0:00:02 > 0:00:06The natural world is full of extraordinary animals
0:00:06 > 0:00:09with amazing life histories.
0:00:09 > 0:00:13Yet certain stories are more intriguing than most.
0:00:16 > 0:00:19The mysteries of a butterfly's life cycle
0:00:19 > 0:00:23or the strange biology of the Emperor penguin.
0:00:23 > 0:00:26Some of these creatures were surrounded by myth
0:00:26 > 0:00:30and misunderstandings for a very long time
0:00:30 > 0:00:33and some have only recently revealed their secrets.
0:00:35 > 0:00:39These are the animals that stand out from the crowd.
0:00:39 > 0:00:42The curiosities I find most fascinating of all.
0:00:51 > 0:00:54Some animals appear to protect themselves
0:00:54 > 0:00:57with formidable suits of armour.
0:00:57 > 0:01:00The rhino carries plates of thick hide on its flanks.
0:01:02 > 0:01:06While the hedgehog is covered in prickly spines.
0:01:07 > 0:01:09Both, in previous centuries,
0:01:09 > 0:01:14inspired far-fetched and outlandish ideas,
0:01:14 > 0:01:18but what is the true nature of their strange coats?
0:01:25 > 0:01:29Some animals have mastered the art of deception.
0:01:29 > 0:01:34The cuckoo tricks other birds into raising its young,
0:01:34 > 0:01:38while the death's-head hawkmoth infiltrates the nests of bees
0:01:38 > 0:01:41to steal their precious honey.
0:01:42 > 0:01:45They're cheats and impostors.
0:01:55 > 0:01:58Rhinoceroses are strange-looking creatures.
0:01:58 > 0:02:00There are five kinds.
0:02:00 > 0:02:05The Indian, this one, has a single horn, squat legs, tiny eyes...
0:02:05 > 0:02:07Whoa!
0:02:07 > 0:02:10..and thick folded skin.
0:02:10 > 0:02:13For many centuries, before any had reached Europe,
0:02:13 > 0:02:17they were surrounded by myth as much as the unicorn.
0:02:17 > 0:02:22Few people had ever seen a live rhino, but, in 1741,
0:02:22 > 0:02:26a young Indian rhinoceros called Clara came to Europe
0:02:26 > 0:02:30and she transformed our image and understanding of the rhinoceros.
0:02:31 > 0:02:33Thank you.
0:02:34 > 0:02:36Before Clara arrived,
0:02:36 > 0:02:39little was known in Europe about the rhinoceros.
0:02:39 > 0:02:44A few animals arrived here in Roman times, but they didn't last long,
0:02:44 > 0:02:47many being slaughtered during the brutal Roman Games.
0:02:48 > 0:02:50It wasn't until the 16th century
0:02:50 > 0:02:54that they first made a real mark on western society.
0:02:56 > 0:03:00In 1515, a woodcut of a rhino was created by an artist called Durer.
0:03:02 > 0:03:06It was a beautiful image of an elaborately armoured creature,
0:03:06 > 0:03:09but it was inaccurate.
0:03:09 > 0:03:13It's doubtful whether Durer ever saw a live rhinoceros.
0:03:15 > 0:03:19It's little wonder that the rhinoceros was thought of
0:03:19 > 0:03:21as a magical mythical creature
0:03:21 > 0:03:25if Durer's woodcut of 1515 was to be believed.
0:03:25 > 0:03:29He shows an armour-plated beast with a large horn
0:03:29 > 0:03:32and a strange little spike on its back.
0:03:32 > 0:03:35But in the 18th century, the perception of the rhinoceros was
0:03:35 > 0:03:41to change when Clara came to Europe on an extraordinary 17-year tour.
0:03:43 > 0:03:46Clara was captured in Assam at just a few months of age
0:03:46 > 0:03:48when hunters killed her mother.
0:03:48 > 0:03:50A director of the Dutch East India Company
0:03:50 > 0:03:53raised her in his household as a pet.
0:03:53 > 0:03:56She wandered indoors amongst the elegant furniture,
0:03:56 > 0:03:59ate from a plate and was a popular attraction at his dinner parties.
0:03:59 > 0:04:03But, inevitably, Clara got too big
0:04:03 > 0:04:06and a little-known Dutch sea captain called Van der Meer
0:04:06 > 0:04:11seized the chance to own possibly the only tame rhino in the world.
0:04:11 > 0:04:14He saw the opportunity of making a lifetime's income
0:04:14 > 0:04:17with an ambitious rhinoceros tour.
0:04:20 > 0:04:24Clara became an orphan while she was still dependent on her mother.
0:04:24 > 0:04:29Rhino calves usually stay with their mothers for up to two years,
0:04:29 > 0:04:31sustained by the milk.
0:04:31 > 0:04:34Only after that are they able to feed independently
0:04:34 > 0:04:36on soft green grass.
0:04:38 > 0:04:41Keeping a young rhino healthy was certainly a challenge,
0:04:41 > 0:04:46but Van der Meer was smart and took good care of his new charge.
0:04:48 > 0:04:50He travelled with her all the way from India
0:04:50 > 0:04:54around the Cape of Good Hope, up the coast of Africa to the Netherlands
0:04:54 > 0:04:57and his home town of Leiden.
0:04:57 > 0:05:01He discovered very soon that Clara had a huge appetite
0:05:01 > 0:05:04and he made sure that she always had plenty to eat.
0:05:05 > 0:05:10Rhinoceros spend a great deal of time feeding.
0:05:10 > 0:05:13They eat plant matter, but they don't have multiple stomachs
0:05:13 > 0:05:15to digest and absorb nutrients,
0:05:15 > 0:05:18so they need to eat large quantities of food to survive,
0:05:18 > 0:05:20up to 100 kilos a day.
0:05:23 > 0:05:27It takes a lot to fuel such an enormous body.
0:05:27 > 0:05:29An adult rhino weighs over a tonne.
0:05:31 > 0:05:33And the Indian rhino has a special mobile lip
0:05:33 > 0:05:37to help it grasp and rip up the vegetation.
0:05:42 > 0:05:46After reaching Europe, Clara lived quietly in Leiden for two years,
0:05:46 > 0:05:48feeding and growing,
0:05:48 > 0:05:52while Van der Meer made plans for his European tour.
0:05:53 > 0:05:57At the time, a live rhino was a wondrous thing,
0:05:57 > 0:06:00as Van der Meer well appreciated.
0:06:00 > 0:06:04He was a clever businessman and he knew that publicity was needed
0:06:04 > 0:06:07if his grand tour was to be a success.
0:06:09 > 0:06:12Van der Meer made an unusual alliance with an ambitious
0:06:12 > 0:06:15Dutch anatomist, BS Albinus,
0:06:15 > 0:06:19who was hoping to produce a definitive medical textbook.
0:06:19 > 0:06:21Both men were looking for publicity
0:06:21 > 0:06:24and together they commissioned Jan Wandelaar,
0:06:24 > 0:06:25an accomplished artist,
0:06:25 > 0:06:30to make prints that would serve to advertise both the book and Clara.
0:06:30 > 0:06:33They were strange but compelling pictures that combined
0:06:33 > 0:06:39precisely drawn human skeletons and detailed images of Clara.
0:06:39 > 0:06:43They were the most accurate drawings yet of the rhinoceros.
0:06:44 > 0:06:46Wandelaar sketched Clara from life.
0:06:46 > 0:06:50He was fascinated by the texture of her skin
0:06:50 > 0:06:54and he depicted a rhino more realistically than Durer did ,
0:06:54 > 0:06:55so, at last,
0:06:55 > 0:06:58the myths surrounding the animal's appearance came to an end.
0:07:00 > 0:07:03As the news of Clara's tour spread,
0:07:03 > 0:07:06everyone was eager to see this wonderful new creature
0:07:06 > 0:07:10and Clara's first trip to Vienna was for a royal appointment.
0:07:12 > 0:07:15The Empress Maria-Theresa was so eager to see Clara
0:07:15 > 0:07:18and so impressed by her appearance and good temperament,
0:07:18 > 0:07:22that she brought her children back for another private showing.
0:07:22 > 0:07:25Clara became the talk of the town
0:07:25 > 0:07:28and European heads of state were eager to meet her.
0:07:31 > 0:07:33She travelled through Europe like a celebrity
0:07:33 > 0:07:38and met both royalty and crowds of curious onlookers.
0:07:39 > 0:07:43Her horn in particular attracted much attention.
0:07:43 > 0:07:46In Paris she started a rhino-mania
0:07:46 > 0:07:51with fashionable women styling their hair 'a-la rhinoceros!'
0:07:57 > 0:08:00Some regarded rhinos as living unicorns.
0:08:00 > 0:08:03The scientific name for the Indian rhino is, in fact,
0:08:03 > 0:08:06Rhinoceros Unicornis,
0:08:06 > 0:08:11and, at the time, it was believed that the horn was made of bone.
0:08:11 > 0:08:14But this in fact is not the case.
0:08:17 > 0:08:23Rhinoceros horn grows from a spongy base positioned here on the skull.
0:08:23 > 0:08:26The horn has no bony core.
0:08:26 > 0:08:29It's made of keratin, the same substance as fingernails
0:08:29 > 0:08:32and can grow again if it's lost.
0:08:32 > 0:08:36Well, in June 1750, Clara's horn fell off,
0:08:36 > 0:08:39probably due to her rubbing it on the travel crate.
0:08:39 > 0:08:42To Van der Meer, this seemed to be a disaster
0:08:42 > 0:08:45since he had no idea that it would regrow.
0:08:45 > 0:08:48But, ingenuously, he used the event as a publicity stunt and the crowds
0:08:48 > 0:08:52flocked all the more to see Clara fearing that she might be dying.
0:08:56 > 0:08:59Even without a horn, Clara was still a fascinating creature
0:08:59 > 0:09:03and her strange armoured skin was another talking point.
0:09:03 > 0:09:08Why would such a gentle creature have such thick and elaborate folds?
0:09:10 > 0:09:15The rhinoceros's skin in some parts is almost five centimetres thick,
0:09:15 > 0:09:18nearly three times thicker than you would expect
0:09:18 > 0:09:20for an animal that size.
0:09:23 > 0:09:25We now know that, in the wild,
0:09:25 > 0:09:28rhinoceros are not always as gentle as Clara.
0:09:28 > 0:09:30They can be very aggressive,
0:09:30 > 0:09:32particularly during the mating season,
0:09:32 > 0:09:36and the tough skin provides them with some protection.
0:09:36 > 0:09:39But it also has other benefits.
0:09:39 > 0:09:45Thick skin is a good barrier against sun, flies and other parasites,
0:09:45 > 0:09:49but why the skin of an Indian rhino grows in plate-like structures
0:09:49 > 0:09:54with deep grooves has only recently been explained.
0:09:54 > 0:09:57We know that the thicker skin areas are good physical protection,
0:09:57 > 0:09:59but something deeper is going on.
0:10:01 > 0:10:05It seems that the large folds increase the surface area
0:10:05 > 0:10:10of the skin and help the rhino regulate its body temperature.
0:10:10 > 0:10:14The tissues around the grooves are particularly rich in blood vessels
0:10:14 > 0:10:17and transmit heat to the enlarged skin plates
0:10:17 > 0:10:20which act like cooling radiators.
0:10:22 > 0:10:26Indian rhinoceros bathe regularly and the folds in their skin
0:10:26 > 0:10:31not only trap water but hold it even after they come back onto land.
0:10:33 > 0:10:36So it turns out that the Indian rhinoceros's skin
0:10:36 > 0:10:40is a far more specialised structure than anyone could have imagined.
0:10:43 > 0:10:47For 17 years, Clara travelled across Europe,
0:10:47 > 0:10:50stopping off in all the main towns and cities.
0:10:50 > 0:10:53Everywhere she went, the crowds queued up to see her.
0:10:55 > 0:10:58She visited England three times,
0:10:58 > 0:11:01but her third visit proved to be her last.
0:11:03 > 0:11:07In 1758, at the age of little more than 20,
0:11:07 > 0:11:11Clara unexpectedly died in London.
0:11:11 > 0:11:15Van der Meer was deeply shocked as he thought she might live to be 100.
0:11:15 > 0:11:20Life on the road was over, but Clara's 17-year tour
0:11:20 > 0:11:24had changed the image of the rhinoceros forever.
0:11:24 > 0:11:27Durer's classic engraving of the fierce armoured beast was now
0:11:27 > 0:11:32a part of history and new accurate images were produced.
0:11:32 > 0:11:35The true Indian rhinoceros, like Clara,
0:11:35 > 0:11:37looked just like this wonderful animal
0:11:37 > 0:11:41painted by the great 18th-century artist George Stubbs.
0:11:44 > 0:11:47Van der Meer made his fortune with her on the grand tour,
0:11:47 > 0:11:50but Clara, more importantly, also enabled people
0:11:50 > 0:11:54to get a first realistic view of what a rhinoceros looks like
0:11:54 > 0:11:59and put to rest the idea of a heavily armoured mythical creature.
0:12:04 > 0:12:08There is a more familiar animal whose body armour
0:12:08 > 0:12:11also perplexed us for a surprisingly long time.
0:12:11 > 0:12:14The hedgehog.
0:12:14 > 0:12:18This delightful little creature is one of our most familiar
0:12:18 > 0:12:23garden animals and yet it's got a surprisingly unusual appearance.
0:12:23 > 0:12:28Instead of fur, like most mammals, it's got a thick coat of spines.
0:12:28 > 0:12:31The only part of its body not covered by them
0:12:31 > 0:12:33are its face and its underside.
0:12:33 > 0:12:37The hedgehog's coat may appear to be painfully prickly,
0:12:37 > 0:12:41but when the hedgehog is relaxed, it can lay its spines down flat.
0:12:41 > 0:12:45When it senses danger, of course, it rolls itself up into a ball
0:12:45 > 0:12:48and is completely hidden and protected.
0:12:48 > 0:12:50It's a formidable suit of armour, these spines.
0:12:50 > 0:12:53Nothing much can get past them.
0:12:53 > 0:12:58It seems obvious that spines must serve as a protection
0:12:58 > 0:13:02but their function was, in fact, misunderstood for a long time.
0:13:04 > 0:13:08Early books claimed the spines were used for collecting food.
0:13:08 > 0:13:11The hedgehogs were said to climb apple trees,
0:13:11 > 0:13:15knock down the fruit and roll on it, impaling the apples on their spines
0:13:15 > 0:13:18and carrying them off to their burrows.
0:13:22 > 0:13:25Today we know that hedgehogs are better at climbing
0:13:25 > 0:13:29than you might think, but they still haven't been seen to climb trees.
0:13:34 > 0:13:36And there were other myths.
0:13:36 > 0:13:40In medieval times, farmers believed that hedgehogs would steal milk
0:13:40 > 0:13:42from their cows at night.
0:13:42 > 0:13:47So the Elizabethan Parliament put a three-pence bounty on the head
0:13:47 > 0:13:51of every hedgehog and thousands were slaughtered as a result.
0:13:53 > 0:13:57Our attitude to the hedgehog is now very different.
0:14:01 > 0:14:03Today, many of us get great pleasure
0:14:03 > 0:14:08from seeing this appealing little creature in our gardens.
0:14:08 > 0:14:10We know that they are a gardener's friend,
0:14:10 > 0:14:12feeding mostly on insects and slugs
0:14:12 > 0:14:15and helping to rid our plants of pests.
0:14:15 > 0:14:18Some of us even put out special food to attract them.
0:14:20 > 0:14:25We now also understand more about the hedgehog's spines.
0:14:25 > 0:14:28They are, in fact, modified hairs,
0:14:28 > 0:14:31hollow inside but reinforced with keratin,
0:14:31 > 0:14:34the same material that forms a rhinoceros's horn.
0:14:36 > 0:14:40That makes them strong while keeping weight down to a minimum.
0:14:41 > 0:14:45A hedgehog has over 5,000 spines
0:14:45 > 0:14:49and their main purpose is indeed protection.
0:14:51 > 0:14:55But hedgehogs don't start life with a coat of armour.
0:15:01 > 0:15:04It would be painful for a hedgehog mother
0:15:04 > 0:15:06to give birth to spiny babies.
0:15:06 > 0:15:09But nature has dealt with that problem.
0:15:09 > 0:15:14Tiny hoglets are born with their spines covered by a layer of skin.
0:15:17 > 0:15:20Within a few hours, the thin quills break through.
0:15:23 > 0:15:27A baby hedgehog's first spines are soft and white
0:15:27 > 0:15:31but these soon fall out and are replaced by darker and harder ones.
0:15:40 > 0:15:44Hedgehog spines are shed and regrown at various stages in their lives,
0:15:44 > 0:15:46just like the hair of mammals.
0:15:51 > 0:15:55Surprisingly, a spiny armour is not common in the animal kingdom.
0:15:57 > 0:16:01In Europe, the hedgehog is the only one of its kind.
0:16:03 > 0:16:06But in other parts of the world, there are creatures that have
0:16:06 > 0:16:08evolved a similar spiky coat.
0:16:15 > 0:16:17This is an African crested porcupine.
0:16:18 > 0:16:22It's got a formidable coat of spines but it's no relative
0:16:22 > 0:16:26of the hedgehog and the spines are in fact very different.
0:16:26 > 0:16:30For one thing, they are very much longer.
0:16:30 > 0:16:34Normally, they lie flat against the body but if the animal is irritated,
0:16:34 > 0:16:37it directs them to give a very spectacular warning.
0:16:39 > 0:16:42Even the most ferocious predator will take care
0:16:42 > 0:16:44when approaching a porcupine.
0:16:46 > 0:16:49The quills will break off easily and become lodged in the skin.
0:16:52 > 0:16:55The lion's only chance is to attack from the front.
0:16:58 > 0:17:01As they circle, the porcupine twists and turns
0:17:01 > 0:17:03to keep its armoured back to them.
0:17:07 > 0:17:10This time, the lion got too close.
0:17:12 > 0:17:16It has no way of removing the spike and may be unable to feed.
0:17:17 > 0:17:19It could prove fatal for the predator.
0:17:24 > 0:17:28Although the porcupine's quills may appear thin, even flimsy,
0:17:28 > 0:17:32once they get stuck in your flesh, they are remarkably difficult
0:17:32 > 0:17:34and painful to remove.
0:17:34 > 0:17:37Why this should be was not known until recently.
0:17:37 > 0:17:41But when looked at under an electron microscope, you can see
0:17:41 > 0:17:45that each quill is coated with tiny backwards facing barbs.
0:17:46 > 0:17:49The barbs act like the teeth on a serrated knife,
0:17:49 > 0:17:51making it easier to penetrate the skin,
0:17:51 > 0:17:54but when it comes to removing the quills,
0:17:54 > 0:17:57the barbs have the opposite effect and act as anchors,
0:17:57 > 0:18:00preventing the spine from sliding out of the wound.
0:18:03 > 0:18:09The porcupine's spiky coat seems more formidable than the hedgehog's.
0:18:09 > 0:18:13But the hedgehog has a very effective way of protecting
0:18:13 > 0:18:16its vulnerable underbelly.
0:18:16 > 0:18:22It rolls itself into a ball, so that it is completely encased in spines.
0:18:26 > 0:18:30Foxes do attack hedgehogs but a fox must wait until the animal
0:18:30 > 0:18:34is on the move if it is to get at its unprotected underside.
0:18:37 > 0:18:40If the hedgehog stays rolled in a defensive ball,
0:18:40 > 0:18:42the fox can't harm it.
0:18:45 > 0:18:51All the hedgehog has to do is to sit it out until the fox loses interest.
0:18:59 > 0:19:02But if spines are such an effective defence,
0:19:02 > 0:19:05why don't many other animals adopt them?
0:19:05 > 0:19:09The answer seems to be connected with the difficulties
0:19:09 > 0:19:11of life with spines.
0:19:13 > 0:19:17Spines may be something of a hindrance when it comes to mating.
0:19:19 > 0:19:23Indeed, early naturalists thought that the hedgehogs must mate
0:19:23 > 0:19:27belly to belly to avoid being impaled on each other's spines.
0:19:29 > 0:19:31We now know that that's not the case.
0:19:31 > 0:19:33The spines seem to do nothing
0:19:33 > 0:19:37to hinder the ardour of a male hedgehog.
0:19:37 > 0:19:41If she is willing, he tries to oblige.
0:19:41 > 0:19:46But it still looks like a tricky and uncomfortable operation.
0:19:53 > 0:19:56Despite the limitations of a spiny coat,
0:19:56 > 0:19:59hedgehogs have remained largely unchanged
0:19:59 > 0:20:03for almost 15 million years.
0:20:03 > 0:20:06New evidence suggests that the spines may play another
0:20:06 > 0:20:09rather surprising role in their lives.
0:20:12 > 0:20:16Hedgehogs, when encountering an unfamiliar or toxic object,
0:20:16 > 0:20:21sometimes behave in a very strange way.
0:20:21 > 0:20:25They will lick and bite it until they start to foam at the mouth.
0:20:25 > 0:20:29The froth is then transferred to their spines.
0:20:30 > 0:20:34We still don't fully understand this strange behaviour.
0:20:35 > 0:20:39It may help to camouflage the hedgehog's smell,
0:20:39 > 0:20:42or make the spiny coat more distasteful to predators.
0:20:46 > 0:20:50Or maybe it helps hedgehogs communicate with each other.
0:20:50 > 0:20:53Or make them more attractive to the opposite sex.
0:20:54 > 0:20:59We might one day discover its true purpose but we haven't yet.
0:21:05 > 0:21:10Our familiar British hedgehog has provoked some very strange
0:21:10 > 0:21:13and far-fetched ideas, but, for many of us,
0:21:13 > 0:21:17it remains one of the most engaging animals in the British countryside,
0:21:17 > 0:21:21and its prickly coat makes it that much more attractive.
0:21:24 > 0:21:28So, it turns out that some of the early ideas about the purpose
0:21:28 > 0:21:30of the rhino's armour and the hedgehog's spines
0:21:30 > 0:21:33were only partly correct.
0:21:33 > 0:21:38Their true functions are far more complex than we yet realise.
0:21:46 > 0:21:50CUCKOO CALLS
0:21:50 > 0:21:55The call of the cuckoo has long been regarded as a sign of spring.
0:21:55 > 0:21:59But, in fact, it's the call of a killer and a cheat.
0:21:59 > 0:22:03The cuckoo lays its egg in the nests of other birds and somehow
0:22:03 > 0:22:08persuades them to treat it and its chick as if it were their own.
0:22:08 > 0:22:10How does it get away with it?
0:22:10 > 0:22:14It's a question that has puzzled people for centuries.
0:22:15 > 0:22:18In Britain, the cuckoo arrives at a time
0:22:18 > 0:22:21when most birds are nesting and laying eggs.
0:22:21 > 0:22:26Early egg collectors noticed that the nests of some birds
0:22:26 > 0:22:29had a slightly odd-looking egg in them.
0:22:29 > 0:22:32These are the eggs laid by a number of different birds.
0:22:32 > 0:22:38A marsh warbler, spotted flycatcher, a linnet and a whitethroat.
0:22:38 > 0:22:43Amongst each of those clutches, there is a fraudster, a cuckoo egg,
0:22:43 > 0:22:45which mimics that of its host.
0:22:48 > 0:22:51Although cuckoos are long known to lay their eggs in the nests
0:22:51 > 0:22:55of other birds, no-one had actually described it happening.
0:22:56 > 0:23:00Then, in the 18th century, an English country doctor
0:23:00 > 0:23:04with an interest in natural history decided to investigate.
0:23:06 > 0:23:10Edward Jenner lived here in Berkeley, Gloucestershire,
0:23:10 > 0:23:15and is best known for his work on the smallpox vaccine.
0:23:15 > 0:23:18In fact, he is said to be the father of vaccination and that
0:23:18 > 0:23:23his work has saved more human lives than that of any other man.
0:23:23 > 0:23:28What is less known is that he first achieved scientific distinction
0:23:28 > 0:23:31by his observations on the behaviour of the cuckoo.
0:23:35 > 0:23:38At the time, it was believed that a cuckoo removes
0:23:38 > 0:23:41all of the eggs in a nest and then lays its own.
0:23:43 > 0:23:46By doing so, it would ensure its own chick gets all the food
0:23:46 > 0:23:49brought in by the unwitting nest owners.
0:23:51 > 0:23:55But Edward Jenner's detailed observations were to reveal
0:23:55 > 0:23:57a rather darker tale.
0:23:59 > 0:24:03Jenner's work on cuckoos was published in 1788
0:24:03 > 0:24:07here in the Philosophical Transactions of the Royal Society,
0:24:07 > 0:24:10the world's first scientific society.
0:24:10 > 0:24:12It was entitled simply...
0:24:12 > 0:24:15"Observations on the natural history of the cuckoo"
0:24:15 > 0:24:17by Mr Edward Jenner.
0:24:17 > 0:24:21In it, he reported that it was not the parent cuckoo
0:24:21 > 0:24:23but the newly hatched chick which pushes the eggs
0:24:23 > 0:24:26and nestlings of the foster parents out of the nest.
0:24:27 > 0:24:29As soon as it hatches,
0:24:29 > 0:24:34the cuckoo chick's instinct is to kill anything else in the nest.
0:24:34 > 0:24:36It's still blind and naked
0:24:36 > 0:24:39but it has a cup-shaped depression on its back
0:24:39 > 0:24:41into which an egg fits perfectly.
0:24:43 > 0:24:49But sometimes the other eggs hatch earlier and Jenner's observations
0:24:49 > 0:24:51of how the cuckoo chick deals with its nest mates
0:24:51 > 0:24:53were quite shocking.
0:24:55 > 0:24:56He writes...
0:24:56 > 0:24:59"the moment of accomplishing this was very curious.
0:24:59 > 0:25:03"The little animal, with the assistance of its rump and wings,
0:25:03 > 0:25:05"contrived to get the bird on its back
0:25:05 > 0:25:09"and, making a lodgement of the burden by elevating its elbows,
0:25:09 > 0:25:12"clambered backwards with it up the side of the nest
0:25:12 > 0:25:15"until it reached the top, where, resting for a moment,
0:25:15 > 0:25:18"it threw off its load with a jerk
0:25:18 > 0:25:22"and quite disengaged it from the nest."
0:25:22 > 0:25:25The real villain had been uncovered.
0:25:25 > 0:25:29Jenner's views were met with incredulity and some disbelief,
0:25:29 > 0:25:33but nonetheless they earned him the Fellowship of the Royal Society.
0:25:33 > 0:25:35It was the greatest honour that could be given to
0:25:35 > 0:25:37a scientist at the time.
0:25:38 > 0:25:40Jenner's observations had revealed
0:25:40 > 0:25:44the true nature of the cuckoo's deception.
0:25:44 > 0:25:47But it still wasn't clear why the cuckoos should opt for this
0:25:47 > 0:25:50strange way of raising its young.
0:25:53 > 0:25:57It wasn't until 100 years later that Charles Darwin finally
0:25:57 > 0:26:01provided an explanation with his theory of evolution.
0:26:02 > 0:26:04The cuckoo's behaviour has evolved
0:26:04 > 0:26:07to increase its own breeding success.
0:26:07 > 0:26:09By avoiding the task of raising chicks,
0:26:09 > 0:26:13the cuckoo can lay more eggs than any other bird,
0:26:13 > 0:26:16as many as 25 in a season.
0:26:19 > 0:26:22While it makes evolutionary sense for the cuckoo
0:26:22 > 0:26:25to lay its eggs in the nests of others, what about its victims?
0:26:25 > 0:26:28Why do they put up with this trickery?
0:26:28 > 0:26:31It seems that they sometimes don't.
0:26:32 > 0:26:36This was revealed in an early natural history film in 1920.
0:26:38 > 0:26:42The Cuckoo's Secret was made by Edgar Chance and Oliver Pike,
0:26:42 > 0:26:46an egg collector and a wildlife film maker.
0:26:46 > 0:26:49Chance was fascinated by cuckoos
0:26:49 > 0:26:51and spent a great deal of time following them.
0:26:51 > 0:26:55He was the first person known to see a cuckoo lay its egg.
0:26:57 > 0:27:02The deception involves stealth and speed.
0:27:02 > 0:27:06The female waits until a nest is unattended and then she strikes.
0:27:06 > 0:27:09But if she is spotted, the owners fight back.
0:27:10 > 0:27:12If she is successful,
0:27:12 > 0:27:16the whole deception takes less than ten seconds.
0:27:16 > 0:27:20She removes and eats just one egg and replaces it with her own.
0:27:25 > 0:27:28The Chance and Pike film solved one mystery,
0:27:28 > 0:27:30but there were still others.
0:27:31 > 0:27:33How does the cuckoo choose its victim?
0:27:34 > 0:27:38And why don't the nest owners reject the alien egg?
0:27:47 > 0:27:50Reed warblers are one of the cuckoo's main targets
0:27:50 > 0:27:53and the pair has a nest just in here.
0:27:58 > 0:28:01The female warbler has laid four speckled eggs,
0:28:01 > 0:28:05and, using a model egg, I can illustrate the cuckoo's trickery.
0:28:07 > 0:28:10This is the sort of egg that a cuckoo would lay
0:28:10 > 0:28:12in the reed warbler's nest.
0:28:13 > 0:28:18It matches the reed warbler's actual egg very closely in colour.
0:28:20 > 0:28:24Experiments with model eggs have shown that reed warblers
0:28:24 > 0:28:27have become very good at recognising an alien egg
0:28:27 > 0:28:32and either throw it out or desert their nest to start afresh.
0:28:32 > 0:28:36So the cuckoo has to make sure that it produces an egg
0:28:36 > 0:28:37that is a very good match.
0:28:41 > 0:28:47The cuckoo and its victims are evolving competitively.
0:28:47 > 0:28:50With each generation, cuckoos improve their mimicry,
0:28:50 > 0:28:54while the nest owners become better at spotting a foreign egg.
0:28:56 > 0:28:58While many birds are very good
0:28:58 > 0:29:00at detecting a strange egg in their nest,
0:29:00 > 0:29:03they seem incapable of recognising
0:29:03 > 0:29:05the monstrous cuckoo chick as an impostor.
0:29:08 > 0:29:11But the deception is not complete.
0:29:11 > 0:29:14The young cuckoo is much larger than the reed warbler chick
0:29:14 > 0:29:17so it also needs a lot more food.
0:29:17 > 0:29:19How does it get enough?
0:29:21 > 0:29:23The cuckoo has a solution.
0:29:23 > 0:29:27It now uses vocal deception to trick its foster parents
0:29:27 > 0:29:29into providing more food.
0:29:31 > 0:29:34This is a sonogram of the sound waves produced by a single
0:29:34 > 0:29:37reed warbler chick begging for food.
0:29:37 > 0:29:40Below it is the call of a cuckoo chick,
0:29:40 > 0:29:43and, as you can see, it looks very different.
0:29:43 > 0:29:47In fact, it more closely resembles
0:29:47 > 0:29:51the calls of a whole nestful of reed warbler chicks.
0:29:53 > 0:29:58So, the cuckoo chick's call is a super stimulus
0:29:58 > 0:30:02that sounds like a whole nestful of chicks.
0:30:02 > 0:30:04And it appears to work.
0:30:06 > 0:30:08The adult birds rush back and forth,
0:30:08 > 0:30:11providing the impostor with the same amount of food
0:30:11 > 0:30:14as they would for an entire brood of their own.
0:30:18 > 0:30:21At three weeks old, the cuckoo chick
0:30:21 > 0:30:23has spilled out of the nest.
0:30:23 > 0:30:27It's now almost eight times the size of its foster parent.
0:30:33 > 0:30:35It was over 200 years ago
0:30:35 > 0:30:37that Edward Jenner first shocked us
0:30:37 > 0:30:41with his revelation of the cuckoo's extraordinary lifestyle.
0:30:43 > 0:30:46Now we know that its unusual behaviour
0:30:46 > 0:30:48is due to an extraordinary arms race
0:30:48 > 0:30:51that has resulted in one of the most fascinating
0:30:51 > 0:30:53specialisations in nature.
0:30:59 > 0:31:04The cuckoo's success relies on deceiving just two parent birds.
0:31:06 > 0:31:08But our second subject is a moth
0:31:08 > 0:31:11that is able to deceive hundreds of bees.
0:31:11 > 0:31:13How does it infiltrate
0:31:13 > 0:31:16one of the most heavily guarded nests in nature?
0:31:19 > 0:31:22This wonderful creature was once
0:31:22 > 0:31:25one of the most feared insects in Europe.
0:31:25 > 0:31:27It's a death's-head hawkmoth,
0:31:27 > 0:31:30and it's easy enough to see how it got its name.
0:31:30 > 0:31:32It has this mark on its back
0:31:32 > 0:31:35that looks just like a human skull.
0:31:35 > 0:31:38This gave it a bad reputation that lasted for centuries,
0:31:38 > 0:31:42but now there are new ideas about this moth's strange appearance
0:31:42 > 0:31:46that may help explain its extraordinary ability
0:31:46 > 0:31:48to rob hives without being stung.
0:31:52 > 0:31:55Death's-head hawkmoths are a rare sight Britain,
0:31:55 > 0:31:58for they spend most of their lives in Africa and Asia.
0:32:00 > 0:32:02But every summer a small number of migrants
0:32:02 > 0:32:04arrive in northern Europe,
0:32:04 > 0:32:08and, if the weather is warm enough, they breed.
0:32:10 > 0:32:14Their caterpillars, unlike the drab adult moths,
0:32:14 > 0:32:15are beautifully coloured.
0:32:18 > 0:32:20After feeding for several weeks
0:32:20 > 0:32:22they can grow to a length of 13 centimetres.
0:32:25 > 0:32:29Once ready to become adults, they pupate in the soil
0:32:29 > 0:32:33and emerge as the sinister, strangely patterned moths.
0:32:38 > 0:32:40In the early 19th century,
0:32:40 > 0:32:44a region of northern France was hit by a terrible pestilence,
0:32:44 > 0:32:47and, at the same time, a large number of hawkmoths
0:32:47 > 0:32:48were seen in the area.
0:32:48 > 0:32:53The local people linked the deaths to these night-flying insects.
0:32:53 > 0:32:57But there was another even more disturbing side to this moth.
0:32:57 > 0:33:00It could make an unusual noise.
0:33:01 > 0:33:03SQUEAKING
0:33:03 > 0:33:04There.
0:33:04 > 0:33:05A strange squeak.
0:33:05 > 0:33:09And that only added to its chilling reputation.
0:33:13 > 0:33:15Moths don't usually squeak.
0:33:17 > 0:33:21Tiger moths sometimes produce ultrasonic warning clicks
0:33:21 > 0:33:25that tell bats that they're poisonous and not good to eat,
0:33:25 > 0:33:27but this is not a noise we can generally hear.
0:33:29 > 0:33:31Perhaps the death's-head hawkmoth squeaks
0:33:31 > 0:33:33to scare predators like birds.
0:33:35 > 0:33:37However, other large migratory moths
0:33:37 > 0:33:39don't make such a sound.
0:33:41 > 0:33:43This makes the death's-head hawkmoth's squeak
0:33:43 > 0:33:45all the more surprising,
0:33:45 > 0:33:48and it has intrigued people for centuries.
0:33:50 > 0:33:53These moths are more than 200 years old.
0:33:53 > 0:33:57We know that because the handwritten label there tells us
0:33:57 > 0:34:02they were collected in 1801 by a Robert Darling Willis,
0:34:02 > 0:34:06the personal physician to King George III.
0:34:06 > 0:34:08George III is well-known as the king
0:34:08 > 0:34:10who suffered from bouts of madness,
0:34:10 > 0:34:13and, on a visit to see the king during one of them,
0:34:13 > 0:34:17Dr Willis discovered these large moths in the monarch's bedchamber.
0:34:18 > 0:34:22Unable to identify them, the doctor sent them to his grandson,
0:34:22 > 0:34:24who was at that time superintendent
0:34:24 > 0:34:26at the Museum of Zoology in Cambridge.
0:34:26 > 0:34:30He confirmed that they were death's-head hawkmoths,
0:34:30 > 0:34:33and, unusually for an insect,
0:34:33 > 0:34:35this moth produces a loud call
0:34:35 > 0:34:38that has been likened to the mournful cry
0:34:38 > 0:34:40of a grief-stricken child.
0:34:41 > 0:34:45Did the disturbed king hear the plaintive calls of a hawkmoth?
0:34:45 > 0:34:47That we don't know.
0:34:47 > 0:34:50But certainly many of the ordinary people of the 19th century
0:34:50 > 0:34:54were struck with a sense of terror whenever this moth appeared.
0:34:56 > 0:35:00The moths' unusual appearance and strange behaviour baffled people.
0:35:02 > 0:35:05But, in nature, such traits usually have a purpose.
0:35:06 > 0:35:09And it may be for the death's-head hawkmoth
0:35:09 > 0:35:13that they enable it to break into beehives and steal their honey.
0:35:15 > 0:35:18These are the giant honey bees of south-east Asia,
0:35:18 > 0:35:22and they form some of the largest bee colonies in the world.
0:35:24 > 0:35:27I once got up close to one in order to demonstrate
0:35:27 > 0:35:30their response to a predator.
0:35:30 > 0:35:32I had a model of a large hornet,
0:35:32 > 0:35:35which produced a kind of Mexican wave,
0:35:35 > 0:35:38and that makes it very difficult for an aggressor to land.
0:35:38 > 0:35:40BUZZING
0:35:40 > 0:35:44This covering of bees looks impossible to penetrate.
0:35:47 > 0:35:48But at night
0:35:48 > 0:35:51a thief can break through their ranks.
0:35:51 > 0:35:55A death's-head hawkmoth lands on the carpet of bees
0:35:55 > 0:35:58and pushes its way through without being attacked.
0:35:59 > 0:36:02In just a few seconds, it takes some sips of honey
0:36:02 > 0:36:03and emerges unharmed.
0:36:05 > 0:36:07Getting past the guard bees is quite a feat,
0:36:07 > 0:36:11but surviving inside is even more astounding.
0:36:16 > 0:36:20Death's-head hawkmoths raid domestic beehives too,
0:36:20 > 0:36:21and can be quite a pest.
0:36:28 > 0:36:32Somehow, the moth slips past the guards and, as if invisible,
0:36:32 > 0:36:36walks through the hive, heading straight for the honeycomb.
0:36:38 > 0:36:40It then feeds unnoticed.
0:36:42 > 0:36:43How does it do this?
0:36:46 > 0:36:49One theory proposes that its spooky appearance
0:36:49 > 0:36:51may help it avoid being attacked.
0:36:51 > 0:36:54BUZZING
0:36:54 > 0:36:56Miriam Rothschild, a great entomologist
0:36:56 > 0:36:59and expert on fleas and butterflies,
0:36:59 > 0:37:01suggested that the moth's skull pattern looks like
0:37:01 > 0:37:03the head of a worker bee,
0:37:03 > 0:37:07and that this could play a role in the moth's deception.
0:37:07 > 0:37:09Well, this is a photograph
0:37:09 > 0:37:12of a worker bee face taken through a microscope.
0:37:12 > 0:37:16Let's see how it looks next to a close-up photo
0:37:16 > 0:37:18of the skull pattern of the moth.
0:37:21 > 0:37:22There.
0:37:22 > 0:37:25Well, I suppose there's a slight resemblance,
0:37:25 > 0:37:28but given the fact that most moths raid beehives and nests
0:37:28 > 0:37:31during the night, it's unlikely the bees
0:37:31 > 0:37:33could see that much detail.
0:37:33 > 0:37:37The most likely answer lies in the scent the moth gives off.
0:37:40 > 0:37:42In America in the 1950s,
0:37:42 > 0:37:45a German entomologist called Thomas Eisner
0:37:45 > 0:37:48studied chemical ecology - in particular,
0:37:48 > 0:37:50the chemical defences of insects.
0:37:53 > 0:37:57Most famously, he illustrated how bombardier beetles
0:37:57 > 0:37:59fire hot acid onto a predator.
0:38:03 > 0:38:05He also studied moths,
0:38:05 > 0:38:08and showed that the feathery projections on their abdomens
0:38:08 > 0:38:12and their large antennae were used to produce and pick up scent.
0:38:13 > 0:38:17It seemed that many insects were using scent in surprising ways.
0:38:19 > 0:38:22Tests on the chemical scents produced by hawkmoths
0:38:22 > 0:38:26reveal a remarkable similarity to those produced by the worker bees
0:38:26 > 0:38:28in the hives that they raid.
0:38:28 > 0:38:30Their scent is not identical,
0:38:30 > 0:38:32but it contains several key chemicals
0:38:32 > 0:38:34that exactly match those produced by bees.
0:38:37 > 0:38:40So the death's-head hawkmoth's scent
0:38:40 > 0:38:43acts as an invisibility cloak
0:38:43 > 0:38:46that makes it undetectable to the worker bees in the nest.
0:38:51 > 0:38:53With thick scales on its body,
0:38:53 > 0:38:55clawed feet that grip the honeycomb,
0:38:55 > 0:38:58and a short, pointed proboscis to pierce the honey cells,
0:38:58 > 0:39:02the moth has evolved into an effective hive robber.
0:39:05 > 0:39:08But there is another, even more impressive impostor
0:39:08 > 0:39:11that can also penetrate the protective defences
0:39:11 > 0:39:13of an insect colony.
0:39:13 > 0:39:16Its victims are not bees but ants.
0:39:18 > 0:39:21The impostor that invades this ant nest
0:39:21 > 0:39:23doesn't get in there by flying.
0:39:23 > 0:39:25Nothing as blatant as that.
0:39:25 > 0:39:29Instead, the caterpillars of some species of blue butterfly,
0:39:29 > 0:39:34like this one, wait for red ants to collect them.
0:39:34 > 0:39:37Remarkably, passing ants don't kill them.
0:39:37 > 0:39:40They pick them up and take them back into their nest.
0:39:40 > 0:39:44The cuckoo caterpillar will stay inside the nest
0:39:44 > 0:39:46for up to ten months.
0:39:46 > 0:39:48Just like the death's-head hawkmoths,
0:39:48 > 0:39:51it produces a chemical scent that deceives the ants.
0:39:54 > 0:39:58This pink caterpillar, which belongs to the alcon blue butterfly,
0:39:58 > 0:40:00has been collected because, to them,
0:40:00 > 0:40:04it smells just like the young of their own nest.
0:40:04 > 0:40:07They become controlled by the impostor's intoxicating scent,
0:40:07 > 0:40:10and feed the butterfly larva even more regularly
0:40:10 > 0:40:12than they do their own.
0:40:14 > 0:40:18There's another way this impostor pulls off its deceptive trick.
0:40:18 > 0:40:20When it's inside the nest,
0:40:20 > 0:40:24the butterfly larva makes a strange chattering noise.
0:40:24 > 0:40:25To our ears, it's very faint,
0:40:25 > 0:40:28but it's clear enough to other insects. This is it.
0:40:30 > 0:40:32CHATTERING NOISE
0:40:32 > 0:40:36And this is the sound that's made by a queen ant.
0:40:38 > 0:40:41SIMILAR CHATTERING NOISE
0:40:43 > 0:40:46To worker ants, these calls are very similar,
0:40:46 > 0:40:49and they react by treating the butterfly larva
0:40:49 > 0:40:51as if it's one of their own.
0:40:53 > 0:40:57Caterpillars of the blue butterfly are impressive impostors.
0:40:57 > 0:41:00Not only do they mimic the scent of the ants,
0:41:00 > 0:41:03but their queen's calls too.
0:41:03 > 0:41:06This seems to trump the death's-head hawkmoth's ability
0:41:06 > 0:41:08as a nest invader.
0:41:11 > 0:41:15But the hawkmoth may also be using sound to trick its victims.
0:41:18 > 0:41:22Remember the eerie squeak that was thought to be so frightening?
0:41:23 > 0:41:24SQUEAKING
0:41:24 > 0:41:26There.
0:41:26 > 0:41:29The hawkmoth makes this sound inside the beehive
0:41:29 > 0:41:31when it enters to steal honey.
0:41:31 > 0:41:35It's been suggested that this might calm the bees,
0:41:35 > 0:41:38because the squeak is thought to sound like the piping call
0:41:38 > 0:41:41that the queen honey bee makes to pacify her workers.
0:41:43 > 0:41:46We can't be sure if the call and the strange skull marking
0:41:46 > 0:41:49evolved to deceive bees, but we can be certain
0:41:49 > 0:41:52that the death's-head hawkmoth's life as an impostor
0:41:52 > 0:41:55is more curious than the superstitions
0:41:55 > 0:41:58that have surrounded it for hundreds of years.
0:42:00 > 0:42:04The cuckoo and the hawkmoth are both audacious impostors,
0:42:04 > 0:42:08but the cuckoo's ability to make its victim raise its young
0:42:08 > 0:42:11is perhaps the most accomplished deception of all.