Original subtitles

The deep ocean.

For mammals,

it's one of the most inhospitable places on Earth.

BEEPING

MAN OVER RADIO: Can we move another camera to channel three? OK.

Anything we've got. Yeah.

BEEPING

Survival in this alien world...

...requires extreme adaptations.

We have only recently begun to explore these depths.

BEEPING

So if you're watching on channel one, the Supersampler is... Yeah.

The heck is that?!

Oh, my gosh! Oh, my goodness, what is that?

Yet, some mammals have been coming here

for millions of years.

It's a sperm whale.

Oh, my goodness. Look at that shape.

WOMAN: Holy cow!

Wow! Unbelievable.

BEEPING

Like all mammals, sperm whales breathe air.

Yet, almost a mile underwater,

in the freezing darkness,

they seem completely at home.

They, like many mammals,

have overcome the challenges of living in water

in the most remarkable ways.

Many mammals, encountering water,

prefer to do no more than dip their toes into it.

Northern Sri Lanka, late in the dry season.

A troop of macaques

are looking for what little fruit is left in the forest.

Their search has brought them to a jungle pool.

But there's more for them here

than just a refreshing drink.

Water lilies.

Enough to fill the empty stomachs of the entire troop.

But the flowers are just out of reach.

Got it!

But a single flower merely whets the appetite.

For the real prize...

...they must take the plunge.

For an animal that spends nearly all of its time on land,

macaques are surprisingly competent in water.

They're looking for the lilies' juicy seed pods...

...which are packed full of nutrients.

An excellent solution to the macaques' seasonal food crisis.

LOUD SPLASH

Thanks to their natural curiosity...

...and willingness to explore new opportunities...

...these macaques have discovered that it can pay to jump into water.

Freshwater ponds in a jungle may be few and far between.

In Central Canada, however,

water is everywhere.

Moist soil is easy to dig...

...and just underground

there is a network of tunnels.

The work of a particularly industrious little mammal.

SNIFFING

A star-nosed mole.

Virtually blind,

he relies on his super-sensitive nose.

It's not just for smelling.

It's also...

...for feeling.

And it is 100 times more sensitive

than our own fingertips.

To fuel his active lifestyle,

he must eat up to twice his body weight every day.

And worms, as they burrow,

simply drop into his tunnels of their own accord.

Life underground can be pretty good.

THUNDER RUMBLES

HEAVY RAINFALL

But every spring,

torrential rain saturates the soil.

Before long, the mole's tunnels are flooded.

He can hold his breath for little more than 30 seconds.

He must get out or he'll drown.

Made it!

But having taken a breath...

...he dives straight back in.

Large feet, excellent for digging,

also make very effective paddles.

And his water-resistant coat

keeps him warm...

...so he's well equipped for swimming.

But, nonetheless, there's a problem.

How do you sniff out prey underwater?

AIR BLOWS

First, he blows bubbles into the submerged leaves.

Smells pass into them.

And sniffing them with his nose

enables him to detect something edible...

...so he can locate possible prey even underwater.

Star-nosed moles are one of the few mammals

that are just as at home in the water as they are in soil.

Beyond land,

the oceans that cover two-thirds of our planet

are full of possible food.

For most mammals, it's out of reach.

But that doesn't stop some from trying to get it.

A female coyote,

patrolling the Pacific coast of Mexico.

Living on the edge of a desert

means often relying on the ocean for food.

SEA BIRDS CALL

This female would make a meal of a sea bird

if only she could catch one.

BIRDS SQUAWK

She can't afford to keep failing.

SEA BIRDS CAW

Driven by hunger, she moves on.

The desert stretches 2,000 miles

along Mexico's Baja coast.

Coyotes living here are forced to explore

tangled mangroves and deep creeks.

SEA BIRDS CAW

After a long day under the desert sun,

persistence pays off.

A dead body cast up by the waves.

It's the carcass of a grey whale...

...rotting in the sun.

Enough to feed her for months.

PATTERING

But other hungry beachcombers have found it, too.

GROWLS

SNARLS

They quarrel over the best bits.

But a 40-tonne whale is more than enough food to go round.

The daily tides provide so much food

that the Baja's Pacific coastline

supports up to 14 times the number of coyotes

than occur inland.

HOWLING

But extending scavenging on shore

to hunting in the sea

requires very different skills.

Nonetheless, 50 million years ago,

the ancestors of marine mammals

started to do exactly that.

A bottlenose dolphin and her two young

cruise the shallows of Florida Bay.

The coastal waters here are full of fish.

But much of the bay is less than a metre deep.

For a large mammal with a tail that beats up and down,

just moving around here is a challenge.

But she has a simple solution.

She swims on her side.

But it's still a struggle to keep up with a fish.

Let alone catch one.

And a single fish won't feed a family.

But this intelligent mother has another,

even more ingenious, solution.

Beating her tail,

she churns up the water...

...creating a muddy barrier...

...around a shoal of fish.

In a bid to escape...

...the fish are forced...

...to leap.

She's not the only one that gets a meal.

Her young family can also feed.

But rings of muddy water

aren't the only way in which dolphins hunt in Florida.

This family uses an S-shaped barrier

to spook the fish.

Why Florida's dolphins use different shapes

remains a mystery.

But this ingenuity

enables marine mammals

to move far beyond the shallows.

Californian sea lions.

BARKING

They may spend over 70% of their lives out at sea.

They know the opportunities offered by the open ocean

are endless.

The trick is how to make the most of them.

BARKING

The sea lions have spent a lot of energy to get here,

and the sardines they seek are widely dispersed beneath them.

The hunters need to round them up.

Striped marlin arrive.

Up to four metres long

and with a deadly spear on their nose,

they, too, are hunting.

Watched by the sea lions...

...the marlin go to work.

They herd the sardines into a ball...

...and then drive them up towards the surface.

This is what the sea lions have been waiting for.

Fast and flexible,

the sea lions take advantage of the marlin's efforts...

...and collect an easy meal.

These canny sea lions

have learnt how to let marlin do the hard work.

But sea lions don't stay permanently in water.

The Galapagos Islands.

Specks of land in the vast emptiness of the Pacific Ocean.

Here, pregnant Galapagos sea lions

haul out on a beach to give birth.

BARKING

GRUNTS

PUP WHINES

Unable to swim when it's newly born,

a pup relies completely on its mother

for her care and her milk.

PUP WHINES

Within two weeks, thanks to the richness of this milk,

it will be strong enough to venture into the water.

But a newborn pup

is something of a shock to its older brother.

For the last two years,

he's had his mother all to himself.

The new pup is a sure sign

that he must now find his own feet.

BLEATS

A sheltered inlet is a safe place for pups and other juveniles

to build up their confidence.

Now, under the watchful eye of a dominant bull...

...the young sea lions acquire the skills they'll need

for a life at sea.

BARKS

But this is the time of year

when sea lions also mate.

GRUNTING

While the bull's attention is elsewhere...

...the pup ventures beyond the safety of the rock pool.

It's a mistake.

The waters surrounding the Galapagos

are patrolled by sharks.

The pup strays further from the pool...

...while the bull is preoccupied.

The pup can outmanoeuvre the shark...

...but not for long.

Alerted by the commotion...

...the bull takes action.

Weighing a quarter of a tonne,

the bull is more than a match for the shark.

Biting at its tail,

he chases it away.

For the pup, it's an important lesson learned.

BLEATS

Many others...

...are less fortunate.

Nearly half of these young sea lions

will not survive beyond their second birthday.

This pup is safely back on land,

and not too old for a reassuring cuddle.

GRUNTS SOFTLY

One small group of mammals, however,

have completely cut their ties with the land.

WHALE SONG

Humpback whale calves can swim from the moment they're born.

The warm coastal shallows off Western Australia

provide excellent nurseries.

In their first few days,

mothers and babies form a strong bond.

Tucked gently under her fin,

this mother gives her daughter

an early lesson in holding its breath.

But they won't stay here for long.

The reef may be an excellent place to give birth...

...but there's almost nothing to eat here...

...so mothers and young

must now make the long journey to richer waters around Antarctica.

But once they've left the safety of the shallow reef

they are vulnerable.

A pod of orca...

...six strong, patrols the migration route.

They are a formidable force.

But the humpback mother puts her baby high on her back

to protect it...

...and then goes on the attack herself.

Slashing her powerful tail

and long five-metre fins,

she could easily kill an orca.

But the orca have a plan.

Some of the pod distract the mother...

...while others ram the calf.

Once it's separated...

...they drown it.

Since 1986,

when commercial whaling was largely banned,

humpback numbers have risen here from a few hundred

to more than 35,000.

With so many calves on the move,

some orca have specialised in hunting them.

A small pod - just three.

The humpback calf they're pursuing

has more than just its mother at its side.

It also has...

...a 40-tonne male.

This is a much bigger challenge.

But rather than give up...

...the orca bide their time.

The male humpback,

believing, perhaps, that the orca have gone...

...now dives.

The killers seize their opportunity.

They kidnap the calf.

They appear to mimic the mother's behaviour,

putting the young calf on their backs

and carrying him along in the slipstream.

Young and naive,

the calf goes willingly with them.

Now, far from his mother...

...the orca attack him.

During the months of migration,

the pod may kill as many as five calves a day.

They catch so many

that sometimes they eat no more than the tongue...

...and leave the rest for the sharks.

This is what can happen

when prey is so abundant

and hunters have such skill.

False killer whales are less than half the size of orcas...

...but they are equally clever.

They roam the ocean in groups up to 50 strong.

Right now, they're on the hunt for other mammals.

HIGH-PITCHED SQUEAKING

Ocean-going bottlenose dolphins.

But the false killers aren't looking for prey.

These two groups are old acquaintances.

In the waters around New Zealand,

they are almost always found together.

Lifelong bonds within species are common...

...but they are rarely seen between different species.

Such friendships

between bottlenose dolphins and false killers...

...have been documented going back 20 years...

...so it's entirely possible that individuals of both species

recognise each other.

They team up not only to play...

...but in order to hunt.

So, when one goes...

...they all go.

A huge school of kahawai fish.

The false killers swim under the shoal...

...and drive it to the surface.

Here, the dolphins attack.

But despite helping,

the whales don't appear to feed.

For them, the kahawai are just the bait.

The false killers know the commotion will attract bigger fish.

Kingfish arrive.

They're up to ten times heavier than the kahawai,

and one metre long.

Too big for the dolphins.

So, now it's the turn of the false killer whales to feed.

They form small groups

and break up the school...

...and then go after the fish that get separated.

Not all the whales make a catch.

But they won't go hungry.

Extraordinarily, the successful hunters share their food.

By helping one another...

...they ensure that no-one goes without.

Teamwork, intelligence and cooperation

has enabled marine mammals to flourish in the high seas.

But one part of the ocean is still beyond the reach of most.

The deep.

Only a very few are capable of venturing here.

A pod of sperm whales resting near the surface.

They spend just 7% of their lives asleep,

less than almost any other mammal.

But they're also waiting here

for another very special reason.

The birth of a baby.

CLICKING

Helped into the world by supportive relatives,

the newborn is already more than three metres long.

It will grow up surrounded and protected by close family.

It thirsts for its mother's milk,

but the food the mother needs in order to produce it

is 1,000 metres below,

far beyond the reach of a young calf.

So, whilst the family looks after the newborn...

...the mother sets off in search of a meal.

Adult sperm whales may remain below,

holding their breath, for an hour.

As they descend, their bodies change in an astonishing way.

The increasing pressure squeezes their lungs

until they collapse completely.

To save oxygen,

their digestion, kidney and liver shut down.

A special camera records a rare and privileged view

of a hunting sperm whale,

sending out a stream of clicks

to detect prey in the pitch blackness.

CLICKING

At this depth, they start to hunt for giant squid.

As the whale closes in,

their clicks speed up.

RAPID CLICKING

A puff of ink is released by the fleeing squid,

but the sperm whale isn't fooled...

...and the squid is eaten in a last cloud of ink.

As this mother returns,

her calf, like all mammal babies,

has only one thing on its mind.

Milk.

It's growing faster now

than during its 16 months in the womb.

And it will consume up to 100 litres,

300,000 calories,

every day for the next two years.

To meet this demand,

its mother will have to dive up to 15 times every day.

It is her ability to reach such extreme depths

and turn what she eats into rich milk

that will be the key to her baby's success.

Today,

protected almost worldwide,

the outlook for this mother and baby,

and all sperm whales,

is bright.

Even so, sperm whales still face many threats.

Every year, enough fishing line is lost in our oceans

to stretch to the moon and back...

...together with 20 million traps,

and carrying 14 billion hooks.

The whales become entangled in these so-called "ghost nets".

The lines cut into their bodies...

...and the floats can prevent them from diving.

Theirs is a slow and agonising death.

We are now aware of the threats we create.

Surely, we should now do everything we can to prevent them.

The greatest challenge for the Mammals team

was not only filming false killer whales in New Zealand,

but trying for the first time

to place a data-recording camera onto one.

With only 150 individuals somewhere within 4,500 square miles,

just finding them will be hard enough.

Luckily, they have the help of Jochen Zaeschmar,

who has been studying this group of whales

for the last 20 years.

He has a directional hydrophone,

with which he can hear the false killer whales' whistles...

...but only from less than ten miles away.

Nothing.

I was kind of hoping... kind of hoping to hear something.

Cameraman Andre Rerekura scans the horizon,

but picking out a fin in the open ocean is no small feat.

The scale of the task ahead

is dawning on assistant producer Kyle Swann.

Searching. Searching, searching.

That's kind of the strategy,

but so far, no luck.

With only a brief few weeks

during which it's possible to film them,

it's a disappointing start.

There's absolutely nothing.

Over the coming days, the team search without pause.

Nothing.

Absolutely nothing.

Nothing again.

Still, keep trying.

They have spent 20 days with no whales...

...but Andre spots something promising in the distance.

There's a few birds, but nothing crazy.

Yeah, well, that's where I heard some faint whistles there.

Worth a look while we're here.

Ah, I've got something!

Whoa! We have a haul. Oh, my God, yeah.

It's promising. It looks...

I've seen a stumpy nose!

I think we've got falsies!

Whoa! Falsies!

No way! Woohoo!

We have 'em!

HE LAUGHS

But with the sun setting

and the whales capable of covering 100 miles a day,

the team hop on their liveaboard

to follow the whales overnight.

The crew takes turns on watch,

using their eyes and ears.

ANDRE: Yeah, we've pretty much done circles all night.

We're in the same spot we found them yesterday afternoon,

so they don't go far.

Like Jochen says, they just sleep.

So they've probably had more sleep than us!

Falsies off the bow! Big old falsies off the bow.

Woohoo-hoo! There's one just here.

Oh, my God, this is just amazing.

They're in a good mood.

A new dawn presents a new challenge.

Back on the filming boat,

the team follow the false killers as they hunt.

No-one has ever recorded them creating a bait ball before.

But the whales can swim at 20mph,

so Andre has brought a little extra propulsion.

ANDRE: The scooter's a game-changer.

You can free-dive down with, you know, a full lung of air,

all your energy,

and hold your breath for a minute and a half to two minutes with ease.

The scooter lets him keep up with false killers

and helps propel him swiftly into the heart of the action.

Once the feeding frenzy is over,

the whales turn their attention to Andre.

ANDRE: This incredible interaction.

It just... just made me realise how amazing

and intelligent these animals are.

CLICKING

It was really unique and really special.

That was... Woo!

I can't even explain that!

Having captured this extraordinary behaviour,

the team switch to the most difficult goal of the trip...

...to place a suction tag on a whale.

For 20 years, Jochen has studied this group

of false killer whales,

but this would be a first.

The tag contains a camera and a data collector.

Combined, they will give Jochen new insights

into how these animals spend their time underwater.

Getting close enough to attach a tag

will take every ounce of Jochen's expertise and understanding.

Here they are.

While they're just chilled, I'll just go in there real slow.

Hope to... Hope to get lucky.

OK, OK, OK, OK.

Beautiful, beautiful, beautiful, beautiful.

OK. No, no, no.

No. No, no, on the next one, on the next one.

They're going down a bit. We'll get them, we'll get them.

Trying to find that perfect moment!

Heart's going through the roof!

JOCHEN: This is a bunch of different males.

Let's see, though, see how they like us.

They're all coming together now.

There's just so, so many factors.

The way the angle of the camera is,

where it comes up next to you.

I'm hopeful. It's hard work.

They're not making it easy.

As the wind drops,

the team have a brief but perfect opportunity.

JOCHEN: So I'm just going to...

...ease my way over towards them.

Wait.

OK, this is it.

Yeah! We did it! We did it!

We did it!

THEY LAUGH

Well done!

Woooo!

We did it. We did it! I'm so happy!

THEY CHEER

It's not just the achievement of getting the tag on,

it's the promise of what it will reveal.

And that turns out to be astounding.

Intimate food sharing

and new hunting strategies

have been recorded for the very first time,

giving us a new perspective on mammals' lives underwater.

Next time - we venture into the cold.

A vast and unforgiving world...

BARKING AND GROWLING

...where mammals, through sheer tenacity

and adapation...

...have found a way to make it home.