0:00:03 > 0:00:06Why do some animals advertise themselves
0:00:06 > 0:00:09with bold patterns or dazzling colours?
0:00:12 > 0:00:14I've been lucky enough, one way or another,
0:00:14 > 0:00:18to meet some of our planet's most enchanting animals,
0:00:18 > 0:00:22but some I find particularly intriguing.
0:00:23 > 0:00:27We've known about some of these creatures for centuries.
0:00:27 > 0:00:30Others, we have discovered more recently.
0:00:30 > 0:00:34In this series, I share their stories
0:00:34 > 0:00:39and reveal why they really are natural curiosities.
0:00:47 > 0:00:52The natural world is full of colours and patterns.
0:00:52 > 0:00:55For most of us, many animals are simply beautiful,
0:00:55 > 0:01:00sometimes so beautiful they become highly collectable.
0:01:01 > 0:01:05But what role do colours and patterns play
0:01:05 > 0:01:08in the lives of the animals that display them?
0:01:12 > 0:01:14The zebra
0:01:14 > 0:01:17has stripes unlike any other mammal.
0:01:17 > 0:01:21When they first became widely known outside Africa,
0:01:21 > 0:01:24during the 18th century, they were much-prized pets
0:01:24 > 0:01:28in menageries of the nobility and royalty.
0:01:28 > 0:01:32But while they fascinated the public, they baffled scientists.
0:01:32 > 0:01:37What on earth could be the function of these extraordinary stripes?
0:01:37 > 0:01:42Well, the answers that have been suggested over the centuries
0:01:42 > 0:01:43have been truly astounding.
0:01:43 > 0:01:47To begin with, all that was known about zebras
0:01:47 > 0:01:52was that they lived in herds on the vast plains of Africa.
0:01:52 > 0:01:55But as zebras became more familiar to European society
0:01:55 > 0:01:58we began to learn more.
0:01:59 > 0:02:02One particular zebra became something of a celebrity
0:02:02 > 0:02:04in Georgian England,
0:02:04 > 0:02:06so much so that it was painted
0:02:06 > 0:02:09by the famous racehorse painter, George Stubbs.
0:02:09 > 0:02:11This is a copy of his picture.
0:02:11 > 0:02:14It was a belated wedding present to Queen Charlotte
0:02:14 > 0:02:17from her husband, King George III,
0:02:17 > 0:02:20and it actually lived in the grounds of Buckingham House,
0:02:20 > 0:02:22as Buckingham Palace was then known.
0:02:24 > 0:02:29Queen Charlotte was a passionate collector of exotic animals
0:02:29 > 0:02:34and the zebra soon became the most famous animal in her collection,
0:02:34 > 0:02:36attracting crowds of visitors.
0:02:36 > 0:02:40Georgian London was not unfamiliar with bizarre and exotic creatures.
0:02:40 > 0:02:43Many curiosities were being sent back
0:02:43 > 0:02:45from the expanding British Empire.
0:02:45 > 0:02:50But the strange striped horse was particularly intriguing.
0:02:50 > 0:02:54Early zebra collectors, in trying to tame them,
0:02:54 > 0:02:58stumbled upon one possible reason for their stripes.
0:02:58 > 0:03:01Queen Charlotte wasn't the only famous European
0:03:01 > 0:03:04to be fanatical about zebras.
0:03:04 > 0:03:08So was this gentleman, Lord Clive of India,
0:03:08 > 0:03:12the British Army officer who established British interest there
0:03:12 > 0:03:14in the 18th century.
0:03:14 > 0:03:17He actually owned two, a male and a female,
0:03:17 > 0:03:21and so keen was he to try and get a zebra that would be tameable,
0:03:21 > 0:03:25he tried to mate his female zebra with a male donkey.
0:03:25 > 0:03:29To make the male donkey more attractive to the female,
0:03:29 > 0:03:32believe it or not, he painted it with stripes -
0:03:32 > 0:03:35and the experiment was a success.
0:03:35 > 0:03:39In due course, the female zebra produced a foal.
0:03:39 > 0:03:41As this old newsreel shows,
0:03:41 > 0:03:46the offspring of such unions are partially striped.
0:03:46 > 0:03:48They're also sometimes fertile.
0:03:49 > 0:03:52Lord Clive's success in producing one
0:03:52 > 0:03:55might suggest that the stripes are indeed important
0:03:55 > 0:03:57in making one partner attractive to the other.
0:03:59 > 0:04:02Charles Darwin built on that idea.
0:04:02 > 0:04:05He noticed that each individual zebra
0:04:05 > 0:04:08had its own unique stripe pattern.
0:04:08 > 0:04:12He suggested that the stripes were a way for individuals
0:04:12 > 0:04:15to recognise each other during courtship.
0:04:15 > 0:04:20Occasionally, however, a zebra appeared with a coat pattern so odd
0:04:20 > 0:04:22that it challenged that explanation.
0:04:24 > 0:04:30In 1968, a picture of a very strange zebra appeared in the press.
0:04:30 > 0:04:33It's fair to say that this animal is dotted, rather than striped,
0:04:33 > 0:04:35and that could give us an insight
0:04:35 > 0:04:38into the function of its coat patterns.
0:04:38 > 0:04:41If it's to do with social cohesion
0:04:41 > 0:04:43then you would expect that such a strange creature
0:04:43 > 0:04:46would be shunned by the rest of the herd,
0:04:46 > 0:04:47but that was not so.
0:04:47 > 0:04:51It was treated just like any other member.
0:04:51 > 0:04:53So maybe its coat patterns
0:04:53 > 0:04:57are not primarily to do with social cohesion.
0:04:57 > 0:05:02Other theories suggest the stripes play an important role
0:05:02 > 0:05:03in defence against predators.
0:05:03 > 0:05:05But how?
0:05:05 > 0:05:08It's been claimed that the moving striped bodies of a herd of zebras
0:05:08 > 0:05:12confuse a lion, making it difficult for it to judge distance,
0:05:12 > 0:05:15and so time its pounce.
0:05:15 > 0:05:20Others have argued that the stripes break up the zebras' outlines,
0:05:20 > 0:05:24so they're hard to spot, especially amongst vegetation.
0:05:24 > 0:05:28However, research comparing the zebra and the tiger
0:05:28 > 0:05:31concluded that, while a tiger's stripes makes it
0:05:31 > 0:05:34blend with its background, at least to our eyes,
0:05:34 > 0:05:37the regular spacing of the zebra's stripes
0:05:37 > 0:05:39actually make it more conspicuous.
0:05:39 > 0:05:43The bold stripes of Queen Charlotte's zebra
0:05:43 > 0:05:46drew huge crowds to Buckingham Palace,
0:05:46 > 0:05:50but the animal itself was proving to be quite a handful.
0:05:51 > 0:05:55The Queen's lone pet was a somewhat temperamental animal and its
0:05:55 > 0:06:00keepers had to warn spectators that it was likely to kick and bite.
0:06:00 > 0:06:04And that's hardly surprising, bearing in mind the strange food
0:06:04 > 0:06:08it was given, which was a mixture of raw meat and tobacco -
0:06:08 > 0:06:12hardly the sort of thing to give to a grazing animal.
0:06:12 > 0:06:16It also became a way of lampooning the royal family.
0:06:16 > 0:06:21The animal itself was known as the Queen's Ass, and its stripes
0:06:21 > 0:06:26were used to indicate the king and queen's son, Prince George.
0:06:28 > 0:06:31The Victorians continued the Georgian obsession
0:06:31 > 0:06:36with taming zebras, but they had a practical reason for doing so.
0:06:36 > 0:06:43A reason that may provide another explanation for the stripes - flies.
0:06:43 > 0:06:49Flies carry fatal diseases that affect both humans and cattle,
0:06:49 > 0:06:54and one of the most dangerous in Africa is the tsetse fly.
0:06:54 > 0:06:57It spreads a disease called sleeping sickness that kills people,
0:06:57 > 0:06:59cattle and horses.
0:07:00 > 0:07:05Early Victorian settlers noticed that, while their domestic
0:07:05 > 0:07:10horses fell ill from sleeping sickness, zebras were not affected.
0:07:10 > 0:07:13So they set about taming them.
0:07:13 > 0:07:18Over the years, many people have attempted to tame zebras, but the
0:07:18 > 0:07:23efforts of one Victorian eccentric were particularly spectacular.
0:07:24 > 0:07:28These zebras were once part of a menagerie of a Victorian aristocrat,
0:07:28 > 0:07:30who became obsessed with taming them.
0:07:30 > 0:07:33Walter Rothschild was a member of the great Rothschild
0:07:33 > 0:07:37banking family, but he wasn't much good as a banker.
0:07:37 > 0:07:39His main passion was for wildlife.
0:07:39 > 0:07:41And he had a particular fondness
0:07:41 > 0:07:46of zebras and spent a great deal of time and effort training them.
0:07:56 > 0:07:58Rothschild succeeded where others failed.
0:07:58 > 0:08:01This extraordinary photograph shows him on a journey
0:08:01 > 0:08:06to Buckingham Palace, with his carriage being drawn by tame zebras.
0:08:06 > 0:08:08It was a time-consuming process.
0:08:08 > 0:08:12He trained each zebra individually, using a small carriage.
0:08:12 > 0:08:15And they didn't take easily to being bridled,
0:08:15 > 0:08:18but eventually all three of his zebras, and a pony,
0:08:18 > 0:08:22pulled his carriage all the way through London to Buckingham Palace.
0:08:22 > 0:08:25It must have been a strange spectacle to anybody passing by,
0:08:25 > 0:08:28but perhaps they didn't notice the zebras.
0:08:28 > 0:08:32Walter's brother Charles remarked that the stripes of the zebra
0:08:32 > 0:08:36made them almost disappear as they travelled through the city streets.
0:08:36 > 0:08:41Despite Rothschild's efforts, zebras never really became
0:08:41 > 0:08:45an alternative to the horse in England or in Africa.
0:08:47 > 0:08:52The observation by those early settlers, that zebras seemed
0:08:52 > 0:08:56immune to the bites of tsetse flies, was not entirely correct.
0:08:56 > 0:08:58Zebras can be bitten by flies
0:08:58 > 0:09:02and can suffer the same sickness as the domestic horse.
0:09:02 > 0:09:07But nonetheless, evidence suggests they attract fewer flies.
0:09:08 > 0:09:13Some scientists have theorised that the zebra's stripes may in some way
0:09:13 > 0:09:19make it more difficult for biting flies to land on a zebra's body.
0:09:19 > 0:09:22To test this theory, a number of Hungarian scientists
0:09:22 > 0:09:26took four horse-shaped models.
0:09:26 > 0:09:30One they painted black, another they painted brown, the third was white
0:09:30 > 0:09:35and the fourth was painted with the stripes of a zebra.
0:09:35 > 0:09:38Then they put these four models in a field
0:09:38 > 0:09:43and covered them with sticky glue.
0:09:43 > 0:09:45Then, after a certain length of time, they went
0:09:45 > 0:09:49and counted the number of flies that had landed on the different bodies
0:09:49 > 0:09:55And believe it or not, there were fewest flies on the zebra's body.
0:09:56 > 0:09:57How could this be?
0:09:57 > 0:10:02Well, an insect's eyes are compound, they have a lot of elements in them,
0:10:02 > 0:10:08and they navigate using horizontally polarised light. And it may be that
0:10:08 > 0:10:13the stripes of the zebra in some way disrupt that polarised light and
0:10:13 > 0:10:19make it much more difficult for the flies to land on the zebra's body.
0:10:19 > 0:10:22These recent findings
0:10:22 > 0:10:26do not prove definitively why zebras got their stripes.
0:10:26 > 0:10:28There could be several other benefits.
0:10:28 > 0:10:31But they do suggest that the stripes are more about avoiding
0:10:31 > 0:10:35being bitten, rather than avoiding being eaten.
0:10:35 > 0:10:39Whatever the biological reason for its stripes,
0:10:39 > 0:10:41zebras have fascinated us for centuries.
0:10:41 > 0:10:45Queen Charlotte was so besotted by hers
0:10:45 > 0:10:47that eventually she bought another.
0:10:47 > 0:10:49The first had proved to be so ill-tempered
0:10:49 > 0:10:53that she sold it to a friend of King George III.
0:10:53 > 0:10:58From there, it went to a travelling menagerie and when it died,
0:10:58 > 0:11:00its body was stuffed and put on display
0:11:00 > 0:11:02in the Blue Boar Inn in York,
0:11:02 > 0:11:08something of a come-down from the grounds of Buckingham House.
0:11:10 > 0:11:15The zebra has taken a basic striped pattern and stuck with it.
0:11:16 > 0:11:20Our second patterned animal has done quite the opposite
0:11:20 > 0:11:25and has produced thousands, if not millions, of variations on a theme.
0:11:28 > 0:11:31Victorian naturalists seemed to have been obsessed with butterflies.
0:11:34 > 0:11:38Their assembled specimens fill the cabinets of many a museum.
0:11:38 > 0:11:44London's Natural History Museum has over three million of them, alone.
0:11:44 > 0:11:48And it's easy to see why those naturalists were so obsessed.
0:11:48 > 0:11:52Butterflies are so astonishingly varied and stunningly beautiful.
0:11:52 > 0:11:54When it comes to pattern,
0:11:54 > 0:11:59nature seems to have excelled herself with the butterfly wing.
0:12:02 > 0:12:06Why nature has refashioned the wing into so many
0:12:06 > 0:12:09different patterns has long fascinated science.
0:12:09 > 0:12:15The vast majority of the specimens here come from the Victorian era,
0:12:15 > 0:12:20a period when a passion for amateur collecting reached its peak.
0:12:22 > 0:12:24Many of those early collectors
0:12:24 > 0:12:27recognised the relationship between the colour and pattern
0:12:27 > 0:12:31of a butterfly's wing, and its identity as a species.
0:12:32 > 0:12:36Each species has its own signature pattern and hue.
0:12:37 > 0:12:42Magnifying a wing shows how these patterns are created.
0:12:42 > 0:12:48The surface is covered with millions of tiny scales.
0:12:48 > 0:12:49They're made of chitin
0:12:49 > 0:12:52and contain different pigments, that tend to fade.
0:12:53 > 0:12:57But there is another kind of wing colouration that gives
0:12:57 > 0:13:00some butterflies a particular spectacular brilliance.
0:13:00 > 0:13:03And this remains long after the butterfly is dead.
0:13:05 > 0:13:10These Morpho butterflies were collected over 100 years ago
0:13:10 > 0:13:16and they are as bright today as the day on which they were collected.
0:13:16 > 0:13:21That is because their wings contain tiny microscopic structures
0:13:21 > 0:13:24called gyroids.
0:13:24 > 0:13:29When the light hits one of them, it is bent and refracted,
0:13:29 > 0:13:32so that the colour it produces varies,
0:13:32 > 0:13:35according to the angle on which you look at it.
0:13:35 > 0:13:40The gyroid, in fact, is not a pigment, which would fade,
0:13:40 > 0:13:42it's a crystal structure.
0:13:44 > 0:13:49Darwin pondered on the reason for such bright colours.
0:13:49 > 0:13:51They could, after all, make the butterfly
0:13:51 > 0:13:55highly visible to predators. So why be so colourful?
0:13:55 > 0:13:59Victorian naturalists were aware that male and female butterflies
0:13:59 > 0:14:02of the same species could be very different in colour.
0:14:02 > 0:14:05The male Large Blue is, indeed, blue,
0:14:05 > 0:14:09but the female, on the other hand, is a drab brown.
0:14:09 > 0:14:12For Darwin, such species were a perfect example of a process
0:14:12 > 0:14:14he called "sexual selection".
0:14:14 > 0:14:18A colour or pattern arises among males that is attractive
0:14:18 > 0:14:20to the opposite sex,
0:14:20 > 0:14:26so the most brightly-coloured male is more likely to get a mate.
0:14:26 > 0:14:31Remarkably, it's sometimes possible to see the male colouration
0:14:31 > 0:14:35and female colouration in a single, individual butterfly,
0:14:35 > 0:14:37like this one.
0:14:40 > 0:14:43That side is female and that's male.
0:14:43 > 0:14:46Such individuals are called gynandromorphs
0:14:46 > 0:14:48and they're extremely rare.
0:14:48 > 0:14:52They're also infertile, but, nonetheless,
0:14:52 > 0:14:58they can reveal a great deal about sex and colouration in butterflies.
0:15:02 > 0:15:05Studying the genetics of gynadromorphs
0:15:05 > 0:15:09has enabled scientists to understand the role male and female genes
0:15:09 > 0:15:12play in the development of wing colour and shape.
0:15:14 > 0:15:17But why should it be the females who are drab
0:15:17 > 0:15:19and the males more colourful?
0:15:22 > 0:15:26That's because, in such species, males are territorial
0:15:26 > 0:15:30and bright colours, visible from a distance, keep other males away.
0:15:32 > 0:15:36The females, on the other hand, are egg layers,
0:15:36 > 0:15:39and it's often better for them to be less conspicuous.
0:15:41 > 0:15:45But not all butterflies show such clear differences between the sexes.
0:15:45 > 0:15:50I once visited the winter home of the Monarch butterfly in Mexico.
0:15:50 > 0:15:53Here, tens of millions of butterflies, having left
0:15:53 > 0:15:59North America, to escape the winter, cluster together on trees.
0:15:59 > 0:16:02Males and females are hardly any different.
0:16:02 > 0:16:05Both are bright orange, with black stripes.
0:16:07 > 0:16:09It's a magnificent spectacle,
0:16:09 > 0:16:12and one might think that, with all these butterflies in one place,
0:16:12 > 0:16:18they would be a feast for predators. But remarkably, few animals
0:16:18 > 0:16:22are able to eat Monarch butterflies, because they are poisonous.
0:16:24 > 0:16:27Today, our understanding of wing pattern and colour,
0:16:27 > 0:16:30as a means of defence, is largely due to the work
0:16:30 > 0:16:34of one of those impressive Victorian butterfly collectors.
0:16:34 > 0:16:38In 1848, a young British naturalist, called Henry Bates,
0:16:38 > 0:16:41began a collecting expedition to the Amazon
0:16:41 > 0:16:43that would continue for 11 years.
0:16:43 > 0:16:48Bates was of humble origin and largely self-educated,
0:16:48 > 0:16:52so he was rather different from other scholars of the time.
0:16:52 > 0:16:55He travelled to the Amazon with fellow naturalist,
0:16:55 > 0:16:58Alfred Russell Wallace, who wrote that the aim of their journey
0:16:58 > 0:17:02wasn't just to collect, but to "gather facts towards solving
0:17:02 > 0:17:05"the problem of the origin of species."
0:17:05 > 0:17:08He stayed on the Amazon for more than a decade
0:17:08 > 0:17:12and amassed thousands of specimens, as well as discovering more than
0:17:12 > 0:17:15100 new species of butterfly.
0:17:15 > 0:17:16His work wasn't just an insight
0:17:16 > 0:17:18into the diversity of life in the tropics.
0:17:18 > 0:17:22It was his theory on butterfly colouration that would
0:17:22 > 0:17:26bring him to the attention of the great Charles Darwin.
0:17:27 > 0:17:31He recorded differences in butterfly behaviour.
0:17:31 > 0:17:35Some species flew in a purposeful way.
0:17:35 > 0:17:39Others were slow, and fluttery, fliers,
0:17:39 > 0:17:43Yet they were left largely alone, despite their conspicuous markings.
0:17:45 > 0:17:48Bates was aware that some of the butterflies in his collection
0:17:48 > 0:17:50were distasteful to predators.
0:17:50 > 0:17:53He knew from his time in the Amazon that some species, like these
0:17:53 > 0:17:58on the left, avoid predation because they contain poisons.
0:17:58 > 0:18:04But here was a butterfly that was almost identical, but not quite.
0:18:04 > 0:18:08In fact, it belongs to a totally different group.
0:18:08 > 0:18:12As he worked through his huge collection, he began to see a trend.
0:18:12 > 0:18:16Each poisonous, or distasteful, species of butterfly
0:18:16 > 0:18:22had a matching copycat and he drew them side by side in his book.
0:18:22 > 0:18:26He called these copycats mimics.
0:18:26 > 0:18:31Bates had stumbled upon a different reason for butterfly patterns,
0:18:31 > 0:18:36one where colours are a warning sign of danger to would-be predators.
0:18:36 > 0:18:41Those mimics with a similar wing pattern to the distasteful species
0:18:41 > 0:18:44were more likely to be avoided by predators.
0:18:44 > 0:18:47Those that looked less convincing were more likely to be killed.
0:18:47 > 0:18:51So, over time, evolution causes these copycats to be
0:18:51 > 0:18:56almost identical in pattern and colour to the model they mimic.
0:18:56 > 0:19:00Darwin was delighted with Bates' observations.
0:19:00 > 0:19:01The butterfly wing pattern
0:19:01 > 0:19:04fitted nicely into his new theory of evolution.
0:19:04 > 0:19:09Bates also discovered that the wing pattern of a butterfly
0:19:09 > 0:19:12could vary over distance.
0:19:12 > 0:19:15This is the butterfly called Heliconius,
0:19:15 > 0:19:19and this is what it looks like in the south of the Amazon basin.
0:19:19 > 0:19:23But this is what it looks like in the north.
0:19:23 > 0:19:28But, even more remarkably, he also discovered that the mimic
0:19:28 > 0:19:31varies in the same sort of way.
0:19:31 > 0:19:35That is what the mimic looks like in the south
0:19:35 > 0:19:39and this is what it looks like in the north.
0:19:41 > 0:19:45While Bates explained the importance of wing pattern in anti-predation,
0:19:45 > 0:19:48there was one question he was never able to answer...
0:19:50 > 0:19:54..how did the mimic avoid mating with the model?
0:19:54 > 0:20:00After all, they're almost identical, to our eyes, at any rate.
0:20:00 > 0:20:05We now know that many butterflies can see a much broader band
0:20:05 > 0:20:09of the light spectrum, even the ultraviolet end.
0:20:09 > 0:20:14This Heliconius butterfly on the left is closely matched
0:20:14 > 0:20:16by its mimic, on the right.
0:20:16 > 0:20:21To our eyes, they look very similar, but view them in ultraviolet,
0:20:21 > 0:20:25and we can see that, now, the mimic is more drab and darker.
0:20:25 > 0:20:27So butterflies themselves
0:20:27 > 0:20:30can see the difference more easily than we can.
0:20:33 > 0:20:35The evolution of wing pattern in butterflies
0:20:35 > 0:20:39is clearly more complex than those early Victorian collectors
0:20:39 > 0:20:41could have imagined.
0:20:41 > 0:20:45Indeed, many different factors may play a role in shaping
0:20:45 > 0:20:49the colour and pattern of each species' wing.
0:20:49 > 0:20:52But we have Henry Bates to thank for revealing the connection
0:20:52 > 0:20:55between colour and defence.
0:20:55 > 0:20:58When Henry Bates returned from the Amazon,
0:20:58 > 0:21:03he described his 11 years in the tropics as the best of his life.
0:21:03 > 0:21:05He would spend the remainder of his career
0:21:05 > 0:21:09working as Assistant Secretary to the Royal Geographical Society,
0:21:09 > 0:21:13a job that really didn't stretch his amazing scientific mind.
0:21:13 > 0:21:17Many collectors have contributed butterfly specimens
0:21:17 > 0:21:20to this impressive collection in the Natural History Museum,
0:21:20 > 0:21:23but thanks to Bates, we are able to see beyond
0:21:23 > 0:21:27the dazzling variety of wing colours and find the evolutionary connection
0:21:27 > 0:21:31between the many different patterns on the butterfly wing.
0:21:31 > 0:21:35So, the striped coat of the zebra
0:21:35 > 0:21:38and the colourful markings of a butterfly's wing
0:21:38 > 0:21:41may play similar roles,
0:21:41 > 0:21:43helping protect the animals they decorate.
0:22:02 > 0:22:05Subtitles by Red Bee Media Ltd