0:00:02 > 0:00:06The natural world is full of extraordinary animals with
0:00:06 > 0:00:09amazing 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.
0:00:19 > 0:00:21Or the strange biology of the emperor penguin.
0:00:23 > 0:00:25Some of these creatures were surrounded by myth
0:00:25 > 0:00:28and misunderstandings for a very long time.
0:00:29 > 0:00:33And some have only recently revealed their secrets.
0:00:34 > 0:00:38These are the animals that stand out from the crowd.
0:00:38 > 0:00:42The curiosities I find most fascinating of all.
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 > 0:01:06And capuchin monkeys live in insect-infested jungles,
0:01:06 > 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?
0:01:20 > 0:01:22And also in this programme,
0:01:22 > 0:01:26some animals can perform amazing physical feats.
0:01:26 > 0:01:30A flea's jump is said to be the equivalent of a man leaping
0:01:30 > 0:01:32over St Paul's cathedral.
0:01:32 > 0:01:37And it's famously quoted that cheetahs can run at speeds of 70mph.
0:01:39 > 0:01:42But are these claims really true?
0:01:50 > 0:01:55Hippos are large land mammals that can weigh up to three tonnes.
0:01:55 > 0:01:57And they need to keep their huge bodies cool
0:01:57 > 0:02:00and protected from the sun.
0:02:00 > 0:02:03To avoid the heat, they spend much of the day swimming,
0:02:03 > 0:02:06as they are doing now in the waters behind me.
0:02:06 > 0:02:10But when they're on land, strangely they don't appear to get sunburnt.
0:02:12 > 0:02:16The secret of their sun tolerance lies within their skin
0:02:16 > 0:02:19that can sometimes appear shiny and greasy.
0:02:19 > 0:02:23It has unique properties that shocked the early explorers
0:02:23 > 0:02:26and now excites modern scientists.
0:02:30 > 0:02:33Hippos live in Africa, south of the Sahara,
0:02:33 > 0:02:37where temperatures can reach 40 degrees centigrade.
0:02:37 > 0:02:40But they spend much of the day submerged in rivers,
0:02:40 > 0:02:45lakes and swamps, and so avoid the worst of the sun's rays.
0:02:48 > 0:02:53They possess formidable teeth, but they are in fact herbivores
0:02:53 > 0:02:56and eat mostly grass, great quantities of it.
0:02:56 > 0:02:58And they graze mostly at night.
0:03:00 > 0:03:05Even so, continually moving in and out of water, together with being
0:03:05 > 0:03:09roasted by the rays of the sun, could be very damaging to their skin.
0:03:11 > 0:03:13But curiously, hippos remain healthy.
0:03:19 > 0:03:20Throughout history,
0:03:20 > 0:03:24the hippopotamus has been the subject of many strange tales.
0:03:24 > 0:03:28The Greeks claimed they sweated blood, and the Romans said
0:03:28 > 0:03:33they deliberately pierced their skin on sharp rushes to release blood.
0:03:33 > 0:03:37It seemed bizarre that an animal would make itself bleed on purpose.
0:03:39 > 0:03:43In the 19th century, one special hippopotamus allowed people
0:03:43 > 0:03:46to get a closer look at these strange skin secretions.
0:03:50 > 0:03:55In 1849, the British consul for Egypt, Charles Augustus Murray,
0:03:55 > 0:03:59formally requested that the Pasha of Egypt helped capture
0:03:59 > 0:04:03a hippo for the Zoological Society of London.
0:04:03 > 0:04:07Hunters searched the reeds on a remote island called Obaysch.
0:04:08 > 0:04:132,000km up the Nile from Cairo,
0:04:13 > 0:04:18they discovered a male hippo that was only a few days old.
0:04:18 > 0:04:21When they tried to grab it, a strange thing happened.
0:04:21 > 0:04:26Murray describes how, "A slimy exudation lavishly poured forth
0:04:26 > 0:04:29"from the innumerable pores in the skin,
0:04:29 > 0:04:34"rendering it so slippery that the animal was impossible to hold."
0:04:34 > 0:04:38The hunters dropped the baby hippo back into the waters of the Nile,
0:04:38 > 0:04:43but they managed to retrieve it again, using the hook of a spear.
0:04:43 > 0:04:48The prized hippo was named Obaysch after the island of its capture,
0:04:48 > 0:04:50and here he is.
0:04:55 > 0:04:59Before his capture, young Obaysch lived with his mother.
0:04:59 > 0:05:02She had moved away from the herd to give birth alone,
0:05:02 > 0:05:06and she protected him from lions and crocodiles.
0:05:06 > 0:05:09Whether Obaysch became accidentally separated from his mother,
0:05:09 > 0:05:11we'll never know,
0:05:11 > 0:05:14but we do know that secretions from his skin made him
0:05:14 > 0:05:17so slippery that he very nearly escaped capture.
0:05:19 > 0:05:22At this time, very little was known about hippos,
0:05:22 > 0:05:26and many people believed that they were some kind of horse
0:05:26 > 0:05:28that had taken to living in rivers.
0:05:30 > 0:05:32In the early 20th century,
0:05:32 > 0:05:36naturalists decided that they were closely related to pigs.
0:05:37 > 0:05:42DNA evidence, however, now shows that, in fact, their ancestors
0:05:42 > 0:05:49were cetaceans - the group that contains whales and dolphins -
0:05:49 > 0:05:54so hippos still retain many adaptations for a life in water.
0:05:58 > 0:06:01Hippos are very heavy animals
0:06:01 > 0:06:05but, for most of their time, their bodies are supported by water.
0:06:05 > 0:06:07They're not really very good swimmers.
0:06:07 > 0:06:11In the water, they move by bounding across the bottom.
0:06:11 > 0:06:15They're well adapted to a semi-aquatic life
0:06:15 > 0:06:19because their ears, their eyes, and their nostrils are all towards
0:06:19 > 0:06:24the top of the head, which enables them to lie almost totally submerged
0:06:24 > 0:06:28and yet still keep notice of what's going on on land,
0:06:28 > 0:06:31but their skin is almost entirely hairless,
0:06:31 > 0:06:34so, on land, it has to be kept moist.
0:06:38 > 0:06:43In order to prevent young Obaysch from sunburn and drying out,
0:06:43 > 0:06:46the Egyptian Pasha had a boat built with a bathing pool,
0:06:46 > 0:06:51to transport Obaysch in comfort all the way down the River Nile.
0:06:52 > 0:06:55Accompanied by several cows to supply him with milk,
0:06:55 > 0:06:59he arrived safely in Cairo four months later.
0:07:02 > 0:07:03On receiving Obaysch,
0:07:03 > 0:07:08the British Consul wrote excitedly to the Zoological Society of London,
0:07:08 > 0:07:13confirming that the hippo was alive, and as tame and playful as a puppy.
0:07:13 > 0:07:17But his travels were not yet over.
0:07:17 > 0:07:21In the spring of 1850, Obaysch was taken to Alexandria,
0:07:21 > 0:07:25to board a P&O steamship called the Ripon.
0:07:25 > 0:07:28A special hippo house with a water tank was built on the deck
0:07:28 > 0:07:32and, in May, Obaysch arrived safely in Southampton.
0:07:32 > 0:07:34With the help of a block and tackle,
0:07:34 > 0:07:38he was loaded onto a train bound for London,
0:07:38 > 0:07:39and at 10 o'clock at night,
0:07:39 > 0:07:43the tired hippo and his keeper reached London Zoo.
0:07:44 > 0:07:47His home was a newly constructed enclosure,
0:07:47 > 0:07:50complete with a heated swimming pool.
0:07:50 > 0:07:52After many hours of travelling,
0:07:52 > 0:07:54the hippo gratefully plunged into the water.
0:07:54 > 0:07:58Obaysch, the hippo sensation, had arrived.
0:08:02 > 0:08:08A journey of over 5,000 miles, by sailboat, steamboat and a train,
0:08:08 > 0:08:10brought a hippo to England -
0:08:10 > 0:08:13the first one since Roman times.
0:08:15 > 0:08:19Now, Europeans had a chance to get close to this unusual creature
0:08:19 > 0:08:24and perhaps learn more about its strange skin secretions.
0:08:25 > 0:08:29Later, more hippos arrived at other zoos,
0:08:29 > 0:08:31and the blood-red sweat was seen again.
0:08:32 > 0:08:35In the cooler climate of Europe,
0:08:35 > 0:08:37hippos don't sweat very much
0:08:37 > 0:08:40but, zookeepers have reported that, sometimes, in the morning,
0:08:40 > 0:08:45they see red trickles forming on the flanks of these animals.
0:08:45 > 0:08:49It comes from particularly large pores,
0:08:49 > 0:08:52which form streaks on the animal's side,
0:08:52 > 0:08:57which does look a little like blood.
0:08:57 > 0:09:00We've known for some time that this is a...
0:09:00 > 0:09:05a moisturiser, but why it's red has only just been discovered.
0:09:07 > 0:09:09A little more.
0:09:09 > 0:09:10Come on.
0:09:10 > 0:09:11There we go.
0:09:13 > 0:09:16Recently, Japanese scientists were intrigued to see
0:09:16 > 0:09:20photos of a wild baby hippo with light pink skin
0:09:20 > 0:09:24that still didn't burn under the harsh African sun.
0:09:24 > 0:09:27They wondered if the red secretion played
0:09:27 > 0:09:30a role in protecting its pale skin,
0:09:30 > 0:09:33so they collected hippo secretion from captive hippos
0:09:33 > 0:09:36to look at its composition.
0:09:36 > 0:09:38They discovered two pigments -
0:09:38 > 0:09:41a red one, that they named hipposudoric acid,
0:09:41 > 0:09:46and an orange one, that they called norhipposudoric acid.
0:09:47 > 0:09:52The red pigment was found to absorb harmful wavelengths of light
0:09:52 > 0:09:54and both pigments were antibacterial.
0:09:57 > 0:10:01Here was the answer to why hippos never got sunburnt
0:10:01 > 0:10:05and why the wounds of battling males rarely became infected.
0:10:05 > 0:10:08HIPPOS GRUNT
0:10:08 > 0:10:12The mysterious slime is neither blood nor sweat,
0:10:12 > 0:10:15but a specialised secretion that turns red in sunlight
0:10:15 > 0:10:17and protects the hippos' skin.
0:10:17 > 0:10:20HIPPOS GRUNT
0:10:20 > 0:10:25So, what became of Obaysch, the first ever hippo in captivity
0:10:25 > 0:10:29that gave us a close-up view of these curious creatures?
0:10:29 > 0:10:33For several years, he was a sensation at the London Zoo.
0:10:33 > 0:10:39He even inspired the Hippo Polka, a popular dance of its time,
0:10:39 > 0:10:42but visitors grew weary of him.
0:10:42 > 0:10:46Some were disappointed not to see a giant river-horse
0:10:46 > 0:10:50and others expected a ferocious beast, not a gentle giant.
0:10:50 > 0:10:54Obaysch died in 1878 at the age of 28,
0:10:54 > 0:10:56and he and others that followed
0:10:56 > 0:10:59taught us some intriguing things about hippos,
0:10:59 > 0:11:01including the reason for the blood-red droplets
0:11:01 > 0:11:05found on their skin. HIPPOS GRUNT
0:11:05 > 0:11:09So, hippos can produce their very own natural sun cream
0:11:09 > 0:11:13that is waterproof, moisturising and antibacterial.
0:11:16 > 0:11:21Next, we meet another animal that has its own natural cure.
0:11:21 > 0:11:25Capuchin monkeys have a surprising way of protecting their skin
0:11:25 > 0:11:27from stings and bites.
0:11:27 > 0:11:29MONKEYS SCREECH
0:11:31 > 0:11:35When early explorers reached the Americas in the 15th century,
0:11:35 > 0:11:37they encountered small monkeys
0:11:37 > 0:11:43with patches of dark brown fur on their heads that resembled hoods,
0:11:43 > 0:11:46so they named them after a group of Franciscan friars
0:11:46 > 0:11:48called Capuchin monks.
0:11:52 > 0:11:57Capuchin monkeys quickly charmed their way into our hearts.
0:11:57 > 0:12:00With dextrous hands and inquisitive personalities,
0:12:00 > 0:12:02they seemed very humanlike.
0:12:04 > 0:12:07They were also adept at learning tricks
0:12:07 > 0:12:10and soon became popular performers on our streets.
0:12:14 > 0:12:16MONKEY SQUEAKS
0:12:16 > 0:12:21In the past, we used to teach monkeys how to do things -
0:12:21 > 0:12:23how to perform tricks -
0:12:23 > 0:12:26but things are different today.
0:12:26 > 0:12:30Today, monkeys are teaching us things.
0:12:30 > 0:12:36Watch what happens when I give them a few spring onions
0:12:36 > 0:12:38and some chilli peppers.
0:12:38 > 0:12:42MONKEYS SQUEAK
0:12:51 > 0:12:53MONKEY SQUEAKS
0:13:09 > 0:13:11They're clearly not eating what I offered them.
0:13:11 > 0:13:16They're rubbing themselves with the peppers and the onions.
0:13:16 > 0:13:19You might think that that's because they're captive monkeys,
0:13:19 > 0:13:22and they are just doing that to entertain themselves,
0:13:22 > 0:13:24but not so.
0:13:24 > 0:13:27I've seen capuchins do just that in the wild.
0:13:39 > 0:13:42MONKEYS SQUEAK
0:13:42 > 0:13:45These white-faced capuchins in Costa Rica
0:13:45 > 0:13:47reacted in much the same way
0:13:47 > 0:13:52when they came across a particular rainforest plant - the piper plant.
0:13:55 > 0:13:58These leaves have a distinctive liquorice scent
0:13:58 > 0:14:01and they are hard to come by, so when they do find them,
0:14:01 > 0:14:04the monkeys passed the leaves around the troop
0:14:04 > 0:14:06so that everyone can have a share.
0:14:06 > 0:14:08MONKEYS CHATTER
0:14:11 > 0:14:14Both in the wild and in captivity,
0:14:14 > 0:14:17capuchin monkeys become similarly excited
0:14:17 > 0:14:19at the sight of lemons or limes,
0:14:19 > 0:14:24and, again, the same frenzied activity and fur-rubbing follows.
0:14:28 > 0:14:32What is it about these plants that gets the monkeys so excited?
0:14:36 > 0:14:39We know they all give off a pungent smell,
0:14:39 > 0:14:42so could this be what the capuchins are after?
0:14:42 > 0:14:45LEMURS SQUEAL
0:14:45 > 0:14:49Smell plays an important part in the lives of many primates,
0:14:49 > 0:14:51but none more so than in the lives
0:14:51 > 0:14:55of these lovely ring-tailed lemurs. LEMURS CHATTER
0:14:55 > 0:14:59They use it both to establish their position within the troop
0:14:59 > 0:15:04and also the boundaries - the frontiers - of their territory.
0:15:04 > 0:15:06If you look at the inside of their forearms,
0:15:06 > 0:15:09there's a black patch without fur, and there,
0:15:09 > 0:15:15the skin is loaded with glands that produce a very strong smell,
0:15:15 > 0:15:17and when these boys go into battle... Whoops!
0:15:17 > 0:15:19When they go into battle,
0:15:19 > 0:15:23they draw their furry tail through their forearms,
0:15:23 > 0:15:25loading it with scent from those glands,
0:15:25 > 0:15:28and then they wave it over their backs
0:15:28 > 0:15:32in the direction of their enemies, in a kind of stink fight.
0:15:34 > 0:15:35You understand that, don't you?
0:15:35 > 0:15:38LEMURS SQUEAK Oh!
0:15:42 > 0:15:44LEMURS CHIRP The pungent scent is also used
0:15:44 > 0:15:47by males during the mating season.
0:15:47 > 0:15:51This male has rubbed his own distinctive smell onto his tail
0:15:51 > 0:15:56and he now wafts over towards a female to signal his intentions...
0:15:57 > 0:16:01LEMUR SQUEALS ..but she is not entirely convinced.
0:16:04 > 0:16:08Unlike lemurs, capuchins don't have scent glands,
0:16:08 > 0:16:10so some thought that they could be
0:16:10 > 0:16:12using the smell of certain plants
0:16:12 > 0:16:14for communication... MONKEYS CHATTER
0:16:14 > 0:16:19..but it turns out that they have a different perfume for that job -
0:16:19 > 0:16:24urine, which they apply lavishly to their fur.
0:16:24 > 0:16:29So, why, then, do they also anoint themselves with other smells?
0:16:29 > 0:16:33The answer may be found in our own history.
0:16:34 > 0:16:38The early Romans noticed some 2,000 years ago that the fruits
0:16:38 > 0:16:43and leaves of the lemon plant have an exceptionally strong scent
0:16:43 > 0:16:45that could be used to ward off insects.
0:16:47 > 0:16:50A further clue as to why capuchins might cover themselves
0:16:50 > 0:16:54in such pungent smells comes from this plant -
0:16:54 > 0:16:56the piper plant.
0:16:56 > 0:16:58Throughout the Amazon,
0:16:58 > 0:17:03Indian tribes apply it as an antiseptic on wounds,
0:17:03 > 0:17:07and in Costa Rica, it's used as an insect repellent.
0:17:07 > 0:17:11Could it be that capuchin monkeys protect themselves
0:17:11 > 0:17:13against the onslaught of mosquitoes in much the same way
0:17:13 > 0:17:18as humans do by rubbing themselves with mosquito repellent?
0:17:23 > 0:17:27In 1993, scientists at Oxford University
0:17:27 > 0:17:30decided to put the question to the test.
0:17:31 > 0:17:34They collected some feather lice
0:17:34 > 0:17:36and put them into petri dishes overnight.
0:17:38 > 0:17:40Into one dish,
0:17:40 > 0:17:43they also placed a slice of lime.
0:17:46 > 0:17:51The next day, the lice without the lime were mostly alive,
0:17:51 > 0:17:55whilst, in the other dish, two thirds had died
0:17:55 > 0:17:58and the remainder were paralysed.
0:17:58 > 0:18:02Clearly, the lime contains a lethal insecticide.
0:18:05 > 0:18:09Today, we know that citrus-fruit peel
0:18:09 > 0:18:11does indeed contain insecticides,
0:18:11 > 0:18:14which disrupt the nervous system of many small insects,
0:18:14 > 0:18:17causing them to become uncoordinated and paralysed.
0:18:19 > 0:18:21The leaves of the piper plant are antiseptic
0:18:21 > 0:18:24and contain substances that protect against fungal
0:18:24 > 0:18:27and bacterial infection,
0:18:27 > 0:18:31and chilli pepper extract is commonly used in households
0:18:31 > 0:18:35and gardens to deter small mammals and insect pests.
0:18:38 > 0:18:41So, it seems that the clever monkeys know exactly how to make
0:18:41 > 0:18:45the best use of nature's remedies. MONKEYS SQUEAK
0:18:45 > 0:18:47Recent research has also revealed
0:18:47 > 0:18:50that capuchins anoint themselves far more during the wet season,
0:18:50 > 0:18:55when mosquitoes are more abundant and the risk of infection is higher.
0:18:56 > 0:19:00Troops use different plants, possibly, simply,
0:19:00 > 0:19:03because they have to use what's locally available.
0:19:03 > 0:19:07But there's one substance with insect-repellent qualities
0:19:07 > 0:19:10that appeals to primates, including capuchins,
0:19:10 > 0:19:14that comes not from a plant but from an animal -
0:19:14 > 0:19:18an animal like this -
0:19:18 > 0:19:20a giant millipede.
0:19:20 > 0:19:22When attacked or in danger,
0:19:22 > 0:19:28tropical millipedes often produce a powerful defensive secretion...
0:19:28 > 0:19:30MONKEYS SCREECH ..and black lemurs have worked out
0:19:30 > 0:19:32how to use this to their advantage.
0:19:35 > 0:19:36When they find a millipede,
0:19:36 > 0:19:38they give it a gentle bite to the head
0:19:38 > 0:19:40to make it release its secretion,
0:19:40 > 0:19:43and then rub this through their fur.
0:19:43 > 0:19:46The toxic fluid has a strong smell
0:19:46 > 0:19:48and is highly irritating... LEMURS SCREECH
0:19:48 > 0:19:51..but it protects the lemurs against mosquitoes.
0:19:53 > 0:19:58This pungent secretion has apparently another strange effect -
0:19:58 > 0:20:00it seems to act as a narcotic,
0:20:00 > 0:20:04sending the lemur into a kind of trance.
0:20:04 > 0:20:05Like other drugs,
0:20:05 > 0:20:07it has powerful side effects.
0:20:10 > 0:20:13We still don't understand how capuchins and lemurs
0:20:13 > 0:20:17select the plants that they use for medicinal purposes.
0:20:17 > 0:20:21These capuchins behind me were born and raised in captivity,
0:20:21 > 0:20:24so they never encountered the plants that their parents
0:20:24 > 0:20:27and ancestors would have used.
0:20:28 > 0:20:30So, how do the monkeys know
0:20:30 > 0:20:32which plants to choose? MONKEYS CHATTER
0:20:32 > 0:20:35Can they detect particular substances in them
0:20:35 > 0:20:38or is it something they learn from others?
0:20:38 > 0:20:40We don't yet know the answers,
0:20:40 > 0:20:43but it could be that babies learn by watching the adults
0:20:43 > 0:20:46and that it's passed down the family line.
0:20:48 > 0:20:50It's clearly a great social event,
0:20:50 > 0:20:54with everyone joining in
0:20:54 > 0:20:59and, afterwards, the entire group appears to be more tightly bonded.
0:20:59 > 0:21:01MONKEYS SQUEAK
0:21:03 > 0:21:07When Europeans first saw monkeys in the wild,
0:21:07 > 0:21:10they thought that they were imitating what people did
0:21:10 > 0:21:14in some of their behaviours, but quite the reverse.
0:21:14 > 0:21:18It now turns out that many of the local people did things
0:21:18 > 0:21:20that the monkeys had taught them -
0:21:20 > 0:21:23using plants as medicines -
0:21:23 > 0:21:27so it seems that clever monkeys have taught us a trick or two.
0:21:51 > 0:21:53Quick! Look!
0:21:53 > 0:21:57This is a real live flea circus,
0:21:57 > 0:22:02and you can see this one pulling along this tiny chariot.
0:22:02 > 0:22:07There are very few circuses like this these days.
0:22:07 > 0:22:10The whole business of performing fleas dates back
0:22:10 > 0:22:11into the 16th century,
0:22:11 > 0:22:14and it was used by watchmakers,
0:22:14 > 0:22:17who used them to demonstrate how they themselves could
0:22:17 > 0:22:19work on a near-miniature scale.
0:22:19 > 0:22:23They used thin gold wires to harness fleas
0:22:23 > 0:22:26and then linked the fleas to tiny chains.
0:22:27 > 0:22:29Early magnifying devices like this
0:22:29 > 0:22:34were actually named fleaglasses after these pests,
0:22:34 > 0:22:37and the fleas were excellent creatures to
0:22:37 > 0:22:41demonstrate a newly-visible microscopic world.
0:22:41 > 0:22:45Fleas appear to be extraordinarily strong.
0:22:45 > 0:22:50After all, this little badger flea here, pulling this chariot -
0:22:50 > 0:22:52what an extraordinary thing.
0:22:52 > 0:22:56That's the equivalent to me trying to pull a jumbo jet single-handed.
0:22:56 > 0:22:58And this tiny merry-go-round -
0:22:58 > 0:23:01that, too, is completely powered by fleas.
0:23:04 > 0:23:09The secret of the fleas' strength and ability to move such equipment
0:23:09 > 0:23:13lies in their powerful walking and jumping techniques.
0:23:13 > 0:23:18They have the ability to store and then release energy,
0:23:18 > 0:23:22and that enables them to leap upwards with great acceleration.
0:23:24 > 0:23:27Fleas need to be good jumpers.
0:23:27 > 0:23:31They live on the skin of mammals and birds, sucking their blood,
0:23:31 > 0:23:35so they have to be able to quickly leap onboard their travelling hosts
0:23:35 > 0:23:37when they get the chance.
0:23:38 > 0:23:42There are more than 2,500 species worldwide,
0:23:42 > 0:23:4562 of which live in Britain.
0:23:45 > 0:23:49Fortunately, only a few feed on us.
0:23:55 > 0:23:57Rat fleas were said to be responsible
0:23:57 > 0:24:05for the spread of the Black Death in 1665, which killed millions,
0:24:05 > 0:24:08but it wasn't until the invention of the magnifying glass
0:24:08 > 0:24:12that we were able to see these tiny creatures face-to-face.
0:24:13 > 0:24:19In 1665, Robert Hooke, an inventor and natural philosopher,
0:24:19 > 0:24:22made one of the first compound microscopes.
0:24:22 > 0:24:24This is a later reproduction of it.
0:24:24 > 0:24:28And he then published his discoveries that he made using it
0:24:28 > 0:24:32in a marvellous book called Micrographia.
0:24:32 > 0:24:36It became one of the first scientific bestsellers.
0:24:36 > 0:24:39Samuel Pepys mentioned it in his diary,
0:24:39 > 0:24:42and it contained magnificent, detailed drawings
0:24:42 > 0:24:46that revealed biological structures that had never been seen before.
0:24:46 > 0:24:50He saw that plant tissue was made up of little units
0:24:50 > 0:24:54that he called cells - the word we still use -
0:24:54 > 0:24:58and he drew this marvellously detailed flea,
0:24:58 > 0:25:01showing its great, strikingly long legs.
0:25:03 > 0:25:06He also watched it through the microscope
0:25:06 > 0:25:09and he described how a flea jumped.
0:25:09 > 0:25:11This is what he says...
0:25:11 > 0:25:17"When the flea intends to leap, he folds up these six legs together,
0:25:17 > 0:25:20"then springs them all out at the same instant,
0:25:20 > 0:25:24"and thereby exerting his whole strength at once,
0:25:24 > 0:25:28"carries his little body to a considerable distance."
0:25:28 > 0:25:30And indeed he does.
0:25:36 > 0:25:40A flea's jump takes just one thousandth of a second,
0:25:40 > 0:25:44so Hooke must have had very sharp eyesight to see it.
0:25:47 > 0:25:50Many researchers have been fascinated by fleas,
0:25:50 > 0:25:54and for one particular family, they became an obsession.
0:25:55 > 0:25:58Charles Rothschild, a banker and keen naturalist,
0:25:58 > 0:26:01amassed over 30,000 specimens
0:26:01 > 0:26:05and identified more than 500 new species.
0:26:09 > 0:26:12He purchased them from specialist traders worldwide,
0:26:12 > 0:26:17and one parcel from America had a special surprise -
0:26:17 > 0:26:20the tiny fleas were dressed as Mexicans.
0:26:29 > 0:26:33Miriam, Charles's daughter, shared his passion for fleas
0:26:33 > 0:26:36and catalogued his whole collection.
0:26:36 > 0:26:39She looked closely at the flea's body and the way they jumped,
0:26:39 > 0:26:42and was puzzled to find that they could leap far higher than
0:26:42 > 0:26:45should theoretically have been possible,
0:26:45 > 0:26:49but could their reputation for jumping 200 times their body length
0:26:49 > 0:26:51possibly be true?
0:26:56 > 0:26:58Most of the natural world's top jumpers
0:26:58 > 0:27:02achieve their impressive leaps by using straightforward muscle power.
0:27:03 > 0:27:08Kangaroos can make single bounds of almost eight metres
0:27:08 > 0:27:13and frogs are able to jump more than 20 times their body length.
0:27:20 > 0:27:23The jumping spider's leap is even more impressive -
0:27:23 > 0:27:26100 times its own length.
0:27:26 > 0:27:30It achieves this by exploiting hydraulics,
0:27:30 > 0:27:34and scientists had long suspected that fleas and other insects
0:27:34 > 0:27:39also needed something other than muscle to make their huge jumps.
0:27:44 > 0:27:48In the 1960s, an exciting discovery was made in the insect world
0:27:48 > 0:27:51that helped explain how bigger flying insects,
0:27:51 > 0:27:53like locusts and dragonflies,
0:27:53 > 0:27:56were able to fly and jump so well.
0:27:56 > 0:28:00A rubbery protein was found in the hinges and joints
0:28:00 > 0:28:03of locusts' wings and legs.
0:28:03 > 0:28:06Using ultraviolet light, it's possible to see it,
0:28:06 > 0:28:10as in this picture of the leg joint of a locust.
0:28:10 > 0:28:14Here, that blue is this new substance.
0:28:14 > 0:28:16But, just like this rubber,
0:28:16 > 0:28:20it could bend and then release energy,
0:28:20 > 0:28:23but the newly discovered material did that
0:28:23 > 0:28:26with more than 90% efficiency.
0:28:26 > 0:28:29Remarkably, too, it repeatedly snapped back into shape
0:28:29 > 0:28:31without any deformation.
0:28:31 > 0:28:33It was named resilin.
0:28:35 > 0:28:39This stretchy protein allows insects to bend their stiff bodies
0:28:39 > 0:28:42and stretch their tendons without snapping.
0:28:44 > 0:28:47It's so robust, it lasts a lifetime,
0:28:47 > 0:28:51and it's believed to be the most efficient elastic protein known.
0:28:54 > 0:28:59The discovery of resilin opened up a whole new area of study,
0:28:59 > 0:29:03and in 1966, Henry Bennet-Clark,
0:29:03 > 0:29:06an expert in insect biomechanics,
0:29:06 > 0:29:08had a breakthrough moment.
0:29:09 > 0:29:13He had the chance to see some exciting new footage of fleas,
0:29:13 > 0:29:15shot on a newly invented
0:29:15 > 0:29:16high-speed camera.
0:29:18 > 0:29:21Bennet-Clark studied the new flea footage
0:29:21 > 0:29:26and built a mechanical model 400 times bigger than the flea.
0:29:26 > 0:29:29He calculated that the fleas were somehow generating
0:29:29 > 0:29:33much more power than their muscles could actually provide.
0:29:33 > 0:29:36He noticed that, just before leaping,
0:29:36 > 0:29:41the flea bent the closest segment of its hindmost legs towards the body
0:29:41 > 0:29:44and hesitated for about a tenth of a second.
0:29:44 > 0:29:49Carefully, he dissected fleas and found a pad of material,
0:29:49 > 0:29:52and that proved to be resilin.
0:29:52 > 0:29:55He proposed that fleas stored some of the energy for their jumps
0:29:55 > 0:29:57in this rubberlike tissue,
0:29:57 > 0:30:00and then released it as they pushed off with their shins and feet.
0:30:04 > 0:30:09So, the tiny wingless fleas use internal resilin springs
0:30:09 > 0:30:14like those of other, bigger, flying and jumping insects,
0:30:14 > 0:30:18and the secret of their huge leaps lies in the efficient way they
0:30:18 > 0:30:23combine muscle, tendons and joints to harness the resilin's energy.
0:30:26 > 0:30:32Only today do we know how a flea jumps and how high it can jump,
0:30:32 > 0:30:36just as, in Hooke's time, a modern technology - a microscope -
0:30:36 > 0:30:40enabled him to see the anatomy of the flea for the very first time,
0:30:40 > 0:30:46so we have a camera now which is recording 5,000 images a second,
0:30:46 > 0:30:49which will enable us to see how it jumps.
0:30:49 > 0:30:51The camera is already running.
0:30:51 > 0:30:55The flea is in that little box there
0:30:55 > 0:30:59and we can see the image from the camera on this computer.
0:30:59 > 0:31:03I will stop it as soon as I see that the flea has jumped.
0:31:06 > 0:31:07There.
0:31:10 > 0:31:15Its legs are already cocked in the jumping position,
0:31:15 > 0:31:17and the cuticle, which is fused to the resilin,
0:31:17 > 0:31:20is bent and ready to release its energy,
0:31:20 > 0:31:22and then it lifts itself from the ground
0:31:22 > 0:31:24and it's catapulted into the air.
0:31:28 > 0:31:32Our story about fleas started 350 years ago
0:31:32 > 0:31:36with Robert Hooke's first microscopic study.
0:31:36 > 0:31:41Today, images from electron microscopes reveal even more details
0:31:41 > 0:31:43than Hooke's beautiful drawings.
0:31:43 > 0:31:46They show the rough hairs on the flea's shins and toes
0:31:46 > 0:31:49that help it grip before thrusting itself into the air
0:31:49 > 0:31:52with the final push from its toes.
0:31:53 > 0:31:58So, can fleas jump 200 times their own body length?
0:31:58 > 0:32:00It would seem not.
0:32:00 > 0:32:02Nonetheless, they can leap
0:32:02 > 0:32:04a respectable 38 times
0:32:04 > 0:32:07the length of their bodies, which is not bad.
0:32:09 > 0:32:13Fleas are extraordinarily strong
0:32:13 > 0:32:16and we now know how they jump,
0:32:16 > 0:32:19but the fleas' story isn't quite over.
0:32:19 > 0:32:22A new discovery has added a twist to their lives
0:32:22 > 0:32:24and dispelled another myth.
0:32:25 > 0:32:29Recently, bodies of people who died of the Black Death
0:32:29 > 0:32:33were uncovered by workers digging a new railway line.
0:32:33 > 0:32:37Close inspection revealed that the Black Death was an airborne disease
0:32:37 > 0:32:42and had nothing to do with rats or their fleas,
0:32:42 > 0:32:46so the fleas' good name can at last be restored, and we can
0:32:46 > 0:32:51celebrate them as one of the natural world's most spectacular jumpers.
0:32:52 > 0:32:56A springy protein propels fleas with great force.
0:32:58 > 0:33:02Next, we investigate another impossible feat -
0:33:02 > 0:33:06the cheetah's legendary top speed of 70mph.
0:33:06 > 0:33:08AEROPLANE ENGINE ROARS
0:33:08 > 0:33:10Is this really possible?
0:33:12 > 0:33:14CHEETAH PURRS
0:33:14 > 0:33:19Cheetahs are beautiful, athletic-looking cats.
0:33:19 > 0:33:22They've got the streamlined body, the small head,
0:33:22 > 0:33:25elongated legs and narrow shoulders,
0:33:25 > 0:33:27and a very long spine.
0:33:28 > 0:33:32This looks like an animal that's built for speed,
0:33:32 > 0:33:35but exactly how fast can he run? CHEETAH PURRS
0:33:38 > 0:33:41They've been admired for their
0:33:41 > 0:33:43grace and speed since antiquity.
0:33:43 > 0:33:45The Egyptians were sometimes
0:33:45 > 0:33:47buried with these cats because
0:33:47 > 0:33:49they believed that they could hasten
0:33:49 > 0:33:52the journey to the after-world
0:33:52 > 0:33:53and, in more recent times,
0:33:53 > 0:33:57sports hunters have used cheetahs to run down their prey.
0:34:01 > 0:34:07So, the cheetah's impressive sprint has been known about for some time,
0:34:07 > 0:34:11but where did the magical figure of 70mph come from?
0:34:15 > 0:34:18Back in 1957, a cheetah hit the headlines,
0:34:18 > 0:34:21with news of a rather unusual experiment.
0:34:30 > 0:34:32A photographer called Kurt Severin
0:34:32 > 0:34:36filmed and measured the running speed of a tame cheetah
0:34:36 > 0:34:40using an upturned bicycle rather like this.
0:34:40 > 0:34:44The back wheel was modified so that a strong fishing line could be
0:34:44 > 0:34:49wound through the rim and pull along a meat-scented bag.
0:34:49 > 0:34:53As the cheetah ran the 80-yard or 73-metre course
0:34:53 > 0:34:54the pedals of the bike were hand-cranked
0:34:54 > 0:34:56as fast as humanly possible
0:34:56 > 0:35:00to drag the bag along just ahead of the cheetah.
0:35:00 > 0:35:06The measurements were made manually using a stopwatch and a pistol.
0:35:06 > 0:35:07Severin wrote that,
0:35:07 > 0:35:10"From a deep crouch, the cheetah spurted to
0:35:10 > 0:35:13"the end of the course in 2.25 seconds,
0:35:13 > 0:35:17"for an average speed of 71mph."
0:35:17 > 0:35:19And so, the legend was born.
0:35:19 > 0:35:22BIRDS SCREECH
0:35:22 > 0:35:25This impressive figure was immediately accepted
0:35:25 > 0:35:27and is still often quoted today,
0:35:27 > 0:35:30but how accurate is it?
0:35:30 > 0:35:33The top speed of any running mammal depends on the power
0:35:33 > 0:35:36of its muscles and the strength of its tendons and bones.
0:35:39 > 0:35:43Human athletes train hard to reach their personal best
0:35:43 > 0:35:46but there's still a limit to how fast they can run.
0:35:48 > 0:35:52In a 100m sprint, a mere two seconds separates
0:35:52 > 0:35:56a good amateur sprinter from a world-class champion.
0:35:57 > 0:36:01The greyhound is similar in size and shape to a cheetah
0:36:01 > 0:36:04so it's a good substitute animal to test out the cheetah's
0:36:04 > 0:36:07legendary top speed of 70mph.
0:36:12 > 0:36:15Their backs flex and extend so greatly that,
0:36:15 > 0:36:18at times, none of their feet touch the ground...
0:36:22 > 0:36:25..but when the greyhound's top speed was measured,
0:36:25 > 0:36:28it was found to be 45mph -
0:36:28 > 0:36:31a whole 25mph slower than the cheetah.
0:36:36 > 0:36:39People argued that the cheetah could nonetheless achieve
0:36:39 > 0:36:43a bigger stride because of extra flexibility in its back...
0:36:47 > 0:36:50..but doubts about its top speed were beginning to creep in.
0:36:50 > 0:36:54A new, more accurate way of testing was needed.
0:36:56 > 0:36:59Here in the Royal Veterinary College,
0:36:59 > 0:37:02they use dogs to help them in their studies of cheetahs.
0:37:02 > 0:37:05Using a lurcher as a stand-in,
0:37:05 > 0:37:09they've developed an extraordinary data-collecting collar.
0:37:09 > 0:37:13It has a GPS attachment that will register position
0:37:13 > 0:37:15to within a fraction of a metre.
0:37:15 > 0:37:20It has movement sensors to show how the animal is, in fact, moving.
0:37:20 > 0:37:22It can be remotely programmed
0:37:22 > 0:37:26and it has a solar-charged battery that will last for up to a year.
0:37:28 > 0:37:31The collars were tested and perfected on lurchers in Britain
0:37:31 > 0:37:34to make sure that they were small and light enough
0:37:34 > 0:37:36not to disturb their wearer.
0:37:38 > 0:37:41Then, the collars were put on captive cheetahs,
0:37:41 > 0:37:44to see if they could cope with the twisting run of the hunt.
0:37:49 > 0:37:50The results were excellent,
0:37:50 > 0:37:53and the collars were ready for the ultimate test...
0:37:53 > 0:37:56in the wild. CHEETAH PANTS
0:37:56 > 0:37:59FLIES BUZZ
0:37:59 > 0:38:03Here was a chance to see if a wild cheetah's special adaptations
0:38:03 > 0:38:08to hunting really enabled it to run at 70mph.
0:38:10 > 0:38:14Wild cheetahs are faster than other, larger cats, like lions,
0:38:14 > 0:38:16because of their lighter bones -
0:38:16 > 0:38:19an advantage in a short, high-speed chase.
0:38:21 > 0:38:26They have big nostrils, so they can take in large amounts of oxygen,
0:38:26 > 0:38:30and an enlarged heart and lungs that increase circulation.
0:38:33 > 0:38:36Their long tails act like rudders to help them steer
0:38:36 > 0:38:38and assist their balance as they twist and turn.
0:38:38 > 0:38:40BIRDS SCREECH
0:38:40 > 0:38:43They need to be fast and manoeuvrable
0:38:43 > 0:38:46because the prey they hunt is extremely agile
0:38:46 > 0:38:49and able to change direction very quickly.
0:38:49 > 0:38:53A cheetah can mirror such changes of movements in an instant.
0:38:56 > 0:39:00But what would the GPS collars tell us about their speed?
0:39:03 > 0:39:06Data from the collars has revealed fascinating details
0:39:06 > 0:39:08about cheetahs' lives,
0:39:08 > 0:39:12how they hunt and exactly how fast they can run.
0:39:12 > 0:39:16The GPS measurements collected are accurate to within half a metre
0:39:16 > 0:39:20and can be precisely matched to satellite images of the area,
0:39:20 > 0:39:24so it's possible to see exactly what kind of terrain the cheetahs
0:39:24 > 0:39:25were hunting on.
0:39:25 > 0:39:29Here, we can see an 11-hour day in the life of a cheetah,
0:39:29 > 0:39:33and there it starts to hunt.
0:39:33 > 0:39:38The cheetah ran in one circular direction,
0:39:38 > 0:39:40like this.
0:39:40 > 0:39:42The blue represents deceleration,
0:39:42 > 0:39:44getting slower here,
0:39:44 > 0:39:48and there, at the red, where it gets faster and accelerates,
0:39:48 > 0:39:52and the arrows represent the power of the force on the cheetah's body
0:39:52 > 0:39:55as it swerves, and there, finally,
0:39:55 > 0:39:58it made the kill.
0:39:58 > 0:40:01367 hunts were studied
0:40:01 > 0:40:06and the top speed of a chase was calculated to be 58mph.
0:40:06 > 0:40:09BIRDS SCREECH
0:40:13 > 0:40:15For more than half a century,
0:40:15 > 0:40:18we have overestimated the cheetah's speed.
0:40:20 > 0:40:24It is, nonetheless, still the fastest animal on land,
0:40:24 > 0:40:28and its greatest feat is its acceleration -
0:40:28 > 0:40:31four times that of Usain Bolt.
0:40:35 > 0:40:37CHEETAH GROWLS
0:40:39 > 0:40:42BIRDS SCREECH
0:40:42 > 0:40:44CHEETAH SNARLS
0:41:03 > 0:41:08The cheetah's legendary 70mph speed record is just a myth
0:41:08 > 0:41:13but their true top speed of 58mph is still extraordinary.
0:41:13 > 0:41:17A body that is fine-tuned for hunting helps them run in a really
0:41:17 > 0:41:23remarkable way, but the cheetah's real impossible feat, so-called...
0:41:23 > 0:41:26CHEETAH PURRS
0:41:28 > 0:41:32..is the ability to change speeds so extremely quickly,
0:41:32 > 0:41:36and that makes it one of the most manoeuvrable animals alive.
0:41:36 > 0:41:38Aren't you? Aren't you?
0:41:38 > 0:41:40CHEETAH PURRS
0:41:42 > 0:41:45We may have overestimated the abilities of the flea
0:41:45 > 0:41:50and the cheetah, but both exhibit remarkable feats of acceleration
0:41:50 > 0:41:52in their quest for food -
0:41:52 > 0:41:55the flea, to hop onto a passing host,
0:41:55 > 0:41:58and the cheetah, to outmanoeuvre its prey.
0:41:58 > 0:42:01BIRDS SCREECH