0:00:03 > 0:00:05'The natural world is full of extraordinary animals
0:00:05 > 0:00:09'with amazing life histories.'
0:00:09 > 0:00:12Yet certain stories are more intriguing than most.
0:00:15 > 0:00:18The mysteries of a butterfly's life cycle,
0:00:18 > 0:00:21or the strange biology of the emperor penguin,
0:00:21 > 0:00:24some of these creatures were surrounded by
0:00:24 > 0:00:28myth and misunderstandings for a very long time.
0:00:29 > 0:00:33And some have only recently revealed their secrets.
0:00:34 > 0:00:37These are the animals that stand out from the crowd,
0:00:37 > 0:00:42the curiosities I find particularly fascinating.
0:00:50 > 0:00:56Some animals have intriguing ways of protecting their skin.
0:00:56 > 0:01:00The hippopotamus lives in Africa under the hot tropical sun,
0:01:00 > 0:01:03yet doesn't get sunburnt.
0:01:03 > 0:01:07And capuchin monkeys live in insect-infested jungles
0:01:07 > 0:01:09but hardly ever get bitten.
0:01:10 > 0:01:12How do these animals beat the elements
0:01:12 > 0:01:16and protect themselves from sun, parasites and disease?
0:01:23 > 0:01:28Hippos are large land mammals that can weigh up to three tonnes
0:01:28 > 0:01:30and they need to keep their huge bodies cool
0:01:30 > 0:01:32and protected from the sun.
0:01:32 > 0:01:35To avoid the heat, they spend much of the day swimming,
0:01:35 > 0:01:39as they are doing now in the waters behind me.
0:01:39 > 0:01:41But, when they're on land,
0:01:41 > 0:01:44strangely, they don't appear to get sunburnt.
0:01:44 > 0:01:48The secret of their sun tolerance lies within their skin.
0:01:48 > 0:01:51It can sometimes appear shiny and greasy.
0:01:51 > 0:01:55It has unique properties that shocked the early explorers
0:01:55 > 0:01:59and now excites modern scientists.
0:02:03 > 0:02:05Hippos live in Africa south of the Sahara,
0:02:05 > 0:02:09where temperatures can reach 40 degrees Centigrade.
0:02:09 > 0:02:12But they spend much of the day submerged in rivers,
0:02:12 > 0:02:17lakes and swamps, and so avoid the worst of the sun's rays.
0:02:21 > 0:02:23They possess formidable teeth
0:02:23 > 0:02:25but they are, in fact, herbivores
0:02:25 > 0:02:29and eat mostly grass, great quantities of it.
0:02:29 > 0:02:31And they graze mostly at night.
0:02:33 > 0:02:36Even so, continually moving in and out of water
0:02:36 > 0:02:39together with being roasted by the rays of the sun
0:02:39 > 0:02:42could be very damaging to their skin.
0:02:43 > 0:02:47But, curiously, hippos remain healthy.
0:02:51 > 0:02:52Throughout history,
0:02:52 > 0:02:57the hippopotamus has been the subject of many strange tales.
0:02:57 > 0:02:59The Greeks claimed they sweated blood,
0:02:59 > 0:03:02and the Romans said they deliberately pierced their skin
0:03:02 > 0:03:05on sharp rushes to release blood.
0:03:05 > 0:03:09It seemed bizarre that an animal would make itself bleed on purpose.
0:03:11 > 0:03:14In the 19th century, one special hippopotamus
0:03:14 > 0:03:19allowed people to get a closer look at these strange skin secretions.
0:03:22 > 0:03:28In 1849, the British Consul for Egypt, Charles Augustus Murray,
0:03:28 > 0:03:33formally requested that the Pasha of Egypt help capture a hippo
0:03:33 > 0:03:36for the Zoological Society Of London.
0:03:36 > 0:03:40Hunters searched the reeds on a remote island called Obaysch,
0:03:40 > 0:03:442,000 kilometres up the Nile from Cairo.
0:03:46 > 0:03:50They discovered a male hippo that was only a few days old.
0:03:51 > 0:03:53When they tried to grab it, a strange thing happened.
0:03:53 > 0:03:59Murray describes how a slimy exudation lavishly poured forth
0:03:59 > 0:04:02from the innumerable pores in the skin,
0:04:02 > 0:04:06rendering it so slippery that the animal was impossible to hold.
0:04:06 > 0:04:09The hunters dropped the baby hippo back
0:04:09 > 0:04:11into the waters of the Nile
0:04:11 > 0:04:15but they managed to retrieve it again using the hook of a spear.
0:04:16 > 0:04:21The prize hippo was named Obaysch after the island of its capture,
0:04:21 > 0:04:22and here he is.
0:04:27 > 0:04:31Before his capture, young Obaysch lived with his mother.
0:04:31 > 0:04:34She had moved away from the herd to give birth alone,
0:04:34 > 0:04:38and she protected him from lions and crocodiles.
0:04:39 > 0:04:42Whether Obaysch became accidentally separated from his mother,
0:04:42 > 0:04:46we will never know, but we do know that secretions from his skin
0:04:46 > 0:04:50made him so slippery that he very nearly escaped capture.
0:04:52 > 0:04:55At this time, very little was known about hippos
0:04:55 > 0:04:58and many people believed that they were some kind of horse
0:04:58 > 0:05:00that had taken to living in rivers.
0:05:02 > 0:05:05In the early 20th century,
0:05:05 > 0:05:09naturalists decided that they were closely related to pigs.
0:05:09 > 0:05:13DNA evidence, however, now shows that, in fact,
0:05:13 > 0:05:15their ancestors were cetaceans,
0:05:15 > 0:05:19the group that contains whales and dolphins.
0:05:21 > 0:05:27So, hippos still retain many adaptations for a life in water.
0:05:31 > 0:05:33Hippos are very heavy animals
0:05:33 > 0:05:37but, for most of their time, their bodies are supported by water.
0:05:37 > 0:05:40They are not really very good swimmers.
0:05:40 > 0:05:44In the water, they move by bounding across the bottom.
0:05:44 > 0:05:47They are well adapted to a semi-aquatic life
0:05:47 > 0:05:50because their ears, their eyes and their nostrils
0:05:50 > 0:05:53are all towards the top of their head
0:05:53 > 0:05:56which enables them to lie almost totally submerged
0:05:56 > 0:06:00and yet still keep notice of what's going on on land.
0:06:00 > 0:06:03But their skin is almost entirely hairless
0:06:03 > 0:06:06so, on land, it has to be kept moist.
0:06:11 > 0:06:15In order to prevent young Obaysch from sunburn and drying out,
0:06:15 > 0:06:20the Egyptian pasha had a boat built with a bathing pool
0:06:20 > 0:06:24to transport Obaysch in comfort all the way down the River Nile.
0:06:25 > 0:06:28Accompanied by several cows to supply him with milk,
0:06:28 > 0:06:32he arrived safely in Cairo four months later.
0:06:34 > 0:06:36On receiving Obaysch,
0:06:36 > 0:06:40the British Consul wrote excitedly to the Zoological Society Of London,
0:06:40 > 0:06:45confirming that the hippo was alive, and as tame and playful as a puppy.
0:06:45 > 0:06:48But his travels were not yet over.
0:06:50 > 0:06:53In the spring of 1850, Obaysch was taken to Alexandria
0:06:53 > 0:06:56to board a P&O steamship called the Ripon.
0:06:56 > 0:07:00A special hippo house with a water tank was built on the deck
0:07:00 > 0:07:05and, in May, Obaysch arrived safely in Southampton.
0:07:05 > 0:07:07With the help of block and tackle,
0:07:07 > 0:07:09he was loaded onto a train bound for London.
0:07:09 > 0:07:12And, at ten o'clock at night,
0:07:12 > 0:07:17the tired hippo and his keeper reached London Zoo.
0:07:17 > 0:07:19His home was a newly constructed enclosure
0:07:19 > 0:07:22complete with a heated swimming pool.
0:07:22 > 0:07:24After many hours of travelling,
0:07:24 > 0:07:27the hippo gratefully plunged into the water.
0:07:27 > 0:07:31Obaysch, the hippo sensation, had arrived.
0:07:35 > 0:07:38A journey of over 5,000 miles by sailboat,
0:07:38 > 0:07:42steamboat and a train brought a hippo to England,
0:07:42 > 0:07:45the first one since Roman times.
0:07:47 > 0:07:52Now Europeans had a chance to get close to this unusual creature
0:07:52 > 0:07:57and, perhaps, learn more about its strange skin secretions.
0:07:57 > 0:08:01Later, more hippos arrived at other zoos
0:08:01 > 0:08:04and the blood-red sweat was seen again.
0:08:05 > 0:08:09In the cooler climate of Europe, hippos don't sweat very much.
0:08:09 > 0:08:12But zookeepers have reported that sometimes, in the morning,
0:08:12 > 0:08:18they see red trickles forming on the flanks of these animals.
0:08:18 > 0:08:21It comes from particularly large pores
0:08:21 > 0:08:24which form streaks on the animal's side
0:08:24 > 0:08:29which does look a little like blood.
0:08:29 > 0:08:34We've known for some time that this is a moisturiser
0:08:34 > 0:08:38but why it's red has only just been discovered.
0:08:39 > 0:08:41A little more?
0:08:41 > 0:08:43Come on!
0:08:43 > 0:08:44There we go.
0:08:45 > 0:08:50Recently, Japanese scientists were intrigued to see photos
0:08:50 > 0:08:52of a wild baby hippo with light pink skin
0:08:52 > 0:08:57that still didn't burn under the harsh African sun.
0:08:57 > 0:09:00They wondered if the red secretion played a role
0:09:00 > 0:09:02in protecting its pale skin.
0:09:02 > 0:09:05So they collected hippo secretion from captive hippos
0:09:05 > 0:09:08to look at its composition.
0:09:08 > 0:09:10They discovered two pigments,
0:09:10 > 0:09:14a red one that they named hipposudoric acid,
0:09:14 > 0:09:19and an orange one that they called norhipposudoric acid.
0:09:20 > 0:09:24The red pigment was found to absorb harmful wavelengths of light,
0:09:24 > 0:09:27and both pigments were antibacterial.
0:09:29 > 0:09:35Here was the answer to why hippos never got sunburnt
0:09:35 > 0:09:38and why the wounds of battling males rarely became infected.
0:09:40 > 0:09:44The mysterious slime was neither blood nor sweat
0:09:44 > 0:09:48but a specialised secretion that turns red in sunlight
0:09:48 > 0:09:50and protects the hippo's skin.
0:09:52 > 0:09:57So, what became of Obaysch, the first-ever hippo in captivity
0:09:57 > 0:10:01that gave us a close-up view of these curious creatures?
0:10:01 > 0:10:05For several years, he was a sensation at London Zoo.
0:10:05 > 0:10:11He even inspired the hippo polka, a popular dance of its time.
0:10:12 > 0:10:14The visitors grew weary of him.
0:10:14 > 0:10:18Some were disappointed not to see a giant river horse.
0:10:18 > 0:10:23And others expected a ferocious beast, not a gentle giant.
0:10:23 > 0:10:27Obaysch died in 1878 at the age of 28,
0:10:27 > 0:10:30and he and others that followed taught us some intriguing things
0:10:30 > 0:10:34about hippos, including the reason for the blood-red droplets
0:10:34 > 0:10:36found on their skin.
0:10:37 > 0:10:41So, hippos can produce their very own natural sun cream
0:10:41 > 0:10:46that is waterproof, moisturising and antibacterial.
0:10:47 > 0:10:52Next, we meet another animal that has its own natural cure.
0:10:54 > 0:10:58Capuchin monkeys have a surprising way of protecting their skin
0:10:58 > 0:11:00from stings and bites.
0:11:04 > 0:11:08When early explorers reached the Americas in the 15th century,
0:11:08 > 0:11:11they encountered small monkeys with patches of
0:11:11 > 0:11:15dark brown fur on their heads that resembled hoods.
0:11:15 > 0:11:17So they named them after a group
0:11:17 > 0:11:21of Franciscan friars called Capuchin monks.
0:11:25 > 0:11:29Capuchin monkeys quickly charmed their way into our hearts.
0:11:29 > 0:11:33With dextrous hands and inquisitive personalities,
0:11:33 > 0:11:35they seemed very humanlike.
0:11:37 > 0:11:40They were also adept at learning tricks
0:11:40 > 0:11:43and soon became popular performers on our streets.
0:11:49 > 0:11:53In the past, we used to teach monkeys how to do things,
0:11:53 > 0:11:56how to perform tricks.
0:11:56 > 0:11:59But things are different today.
0:11:59 > 0:12:03Today, monkeys are teaching us things.
0:12:03 > 0:12:08Watch what happens when I give them a few spring onions
0:12:08 > 0:12:10and some chilli peppers.
0:12:42 > 0:12:44They're clearly not eating what I offered them,
0:12:44 > 0:12:47they're rubbing themselves with the peppers and the onions.
0:12:47 > 0:12:52You might think that's because they're captive monkeys
0:12:52 > 0:12:55and they are just doing that to entertain themselves.
0:12:55 > 0:12:56But not so.
0:12:56 > 0:13:00I've seen capuchins do just that in the wild.
0:13:15 > 0:13:18These white-faced capuchins in Costa Rica
0:13:18 > 0:13:21reacted in much the same way when they came across
0:13:21 > 0:13:25a particular rainforest plant, the piper plant.
0:13:28 > 0:13:31These leaves have a distinctive liquorice scent
0:13:31 > 0:13:33and they're hard to come by.
0:13:33 > 0:13:34So, when they do find them,
0:13:34 > 0:13:37the monkeys pass the leaves around the troop
0:13:37 > 0:13:39so everyone can have a share.
0:13:43 > 0:13:46Both in the wild and in captivity,
0:13:46 > 0:13:49capuchin monkeys become similarly excited
0:13:49 > 0:13:51at the sight of lemons or limes
0:13:51 > 0:13:57and again the same frenzied activity and fur rubbing follows.
0:14:01 > 0:14:05What is it about these plants that gets the monkeys so excited?
0:14:08 > 0:14:12We know they all give off a pungent smell,
0:14:12 > 0:14:14so could this be what the capuchins are after?
0:14:18 > 0:14:22Smell plays an important part in the lives of many primates
0:14:22 > 0:14:27but none more so than in the lives of these lovely ring-tailed lemurs.
0:14:27 > 0:14:32They use it both to establish their position within the troop,
0:14:32 > 0:14:36and also the boundaries, the frontiers of their territory.
0:14:36 > 0:14:38If you look at the inside of their forearms,
0:14:38 > 0:14:41there is a black patch without fur
0:14:41 > 0:14:44and there the skin is loaded with glands that produce
0:14:44 > 0:14:47a very strong smell.
0:14:47 > 0:14:50And when these boys go into battle... Whoops!
0:14:50 > 0:14:52When they go into battle,
0:14:52 > 0:14:55they draw their furry tail through their forearms,
0:14:55 > 0:14:58loading it with scent from those glands,
0:14:58 > 0:15:01and then they would wave it over their backs
0:15:01 > 0:15:05in the direction of their enemies in a kind of stink fight.
0:15:06 > 0:15:08You understand that, don't you?
0:15:08 > 0:15:09LEMURS SQUEAK
0:15:09 > 0:15:10Oh!
0:15:14 > 0:15:19The pungent scent is also used by males during the mating season.
0:15:19 > 0:15:23This male has rubbed his own distinctive smell onto his tail
0:15:23 > 0:15:28and he now wafts it towards a female to signal his intentions.
0:15:31 > 0:15:34But she is not entirely convinced.
0:15:36 > 0:15:40Unlike lemurs, capuchins don't have scent glands,
0:15:40 > 0:15:44so some thought that they could be using the smell of certain plants
0:15:44 > 0:15:46for communication.
0:15:46 > 0:15:52But it turns out that they have a different perfume for that job -
0:15:52 > 0:15:57urine, which they apply lavishly to their fur.
0:15:57 > 0:16:02So why then do they also anoint themselves with other smells?
0:16:02 > 0:16:06The answer may be found in our own history.
0:16:06 > 0:16:10The early Romans noticed some 2,000 years ago
0:16:10 > 0:16:13that the fruits and leaves of the lemon plant
0:16:13 > 0:16:16have an exceptionally strong scent
0:16:16 > 0:16:18that can be used to ward off insects.
0:16:20 > 0:16:23A further clue as to why capuchins might cover themselves
0:16:23 > 0:16:29in such pungent smells comes from this plant, the piper plant.
0:16:29 > 0:16:35Throughout the Amazon, Indian tribes apply it as an antiseptic on wounds.
0:16:35 > 0:16:40And in Costa Rica it's used as an insect repellent.
0:16:40 > 0:16:43Could it be that capuchin monkeys protect themselves
0:16:43 > 0:16:47against the onslaught of mosquitoes in much the same way as humans do
0:16:47 > 0:16:51by rubbing themselves with mosquito repellent?
0:16:56 > 0:17:00In 1993, scientists at Oxford University
0:17:00 > 0:17:03decided to put the question to the test.
0:17:03 > 0:17:06They collected some feather lice
0:17:06 > 0:17:10and put them into Petri dishes overnight.
0:17:11 > 0:17:16Into one dish, they also placed a slice of lime.
0:17:19 > 0:17:23The next day, the lice without the lime were mostly alive.
0:17:24 > 0:17:27Whilst in the other dish, two-thirds had died
0:17:27 > 0:17:30and the remainder were paralysed.
0:17:31 > 0:17:36Clearly, the lime contains a lethal insecticide.
0:17:38 > 0:17:41Today, we know that citrus fruit peel
0:17:41 > 0:17:44does indeed contain insecticides
0:17:44 > 0:17:47which disrupt the nervous system of many small insects,
0:17:47 > 0:17:51causing them to become uncoordinated and paralysed.
0:17:51 > 0:17:55The leaves of the piper plant are antiseptic and contain substances
0:17:55 > 0:17:59that protect against fungal and bacterial infection.
0:17:59 > 0:18:03And chilli pepper extract is commonly used in households
0:18:03 > 0:18:08and gardens to deter small mammals and insect pests.
0:18:11 > 0:18:13So it seems that the clever monkeys know
0:18:13 > 0:18:16exactly how to make the best use of nature's remedies.
0:18:18 > 0:18:22Recent research has also revealed that capuchins anoint themselves
0:18:22 > 0:18:25far more during the wet season when mosquitoes are more abundant
0:18:25 > 0:18:27and the risk of infection is higher.
0:18:29 > 0:18:31Troops use different plants,
0:18:31 > 0:18:35possibly simply because they have to use what's locally available.
0:18:36 > 0:18:39But there's one substance with insect repellent qualities
0:18:39 > 0:18:43that appeals to primates, including capuchins,
0:18:43 > 0:18:47that comes not from a plant but from an animal.
0:18:47 > 0:18:49An animal like this.
0:18:50 > 0:18:52A giant millipede.
0:18:53 > 0:18:55When attacked or in danger,
0:18:55 > 0:19:00tropical millipedes often produce a powerful defensive secretion.
0:19:01 > 0:19:05And black lemurs have worked out how to use this to their advantage.
0:19:07 > 0:19:11When they find a millipede, they give it a gentle bite to the head
0:19:11 > 0:19:16to make it release its secretion, and then rub this through their fur.
0:19:16 > 0:19:21The toxic fluid has a strong smell and is highly irritating,
0:19:21 > 0:19:24but it protects the lemurs against mosquitoes.
0:19:26 > 0:19:31This pungent secretion has apparently another strange effect.
0:19:31 > 0:19:33It seems to act as a narcotic,
0:19:33 > 0:19:36sending the lemur into a kind of trance.
0:19:36 > 0:19:40Like other drugs, it has powerful side effects.
0:19:42 > 0:19:46We still don't understand how capuchins and lemurs
0:19:46 > 0:19:50select the plants that they use for medicinal purposes.
0:19:50 > 0:19:54These capuchins behind me were born and raised in captivity
0:19:54 > 0:19:56so they've never encountered the plants
0:19:56 > 0:19:59that their parents and ancestors would have used.
0:20:01 > 0:20:05So how did the monkeys know which plants to choose?
0:20:05 > 0:20:08Can they detect particular substances in them?
0:20:08 > 0:20:11Or is it something they learn from others?
0:20:11 > 0:20:13We don't yet know the answers
0:20:13 > 0:20:17but it could be that babies learn by watching the adults
0:20:17 > 0:20:20and that it's passed down the family line.
0:20:20 > 0:20:25It's clearly a great social event with everyone joining in.
0:20:27 > 0:20:32And, afterwards, the entire group appears to be more tightly bonded.
0:20:35 > 0:20:39When Europeans first saw monkeys in the wild,
0:20:39 > 0:20:42they thought that they were imitating what people did
0:20:42 > 0:20:45in some of their behaviours.
0:20:45 > 0:20:46But quite the reverse,
0:20:46 > 0:20:50it now turns out that many of the local people did things
0:20:50 > 0:20:55that the monkeys had taught them, using plants as medicines.
0:20:55 > 0:21:00So it seems clever monkeys have taught us a trick or two.
0:21:06 > 0:21:10So, it's clear that we're not alone in using medicines
0:21:10 > 0:21:12against injuries and infections.
0:21:12 > 0:21:17Both capuchin monkeys and hippos discovered some medical remedies
0:21:17 > 0:21:19long before we did.