I am zoologist and adventurer Nigel Marven.
I've spent my whole life searching the world for the largest animals alive today.
But I've always wanted to meet the ultimate giants,
to go on a prehistoric safari amongst the largest land animals ever...
(GROWLS)
..to travel back in time and walk with dinosaurs.
Just imagine that this line here represents 225 million years BC,
the time when dinosaurs first evolved.
Right over here, this represents 65 million years BC,
the time when the great reptiles became extinct.
And I'm precisely here -
100 million years BC, in the Early Cretaceous.
This magical place will one day become Argentina.
I've always wanted to come here,
because the dinosaurs that live here, they're the biggest ever.
This is the skeleton of an Argentinosaurus,
the largest land animal that ever lived.
Look at it. It must be over 100 feet long.
Even so, some of these massive skulls have got puncture marks in them
from formidable and dagger-like teeth.
What sort of predatory dinosaur could take out prey as large as this?
It can't have been T-rex. They haven't evolved yet.
It was a predator that was even larger.
This is the setting for some titanic battles.
The biggest prey of all time...
The biggest predator of all time...
Just imagine a hunt like that,
and it happens here every year.
(ROARS)
Any day now, this area, just a mile from our camp,
will witness an extraordinary influx of giant dinosaurs.
Every year, a herd of Argentinosaurus visits this lake,
and every year, giant predators gather to hunt them down.
This is such a special place
because the Argentinosaurus come here to lay their eggs.
This shore on the edge of the lake is the perfect nursery for them.
Look. There's eggshells scattered all over the place here.
That gives you a good idea of what these huge animals hatch out from.
Quite small beginnings. The full egg is about the size of a football.
This is exactly as I suspected. Look.
The females come year after year because this is the perfect place to lay their eggs.
I can't wait till the herd come back to lay their eggs for this season.
But the first dinosaur I spotted here was hardly a giant.
At least, not yet.
This can't be anything else - it's a young Argentinosaurus,
just three or four years old.
It's stayed around the nesting area. There must be good food.
She's too young to travel with the herd. It's amazing to think, if she survives,
she'll grow up to be as large as those skeletons that I saw.
(BELLOWS)
Even standing next to a baby was quite an experience.
What would it be like to get close to an adult Argentinosaurus,
some 60 times the weight of this one?
I could hardly imagine it.
Flippin' heck!
I'm smiling...because of the shock of that.
It scared me out of my skin.
I'm pretty sure I know what it is.
It's not a crocodile, even though it looks like one, but it's a close cousin.
Called Sarcosuchus, it grows much bigger than crocodiles.
I'm not mad. This is a calculated...risk.
Sarcosuchus should behave like its modern relatives, crocodiles and alligators,
and I've done this with them.
What I'm worried about is that he's got some mates around here.
As long as you keep your eyes open...
Come on. Come on.
These are the sort of splashings that prey would make, and...
I just saw a swell. Get back. He's coming...closer.
Come on.
Wa-hey! What a stupendous reptile!
He must be over 40 feet long.
He'll be a real threat to the herd.
When they come to the nesting site, the Sarcosuchus will be waiting.
So the young Argentinosaurus, they could be taken by this creature.
He's basking on the bank now. I've done this before with a 12-foot alligator -
put a minicam on my head and looked inside the mouth.
The principle should be the same with a 40-foot Sarcosuchus.
I'm just feet away from a 40-foot Sarcosuchus.
I've got my stick. It's not much defense.
That's a great view of the teeth with the head-cam.
Watch this. The mouth is open, but I'm gonna gently touch that mouth.
(DISTANT ROARING)
We can't just sit around and wait. This is an active way to look for the herd.
If I can get high, I should see for miles
and get a view of them if they're anywhere near here.
(DISTANT BELLOWING)
At last...some dinosaurs.
It's not the herd I'm looking for. These are a kind of Iguanodon.
But these are very successful dinosaurs. They've been around for 45 million years.
They'll be around for another 30 million years. 75 million years on the Earth.
They colonized every single continent.
(SQUAWKS)
My search for the elusive giants was taking me an increasing distance from the lakeside.
To find their migration route, I even went as far as the ocean.
I've come all this way to find this coastline is too steep for big animals...
Whoa! (LAUGHS)
..for big animals like Argentinosaurus to move along.
But this was a perfect habitat for another kind of oversized reptile,
which was obviously thriving here - pterosaurs.
This is one of the most thrilling sights in the prehistoric world.
There's Pteranodons soaring all around me.
I've sneaked up to this one. He's just digesting a fish.
I'm just eight feet away.
It's only when you get this close that you realize just how huge they really are.
This one, the wingspan - it's a big male - it would be over 20 feet from wing tip to wing tip.
So how do flying creatures like this get to be so huge?
It's because everything about them is designed to be lightweight.
The bones are hollow, and these membranous wings,
the only support is thin and flexible rods.
They're more like bat wings than bird wings.
Being so big, it's difficult for pterosaurs to take off.
That's why these sorts of habitats - cliffs and canyons - you find them here most often,
because they rely on prevailing winds to literally take them off.
I hadn't found the giant dinosaurs, but they had found me.
What the heck...?
Flippin' hell!
There's been a big animal here.
Look at those...slash marks.
The whole place has been trashed.
Look at this, quick!
A dinosaur tooth trying to bite into this can of meat,
and it is a massive one.
There must have been a very big predator in here.
(DISTANT ROARING)
I didn't sleep a wink.
You expect it on dinosaur safaris...
..but I was petrified.
I never thought I'd be scared.
We've rigged up this device, an early warning system.
(ALARM SOUNDS)
Maybe that would have frightened it away, but look at the damage.
It's just scared me witless.
This is even more terrifying in the daylight.
Look at that for a tooth. There's still dinosaur gum attached.
But the predator won't miss this. Dinosaurs are like sharks and alligators.
If they crunch into something that's too hard, these teeth are specially designed to be lost.
Some dinosaurs, they can go through 500 teeth in a lifetime.
But that is a formidable weapon.
We're tracking the predator.
There's a trail of trampled vegetation down to this river bed.
No more plants to tread on, but it's still an easy trail to follow.
Look at that for a dinosaur footprint.
Whenever you're following a big animal, you don't want to surprise them.
The trouble is, my eyes are skinned,
but any tree, every shadow, seems to be a big dinosaur.
Look at that. Three of my size 11s in just one toe.
But the stride pattern has changed here. There's not such a big gap between prints.
It's as though it stopped
and listened or looked or smelled.
Maybe it's stalking something.
We're a few miles from camp, and there was a terrific noise,
just up ahead, as if animals were fighting.
Something's happening. Come on.
(ROARING IN DISTANCE)
The trail of blood led me to a badly wounded Iguanodon.
(GRUNTS)
This must have been what that commotion was. Look at that injury.
It's either been bitten or clawed,
and luckily they can recover from injuries that would kill a mammal,
and hopefully she's gonna be all right.
The predator can't be far away now.
A little scary, but it must be magnificent.
There's more blood here.
That is very fresh.
And there's another drop.
Just a little further on, I came face to face with the killer.
There it was - the biggest land predator ever, with a dead Iguanodon at its feet.
It couldn't be anything else, a Giganotosaurus.
Paleontologists reckon that that predator weighs two tonnes more than T-rex.
That must have been what wrecked the campsite. That shook me up a bit, but really it's good news.
These big predators wait for the herbivores like crocodiles waiting at river crossings in Africa.
And because he's here, the herd of Argentinosaurus can't be far away.
(GROWLS)
Time to bring in some 21st-century technology.
I can't believe this. They're all around me. On every wing tip, there's a pterosaur.
Ha-hey!
I've seen this with vultures. They're not frightened by the noise. That is fantastic!
Flying with pterosaurs.
I can't believe it. It's the biggest pterosaur ever - Ornithocheirus.
We've got a wingspan of 26 feet in this ultralight.
They've got a wingspan of 40 feet.
And look at that gliding. That's the biggest creature that's ever flown.
There. That's what we've been looking for.
There's the herd down there.
And they are massive, even from up here.
Even from a few hundred feet, they look huge.
A pterosaur's-eye view of Argentinosaurus.
There's at least a dozen down there.
(DEEP BELLOWING)
I have just flown with the biggest creature that's ever flown,
and, most importantly, we've located the herd.
They were going that way. There's another big volcanic lava field.
I want to see them on the ground.
At last, this is what we've been waiting for,
and we have got to hurry.
This was the herd all right, now just 20 miles from the nesting site by the lake.
(RUMBLING BELLOW)
And here was my chance to do a bit of dino-science.
The herd are just over there. They're coming this way.
I want to try an experiment, but I've got to work fast.
Paleontologists think Argentinosaurus was the heaviest creature ever to walk on land,
and this is an opportunity to corroborate that, to actually weigh a dinosaur.
These are weighing pads for lorries
that are a bit more robust than normal bathroom scales.
And if I get them in position, if the dinosaurs walk on these, I can weigh them.
Given the size of the Argentinosaurus,
it would take quite a few plates to cover enough ground.
Wired together, these should work like one big weighing machine.
This is working like a dream.
They're funnelling through the gap, the whole herd.
All we need now is for one to step on those plates.
Come on. Come on.
Just missed. One foot on a plate there. They need all four feet.
Come on. There's one coming right in line.
Yes. I think he's on the spot. Let me check that.
Yes! 92 tonnes. That's about as much as 30 African elephants.
The herd was now entering the most dangerous phase of their migration.
Between them and the nesting site, fearsome predatory heavyweights were lying in wait.
After yesterday's weigh-in, we left the Argentinosaurus herd here.
They were skirting the edge of this forest, heading east towards the nesting grounds.
They can't move very fast, so hopefully we can intercept them.
Iguanodon. That is beautiful!
Gorgeous! It moves so beautifully.
Watch out! Look at that behind!
We're being chased!
Come on! What a monster!
(ROARS)
Wow! My heart is still hammering.
Having a big predatory dinosaur virtually breathing down your neck...
That was terrifying!
It gives you a tiny idea of what it's like to be an Argentinosaurus.
Every time this brilliant herd goes to its breeding grounds,
they have to run a gauntlet of these big predators.
There's five or six Giganotosaurus,
and they are trailing the back of the herd, looking really interested.
But what I was about to witness would be nothing like the explosive pursuits
of lions hunting zebras.
This kill would be far from quick.
It doesn't feel like it, but we've been following the herd
and the attacking Giganotosaurus for over an hour now.
They've selected a victim - a young female, I think.
What they've been doing is running into the herd, testing for weaknesses.
And now I think the hunt's gonna start in earnest.
This is getting very serious.
I kept following the herd as they slowly made their way towards the lake.
Time after time after time, the Giganotosaurus attacked the female,
trying to separate her off from the rest of the herd.
This hunt's gone on a remarkably long time - virtually all day.
They are relentlessly pursuing that young female.
They're biting her, trying to wear her down from blood loss and exhaustion.
Working as a team, the Giganotosaurus can tackle large prey like this.
If they can bring down this Argentinosaurus, they won't need to feed again for a few months.
(GROWLS)
(ROARING AND BELLOWING)
The ultimate hunt. This is what we came all this way for.
But now it's just too harrowing.
You can hear the distress calls of the Argentinosaurus.
She's trapped somewhere down there. They just go right through you.
It's just about too dark to film any more...
and for once I'm pleased about that.
(DISTANT WAILING)
This is a magical end to my dinosaur safari.
The drive to breed is why the Argentinosaurus herd make their perilous journey.
And this is why they do it. The females, they're all egg-laying.
I don't want to get too close and disturb them. I'd hate to get caught in a stampede.
There's no place or time that's quite like this.
Look at them. How do I feel?
Well, when you're next to giant dinosaurs, it makes you feel so incredibly small.
Watch out!