dramatically,
even within a single lava tube.

Some that have been here
for a long time are blind

and feel their way through the cave.

A few have lost their eyes entirely.

But living just centimetres
from them are more recent colonists,

species that still retain
their eyes.

Such variety in such a small area
seems extraordinary,

but in the Galapagos,
it's almost common.

The huge number of differing
habitats has made Santa Cruz

a centre of biological diversity.

And, as an island ages,
so it develops more habitats.

Now, it's entering its old age.

It's no longer growing.

The sheer mass is too heavy
for the earth's crust to support.

It begins to sink
under its own weight.

And now, the rainwater that has been
falling on it throughout

its middle age begins to carve away
its substance.

So the island becomes smaller,
drier and flatter.

That is what has happened
to Espanola.

It's nearing four million years old.

Its forests have gone.

But it now has a different range
of habitats.

Millions of years of erosion
have created beaches of soft sand.

And they suit some animals
very well.

This is a natural bathing beach
for Galapagos sea lions.

They are just one of the very few
mammal species that are unique

to the Galapagos.

And the beach of an ageing island

provides them with
an excellent nursery.

Here, sea lion pups can suckle
in complete safety.

Though they can be
a little irritating.

And, in a protected cove
close by the beach,

parents can teach
their youngsters to swim.

After a swimming lesson, the beach
is a perfect place to relax.

Sea lions seem to have
an idyllic life,

but there is just one irritant...

(FLIES BUZZ)

...flies.

On younger islands
with rocky coastlines,

sea lions have help to keep
the flies at bay - lava lizards.

(FLY BUZZES)

But on the sandy beaches
of Espanola,

the lava lizards
are nowhere to be seen.

They prefer the nearby rocks,
which are warmer.

So here the sea lions must deal
with the fly problem by themselves.

Espanola's soft sand beaches

are also gratefully valued
by another species -

the waved albatross.

The islands provides
an excellent nesting ground

for these huge seabirds.

With a wingspan
of two-and-a-half metres,

the albatross is so big and heavy

that it has to get up a considerable
ground speed in order to take off.

And that's what the beach provides.

As you might expect, the species
of albatross that lives here

is slightly different from those
found in other parts of the world.

These wavelike patterns on its
neck feathers distinguish it

from all other albatross species.

All albatrosses spend
most of their lives on the wing,

travelling across entire oceans.

But here on Espanola,
the waved albatrosses can nest.

(SQUAWKING)

The isolation of the Galapagos and
the protected soft shingle beaches

of Espanola make this ageing island

an excellent breeding ground
for them.

35,000 settle here each year.

Waved albatrosses are monogamous -
they mate for life.

But how do you find a new mate
or recognise your old partner

in such a crowded colony?

You dance.

(RHYTHMIC SQUAWKING)

The whole performance
can last for nearly an hour.

And it's repeated
several times every day.

Sometimes, a potential rival
steps in to try his luck.

The female in the middle dances
with both enthusiastic males

at the same time.

The reward for the victorious male
is great.

A mate.

And an opportunity
to pass on his genes.

The many habitats of Espanola
and all ageing Galapagos Islands

were created by the erosive power
of sea and weather.

But erosion can have
only one final result.

Destruction.

So, a Galapagos island worn down
by the waves and the weather

eventually reaches
the last stage of its existence.

After millions of years
sustaining life,

all that remains of it above water
is a rocky, curving cliff.

Like Tortuga.

There are many relic islands
like Tortuga in the Galapagos.

Devil's Crown in the south
of the archipelago is even closer

to disappearing altogether
below the waves.

But even in its final days,

a Galapagos island
provides a habitat for some.

Its rock has been turned by erosion
into sediment, and now,

that fertilises the marine life
around its submerged remains.

A ring of coral two metres wide
encircles its dwindling stump.

So, a whole new animal community
develops.

Corals are at its centre.

Bristle worms hide inside them,

occasionally emerging
to browse on passing morsels.

Fish find safety among the branches.

And some of the species, once again,
are unique to the Galapagos.

The reef teems with life.

But the presence of warm water
corals here in the Galapagos seas

is something of a surprise.

Because penguins that need
cold water live here too.

So how can tropical corals
and penguins co-exist?

The Galapagos Islands have
one more trick up their sleeve.

The archipelago lies
at the confluence

of several deep ocean currents.

And that creates a bizarre
mixture of marine habitats.

The subantarctic Humboldt Current
flows around the islands

and chills the water just enough
for the penguins to survive.

The corals can't grow
in such cold water

but they can go into a state of
semi-hibernation for short periods.

When warm water from
Central America is dominant,

the temperature
rises by about seven degrees.

Now the corals can grow...

...and the penguins can find refuge

in the few remaining pockets
of cold water in the coves and bays

that still remain.

So, even in the last stages
of its life,

a Galapagos island can support
a rich animal community.

But remarkably, even this
is not the end of the story.

Because even when an island totally
disappears beneath the waves,

it continues to influence life
in the surrounding seas.

The remains of ancient
Galapagos islands

stretch for hundreds of miles
across the Pacific seabed.

These were once volcanoes
like Fernandina,

vegetated mountains like Santa Cruz

and low-lying nurseries
like Espanola.

Today,
those environments are long gone,

but the remnants of the islands
under the sea are still key

in the lives of one of the ocean's
most magnificent inhabitants.

Up to 12 metres long,
it's the largest fish in the world.

The whale shark.

Whale sharks come to the Galapagos
in large numbers

at the same time every year.

But why they do so is a mystery.

Marine biologists Alex Hearn
and Jonathan Green have spent

the last five years trying
to solve the puzzle.

If you think about how Galapagos
is formed and how currents work,

the most productive waters
are actually out west,

so you would've thought that if
whale sharks were here to feed,

they'd be out in the west
of the archipelago, and they're not.

They're up north.

So, why are they coming here?
It's clearly not to feed.

What we found out recently is that
it's mainly large, pregnant females.

Are they coming here to give birth?

This may be the pupping ground for
whale sharks. I'm slightly sceptical.

I think we'd have seen juveniles,
and we don't.

So, that brings back the question,
well, then,

if they aren't pupping here
and they aren't feeding here,

why are they coming?

To understand the whale sharks'
migratory patterns,

Hearn and Green attach satellite
tags to the sharks they encounter.

This enables them
to track their movements.

And it's revealing some
extraordinary new facts.

First, the sharks swim
open-mouthed through the rich waters

off the west coast of South America.

Then they continue their journey
westwards to the Galapagos.

But they only spend a few days
at a time in the islands' waters,

before continuing westwards
out into the open ocean.

Nobody has yet proved why
the whale sharks do this,

but Alex Hearn has begun
to formulate some ideas.

I think there are two possibilities.

Firstly, they may be using Galapagos
as a waypoint which directs them

towards their pupping grounds.

The other option is Galapagos may be
providing a service along way,

and that service may be cleaning,

because we do see a lot of cleaning
behaviour from the reef fish,

or it may be a combination
of the two.

The long line of submerged Galapagos
islands could play a central role

in the whale sharks'
extraordinary journey.

It might be that they
serve as signposts

by which the sharks navigate.

If you start looking at
where they're going,

especially the tracks that we have,
along those ridges

and then up to the next ridge
and back down again, it certainly

seems that they're associating with
those ridges for one reason

or another, and that could be
geomagnetism or it could also be

something to do with the biology of
the water column above the ridges,

but certainly something is going on.

From their birth to their death,

the islands have acted like
evolutionary pressure cookers.

From the youngest islands
like Fernandina,

middle-aged ones like Santa Cruz
and the old islands like Espanola...

...they are extremely varied,
with contrasted conditions.

Deserts, rainforests
and polar waters crowded together

in a very small area.

These huge variations have created
a wide range of opportunities

for the few animals
that have managed to reach here.

As they colonised...

...so they adapted.

And consequently, flourished.

That explains many of the oddities
of the inhabitants of these islands.

Including that most fundamental
phenomenon of all -

the appearance of new species.

The giant tortoise is the
very emblem of the Galapagos,

and in their heyday, there were
hundreds of thousands of them.

Not only that,
there were 15 different species

each in its own locality.

But why should there be
so many species

within such a comparatively
restricted area?

In the next programme, we'll look
at the deep geological forces

that can make a single species
produce many,

and turn the Galapagos
into this wonderland.

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