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The natural world is full of extraordinary animals
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with amazing life histories.
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Yet certain stories are more intriguing than most.
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The mysteries of a butterfly's life cycle
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or the strange biology of the Emperor penguin.
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Some of these creatures were surrounded by myth
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and misunderstandings for a very long time
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and some have only recently revealed their secrets.
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These are the animals that stand out from the crowd.
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The curiosities I find most fascinating of all.
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Some animals appear to protect themselves
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with formidable suits of armour.
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The rhino carries plates of thick hide on its flanks.
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While the hedgehog is covered in prickly spines.
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Both, in previous centuries,
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inspired far-fetched and outlandish ideas,
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but what is the true nature of their strange coats?
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Some animals have mastered the art of deception.
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The cuckoo tricks other birds into raising its young,
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while the death's-head hawkmoth infiltrates the nests of bees
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to steal their precious honey.
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They're cheats and impostors.
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Rhinoceroses are strange-looking creatures.
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There are five kinds.
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The Indian, this one, has a single horn, squat legs, tiny eyes...
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Whoa!
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..and thick folded skin.
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For many centuries, before any had reached Europe,
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they were surrounded by myth as much as the unicorn.
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Few people had ever seen a live rhino, but, in 1741,
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a young Indian rhinoceros called Clara came to Europe
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and she transformed our image and understanding of the rhinoceros.
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Thank you.
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Before Clara arrived,
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little was known in Europe about the rhinoceros.
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A few animals arrived here in Roman times, but they didn't last long,
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many being slaughtered during the brutal Roman Games.
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It wasn't until the 16th century
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that they first made a real mark on western society.
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In 1515, a woodcut of a rhino was created by an artist called Durer.
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It was a beautiful image of an elaborately armoured creature,
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but it was inaccurate.
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It's doubtful whether Durer ever saw a live rhinoceros.
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It's little wonder that the rhinoceros was thought of
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as a magical mythical creature
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if Durer's woodcut of 1515 was to be believed.
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He shows an armour-plated beast with a large horn
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and a strange little spike on its back.
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But in the 18th century, the perception of the rhinoceros was
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to change when Clara came to Europe on an extraordinary 17-year tour.
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Clara was captured in Assam at just a few months of age
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when hunters killed her mother.
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A director of the Dutch East India Company
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raised her in his household as a pet.
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She wandered indoors amongst the elegant furniture,
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ate from a plate and was a popular attraction at his dinner parties.
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But, inevitably, Clara got too big
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and a little-known Dutch sea captain called Van der Meer
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seized the chance to own possibly the only tame rhino in the world.
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He saw the opportunity of making a lifetime's income
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with an ambitious rhinoceros tour.
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Clara became an orphan while she was still dependent on her mother.
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Rhino calves usually stay with their mothers for up to two years,
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sustained by the milk.
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Only after that are they able to feed independently
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on soft green grass.
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Keeping a young rhino healthy was certainly a challenge,
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but Van der Meer was smart and took good care of his new charge.
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He travelled with her all the way from India
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around the Cape of Good Hope, up the coast of Africa to the Netherlands
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and his home town of Leiden.
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He discovered very soon that Clara had a huge appetite
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and he made sure that she always had plenty to eat.
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Rhinoceros spend a great deal of time feeding.
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They eat plant matter, but they don't have multiple stomachs
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to digest and absorb nutrients,
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so they need to eat large quantities of food to survive,
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up to 100 kilos a day.
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It takes a lot to fuel such an enormous body.
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An adult rhino weighs over a tonne.
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And the Indian rhino has a special mobile lip
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to help it grasp and rip up the vegetation.
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After reaching Europe, Clara lived quietly in Leiden for two years,
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feeding and growing,
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while Van der Meer made plans for his European tour.
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At the time, a live rhino was a wondrous thing,
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as Van der Meer well appreciated.
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He was a clever businessman and he knew that publicity was needed
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if his grand tour was to be a success.
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Van der Meer made an unusual alliance with an ambitious
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Dutch anatomist, BS Albinus,
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who was hoping to produce a definitive medical textbook.
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Both men were looking for publicity
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and together they commissioned Jan Wandelaar,
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an accomplished artist,
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to make prints that would serve to advertise both the book and Clara.
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They were strange but compelling pictures that combined
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precisely drawn human skeletons and detailed images of Clara.
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They were the most accurate drawings yet of the rhinoceros.
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Wandelaar sketched Clara from life.
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He was fascinated by the texture of her skin
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and he depicted a rhino more realistically than Durer did ,
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so, at last,
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the myths surrounding the animal's appearance came to an end.
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As the news of Clara's tour spread,
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everyone was eager to see this wonderful new creature
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and Clara's first trip to Vienna was for a royal appointment.
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The Empress Maria-Theresa was so eager to see Clara
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and so impressed by her appearance and good temperament,
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that she brought her children back for another private showing.
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Clara became the talk of the town
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and European heads of state were eager to meet her.
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She travelled through Europe like a celebrity
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and met both royalty and crowds of curious onlookers.
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Her horn in particular attracted much attention.
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In Paris she started a rhino-mania
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with fashionable women styling their hair 'a-la rhinoceros!'
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Some regarded rhinos as living unicorns.
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The scientific name for the Indian rhino is, in fact,
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Rhinoceros Unicornis,
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and, at the time, it was believed that the horn was made of bone.
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But this in fact is not the case.
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Rhinoceros horn grows from a spongy base positioned here on the skull.
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The horn has no bony core.
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It's made of keratin, the same substance as fingernails
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and can grow again if it's lost.
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Well, in June 1750, Clara's horn fell off,
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probably due to her rubbing it on the travel crate.
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To Van der Meer, this seemed to be a disaster
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since he had no idea that it would regrow.
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But, ingenuously, he used the event as a publicity stunt and the crowds
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flocked all the more to see Clara fearing that she might be dying.
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Even without a horn, Clara was still a fascinating creature
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and her strange armoured skin was another talking point.
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Why would such a gentle creature have such thick and elaborate folds?
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The rhinoceros's skin in some parts is almost five centimetres thick,
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nearly three times thicker than you would expect
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for an animal that size.
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We now know that, in the wild,
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rhinoceros are not always as gentle as Clara.
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They can be very aggressive,
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particularly during the mating season,
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and the tough skin provides them with some protection.
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But it also has other benefits.
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Thick skin is a good barrier against sun, flies and other parasites,
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but why the skin of an Indian rhino grows in plate-like structures
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with deep grooves has only recently been explained.
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We know that the thicker skin areas are good physical protection,
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but something deeper is going on.
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It seems that the large folds increase the surface area
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of the skin and help the rhino regulate its body temperature.
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The tissues around the grooves are particularly rich in blood vessels
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and transmit heat to the enlarged skin plates
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which act like cooling radiators.
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Indian rhinoceros bathe regularly and the folds in their skin
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not only trap water but hold it even after they come back onto land.
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So it turns out that the Indian rhinoceros's skin
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is a far more specialised structure than anyone could have imagined.
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For 17 years, Clara travelled across Europe,
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stopping off in all the main towns and cities.
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Everywhere she went, the crowds queued up to see her.
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She visited England three times,
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but her third visit proved to be her last.
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In 1758, at the age of little more than 20,
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Clara unexpectedly died in London.
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Van der Meer was deeply shocked as he thought she might live to be 100.
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Life on the road was over, but Clara's 17-year tour
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had changed the image of the rhinoceros forever.
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Durer's classic engraving of the fierce armoured beast was now
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a part of history and new accurate images were produced.
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The true Indian rhinoceros, like Clara,
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looked just like this wonderful animal
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painted by the great 18th-century artist George Stubbs.
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Van der Meer made his fortune with her on the grand tour,
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but Clara, more importantly, also enabled people
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to get a first realistic view of what a rhinoceros looks like
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and put to rest the idea of a heavily armoured mythical creature.
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There is a more familiar animal whose body armour
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also perplexed us for a surprisingly long time.
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The hedgehog.
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This delightful little creature is one of our most familiar
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garden animals and yet it's got a surprisingly unusual appearance.
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Instead of fur, like most mammals, it's got a thick coat of spines.
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The only part of its body not covered by them
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are its face and its underside.
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The hedgehog's coat may appear to be painfully prickly,
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but when the hedgehog is relaxed, it can lay its spines down flat.
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When it senses danger, of course, it rolls itself up into a ball
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and is completely hidden and protected.
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It's a formidable suit of armour, these spines.
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Nothing much can get past them.
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It seems obvious that spines must serve as a protection
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but their function was, in fact, misunderstood for a long time.
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Early books claimed the spines were used for collecting food.
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The hedgehogs were said to climb apple trees,
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knock down the fruit and roll on it, impaling the apples on their spines
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and carrying them off to their burrows.
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Today we know that hedgehogs are better at climbing
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than you might think, but they still haven't been seen to climb trees.
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And there were other myths.
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In medieval times, farmers believed that hedgehogs would steal milk
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from their cows at night.
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So the Elizabethan Parliament put a three-pence bounty on the head
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of every hedgehog and thousands were slaughtered as a result.
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Our attitude to the hedgehog is now very different.
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Today, many of us get great pleasure
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from seeing this appealing little creature in our gardens.
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We know that they are a gardener's friend,
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feeding mostly on insects and slugs
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and helping to rid our plants of pests.
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Some of us even put out special food to attract them.
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We now also understand more about the hedgehog's spines.
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They are, in fact, modified hairs,
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hollow inside but reinforced with keratin,
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the same material that forms a rhinoceros's horn.
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That makes them strong while keeping weight down to a minimum.
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A hedgehog has over 5,000 spines
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and their main purpose is indeed protection.
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But hedgehogs don't start life with a coat of armour.
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It would be painful for a hedgehog mother
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to give birth to spiny babies.
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But nature has dealt with that problem.
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Tiny hoglets are born with their spines covered by a layer of skin.
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Within a few hours, the thin quills break through.
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A baby hedgehog's first spines are soft and white
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but these soon fall out and are replaced by darker and harder ones.
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Hedgehog spines are shed and regrown at various stages in their lives,
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just like the hair of mammals.
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Surprisingly, a spiny armour is not common in the animal kingdom.
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In Europe, the hedgehog is the only one of its kind.
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But in other parts of the world, there are creatures that have
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evolved a similar spiky coat.
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This is an African crested porcupine.
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It's got a formidable coat of spines but it's no relative
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of the hedgehog and the spines are in fact very different.
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For one thing, they are very much longer.
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Normally, they lie flat against the body but if the animal is irritated,
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it directs them to give a very spectacular warning.
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Even the most ferocious predator will take care
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when approaching a porcupine.
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The quills will break off easily and become lodged in the skin.
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The lion's only chance is to attack from the front.
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As they circle, the porcupine twists and turns
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to keep its armoured back to them.
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This time, the lion got too close.
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It has no way of removing the spike and may be unable to feed.
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It could prove fatal for the predator.
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Although the porcupine's quills may appear thin, even flimsy,
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once they get stuck in your flesh, they are remarkably difficult
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and painful to remove.
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Why this should be was not known until recently.
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But when looked at under an electron microscope, you can see
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that each quill is coated with tiny backwards facing barbs.
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00:17:46,320 --> 00:17:49,240
The barbs act like the teeth on a serrated knife,
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making it easier to penetrate the skin,
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00:17:51,720 --> 00:17:54,280
but when it comes to removing the quills,
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the barbs have the opposite effect and act as anchors,
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preventing the spine from sliding out of the wound.
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00:18:03,880 --> 00:18:09,920
The porcupine's spiky coat seems more formidable than the hedgehog's.
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But the hedgehog has a very effective way of protecting
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its vulnerable underbelly.
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It rolls itself into a ball, so that it is completely encased in spines.
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00:18:26,120 --> 00:18:30,840
Foxes do attack hedgehogs but a fox must wait until the animal
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00:18:30,840 --> 00:18:34,320
is on the move if it is to get at its unprotected underside.
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If the hedgehog stays rolled in a defensive ball,
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the fox can't harm it.
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All the hedgehog has to do is to sit it out until the fox loses interest.
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But if spines are such an effective defence,
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why don't many other animals adopt them?
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The answer seems to be connected with the difficulties
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of life with spines.
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Spines may be something of a hindrance when it comes to mating.
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00:19:19,800 --> 00:19:23,480
Indeed, early naturalists thought that the hedgehogs must mate
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belly to belly to avoid being impaled on each other's spines.
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We now know that that's not the case.
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The spines seem to do nothing
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to hinder the ardour of a male hedgehog.
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If she is willing, he tries to oblige.
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But it still looks like a tricky and uncomfortable operation.
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Despite the limitations of a spiny coat,
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hedgehogs have remained largely unchanged
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for almost 15 million years.
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00:20:03,200 --> 00:20:06,840
New evidence suggests that the spines may play another
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rather surprising role in their lives.
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00:20:12,840 --> 00:20:16,680
Hedgehogs, when encountering an unfamiliar or toxic object,
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sometimes behave in a very strange way.
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00:20:21,040 --> 00:20:25,800
They will lick and bite it until they start to foam at the mouth.
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The froth is then transferred to their spines.
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00:20:30,920 --> 00:20:34,200
We still don't fully understand this strange behaviour.
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00:20:35,680 --> 00:20:39,160
It may help to camouflage the hedgehog's smell,
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00:20:39,160 --> 00:20:42,800
or make the spiny coat more distasteful to predators.
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00:20:46,040 --> 00:20:50,400
Or maybe it helps hedgehogs communicate with each other.
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00:20:50,400 --> 00:20:53,200
Or make them more attractive to the opposite sex.
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We might one day discover its true purpose but we haven't yet.
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00:21:05,840 --> 00:21:10,040
Our familiar British hedgehog has provoked some very strange
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00:21:10,040 --> 00:21:13,360
and far-fetched ideas, but, for many of us,
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it remains one of the most engaging animals in the British countryside,
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00:21:17,960 --> 00:21:21,800
and its prickly coat makes it that much more attractive.
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00:21:24,040 --> 00:21:28,080
So, it turns out that some of the early ideas about the purpose
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00:21:28,080 --> 00:21:30,840
of the rhino's armour and the hedgehog's spines
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00:21:30,840 --> 00:21:33,800
were only partly correct.
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00:21:33,800 --> 00:21:38,080
Their true functions are far more complex than we yet realise.
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00:21:46,440 --> 00:21:50,320
CUCKOO CALLS
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The call of the cuckoo has long been regarded as a sign of spring.
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00:21:55,080 --> 00:21:59,640
But, in fact, it's the call of a killer and a cheat.
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00:21:59,640 --> 00:22:03,880
The cuckoo lays its egg in the nests of other birds and somehow
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00:22:03,880 --> 00:22:08,520
persuades them to treat it and its chick as if it were their own.
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00:22:08,520 --> 00:22:10,640
How does it get away with it?
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00:22:10,640 --> 00:22:14,120
It's a question that has puzzled people for centuries.
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00:22:15,760 --> 00:22:18,600
In Britain, the cuckoo arrives at a time
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00:22:18,600 --> 00:22:21,920
when most birds are nesting and laying eggs.
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00:22:21,920 --> 00:22:26,240
Early egg collectors noticed that the nests of some birds
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00:22:26,240 --> 00:22:29,160
had a slightly odd-looking egg in them.
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00:22:29,160 --> 00:22:32,640
These are the eggs laid by a number of different birds.
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00:22:32,640 --> 00:22:38,760
A marsh warbler, spotted flycatcher, a linnet and a whitethroat.
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00:22:38,760 --> 00:22:43,360
Amongst each of those clutches, there is a fraudster, a cuckoo egg,
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00:22:43,360 --> 00:22:45,280
which mimics that of its host.
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00:22:48,080 --> 00:22:51,480
Although cuckoos are long known to lay their eggs in the nests
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00:22:51,480 --> 00:22:55,080
of other birds, no-one had actually described it happening.
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00:22:56,720 --> 00:23:00,640
Then, in the 18th century, an English country doctor
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00:23:00,640 --> 00:23:04,320
with an interest in natural history decided to investigate.
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00:23:06,920 --> 00:23:10,960
Edward Jenner lived here in Berkeley, Gloucestershire,
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00:23:10,960 --> 00:23:15,240
and is best known for his work on the smallpox vaccine.
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00:23:15,240 --> 00:23:18,600
In fact, he is said to be the father of vaccination and that
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00:23:18,600 --> 00:23:23,480
his work has saved more human lives than that of any other man.
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00:23:23,480 --> 00:23:28,120
What is less known is that he first achieved scientific distinction
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00:23:28,120 --> 00:23:31,960
by his observations on the behaviour of the cuckoo.
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00:23:35,040 --> 00:23:38,760
At the time, it was believed that a cuckoo removes
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00:23:38,760 --> 00:23:41,560
all of the eggs in a nest and then lays its own.
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00:23:43,160 --> 00:23:46,680
By doing so, it would ensure its own chick gets all the food
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00:23:46,680 --> 00:23:49,640
brought in by the unwitting nest owners.
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00:23:51,720 --> 00:23:55,440
But Edward Jenner's detailed observations were to reveal
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00:23:55,440 --> 00:23:57,320
a rather darker tale.
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00:23:59,600 --> 00:24:03,560
Jenner's work on cuckoos was published in 1788
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00:24:03,560 --> 00:24:07,200
here in the Philosophical Transactions of the Royal Society,
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00:24:07,200 --> 00:24:10,280
the world's first scientific society.
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00:24:10,280 --> 00:24:12,040
It was entitled simply...
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00:24:12,040 --> 00:24:15,200
"Observations on the natural history of the cuckoo"
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00:24:15,200 --> 00:24:17,480
by Mr Edward Jenner.
340
00:24:17,480 --> 00:24:21,000
In it, he reported that it was not the parent cuckoo
341
00:24:21,000 --> 00:24:23,560
but the newly hatched chick which pushes the eggs
342
00:24:23,560 --> 00:24:26,520
and nestlings of the foster parents out of the nest.
343
00:24:27,800 --> 00:24:29,440
As soon as it hatches,
344
00:24:29,440 --> 00:24:34,480
the cuckoo chick's instinct is to kill anything else in the nest.
345
00:24:34,480 --> 00:24:36,280
It's still blind and naked
346
00:24:36,280 --> 00:24:39,160
but it has a cup-shaped depression on its back
347
00:24:39,160 --> 00:24:41,360
into which an egg fits perfectly.
348
00:24:43,720 --> 00:24:49,000
But sometimes the other eggs hatch earlier and Jenner's observations
349
00:24:49,000 --> 00:24:51,960
of how the cuckoo chick deals with its nest mates
350
00:24:51,960 --> 00:24:53,320
were quite shocking.
351
00:24:55,200 --> 00:24:56,440
He writes...
352
00:24:56,440 --> 00:24:59,320
"the moment of accomplishing this was very curious.
353
00:24:59,320 --> 00:25:03,320
"The little animal, with the assistance of its rump and wings,
354
00:25:03,320 --> 00:25:05,680
"contrived to get the bird on its back
355
00:25:05,680 --> 00:25:09,400
"and, making a lodgement of the burden by elevating its elbows,
356
00:25:09,400 --> 00:25:12,120
"clambered backwards with it up the side of the nest
357
00:25:12,120 --> 00:25:15,680
"until it reached the top, where, resting for a moment,
358
00:25:15,680 --> 00:25:18,200
"it threw off its load with a jerk
359
00:25:18,200 --> 00:25:22,400
"and quite disengaged it from the nest."
360
00:25:22,400 --> 00:25:25,600
The real villain had been uncovered.
361
00:25:25,600 --> 00:25:29,920
Jenner's views were met with incredulity and some disbelief,
362
00:25:29,920 --> 00:25:33,440
but nonetheless they earned him the Fellowship of the Royal Society.
363
00:25:33,440 --> 00:25:35,680
It was the greatest honour that could be given to
364
00:25:35,680 --> 00:25:37,080
a scientist at the time.
365
00:25:38,440 --> 00:25:40,800
Jenner's observations had revealed
366
00:25:40,800 --> 00:25:44,280
the true nature of the cuckoo's deception.
367
00:25:44,280 --> 00:25:47,560
But it still wasn't clear why the cuckoos should opt for this
368
00:25:47,560 --> 00:25:50,200
strange way of raising its young.
369
00:25:53,160 --> 00:25:57,560
It wasn't until 100 years later that Charles Darwin finally
370
00:25:57,560 --> 00:26:01,200
provided an explanation with his theory of evolution.
371
00:26:02,280 --> 00:26:04,760
The cuckoo's behaviour has evolved
372
00:26:04,760 --> 00:26:07,440
to increase its own breeding success.
373
00:26:07,440 --> 00:26:09,880
By avoiding the task of raising chicks,
374
00:26:09,880 --> 00:26:13,880
the cuckoo can lay more eggs than any other bird,
375
00:26:13,880 --> 00:26:16,560
as many as 25 in a season.
376
00:26:19,400 --> 00:26:22,040
While it makes evolutionary sense for the cuckoo
377
00:26:22,040 --> 00:26:25,680
to lay its eggs in the nests of others, what about its victims?
378
00:26:25,680 --> 00:26:28,720
Why do they put up with this trickery?
379
00:26:28,720 --> 00:26:31,680
It seems that they sometimes don't.
380
00:26:32,680 --> 00:26:36,840
This was revealed in an early natural history film in 1920.
381
00:26:38,080 --> 00:26:42,120
The Cuckoo's Secret was made by Edgar Chance and Oliver Pike,
382
00:26:42,120 --> 00:26:46,120
an egg collector and a wildlife film maker.
383
00:26:46,120 --> 00:26:49,080
Chance was fascinated by cuckoos
384
00:26:49,080 --> 00:26:51,840
and spent a great deal of time following them.
385
00:26:51,840 --> 00:26:55,960
He was the first person known to see a cuckoo lay its egg.
386
00:26:57,840 --> 00:27:02,080
The deception involves stealth and speed.
387
00:27:02,080 --> 00:27:06,760
The female waits until a nest is unattended and then she strikes.
388
00:27:06,760 --> 00:27:09,720
But if she is spotted, the owners fight back.
389
00:27:10,880 --> 00:27:12,440
If she is successful,
390
00:27:12,440 --> 00:27:16,080
the whole deception takes less than ten seconds.
391
00:27:16,080 --> 00:27:20,400
She removes and eats just one egg and replaces it with her own.
392
00:27:25,560 --> 00:27:28,080
The Chance and Pike film solved one mystery,
393
00:27:28,080 --> 00:27:30,000
but there were still others.
394
00:27:31,120 --> 00:27:33,480
How does the cuckoo choose its victim?
395
00:27:34,920 --> 00:27:38,480
And why don't the nest owners reject the alien egg?
396
00:27:47,360 --> 00:27:50,960
Reed warblers are one of the cuckoo's main targets
397
00:27:50,960 --> 00:27:53,920
and the pair has a nest just in here.
398
00:27:58,320 --> 00:28:01,680
The female warbler has laid four speckled eggs,
399
00:28:01,680 --> 00:28:05,240
and, using a model egg, I can illustrate the cuckoo's trickery.
400
00:28:07,240 --> 00:28:10,360
This is the sort of egg that a cuckoo would lay
401
00:28:10,360 --> 00:28:12,400
in the reed warbler's nest.
402
00:28:13,800 --> 00:28:18,920
It matches the reed warbler's actual egg very closely in colour.
403
00:28:20,800 --> 00:28:24,400
Experiments with model eggs have shown that reed warblers
404
00:28:24,400 --> 00:28:27,920
have become very good at recognising an alien egg
405
00:28:27,920 --> 00:28:32,840
and either throw it out or desert their nest to start afresh.
406
00:28:32,840 --> 00:28:36,000
So the cuckoo has to make sure that it produces an egg
407
00:28:36,000 --> 00:28:37,720
that is a very good match.
408
00:28:41,880 --> 00:28:47,120
The cuckoo and its victims are evolving competitively.
409
00:28:47,120 --> 00:28:50,840
With each generation, cuckoos improve their mimicry,
410
00:28:50,840 --> 00:28:54,640
while the nest owners become better at spotting a foreign egg.
411
00:28:56,240 --> 00:28:58,040
While many birds are very good
412
00:28:58,040 --> 00:29:00,760
at detecting a strange egg in their nest,
413
00:29:00,760 --> 00:29:03,080
they seem incapable of recognising
414
00:29:03,080 --> 00:29:05,680
the monstrous cuckoo chick as an impostor.
415
00:29:08,080 --> 00:29:11,560
But the deception is not complete.
416
00:29:11,560 --> 00:29:14,680
The young cuckoo is much larger than the reed warbler chick
417
00:29:14,680 --> 00:29:17,720
so it also needs a lot more food.
418
00:29:17,720 --> 00:29:19,840
How does it get enough?
419
00:29:21,000 --> 00:29:23,480
The cuckoo has a solution.
420
00:29:23,480 --> 00:29:27,600
It now uses vocal deception to trick its foster parents
421
00:29:27,600 --> 00:29:29,880
into providing more food.
422
00:29:31,200 --> 00:29:34,920
This is a sonogram of the sound waves produced by a single
423
00:29:34,920 --> 00:29:37,280
reed warbler chick begging for food.
424
00:29:37,280 --> 00:29:40,600
Below it is the call of a cuckoo chick,
425
00:29:40,600 --> 00:29:43,720
and, as you can see, it looks very different.
426
00:29:43,720 --> 00:29:47,240
In fact, it more closely resembles
427
00:29:47,240 --> 00:29:51,720
the calls of a whole nestful of reed warbler chicks.
428
00:29:53,640 --> 00:29:58,200
So, the cuckoo chick's call is a super stimulus
429
00:29:58,200 --> 00:30:02,360
that sounds like a whole nestful of chicks.
430
00:30:02,360 --> 00:30:04,480
And it appears to work.
431
00:30:06,160 --> 00:30:08,600
The adult birds rush back and forth,
432
00:30:08,600 --> 00:30:11,600
providing the impostor with the same amount of food
433
00:30:11,600 --> 00:30:14,520
as they would for an entire brood of their own.
434
00:30:18,760 --> 00:30:21,280
At three weeks old, the cuckoo chick
435
00:30:21,280 --> 00:30:23,120
has spilled out of the nest.
436
00:30:23,120 --> 00:30:27,160
It's now almost eight times the size of its foster parent.
437
00:30:33,080 --> 00:30:35,360
It was over 200 years ago
438
00:30:35,360 --> 00:30:37,600
that Edward Jenner first shocked us
439
00:30:37,600 --> 00:30:41,440
with his revelation of the cuckoo's extraordinary lifestyle.
440
00:30:43,840 --> 00:30:46,120
Now we know that its unusual behaviour
441
00:30:46,120 --> 00:30:48,840
is due to an extraordinary arms race
442
00:30:48,840 --> 00:30:51,720
that has resulted in one of the most fascinating
443
00:30:51,720 --> 00:30:53,760
specialisations in nature.
444
00:30:59,520 --> 00:31:04,240
The cuckoo's success relies on deceiving just two parent birds.
445
00:31:06,080 --> 00:31:08,480
But our second subject is a moth
446
00:31:08,480 --> 00:31:11,960
that is able to deceive hundreds of bees.
447
00:31:11,960 --> 00:31:13,800
How does it infiltrate
448
00:31:13,800 --> 00:31:16,600
one of the most heavily guarded nests in nature?
449
00:31:19,880 --> 00:31:22,320
This wonderful creature was once
450
00:31:22,320 --> 00:31:25,120
one of the most feared insects in Europe.
451
00:31:25,120 --> 00:31:27,640
It's a death's-head hawkmoth,
452
00:31:27,640 --> 00:31:30,240
and it's easy enough to see how it got its name.
453
00:31:30,240 --> 00:31:32,440
It has this mark on its back
454
00:31:32,440 --> 00:31:35,320
that looks just like a human skull.
455
00:31:35,320 --> 00:31:38,760
This gave it a bad reputation that lasted for centuries,
456
00:31:38,760 --> 00:31:42,600
but now there are new ideas about this moth's strange appearance
457
00:31:42,600 --> 00:31:46,040
that may help explain its extraordinary ability
458
00:31:46,040 --> 00:31:48,800
to rob hives without being stung.
459
00:31:52,560 --> 00:31:55,240
Death's-head hawkmoths are a rare sight Britain,
460
00:31:55,240 --> 00:31:58,320
for they spend most of their lives in Africa and Asia.
461
00:32:00,400 --> 00:32:02,960
But every summer a small number of migrants
462
00:32:02,960 --> 00:32:04,800
arrive in northern Europe,
463
00:32:04,800 --> 00:32:08,040
and, if the weather is warm enough, they breed.
464
00:32:10,720 --> 00:32:14,080
Their caterpillars, unlike the drab adult moths,
465
00:32:14,080 --> 00:32:15,880
are beautifully coloured.
466
00:32:18,520 --> 00:32:20,240
After feeding for several weeks
467
00:32:20,240 --> 00:32:22,920
they can grow to a length of 13 centimetres.
468
00:32:25,680 --> 00:32:29,640
Once ready to become adults, they pupate in the soil
469
00:32:29,640 --> 00:32:33,760
and emerge as the sinister, strangely patterned moths.
470
00:32:38,520 --> 00:32:40,120
In the early 19th century,
471
00:32:40,120 --> 00:32:44,280
a region of northern France was hit by a terrible pestilence,
472
00:32:44,280 --> 00:32:47,280
and, at the same time, a large number of hawkmoths
473
00:32:47,280 --> 00:32:48,640
were seen in the area.
474
00:32:48,640 --> 00:32:53,560
The local people linked the deaths to these night-flying insects.
475
00:32:53,560 --> 00:32:57,960
But there was another even more disturbing side to this moth.
476
00:32:57,960 --> 00:33:00,200
It could make an unusual noise.
477
00:33:01,720 --> 00:33:03,040
SQUEAKING
478
00:33:03,040 --> 00:33:04,200
There.
479
00:33:04,200 --> 00:33:05,920
A strange squeak.
480
00:33:05,920 --> 00:33:09,000
And that only added to its chilling reputation.
481
00:33:13,320 --> 00:33:15,760
Moths don't usually squeak.
482
00:33:17,720 --> 00:33:21,240
Tiger moths sometimes produce ultrasonic warning clicks
483
00:33:21,240 --> 00:33:25,040
that tell bats that they're poisonous and not good to eat,
484
00:33:25,040 --> 00:33:27,640
but this is not a noise we can generally hear.
485
00:33:29,200 --> 00:33:31,600
Perhaps the death's-head hawkmoth squeaks
486
00:33:31,600 --> 00:33:33,480
to scare predators like birds.
487
00:33:35,080 --> 00:33:37,680
However, other large migratory moths
488
00:33:37,680 --> 00:33:39,520
don't make such a sound.
489
00:33:41,360 --> 00:33:43,920
This makes the death's-head hawkmoth's squeak
490
00:33:43,920 --> 00:33:45,560
all the more surprising,
491
00:33:45,560 --> 00:33:48,360
and it has intrigued people for centuries.
492
00:33:50,400 --> 00:33:53,920
These moths are more than 200 years old.
493
00:33:53,920 --> 00:33:57,760
We know that because the handwritten label there tells us
494
00:33:57,760 --> 00:34:02,640
they were collected in 1801 by a Robert Darling Willis,
495
00:34:02,640 --> 00:34:06,440
the personal physician to King George III.
496
00:34:06,440 --> 00:34:08,520
George III is well-known as the king
497
00:34:08,520 --> 00:34:10,600
who suffered from bouts of madness,
498
00:34:10,600 --> 00:34:13,400
and, on a visit to see the king during one of them,
499
00:34:13,400 --> 00:34:17,840
Dr Willis discovered these large moths in the monarch's bedchamber.
500
00:34:18,920 --> 00:34:22,600
Unable to identify them, the doctor sent them to his grandson,
501
00:34:22,600 --> 00:34:24,360
who was at that time superintendent
502
00:34:24,360 --> 00:34:26,880
at the Museum of Zoology in Cambridge.
503
00:34:26,880 --> 00:34:30,760
He confirmed that they were death's-head hawkmoths,
504
00:34:30,760 --> 00:34:33,160
and, unusually for an insect,
505
00:34:33,160 --> 00:34:35,800
this moth produces a loud call
506
00:34:35,800 --> 00:34:38,560
that has been likened to the mournful cry
507
00:34:38,560 --> 00:34:40,680
of a grief-stricken child.
508
00:34:41,800 --> 00:34:45,320
Did the disturbed king hear the plaintive calls of a hawkmoth?
509
00:34:45,320 --> 00:34:47,080
That we don't know.
510
00:34:47,080 --> 00:34:50,400
But certainly many of the ordinary people of the 19th century
511
00:34:50,400 --> 00:34:54,080
were struck with a sense of terror whenever this moth appeared.
512
00:34:56,600 --> 00:35:00,560
The moths' unusual appearance and strange behaviour baffled people.
513
00:35:02,080 --> 00:35:05,600
But, in nature, such traits usually have a purpose.
514
00:35:06,600 --> 00:35:09,080
And it may be for the death's-head hawkmoth
515
00:35:09,080 --> 00:35:13,160
that they enable it to break into beehives and steal their honey.
516
00:35:15,560 --> 00:35:18,960
These are the giant honey bees of south-east Asia,
517
00:35:18,960 --> 00:35:22,560
and they form some of the largest bee colonies in the world.
518
00:35:24,480 --> 00:35:27,560
I once got up close to one in order to demonstrate
519
00:35:27,560 --> 00:35:30,120
their response to a predator.
520
00:35:30,120 --> 00:35:32,640
I had a model of a large hornet,
521
00:35:32,640 --> 00:35:35,080
which produced a kind of Mexican wave,
522
00:35:35,080 --> 00:35:38,360
and that makes it very difficult for an aggressor to land.
523
00:35:38,360 --> 00:35:40,920
BUZZING
524
00:35:40,920 --> 00:35:44,000
This covering of bees looks impossible to penetrate.
525
00:35:47,520 --> 00:35:48,880
But at night
526
00:35:48,880 --> 00:35:51,400
a thief can break through their ranks.
527
00:35:51,400 --> 00:35:55,000
A death's-head hawkmoth lands on the carpet of bees
528
00:35:55,000 --> 00:35:58,120
and pushes its way through without being attacked.
529
00:35:59,440 --> 00:36:02,240
In just a few seconds, it takes some sips of honey
530
00:36:02,240 --> 00:36:03,720
and emerges unharmed.
531
00:36:05,080 --> 00:36:07,920
Getting past the guard bees is quite a feat,
532
00:36:07,920 --> 00:36:11,320
but surviving inside is even more astounding.
533
00:36:16,640 --> 00:36:20,040
Death's-head hawkmoths raid domestic beehives too,
534
00:36:20,040 --> 00:36:21,760
and can be quite a pest.
535
00:36:28,320 --> 00:36:32,920
Somehow, the moth slips past the guards and, as if invisible,
536
00:36:32,920 --> 00:36:36,400
walks through the hive, heading straight for the honeycomb.
537
00:36:38,760 --> 00:36:40,760
It then feeds unnoticed.
538
00:36:42,360 --> 00:36:43,840
How does it do this?
539
00:36:46,800 --> 00:36:49,960
One theory proposes that its spooky appearance
540
00:36:49,960 --> 00:36:51,880
may help it avoid being attacked.
541
00:36:51,880 --> 00:36:54,360
BUZZING
542
00:36:54,360 --> 00:36:56,760
Miriam Rothschild, a great entomologist
543
00:36:56,760 --> 00:36:59,040
and expert on fleas and butterflies,
544
00:36:59,040 --> 00:37:01,880
suggested that the moth's skull pattern looks like
545
00:37:01,880 --> 00:37:03,520
the head of a worker bee,
546
00:37:03,520 --> 00:37:07,000
and that this could play a role in the moth's deception.
547
00:37:07,000 --> 00:37:09,440
Well, this is a photograph
548
00:37:09,440 --> 00:37:12,920
of a worker bee face taken through a microscope.
549
00:37:12,920 --> 00:37:16,280
Let's see how it looks next to a close-up photo
550
00:37:16,280 --> 00:37:18,160
of the skull pattern of the moth.
551
00:37:21,080 --> 00:37:22,280
There.
552
00:37:22,280 --> 00:37:25,240
Well, I suppose there's a slight resemblance,
553
00:37:25,240 --> 00:37:28,760
but given the fact that most moths raid beehives and nests
554
00:37:28,760 --> 00:37:31,480
during the night, it's unlikely the bees
555
00:37:31,480 --> 00:37:33,600
could see that much detail.
556
00:37:33,600 --> 00:37:37,840
The most likely answer lies in the scent the moth gives off.
557
00:37:40,440 --> 00:37:42,560
In America in the 1950s,
558
00:37:42,560 --> 00:37:45,480
a German entomologist called Thomas Eisner
559
00:37:45,480 --> 00:37:48,600
studied chemical ecology - in particular,
560
00:37:48,600 --> 00:37:50,920
the chemical defences of insects.
561
00:37:53,360 --> 00:37:57,240
Most famously, he illustrated how bombardier beetles
562
00:37:57,240 --> 00:37:59,480
fire hot acid onto a predator.
563
00:38:03,320 --> 00:38:05,280
He also studied moths,
564
00:38:05,280 --> 00:38:08,520
and showed that the feathery projections on their abdomens
565
00:38:08,520 --> 00:38:12,200
and their large antennae were used to produce and pick up scent.
566
00:38:13,640 --> 00:38:17,560
It seemed that many insects were using scent in surprising ways.
567
00:38:19,400 --> 00:38:22,480
Tests on the chemical scents produced by hawkmoths
568
00:38:22,480 --> 00:38:26,120
reveal a remarkable similarity to those produced by the worker bees
569
00:38:26,120 --> 00:38:28,160
in the hives that they raid.
570
00:38:28,160 --> 00:38:30,240
Their scent is not identical,
571
00:38:30,240 --> 00:38:32,080
but it contains several key chemicals
572
00:38:32,080 --> 00:38:34,840
that exactly match those produced by bees.
573
00:38:37,720 --> 00:38:40,440
So the death's-head hawkmoth's scent
574
00:38:40,440 --> 00:38:43,040
acts as an invisibility cloak
575
00:38:43,040 --> 00:38:46,360
that makes it undetectable to the worker bees in the nest.
576
00:38:51,240 --> 00:38:53,120
With thick scales on its body,
577
00:38:53,120 --> 00:38:55,240
clawed feet that grip the honeycomb,
578
00:38:55,240 --> 00:38:58,840
and a short, pointed proboscis to pierce the honey cells,
579
00:38:58,840 --> 00:39:02,120
the moth has evolved into an effective hive robber.
580
00:39:05,200 --> 00:39:08,440
But there is another, even more impressive impostor
581
00:39:08,440 --> 00:39:11,160
that can also penetrate the protective defences
582
00:39:11,160 --> 00:39:13,200
of an insect colony.
583
00:39:13,200 --> 00:39:16,200
Its victims are not bees but ants.
584
00:39:18,480 --> 00:39:21,320
The impostor that invades this ant nest
585
00:39:21,320 --> 00:39:23,760
doesn't get in there by flying.
586
00:39:23,760 --> 00:39:25,800
Nothing as blatant as that.
587
00:39:25,800 --> 00:39:29,680
Instead, the caterpillars of some species of blue butterfly,
588
00:39:29,680 --> 00:39:34,080
like this one, wait for red ants to collect them.
589
00:39:34,080 --> 00:39:37,320
Remarkably, passing ants don't kill them.
590
00:39:37,320 --> 00:39:40,600
They pick them up and take them back into their nest.
591
00:39:40,600 --> 00:39:44,120
The cuckoo caterpillar will stay inside the nest
592
00:39:44,120 --> 00:39:46,200
for up to ten months.
593
00:39:46,200 --> 00:39:48,280
Just like the death's-head hawkmoths,
594
00:39:48,280 --> 00:39:51,920
it produces a chemical scent that deceives the ants.
595
00:39:54,000 --> 00:39:58,080
This pink caterpillar, which belongs to the alcon blue butterfly,
596
00:39:58,080 --> 00:40:00,640
has been collected because, to them,
597
00:40:00,640 --> 00:40:04,080
it smells just like the young of their own nest.
598
00:40:04,080 --> 00:40:07,840
They become controlled by the impostor's intoxicating scent,
599
00:40:07,840 --> 00:40:10,960
and feed the butterfly larva even more regularly
600
00:40:10,960 --> 00:40:12,400
than they do their own.
601
00:40:14,880 --> 00:40:18,320
There's another way this impostor pulls off its deceptive trick.
602
00:40:18,320 --> 00:40:20,400
When it's inside the nest,
603
00:40:20,400 --> 00:40:24,080
the butterfly larva makes a strange chattering noise.
604
00:40:24,080 --> 00:40:25,800
To our ears, it's very faint,
605
00:40:25,800 --> 00:40:28,680
but it's clear enough to other insects. This is it.
606
00:40:30,480 --> 00:40:32,320
CHATTERING NOISE
607
00:40:32,320 --> 00:40:36,080
And this is the sound that's made by a queen ant.
608
00:40:38,880 --> 00:40:41,320
SIMILAR CHATTERING NOISE
609
00:40:43,400 --> 00:40:46,640
To worker ants, these calls are very similar,
610
00:40:46,640 --> 00:40:49,640
and they react by treating the butterfly larva
611
00:40:49,640 --> 00:40:51,200
as if it's one of their own.
612
00:40:53,280 --> 00:40:57,640
Caterpillars of the blue butterfly are impressive impostors.
613
00:40:57,640 --> 00:41:00,280
Not only do they mimic the scent of the ants,
614
00:41:00,280 --> 00:41:03,360
but their queen's calls too.
615
00:41:03,360 --> 00:41:06,720
This seems to trump the death's-head hawkmoth's ability
616
00:41:06,720 --> 00:41:08,160
as a nest invader.
617
00:41:11,320 --> 00:41:15,480
But the hawkmoth may also be using sound to trick its victims.
618
00:41:18,480 --> 00:41:22,040
Remember the eerie squeak that was thought to be so frightening?
619
00:41:23,440 --> 00:41:24,840
SQUEAKING
620
00:41:24,840 --> 00:41:26,480
There.
621
00:41:26,480 --> 00:41:29,680
The hawkmoth makes this sound inside the beehive
622
00:41:29,680 --> 00:41:31,840
when it enters to steal honey.
623
00:41:31,840 --> 00:41:35,200
It's been suggested that this might calm the bees,
624
00:41:35,200 --> 00:41:38,360
because the squeak is thought to sound like the piping call
625
00:41:38,360 --> 00:41:41,360
that the queen honey bee makes to pacify her workers.
626
00:41:43,320 --> 00:41:46,000
We can't be sure if the call and the strange skull marking
627
00:41:46,000 --> 00:41:49,320
evolved to deceive bees, but we can be certain
628
00:41:49,320 --> 00:41:52,680
that the death's-head hawkmoth's life as an impostor
629
00:41:52,680 --> 00:41:55,600
is more curious than the superstitions
630
00:41:55,600 --> 00:41:58,600
that have surrounded it for hundreds of years.
631
00:42:00,720 --> 00:42:04,440
The cuckoo and the hawkmoth are both audacious impostors,
632
00:42:04,440 --> 00:42:08,400
but the cuckoo's ability to make its victim raise its young
633
00:42:08,400 --> 00:42:11,480
is perhaps the most accomplished deception of all.
54143
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