Whale Sharks Natural World

A giant roams the world's oceans.

At more than 12 metres long, the whale shark is the largest fish in the sea.

Yet for all its size, it remains a total mystery to science.

For most of the year, they travel the oceans undetected.

Then, off tropical coasts and coral reefs, the whale sharks suddenly appear.

Where they come from, nobody knows.

But just as mysteriously as they arrive, the whale sharks soon disappear.

Back her off... There it is! Right there!

Shark expert Dr Mark Meekan is on a quest to find out where they go.

He believes they're travelling huge distances

and could even be crossing oceans.

Over the next year, Mark will attempt to track the whale shark's movements.

If all goes to plan, he will unravel one of the ocean's great mysteries.

Ningaloo Reef, Western Australia,

where the Indian Ocean meets the harsh desert coast.

Just 100 metres off shore lies one of the world's richest coral reefs,

where an incredible event is about to take place.

It's early April, and seven days after the full moon,

a neap tide calms the great ocean swell.

Underwater, the reef is stirring.

Finally the conditions are right for the coral to spawn.

Over the next 24 hours, several tonnes of sperm and eggs will be released into the water.

Overnight, the reef explodes into life.

And soon one of the most mysterious animals in the ocean appears.

For a few brief months each year, hundreds of whale sharks

come to cruise the Ningaloo coastline.

They're the ocean's great wanderers.

But outside these waters, almost nothing is known about their lives.

The first time I swam with a whale shark was about ten years ago now,

out the front of Ningaloo reef.

Beautiful calm day, jumped in the water,

and out of the deep blue came this great big shape.

You've got an animal that hasn't changed, basically,

since the age of the dinosaurs.

You're swimming with a dinosaur.

At the same time, it's just an absolutely beautiful animal.

Now Mark Meekan is finding worrying evidence

that whale sharks are on the decline.

Over the last ten years, the average size of sharks we've been seeing has been getting smaller.

It's alarming because it's a classic symptom of over-fishing.

If my kids want to swim with whale sharks,

there are really two questions that we actually have to answer.

The first of those is, where do they go after Ningaloo?

The second one is, who are they interacting with?

Those are the things we've got to find out.

The next morning, Mark heads out on the first day of his tagging operation.

They have just one week to deploy six satellite tags.

They may be searching for the biggest fish in the ocean,

but it's still a challenge to find them.

Norwest Air, this is the Orissa Blue. You receive me?

'Go ahead Orissa Blue, this is Norwest Air.'

From the air you can see the sharks much, much better than you can see them on the water.

These things are brilliantly camouflaged

but in the air they're silhouetted. The pilot can look down,

spot the shark and he can lead us straight to it.

Now the key thing is the whale sharks have to show up and want to play.

Tim, we'll hang around Black Rock here.

-If you get a shark we'll have a good run to it.

-Roger that.

Stretching 260 kilometres across the West Coast of Australia,

Ningaloo is one of the largest fringing reef systems in the world.

And at this time of year it explodes into life.

Every creature in the ocean is moving in to feed and breed,

from the smallest to the largest.

They've all come to exploit the reef's nutrient-rich waters.

'Orissa Blue, Orissa Blue, this is Norwest Air - do you copy?'

Receiving, Tim. What have you got for us?

'Got a large shark about half a mile...'

Guys, got a shark.

OK. Going north at about what speed, mate?

The whale shark has been spotted at the surface

but it's an unpredictable animal and could disappear at any moment.

-How big?

-It's a seven-metre shark but he's diving.

-We need to get down there quick.

-Toe tag?

-Let's get it on.

-Coming up on the wave now.

-Got it?

-Good to go.

-Gun loaded?

-The gun's loaded. Safety's on.

OK. I see him. Go, go, go, go.

Every shark is photographed for their database.

The tag is designed to drop off after a year.

For the shark it will be painless,

but for Mark it's a dangerous moment.

An animal this large must be approached with extreme caution.

A direct hit from its tail could cause serious injury.

I'll pass you the gun there, Cary.

-Careful, it's still loaded. Didn't go off.

-Got it.

Got in the water, got up to it, put the tag on the animal

and the gun didn't go off.

Ah, you know, occasionally these things happen.

We're just going to have to work out why it didn't go off.

Beneath them, the conditions are perfect for whale sharks.

As the current runs over the reef, it brings with it

a cloud of minute sea life that turns the water cloudy.

And soon the ocean's filter feeders are drawn to the feast.

Whale sharks are the largest of all sharks.

Fully grown, they're twice the size of a great white.

And with a mouth up to two metres wide,

they could easily engulf a human.

But these sharks are gentle giants,

and unlike their fearsome relatives, they filter their food.

Gulping thousands of litres of water every hour,

they use their huge gills to sieve out small particles of life.

OK, we've got a whale shark just off the bow.

With the gun fixed, Mark is back in action.

Go, go, go!

As Mark approaches,

the whale shark turns its back in a defensive posture.

Here its skin grows up to 14 cm thick -

thicker and tougher than any animal in the world.

Breath-holding to 15 metres,

Mark's first successful tag shows just how dangerous it can be.

This animal's swimming towards you at about two knots.

It's like a bus coming past and you're trying to whack something on the side of a bus as it goes past.

It's not a simple matter.

The animal's big. You can't stop it, you get one shot at it.

As the afternoon progresses,

more sharks are tagged and the project gets off to a good start.

You know what I was doing today?

I tagged three whale sharks today.

Three!

Three great big ones.

'You know, it's my son,'

he's five years old and he's got a...

Well, he loves whale sharks

and I was hoping maybe we could get some names

for some of the whale sharks we tagged today.

You know, he came up with some names.

Hamish and Jack, two of his school friends.

As the moon rises over Ningaloo, it's time to input the day's data.

Over the last ten years,

the team has built up an impressive database of whale shark sightings.

Each animal has a unique pattern of spots that allows Mark

to identify and cross-reference every individual.

OK, lets see if we've got any matches from today.

The first shark to be analysed is a six-metre male he calls Hamish.

The next two are smaller adolescent males named Jack and Sammy.

Have they ever been seen in these waters before?

The photo ID results show they're new to the database.

But just like the other sharks at Ningaloo,

they share one thing in common.

The population here at Ningaloo, they're all young males. They're all juveniles, really.

Although they're quite large, five to six metres in size,

they're still babies really. They haven't become mature.

By the end of the week, a total of six whale sharks are tagged.

Now every time Hamish and the others surface,

a satellite deep in space will record their every move.

But unlike a true whale, these sharks don't need to come up for air

and could spend several days deep underwater.

With the tags on, Mark can now focus on another whale shark mystery.

Beyond a few brief encounters at the surface,

almost nothing is known about their day-to-day lives.

We're going to try and attach this camera - it's more than a camera.

It's a mini laboratory, it's a dive computer.

This has never been done successfully before, but if we get it right

it's going to tell us about what these animals are feeding on,

how they get down there and what they're actually doing on the bottom.

We can't go down there. This can,

and when it pops back up to the surface we get that information back.

The camera is attached by a time-sensitive fuse

and will release at 4am tomorrow morning.

Riding on top of its back the camera will capture

a shark's eye view of Ningaloo Reef.

Offering for the first time a unique window into the whale shark's world.

What secrets will it uncover?

-22...

-22 degrees, 40.211 minutes.

-40.211.

-The next morning, the team head out early.

-113 degrees.

We've got the lat longs of the camera.

It's come off the animal, floating in the ocean and we've got to go and get it.

The coordinates will get them close,

but from here on they must rely on a VHF receiver

to pick up the camera's signal.

With 40,000 of equipment floating in the open ocean,

there's a lot riding on its safe return.

-One o'clock, straight ahead.

-Yeah, there it is, there it is. Got it.

Keep coming, Terry.

-One o'clock, Terry.

-About four boat lengths.

-Keep the same position.

-Coming down the side.

Well done!

Hup! He's got it.

Woo-hoo!

Hey, you caught a fish!

An expensive fish.

A very expensive fish, look at that!

Great, fantastic, we got it back.

We got it back!

Well, hopefully it's full of data, that's the next question.

Did the camera work, did the instruments work, that's the thing.

If they did it's fantastic, it's a huge amount of data in there,

that no-one's ever managed to get from whale sharks before.

While the sharkcam data is being analysed,

information starts to come in from the other tagged sharks.

Will they finally discover where Ningaloo's whale sharks are going?

In the weeks that follow,

Mark tracks their progress up and down the coastline

as they continue to feed on Ningaloo's rich currents.

By mid-May one of the sharks, the six-metre male called Hamish,

breaks away from the group.

Moving offshore, he leaves the security of the Ningaloo Marine Park

travelling 800 kilometres into the Indian Ocean.

It's an exciting development.

It confirms Mark's suspicions that Ningaloo's whale sharks

are not only leaving Australia, but travelling huge distances.

But it's here, entering the busy shipping lanes of Asia,

that Hamish is most vulnerable.

Every year, hundreds of whale sharks

are killed by boat strikes, fishing, and even pollution.

It's having a devastating effect on the Ningaloo population.

Ten years ago whale sharks averaged seven metres in size.

Today the whale sharks we see out there are three to four metres in size.

That's a drop of two metres, it's big.

There's also been a worrying decline in abundance.

Now those are classic signs of a population in trouble.

It makes it all the more critical that we find out where these sharks are going to.

You have to know where they're going and who you have to talk to

if you're going to do anything about the problem.

Protecting an animal that moves through international waters isn't easy.

But thankfully, Hamish's journey doesn't end there.

Whilst the other sharks stay around Ningaloo,

Hamish continues west at a rate of 30 kilometres a day.

But before more satellite data comes in,

the sharkcam starts yielding some interesting results.

We put the sharkcam on the sharks to really, for the first time,

get a view of what the shark is actually doing

down on the bottom at Ningaloo,

and it's an amazing bit of footage we've recovered.

On the surface we can see the shark gulping and feeding at things.

But there are plenty of strange behaviours I can't explain.

There's some interesting behaviour where the shark is literally

standing on its tail and sinking down from the surface.

What it's doing then I have no idea.

And more surprises are being revealed by the 3-D dive profile.

These animals are a lot like marine mammals.

They go down and come back up again. Why?

Well, one, it's a search for food.

The water is in layers. Smells travel really well through those layers

and if you're a shark you go down, you go up, you pass through all those layers

and you get a good sample of what's around to feed on.

The other thing is that, even though these are big animals,

the water down at the bottom is colder than it is at the top

so it may well be that when the shark spends a lot of time at the bottom

it actually has to come back up to the surface to reheat.

But we need a lot more footage like this

to really understand the reasons behind that diving behaviour.

It's two months since the tags were deployed

and Hamish has travelled 1,000 kilometres.

Where he is heading, nobody knows.

Mark has a hunch that Hamish could be following

seasonal food pulses around the Indian Ocean.

We know that these animals turn up at Ningaloo

for these mass feeding events and there are other places

around the world's oceans where this happens as well.

In the Indian Ocean they also turn up periodically to feed off

Christmas Island, India, Kenya, Mozambique and the Seychelles.

The real question is, are they the same animals that are participating in all these events?

Are they travelling between them?

The DNA evidence shows they're all closely related

and could be part of one large inter-breeding population.

So could Hamish be travelling from Australia to Africa?

As he continues west, now almost 1,000 kilometres from Ningaloo,

some disappointing news comes in.

The tags are off the animals, they're floating.

How they came off, I don't know. It's just one of those things.

We have to expect a high failure rate for tags, so we just have to

get more out there, get more on the sharks I think is the only way forward.

Following his hunch, Mark flies 5,000km across the Indian Ocean

to the tropical islands of the Seychelles

for a working holiday with his family and the next leg of the study.

To meet them is long-time collaborator, David Rowatt,

who runs the largest whale shark monitoring programme in the world.

Hiya. How are you two?

So are you getting good sharks, David?

Yeah, sharks arrived about a day or two ago.

We're getting reasonable numbers at the moment.

It's taken 18 hours to get here from Australia

and now Mark and David have just one week to find out

if the whale sharks are making a similar journey.

Basically the boats are going out every day, so yeah, ready to roll.

Perched on the edge of the African continent, the granite islands

of the Seychelles rise out of the Indian Ocean.

It's the start of the whale shark season

and for the next three months,

seasonal upwellings of nutrient-rich waters

will attract whale sharks to these shores.

Real time, real time, I have sighted a shark...

-It's just south under me.

-We've got a visual.

During this period, every encounter is photographed, measured and recorded.

Go when you're ready. That's it... Go, go.

And what's so special about this research

is that almost all the data is collected by tourists.

We thank you for coming along,

because it's only with your assistance and support

that we can run this programme.

It's all part of David Rowatt's plan to make the whale sharks more valuable to the island.

And by offering hundreds of tourists the chance to swim with them,

it means that David can run his research on an epic scale.

It's this data that could tell Mark if Ningaloo's sharks are visiting the Seychelles.

That long line there - it's not the same shark.

Both David and I have very large

photo-identification libraries of whale sharks,

for me in Ningaloo and David in the Seychelles and what we've been doing

is using a computer programme to try and match those photographs.

-So we've done the fingerprint, we've done our three points in.

-Yeah.

If Hamish and other Ningaloo sharks really are crossing the Indian Ocean

they would expect to find some matches.

But with over 1,000 images to compare,

it will be another month before they will know the result.

In the meantime, Mark and David have more tags to deploy.

Real time, real time, I've sighted a shark.

It's just south. We're gonna go down and have a look.

Real time, if you come right 45 degrees, at 500 metres from you,

45 degrees, 500 metres.

Go, Dave, go!

Every year more than 200 sharks visit these islands,

but when the food runs out, almost all of them disappear.

By tagging more whale sharks, Mark and David hope to find out where they're going.

Could they be heading back to Australia

and the rich waters of Ningaloo?

After a successful start, it's time for Mark to head out

for some fun with his six-year-old son, Sammy.

We've promised him he can go swimming with a whale shark.

I think I'm more delighted than he is, actually.

It's been such a fondly held dream of mine for so long,

and finally we did it, you know?

-OK, it's just here, Mark, close to the boat.

-We'll get there.

Here we go, are you ready, mate?

It really was a contrast between the two of them.

I mean, there's Sammy, he's just over a metre tall,

and that shark, five or six times his size,

and he's not afraid of it at all.

Perfectly happy to paddle along with the shark.

Missing most of its dorsal fin, this shark is typical of the population

in the Seychelles, where some 30% carry the scars of boat strikes.

It's a sobering reminder of just how vulnerable these sharks are.

It was important for me to have Sammy swim with the whale shark

and share that joy I get out of it with my kids,

and important to do it now too, because who knows, mate,

when he's my age they may not be around.

As the week progresses, the team collect data on ten more whale sharks.

And as Mark's trip draws to a close,

they attach a second satellite tag to a four-metre male named Joe.

Soon, data comes in showing him moving north along the main island.

But as Mark returns home, the airwaves go silent.

And as weeks turn into months, it becomes all too apparent

that the satellite has lost contact with the sharks.

You know, pretty disappointed that another tag design has failed.

But, look, there are some real positives that came out of the Seychelles.

One of those was the photo ID study.

We found no matches between the Seychelles and Ningaloo.

That's really significant because it tells us the animals

probably aren't travelling between Ningaloo and the Seychelles or vice versa.

What I think it means is that we have to look closer to home

for some of the answers about where these animals are going.

If Ningaloo's whale sharks aren't crossing the Indian Ocean,

then where are they heading?

Mark re-examines the data from Hamish,

the adolescent male that lost his tag mid-ocean.

16,000 kilometres from Ningaloo

lies the tiny Australian outpost of Christmas Island,

where there are reports of whale sharks gathering.

It's a tiny little green speck out in the middle of the Indian Ocean

but to whale sharks they see it from a different perspective.

It's a giant mountain rising out of the sea floor and the whale sharks turn up there predictably every year.

Arriving on the tail end of a storm,

Mark has just two weeks to find some answers.

But his first lead doesn't point to the ocean.

Instead, it takes him inland to the lush tropical forests that cover Christmas Island.

Here, beneath a pristine canopy,

one of the greatest events of the natural world is under way.

Hey, look, crabs, crabs on the road.

Yeah, there's a lot on the side of the road.

OK, look out, don't run them over.

Stop, stop, we're going to drive over those ones. Yeah, I'll get out.

Look at that.

It's a red land crab. It's land crab breeding season

and these guys are all moving from the forest down to the beach.

Each one of these crabs is spawning about 100,000 eggs

and you've got to figure that with about 15 million females on the island

we're talking about a billion eggs being released into the ocean.

We don't know if the whale sharks are actually eating them or not

but you'd have to figure that it would make sense.

The crabs only spawn on one night of the year.

Is it just coincidence that the whale sharks arrive at the same time?

It's now a month since they left their forest homes,

and their arduous migration is almost over.

Now heavily laden with eggs,

the females navigate the final stretch to the ocean.

In a few hours' time,

100 million new lives will be launched into the water.

Look at that! That's amazing!

Crabs on top of crabs on top of crabs.

That's incredible, look.

At 4am, on the turn of a high tide, the action begins.

Like their marine ancestors,

the land crabs are still tied to the ocean

and their eggs can only hatch when they reach the water.

That is solid crabs, look at it.

They're flapping, look at that!

There's the jig as they release the eggs.

As the eggs hit the water they hatch immediately

and turn into these tiny little crab larvae.

They'll swim around for about 27 days out on the water

and then come back in a stage called the megalope -

it looks just like a baby, juvenile crab -

and climb up the cliffs and head back into the forest.

Look at the water - it's brown with eggs.

you've got to figure that this is a great reason

for the whale sharks to come to Christmas Island.

No-one has ever witnessed sharks feeding on red crab larvae.

It's just a theory, but if Mark can prove it, it will be a first.

But the next day gets off to a slow start.

We're very keen to get out and see if we can find some whale sharks.

One problem is though that our plane, our aerial support, is out there on a supply ship.

The weather's been so bad they've been unable to bring the boat against the wharf here.

Without that plane it just means we're going to have to get out there

and maybe do an exploratory dive and see what we can see.

With no indication of when the boat might come in,

Mark's best chance of finding a whale shark

is to start surveying the island's 80 kilometres of coastline.

Surrounded by a narrow ledge of tropical reef, the sea bed

quickly drops away to the abyssal depths of the Java Trench.

Four kilometres below the surface,

it's one of the deepest points in the Indian Ocean.

And it's along these walls that the whale sharks are reported to cruise.

As you went over the edge of the drop-off,

you lean forward and it was like you were flying a plane into the depths.

An absolutely fantastic feeling.

It truly is the edge of the unknown.

You feel like you're clinging to the last vestiges of the land,

and somewhere out there are these giant creatures cruising up and down.

But until they can get up in the air,

the sharks remain as elusive as ever.

Then, on the fifth day, the container ship finally comes in,

and with just one week to go Mark's study can at last take off.

The team's first task is to locate the whale sharks

and establish where they are congregating.

What a great morning for flying.

-Yeah, it's awesome, isn't it?

-Beautiful.

You get a great view from up here, don't you?

It's the first time a whale shark survey has ever been conducted

on Christmas Island, and Mark has no idea what he's going to find.

OK, that's deep. Let's just swing around.

Yeah, that's a shark. OK, that's a big tadpole.

Look at that, they look just like big tadpoles from the air.

A great big, fat head

and a skinny tail at the back.

-It's great, isn't it?

-Oh, we lost them.

Well, we saw two whale sharks, they're both on the north coast.

What it means for the population we're not really sure.

We need to do a few more flights and spend a more time out there to find out if there are more of them.

Maybe it's the same two whale sharks out there every day. Who knows.

It's fewer sharks than they were expecting, but it's enough to get started.

Mark has just six days left to find out

if Hamish and the other whale sharks from Ningaloo

are visiting Christmas Island.

To do this they plan to find, photograph and tag as many of them as possible.

The spotter plane is now finding many more sharks.

It's right here, by the boat.

But, frustratingly, as soon as they get close, the animals are diving.

And as the days go by,

the difficulties of studying such an elusive fish are all too evident.

-That's getting ridiculous, don't you think?

-Yes.

Same old story, I'm afraid - get on the shark,

right up close to it just off the bow, within distance to swim to it,

the thing dives straight away. I didn't see it.

It was on the surface but it jumped in. It hit the water and was gone.

With one day left, it looks like they will go home empty-handed.

-I'm over it.

-It's hard to tag them when you can't see them.

-I'm over it.

Bye, Mark!

10 o'clock...

Two only, back her off, back her off.

There it is, right there!

Then on the very last day, just hours before their flight,

a final opportunity presents itself.

We have a visual, stay on it, small shark.

They're coming round on the back, OK?

In... go, Cary, go! Go!

Get it, go!

We're looking at it.

We're not waiting here, we're going.

It's a friendly shark!

Good God, I didn't know they existed.

HE SHOUTS AND CHEERS

Christmas Island was nothing if not dramatic.

We spent two weeks there fruitlessly searching for whale sharks

and in the final day we finally got some.

In fact, we got a lot.

We got seven tags out.

It was an absolutely fantastic end to the trip.

And remarkably, we even got a whale shark that managed to do a poo for us.

It's such a rare event.

I've only ever seen it twice

with the hundreds of whale sharks I've swum with.

It's so significant because the DNA in that sample is worth gold.

Here it is - whale shark poo.

Tip it out and there it is.

That little, reddy brown soupy mixture there,

if we can extract the DNA out of this, it's gonna tell us something

about why the whale sharks are coming to Christmas Island.

And when the result come in, it proves Mark's theory.

The sample is packed with red crab DNA.

The results of the poo analysis are pretty exciting.

They tell us that the migration of these sharks from Ningaloo to the north is not some random thing.

These sharks are actually directing their movements.

They're going to Christmas Island for a reason.

There's a whole pile of food up there and these sharks are feeding on it.

So the next question is, where do they go after Christmas Island?

Do they come back to Ningaloo or do they go somewhere else?

In the weeks that follow, all seven sharks remain around the island.

But after a month, only one tag is still transmitting.

It's attached to a five-metre male named Fin,

and to Mark's delight, he's now on the move.

First, he travels north,

before heading south-east on a direct course back to Australia.

It's an exciting development.

With Ningaloo's coral spawn imminent,

could Fin be returning on an annual migration?

But then, to everyone's surprise, he changes direction.

In two months he travels 2,000 kilometres,

before disappearing off the radar.

It looks like there's a problem with Fin's tag.

But two weeks later, he reappears in the Banda Sea.

The dive data reveals he travelled 800 kilometres,

rarely coming close to the surface.

Mark wonders whether he was feeding on an unknown food source deep underwater.

Or perhaps he was avoiding the strong surface currents

that run between these islands.

Then Fin turns around and heads back to West Timor.

It's here, four months and 4,000 kilometres later,

that the tag finally falls off.

It washed up on a beach and it was found by a guy searching for turtle eggs.

The tag was still transmitting so I could actually see the guy

and I could see his house where he was storing it.

So at that point I got one of our PhD students

to go and recover the tag, which he did.

And here it is. And when we got the tag back I think we got

some pretty interesting clues as to why it came off in the first place.

See this? Shark bite marks,

and it's been a pretty big shark too

judging by the distance between those scrape marks.

I think a couple of hundred kilos of biting shark

hanging off the end of this

has been the reason the tag came off the whale shark.

And it could be the reason behind many of the tags failing.

As Fin's journey ends, Mark is left to draw his conclusions

from the remarkable data he's provided.

But 12 months and 20 satellite tags later, is Mark any closer

to unravelling the mystery of where Ningaloo's whale sharks are going?

What I thought we'd see at the start of this study

is we'd tag sharks in Ningaloo and we'd see at least some

go across the Indian Ocean to the Seychelles.

And that's certainly what the genetic data was suggesting.

But that's not what happened.

Moreover, when we looked at the photo identification data,

there were no matches between sharks at Ningaloo

or sharks in the Seychelles.

Hundred of sharks, thousands of photos, not one shark in common.

So I think this is basically wrong.

I suspect what's actually going on

is the sharks that are over here on this side of the Indian Ocean

stay within the same area, and that's certainly what we saw

for the sharks we tagged at Christmas Island.

What does that mean for the sharks at Ningaloo?

Well, actually, I think it's good news.

Look if the sharks are really truly moving all this way over to Africa,

conservation of them is a much more complex question,

but if they're actually just staying over here,

we only have to deal with our nearest neighbours.

Since this study,

Mark has started an ecotourism project in Western Timor.

And now the prospects for Ningaloo's giant fish look a little brighter.

But whilst the whale sharks have given up some of their secrets,

there are still many more questions that will need to be answered

before their future can be truly secured.

Subtitles by Red Bee Media Ltd

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