Supergiant Animals

'Across our planet, there are spectacular animals

'united by one thing.

'Their size.'

These are nature's heavyweight champions.

True masters of their environment.

These are the supergiants.

'I'm Steve Backshall and I'm travelling the world

'to track down the most remarkable supergiants.

'I want to witness their incredible abilities.'

Yes!

'Understand the challenges they face.'

That tree was snapped like a matchstick.

'And ultimately discover why size matters.'

Wow, that's heavy!

'I believe the best way to do that

'is to encounter them in their world.'

It's coming after us! It's coming right for us!

'Supergiants are unique individuals.

'They dominate their worlds and out-compete their rivals.

'But being massive also brings immense challenges.

'To begin to understand what life is like for a supergiant,

'I'm looking for an animal that's mastered supersize so well,

'it's remained unchanged for tens of millions of years.'

This is the Okavango Delta.

There's about 5,000 square miles of swampy wilderness here,

and it's one of the great spots on the planet for wildlife.

'I've come for an encounter with a predator that's so large,

'nothing can challenge it.

'The Nile crocodile.

'These are Africa's biggest reptiles.

'Up to six metres long and over a tonne in weight.

'They combine raw power and speed with patience and stealth.

'The result is one of the animal kingdom's most formidable

'hunting techniques.

'Nile crocodiles look impressive on land,

'but the secret of their success and their size is found underwater,

'so that's where I'll need to go.

'In over 14 years filming wildlife,

'this is potentially my most dangerous encounter.

'Joining me is Brad Bestelink,

'a film-maker who's lived in the Okavango his whole life.'

So, from your experience, how big do the crocs here get?

The biggest we've dived with has been about four-and-a-half metres.

I'm guessing that you've had some pretty close calls with crocs over the years.

-A big crocodile bit a hole in the side of this boat and sank this boat.

-Seriously?!

Yeah, an animal that big has got no problem going in and punching a hole.

-It's quite a frightening animal.

-Let's hope they don't punch a hole in us!

'Crocodiles sunbathe to raise their body temperature.

'The bigger crocs can store more heat

'and the warmer their muscles, the faster they become.

'When they're ready, they drop into the water to hunt.'

Oh, croc!

'My first chance to see one underwater.

'The initial few seconds are one of the most dangerous parts of the dive.

As soon as we hit the water, we have to drop straight down to the bottom

because the surface is the kill zone, where we're most vulnerable and most exposed.

'Crocodiles usually ambush their victims from below,

'so being above them could trigger an attack.'

Three...two...one.

'The Okavango is the only place on Earth

'where diving with these predators is possible.'

Firstly, because the water's so clear,

there's much less chance of them creeping up on you unawares.

But also, this time of year, the water is quite chilly.

It means that they're much less likely to be aggressive.

But, I have to say, it's still a nerve-wracking experience.

'Their camouflage allows them to disappear

'in this labyrinth of overhanging vegetation.'

And we have a croc. We have a crocodile.

I'm just going to edge forward very, very carefully.

'This crocodile is around three metres

'and, from its proportions, is probably a female.'

And at this size, it wouldn't struggle at all with a human being,

so, to be lying right next to it, to have its tail...

right down at my knees... is an extraordinary experience.

The ability to just sit here not expending any energy

is really important for crocodiles.

They can lie in wait or ambush for their prey

for many days at a time if they have to.

'Large crocodiles can go six months between meals.

'But when they do encounter a potential victim,

'they are equipped to burst into action.'

This broad, flat, paddle-shaped tail...

at the base here...has enormous amounts of muscle

which can drive it from side to side as it powers off.

It can use that for explosive force,

thrusting it out of the water to catch prey at the water's edge.

'And the larger the crocodile, the more power it can generate.

'This female is half the length of the biggest crocs,

'but she can swim incredibly quickly.'

Once they get moving, there's simply no way you're going to keep up,

especially not into the current.

They can drive themselves on with total ease.

And I'm just going backwards!

Our next challenge is to get back up to the boat.

We need to get up and out of the water as quickly as possible.

Oh! That was incredible.

I just can't believe

how much she allowed us to be close to her.

We were right on top of her and just not bothered by us at all.

So chilled out.

What a wonderful animal.

But this is probably as large as female crocodiles get.

The males are the ones that get to be really enormous.

'I really want to find a large male

'and get a sense of its power underwater.

'So we're continuing upriver to look for one.

'And that appears to be a giant.'

Yeah. Hey, it's a big croc, eh?

I've just seen a really good-sized crocodile slide into the water

and we're just trying to get a handle on where it is.

It's even more gloomy and sinister now.

Ah, I see it, I see it!

Our supergiant croc up ahead of us...

he is a true monster.

I'm having to do all I can... to keep my heart rate down.

The last thing I want is for him to sense...any fear from me.

It's a whole different scale.

He's probably...over four metres in length.

It could be four-and-a-half.

This animal is standing up,

menacing, threatening, alert.

I'm really not that comfortable being so close to him.

It's one of the most chilling experiences I've ever had.

'A crocodile of this size could be 50 years old

'and would have no trouble taking an adult wildebeest or me.'

This is the closest I've ever been

to lying alongside a dinosaur.

'The massive male makes for the surface.

'But simply takes a breath and heads straight back down towards us.'

It's coming after us.

It's following us along the bottom!

'Big males battle to dominate their territories.

'He clearly sees us as a challenge.

'We've no choice but to risk a dash for the surface.'

Well, that was without a doubt the most frightening experience

I've ever had with an animal.

There was one point where he came up to the surface

and then he dropped down and headed straight for us.

There was a great cloud of sand went up

and I lost sight of the two guys.

All I could see was lights twirling around

and he's sat on the surface right back there now,

a completely different attitude,

completely different animal to any of the others we've seen.

'By growing enormous, male Nile crocodiles become dominant.

'They retain enough heat to hunt for longer underwater than their rivals.

'And the biggest, meanest males command the best territories.

'Being a supergiant can be a huge benefit.

'But on dry land, it's much more challenging.

'I've travelled to South Africa to discover how some supergiants

'solve the problems that size brings.'

Africa really is a land of giants,

home to the largest of all land animals.

'The hippo, rhino and Cape buffalo are all massive,

'but the supergiant I've come to find

'can outweigh all three of these combined.'

They can run down a human being in full sprint,

they'll destroy pretty much anything in their path.

They are an unstoppable force of nature.

'The African elephant is the biggest land animal on the planet.

'The record-holder was hunted in Angola in 1955.

'It was four metres tall and had footprints the size of dustbin lids.

'At over ten tonnes, it weighed more than a T. rex.

'Today, there aren't so many giant elephants left,

'but I've tracked one down.'

Below me now is Addo Elephant Park. It covers about 700 square miles,

which makes it the third largest reserve in South Africa.

There's about 500 elephants here.

'Over the last century, hunting removed all the big ones.'

So a few years ago they came up with a solution.

They decided to bring in a supergiant male

to try and bolster the gene pool.

'The elephant's called Vallie,

'and we're hoping to pick up the signal from his radio collar.'

Here he is. This is him. This is the animal.

He is enormous!

'Vallie is one of the largest elephants in the world.'

The best way of getting a real sense of quite how big this animal is,

is to approach him on the ground.

It's been a long time since I've seen an animal

that has that size tusks.

They're becoming all too rare nowadays.

When Vallie had his radio collar fitted, all of his measurements were taken.

He stands 3.4 metres at the shoulder,

which means he's taller than our bus that we're driving around in.

'An elephant of this size weighs around six tonnes

'and no other animal around here could challenge him.

'But his life in Addo isn't easy.

'The temperature regularly tops 40 degrees Celsius.

'It's tough here, and even harder if you have a massive body.'

To see an animal of this size in the absolute prime of his life

up close, on foot,

is one of the great privileges of being here in Africa.

'But as wild elephants can be dangerous,

'to get a more intimate idea of scale

'I'll need a friendlier supergiant.'

There are very few bull African elephants in the world

you could stand this close to, but Tembo's very special.

And trust me, when you're in the shadow of a giant,

you feel very, very small.

'He's over three metres tall and very used to being around people.'

You might think that, being this size, life would be easy.

You don't have to worry about any predators.

But for a supergiant, life is just packed with challenges.

'It takes over 200 kilos of food every day

'to fuel a body this size.

'So elephants will stop at nothing to get a meal.'

In the wild, elephants are capable of taking down really large trees

in the hope of getting to the foliage up in the canopy.

How about that?

'An elephant's trunk has around 60,000 muscles.'

This is that tree trunk that Tembo was twirling like a twig.

I actually didn't think it was going to be that heavy!

Wow!

There must be a tonne of trunk here.

And for him it was absolutely effortless.

'This strength gives elephants access to food

'others can't take advantage of.

'But these giants may have to cover hundreds of miles to find food.

'And if you weigh the same as four family cars,

'that takes some clever engineering.'

There's something very, very special about the feet

that I'd really like to show you.

About 60% of the weight is coming through these two front legs,

so he has enormous, pillar-like bones

which allow all of the weight to be driven down into these huge feet.

Elephants effectively walk on their toes,

so this area is where the foot bones are - you can see the toenails,

and all of this area here is fat.

It's a huge, fatty shock-absorber.

'The giant pads cushion the feet.

'With each step, the fat spreads out,

'distributing the load over a greater area.

'When they lift their foot, the fat contracts and the foot gets smaller.

'This helps them avoid getting stuck in the mud.

'While that's ingenious, these titans also face an extra challenge.

'Overheating in the African sun.

'The solution is their colossal ears.'

Even just standing here now, I can feel from the mechanical action

of them flapping backwards and forwards,

it is genuinely cooling, but it's much more than that.

Running close to the surface of the skin is a dense

network of capillaries, filled with warm blood.

As the air moves over the ears, it cools the blood down,

which is then returned to the body, bringing down the overall body temperature.

'Tembo can cycle almost 1,000 litres of blood

'through his ears every hour,

'cooling it by up to nine degrees in the process.

'Without their vast ears, elephants wouldn't be able to survive here.

'Having solved the problems of their size,

'elephants can thrive across much of Africa.

'In their endless search for food, they've become nature's landscapers.

'Another solution to the problems of supersize

'is to escape the drag of gravity by living in the ocean.

'Off the coast of Africa lurks another supergiant

'that does just that.

'The great white shark.

'It's the perfect hunting machine.

'Some truly gargantuan great whites have been pulled from the ocean.

'Over six metres long and two tonnes in weight.

'Some of the largest ever seen have been recorded off the coast of South Africa.'

So this is the reason why there is such an abundance of great white sharks here in False Bay.

On this rocky island, there are over 70,000 Cape fur seals.

'To find out why supergiant sharks are so successful here,

'the best place to start is underwater

'with the animals they hunt.'

Cape fur seals.

They've got a really graceful, elegant, agile way about them

underwater.

They have all these senses on display.

The enormous eyes - they've got fantastic eyesight.

And all those whiskers make them very, very sensitive

to everything that's going on in the water around them.

They're so aware.

It's their manoeuvrability - the fact that they can twist and turn

and move at such speed.

It's an animal that's almost impossible to catch.

'But somehow, great whites manage to eat thousands of seals here

'every year.

'To find out how,

'we're going to need to see a great white at work.'

So this is how you attract the attention of a shark.

It's called chumming.

What we're doing is creating a thin slick of blood and oil.

Sharks can sense just a tablespoon of blood

in an Olympic swimming pool of water,

and can pick up blood from well over a mile away.

I know it's hard to guesstimate but, for you, the biggest that you've ever seen here?

The biggest shark I've ever seen at Seal Island

-is about five-and-a-half metres.

-Five-and-a-half?

That's enormous. I mean, that must be the size of a bus!

You think it's a whale when it approaches the boat.

'Even a giant shark will barely break the surface.

'To get a true sense of scale,

'we need to be eye-to-eye and underwater.

'Shark cages are the safest way to get close.

'On occasion, too close!'

Big shark! Whoa, that's a big shark!

'After hours of waiting, a shark finally appears.

'Time for me to get into the cage.'

We have an enormous great white shark

circling around behind the boat.

This is exactly what we'd hoped for.

She is absolutely colossal.

Probably the biggest great white I've ever seen.

Go down in, go in, go in, go in!

We've been lowered down to about three metres below the surface.

'It's here that the great white's array of senses are on display.'

Wow, did you see how close that was?

It came rocketing past the cage.

'From a distance, the shark is drawn in by smell.

'But when it gets close, it fixes on food using its sight.

'Great whites' eyes are incredibly sensitive.

'Next, electrical sensors in the snout

'analyse the food from close range.

'Once the shark realises this is an easy meal, it attacks.'

Oh, look at that!

Right over the top of us,

thrashing about like crazy.

'The water around me is cold...

'too cold for most types of shark to function,

'but great whites have a special ability.'

One of the reasons they can thrive in waters like these

is that, unlike most fish, they're warm-blooded.

'They use their massive muscles to heat their blood.'

It means they can carry on functioning

at the absolute apex of their abilities.

'These lunges are fine for scavenging,

'but when the sharks are hunting highly manoeuvrable seals,

'they need to step up their game.'

The great white shark's secret is an attack that is one of the most

incredible spectacles in the whole natural world.

'And to witness that, we need to change tactics...

'..by using this.'

It's a decoy, just really a chunk of fibreglass

made in the shape of a Cape fur seal.

And on the top, this is our very own black box recorder.

This measures G-force at the moment of strike.

Essentially, this is going to tell us how it feels

to be hit by a great white shark.

'The decoy also has a built-in camera.'

Glad it's him out there and not me.

'What we're hoping for is known as a breach.

'Conditions are perfect.

'Great whites prefer to hunt in low light

'as it gives them an element of surprise.'

The longer this weather continues,

the better our chances of seeing a breach.

Yes!

That was exactly what we've been hoping to see.

A full, leaping breaching attack.

It was an enormous animal and it completely cleared the water.

The tail must have been two-and-a-half, even three metres

out of the waves.

The force that must be generated to get an animal of that size

clear of the water must be unimaginable.

'But how hard did that shark hit the decoy?'

Right, I want to bring it in quickly now because the last thing we want

is a great white breaching right up onto the boat.

Well, if this was a real seal, it would be in a lot worse

condition than that.

Kind of miraculous, but this does still seem to be functioning.

And let's see what we recorded.

The highest it's recorded is 5G of force

as this decoy was being carried upwards by our shark.

That's the same as a fighter jet in a tight turn.

And if you can imagine that, that kind of force being delivered

by an animal that could be a tonne in weight

with 300 scalpel-sharp teeth, it would be simply unstoppable.

If this was a real seal, right now it would be in tatters.

This is a devastating predatory technique.

The shark's eyes,

pressure and electrical sensors lock on to its target.

With a few flicks of its tail, it accelerates to 20 miles an hour.

The force of the impact drives the entire animal clear of the water.

The decoy is continuing to attract large great whites.

Played in real-time,

we get an insight into why breaches are so lethal.

Seals only have a tenth of a second to react.

And finally we witness a breach by a giant great white.

The decoy is 90 centimetres.

Using it as a scale,

this shark is around five metres long.

This is a true supergiant.

Seen fully out of the water, you can understand why

it's one of the most lethal predators on the planet.

Being a supergiant allows animals to break the rules,

and in Florida one species has used that ability to invade

and conquer a totally new habitat.

The Everglades is probably my favourite part of the whole of North America.

Firstly, because it's very wild and untameable,

but secondly, because it is fantastic for wildlife.

These wetlands are home to America's biggest reptiles.

Alligators, crocodiles and turtles all thrive in this wilderness.

But there's one reptile that simply shouldn't be here,

and it's out-competing all the others.

The Burmese python.

These snakes can reach six metres in length

and weigh the same as a heavyweight boxer.

The pythons are native to South-East Asia

and first came to America as pets.

Some were released or escaped. Now their numbers are growing.

Over 2,000 have been caught in and around the national park.

Nobody knows how many are loose in Florida now,

it could be over 100,000.

Larger and larger snakes are being pulled from the swamp.

The longest so far was 5.7 metres.

I want to get hands-on with a python,

to discover how its size has allowed it to overwhelm an entire ecosystem.

So, we've got here a really good-sized Burmese python.

Oh, wow, that's heavy!

So, this animal was caught about a year ago

and it's used for training for local emergency services,

so the people who might be finding snakes like these

in people's back yards can use this snake

to learn how to handle them.

It's about twice as long as I am tall,

and around about 40 kilos in weight,

that's about the same as a really big dog.

But this is just one long tube of solid muscle.

This snake is so incredibly adaptable,

and as long as there's nothing else that's feeding on it, it is unstoppable.

The pythons are eating their way through the native wildlife.

Professor Frank Mazzotti from the University of Florida

has collected an extraordinary range of items they've swallowed.

We're constantly surprised by the things we find in the stomach.

In fact, we're still finding new prey items.

This looks like it's probably the remains of a bobcat.

The bobcat is so quick, so fast!

Just the idea for that being overcome by a snake is incredible.

This is the hoof from a deer and deer hair,

and it takes quite a large python to eat an adult deer.

This 34-kilo deer was found inside a five-metre python.

Now here we've got something that must have been eaten by a bigger snake,

because those are scales from a decent-sized alligator.

That is correct. I'd say, I don't know, maybe six feet in size.

So, an alligator that was as long as I am tall, and it's been eaten...

-Eaten by a bigger python.

-That's incredible!

I guess what's clear, looking at this, is that nothing is safe here.

That is true, we have a new top predator on the block,

and it's the Burmese python.

Snakes can't chew, but their skulls are supremely flexible,

allowing them to swallow enormous prey, like alligators, whole.

They can engulf objects four times wider than their own head,

that's like me swallowing a car tyre.

After squeezing this alligator to death,

the python will take about an hour to swallow it.

But they don't always succeed.

This snake was found dead with an alligator inside it.

The meal was so big, the snake simply ruptured.

Pythons here are now pushing six metres.

It's an amazing success story for this supergiant,

but it's going to take a monumental human effort

if the Everglades are ever to be rid of this alien invader.

Either that or we learn to live with a new top predator

in the swamps of southern Florida.

Crocodiles, sharks and pythons all show that supergiants

are incredibly successful hunters and dominate their environments.

But another supergiant uses its power to dominate its own species.

On the Pacific coast of the United States lives the biggest animal

you can see on dry land anywhere in the Americas.

For an idea of the scale of the supergiant we're here to find

I've got a selection of skulls.

This one belongs to a black bear and these are found right

here in California, but it's totally dwarfed by this one.

This is a grizzly bear,

and the canine teeth on this one are about as long as my thumb.

This is in the record books as being the largest land predator on Earth.

So, this gargantuan skull must surely come from some

prehistoric dinosaur, a sabre-toothed cat perhaps?

Well, actually this supergiant is anything but extinct.

In fact, they're increasing in number,

there's said to be over 150,000 of them,

and the best place to see them is on the beach just over there.

These are elephant seals.

It's pretty obvious where the name comes from.

I mean, that size, the skin and that extraordinary nose.

They do just look like swimming elephants.

Elephant seals are the biggest seals on the planet.

The largest can be six metres long, and a whopping four tonnes.

I want to see for myself

why elephant seals have become supergiants.

It's important to respect their personal space.

Elephant seals rarely cross paths with people,

but when they do, they can really throw their weight around.

Up here on land, they're impossibly ungainly and out of place.

But for these female elephant seals, there's still one part of their life

where they're totally bound to the land.

They come here to give birth...

-SEAL ROARS

-All right!

..and to find a man.

It's the male elephant seals that are the real supergiants.

They're over three times heavier than the females.

The males have to fight for mates.

The bigger they are, the better their chances of success.

Thanks to scientists from the University of California, Santa Cruz,

I can get hands-on with one to see how it's equipped for battle.

He's been sedated while the team attach a radio transmitter.

It's remarkable, as the animal's breathing

you can hear the air resonating around that huge nose.

You can feel the vibrations coming up from the ground,

it's like someone revving a big motorbike right next to you.

DEEP SHUDDERING BREATHS

Inside that mouth are four canine teeth - look a little bit like that.

Particularly the two on the lower jaw are angled forward like this

and can be used in a stabbing motion.

If that was propelled at me I wouldn't last a second.

Also the skin here is very, very heavy.

I guess it functions almost like a suit of armour to stave off the worst blows.

3.88.

3.88?

This male is four metres long.

He's too heavy to weigh, but seal expert Dan Crocker can size him up.

Just looking at him,

I'd guess this male's about 1,500 kilos.

That's more than three grand pianos!

This enormous bulk, coupled with those tusk-like teeth,

makes seal fights incredibly dangerous.

Confrontations between males always begin with a shouting match.

They're kind of like two guys in a pub car park after closing time,

sizing each other up, just letting rip with that enormous bellow,

and it resonates around that grotesque nose.

SEALS GROWL

The bigger the seal, the deeper its call.

So, by bellowing, males can get the measure of each other.

SEALS BELLOW

These giants can sound off at 120 decibels -

the same as a chain saw.

If one animal's clearly larger,

then the other will probably back down or be chased away.

But if the two are more closely matched, then all hell breaks loose.

GUTTURAL BELLOWS

These two animals keep getting closer and closer,

they're bellowing away and neither's willing to back down.

When the odds are even, a battle begins.

This is the key to why these animals get so big,

where they truly are supergiants.

When you see two males going head-to-head like this,

tearing chunks out of each other,

it is truly like one of the finest gladiatorial contests

you'll see in the whole natural world.

Already there's blood spilt everywhere,

these two massive animals,

tonnes and tonnes of blubber and muscle going head-to-head,

with those canine teeth on the lower jaw

being used like daggers against each other.

And the females are scattering everywhere.

The last thing they want is to get caught amongst this lot...

..and neither do I!

An even larger seal has joined the fight,

forcing one male off the beach

and then the other.

This massive seal is a beachmaster,

he controls an entire section of beach.

The beachmaster seems to have seen off the challengers,

they've both gone into the surf.

The supergiant seal defeated both rivals,

and by doing that has retained the right

to mate with every female in his territory.

He is the beachmaster

and this is the reason these animals get to be so big.

Very few seals ever get to be beachmasters, although plenty try.

The stakes couldn't be higher.

The winners might father 100 pups in a single season.

The losers might die as virgins.

Essentially, success, being able to pass on your genes,

is all down to size, it's all about being a supergiant.

The vast majority of pups born at Ano Nuevo

have a beachmaster for a dad.

It's no wonder they all grow up to become supergiants.

I've seen how supergiants use their size to hunt prey,

survive extremes, expand their territory and win mates.

But there's one ultimate supergiant I want to find

that dwarfs all the others.

We couldn't go on a quest for giant animals

without seeking out the largest ever known to have lived,

the great whales.

These are the largest animals on Earth,

some are even heavier than the biggest of the dinosaurs.

Most great whales are toothless,

feeding by sieving tiny sea creatures from the ocean.

But there's an exception.

One of these leviathans is toothed and predatory.

It's a monster that does battle with giant squid

in the inky blackness of the deep ocean. The sperm whale.

These are hunters of large fish, sharks

and, as this footage shows, the legendary giant squid.

Sperm whales can weigh 45 tonnes,

and use their size to generate the loudest sound in the animal kingdom.

I want to discover what they use this superpower for,

and experience it for myself.

The best place to do that is the island of Dominica, where the whales pass just off the coast.

Here we go.

We have blue skies, mirror-flat seas,

this is just the perfect day for an encounter with a marine monster.

We used to seek out sperm whales for all the wrong reasons.

Over the last two centuries, we pulled around a million of them from the sea,

hunting them for their valuable spermaceti oil

which helped fuel the Industrial Revolution.

Now, they're protected.

Numbers are stable, and they're found in every ocean on Earth.

But that doesn't mean they're easy to find.

To narrow our search, we're going to try

and track the whales using their own superpower.

On the end of this pole is a highly-directional microphone,

we put that into the water and we should be able to hear the sperm whale.

Andrew Armour has worked with whales for over 20 years.

He can pick out the faintest of calls.

FAINT CLICKS

Hear that?

What do you hear?

Sounds like whales.

Their calls can travel over 30 miles,

and there are several distinct types.

I do hear it now, now that you've pointed it out.

"Tik-tik-tik-tik-tik, tik-tik-tik-tik-tik..."

This kind of call is known as "coda",

and sperm whales use it for communication.

So this is almost certainly a group.

There she blows, Philbert!

This is my chance to get up close to these giants.

OK, get in now, get in now!

I've joined a baby and an adult female.

Female sperm whales live in family groups up to 20 strong.

The rest of this pod could well be hunting far below us.

Youngsters can't dive deep,

so this baby-sitter has stayed at the surface.

It could be Mum, an aunt or even Grandma.

She's playing with me,

mirroring my movements.

As she dives, she swings past my cameraman.

That tail has the force to power a giant,

it could easily kill a human.

Yet she takes care not to hit either of us.

It's a remarkable display of agility.

The whales are just as fascinated with me as I am with them.

It's a far cry from the meetings between our species

in the days of whaling.

I am absolutely shaking like a leaf.

She brought her calf right alongside us,

span over onto her side so that she was looking directly in my eyes

from no more than a couple of metres away

and then she pirouetted like a ballerina and swept past me.

But she made so sure that she didn't hit me.

Back on land, I've got a chance to see how sperm whales

generate their extraordinarily powerful calls.

This is a cast of a skeleton of a small female sperm whale.

I guess the thing that catches the attention is the lower jaw,

lined with these curved, backwards-facing teeth.

But weirdly, the predatory weapon of the sperm whale is up here.

This is where the bulk of the head sits, and it is immense.

It could make up as much as a third of the animal's body length.

Almost all of this is filled with spermaceti, that waxy oily liquid.

The sounds that the sperm whale generates are bizarrely created

at the front of the nose, travel back through the spermaceti

until they hit this portion of the skull,

which is shaped like a satellite dish, a parabola.

It focuses and intensifies the sounds as they pass back

through the spermaceti, and then out at this end of the animal.

This beam of sound bounces off objects in the water.

By listening to the echoes, sperm whales build up

a three-dimensional picture of their surroundings.

Using this system,

they can hunt in total darkness over 1,000 metres underwater.

To feel the force of these sounds for myself,

I'm heading back out to sea.

There she blows, Philli!

12.30!

We have a mother and her calf approaching from this side,

travelling very quickly.

And three animals travelling from this side.

It looks like their paths are going to converge

right in front of us.

It's possible this could be exactly what we've been waiting for.

If it's a family group, there's likely to be a lot of communication.

This is my chance to feel the power of sperm whale sonar.

I've dropped right into the middle

of a group of socialising sperm whales...

..and the sound is overwhelming!

The largest males can generate 230 decibels,

far louder than a jet plane taking off.

The whales seem to be scanning me, firing sonar at my body

and visualising its shape by listening to the echoes.

It's highly directional, as the barrel of the whale's head turns

towards me, I can feel the sound resonating through my whole body.

And she's giving me a good eyeballing.

The biggest sperm whales can be 20 metres long

and four times heavier than a fire engine.

Physically, I have little in common with this supergiant,

yet I feel closer to it than any of the others.

We're both creatures with close family bonds,

a real sense of curiosity...

..and a desire to communicate.

That was perfect!

Absolutely mesmerising!

That was exactly what we've come halfway round the world to find.

The sound of the whales is deafening.

But it is rather a mystical experience,

kind of feeling like you're really in the whales' world.

It's thought that sperm whales can use

their most powerful pulses of sound as a weapon,

stunning giant squid.

Yet, rather than being hostile,

this supergiant is the most gentle I've met.

I think the sperm whale is,

to me, the epitome of the supergiant animal,

one that can do things we human beings can only dream of,

and makes us realise quite how fragile we really are.

These remarkable animals have overcome all the problems

that size throws at them, in order to dominate their environments.

But their future survival is far from certain.

In today's world of shrinking habitats and dwindling resources,

it's tougher than ever for giants to find space to live, and food to eat.

Supergiant animals fill us with awe and wonder

and remind us of everything that's special in the natural world.

Everything that's worth saving.

Subtitles by Red Bee Media Ltd