Fugitive from the Fire Survivors: Nature's Indestructible Creatures

Since the emergence of life, more than 3 billion years ago,

life on our planet has suffered a series of devastating mass extinction events.

These have killed off uncountable species,

and even threatened to end life on Earth altogether.

I'm Professor Richard Fortey, of London's Natural History Museum.

I've spent all my working life studying the remains of animals long extinct.

'But now, I'm leaving the vaults

'to discover why some animals and plants have survived.'

Hello, snakey.

'I'm going in search of living fossils,

'old-timers...'

This little face.

'..that somehow managed to survive when so many others perished.'

Rubbery hardly does it justice.

'In the process, I hope to find an answer to a profound question.'

Is being a survivor a question of having some very special features?

Or nothing more than pure chance?

'From living fossils that are our most ancient relatives...

'..to gigantic relics from the age of the dinosaurs.'

Life as we see it today is not just the product of evolution,

it's also a consequence of mass extinction.

We are all the sons and daughters of catastrophe.

Oh, my goodness!

More than 100 million years ago, the Cretaceous Age already had

highly sophisticated and complex ecosystems.

There were flowers, and plants that we might recognise.

There were insects, birds and even tiny mammals,

though not yet butterflies or bees.

And there were amphibians and reptiles,

especially very big reptiles, like dinosaurs.

Then, one day, 65 million years ago,

this world came to a sudden end

when a 10km-diameter asteroid collided with the Earth.

The impact is believed to have struck the Earth

with the force of 96 teratonnes of TNT,

causing colossal shockwaves,

tsunamis perhaps hundreds of metres high

and so much hot ash and debris, the global atmosphere became superheated,

igniting wildfires all over the world.

It was the end of the long reign of the dinosaurs.

I used to walk with dinosaurs or, more accurately,

pass them every working day on the way to my office

in London's Natural History Museum.

But what I want to know is, what were the lucky breaks

and evolutionary adaptations that allowed some species

to survive the disastrous end of the Cretaceous Age

when these marvellous giants did not?

Locating the scattered survivors of the KT extinction

is not as straightforward as you might imagine.

'You never know quite where they'll turn up.'

OK, 42nd Street.

'The survivor I am looking for not only outlived the dinosaurs,

'but apparently several of them even survived the dropping of the atom bomb on Hiroshima

'at the end of World War II.'

Well, this is a jungle of sorts,

an urban jungle.

We are right in the middle of Manhattan,

but even here, lurking in some corner, there might yet be a survivor.

There's hardly any space here for anything green.

In fact, hardly any space for anything living,

except lots and lots of human beings.

Strangely enough, there's one over there.

If something can survive the pollution and the heat

of a summer in New York, not to mention miscellaneous garbage,

then that is a pretty tough organism.

And that's exactly where we find the gingko.

Ginkgo leaves are fan-shaped or triangular, really beautiful leaves,

combining a perfect design and a certain toughness,

which may of course have helped them through these crises.

Gingko trees can now be found

all over the world.

But until two centuries ago,

they could only be found in one isolated region of China.

Sometimes living for more than a thousand years, they're extremely tough.

The gingko tree is an example of perhaps the simplest survival strategy of all.

If you're tough enough to cling on somewhere,

even a tiny area in one part of the globe,

a chance may yet come to recolonise the world.

The KT event was so destructive,

it reduced even this tough species

to a tiny rump population clinging on in one remote location.

So, it may not be surprising

that nearly half of all animal and plant species

perished in the destruction.

What is perhaps far more surprising is that

relatives of the dinosaurs managed to survive.

In Queensland, Australia,

I prepare to meet one of the largest animal survivors

of the KT extinction event.

Guys, look, what I'm going to do this afternoon is

I'm going to dispel the difference between fact and fiction about these animals.

Now, what most people see...

Crocodiles are found in tropical climates all over the world.

The croc is a formidable predator

that's responsible for the deaths of 2,000 people annually...

..a fact that handler Clay Mitchell is acutely aware of.

A male saltwater crocodile can grow to be seven metres long

and weigh up to 1,000 kilos.

It's a survivor for whom surprise and ferocity are key weapons.

Its jaw can snap shut at lightning speed

and its mouth is filled with 66 hollow teeth.

These are constantly being renewed by fresh replacements growing inside them.

A single crocodile can get through an incredible 2,000 teeth in its lifetime.

And since the oldest crocodile in captivity survived until it was 140 years old,

well, you can see why it's got such a lot to smile about.

Go on.

We might let him get his breath back, eh?

LAUGHTER

It's not easy to teach a crocodile new tricks.

But then, it doesn't need them.

Crocodiles have remained unchanged since the Jurassic Age,

the golden age of the dinosaurs that began nearly 200 million years ago.

They are cold-blooded, highly efficient killing machines

and, above all, they can wait.

If pushed, it's not fussy about what it eats.

I mean, I know it'd eat us if it's feeling a little bit peckish.

So, it could survive on anything from the small to the humongous.

It's a tremendous advantage to be able to feed only occasionally and then well,

and when you get something not to let it go. Cos...

if you can go without food for six or seven months, you can weather a crisis.

A born survivor, this one.

Being able to eat almost anything,

it's a good way to stay alive in lean times.

But to get through utter devastation you need something more.

The question we really want to know is,

why did this particular kind of animal come through the big crisis

at the end of the Cretaceous

and dinosaurs, their contemporaries,

in some ways more superbly adapted, you might say, didn't make it?

I think probably one would be its ability to utilise food

a lot more efficiently than us.

These guys have got a very slow metabolism,

so a little bit of food goes a very, very long way.

So I could probably definitely say he could survive

for eight or ten months without eating absolutely anything.

And probably versatility might have been a factor too.

They've got this famous structure, the nictitating membrane, isn't that right?

-That's correct.

-It sounds vaguely obscene, doesn't it?

-Ha-ha, it does.

Perhaps you could explain what that is.

It's very simple. Look, they have three eyelids.

So what they do is they have a top one and a bottom one,

and the nictitating membrane is one that actually moves on the inside of those two eyelids

from the front of the eye to the back of it.

When they go under the water and do these sorts of things,

that nictitating membrane does move across the eye.

So, the minimum exposure position is basically just to have that nasal disc

with the two nostrils above the water

-and you can see how the eyes project at about the same height.

-Yeah.

So, all they need is to be able to see and to be able to breathe,

and the rest of the body can remain completely concealed below the water.

One of the reasons crocodiles survived and dinosaurs didn't

may be because the same skills that made it such a master of ambush by hiding underwater

also saved it from the fiery devastation that swept across the world.

Of course, just to point out one thing, which you said it was half tail.

That half tail contains some meat, and the meat is presumably quite edible.

-Definitely.

-So, perhaps we should go and try it.

Yes. Well, I'd say, I think our chef does a pretty good job with it.

I think it's actually a meat with a little bit of bite.

THEY LAUGH

'I have to admit that I'm curious to try eating crocodile.

'After all, it's almost like eating dinosaur.'

-You might as well try one of those, mate.

-All right, let's see. It's a... ha-ha...

Cheers, mate.

Mmm...

Mmm...

It's pretty good.

Meaty, succulent.

It's sort of, um... more pig than fish.

In fact, you might call it Jurassic pork.

He-he-he! Certainly.

All it takes is usually some celebrity chef to get on

and actually do a little bit of a dish to actually encourage

people just over that fence to go out there and actually try it for themselves.

The more people that try it, I think, the more popular it will actually become.

65 million years ago,

it wasn't just dinosaurs that got exterminated by the impact.

Perhaps as many as half of all plant species were also blasted, never to return.

Some of the same survival strategies the apply to animals like the crocodile

were also appropriate for the plant world.

Plants that survived the KT also needed ways to hide out and bide their time.

One way to survive a disaster is to go NUTS!

These podocarp seeds are extremely tough, durable time capsules

that can fall to the ground and germinate after the KT events had passed over them.

The shell on a nut is a good way to protect a seed from fire,

but some ancient species have even adapted to endure periodic fires

as part of their life cycle.

Such species include many cycads.

Which is why I'm going to meet cycad expert and enthusiast Gary Wilson.

'Gary leads me down to the forest trail on a cycad safari.'

Well, that's quite a tree.

And I suppose it might be quite old.

Yes, certainly.

This one I would suggest, and it's a little difficult to age them, 400 or 500 years, perhaps.

To an untutored eye, it might look a bit like a palm tree,

but it's not related to a palm, is it?

This is one of three types of cycads that is found here

in this Wet Tropics Region in Daintree, in North Queensland.

In that way it's a living laboratory

for these evolutionary survivors across time barriers and extinction events.

This is a green dinosaur.

This predated the dinosaurs and has survived them.

I think they've even found masticated remains of these things...

-That's correct.

-..in dinosaur coprolites or dinosaur poo, fossilised.

And found cycad fragments inside, so this was part of dinosaur diet.

-They went, but their food plant survived.

-Survived.

And that's an interesting question.

Any theories particularly why?

The strategy that ensured the success of the cycads as a group of plants is this,

it's a time machine, it's a seed.

It contains a nutrient reservoir.

It contains an embryo, it can travel through time,

through seasonality, through extreme events.

Cycad seeds from some species even need fire to reproduce.

With rainfall, nutrients in the ash trigger germination.

'To ensure its survival, the cycad fruit has evolved an additional strategy -

'poison.'

It contains a suite of novel compounds that make it unattractive to things eating it, for instance,

or that would be eating it.

Cycads are the only plants on the planet

that incorporate mercury in their tissue.

-That's very nasty indeed, isn't it?

-Very nasty.

'More delicate plant survivors needed subtler tactics to survive the KT crisis.'

In my own garden is a survivor that only made it because of a helping hand.

Or should I say proboscis?

Magnolia blossom announces itself from afar

like a small flock of pale, untidy birds that have become entangled in the branches.

When this first evolved,

this plant was pollinated not by the bees and butterflies

that we are so used to today, but by beetles and other insects.

'The first magnolias appeared around 100 million years ago.

'And a few days each year, it's still visited by its ancient pollinators.'

Got it! Look, look, look, look, look! There they are.

There's our little beetles.

Isn't that nice?

There's one going up the petal.

Without these tiny insects, flowering plants could not have survived.

Indeed, the survival of insects and other small invertebrates

was crucial to the survival of many other species.

Even so, the early flowers and their pollinators both only just scraped through.

Why did it survive? Well, it was pollinated by beetles and other insects.

Those insects carried through too and survived that big extinction event.

But also it had seeds. And the seeds could survive in the soil.

They didn't need to germinate every year. Perhaps they could outlive the hard times.

And I don't think its antiquity has diminished its beauty one iota.

Even those few plants that made it were ravaged and stressed.

As plant species after plant species withered and died,

so too the giant herbivorous dinosaurs also vanished.

And, in turn, the carnivorous dinosaurs that preyed on them.

To survive, many animals also needed to behave a little like seeds,

going underground and quietly enduring.

A strategy like this may well have saved the snakes.

'Snake handler Shane Neal has agreed to show me

'a few of the snake family's more illustrious members.'

-Hello, Shane.

-Hello, mate.

-Nice to see you.

-Nice to see you too.

-I gather you've brought me a load of different snakes.

-I have, indeed.

-Can we have a look?

-Absolutely.

-Ah! Now, that's an impressive snake.

-It is indeed.

-What do we have here?

-This is an olive python.

Would you like to hold it?

-Ah... Is this the one that likes to be held?

-It is one.

-Oh, all right.

-Do you trust me?

-Sure, I trust you. Yeah.

OK.

And this one is any... Well, as you can see, it's a constrictor.

It is indeed, yeah.

-That throttles its, uh...its prey.

-A-ha.

-Of whom I am not one.

-You hope.

-I hope.

Could I see where the head is right at the moment?

-Right beside you.

-All right, OK.

-It's just here.

-Hello, snakey.

Um... I think, compared with the other snakes,

am I right in saying that these are comparatively primitive?

They are indeed. These are probably one of the first constrictors.

Back in the prehistoric times they used their power to overcome their prey.

'Snakes are descended from lizard-like reptiles

'that lost their legs during the Early Cretaceous,

'some 90 million years ago.

'This giant python is one of the more ancient living snakes.'

This is probably the second largest python we have in Australia

and they could take anything, maybe even a full-grown wallaby.

And when they've eaten a full-grown wallaby,

how long is it before they have to eat again?

Well, it'd vary on temperatures and what kind of climates,

-cos the hotter it is the more... quicker they actually back down.

-Yes.

But, like all reptiles, they could go months and months and months

before they even need another feed after a big one like that.

Well, this is kind of relevant to our thoughts about survivors.

You could imagine a scenario at least where you've got something

-which would go without food for a long time and burrow.

-That's definitely a...

Which would be a pretty...secure environment for them to survive a crisis.

Absolutely.

And, um... Am I ever going to extract myself from this situation?

I'm not quite sure.

Well, some venomous snakes of course are almost ludicrously poisonous, aren't they?

There's only one poisonous snake in the entire world, and that's the sea snake.

The rest are venomous.

Oh, I beg your pardon. Yes, venomous. That's exactly right.

Of course, I should have remembered,

poison is ingested into the system, whereas venom is injected directly by fangs.

-Perhaps we should look at one of the other ones.

-Absolutely. Indeed.

-See where he's going already.

-There we go.

He could have you, not a problem.

-He could have me, not a problem.

-A-ha.

The ancestors of the python may well have survived

because they could swallow one big meal and wait.

But if you only eat once a year, you need to make sure your attack is effective.

'Constriction is one method to immobilise your prey

'and venom is another.'

Now, that's an impressive snake.

'Recent genetic studies suggest that this is a very ancient weapon

'and that the first venomous snakes evolved during the time of the dinosaurs.'

The most venomous snake in the world is the legendary taipan, and...

If I go like this a little bit...

Yeah. I'm not going to take any chances with this one, and...

-This is it.

-There's a legendary statistic about this particular snake.

It's so venomous that one bite would kill how many human beings?

About 300 men.

Which leads one to the question of why any snake has to be so venomous.

It would probably have a lot to do with what it eats.

Now, no-one is 100% sure but, I mean, when it comes to venom,

cos venom is just modified saliva.

It actually just works a lot better on warm-blooded animals,

whereas things like fish, amphibians, and even other reptiles,

they generally need a much higher dose, and that's actually what these guys feed on.

So it's a case of, it may seem extravagant,

but actually it's just right.

That's right. It's perfect for what this animal actually needs.

Good. Well, that's answered a question which has been bothering me for some time.

'Such potent venom is surely a guarantee of success,

'especially in hard times when you can't afford to miss a kill.

'Snakes could have survived the KT by hiding away and feeding only rarely.

'But how my next survivor made it through the extinction is more of a mystery.'

Quack, quack, quack! Come on.

How did the ancestors of today's birds survive the KT impact?

They couldn't just fly away from a ubiquitous catastrophe,

although having wings may have helped them reach a refuge.

Some aquatic birds might have survived out to sea,

or maybe some land lovers burrowed to escape the immediate effects of the catastrophe.

Feathers would have been useful insulation in the cold climate

that followed in the months, even years, after.

But then, many dinosaurs also had feathers and didn't survive.

So that can't be the explanation.

It seems most probable that birds could brave the hard times

because they survived on insects and small fish, other survivors.

And their flight buoyed them through from meal to meal and place to place.

But if the survival of their foodstuff

was one of the possible reasons why birds were saved from extinction,

if you're a bird that can't fly, you would have needed different strategies.

The emu is from a primitive family of birds called ratites,

that also includes ostriches, kiwi and cassowaries.

Emus have flightless feathers

and blade-like claws that closely resemble those of the three-toed theropod dinosaurs

from which they are ultimately descended.

They also have a reputation for aggression.

Females fight over males to breed.

Those prepared to get up close to an emu,

like our soundman, can only hope they are not mistaken for a rival.

Fortunately, James Biggs is a young man brave enough to be my guide.

-Well, I gather you... there's Mr and Mrs here.

-Yeah.

And Mrs has a, what should we say,

slightly more ferocious temperament than Mr, is that right?

Yeah, that's right.

So, as somebody who's looked after these creatures for a long time,

would you say they're, um... Would you describe them as intelligent?

Ha-ha-ha! No.

Instinctive, reactive, but definitely not intelligent.

Well, but they are survivors.

Emus might not be bright,

but they have a series of key survival traits.

They reach full size in only six months

and can live to be, well, perhaps 20 years old.

But the real secret of their success is that females don't put all their eggs in one basket.

They leave the males holding the babies.

-And the male incubates the eggs?

-He does. He incubates the eggs, he raises the chicks.

The female, apart from laying the egg, has nothing to do with the raising of the offspring.

Well, of course, I knew one or two human beings rather like that. But it's not the rule.

For ratites, I guess it seems to be.

Particularly in the breeding season, the male can go for weeks without food

whilst he's incubating the eggs.

-Well, actually, that is a survival technique, isn't it?

-Yes.

Let's face it, if times get hard, if you don't have to drink for weeks on end,

-you can travel a great distance in search of either food or water.

-Yeah.

By spreading her eggs around multiple males, and multiple nests,

the female emu increases the chance of at least some of her offspring surviving.

The turtle is a creature that does the opposite.

It puts all its eggs in one very big basket.

On average, only one out of every thousand of these baby turtles is likely to reach adulthood.

And yet, this very different strategy has long worked for the turtle.

After the KT impact, the seas became poisoned

by the fallout of toxic debris and ash.

Turtles had already been around for more than 150 million years.

Some had even evolved into four metre long giants.

But the KT extinction event would reduce their numbers

and their size.

'Doing her bit to maintain the turtles' long track record of survival is Jennie Gilbert,

'who runs a turtle rehabilitation centre.'

So, who have we got here?

Her name is Angie and she's actually a mature female olive ridley.

-And that's one of the rarer turtles?

-It is.

She is one of the rarer turtles.

I can see some tooth marks.

Yes, she got bitten on the top of the shell as you can see.

She actually was attacked by a very large saltwater crocodile.

And she also had part of her jaw hanging off.

So we had to take that piece of jaw off.

That proves that if a crocodile can snap at this poor animal

and the animal survives, it shows how tough she is.

Exactly right.

That shell must be incredibly tough for her to survive through that.

If you think of the size of a large saltwater crocodile, about 17 ft,

and he has come down with his jaws on top of her

and she's got out of it, she's a pretty tough girl.

To examine just how tough, I want to dig deep into the anatomy

of a recently deceased turtle found on a local beach.

Here's our turtle. How old do you think?

She's probably about 60-plus years.

-And it's a...green?

-Green, mature female.

This is called a plastron and it's a series of plates, as you can see.

-Extremely tough.

-Extremely tough.

But it's not as tough as the carapace which is on the top.

As you can feel, the carapace is very, very tough and bony.

'The turtle's shell is a very obvious survival trait,

'but, believe it or not, it was once possible to have half a turtle.'

There are fossil turtles going back to about 240 million years,

and I think the earlier ones got the plastron first.

-Yes, they did.

-Which implies to me that they were protecting

against something coming up and biting them from beneath.

The plastron was developed because they used to have predators

that used to come up underneath them in the water,

and on the top of them they just had

a backbone with a little bit of a shell, but not a complete covering.

-Well, shall we open her up and have a look inside?

-Yes.

The turtle's shell is a good adaptation for surviving predators,

but how did turtles survive through the KT?

-This has quite an impressive intestine.

-They have.

Wrapped round like a rather unappetising sausage.

Part of the answer lies with its lungs.

But to get to them I need a stomach almost as strong as the turtle's.

-Certainly a lot of bowel involved here.

-Yes.

And we've arrived at a position where we can see the lungs.

Yes, there's a very large surface area for these lungs.

The benefit of their lungs

is that these animals can stay submerged up to five hours,

but the benefit is they can take in air that can go through

into their lungs and out into their blood and out into the muscle.

So therefore that's why they can stay submerged for such a length of time.

So they really are diving champions.

Not only can turtles break records for staying submerged,

they can also win awards for surviving without food.

This one has been floating so long it even has barnacles.

This was brought in and actually has floater's disease.

As you can see, it's got air under the shell here,

and that's caused it to float on this side.

We've actually had animals brought in here that have been found

and they have probably been floating for about 12 months without eating.

Because once they float, they get this floater's disease

and they get air under their shell

and they can't dive down to actually feed.

So they've been floating.

Up to 12 months they can float and they can live on their fat stores.

So, like crocs and snakes,

the turtle is capable of not eating for a very long time.

This little turtle, has it got a name yet?

Well, Richard, it looks like a lovely turtle to me.

It looks like a pure gentleman, so therefore it should be Richard.

Well, I'm exceedingly flattered

to have an ancient living fossil named in my honour.

Thank you very much. I'm delighted.

After more than 200 million years of survival,

today, turtles are seriously endangered.

This time by man.

Humans are destroying turtle habitats

and spawning grounds in a way even the KT could not.

The turtle's armour can protect it from a hostile world.

But an even more effective strategy is to use a shell

to create a private and protected place.

Shells allowed ocean-dwelling invertebrates

to create their own microhabitats.

The earliest shelled molluscs

evolved more than 400 million years ago.

They survived the KT and continue to grow in abundance

here in Delaware Bay,

clinging to the rocks and ruins on the shoreline.

They may have survived the KT,

but they are easy pickings for certain two-legged mammals.

Actually rather good.

Another way to survive a crisis is...

..to clam up.

A lot of molluscs came through

because of their ability to seal themselves away from trouble.

Mmm!

Fairly yummy.

Probably the most delicious of these survivors, the oyster.

Which lives attached to rocks.

Securely fastened to rocks, often in the inter-tidal area.

Mmm! Yum!

I'm eating it washed down by another survivor,

beer from the oldest brewery in America.

Oysters suck in water, filter and consume its nutrients

and expel it again.

Since some oyster species can pass more than five litres

in a single hour, they would, in their own small way,

and over thousands of years,

contribute to the spring-cleaning of the seas after the crisis.

Living in well-stirred inter-tidal waters, oysters were protected

from the de-oxygenation event that poisoned so much marine life.

They still prosper today at the edges of the sea,

and they have provided man with an accessible foodstuff,

easily prised off rocks with primitive tools

since the early days of our species.

The nautilus is another shelled Cretaceous survivor.

It couldn't shut the world out completely,

but then, as a scavenger, it didn't want to.

The nautilus is a cephalopod, a relative of the squid

that can live to be 20 years old.

It uses a kind of jet propulsion to navigate itself through the depths.

The nautilus's big eyes are misleading.

In fact, it has poor vision and relies on its sense of smell

to forage for food and locate potential mates.

Perhaps smell would have been a handy survival trait

when the sun had been blotted out

and the oceans had been plunged into darkness.

But it probably wasn't this that saved it.

Once again, reproduction could have been the real key.

This is one of the first fossils I ever found.

Since their appearance about 400 million years ago, ammonites

evolved into thousands of different species of every shape and size.

And survived everything a hostile world could throw at them

for more than 300 million years.

Sadly, it was not these wonderful, rapidly evolving cephalopods

that made it through the KT, but...

..the more humble nautilus.

Some scientists even speculate that the ammonite spawned just once

at the end of their lives while our friend the nautilus, a superficially

similar creature, bred several times in a lifetime and made it through.

The nautilus lays comparatively few large eggs,

well supplied with nutrients, useful at a time of shortage.

The collapse of the aquatic food chain,

just like the collapse of the terrestrial food chain,

was a good time to be a scavenger or a bottom feeder.

Even dead species sinking into the depths provided

nourishment for perhaps the most famous living fossil of them all.

The coelacanth is glimpsed only rarely and spends

most of the time tucked out of the way in a safe corner of the ocean.

This is the only footage of it ever shot by the BBC.

Was it luck or its special adaptations that allowed

this living relic to pass through the KT?

It's tempting to look at its leisurely lifestyle,

large eggs and habitat as a kind of passport to survival.

But the answer may be that not only did it have

ample food to scavenge, it also made an unappetising meal itself.

Indeed, the coelacanth's oily innards reputedly make it

one of the most foul-tasting creatures ever to swim the seas.

Making yourself nasty-tasting and inedible was a tactic

that was also being employed back on the land.

One of the most successful plant survivors

of the last 360 million years, ferns.

Ferns are the first to colonise devastated landscapes.

They lack both flowers and seeds,

reproducing by spores carried on the underside of the leaves.

And they release them in their millions.

This is a male fern, a very elegant fern.

And here, look, on the back of the leaves,

are these little spore capsules

which ensure their wide distribution and they're toxic.

Few animals can eat them

and today there are an incredible 12,000 species.

The KT extinction event triggered what's called the fern spike,

the sudden and widespread appearance in the fossil record

of billions of spores derived from these ancient plants.

The aftermath of the asteroid impact had been a disaster for many.

But for others, it was the opportunity finally to shine.

For the dinosaurs, big had been beautiful,

and they had conquered almost every ecological niche available...

except one.

Burrowing underground were tiny mammals, like these shrews.

Small and delicate, with high metabolism,

short lifespans and vulnerable young,

they were, in many ways, the most unlikely survivors of all.

But when fiery disaster struck,

they were tucked away safe and sound.

Our oldest mammalian ancestors were rather inconspicuous little insect eaters,

something like shrews, and their distant descendants...

..this little chap.

A common hedgehog.

They were excellent at sniffing out food.

Maybe the ancient mammals could seek out their fellow survivors,

insects, from the safety of burrows,

while so many large animals above ground died in the mayhem of the KT.

If they could find enough food to sustain their warm-blooded metabolism,

they could endure through hard times.

Couldn't they?

The meek were to inherit the Earth.

After the dinosaurs died out,

there was an ecological vacuum which was quickly filled by the mammals.

The small mammals could come out of their underground burrows

or out of the leaf litter,

and soon they evolved into forms

that replaced the dinosaurs that had preceded them.

Giant herbivores, even carnivores, appeared in a short order.

But while new species were quickly evolving

to exploit the opportunities a changed world provided,

in one sheltered corner of the world,

some of the very oldest mammals had already claimed their place in the new world order.

It's a place they still occupy.

They're KT survivors that belong to a group of early mammals

even older than the marsupials,

and who still retain features inherited from their reptile ancestors.

They are called the monotremes.

Duckbilled, beaver-tailed, otter-footed, seal-bodied,

it's no wonder 18th-century naturalists thought the platypus to be a mythical chimera,

a creature stitched together by unscrupulous taxidermists that couldn't possibly be real.

But now, I'm off to find one.

So this is my third time in Warrawong,

and I haven't yet seen a platypus.

Oh, right! Hope today's the day.

So we must very careful in describing them as in any sense primitive,

because in a way, they're exquisitely adapted.

They are, definitely.

Over 100 million years these animals have been around, and they're great at hiding,

so that's one of the reasons you haven't seen 'em yet.

So... Yes, I'm sure!

The habitat here in the Warrawong nature sanctuary is much as it is in the wild,

which is ideal for the privacy-loving platypus.

So do you have, what? Two or three, half a dozen here?

I'd like to think we have about ten.

We should be quiet now, because you never know,

this might be the time to actually see the platypus.

(I can see some ripples down there.)

(Perhaps we should move along a bit.)

'The platypus loves this sort of habitat,

'but as the hours tick by, it becomes increasingly clear

'we're about as welcome as paparazzi on a private beach.'

It's very discreet, you have to say.

Well, I mean, it would be great if we could see one.

Could that be one?

Every time I think I've seen one, another bird hops into view.

-They're not frightened of the lights.

-No, not at all.

Our platypuses have been conditioned to have light on them,

and they're not too fussed.

Then, finally, after 18 years and nearly five hours,

I see the platypus.

(There we go!)

There it is again.

They lay their eggs in burrows, don't they?

-They do, yeah.

-So how many in this pond?

I think there's about three burrows in this pond, and they're very extensive burrows.

So when the female lays her eggs,

she lays up to two or three eggs in the burrow,

and they could be in the burrow for four to five months, developing.

They take about 12 days to hatch,

and she incubates the eggs.

Gosh, that's a clear view.

That's as good as you ever get.

'As well as being an egg layer, the platypus also retained something

'of the cold-bloodedness of its reptilian ancestors,

'having an average body temperature five degrees centigrade colder than placental mammals.'

I gather the platypus can be, if you don't handle it right,

quite a dangerous animal.

They can, definitely.

Platypus have a venomous spear on their back ankles,

and that's just for the males.

They use that venomous spear against their natural enemy, which are water rats,

and also against each other during the mating season.

-I believe the venom is bad enough to kill a small dog?

-It is.

It caused excruciating pain to the European settlers when they first came,

and picked these innocent-looking creatures up and got a nasty shock.

So yet another Australian creature that causes you pain

-if you don't do it right.

-That's right, we've got lots of them in Australia!

I came here first 18 years ago.

I don't need to hunt the platypus now,

I've seen one of the great survivors.

The platypus might not be an obvious survivor,

but its ancestors, swimming, burrowing creatures that rely on smell and survive on insects,

were adapted to the kinds of conditions the KT crisis caused.

Evidence suggests the platypus's earliest ancestors may have been around even longer

than the oldest placental and marsupial mammals.

The platypus's closest living relative is my final KT survivor.

'It's an extraordinary creature called an echidna.'

That way, I'd say, wouldn't you?

'And it possesses a quality that would become key to mammals inheriting the Earth.'

Now, where I could hear her earlier was down through there.

The signal's not any stronger, because you see the little hill...

'My guide is Dr Peggy Rismiller,

'a woman who has spent much of her life protecting echidnas and their habitat.'

She could be... A-ha.

'Echidnas bear a close physical resemblance to giant hedgehogs,

'but they're not closely related.'

So yeah, they're very good at hiding.

I think she's burrowed at the back of the tree here.

There she goes.

This is Big Mama. I've known her for 23 years.

So it's a waiting game. I just wait for her to relax.

She has the advantage of being extremely strong.

And you always go with the spines, so in this direction,

I'm going with the spines, and see, I'm actually...

-Do you want that closer?

-That's OK. Just a second, I'll get her out.

OK.

It's like digging up great spiny wheat.

There, you see her face?

That's her little nose sticking out there.

You're very lucky to see her face.

Very often the first thing they do is hide that beak

because it's the most vulnerable part of the body.

-How old?

-I think probably about 45.

45 years?

That's a human lifetime!

There you go. Have you held an echidna?

I'm about to.

OK.

She's five kilos, remember. You got her?

I've got her.

There she is.

She's tucked her face well inside,

so the sensitive nose, or beak, I suppose, is protected.

But you can see the long claws on either side,

which make such an effective digging instrument,

and make them so good at hiding, too.

Echidnas are the only mammal who can dig straight down into the ground,

because the front feet go in one direction, the hind feet go

in the other direction, so they can go straight down and make a hole like she just came out of.

She's sort of bunching up her spines

to give her maximum pincushion effect.

THEY CHUCKLE

'Like other early mammals, the echidna eats insects

'and other small creatures.

'So the survival of these tiny animals helped

'ensure its survival, in turn.

'The echidna has been using its sensitive beak

'to ferret out tiny prey for millions of years.'

Now this little delicate structure is what?

The lower jaw.

A pair of struts, really, no more than that.

Or something like a tuning rod,

because when the echidna is foraging, it will put its beak on the ground,

and they're very sensitive to vibrations, so these tuning rods

can help it actually sense any vibration in the soil,

which means finding their food source.

Why do you think echidnas are great survivors?

I think the first thing to look at is food source.

If you're going to be a survivor, what do you eat?

Invertebrates.

So being an invertebrate eater makes them a good survivor.

We know invertebrates carried through the crisis at the end of the Cretaceous, yes.

And what's going to be around longer than anything else? Invertebrates.

Secondly, echidnas have a low operative body temperature,

which gives them an advantage.

They also regulate their body temperature, in that when they go to sleep,

they just let the body temperature go down, which means they save a lot of energy.

There she is again. Look at that face!

'Two vital traits shared by a number of our survivors.

'An unfussy diet, and a slow metabolism.'

They are also capable of hunkering down,

of digging down and hiding from trouble.

It's not only that, they're good at surviving natural things like fire,

so because of their digging capabilities

and being able to lower their body temperature and their metabolism

during a fire situation which happens in Australia naturally,

these guys are going to survive.

Hiding away - another common survival technique.

But unlike our reptile survivors,

that produce many, well-developed offspring,

the echidna lays a single egg, which hatches in her pouch

and grows into an underdeveloped and hairless baby, called a puggle.

The reproduction is quite slow. They're eight years old before they're sexually mature,

they may only have one young every three years.

And the puggle gets its own additional security,

a nursery burrow.

The amazing thing about the echidna,

very different again from any other mammal -

once the puggle is in the burrow, its life changes dramatically.

When it was in the pouch, it could suckle at any time,

-because they do suckle milk.

-Yes.

Once it's in the burrow,

mom only comes back for two hours every five days.

And the other advantage is they have a low temperature,

the burrow is quite cool,

so the young echidna is growing at a slow rate.

But she will continue for seven months.

So this is really rather slow child-rearing, isn't it?

Particularly for an animal of that size.

Investing so much time and energy into one or a few offspring

is a distinctly mammalian reproduction strategy.

And nurture may have been key to evolving perhaps what we regard

as the greatest survival trait of them all.

Intelligence.

One thing that strikes me, I think I'm right -

-it seems to have a rather large brain.

-Good observation.

Actually, the brain is huge for the size of the animal.

And I think the most important part is the neocortex.

Have you ever heard of the neocortex?

Explain what it does.

Well, the neocortex is the frontal part of the brain,

where your memory, your reasoning, your personality comes from.

And echidnas have great personalities.

But I think the best reason I heard for the neocortex

was from a ten-year-old student, who said,

"You said they were around with the dinosaurs, so they have a lot to remember."

-That's rather a good answer!

-Absolutely!

Big brains would prove to be key in the evolution

and success of mammals.

Today, mammals have occupied every ecological niche

once inhabited by dinosaurs.

Yet it still seems extraordinary that small insectivores

could produce giant predators and potbellied grazers.

It seems nature abhors a vacuum,

and every vacant ecological niche is an opportunity waiting to be filled.

'But few prehistoric bookies would have put money on mammals

'winning the lottery of life.

'Which, I suppose, just goes to show...'

Sometimes, to be a survivor,

it does no harm to have luck on your side.

-# The winner takes it all

-Takes it all

-# The loser has to fall

-Has to fall

-# It's simple and it's plain

-Yes, it's plain

# The winner takes it all... #

In the next episode, I go in search of survivors from the Ice Age.

Subtitles by Red Bee Media Ltd