DAVID ATTENBOROUGH: 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.