All language subtitles for The Life of Mammals 7of9 Return to the Water 720p HDTV x264 AAC MVGroup org_Subtitles01.ENG

Nearly all mammals have to go down
to the water to drink.

And even the most unlikely of them
can swim.

You might not think that an elephant
would willingly go out of its depth,

but many do so quite regularly.

Some scientists even believe that
the elephants' ancestors once spent
much of their time in water,

and that their trunk first evolved
as a device to help them
breathe there - as a snorkel.

It's certainly true that elephants
even now are very fond of bathing

and can swim across deep channels.

But there are some mammals
that swim so frequently that water
has become their true home.

Fresh water
contains all kinds of food,

both animal and vegetable,
and mammals of many kinds
have ventured there in search of it.

The desman belongs to that ancient
group, the insect eaters, that were
around in the time of the dinosaurs.

Like its relations the shrews,

it lives on worms and molluscs
as well as insects.

Most shrews
look for such things on land,
but the desman is more adventurous.

And it's
got special underwater gear -

a snorkel. A miniature version
of the elephant's trunk.

It's also got long, dense fur
that keeps it warm in the water.

These two modifications
make it a very effective swimmer,

and its snorkel also serves as a
sensitive probe to help it discover
things to eat on the riverbed.

Even so, its body is very buoyant
and keeping below the surface
is hard work,

so it seldom dives for more
than a few minutes at a time.

And having caught something, it has
to come back to land to eat it.

But hunger has led other mammals
to swim in much bigger
and more hazardous waters -

the seas.

The oceans that cover two-thirds
of the planet are full of food.

So it's hardly surprising that some
mammals have gone there to find it.

These behind me spend their lives
at sea. And these particular ones
spend most of their time feeding.

In fact, in proportion to their size,
they probably have the
biggest appetite of any mammal.

They are sea otters.

The ancestors of otters
were weasel-like creatures -

land-living carnivores
that scampered around on four feet,
had warm blood and breathed air.

Each one of these characteristics
poses a problem for any mammal
that tries to take up swimming.

I can solve them
by putting flippers on my feet,

by wearing an insulated suit
to keep me warm

and putting a snorkel in my mouth
so that I can breathe underwater.

The otter has developed webs
between its toes and in that way
converted them to paddles.

Even the best human scuba diver -
and that's certainly not me -

can't match the sinuous agility
of a sea otter.

Much of the food in the Californian
waters is packed up in hard shells.

To deal with that, the sea otter
collects a stone from the sea floor.

Back on the surface,
it puts the stone on its stomach
and uses it as an anvil.

Sea otters are so good at this
and so energetic

that one can crack open
and eat a quarter of its own weight
in shellfish in a day.

River otters leave the water to mate,
but sea otters are so at home at sea

that they mate here,
bringing a new meaning to
the concept of synchronised swimming.

They don't even
go back to land to sleep.

And how do they prevent themselves
from being carried away
by the current?

They wrap themselves in kelp,
like this one has done.

You might think that it wouldn't
matter very much to an otter

if it did drift a bit while it dozed.

But these kelp forests
are rich feeding grounds,
and sea otters are territorial

and they don't want to leave their
family hunting grounds undefended.

And how does a sea otter deal with
the problem - so crucial for mammals
everywhere - of staying warm?

My dry suit
gives me very good insulation,

but the sea otters' fur
is superb.

It has more hairs in one square
centimetre of its body

than any human being
has on their head.

In fact, sea otter fur
is the densest fur
in the whole of the animal kingdom.

It takes a lot of looking after.
Its efficiency as an insulator
depends on having air trapped in it.

To make sure that it is at its most
effective, sea otters spend a lot
of time blowing into their dense fur.

When an otter dives, some air,
inevitably, is squeezed from its fur.

But even so, enough remains
to keep the otter warm and snug.

Few animals look more at ease on the
surface of the sea than a sea otter.

Their furry wet suit is even
efficient enough to keep them warm
in the frozen waters of Alaska.

But that superb fur
was nearly their downfall.

Human beings prized it so greatly
that they hunted the sea otter close
to extinction. Now, hunting's banned.

There are other sea-going mammals
that fish along these
Pacific coasts of North America -

sea lions.

They may have taken to the water
even before the sea otters,

for their limbs are now even
more extremely adapted to swimming.

Their front legs have become paddles,
their back - broad flippers.

And they have developed
an additional means of insulation.

As well as fur,
they have a specially thick layer
of fat beneath the skin - blubber.

They do, however,
still retain their external ears.

And it's this that identifies them
as sea lions rather than seals.

Even though all four limbs
are flippers,

the front legs are stout enough
to act as props

and the hind can still be pointed
forward to help them walk.

But they still have to come to land
to give birth to their pups.

Beaches, to be suitable
for a sea-lion nursery,

must have a gentle seaward approach
so they aren't battered by waves

and to be on islands or sheltered
coves that are difficult
for land predators to reach.

Such places are not common,

so they're usually crowded,
like this one in New Zealand.

Each patch is dominated
by a big male, a beach master,

who will claim any female who lands
on his patch, and mate with her
as soon as she's given birth.

He keeps a lookout for any other
male who might have the same idea.

HE GROWLS

The females need to
get back to the sea in order to feed,

so they rear their babies as quickly
as possible and provide them with
rich milk - it's about 30% fat.

The baby consumes such quantities
at such speed that the growth of its
bones and muscles can't keep pace.

So, the baby converts some of the
fatty milk into baby fat, blubber,
which takes hardly any time.

But inevitably, this pampered life
will soon come to an end.

It's going to get much tougher.

After a mere three weeks or so,

a mother leads her baby down
for its first swim.

To reach open water, they have
to get through the swirling,
entangling beds of kelp.

Made it at last.

South of New Zealand,
in the Antarctic,

it's so cold
that the sea freezes over.

These are seals, not sea lions.

Both groups seem to be descended
from an early carnivore - something
between a weasel and a bear.

But seals have taken their swimming
adaptation farther than sea lions.

They have
completely lost their small external
ears, which sea lions have retained.

Consequently, their heads are
just that much better streamlined.

And their hind legs have become so
shortened that they can no longer be
pointed forwards to help in walking.

All a seal can do to get around out
of water is to hump its whole body,
or simply slide.

With the surface of the sea frozen,
an expectant mother seal can haul
herself out of the water anywhere.

So, a male can't lord it over harems

and the females are left to produce
their young in comparative peace.

Seal pups here
have a comparatively safe childhood.

The frozen seas around Antarctica

are so far from other continents
that there are no terrestrial
hunters here to threaten the seals.

That is a privilege, and one that
is denied to seal pups elsewhere.

I'm now at the other end
of the Earth - the north, the Arctic.

It may look very much the same
as the Antarctic,
with snowfields and icebergs,

but as far as seals are concerned,
it's crucially different

because land extends north into the
Arctic and there are land predators
that can get out onto the sea ice.

There are tracks of them all here.

These...are the footprints...

..of an Arctic fox.

And foxes prey on new-born seals.

I'm out on
the frozen surface of the sea.

Here, mother seals come up
through holes in the ice

and dig snow caves as a nursery.

The fox whose tracks I'm following
has found it and burrowed into it.

But did it catch the pup?

This...is the surface of the sea ice.

Over there is the hole through
which the female seal came

in order to burrow out this lair.

Here, snug, away from the blizzards
and gales of the Arctic,

she gave birth.

And here, it seems, that
the pup did escape from that fox

for there is no sign of any blood
on the ice.

But there are bigger predators here
than foxes.

Polar bears.

They, too,
are on the lookout for pups.

Ringed seals, at this time
of the year, are their staple diet.

Ringed seal pups can't swim
until they are several weeks old.

Their survival
depends on them remaining undetected
in their nurseries under the snow.

The adults are relatively safe
beneath the ice.

They can stay submerged for 20
minutes, but visit the breathing
holes to prevent them freezing over.

Polar bears have an extraordinarily
sensitive sense of smell.

They can detect the breath of a seal
drifting up from the snow
from over half a mile away.

That could lead them to a pup.

That pounce smashed the roof
of the nursery den and
could have killed the pup outright.

But this pup was already dead.

Its little body is stiff and frozen.

Maybe its mother failed to
keep the entrance hole free of ice

and couldn't get back to feed him.

Several kinds of seals in the Arctic
breed away from land, out on the ice.

Female seals mate
soon after giving birth.

That means they only have to leave
the sea once a year, not twice.

Here, the males have
no chance of assembling a harem,
as they can on a beach.

Instead, each one waits for a female
to become sexually receptive again.

These hooded seals have their
own way of impressing rivals.

It blows up its hood -
a cavity beneath the head skin -

and then inflates a scarlet membrane
that balloons out of its nostrils.

If displays like this aren't enough
to settle a dispute, the males have
to resort to physical violence.

Male harbour seals have
an even stranger courtship ritual,

and one that has been discovered
so recently that its mechanisms
are still not fully understood.

They go in for
competitive choral singing.

One big male, just off the breeding
beach, begins to vocalise.

LOW RUMBLINGS

Others - probably younger ones -
then join him.

THEY ALL MAKE SOUNDS

Eventually, half a dozen
may be singing, holding their heads
together like a barber-shop group.

When a female does appear,
the one who started the performance
swims away with her

while the rest obligingly
wait behind.

Otters, seals and sea lions

are all descended from an ancient
group of hunting mammals that were
tempted into the water to fish.

But they've retained
the character of their ancestors -
they're fierce and aggressive.

But what about
the early plant-eating mammals?

They, too, went into the water
about 35 million years ago,

because there are many water plants,
particularly in shallow fresh water.

They, too, have retained
the character of their ancestors.

They are gentle grazers.

And here, in the warm, clear waters
of the Florida creeks,

they still are. Manatee.

They're so completely at home
in water...

that they never leave it.

Oh, dear...

I suppose a little halitosis is what
you'd expect from all these leaves,

but - phew! - that's a bit strong.

But what were
those vegetarian ancestors?

No-one knows.
Some characteristics, like teeth,
link manatees to elephants.

These, like those of elephants,
are flat, grinding molars.

As they're worn down by the coarse
grass, they're replaced by new ones

that erupt at the back of the jaw
and slowly move forward.

Manatees are so big
that nothing much attacks them.

With plenty of vegetation there
for the taking, there's no need
for them to be swift swimmers.

Their forelimbs have become short
flippers that can be used as paddles

or to gently punt along the bottom.

They still carry nails - vestiges
of their terrestrial past.

Their hind legs have disappeared
altogether, and they propel
themselves on their cruises

with slow, powerful sweeps
of their huge tails.

Their bristly upper lip is so
well muscled that they can use it
to grasp leaves,

rip them up
and push them into their mouth.

They have gentle lives trundling
across shallow submarine pastures.

Their other name is "sea cow",
and very appropriate it is, too.

Manatees live in clear,
sunlit waters.

The plants they feed on only grow
in light, so they have little
difficulty in finding their food.

But other swimming mammals
have a harder time of it.

India, the Ganges.

There are water-living mammals here,
though they're rare and hard to spot.

There's one.

It's a river dolphin.

The trouble with rivers in general -
and the Ganges in particular -

is that they're full of sediment
and very cloudy.

Below the surface, it's impossible
to see more than a few inches ahead.

The water is opaque.
Eyes are no use at all.

And the river dolphin has lost the
use of them. It's completely blind.

How, then,
does it find the fish it feeds on?

It uses sound - electronically.

WE can make a sound
and use a system known as "sonar".

We can send out
very high-pitched sounds from this.

And if that hits their body, it
causes an echo which we will receive

on this monitor.

Let's try.

BEEPING

There they are.

Shoals of fish, somewhere out there
in the murky water.

River dolphins use sound
in exactly the same way.

If I lower an underwater microphone,
we can hear the sounds
THEY are making to locate their prey.

BUZZING

GURGLING

All dolphins exploit sound
when hunting.

But here, on the south-eastern coast
of the United States,
in Georgia and the Carolinas,

there are dolphins that've invented
their own special way of hunting

that seems to be used by no other
dolphins anywhere in the world.

It's daring and it's complicated,
but the birds can predict it.

They're assembling over there,
so that's where
we should point our cameras.

And sure enough, there in the water
in front of them are the dolphins.

They're swimming slowly back
and forth, edging a shoal of fish
closer to the river bank.

And now their tactics
are about to change.

Several dozen little fish were swept
up onto the mud, and the dolphins
are now snapping them up.

The birds are getting quite a lot,
too.

Now, the dolphins
have to wriggle back to water.

Off they go upriver to find
the next suitable place for doing
the same thing all over again.

Once more, the birds show us
where that is likely to be.

But have they got it right?

This daring strategy
depends on a number of things.

First, obviously, teamwork.

And that requires an ability
for the members of the team
to communicate with one another,

which in this murky water
must be done by sound.

But it also requires
a high intelligence...

The high intelligence
needed to plan ahead,
which was more than I managed to do!

They obviously knew that they were
going to come to a safe place,

and one of the keys that tells you
that it's going to happen

is when one of the members of the
team pokes its head out of the water

in order to make sure everything
is safe on the bank.

Synchronisation must be perfect

to create the necessary surge, and
that can only be done by underwater
communication between the team.

And they must all turn the same way.

If two alongside one another were
to turn in different directions,

they would either end up facing one
another, competing for the same fish,

or both turning their backs on those
same fish, allowing them to escape.

Out in the open ocean,

dolphin teams
may number several hundred.

These are common dolphin,

and the speed with
which they are going - wow! -

and the determined way in which
they're travelling, and the fact
that all these birds are soaring

means that they know
there are some fish right over there.

The whole school stretches out on
either side of me for a quarter of
a mile or more in either direction.

They seem to be chasing a shoal of
fish ahead of them, just as those
dolphins were doing in the river.

But this is on vastly greater scale.

They've succeeded in isolating
a huge school of sardines,

and now they're swimming round them,
herding the shoal in upon itself,

forcing it
into one gigantic meatball.

They drive the shoal upwards
so that it will be trapped
against the surface.

And now the moment has come to swim
straight into the meatball

and collect the rewards
for all this effort.

As the sardines
are forced towards the surface,

so they come
within range of sea birds overhead.

There's a water-living mammal
that feeds in a quite different way.

Instead of teeth, it uses baleen -
horny plates
that are hung from its upper jaw

and fringed with long, coarse hairs.

It collects krill - little
shrimp-like creatures, scarcely
bigger than my little finger -

but it finds them in such quantity
that it's become gigantic.

It takes in a great mouthful of
water and krill, then shuts its jaws,

and up comes its tongue.
It's as big as an elephant.

The tongue pulls back,
wipes the krill from the baleen,
and the animal swallows it.

And that krill is so nutritious
that this creature, the blue whale,

is the biggest that has ever
existed on this planet -

almost twice as heavy
as the biggest known dinosaur.

Its vast ribcage houses its lungs.

They carry 2,000 litres of air -

that's 500 times
the capacity of our lungs.

The heart is as big
as a small family car.

It only beats
five or six times a minute,

but it drives
ten tonnes of blood through
a million miles of blood vessels.

And all that is left

of the hind legs and hip bones
are these two isolated fragments,

buried in a mountain of muscle.

I can see its tail,
just under my boat here.

It's coming up...

The blue whale...

is 100 feet long...

30 metres.

Nothing like that can go on land
because no bone is strong enough
to support such bulk.

Only in the sea do you get such huge
size as that magnificent creature.

And down it goes...

The land-living deer-like creatures
that were the ancestors of the great
whales first entered the water

around 55 million years ago.

Since then, their descendents
have evolved ways of solving
all the problems of life at sea.

With one blast from its nostrils,
a whale discharges 90% of the spent
air from its lungs and takes in new.

Most land-living mammals
only manage to void about 15%.

It's able to store oxygen not just
in its blood, but in the tissues
of its vast body.

And so it can stay beneath
the surface for half an hour or more.

It collects food wholesale.

With one sideways gulp, it takes
in a tonne of krill-filled water.

Their ancestors' coat of hair, so
characteristic of all land mammals,
has been completely lost.

Instead, the whale's entire body is
swathed by a blanket of fat beneath
the skin, in places 20 inches thick,

which insulates it against the chill
of the water, no matter the depth.

It has a near-perfect
hydrodynamic shape,

uninterrupted by hind limbs,
ears or genitals.

And as it tilts its hundred-tonne
body downwards,

so it can plunge to the black world
500 feet or more below the surface.

Down in the blue immensities
of the oceans,

where the great whales spend
much of their time, they communicate,
like dolphins, by sound.

BOOMING ECHOES
HIGH-PITCHED SQUEAKING

GRUNTING AND RASPING

Sound travels further and faster
in water than it does in air.

Loud noises can be heard
hundreds of miles away,

so whales may be able to hear the
distant waves breaking on the shore

and use that to find their way
around the otherwise featureless
expanses of the open oceans.

Individuals also call to one another
and may keep in contact even though
they're hundreds of miles apart.

Humpback whales have developed
particularly complex sounds.

They produce deep notes, almost
beyond the range of our hearing.

If you swim alongside them, these
vibrations seem to fill your body

as the low notes of an organ
will throb inside a cathedral.

The more complex notes are directed
to females, inviting them to mate.

All humpback males
in one part of the ocean sing
the same sequence of sounds,

the same song, but each, as he sings,
may repeat the phrases within
that sequence several times.

GRUNTING AND TRILLING

A complete song
may last for half an hour.

Once it's over, the male
may repeat it and continue doing so
over and over again

in a performance
that may last several days.

Off the coast of Patagonia,
southern right whales are assembling.

The males announce their arrival by
gigantic leaps. 100 tonnes propelled
into the air with the flip of a tail.

The sound above water
is like a cannon shot.

Below,
it must be felt for miles around.

These whales show their solution to
the problem for all mammals if they
are to live permanently in the sea -

how to breed in water.

This female
is surrounded by ardent males.

She's not yet ready to mate,

and rolls over on her back
in an attempt to keep her
genital region away from her suitors.

That's not easy when a male is as
formidably equipped as a right whale.

A slit has opened in the male's
underside and a penis protrudes -

12 feet long and highly mobile.

The males barge and jostle one
another to reach her and several
may succeed - one after the other.

Now, seemingly,
the female has changed her mind.

She rights herself
and leaves the surface.
Now she is ready to receive a male.

Male right whales have gigantic
testes, the largest in the world.

They weigh a tonne,
and produce gallons of sperm.

One coupling can flush out
whatever preceded it,

so it may not be the first male who
succeeded in copulating who becomes
a father. It will be the last.

So, some mammals who started out
with four legs and no fins,
with bodies that had to be kept warm

and with an awkward necessity
to breathe air

have managed
to colonise the waters of the world.

We, with the aid of plastic flippers
and compressed air bottles,

managed to follow them
a few decades ago,

but we still have lots to learn
about how they organise their lives.

Given the elusive nature of marine
mammals, it will be many years yet
before their mysteries are solved.

You may wonder how
I was lucky enough to get alongside
that surfacing blue whale.

It was done
using the latest technologies -

a radio tagged on the whales
sent signals up to a satellite
which gives their position.

Then, a low flying aircraft calls a
swift launch. That's how I got there.

That gets scientists there, too,
of course, and it's their job, in
a very short time, to collect data.

To study a mammal that spends the
vast majority of its life underwater
or far out at sea

presents an enormous challenge
for humans.

For marine biologists,
each close encounter
with a huge whale is ample reward.

I've studied blue whales for years,

but I will never forget the
first time I saw one from the air.

I was in a rickety old Cessna,
over the Sea of Cortez in Mexico.

We flew over an adult blue whale
just as it surfaced.

It looked more like a Boeing 737
than a real, wild, living whale.

It was absolutely huge.

Yet despite its size,
the blue whale has remained
surprisingly well hidden from humans.

In August 1986, whale biologist
John Calambokidis

was doing an aerial survey in
a vast area of sea off California

and he made
the most incredible discovery.

He saw a giant amongst humpbacks.
It was blue with a huge blow

and he recognised it
as a blue whale.

Then he saw more and more.

He had discovered the largest known
population of blue whales on Earth.

Research shows that there's about
2,000 blue whales off California.

How they could have gone unnoticed
for so long I don't know, but
it was an extraordinary discovery.

But the key to understanding is
to identify and follow individuals.

Since the early 1970s, scientists
have identified killer whales

using the shape of the dorsal fin.

Similarly, humpback whales
have individual patterns
on their tail fins.

Blue whales proved more of
a challenge, but in the early '80s,

biologist Richard Sears showed that
individual blue whales could be
identified by their mottled flanks.

Now we can recognise over 1,300 of
the whales in the California group.

It's like a human mugshot. Imagine
the CIA files for criminals. This
is the equivalent for blue whales.

You build up catalogues
of an entire population.

This is the bricks and mortar
of blue whale research now.

When the whales
dive out of camera range,

it's still possible to follow them
by listening to their calls.

This, too, is a way
to identify individuals and families.

Surprisingly, the end of the
Cold War brought the next advance.

The US navy used very sensitive
hydrophones to track submarines.

Its operatives had
listened in to whales for decades.

The crux point was in 1993 when
Chris Clark of Cornell University

was given permission to use
this system to eavesdrop on whales.

For whale biologists all over
the world, this was like Christmas
a thousand times over. It was great.

It meant he could listen to one
whale as it crossed an ocean basin.

The first afternoon Chris
and his colleagues listened in

with the help of navy analysts,

they actually heard more blue
whales than had ever been written
about by scientists ever before.

It was mind-boggling stuff.

The latest technology
gives even more detail.

A harmless tag sends biological data
up to a satellite each time
the whale surfaces to breathe.

It provides vital information
for whale biologist Bruce Mate.

There's a low population
of blue whales worldwide now -

we've lost 92% of them to whaling.

With 8% left, and the Californian
coast having 25% of those,

we really need to know
where they go to breed and calve
in the winter to protect them.

We only know
where they are in the summer,

so tagging them here and tracking
them in the winter is important.

Our understanding of whales,
dolphins and other marine mammals

has increased enormously
over recent years thanks to
the researches of marine biologists.

It's THEIR expertise that has
enabled us to get our camera teams
to the right place at the right time.

Nonetheless, filming whales
still poses enormous problems.

Sometimes, it's as simple as
get on a boat, point the camera.

In that case, you're only seeing
them for a small part of their life.

We think that to see the subject
properly, you have to go underwater.

Entering the underwater world
obviously brings up
a whole set of fresh challenges.

For a start, you can't breathe.

A lot of times, marine mammals
live in water which is quite cold -

temperate or polar zones -
so you have to wear a dry suit
rather than a wet suit.

Your extremities, like your hands,
tend to get quite cold,
so we put hot water into our gloves,

which means
our fingers are slower to get cold.

You either use a scuba
or a rebreather - which
doesn't give out so many bubbles.

But sometimes the best technique
is to go completely simple - simply
use your snorkel and breath hold.

As a testament, this is one
of the most memorable whale images.

It's the sei whale,
with a mouth the size of a dustcart,
passing right by the lens.

Cameraman Doug Anderson managed
to film it holding his breath

and with an amazingly steady camera
from just two metres.

Being close to a blue whale
is something I'll never forget.

But conveying
its sheer size visually
requires a whole range of skills

and poses a considerable challenge.

The idea of this sequence was to
get over how huge the blue whale is.

Although there's
a great shot of David in the boat,
there's no sense of scale.

We got the skeleton through the
internet - there were images of one
that's outside a Californian museum.

We thought it would be
a great location, cos there was
plenty of access, plenty of space.

To prepare for shooting, we had to
put up a drape to hide the car park
behind it

and then we lit it with arc lamps
on cherry pickers from way above,

and then got David to walk around
and through it as we filmed him.

When we arrived on location,
we noticed one problem - the inside
was supported by a black frame

that would appear in every shot.

We had to paint it electronically.

Back in Bristol, for each shot we
created a scene in the 3-D computer,

built models of the organs, lit
them, animated them and composited
them with the shots of David

to give the final sequence.
It's fun AND informative with
the organs appearing next to David.

We brought
something new to the screen.

Finally,
we can show you the essence
of the greatest mammal on the planet.

But even now, we've only touched
the surface of our understanding.

The more we care for and study these
magnificent creatures, the closer
our relationship will become.