Natural World (1983) s26e06 Episode Script

A 56-year-old scuba diver was reported missing by his diving partner this morning.
The man's body was found this afternoon.
Police say his injuries are consistent with a crocodile attack.
There's a growing problem in Northern Australia.
Saltwater crocodile numbers have exploded.
If you get in the water, you run the real, serious risk of getting eaten.
Crocodiles are now moving into new territory, travelling hundreds of kilometres.
They are pushing up river, along the coast.
Even far out to sea.
And now they are coming into conflict with people.
It's a nice-looking croc.
A ten-footer.
Looks like it's heading towards Darwin.
Last year, rangers pulled 253 crocs out of Darwin Harbour.
Many of the crocs are around three metres long.
As far as I'm concerned, anybody that swims in Darwin Harbour is mad.
Croc expert Adam Britton is about to spend the next year following every move the saltwater crocodiles make.
In the last week alone, six crocodiles were pulled out of Darwin Harbour.
There have been two fatal attacks on swimmers out at sea.
This is a new and dangerous situation.
To manage it, we have to find out how and why crocodiles are moving.
What he discovers could hold the key to managing this ancient predator.
One of the most ambitious studies ever to be conducted on saltwater-crocodile movements is about to start.
- There's a good one in there.
- Just there, look.
- Big male.
- He's pretty awesome.
He's about 30 foot, 40 foot.
16 crocodiles will be fitted with state-of-the-art tracking devices.
It'll be fantastic to get a satellite transmitter on him.
Hour by hour, they will allow Adam and his team to follow the crocodiles' every move.
I'll put a GPS position in here and then come back at night and look for it.
the Mary and South Alligator Rivers have been chosen for their high number of saltwater crocodiles.
There's a good one down here.
He's a good-size one, that one.
Yeah.
What, 12 foot, 13 foot? If Adam can discover where and when the crocodiles are moving, they'll be closer to solving the escalating conflict between crocodiles and people.
For millions of years, saltwater crocodiles have stalked the tidal rivers of Australia's Northern Territory.
Growing up to six metres, they're the largest and most aggressive of reptiles.
It's very easy for crocodiles to capture attention.
They're just such incredible masters of the domain that they live in.
And When I was young, I used to dream how incredible it would be to be able to follow these animals around, to really learn what they were doing.
If you're a saltwater crocodile today, you've got a dilemma.
The best place to live is the tidal rivers.
That's where the best food is and the best habitat is.
The problem is, it's full of other crocodiles.
There's a lot of big, dominant males.
If you want to stay there, you've got a serious fight on your hands.
And it's these fights which are at the heart of the crocodile problem.
Sizing each other up, two males puff their bodies high out of the water and emit low-frequency warning calls.
It's all about territory, a resource so precious many crocs are killed in these violent confrontations.
The loser's only chance is to move out.
And it's these outcasts, often young males, that this study is targeting.
As twilight comes to the Mary River, the team head out on the first night of the tagging operation.
Night is when crocodiles are most active.
It's also the best time to catch them.
It's quite easy to get nervous when you're doing this.
This is potentially very dangerous.
This animal could cause us very serious injury or kill us if we don't do this right.
We've got a crocodile on the bank right here.
He's a good size.
Yeah, three and a half metres.
It's OK.
We'll get him.
For a moment, the crocodile is blinded.
OK.
Neutral.
- Get the pole.
- You got the snout rope? Keep reversing it out.
OK, slide it on.
Get your hands out of the water.
Hang on.
Ah-ah.
Hands up.
It's dangerous work.
The crocodile's bite is even more powerful than a great white shark's.
At least that means he can't bite you.
Hang on.
That's it.
- You all right? - Yeah.
- Pull him up.
Bit more.
- He'll be perfect for the transmitter.
Got him? An adult male can weigh over half a ton.
Just keep that head forward.
Take him up the back.
This is definitely a feisty crocodile.
We've got a 2.
6m male saltwater crocodile just here.
He's really an ideal animal for us.
So We're going to put a satellite transmitter onto him and release him.
He's not light.
So if I pull this rope, it should release his jaws.
And now he can go.
The first crocodile to be tagged, they've called Wills.
See you later, alligator.
For the next 12 months, Adam and the team will follow his every move.
When we get new technology like this, what we're able to do really for the first time, is have a look at the secret lives of crocodiles.
We can put a tracking device on the back of a crocodile.
We can watch it from the safety of our computer screens, swimming up and down rivers and we are able to really learn a huge amount about what makes a crocodile tick.
And I just found that absolutely hypnotically compelling.
By the end of the night, four more crocodiles are tagged in the Mary River.
For the next year, a satellite deep in space will track their exact positions.
Next morning, they head to Kakadu National Park and the second study area, the South Alligator River.
Controversy continues in the Northern Territory over some of Kakadu National Park's top tourism spots.
A record number of saltwater crocodiles are being found in the area.
The vast South Alligator River cuts a path through the heart of Kakadu.
At the end of the dry season, its upstream waters dwindle to a series of pools called billabongs.
As these water holes dry out, birds, fish and crocodiles are drawn together in ever-denser numbers.
For the crocodiles, it makes for easy pickings.
Ten years ago, these billabongs marked the end of the salties' range.
But every year, they are moving further and further up river.
50 kilometres upstream, Jim Jim Falls lies at the source of the South Alligator.
It's one of Kakadu's most popular swimming holes.
But now crocodiles are moving dangerously close.
As concern mounts over the safety of the falls, Kakadu ranger, Garry Linder, hopes the study will reveal how and when the crocs are moving.
Over the next two weeks, 11 more crocs are tagged in the South Alligator River.
The last to be released, they've called Munmalary.
It's mid-November and one month since the tags were deployed.
Now is the moment of truth.
The first set of data is coming in.
Five crocodiles are sending back signals from the Mary River.
and 11 from the South Alligator.
Already, some interesting stories are emerging.
Adam and data analyst Corey Bradshaw are surprised by the results coming from one Mary River croc.
This is Wills and he was really interesting.
because He did a couple of really interesting moves.
He spent most of the time after release around the spot that he was released.
Then he moved upstream towards the barrage.
In just three hours, Wills covers an incredible 15 kilometres.
The crocodile equivalent of a fast jog.
Now he is sitting close to a manmade barrage that divides the Mary River in two.
It's exciting to finally start getting some data and to see that the crocodiles are moving.
What's interesting about this crocodile is that it's moved such a long way in such a short period of time.
And I'm hoping when we go there, we can find out why.
This is amazing.
The number of eye shines, it's incredible.
There must be maybe 60, maybe 70 crocodiles out there.
Somewhere amongst them is Adam's tagged crocodile, Wills.
As a high spring tide briefly floods the barrage, an extraordinary event begins to unfold one that has never recorded in saltwater crocodiles before.
This is absolutely incredible to see.
The mullet are flying over the barrage.
There are hundreds of them, and the crocodiles are lined up.
We've got a crocodile feeding frenzy here.
I've never seen saltwater crocodiles do this before.
Our tagged croc is actually in this area.
And I'm pretty sure now I know why he is here.
The mullet are heading down river and out to the ocean to spawn.
It's a seasonal event that only occurs on an extreme high tide.
It's just incredible to see these animals, normally so territorial, tolerating each other because there is so much free food available.
How have so many crocodiles tuned in to this one event? Wills travelled 30 kilometres in two days just to be here on this night.
Not only does it suggest crocs have a remarkable understanding of their environment but also, that their movements are far from random.
As the tide turns and the flow begins to subside, the crocodiles turn their attention to the bank.
Oh! A lucky escape.
Just one month in, the discovery of this event offers remarkable new insights into crocodile behaviour.
The next morning, some of the world's most aggressive predators are lying side by side, digesting the night's catch.
Nowhere else are saltwater crocodiles known to tolerate each other in such numbers.
30 years ago, crocodiles were hunted to the brink of extinction in Northern Australia.
But thanks to a hunting ban, their numbers have increased from 3,000 to 75,000.
It's a conservation success story.
But has it now gone too far? It's now December and the monsoon is taking hold.
For weeks at a time, the rain is almost constant.
Overnight, the billabongs are transformed into flowing rivers.
The crocodiles' world has changed beyond all recognition.
Released from their billabongs, they're starting to explore the newly-flooded landscape.
Cattle ranchers are keen to see the reintroduction of controlled culling of saltwater crocodiles.
They say the high number of stock attacks is becoming a serious problem with some stations reporting hundreds of losses.
The Mary River runs through the heart of cattle-station country.
Just Upstream from the barrage, ranchers are concerned at the rise in attacks on livestock.
The crocodile population up here is getting out of hand.
There's far, far too many of them.
It is getting to a stage now where anywhere you go up here, there's crocodiles in the water.
We've always got someone on watch and if they do see a crocodile, we don't shoot at the crocodile, we shoot around it to try and deter it away.
You're not allowed to shoot them unless one's got hold of you, and then it's too late.
As temperatures and humidity rise, the distant thunder triggers the crocs to start breeding.
Blowing bubbles, a dominant male gently woos the female, until finally, the love match is played out underwater.
An arching back and the joining of bubbles are the only visible sign of their union.
The mating season will continue for another two months.
During this time, the males will have to fight hard to defend breeding rights.
And for those that lose out, the struggle to find new territory continues.
It's now January, and three months since the study began.
.
.
the Mary River, about 20 miles away at the moment.
The first crocodile we're gonna be looking for Adam's team have just received some exciting new data.
It's Wills again, who was last located at the feeding frenzy next to the barrage.
What we're seeing just outside the helicopter This is Shady Camp.
This is the barrage.
We were standing on this only recently, looking for one of the crocodiles.
Now the crocodile has moved from here all the way downstream, out to the coast, so we're gonna fly all the way to the coast to see if we can find this animal.
In one week, Wills has moved 85 kilometres.
From the barrage, he travelled downriver reaching the sea at 2am, on the 18th of January.
Since then he has been hugging the muddy coastline, steadily moving west towards Darwin.
We do know that crocodiles move around the coast.
That much isn't a mystery.
What is a mystery is how much time they spend around here and how they actually do it.
We know that they can tolerate saltwater but we don't know how much they can tolerate it.
Saltwater crocodiles are the only ocean-going crocs in the world.
But battering waves and salty water make it a gruelling place to be.
More accustomed to life in tidal rivers, crocodiles can't drink and rarely eat whilst at sea.
How is Wills surviving out here and where is he going? We are getting a pretty good signal from this croc.
This is looking pretty hopeful.
Look at this guy.
This guy is actually He's pretty much buried in the mud.
Look, there he goes! This is one of the crocs.
He's got a transmitter on the back of his neck.
OK, that's fantastic.
If this crocodile keeps moving west, he'll end up in Darwin Harbour.
Then he'll be a problem crocodile.
In a five-kilometre stretch, Adam spots ten more crocodiles.
There's another one.
I'm actually amazed how many crocodiles are out here.
They're all over the place.
It's an unexpected result.
It not only confirms that the Mary River crocodiles are pushing into the sea but they're doing so in huge numbers.
I'm really stoked by all this.
We've got some fantastic data.
To see so many out here is just fantastic.
It tells us a huge amount about the populations of crocs in these rivers.
It's strong evidence that the Mary River is now full.
But where are the crocodiles going? Parks and wildlife rangers have had a busy start to the year, catching 19 crocodiles in the last month alone.
Saltwater crocodile numbers are at an all-time high.
Last year, rangers pulled 253 crocs out of Darwin Harbour.
Darwin is on the front line of the crocodile invasion.
And keeping its waters safe is a never-ending task.
As soon as one crocodile is removed, another quickly takes its place.
Yeah, terrified.
I'm terrified of crocodiles.
I wouldn't swim in Darwin Harbour.
Not if you paid me.
As the croc problem escalates, the pressure is building for the study to deliver some answers.
It's now February, and the satellite tags have been sending back data for four months.
As the Mary River crocs continue to move along the coast, Adam receives news of crocs being sighted far out to sea.
We have reports, fairly frequently, that people who work on oil rigs, people in ships, they'll see crocodiles swimming past.
Now, those animals can be 300-400 kilometres from the nearest land.
What are they doing out there? Adam is on his way to investigate some unusual sightings on the Tiwi Islands, north of Darwin.
To make the 100-kilometre journey from the mainland would take a crocodile around a week.
Millions of years ago, the crocodiles' ancestors were giant reptiles that ruled the seas.
Travelling huge distances, they colonised the tropical world.
And today's saltwater crocodiles retain many of their prehistoric features.
Inside their mouths, tiny glands are working overtime to excrete enough salt to overcome the oceans' saline waters.
Along its back, blood-filled plates absorb the sun's heat, warming its muscles for the journey ahead.
And with a tail that makes up half its body length, it can move through the waves at speeds of up to 10 kilometres an hour.
Just like their ancestors, today's saltwater crocodiles are once again moving into the oceans.
As night comes to the Tiwi Islands, a crocodile is waiting in the surf.
It's 9:00 at night.
We're on a beach on the north of the Tiwi Islands.
I'm with turtle biologist Scott Whiting because Scott has witnessed saltwater crocodiles attacking flatback turtles.
I think it's 100% that we'll see turtles.
Whether we see crocodiles is another thing.
But as they approach the turtle nesting site, they realise they're being followed.
A crocodile, just there.
It's gone.
There was an eye shine just there.
Yep, there is he is, look.
No, he's gone again.
Look.
He's just bobbing up and down in the water.
But he's definitely moving this way, and he's going quite fast.
It's very exciting to see a crocodile in this kind of a situation.
To be honest, it's the first time I've ever seen a croc on a beach at night.
It's made me a little bit uneasy.
You just couldn't see the crocs coming.
They'd be able to launch themselves out of the water so I'm gonna stay a safe distance away from the edge.
Further down the beach, a flatback turtle hauls herself out.
Now she is at her most vulnerable.
It takes just half an hour to lay her eggs.
But every second she is out of the water, she is in danger from the crocodiles.
- Wow, look at these tracks, Adam.
- Whoa.
We're standing on them.
You can see what's happened.
Turtle's come up, crocodile's followed it.
You can see clearly the imprint from his scales between each of these footprints.
There's no signs of a struggle or no blood, or anything,so obviously the croc missed its target.
Yeah, I think so.
It's pretty exciting to see these tracks, to see this story in the sand here.
Um It's just a bit frustrating that we missed, unfortunately.
I think what this shows is that saltwater crocodiles are not only using the coastline for moving but there's also a potential source of food here.
So it really raises the possibility that crocodiles use islands such as this as staging posts on a longer journey.
With increasing evidence of crocs spending long periods at sea, could this be the start of a wider problem? Are crocs now leaving Australia to colonise new continents? It's now April.
Two more crocodiles from the Mary River have joined Wills on the coast.
And as water levels rise, the billabong crocs on the South Alligator are becoming more and more active.
But it's a crocodile that's barely moved at all that attracts the team's attention.
He's called Munmalary.
Do you remember that animal, he was a male about 3.
5 metres? - We got him about 30 kilometres - I remember.
The South Alligator here.
And He's moved five or six kilometres up that area and he hasn't moved at all.
To find out why Munmalary is so in active, Adam and Garry head back to the South Alligator.
They suspect Munmalary is either trapped between the territory of two dominant males or that he is the boss croc, and this is his area.
As the signal gets stronger, Adam spots signs of a crocodile nest near by.
It looks like there might be one just over here.
In fact, there is.
I can see it.
There.
A nest back there.
I can't see the female but she might be in a wallow, hidden there.
So it's going to be very dangerous for us to go in here.
She might rush out at us, so what we're gonna do is go a little bit further upstream and then we can walk along the bank and we can come from behind.
To find out if the nest is active, they must open it.
It's extremely dangerous.
From a standing start, a crocodile can explode at speeds of up to seven metres per second.
It's a fairly big one.
It's a good-size nest which means it's a good-size female.
They still have no idea where the female is hiding.
It's often a good idea to bang the ground like this, because if she is hidden, the vibrations from this can bring her out or even make her flee.
- Adam, she is coming out of the water.
- OK.
Come here.
A nice-looking female.
Well, this is the female.
She's actually come back to the nest.
So Us disturbing it has attracted her.
So she's obviously a little unsure what to do now.
There's a good chance she's going to come up towards us.
We have to be very careful.
You want to check those eggs and I'll give you a yell? OK, well, this is your classic saltwater-crocodile nest.
She has grabbed all of this grass, this vegetation, from around here, and she's just stacked it all together and compressed it down.
Hopefully, she laid some eggs.
That's what we're looking for.
Is this an active nest? It's incredible how tightly they pack the vegetation when they build these nests.
It's often a really good indication that the female needs to be here to open it when the eggs hatch out because imagine being a baby crocodile trying to get out of this.
OK, we've got some eggs.
Excellent.
So basically, this is a very good reason for Munmalary to stay in this area.
to stay in this area.
The ability to breed.
Munmalary could father as many as 300 crocodiles this season.
And with up to 1,000 nests being laid in Northern Australia this year, salty numbers continue to rise.
But before the team can locate Munmalary, they are forced to return to Darwin.
Residents in the Northern Territory capital, Darwin, are on high alert as Cyclone Monica continues on its destructive path.
The category-five tropical cyclone is one of the biggest in the Territory's history.
The cyclone cuts a path straight through the study site, decimating the landscape.
It's still not clear what effect it's had on the crocodiles.
Early this morning, severe tropical cyclone Monica passed across the South Alligator River.
At that point, it was packing winds of 350 kilometres an hour.
In extreme weather conditions like this, it's going to be very difficult for crocodiles.
It's an unprecedented opportunity to study crocodile behaviour in cyclone conditions.
As the data comes in, it reveals that two days before the storm, the Mary River crocs, Wills and Kelly, moved to the relative safety of the river.
It suggests they knew the bad weather was approaching.
But the data is limited.
Only half the satellite tags were able to transmit.
It's likely their aerials were hidden as the crocs sought refuge underwater.
Large crocs can dive to around ten metres and hold their breath for more than two hours.
Deep underwater, the storm passes by barely detected.
This ability to predict severe weather has never been reported in saltwater crocodiles before.
As the study draws to a close, Adam and Garry make one final expedition down river.
Across Northern Australia, it's the crocodile hatching season, and Munmalary's babies are about to emerge.
The female has been guarding her nest for the last 80 days.
- Strange calls fill the air.
- (Bleating) It's the sound she's been waiting for.
Ripping into the compacted grass, she sets the young crocodiles free.
Then, by one by one, she gently carries them down to the water.
Within 24 hours, her clutch of more than 50 eggs have hatched.
All over the Northern Territory, thousands more are taking to the water.
Garry, there's a bunch of eye shines on the bank here.
- That's mum there, is it? - Yeah, that's the female.
It's pretty impressive when they move like that.
There's about three of them here, Garry.
Oh, wow, there's so many of them.
It's incredible.
I've seen the odd hatchling here and there.
I've never seen so many hatchlings like this, together, feeding at once.
It's an amazing site, to be honest.
Baby crocodiles grow up fast.
Already they're skilled hunters, killing these mudskippers with a single bite.
For the moment, their mother watches over them.
But in three months' time, these tiny crocs will be on their own.
It's pretty exciting.
This could possibly be one of Munmalary's young.
It's a bit frightened now, doesn't know what's going on, so it's producing this ''ow-ow''.
It's calling out for the female, the mother, who is just over there.
Something like this looks so cute and innocent.
And yet ultimately, this could be the animal that becomes a real problem.
OK, I'm just going to release this one here.
Good luck, fella.
No, you've got to go that way.
Well, it's been an amazing night.
We've seen that there are a lot of hatchlings on this river.
We've found several groups of them and we've seen some pretty amazing behaviour, we've seen all these animals feeding and they're doing it now in front of us, taking all of these mudskippers, it's something I've never seen before.
What it's proven to us is that this is an incredibly productive river system.
Latest estimates put the salty population in Northern Australia at 75,000.
Whilst only half of these hatchlings will survive their first year, there's clearly a lot more problem crocs on the way.
For the past year, 16 crocodiles have been transmitting their daily positions.
Now the study is coming to a close.
As the data comes in, finally some patterns are emerging.
We've got the biggest movements from the river with the highest density of crocs.
- Which is what you'd expect.
- It's a fantastic result.
The crocodiles in the overcrowded Mary River have moved further and faster than anyone had expected.
Moving up and down the coastline, they've surprised the team by crossing the difficult waters of Cape Hoffen.
It's a crucial piece of information.
It suggests that crocodiles from the Mary River are capable of swimming the 150 kilometres to Darwin.
And they can do it in less than a week.
For Darwin's residents, it's sobering news.
It means that crocodiles could turn up at any time.
But on the South Alligator, it's quite a different story.
Adam and Corey are surprised at how little the crocs have moved.
This inactivity can only be good news for Kakadu.
But then some alarming data comes in.
The Northern Territory had its wetest April since records began 65 years ago.
Extensive Flooding in the top end has closed major highways and swimming holes, disrupting the start of the tourist season.
We've just got some very interesting data from one of our crocodiles.
The crocodile called Mullet has moved about 20 kilometres upstream and is swimming straight towards the Jim Jim Falls swimming area.
That means he's going to be a big problem.
It's frightening news.
A late flush of rain has allowed Mullet to push upstream, covering 20 kilometres in just ten hours.
This area here, We're just coming up to Jim Jim Falls, which is ahead of us, it's very rocky, very stony escarpment country.
It's not the kind of habitat that you'd associate with saltwater crocodiles.
Ten years ago, you wouldn't have found salties moving this far upstream.
But they're certainly there now.
To get to the falls, Mullet has to climb several stretches of rapids.
It's a difficult and exhausting journey.
But with the sudden rise in water levels, he does it with unexpected ease.
As 11 more potential man-eaters are spotted in the area, Garry closes the falls.
It's the first time in the park's history that so many crocodiles have been found this far up river.
It suggests that salty behaviour is changing.
For Garry, this new information could save lives.
Now, when water levels rise, he'll be putting Kakadu on high alert.
I think the most surprising result for me was the speed at which these crocodiles were capable of moving.
And it's raised a very interesting management issue.
That is that even if you find an area has no crocodiles in one day, it doesn't mean to say there isn't going to be one in there the next day.
I think Crocodiles have got a place in the Northern Territory but we obviously have to make sure that crocodiles and people are not coming into conflict.
That means there are places where we have to control them, to keep them from killing people.
It's a balancing act and if we don't get the balance right, then the consequences for either species could be fatal.
Getting the balance right is never going to be easy.
But this study is a critical first step in managing the future of this ancient predator.