Curious Cures David Attenborough's Natural Curiosities


Curious Cures

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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

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myth 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 particularly fascinating.

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Some animals have intriguing ways of protecting their skin.

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The hippopotamus lives in Africa under the hot tropical sun,

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yet doesn't get sunburnt.

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And capuchin monkeys live in insect-infested jungles

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but hardly ever get bitten.

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How do these animals beat the elements

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and protect themselves from sun, parasites and disease?

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Hippos are large land mammals that can weigh up to three tonnes

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and they need to keep their huge bodies cool

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and protected from the sun.

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To avoid the heat, they spend much of the day swimming,

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as they are doing now in the waters behind me.

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But, when they're on land,

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strangely, they don't appear to get sunburnt.

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The secret of their sun tolerance lies within their skin.

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It can sometimes appear shiny and greasy.

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It has unique properties that shocked the early explorers

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and now excites modern scientists.

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Hippos live in Africa south of the Sahara,

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where temperatures can reach 40 degrees Centigrade.

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But they spend much of the day submerged in rivers,

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lakes and swamps, and so avoid the worst of the sun's rays.

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They possess formidable teeth

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but they are, in fact, herbivores

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and eat mostly grass, great quantities of it.

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And they graze mostly at night.

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Even so, continually moving in and out of water

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together with being roasted by the rays of the sun

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could be very damaging to their skin.

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But, curiously, hippos remain healthy.

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Throughout history,

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the hippopotamus has been the subject of many strange tales.

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The Greeks claimed they sweated blood,

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and the Romans said they deliberately pierced their skin

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on sharp rushes to release blood.

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It seemed bizarre that an animal would make itself bleed on purpose.

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In the 19th century, one special hippopotamus

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allowed people to get a closer look at these strange skin secretions.

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In 1849, the British Consul for Egypt, Charles Augustus Murray,

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formally requested that the Pasha of Egypt help capture a hippo

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for the Zoological Society Of London.

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Hunters searched the reeds on a remote island called Obaysch,

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2,000 kilometres up the Nile from Cairo.

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They discovered a male hippo that was only a few days old.

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When they tried to grab it, a strange thing happened.

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Murray describes how a slimy exudation lavishly poured forth

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from the innumerable pores in the skin,

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rendering it so slippery that the animal was impossible to hold.

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The hunters dropped the baby hippo back

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into the waters of the Nile

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but they managed to retrieve it again using the hook of a spear.

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The prize hippo was named Obaysch after the island of its capture,

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and here he is.

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Before his capture, young Obaysch lived with his mother.

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She had moved away from the herd to give birth alone,

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and she protected him from lions and crocodiles.

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Whether Obaysch became accidentally separated from his mother,

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we will never know, but we do know that secretions from his skin

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made him so slippery that he very nearly escaped capture.

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At this time, very little was known about hippos

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and many people believed that they were some kind of horse

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that had taken to living in rivers.

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In the early 20th century,

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naturalists decided that they were closely related to pigs.

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DNA evidence, however, now shows that, in fact,

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their ancestors were cetaceans,

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the group that contains whales and dolphins.

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So, hippos still retain many adaptations for a life in water.

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Hippos are very heavy animals

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but, for most of their time, their bodies are supported by water.

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They are not really very good swimmers.

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In the water, they move by bounding across the bottom.

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They are well adapted to a semi-aquatic life

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because their ears, their eyes and their nostrils

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are all towards the top of their head

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which enables them to lie almost totally submerged

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and yet still keep notice of what's going on on land.

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But their skin is almost entirely hairless

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so, on land, it has to be kept moist.

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In order to prevent young Obaysch from sunburn and drying out,

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the Egyptian pasha had a boat built with a bathing pool

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to transport Obaysch in comfort all the way down the River Nile.

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Accompanied by several cows to supply him with milk,

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he arrived safely in Cairo four months later.

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On receiving Obaysch,

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the British Consul wrote excitedly to the Zoological Society Of London,

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confirming that the hippo was alive, and as tame and playful as a puppy.

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But his travels were not yet over.

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In the spring of 1850, Obaysch was taken to Alexandria

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to board a P&O steamship called the Ripon.

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A special hippo house with a water tank was built on the deck

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and, in May, Obaysch arrived safely in Southampton.

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With the help of block and tackle,

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he was loaded onto a train bound for London.

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And, at ten o'clock at night,

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the tired hippo and his keeper reached London Zoo.

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His home was a newly constructed enclosure

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complete with a heated swimming pool.

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After many hours of travelling,

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the hippo gratefully plunged into the water.

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Obaysch, the hippo sensation, had arrived.

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A journey of over 5,000 miles by sailboat,

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steamboat and a train brought a hippo to England,

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the first one since Roman times.

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Now Europeans had a chance to get close to this unusual creature

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and, perhaps, learn more about its strange skin secretions.

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Later, more hippos arrived at other zoos

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and the blood-red sweat was seen again.

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In the cooler climate of Europe, hippos don't sweat very much.

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But zookeepers have reported that sometimes, in the morning,

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they see red trickles forming on the flanks of these animals.

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It comes from particularly large pores

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which form streaks on the animal's side

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which does look a little like blood.

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We've known for some time that this is a moisturiser

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but why it's red has only just been discovered.

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A little more?

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Come on!

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There we go.

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Recently, Japanese scientists were intrigued to see photos

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of a wild baby hippo with light pink skin

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that still didn't burn under the harsh African sun.

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They wondered if the red secretion played a role

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in protecting its pale skin.

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So they collected hippo secretion from captive hippos

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to look at its composition.

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They discovered two pigments,

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a red one that they named hipposudoric acid,

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and an orange one that they called norhipposudoric acid.

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The red pigment was found to absorb harmful wavelengths of light,

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and both pigments were antibacterial.

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Here was the answer to why hippos never got sunburnt

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and why the wounds of battling males rarely became infected.

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The mysterious slime was neither blood nor sweat

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but a specialised secretion that turns red in sunlight

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and protects the hippo's skin.

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So, what became of Obaysch, the first-ever hippo in captivity

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that gave us a close-up view of these curious creatures?

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For several years, he was a sensation at London Zoo.

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He even inspired the hippo polka, a popular dance of its time.

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The visitors grew weary of him.

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Some were disappointed not to see a giant river horse.

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And others expected a ferocious beast, not a gentle giant.

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Obaysch died in 1878 at the age of 28,

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and he and others that followed taught us some intriguing things

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about hippos, including the reason for the blood-red droplets

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found on their skin.

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So, hippos can produce their very own natural sun cream

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that is waterproof, moisturising and antibacterial.

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Next, we meet another animal that has its own natural cure.

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Capuchin monkeys have a surprising way of protecting their skin

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from stings and bites.

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When early explorers reached the Americas in the 15th century,

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they encountered small monkeys with patches of

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dark brown fur on their heads that resembled hoods.

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So they named them after a group

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of Franciscan friars called Capuchin monks.

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Capuchin monkeys quickly charmed their way into our hearts.

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With dextrous hands and inquisitive personalities,

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they seemed very humanlike.

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They were also adept at learning tricks

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and soon became popular performers on our streets.

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In the past, we used to teach monkeys how to do things,

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how to perform tricks.

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But things are different today.

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Today, monkeys are teaching us things.

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Watch what happens when I give them a few spring onions

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and some chilli peppers.

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They're clearly not eating what I offered them,

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they're rubbing themselves with the peppers and the onions.

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You might think that's because they're captive monkeys

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and they are just doing that to entertain themselves.

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But not so.

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I've seen capuchins do just that in the wild.

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These white-faced capuchins in Costa Rica

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reacted in much the same way when they came across

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a particular rainforest plant, the piper plant.

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These leaves have a distinctive liquorice scent

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and they're hard to come by.

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So, when they do find them,

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the monkeys pass the leaves around the troop

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so everyone can have a share.

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Both in the wild and in captivity,

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capuchin monkeys become similarly excited

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at the sight of lemons or limes

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and again the same frenzied activity and fur rubbing follows.

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What is it about these plants that gets the monkeys so excited?

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We know they all give off a pungent smell,

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so could this be what the capuchins are after?

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Smell plays an important part in the lives of many primates

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but none more so than in the lives of these lovely ring-tailed lemurs.

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They use it both to establish their position within the troop,

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and also the boundaries, the frontiers of their territory.

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If you look at the inside of their forearms,

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there is a black patch without fur

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and there the skin is loaded with glands that produce

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a very strong smell.

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And when these boys go into battle... Whoops!

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When they go into battle,

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they draw their furry tail through their forearms,

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loading it with scent from those glands,

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and then they would wave it over their backs

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in the direction of their enemies in a kind of stink fight.

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You understand that, don't you?

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LEMURS SQUEAK

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Oh!

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The pungent scent is also used by males during the mating season.

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This male has rubbed his own distinctive smell onto his tail

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and he now wafts it towards a female to signal his intentions.

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But she is not entirely convinced.

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Unlike lemurs, capuchins don't have scent glands,

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so some thought that they could be using the smell of certain plants

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for communication.

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But it turns out that they have a different perfume for that job -

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urine, which they apply lavishly to their fur.

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So why then do they also anoint themselves with other smells?

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The answer may be found in our own history.

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The early Romans noticed some 2,000 years ago

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that the fruits and leaves of the lemon plant

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have an exceptionally strong scent

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that can be used to ward off insects.

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A further clue as to why capuchins might cover themselves

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in such pungent smells comes from this plant, the piper plant.

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Throughout the Amazon, Indian tribes apply it as an antiseptic on wounds.

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And in Costa Rica it's used as an insect repellent.

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Could it be that capuchin monkeys protect themselves

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against the onslaught of mosquitoes in much the same way as humans do

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by rubbing themselves with mosquito repellent?

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In 1993, scientists at Oxford University

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decided to put the question to the test.

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They collected some feather lice

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and put them into Petri dishes overnight.

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Into one dish, they also placed a slice of lime.

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The next day, the lice without the lime were mostly alive.

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Whilst in the other dish, two-thirds had died

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and the remainder were paralysed.

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Clearly, the lime contains a lethal insecticide.

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Today, we know that citrus fruit peel

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does indeed contain insecticides

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which disrupt the nervous system of many small insects,

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causing them to become uncoordinated and paralysed.

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The leaves of the piper plant are antiseptic and contain substances

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that protect against fungal and bacterial infection.

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And chilli pepper extract is commonly used in households

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and gardens to deter small mammals and insect pests.

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So it seems that the clever monkeys know

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exactly how to make the best use of nature's remedies.

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Recent research has also revealed that capuchins anoint themselves

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far more during the wet season when mosquitoes are more abundant

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and the risk of infection is higher.

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Troops use different plants,

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possibly simply because they have to use what's locally available.

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But there's one substance with insect repellent qualities

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that appeals to primates, including capuchins,

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that comes not from a plant but from an animal.

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An animal like this.

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A giant millipede.

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When attacked or in danger,

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tropical millipedes often produce a powerful defensive secretion.

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And black lemurs have worked out how to use this to their advantage.

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When they find a millipede, they give it a gentle bite to the head

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to make it release its secretion, and then rub this through their fur.

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The toxic fluid has a strong smell and is highly irritating,

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but it protects the lemurs against mosquitoes.

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This pungent secretion has apparently another strange effect.

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It seems to act as a narcotic,

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sending the lemur into a kind of trance.

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Like other drugs, it has powerful side effects.

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We still don't understand how capuchins and lemurs

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select the plants that they use for medicinal purposes.

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These capuchins behind me were born and raised in captivity

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so they've never encountered the plants

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that their parents and ancestors would have used.

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So how did the monkeys know which plants to choose?

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Can they detect particular substances in them?

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Or is it something they learn from others?

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We don't yet know the answers

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but it could be that babies learn by watching the adults

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and that it's passed down the family line.

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It's clearly a great social event with everyone joining in.

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And, afterwards, the entire group appears to be more tightly bonded.

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When Europeans first saw monkeys in the wild,

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they thought that they were imitating what people did

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in some of their behaviours.

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But quite the reverse,

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it now turns out that many of the local people did things

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that the monkeys had taught them, using plants as medicines.

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So it seems clever monkeys have taught us a trick or two.

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So, it's clear that we're not alone in using medicines

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against injuries and infections.

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Both capuchin monkeys and hippos discovered some medical remedies

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long before we did.

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