0:00:05 > 0:00:10Since the emergence of life, more than 3 billion years ago,
0:00:10 > 0:00:16life on our planet has suffered a series of devastating mass extinction events.
0:00:16 > 0:00:20These have killed off uncountable species,
0:00:20 > 0:00:24and even threatened to end life on Earth altogether.
0:00:26 > 0:00:31I'm Professor Richard Fortey, of London's Natural History Museum.
0:00:31 > 0:00:36I've spent all my working life studying the remains of animals long extinct.
0:00:38 > 0:00:41'But now, I'm leaving the vaults
0:00:41 > 0:00:45'to discover why some animals and plants have survived.'
0:00:45 > 0:00:46Hello, snakey.
0:00:46 > 0:00:49'I'm going in search of living fossils,
0:00:49 > 0:00:50'old-timers...'
0:00:50 > 0:00:53This little face.
0:00:53 > 0:00:56'..that somehow managed to survive when so many others perished.'
0:00:59 > 0:01:01Rubbery hardly does it justice.
0:01:03 > 0:01:07'In the process, I hope to find an answer to a profound question.'
0:01:09 > 0:01:13Is being a survivor a question of having some very special features?
0:01:14 > 0:01:17Or nothing more than pure chance?
0:01:19 > 0:01:24'From living fossils that are our most ancient relatives...
0:01:25 > 0:01:30'..to gigantic relics from the age of the dinosaurs.'
0:01:30 > 0:01:36Life as we see it today is not just the product of evolution,
0:01:36 > 0:01:39it's also a consequence of mass extinction.
0:01:39 > 0:01:42We are all the sons and daughters of catastrophe.
0:01:44 > 0:01:46Oh, my goodness!
0:02:00 > 0:02:04More than 100 million years ago, the Cretaceous Age already had
0:02:04 > 0:02:08highly sophisticated and complex ecosystems.
0:02:10 > 0:02:14There were flowers, and plants that we might recognise.
0:02:14 > 0:02:17There were insects, birds and even tiny mammals,
0:02:17 > 0:02:21though not yet butterflies or bees.
0:02:21 > 0:02:24And there were amphibians and reptiles,
0:02:24 > 0:02:28especially very big reptiles, like dinosaurs.
0:02:32 > 0:02:36Then, one day, 65 million years ago,
0:02:36 > 0:02:39this world came to a sudden end
0:02:39 > 0:02:42when a 10km-diameter asteroid collided with the Earth.
0:02:50 > 0:02:54The impact is believed to have struck the Earth
0:02:54 > 0:02:58with the force of 96 teratonnes of TNT,
0:02:58 > 0:03:00causing colossal shockwaves,
0:03:00 > 0:03:03tsunamis perhaps hundreds of metres high
0:03:03 > 0:03:08and so much hot ash and debris, the global atmosphere became superheated,
0:03:08 > 0:03:11igniting wildfires all over the world.
0:03:13 > 0:03:16It was the end of the long reign of the dinosaurs.
0:03:20 > 0:03:24I used to walk with dinosaurs or, more accurately,
0:03:24 > 0:03:27pass them every working day on the way to my office
0:03:27 > 0:03:29in London's Natural History Museum.
0:03:29 > 0:03:33But what I want to know is, what were the lucky breaks
0:03:33 > 0:03:37and evolutionary adaptations that allowed some species
0:03:37 > 0:03:41to survive the disastrous end of the Cretaceous Age
0:03:41 > 0:03:43when these marvellous giants did not?
0:03:49 > 0:03:53Locating the scattered survivors of the KT extinction
0:03:53 > 0:03:56is not as straightforward as you might imagine.
0:03:56 > 0:03:59'You never know quite where they'll turn up.'
0:03:59 > 0:04:01OK, 42nd Street.
0:04:05 > 0:04:09'The survivor I am looking for not only outlived the dinosaurs,
0:04:09 > 0:04:13'but apparently several of them even survived the dropping of the atom bomb on Hiroshima
0:04:13 > 0:04:16'at the end of World War II.'
0:04:21 > 0:04:24Well, this is a jungle of sorts,
0:04:24 > 0:04:26an urban jungle.
0:04:26 > 0:04:30We are right in the middle of Manhattan,
0:04:30 > 0:04:35but even here, lurking in some corner, there might yet be a survivor.
0:04:37 > 0:04:40There's hardly any space here for anything green.
0:04:40 > 0:04:43In fact, hardly any space for anything living,
0:04:43 > 0:04:45except lots and lots of human beings.
0:04:50 > 0:04:54Strangely enough, there's one over there.
0:05:01 > 0:05:06If something can survive the pollution and the heat
0:05:06 > 0:05:11of a summer in New York, not to mention miscellaneous garbage,
0:05:11 > 0:05:14then that is a pretty tough organism.
0:05:14 > 0:05:17And that's exactly where we find the gingko.
0:05:22 > 0:05:27Ginkgo leaves are fan-shaped or triangular, really beautiful leaves,
0:05:27 > 0:05:31combining a perfect design and a certain toughness,
0:05:31 > 0:05:34which may of course have helped them through these crises.
0:05:38 > 0:05:40Gingko trees can now be found
0:05:40 > 0:05:42all over the world.
0:05:42 > 0:05:44But until two centuries ago,
0:05:44 > 0:05:48they could only be found in one isolated region of China.
0:05:48 > 0:05:53Sometimes living for more than a thousand years, they're extremely tough.
0:05:56 > 0:06:02The gingko tree is an example of perhaps the simplest survival strategy of all.
0:06:02 > 0:06:04If you're tough enough to cling on somewhere,
0:06:04 > 0:06:07even a tiny area in one part of the globe,
0:06:07 > 0:06:12a chance may yet come to recolonise the world.
0:06:20 > 0:06:23The KT event was so destructive,
0:06:23 > 0:06:25it reduced even this tough species
0:06:25 > 0:06:30to a tiny rump population clinging on in one remote location.
0:06:30 > 0:06:32So, it may not be surprising
0:06:32 > 0:06:36that nearly half of all animal and plant species
0:06:36 > 0:06:38perished in the destruction.
0:06:40 > 0:06:42What is perhaps far more surprising is that
0:06:42 > 0:06:46relatives of the dinosaurs managed to survive.
0:06:49 > 0:06:51In Queensland, Australia,
0:06:51 > 0:06:54I prepare to meet one of the largest animal survivors
0:06:54 > 0:06:57of the KT extinction event.
0:06:57 > 0:06:59Guys, look, what I'm going to do this afternoon is
0:06:59 > 0:07:05I'm going to dispel the difference between fact and fiction about these animals.
0:07:05 > 0:07:07Now, what most people see...
0:07:07 > 0:07:11Crocodiles are found in tropical climates all over the world.
0:07:13 > 0:07:15The croc is a formidable predator
0:07:15 > 0:07:19that's responsible for the deaths of 2,000 people annually...
0:07:20 > 0:07:25..a fact that handler Clay Mitchell is acutely aware of.
0:07:25 > 0:07:29A male saltwater crocodile can grow to be seven metres long
0:07:29 > 0:07:31and weigh up to 1,000 kilos.
0:07:33 > 0:07:38It's a survivor for whom surprise and ferocity are key weapons.
0:07:50 > 0:07:53Its jaw can snap shut at lightning speed
0:07:53 > 0:07:58and its mouth is filled with 66 hollow teeth.
0:07:58 > 0:08:03These are constantly being renewed by fresh replacements growing inside them.
0:08:03 > 0:08:09A single crocodile can get through an incredible 2,000 teeth in its lifetime.
0:08:09 > 0:08:16And since the oldest crocodile in captivity survived until it was 140 years old,
0:08:16 > 0:08:19well, you can see why it's got such a lot to smile about.
0:08:19 > 0:08:20Go on.
0:08:23 > 0:08:26We might let him get his breath back, eh?
0:08:26 > 0:08:28LAUGHTER
0:08:28 > 0:08:31It's not easy to teach a crocodile new tricks.
0:08:31 > 0:08:34But then, it doesn't need them.
0:08:34 > 0:08:37Crocodiles have remained unchanged since the Jurassic Age,
0:08:37 > 0:08:41the golden age of the dinosaurs that began nearly 200 million years ago.
0:08:45 > 0:08:49They are cold-blooded, highly efficient killing machines
0:08:49 > 0:08:52and, above all, they can wait.
0:08:54 > 0:08:57If pushed, it's not fussy about what it eats.
0:08:57 > 0:09:01I mean, I know it'd eat us if it's feeling a little bit peckish.
0:09:01 > 0:09:05So, it could survive on anything from the small to the humongous.
0:09:07 > 0:09:12It's a tremendous advantage to be able to feed only occasionally and then well,
0:09:12 > 0:09:15and when you get something not to let it go. Cos...
0:09:15 > 0:09:20if you can go without food for six or seven months, you can weather a crisis.
0:09:23 > 0:09:25A born survivor, this one.
0:09:30 > 0:09:33Being able to eat almost anything,
0:09:33 > 0:09:36it's a good way to stay alive in lean times.
0:09:36 > 0:09:40But to get through utter devastation you need something more.
0:09:42 > 0:09:45The question we really want to know is,
0:09:45 > 0:09:50why did this particular kind of animal come through the big crisis
0:09:50 > 0:09:52at the end of the Cretaceous
0:09:52 > 0:09:55and dinosaurs, their contemporaries,
0:09:55 > 0:09:59in some ways more superbly adapted, you might say, didn't make it?
0:09:59 > 0:10:04I think probably one would be its ability to utilise food
0:10:04 > 0:10:07a lot more efficiently than us.
0:10:07 > 0:10:09These guys have got a very slow metabolism,
0:10:09 > 0:10:12so a little bit of food goes a very, very long way.
0:10:12 > 0:10:14So I could probably definitely say he could survive
0:10:14 > 0:10:17for eight or ten months without eating absolutely anything.
0:10:17 > 0:10:21And probably versatility might have been a factor too.
0:10:21 > 0:10:26They've got this famous structure, the nictitating membrane, isn't that right?
0:10:26 > 0:10:29- That's correct.- It sounds vaguely obscene, doesn't it?- Ha-ha, it does.
0:10:29 > 0:10:31Perhaps you could explain what that is.
0:10:31 > 0:10:33It's very simple. Look, they have three eyelids.
0:10:33 > 0:10:36So what they do is they have a top one and a bottom one,
0:10:36 > 0:10:41and the nictitating membrane is one that actually moves on the inside of those two eyelids
0:10:41 > 0:10:44from the front of the eye to the back of it.
0:10:44 > 0:10:46When they go under the water and do these sorts of things,
0:10:46 > 0:10:48that nictitating membrane does move across the eye.
0:10:48 > 0:10:52So, the minimum exposure position is basically just to have that nasal disc
0:10:52 > 0:10:55with the two nostrils above the water
0:10:55 > 0:10:58- and you can see how the eyes project at about the same height.- Yeah.
0:10:58 > 0:11:02So, all they need is to be able to see and to be able to breathe,
0:11:02 > 0:11:06and the rest of the body can remain completely concealed below the water.
0:11:09 > 0:11:13One of the reasons crocodiles survived and dinosaurs didn't
0:11:13 > 0:11:20may be because the same skills that made it such a master of ambush by hiding underwater
0:11:20 > 0:11:25also saved it from the fiery devastation that swept across the world.
0:11:28 > 0:11:33Of course, just to point out one thing, which you said it was half tail.
0:11:33 > 0:11:37That half tail contains some meat, and the meat is presumably quite edible.
0:11:37 > 0:11:40- Definitely.- So, perhaps we should go and try it.
0:11:40 > 0:11:44Yes. Well, I'd say, I think our chef does a pretty good job with it.
0:11:44 > 0:11:46I think it's actually a meat with a little bit of bite.
0:11:46 > 0:11:47THEY LAUGH
0:11:53 > 0:11:57'I have to admit that I'm curious to try eating crocodile.
0:11:57 > 0:12:00'After all, it's almost like eating dinosaur.'
0:12:00 > 0:12:05- You might as well try one of those, mate.- All right, let's see. It's a... ha-ha...
0:12:06 > 0:12:07Cheers, mate.
0:12:10 > 0:12:12Mmm...
0:12:12 > 0:12:13Mmm...
0:12:18 > 0:12:20It's pretty good.
0:12:20 > 0:12:23Meaty, succulent.
0:12:24 > 0:12:27It's sort of, um... more pig than fish.
0:12:27 > 0:12:31In fact, you might call it Jurassic pork.
0:12:31 > 0:12:34He-he-he! Certainly.
0:12:34 > 0:12:37All it takes is usually some celebrity chef to get on
0:12:37 > 0:12:39and actually do a little bit of a dish to actually encourage
0:12:39 > 0:12:44people just over that fence to go out there and actually try it for themselves.
0:12:44 > 0:12:49The more people that try it, I think, the more popular it will actually become.
0:12:57 > 0:12:5965 million years ago,
0:12:59 > 0:13:04it wasn't just dinosaurs that got exterminated by the impact.
0:13:04 > 0:13:10Perhaps as many as half of all plant species were also blasted, never to return.
0:13:12 > 0:13:15Some of the same survival strategies the apply to animals like the crocodile
0:13:15 > 0:13:19were also appropriate for the plant world.
0:13:19 > 0:13:25Plants that survived the KT also needed ways to hide out and bide their time.
0:13:27 > 0:13:31One way to survive a disaster is to go NUTS!
0:13:33 > 0:13:40These podocarp seeds are extremely tough, durable time capsules
0:13:40 > 0:13:47that can fall to the ground and germinate after the KT events had passed over them.
0:13:51 > 0:13:56The shell on a nut is a good way to protect a seed from fire,
0:13:56 > 0:14:01but some ancient species have even adapted to endure periodic fires
0:14:01 > 0:14:04as part of their life cycle.
0:14:07 > 0:14:09Such species include many cycads.
0:14:11 > 0:14:17Which is why I'm going to meet cycad expert and enthusiast Gary Wilson.
0:14:18 > 0:14:23'Gary leads me down to the forest trail on a cycad safari.'
0:14:24 > 0:14:27Well, that's quite a tree.
0:14:27 > 0:14:30And I suppose it might be quite old.
0:14:30 > 0:14:31Yes, certainly.
0:14:31 > 0:14:36This one I would suggest, and it's a little difficult to age them, 400 or 500 years, perhaps.
0:14:36 > 0:14:40To an untutored eye, it might look a bit like a palm tree,
0:14:40 > 0:14:42but it's not related to a palm, is it?
0:14:42 > 0:14:45This is one of three types of cycads that is found here
0:14:45 > 0:14:49in this Wet Tropics Region in Daintree, in North Queensland.
0:14:49 > 0:14:52In that way it's a living laboratory
0:14:52 > 0:14:56for these evolutionary survivors across time barriers and extinction events.
0:14:56 > 0:14:58This is a green dinosaur.
0:14:58 > 0:15:01This predated the dinosaurs and has survived them.
0:15:01 > 0:15:04I think they've even found masticated remains of these things...
0:15:04 > 0:15:08- That's correct.- ..in dinosaur coprolites or dinosaur poo, fossilised.
0:15:08 > 0:15:13And found cycad fragments inside, so this was part of dinosaur diet.
0:15:13 > 0:15:17- They went, but their food plant survived.- Survived.
0:15:17 > 0:15:20And that's an interesting question.
0:15:20 > 0:15:22Any theories particularly why?
0:15:22 > 0:15:28The strategy that ensured the success of the cycads as a group of plants is this,
0:15:28 > 0:15:30it's a time machine, it's a seed.
0:15:30 > 0:15:33It contains a nutrient reservoir.
0:15:33 > 0:15:36It contains an embryo, it can travel through time,
0:15:36 > 0:15:39through seasonality, through extreme events.
0:15:41 > 0:15:46Cycad seeds from some species even need fire to reproduce.
0:15:48 > 0:15:51With rainfall, nutrients in the ash trigger germination.
0:15:52 > 0:15:57'To ensure its survival, the cycad fruit has evolved an additional strategy -
0:15:57 > 0:15:58'poison.'
0:16:00 > 0:16:06It contains a suite of novel compounds that make it unattractive to things eating it, for instance,
0:16:06 > 0:16:08or that would be eating it.
0:16:08 > 0:16:11Cycads are the only plants on the planet
0:16:11 > 0:16:14that incorporate mercury in their tissue.
0:16:14 > 0:16:18- That's very nasty indeed, isn't it? - Very nasty.
0:16:18 > 0:16:24'More delicate plant survivors needed subtler tactics to survive the KT crisis.'
0:16:26 > 0:16:31In my own garden is a survivor that only made it because of a helping hand.
0:16:31 > 0:16:34Or should I say proboscis?
0:16:37 > 0:16:40Magnolia blossom announces itself from afar
0:16:40 > 0:16:45like a small flock of pale, untidy birds that have become entangled in the branches.
0:16:48 > 0:16:50When this first evolved,
0:16:50 > 0:16:54this plant was pollinated not by the bees and butterflies
0:16:54 > 0:16:58that we are so used to today, but by beetles and other insects.
0:17:01 > 0:17:05'The first magnolias appeared around 100 million years ago.
0:17:05 > 0:17:11'And a few days each year, it's still visited by its ancient pollinators.'
0:17:11 > 0:17:14Got it! Look, look, look, look, look! There they are.
0:17:14 > 0:17:17There's our little beetles.
0:17:17 > 0:17:19Isn't that nice?
0:17:19 > 0:17:20There's one going up the petal.
0:17:24 > 0:17:27Without these tiny insects, flowering plants could not have survived.
0:17:27 > 0:17:31Indeed, the survival of insects and other small invertebrates
0:17:31 > 0:17:35was crucial to the survival of many other species.
0:17:37 > 0:17:43Even so, the early flowers and their pollinators both only just scraped through.
0:17:45 > 0:17:50Why did it survive? Well, it was pollinated by beetles and other insects.
0:17:50 > 0:17:55Those insects carried through too and survived that big extinction event.
0:17:55 > 0:18:00But also it had seeds. And the seeds could survive in the soil.
0:18:00 > 0:18:06They didn't need to germinate every year. Perhaps they could outlive the hard times.
0:18:06 > 0:18:10And I don't think its antiquity has diminished its beauty one iota.
0:18:19 > 0:18:24Even those few plants that made it were ravaged and stressed.
0:18:26 > 0:18:30As plant species after plant species withered and died,
0:18:30 > 0:18:34so too the giant herbivorous dinosaurs also vanished.
0:18:36 > 0:18:40And, in turn, the carnivorous dinosaurs that preyed on them.
0:18:42 > 0:18:47To survive, many animals also needed to behave a little like seeds,
0:18:47 > 0:18:51going underground and quietly enduring.
0:18:51 > 0:18:56A strategy like this may well have saved the snakes.
0:18:58 > 0:19:01'Snake handler Shane Neal has agreed to show me
0:19:01 > 0:19:05'a few of the snake family's more illustrious members.'
0:19:05 > 0:19:08- Hello, Shane.- Hello, mate.- Nice to see you.- Nice to see you too.
0:19:08 > 0:19:12- I gather you've brought me a load of different snakes.- I have, indeed.
0:19:12 > 0:19:14- Can we have a look?- Absolutely.
0:19:17 > 0:19:20- Ah! Now, that's an impressive snake. - It is indeed.
0:19:20 > 0:19:24- What do we have here? - This is an olive python.
0:19:24 > 0:19:25Would you like to hold it?
0:19:25 > 0:19:29- Ah... Is this the one that likes to be held?- It is one.- Oh, all right.
0:19:29 > 0:19:31- Do you trust me? - Sure, I trust you. Yeah.
0:19:31 > 0:19:33OK.
0:19:36 > 0:19:40And this one is any... Well, as you can see, it's a constrictor.
0:19:40 > 0:19:42It is indeed, yeah.
0:19:42 > 0:19:46- That throttles its, uh...its prey. - A-ha.
0:19:46 > 0:19:50- Of whom I am not one.- You hope. - I hope.
0:19:50 > 0:19:54Could I see where the head is right at the moment?
0:19:54 > 0:19:57- Right beside you.- All right, OK. - It's just here.- Hello, snakey.
0:19:57 > 0:20:00Um... I think, compared with the other snakes,
0:20:00 > 0:20:05am I right in saying that these are comparatively primitive?
0:20:05 > 0:20:08They are indeed. These are probably one of the first constrictors.
0:20:08 > 0:20:13Back in the prehistoric times they used their power to overcome their prey.
0:20:14 > 0:20:17'Snakes are descended from lizard-like reptiles
0:20:17 > 0:20:19'that lost their legs during the Early Cretaceous,
0:20:19 > 0:20:21'some 90 million years ago.
0:20:21 > 0:20:26'This giant python is one of the more ancient living snakes.'
0:20:26 > 0:20:29This is probably the second largest python we have in Australia
0:20:29 > 0:20:33and they could take anything, maybe even a full-grown wallaby.
0:20:33 > 0:20:36And when they've eaten a full-grown wallaby,
0:20:36 > 0:20:38how long is it before they have to eat again?
0:20:38 > 0:20:41Well, it'd vary on temperatures and what kind of climates,
0:20:41 > 0:20:44- cos the hotter it is the more... quicker they actually back down. - Yes.
0:20:44 > 0:20:47But, like all reptiles, they could go months and months and months
0:20:47 > 0:20:50before they even need another feed after a big one like that.
0:20:50 > 0:20:54Well, this is kind of relevant to our thoughts about survivors.
0:20:54 > 0:20:57You could imagine a scenario at least where you've got something
0:20:57 > 0:21:01- which would go without food for a long time and burrow. - That's definitely a...
0:21:01 > 0:21:06Which would be a pretty...secure environment for them to survive a crisis.
0:21:06 > 0:21:08Absolutely.
0:21:08 > 0:21:13And, um... Am I ever going to extract myself from this situation?
0:21:13 > 0:21:15I'm not quite sure.
0:21:15 > 0:21:20Well, some venomous snakes of course are almost ludicrously poisonous, aren't they?
0:21:20 > 0:21:23There's only one poisonous snake in the entire world, and that's the sea snake.
0:21:23 > 0:21:25The rest are venomous.
0:21:25 > 0:21:28Oh, I beg your pardon. Yes, venomous. That's exactly right.
0:21:28 > 0:21:30Of course, I should have remembered,
0:21:30 > 0:21:35poison is ingested into the system, whereas venom is injected directly by fangs.
0:21:35 > 0:21:40- Perhaps we should look at one of the other ones.- Absolutely. Indeed.
0:21:40 > 0:21:45- See where he's going already.- There we go.
0:21:45 > 0:21:47He could have you, not a problem.
0:21:47 > 0:21:50- He could have me, not a problem. - A-ha.
0:21:50 > 0:21:55The ancestors of the python may well have survived
0:21:55 > 0:22:00because they could swallow one big meal and wait.
0:22:00 > 0:22:05But if you only eat once a year, you need to make sure your attack is effective.
0:22:05 > 0:22:08'Constriction is one method to immobilise your prey
0:22:08 > 0:22:11'and venom is another.'
0:22:11 > 0:22:12Now, that's an impressive snake.
0:22:12 > 0:22:17'Recent genetic studies suggest that this is a very ancient weapon
0:22:17 > 0:22:21'and that the first venomous snakes evolved during the time of the dinosaurs.'
0:22:21 > 0:22:27The most venomous snake in the world is the legendary taipan, and...
0:22:27 > 0:22:30If I go like this a little bit...
0:22:30 > 0:22:35Yeah. I'm not going to take any chances with this one, and...
0:22:39 > 0:22:45- This is it. - There's a legendary statistic about this particular snake.
0:22:45 > 0:22:50It's so venomous that one bite would kill how many human beings?
0:22:50 > 0:22:52About 300 men.
0:22:52 > 0:22:58Which leads one to the question of why any snake has to be so venomous.
0:22:58 > 0:23:00It would probably have a lot to do with what it eats.
0:23:00 > 0:23:05Now, no-one is 100% sure but, I mean, when it comes to venom,
0:23:05 > 0:23:06cos venom is just modified saliva.
0:23:06 > 0:23:09It actually just works a lot better on warm-blooded animals,
0:23:09 > 0:23:13whereas things like fish, amphibians, and even other reptiles,
0:23:13 > 0:23:17they generally need a much higher dose, and that's actually what these guys feed on.
0:23:17 > 0:23:21So it's a case of, it may seem extravagant,
0:23:21 > 0:23:24but actually it's just right.
0:23:24 > 0:23:27That's right. It's perfect for what this animal actually needs.
0:23:27 > 0:23:33Good. Well, that's answered a question which has been bothering me for some time.
0:23:33 > 0:23:37'Such potent venom is surely a guarantee of success,
0:23:37 > 0:23:40'especially in hard times when you can't afford to miss a kill.
0:23:40 > 0:23:45'Snakes could have survived the KT by hiding away and feeding only rarely.
0:23:45 > 0:23:52'But how my next survivor made it through the extinction is more of a mystery.'
0:23:53 > 0:23:55Quack, quack, quack! Come on.
0:23:55 > 0:24:01How did the ancestors of today's birds survive the KT impact?
0:24:01 > 0:24:04They couldn't just fly away from a ubiquitous catastrophe,
0:24:04 > 0:24:08although having wings may have helped them reach a refuge.
0:24:08 > 0:24:11Some aquatic birds might have survived out to sea,
0:24:11 > 0:24:17or maybe some land lovers burrowed to escape the immediate effects of the catastrophe.
0:24:18 > 0:24:21Feathers would have been useful insulation in the cold climate
0:24:21 > 0:24:25that followed in the months, even years, after.
0:24:25 > 0:24:29But then, many dinosaurs also had feathers and didn't survive.
0:24:29 > 0:24:31So that can't be the explanation.
0:24:34 > 0:24:37It seems most probable that birds could brave the hard times
0:24:37 > 0:24:42because they survived on insects and small fish, other survivors.
0:24:42 > 0:24:46And their flight buoyed them through from meal to meal and place to place.
0:24:58 > 0:25:00But if the survival of their foodstuff
0:25:00 > 0:25:04was one of the possible reasons why birds were saved from extinction,
0:25:04 > 0:25:09if you're a bird that can't fly, you would have needed different strategies.
0:25:11 > 0:25:16The emu is from a primitive family of birds called ratites,
0:25:16 > 0:25:18that also includes ostriches, kiwi and cassowaries.
0:25:27 > 0:25:30Emus have flightless feathers
0:25:30 > 0:25:35and blade-like claws that closely resemble those of the three-toed theropod dinosaurs
0:25:35 > 0:25:38from which they are ultimately descended.
0:25:38 > 0:25:41They also have a reputation for aggression.
0:25:43 > 0:25:45Females fight over males to breed.
0:25:47 > 0:25:50Those prepared to get up close to an emu,
0:25:50 > 0:25:54like our soundman, can only hope they are not mistaken for a rival.
0:26:08 > 0:26:12Fortunately, James Biggs is a young man brave enough to be my guide.
0:26:21 > 0:26:25- Well, I gather you... there's Mr and Mrs here.- Yeah.
0:26:25 > 0:26:28And Mrs has a, what should we say,
0:26:28 > 0:26:31slightly more ferocious temperament than Mr, is that right?
0:26:31 > 0:26:33Yeah, that's right.
0:26:33 > 0:26:37So, as somebody who's looked after these creatures for a long time,
0:26:37 > 0:26:41would you say they're, um... Would you describe them as intelligent?
0:26:41 > 0:26:43Ha-ha-ha! No.
0:26:43 > 0:26:48Instinctive, reactive, but definitely not intelligent.
0:26:48 > 0:26:52Well, but they are survivors.
0:26:52 > 0:26:54Emus might not be bright,
0:26:54 > 0:26:57but they have a series of key survival traits.
0:26:57 > 0:27:00They reach full size in only six months
0:27:00 > 0:27:04and can live to be, well, perhaps 20 years old.
0:27:04 > 0:27:10But the real secret of their success is that females don't put all their eggs in one basket.
0:27:10 > 0:27:14They leave the males holding the babies.
0:27:14 > 0:27:19- And the male incubates the eggs? - He does. He incubates the eggs, he raises the chicks.
0:27:19 > 0:27:26The female, apart from laying the egg, has nothing to do with the raising of the offspring.
0:27:26 > 0:27:30Well, of course, I knew one or two human beings rather like that. But it's not the rule.
0:27:30 > 0:27:33For ratites, I guess it seems to be.
0:27:33 > 0:27:38Particularly in the breeding season, the male can go for weeks without food
0:27:38 > 0:27:40whilst he's incubating the eggs.
0:27:40 > 0:27:44- Well, actually, that is a survival technique, isn't it?- Yes.
0:27:44 > 0:27:49Let's face it, if times get hard, if you don't have to drink for weeks on end,
0:27:49 > 0:27:55- you can travel a great distance in search of either food or water. - Yeah.
0:27:55 > 0:27:59By spreading her eggs around multiple males, and multiple nests,
0:27:59 > 0:28:05the female emu increases the chance of at least some of her offspring surviving.
0:28:14 > 0:28:18The turtle is a creature that does the opposite.
0:28:18 > 0:28:22It puts all its eggs in one very big basket.
0:28:26 > 0:28:32On average, only one out of every thousand of these baby turtles is likely to reach adulthood.
0:28:35 > 0:28:40And yet, this very different strategy has long worked for the turtle.
0:28:46 > 0:28:50After the KT impact, the seas became poisoned
0:28:50 > 0:28:53by the fallout of toxic debris and ash.
0:28:58 > 0:29:04Turtles had already been around for more than 150 million years.
0:29:04 > 0:29:07Some had even evolved into four metre long giants.
0:29:09 > 0:29:12But the KT extinction event would reduce their numbers
0:29:12 > 0:29:14and their size.
0:29:17 > 0:29:23'Doing her bit to maintain the turtles' long track record of survival is Jennie Gilbert,
0:29:23 > 0:29:27'who runs a turtle rehabilitation centre.'
0:29:27 > 0:29:29So, who have we got here?
0:29:29 > 0:29:33Her name is Angie and she's actually a mature female olive ridley.
0:29:33 > 0:29:36- And that's one of the rarer turtles? - It is.
0:29:36 > 0:29:38She is one of the rarer turtles.
0:29:38 > 0:29:41I can see some tooth marks.
0:29:41 > 0:29:44Yes, she got bitten on the top of the shell as you can see.
0:29:44 > 0:29:47She actually was attacked by a very large saltwater crocodile.
0:29:47 > 0:29:51And she also had part of her jaw hanging off.
0:29:51 > 0:29:54So we had to take that piece of jaw off.
0:29:54 > 0:30:00That proves that if a crocodile can snap at this poor animal
0:30:00 > 0:30:02and the animal survives, it shows how tough she is.
0:30:02 > 0:30:03Exactly right.
0:30:03 > 0:30:07That shell must be incredibly tough for her to survive through that.
0:30:07 > 0:30:12If you think of the size of a large saltwater crocodile, about 17 ft,
0:30:12 > 0:30:14and he has come down with his jaws on top of her
0:30:14 > 0:30:17and she's got out of it, she's a pretty tough girl.
0:30:21 > 0:30:25To examine just how tough, I want to dig deep into the anatomy
0:30:25 > 0:30:28of a recently deceased turtle found on a local beach.
0:30:30 > 0:30:33Here's our turtle. How old do you think?
0:30:33 > 0:30:36She's probably about 60-plus years.
0:30:37 > 0:30:40- And it's a...green? - Green, mature female.
0:30:40 > 0:30:45This is called a plastron and it's a series of plates, as you can see.
0:30:45 > 0:30:47- Extremely tough.- Extremely tough.
0:30:47 > 0:30:50But it's not as tough as the carapace which is on the top.
0:30:50 > 0:30:54As you can feel, the carapace is very, very tough and bony.
0:30:54 > 0:30:58'The turtle's shell is a very obvious survival trait,
0:30:58 > 0:31:02'but, believe it or not, it was once possible to have half a turtle.'
0:31:02 > 0:31:08There are fossil turtles going back to about 240 million years,
0:31:08 > 0:31:10and I think the earlier ones got the plastron first.
0:31:10 > 0:31:13- Yes, they did.- Which implies to me that they were protecting
0:31:13 > 0:31:16against something coming up and biting them from beneath.
0:31:16 > 0:31:20The plastron was developed because they used to have predators
0:31:20 > 0:31:22that used to come up underneath them in the water,
0:31:22 > 0:31:24and on the top of them they just had
0:31:24 > 0:31:27a backbone with a little bit of a shell, but not a complete covering.
0:31:27 > 0:31:32- Well, shall we open her up and have a look inside?- Yes.
0:31:33 > 0:31:39The turtle's shell is a good adaptation for surviving predators,
0:31:39 > 0:31:42but how did turtles survive through the KT?
0:31:42 > 0:31:45- This has quite an impressive intestine.- They have.
0:31:45 > 0:31:48Wrapped round like a rather unappetising sausage.
0:31:50 > 0:31:53Part of the answer lies with its lungs.
0:31:55 > 0:32:00But to get to them I need a stomach almost as strong as the turtle's.
0:32:00 > 0:32:03- Certainly a lot of bowel involved here.- Yes.
0:32:05 > 0:32:09And we've arrived at a position where we can see the lungs.
0:32:09 > 0:32:13Yes, there's a very large surface area for these lungs.
0:32:13 > 0:32:15The benefit of their lungs
0:32:15 > 0:32:19is that these animals can stay submerged up to five hours,
0:32:19 > 0:32:22but the benefit is they can take in air that can go through
0:32:22 > 0:32:26into their lungs and out into their blood and out into the muscle.
0:32:26 > 0:32:30So therefore that's why they can stay submerged for such a length of time.
0:32:30 > 0:32:32So they really are diving champions.
0:32:35 > 0:32:39Not only can turtles break records for staying submerged,
0:32:39 > 0:32:42they can also win awards for surviving without food.
0:32:44 > 0:32:47This one has been floating so long it even has barnacles.
0:32:48 > 0:32:52This was brought in and actually has floater's disease.
0:32:52 > 0:32:56As you can see, it's got air under the shell here,
0:32:56 > 0:32:59and that's caused it to float on this side.
0:32:59 > 0:33:02We've actually had animals brought in here that have been found
0:33:02 > 0:33:06and they have probably been floating for about 12 months without eating.
0:33:06 > 0:33:09Because once they float, they get this floater's disease
0:33:09 > 0:33:11and they get air under their shell
0:33:11 > 0:33:13and they can't dive down to actually feed.
0:33:13 > 0:33:16So they've been floating.
0:33:16 > 0:33:20Up to 12 months they can float and they can live on their fat stores.
0:33:20 > 0:33:22So, like crocs and snakes,
0:33:22 > 0:33:26the turtle is capable of not eating for a very long time.
0:33:27 > 0:33:29This little turtle, has it got a name yet?
0:33:29 > 0:33:32Well, Richard, it looks like a lovely turtle to me.
0:33:32 > 0:33:36It looks like a pure gentleman, so therefore it should be Richard.
0:33:37 > 0:33:39Well, I'm exceedingly flattered
0:33:39 > 0:33:44to have an ancient living fossil named in my honour.
0:33:44 > 0:33:46Thank you very much. I'm delighted.
0:33:50 > 0:33:56After more than 200 million years of survival,
0:33:56 > 0:33:58today, turtles are seriously endangered.
0:33:58 > 0:34:01This time by man.
0:34:01 > 0:34:04Humans are destroying turtle habitats
0:34:04 > 0:34:08and spawning grounds in a way even the KT could not.
0:34:12 > 0:34:15The turtle's armour can protect it from a hostile world.
0:34:17 > 0:34:20But an even more effective strategy is to use a shell
0:34:20 > 0:34:22to create a private and protected place.
0:34:24 > 0:34:27Shells allowed ocean-dwelling invertebrates
0:34:27 > 0:34:30to create their own microhabitats.
0:34:32 > 0:34:34The earliest shelled molluscs
0:34:34 > 0:34:37evolved more than 400 million years ago.
0:34:39 > 0:34:43They survived the KT and continue to grow in abundance
0:34:43 > 0:34:44here in Delaware Bay,
0:34:44 > 0:34:47clinging to the rocks and ruins on the shoreline.
0:34:51 > 0:34:53They may have survived the KT,
0:34:53 > 0:34:56but they are easy pickings for certain two-legged mammals.
0:35:03 > 0:35:05Actually rather good.
0:35:05 > 0:35:08Another way to survive a crisis is...
0:35:10 > 0:35:11..to clam up.
0:35:17 > 0:35:19A lot of molluscs came through
0:35:19 > 0:35:23because of their ability to seal themselves away from trouble.
0:35:24 > 0:35:25Mmm!
0:35:27 > 0:35:28Fairly yummy.
0:35:30 > 0:35:34Probably the most delicious of these survivors, the oyster.
0:35:41 > 0:35:44Which lives attached to rocks.
0:35:45 > 0:35:50Securely fastened to rocks, often in the inter-tidal area.
0:35:52 > 0:35:53Mmm! Yum!
0:35:56 > 0:35:59I'm eating it washed down by another survivor,
0:35:59 > 0:36:02beer from the oldest brewery in America.
0:36:05 > 0:36:09Oysters suck in water, filter and consume its nutrients
0:36:09 > 0:36:11and expel it again.
0:36:11 > 0:36:15Since some oyster species can pass more than five litres
0:36:15 > 0:36:18in a single hour, they would, in their own small way,
0:36:18 > 0:36:20and over thousands of years,
0:36:20 > 0:36:24contribute to the spring-cleaning of the seas after the crisis.
0:36:33 > 0:36:37Living in well-stirred inter-tidal waters, oysters were protected
0:36:37 > 0:36:42from the de-oxygenation event that poisoned so much marine life.
0:36:42 > 0:36:45They still prosper today at the edges of the sea,
0:36:45 > 0:36:49and they have provided man with an accessible foodstuff,
0:36:49 > 0:36:52easily prised off rocks with primitive tools
0:36:52 > 0:36:54since the early days of our species.
0:37:04 > 0:37:09The nautilus is another shelled Cretaceous survivor.
0:37:10 > 0:37:12It couldn't shut the world out completely,
0:37:12 > 0:37:15but then, as a scavenger, it didn't want to.
0:37:19 > 0:37:24The nautilus is a cephalopod, a relative of the squid
0:37:24 > 0:37:27that can live to be 20 years old.
0:37:29 > 0:37:33It uses a kind of jet propulsion to navigate itself through the depths.
0:37:35 > 0:37:38The nautilus's big eyes are misleading.
0:37:38 > 0:37:43In fact, it has poor vision and relies on its sense of smell
0:37:43 > 0:37:47to forage for food and locate potential mates.
0:37:49 > 0:37:52Perhaps smell would have been a handy survival trait
0:37:52 > 0:37:54when the sun had been blotted out
0:37:54 > 0:37:58and the oceans had been plunged into darkness.
0:38:00 > 0:38:03But it probably wasn't this that saved it.
0:38:03 > 0:38:07Once again, reproduction could have been the real key.
0:38:11 > 0:38:15This is one of the first fossils I ever found.
0:38:15 > 0:38:19Since their appearance about 400 million years ago, ammonites
0:38:19 > 0:38:23evolved into thousands of different species of every shape and size.
0:38:23 > 0:38:28And survived everything a hostile world could throw at them
0:38:28 > 0:38:31for more than 300 million years.
0:38:33 > 0:38:38Sadly, it was not these wonderful, rapidly evolving cephalopods
0:38:38 > 0:38:40that made it through the KT, but...
0:38:43 > 0:38:45..the more humble nautilus.
0:38:47 > 0:38:51Some scientists even speculate that the ammonite spawned just once
0:38:51 > 0:38:55at the end of their lives while our friend the nautilus, a superficially
0:38:55 > 0:39:01similar creature, bred several times in a lifetime and made it through.
0:39:01 > 0:39:05The nautilus lays comparatively few large eggs,
0:39:05 > 0:39:10well supplied with nutrients, useful at a time of shortage.
0:39:13 > 0:39:16The collapse of the aquatic food chain,
0:39:16 > 0:39:19just like the collapse of the terrestrial food chain,
0:39:19 > 0:39:21was a good time to be a scavenger or a bottom feeder.
0:39:25 > 0:39:29Even dead species sinking into the depths provided
0:39:29 > 0:39:33nourishment for perhaps the most famous living fossil of them all.
0:39:43 > 0:39:47The coelacanth is glimpsed only rarely and spends
0:39:47 > 0:39:52most of the time tucked out of the way in a safe corner of the ocean.
0:39:52 > 0:39:56This is the only footage of it ever shot by the BBC.
0:39:58 > 0:40:03Was it luck or its special adaptations that allowed
0:40:03 > 0:40:05this living relic to pass through the KT?
0:40:07 > 0:40:09It's tempting to look at its leisurely lifestyle,
0:40:09 > 0:40:14large eggs and habitat as a kind of passport to survival.
0:40:14 > 0:40:18But the answer may be that not only did it have
0:40:18 > 0:40:22ample food to scavenge, it also made an unappetising meal itself.
0:40:22 > 0:40:26Indeed, the coelacanth's oily innards reputedly make it
0:40:26 > 0:40:30one of the most foul-tasting creatures ever to swim the seas.
0:40:32 > 0:40:36Making yourself nasty-tasting and inedible was a tactic
0:40:36 > 0:40:39that was also being employed back on the land.
0:40:41 > 0:40:45One of the most successful plant survivors
0:40:45 > 0:40:48of the last 360 million years, ferns.
0:40:48 > 0:40:54Ferns are the first to colonise devastated landscapes.
0:40:54 > 0:40:57They lack both flowers and seeds,
0:40:57 > 0:41:02reproducing by spores carried on the underside of the leaves.
0:41:02 > 0:41:06And they release them in their millions.
0:41:06 > 0:41:10This is a male fern, a very elegant fern.
0:41:10 > 0:41:13And here, look, on the back of the leaves,
0:41:13 > 0:41:16are these little spore capsules
0:41:16 > 0:41:21which ensure their wide distribution and they're toxic.
0:41:21 > 0:41:22Few animals can eat them
0:41:22 > 0:41:27and today there are an incredible 12,000 species.
0:41:33 > 0:41:36The KT extinction event triggered what's called the fern spike,
0:41:36 > 0:41:40the sudden and widespread appearance in the fossil record
0:41:40 > 0:41:44of billions of spores derived from these ancient plants.
0:41:47 > 0:41:52The aftermath of the asteroid impact had been a disaster for many.
0:41:52 > 0:41:56But for others, it was the opportunity finally to shine.
0:41:58 > 0:42:02For the dinosaurs, big had been beautiful,
0:42:02 > 0:42:07and they had conquered almost every ecological niche available...
0:42:07 > 0:42:10except one.
0:42:12 > 0:42:16Burrowing underground were tiny mammals, like these shrews.
0:42:17 > 0:42:20Small and delicate, with high metabolism,
0:42:20 > 0:42:23short lifespans and vulnerable young,
0:42:23 > 0:42:28they were, in many ways, the most unlikely survivors of all.
0:42:32 > 0:42:33But when fiery disaster struck,
0:42:33 > 0:42:36they were tucked away safe and sound.
0:42:43 > 0:42:48Our oldest mammalian ancestors were rather inconspicuous little insect eaters,
0:42:48 > 0:42:52something like shrews, and their distant descendants...
0:42:53 > 0:42:55..this little chap.
0:42:55 > 0:42:56A common hedgehog.
0:42:56 > 0:42:59They were excellent at sniffing out food.
0:43:01 > 0:43:06Maybe the ancient mammals could seek out their fellow survivors,
0:43:06 > 0:43:09insects, from the safety of burrows,
0:43:09 > 0:43:16while so many large animals above ground died in the mayhem of the KT.
0:43:17 > 0:43:21If they could find enough food to sustain their warm-blooded metabolism,
0:43:21 > 0:43:25they could endure through hard times.
0:43:25 > 0:43:27Couldn't they?
0:43:30 > 0:43:33The meek were to inherit the Earth.
0:43:36 > 0:43:38After the dinosaurs died out,
0:43:38 > 0:43:44there was an ecological vacuum which was quickly filled by the mammals.
0:43:44 > 0:43:47The small mammals could come out of their underground burrows
0:43:47 > 0:43:50or out of the leaf litter,
0:43:50 > 0:43:52and soon they evolved into forms
0:43:52 > 0:43:55that replaced the dinosaurs that had preceded them.
0:43:55 > 0:44:00Giant herbivores, even carnivores, appeared in a short order.
0:44:13 > 0:44:16But while new species were quickly evolving
0:44:16 > 0:44:19to exploit the opportunities a changed world provided,
0:44:19 > 0:44:22in one sheltered corner of the world,
0:44:22 > 0:44:29some of the very oldest mammals had already claimed their place in the new world order.
0:44:29 > 0:44:31It's a place they still occupy.
0:44:35 > 0:44:39They're KT survivors that belong to a group of early mammals
0:44:39 > 0:44:40even older than the marsupials,
0:44:40 > 0:44:45and who still retain features inherited from their reptile ancestors.
0:44:47 > 0:44:49They are called the monotremes.
0:44:51 > 0:44:55Duckbilled, beaver-tailed, otter-footed, seal-bodied,
0:44:55 > 0:45:01it's no wonder 18th-century naturalists thought the platypus to be a mythical chimera,
0:45:01 > 0:45:07a creature stitched together by unscrupulous taxidermists that couldn't possibly be real.
0:45:07 > 0:45:09But now, I'm off to find one.
0:45:10 > 0:45:14So this is my third time in Warrawong,
0:45:14 > 0:45:17and I haven't yet seen a platypus.
0:45:17 > 0:45:18Oh, right! Hope today's the day.
0:45:18 > 0:45:23So we must very careful in describing them as in any sense primitive,
0:45:23 > 0:45:27because in a way, they're exquisitely adapted.
0:45:27 > 0:45:28They are, definitely.
0:45:28 > 0:45:32Over 100 million years these animals have been around, and they're great at hiding,
0:45:32 > 0:45:35so that's one of the reasons you haven't seen 'em yet.
0:45:35 > 0:45:37So... Yes, I'm sure!
0:45:39 > 0:45:44The habitat here in the Warrawong nature sanctuary is much as it is in the wild,
0:45:44 > 0:45:47which is ideal for the privacy-loving platypus.
0:45:49 > 0:45:52So do you have, what? Two or three, half a dozen here?
0:45:52 > 0:45:54I'd like to think we have about ten.
0:45:55 > 0:45:59We should be quiet now, because you never know,
0:45:59 > 0:46:02this might be the time to actually see the platypus.
0:46:38 > 0:46:41(I can see some ripples down there.)
0:46:47 > 0:46:49(Perhaps we should move along a bit.)
0:46:53 > 0:46:57'The platypus loves this sort of habitat,
0:46:57 > 0:47:00'but as the hours tick by, it becomes increasingly clear
0:47:00 > 0:47:04'we're about as welcome as paparazzi on a private beach.'
0:47:10 > 0:47:13It's very discreet, you have to say.
0:47:18 > 0:47:21Well, I mean, it would be great if we could see one.
0:47:30 > 0:47:31Could that be one?
0:47:35 > 0:47:40Every time I think I've seen one, another bird hops into view.
0:47:40 > 0:47:43- They're not frightened of the lights.- No, not at all.
0:47:43 > 0:47:46Our platypuses have been conditioned to have light on them,
0:47:46 > 0:47:48and they're not too fussed.
0:47:49 > 0:47:54Then, finally, after 18 years and nearly five hours,
0:47:54 > 0:47:56I see the platypus.
0:47:58 > 0:47:59(There we go!)
0:48:01 > 0:48:03There it is again.
0:48:10 > 0:48:13They lay their eggs in burrows, don't they?
0:48:13 > 0:48:15- They do, yeah.- So how many in this pond?
0:48:15 > 0:48:20I think there's about three burrows in this pond, and they're very extensive burrows.
0:48:20 > 0:48:22So when the female lays her eggs,
0:48:22 > 0:48:26she lays up to two or three eggs in the burrow,
0:48:26 > 0:48:30and they could be in the burrow for four to five months, developing.
0:48:30 > 0:48:32They take about 12 days to hatch,
0:48:32 > 0:48:35and she incubates the eggs.
0:48:36 > 0:48:38Gosh, that's a clear view.
0:48:38 > 0:48:40That's as good as you ever get.
0:48:40 > 0:48:44'As well as being an egg layer, the platypus also retained something
0:48:44 > 0:48:47'of the cold-bloodedness of its reptilian ancestors,
0:48:47 > 0:48:53'having an average body temperature five degrees centigrade colder than placental mammals.'
0:48:53 > 0:48:56I gather the platypus can be, if you don't handle it right,
0:48:56 > 0:48:58quite a dangerous animal.
0:48:58 > 0:48:59They can, definitely.
0:48:59 > 0:49:02Platypus have a venomous spear on their back ankles,
0:49:02 > 0:49:04and that's just for the males.
0:49:04 > 0:49:08They use that venomous spear against their natural enemy, which are water rats,
0:49:08 > 0:49:11and also against each other during the mating season.
0:49:11 > 0:49:14- I believe the venom is bad enough to kill a small dog?- It is.
0:49:14 > 0:49:18It caused excruciating pain to the European settlers when they first came,
0:49:18 > 0:49:21and picked these innocent-looking creatures up and got a nasty shock.
0:49:21 > 0:49:25So yet another Australian creature that causes you pain
0:49:25 > 0:49:29- if you don't do it right. - That's right, we've got lots of them in Australia!
0:49:31 > 0:49:34I came here first 18 years ago.
0:49:34 > 0:49:36I don't need to hunt the platypus now,
0:49:36 > 0:49:39I've seen one of the great survivors.
0:49:43 > 0:49:47The platypus might not be an obvious survivor,
0:49:47 > 0:49:52but its ancestors, swimming, burrowing creatures that rely on smell and survive on insects,
0:49:52 > 0:49:57were adapted to the kinds of conditions the KT crisis caused.
0:49:58 > 0:50:03Evidence suggests the platypus's earliest ancestors may have been around even longer
0:50:03 > 0:50:08than the oldest placental and marsupial mammals.
0:50:08 > 0:50:14The platypus's closest living relative is my final KT survivor.
0:50:16 > 0:50:19'It's an extraordinary creature called an echidna.'
0:50:19 > 0:50:22That way, I'd say, wouldn't you?
0:50:22 > 0:50:27'And it possesses a quality that would become key to mammals inheriting the Earth.'
0:50:29 > 0:50:33Now, where I could hear her earlier was down through there.
0:50:35 > 0:50:38The signal's not any stronger, because you see the little hill...
0:50:38 > 0:50:41'My guide is Dr Peggy Rismiller,
0:50:41 > 0:50:45'a woman who has spent much of her life protecting echidnas and their habitat.'
0:50:47 > 0:50:49She could be... A-ha.
0:50:50 > 0:50:54'Echidnas bear a close physical resemblance to giant hedgehogs,
0:50:54 > 0:50:55'but they're not closely related.'
0:51:01 > 0:51:04So yeah, they're very good at hiding.
0:51:07 > 0:51:11I think she's burrowed at the back of the tree here.
0:51:14 > 0:51:16There she goes.
0:51:16 > 0:51:18This is Big Mama. I've known her for 23 years.
0:51:21 > 0:51:25So it's a waiting game. I just wait for her to relax.
0:51:25 > 0:51:28She has the advantage of being extremely strong.
0:51:28 > 0:51:32And you always go with the spines, so in this direction,
0:51:32 > 0:51:35I'm going with the spines, and see, I'm actually...
0:51:35 > 0:51:39- Do you want that closer?- That's OK. Just a second, I'll get her out.
0:51:39 > 0:51:40OK.
0:51:40 > 0:51:45It's like digging up great spiny wheat.
0:51:45 > 0:51:47There, you see her face?
0:51:47 > 0:51:49That's her little nose sticking out there.
0:51:54 > 0:51:56You're very lucky to see her face.
0:51:56 > 0:51:59Very often the first thing they do is hide that beak
0:51:59 > 0:52:02because it's the most vulnerable part of the body.
0:52:02 > 0:52:04- How old?- I think probably about 45.
0:52:04 > 0:52:0645 years?
0:52:06 > 0:52:08That's a human lifetime!
0:52:09 > 0:52:12There you go. Have you held an echidna?
0:52:12 > 0:52:14I'm about to.
0:52:16 > 0:52:17OK.
0:52:17 > 0:52:19She's five kilos, remember. You got her?
0:52:19 > 0:52:21I've got her.
0:52:21 > 0:52:22There she is.
0:52:22 > 0:52:26She's tucked her face well inside,
0:52:26 > 0:52:31so the sensitive nose, or beak, I suppose, is protected.
0:52:31 > 0:52:34But you can see the long claws on either side,
0:52:34 > 0:52:38which make such an effective digging instrument,
0:52:38 > 0:52:40and make them so good at hiding, too.
0:52:40 > 0:52:44Echidnas are the only mammal who can dig straight down into the ground,
0:52:44 > 0:52:47because the front feet go in one direction, the hind feet go
0:52:47 > 0:52:52in the other direction, so they can go straight down and make a hole like she just came out of.
0:52:52 > 0:52:55She's sort of bunching up her spines
0:52:55 > 0:52:58to give her maximum pincushion effect.
0:52:58 > 0:52:59THEY CHUCKLE
0:53:01 > 0:53:05'Like other early mammals, the echidna eats insects
0:53:05 > 0:53:06'and other small creatures.
0:53:06 > 0:53:11'So the survival of these tiny animals helped
0:53:11 > 0:53:13'ensure its survival, in turn.
0:53:13 > 0:53:16'The echidna has been using its sensitive beak
0:53:16 > 0:53:20'to ferret out tiny prey for millions of years.'
0:53:22 > 0:53:26Now this little delicate structure is what?
0:53:26 > 0:53:27The lower jaw.
0:53:27 > 0:53:30A pair of struts, really, no more than that.
0:53:30 > 0:53:32Or something like a tuning rod,
0:53:32 > 0:53:36because when the echidna is foraging, it will put its beak on the ground,
0:53:36 > 0:53:40and they're very sensitive to vibrations, so these tuning rods
0:53:40 > 0:53:44can help it actually sense any vibration in the soil,
0:53:44 > 0:53:46which means finding their food source.
0:53:46 > 0:53:50Why do you think echidnas are great survivors?
0:53:50 > 0:53:53I think the first thing to look at is food source.
0:53:53 > 0:53:56If you're going to be a survivor, what do you eat?
0:53:56 > 0:53:58Invertebrates.
0:53:58 > 0:54:01So being an invertebrate eater makes them a good survivor.
0:54:01 > 0:54:06We know invertebrates carried through the crisis at the end of the Cretaceous, yes.
0:54:06 > 0:54:10And what's going to be around longer than anything else? Invertebrates.
0:54:10 > 0:54:13Secondly, echidnas have a low operative body temperature,
0:54:13 > 0:54:14which gives them an advantage.
0:54:14 > 0:54:18They also regulate their body temperature, in that when they go to sleep,
0:54:18 > 0:54:22they just let the body temperature go down, which means they save a lot of energy.
0:54:22 > 0:54:26There she is again. Look at that face!
0:54:26 > 0:54:29'Two vital traits shared by a number of our survivors.
0:54:29 > 0:54:32'An unfussy diet, and a slow metabolism.'
0:54:33 > 0:54:36They are also capable of hunkering down,
0:54:36 > 0:54:40of digging down and hiding from trouble.
0:54:40 > 0:54:44It's not only that, they're good at surviving natural things like fire,
0:54:44 > 0:54:46so because of their digging capabilities
0:54:46 > 0:54:50and being able to lower their body temperature and their metabolism
0:54:50 > 0:54:53during a fire situation which happens in Australia naturally,
0:54:53 > 0:54:55these guys are going to survive.
0:54:56 > 0:55:00Hiding away - another common survival technique.
0:55:02 > 0:55:04But unlike our reptile survivors,
0:55:04 > 0:55:07that produce many, well-developed offspring,
0:55:07 > 0:55:11the echidna lays a single egg, which hatches in her pouch
0:55:11 > 0:55:17and grows into an underdeveloped and hairless baby, called a puggle.
0:55:23 > 0:55:27The reproduction is quite slow. They're eight years old before they're sexually mature,
0:55:27 > 0:55:30they may only have one young every three years.
0:55:30 > 0:55:34And the puggle gets its own additional security,
0:55:34 > 0:55:35a nursery burrow.
0:55:35 > 0:55:38The amazing thing about the echidna,
0:55:38 > 0:55:41very different again from any other mammal -
0:55:41 > 0:55:46once the puggle is in the burrow, its life changes dramatically.
0:55:46 > 0:55:49When it was in the pouch, it could suckle at any time,
0:55:49 > 0:55:51- because they do suckle milk.- Yes.
0:55:51 > 0:55:52Once it's in the burrow,
0:55:52 > 0:55:57mom only comes back for two hours every five days.
0:55:57 > 0:56:00And the other advantage is they have a low temperature,
0:56:00 > 0:56:02the burrow is quite cool,
0:56:02 > 0:56:06so the young echidna is growing at a slow rate.
0:56:06 > 0:56:08But she will continue for seven months.
0:56:08 > 0:56:12So this is really rather slow child-rearing, isn't it?
0:56:12 > 0:56:15Particularly for an animal of that size.
0:56:20 > 0:56:25Investing so much time and energy into one or a few offspring
0:56:25 > 0:56:29is a distinctly mammalian reproduction strategy.
0:56:29 > 0:56:33And nurture may have been key to evolving perhaps what we regard
0:56:33 > 0:56:37as the greatest survival trait of them all.
0:56:37 > 0:56:39Intelligence.
0:56:39 > 0:56:42One thing that strikes me, I think I'm right -
0:56:42 > 0:56:45- it seems to have a rather large brain.- Good observation.
0:56:45 > 0:56:48Actually, the brain is huge for the size of the animal.
0:56:48 > 0:56:51And I think the most important part is the neocortex.
0:56:51 > 0:56:54Have you ever heard of the neocortex?
0:56:54 > 0:56:55Explain what it does.
0:56:55 > 0:56:58Well, the neocortex is the frontal part of the brain,
0:56:58 > 0:57:03where your memory, your reasoning, your personality comes from.
0:57:03 > 0:57:05And echidnas have great personalities.
0:57:05 > 0:57:08But I think the best reason I heard for the neocortex
0:57:08 > 0:57:11was from a ten-year-old student, who said,
0:57:11 > 0:57:15"You said they were around with the dinosaurs, so they have a lot to remember."
0:57:15 > 0:57:18- That's rather a good answer! - Absolutely!
0:57:22 > 0:57:26Big brains would prove to be key in the evolution
0:57:26 > 0:57:27and success of mammals.
0:57:30 > 0:57:33Today, mammals have occupied every ecological niche
0:57:33 > 0:57:36once inhabited by dinosaurs.
0:57:36 > 0:57:41Yet it still seems extraordinary that small insectivores
0:57:41 > 0:57:44could produce giant predators and potbellied grazers.
0:57:44 > 0:57:47It seems nature abhors a vacuum,
0:57:47 > 0:57:54and every vacant ecological niche is an opportunity waiting to be filled.
0:58:00 > 0:58:05'But few prehistoric bookies would have put money on mammals
0:58:05 > 0:58:07'winning the lottery of life.
0:58:07 > 0:58:10'Which, I suppose, just goes to show...'
0:58:10 > 0:58:12Sometimes, to be a survivor,
0:58:12 > 0:58:16it does no harm to have luck on your side.
0:58:16 > 0:58:20- # The winner takes it all - Takes it all
0:58:20 > 0:58:23- # The loser has to fall - Has to fall
0:58:23 > 0:58:27- # It's simple and it's plain - Yes, it's plain
0:58:27 > 0:58:30# The winner takes it all... #
0:58:32 > 0:58:38In the next episode, I go in search of survivors from the Ice Age.
0:58:41 > 0:58:44Subtitles by Red Bee Media Ltd