Why do some animals advertise themselves 0:00:03 0:00:06

with bold patterns or dazzling colours? 0:00:06 0:00:09

I've been lucky enough, one way or another, 0:00:12 0:00:14

to meet some of our planet's most enchanting animals, 0:00:14 0:00:18

but some I find particularly intriguing. 0:00:18 0:00:22

We've known about some of these creatures for centuries. 0:00:23 0:00:27

Others, we have discovered more recently. 0:00:27 0:00:30

In this series, I share their stories 0:00:30 0:00:34

and reveal why they really are natural curiosities. 0:00:34 0:00:39

The natural world is full of colours and patterns. 0:00:47 0:00:52

For most of us, many animals are simply beautiful, 0:00:52 0:00:55

sometimes so beautiful they become highly collectable. 0:00:55 0:01:00

But what role do colours and patterns play 0:01:01 0:01:05

in the lives of the animals that display them? 0:01:05 0:01:08

The zebra 0:01:12 0:01:14

has stripes unlike any other mammal. 0:01:14 0:01:17

When they first became widely known outside Africa, 0:01:17 0:01:21

during the 18th century, they were much-prized pets 0:01:21 0:01:24

in menageries of the nobility and royalty. 0:01:24 0:01:28

But while they fascinated the public, they baffled scientists. 0:01:28 0:01:32

What on earth could be the function of these extraordinary stripes? 0:01:32 0:01:37

Well, the answers that have been suggested over the centuries 0:01:37 0:01:42

have been truly astounding. 0:01:42 0:01:43

To begin with, all that was known about zebras 0:01:43 0:01:47

was that they lived in herds on the vast plains of Africa. 0:01:47 0:01:52

But as zebras became more familiar to European society 0:01:52 0:01:55

we began to learn more. 0:01:55 0:01:58

One particular zebra became something of a celebrity 0:01:59 0:02:02

in Georgian England, 0:02:02 0:02:04

so much so that it was painted 0:02:04 0:02:06

by the famous racehorse painter, George Stubbs. 0:02:06 0:02:09

This is a copy of his picture. 0:02:09 0:02:11

It was a belated wedding present to Queen Charlotte 0:02:11 0:02:14

from her husband, King George III, 0:02:14 0:02:17

and it actually lived in the grounds of Buckingham House, 0:02:17 0:02:20

as Buckingham Palace was then known. 0:02:20 0:02:22

Queen Charlotte was a passionate collector of exotic animals 0:02:24 0:02:29

and the zebra soon became the most famous animal in her collection, 0:02:29 0:02:34

attracting crowds of visitors. 0:02:34 0:02:36

Georgian London was not unfamiliar with bizarre and exotic creatures. 0:02:36 0:02:40

Many curiosities were being sent back 0:02:40 0:02:43

from the expanding British Empire. 0:02:43 0:02:45

But the strange striped horse was particularly intriguing. 0:02:45 0:02:50

Early zebra collectors, in trying to tame them, 0:02:50 0:02:54

stumbled upon one possible reason for their stripes. 0:02:54 0:02:58

Queen Charlotte wasn't the only famous European 0:02:58 0:03:01

to be fanatical about zebras. 0:03:01 0:03:04

So was this gentleman, Lord Clive of India, 0:03:04 0:03:08

the British Army officer who established British interest there 0:03:08 0:03:12

in the 18th century. 0:03:12 0:03:14

He actually owned two, a male and a female, 0:03:14 0:03:17

and so keen was he to try and get a zebra that would be tameable, 0:03:17 0:03:21

he tried to mate his female zebra with a male donkey. 0:03:21 0:03:25

To make the male donkey more attractive to the female, 0:03:25 0:03:29

believe it or not, he painted it with stripes - 0:03:29 0:03:32

and the experiment was a success. 0:03:32 0:03:35

In due course, the female zebra produced a foal. 0:03:35 0:03:39

As this old newsreel shows, 0:03:39 0:03:41

the offspring of such unions are partially striped. 0:03:41 0:03:46

They're also sometimes fertile. 0:03:46 0:03:48

Lord Clive's success in producing one 0:03:49 0:03:52

might suggest that the stripes are indeed important 0:03:52 0:03:55

in making one partner attractive to the other. 0:03:55 0:03:57

Charles Darwin built on that idea. 0:03:59 0:04:02

He noticed that each individual zebra 0:04:02 0:04:05

had its own unique stripe pattern. 0:04:05 0:04:08

He suggested that the stripes were a way for individuals 0:04:08 0:04:12

to recognise each other during courtship. 0:04:12 0:04:15

Occasionally, however, a zebra appeared with a coat pattern so odd 0:04:15 0:04:20

that it challenged that explanation. 0:04:20 0:04:22

In 1968, a picture of a very strange zebra appeared in the press. 0:04:24 0:04:30

It's fair to say that this animal is dotted, rather than striped, 0:04:30 0:04:33

and that could give us an insight 0:04:33 0:04:35

into the function of its coat patterns. 0:04:35 0:04:38

If it's to do with social cohesion 0:04:38 0:04:41

then you would expect that such a strange creature 0:04:41 0:04:43

would be shunned by the rest of the herd, 0:04:43 0:04:46

but that was not so. 0:04:46 0:04:47

It was treated just like any other member. 0:04:47 0:04:51

So maybe its coat patterns 0:04:51 0:04:53

are not primarily to do with social cohesion. 0:04:53 0:04:57

Other theories suggest the stripes play an important role 0:04:57 0:05:02

in defence against predators. 0:05:02 0:05:03

But how? 0:05:03 0:05:05

It's been claimed that the moving striped bodies of a herd of zebras 0:05:05 0:05:08

confuse a lion, making it difficult for it to judge distance, 0:05:08 0:05:12

and so time its pounce. 0:05:12 0:05:15

Others have argued that the stripes break up the zebras' outlines, 0:05:15 0:05:20

so they're hard to spot, especially amongst vegetation. 0:05:20 0:05:24

However, research comparing the zebra and the tiger 0:05:24 0:05:28

concluded that, while a tiger's stripes makes it 0:05:28 0:05:31

blend with its background, at least to our eyes, 0:05:31 0:05:34

the regular spacing of the zebra's stripes 0:05:34 0:05:37

actually make it more conspicuous. 0:05:37 0:05:39

The bold stripes of Queen Charlotte's zebra 0:05:39 0:05:43

drew huge crowds to Buckingham Palace, 0:05:43 0:05:46

but the animal itself was proving to be quite a handful. 0:05:46 0:05:50

The Queen's lone pet was a somewhat temperamental animal and its 0:05:51 0:05:55

keepers had to warn spectators that it was likely to kick and bite. 0:05:55 0:06:00

And that's hardly surprising, bearing in mind the strange food 0:06:00 0:06:04

it was given, which was a mixture of raw meat and tobacco - 0:06:04 0:06:08

hardly the sort of thing to give to a grazing animal. 0:06:08 0:06:12

It also became a way of lampooning the royal family. 0:06:12 0:06:16

The animal itself was known as the Queen's Ass, and its stripes 0:06:16 0:06:21

were used to indicate the king and queen's son, Prince George. 0:06:21 0:06:26

The Victorians continued the Georgian obsession 0:06:28 0:06:31

with taming zebras, but they had a practical reason for doing so. 0:06:31 0:06:36

A reason that may provide another explanation for the stripes - flies. 0:06:36 0:06:43

Flies carry fatal diseases that affect both humans and cattle, 0:06:43 0:06:49

and one of the most dangerous in Africa is the tsetse fly. 0:06:49 0:06:54

It spreads a disease called sleeping sickness that kills people, 0:06:54 0:06:57

cattle and horses. 0:06:57 0:06:59

Early Victorian settlers noticed that, while their domestic 0:07:00 0:07:05

horses fell ill from sleeping sickness, zebras were not affected. 0:07:05 0:07:10

So they set about taming them. 0:07:10 0:07:13

Over the years, many people have attempted to tame zebras, but the 0:07:13 0:07:18

efforts of one Victorian eccentric were particularly spectacular. 0:07:18 0:07:23

These zebras were once part of a menagerie of a Victorian aristocrat, 0:07:24 0:07:28

who became obsessed with taming them. 0:07:28 0:07:30

Walter Rothschild was a member of the great Rothschild 0:07:30 0:07:33

banking family, but he wasn't much good as a banker. 0:07:33 0:07:37

His main passion was for wildlife. 0:07:37 0:07:39

And he had a particular fondness 0:07:39 0:07:41

of zebras and spent a great deal of time and effort training them. 0:07:41 0:07:46

Rothschild succeeded where others failed. 0:07:56 0:07:58

This extraordinary photograph shows him on a journey 0:07:58 0:08:01

to Buckingham Palace, with his carriage being drawn by tame zebras. 0:08:01 0:08:06

It was a time-consuming process. 0:08:06 0:08:08

He trained each zebra individually, using a small carriage. 0:08:08 0:08:12

And they didn't take easily to being bridled, 0:08:12 0:08:15

but eventually all three of his zebras, and a pony, 0:08:15 0:08:18

pulled his carriage all the way through London to Buckingham Palace. 0:08:18 0:08:22

It must have been a strange spectacle to anybody passing by, 0:08:22 0:08:25

but perhaps they didn't notice the zebras. 0:08:25 0:08:28

Walter's brother Charles remarked that the stripes of the zebra 0:08:28 0:08:32

made them almost disappear as they travelled through the city streets. 0:08:32 0:08:36

Despite Rothschild's efforts, zebras never really became 0:08:36 0:08:41

an alternative to the horse in England or in Africa. 0:08:41 0:08:45

The observation by those early settlers, that zebras seemed 0:08:47 0:08:52

immune to the bites of tsetse flies, was not entirely correct. 0:08:52 0:08:56

Zebras can be bitten by flies 0:08:56 0:08:58

and can suffer the same sickness as the domestic horse. 0:08:58 0:09:02

But nonetheless, evidence suggests they attract fewer flies. 0:09:02 0:09:07

Some scientists have theorised that the zebra's stripes may in some way 0:09:08 0:09:13

make it more difficult for biting flies to land on a zebra's body. 0:09:13 0:09:19

To test this theory, a number of Hungarian scientists 0:09:19 0:09:22

took four horse-shaped models. 0:09:22 0:09:26

One they painted black, another they painted brown, the third was white 0:09:26 0:09:30

and the fourth was painted with the stripes of a zebra. 0:09:30 0:09:35

Then they put these four models in a field 0:09:35 0:09:38

and covered them with sticky glue. 0:09:38 0:09:43

Then, after a certain length of time, they went 0:09:43 0:09:45

and counted the number of flies that had landed on the different bodies 0:09:45 0:09:49

And believe it or not, there were fewest flies on the zebra's body. 0:09:49 0:09:55

How could this be? 0:09:56 0:09:57

Well, an insect's eyes are compound, they have a lot of elements in them, 0:09:57 0:10:02

and they navigate using horizontally polarised light. And it may be that 0:10:02 0:10:08

the stripes of the zebra in some way disrupt that polarised light and 0:10:08 0:10:13

make it much more difficult for the flies to land on the zebra's body. 0:10:13 0:10:19

These recent findings 0:10:19 0:10:22

do not prove definitively why zebras got their stripes. 0:10:22 0:10:26

There could be several other benefits. 0:10:26 0:10:28

But they do suggest that the stripes are more about avoiding 0:10:28 0:10:31

being bitten, rather than avoiding being eaten. 0:10:31 0:10:35

Whatever the biological reason for its stripes, 0:10:35 0:10:39

zebras have fascinated us for centuries. 0:10:39 0:10:41

Queen Charlotte was so besotted by hers 0:10:41 0:10:45

that eventually she bought another. 0:10:45 0:10:47

The first had proved to be so ill-tempered 0:10:47 0:10:49

that she sold it to a friend of King George III. 0:10:49 0:10:53

From there, it went to a travelling menagerie and when it died, 0:10:53 0:10:58

its body was stuffed and put on display 0:10:58 0:11:00

in the Blue Boar Inn in York, 0:11:00 0:11:02

something of a come-down from the grounds of Buckingham House. 0:11:02 0:11:08

The zebra has taken a basic striped pattern and stuck with it. 0:11:10 0:11:15

Our second patterned animal has done quite the opposite 0:11:16 0:11:20

and has produced thousands, if not millions, of variations on a theme. 0:11:20 0:11:25

Victorian naturalists seemed to have been obsessed with butterflies. 0:11:28 0:11:31

Their assembled specimens fill the cabinets of many a museum. 0:11:34 0:11:38

London's Natural History Museum has over three million of them, alone. 0:11:38 0:11:44

And it's easy to see why those naturalists were so obsessed. 0:11:44 0:11:48

Butterflies are so astonishingly varied and stunningly beautiful. 0:11:48 0:11:52

When it comes to pattern, 0:11:52 0:11:54

nature seems to have excelled herself with the butterfly wing. 0:11:54 0:11:59

Why nature has refashioned the wing into so many 0:12:02 0:12:06

different patterns has long fascinated science. 0:12:06 0:12:09

The vast majority of the specimens here come from the Victorian era, 0:12:09 0:12:15

a period when a passion for amateur collecting reached its peak. 0:12:15 0:12:20

Many of those early collectors 0:12:22 0:12:24

recognised the relationship between the colour and pattern 0:12:24 0:12:27

of a butterfly's wing, and its identity as a species. 0:12:27 0:12:31

Each species has its own signature pattern and hue. 0:12:32 0:12:36

Magnifying a wing shows how these patterns are created. 0:12:37 0:12:42

The surface is covered with millions of tiny scales. 0:12:42 0:12:48

They're made of chitin 0:12:48 0:12:49

and contain different pigments, that tend to fade. 0:12:49 0:12:52

But there is another kind of wing colouration that gives 0:12:53 0:12:57

some butterflies a particular spectacular brilliance. 0:12:57 0:13:00

And this remains long after the butterfly is dead. 0:13:00 0:13:03

These Morpho butterflies were collected over 100 years ago 0:13:05 0:13:10

and they are as bright today as the day on which they were collected. 0:13:10 0:13:16

That is because their wings contain tiny microscopic structures 0:13:16 0:13:21

called gyroids. 0:13:21 0:13:24

When the light hits one of them, it is bent and refracted, 0:13:24 0:13:29

so that the colour it produces varies, 0:13:29 0:13:32

according to the angle on which you look at it. 0:13:32 0:13:35

The gyroid, in fact, is not a pigment, which would fade, 0:13:35 0:13:40

it's a crystal structure. 0:13:40 0:13:42

Darwin pondered on the reason for such bright colours. 0:13:44 0:13:49

They could, after all, make the butterfly 0:13:49 0:13:51

highly visible to predators. So why be so colourful? 0:13:51 0:13:55

Victorian naturalists were aware that male and female butterflies 0:13:55 0:13:59

of the same species could be very different in colour. 0:13:59 0:14:02

The male Large Blue is, indeed, blue, 0:14:02 0:14:05

but the female, on the other hand, is a drab brown. 0:14:05 0:14:09

For Darwin, such species were a perfect example of a process 0:14:09 0:14:12

he called "sexual selection". 0:14:12 0:14:14

A colour or pattern arises among males that is attractive 0:14:14 0:14:18

to the opposite sex, 0:14:18 0:14:20

so the most brightly-coloured male is more likely to get a mate. 0:14:20 0:14:26

Remarkably, it's sometimes possible to see the male colouration 0:14:26 0:14:31

and female colouration in a single, individual butterfly, 0:14:31 0:14:35

like this one. 0:14:35 0:14:37

That side is female and that's male. 0:14:40 0:14:43

Such individuals are called gynandromorphs 0:14:43 0:14:46

and they're extremely rare. 0:14:46 0:14:48

They're also infertile, but, nonetheless, 0:14:48 0:14:52

they can reveal a great deal about sex and colouration in butterflies. 0:14:52 0:14:58

Studying the genetics of gynadromorphs 0:15:02 0:15:05

has enabled scientists to understand the role male and female genes 0:15:05 0:15:09

play in the development of wing colour and shape. 0:15:09 0:15:12

But why should it be the females who are drab 0:15:14 0:15:17

and the males more colourful? 0:15:17 0:15:19

That's because, in such species, males are territorial 0:15:22 0:15:26

and bright colours, visible from a distance, keep other males away. 0:15:26 0:15:30

The females, on the other hand, are egg layers, 0:15:32 0:15:36

and it's often better for them to be less conspicuous. 0:15:36 0:15:39

But not all butterflies show such clear differences between the sexes. 0:15:41 0:15:45

I once visited the winter home of the Monarch butterfly in Mexico. 0:15:45 0:15:50

Here, tens of millions of butterflies, having left 0:15:50 0:15:53

North America, to escape the winter, cluster together on trees. 0:15:53 0:15:59

Males and females are hardly any different. 0:15:59 0:16:02

Both are bright orange, with black stripes. 0:16:02 0:16:05

It's a magnificent spectacle, 0:16:07 0:16:09

and one might think that, with all these butterflies in one place, 0:16:09 0:16:12

they would be a feast for predators. But remarkably, few animals 0:16:12 0:16:18

are able to eat Monarch butterflies, because they are poisonous. 0:16:18 0:16:22

Today, our understanding of wing pattern and colour, 0:16:24 0:16:27

as a means of defence, is largely due to the work 0:16:27 0:16:30

of one of those impressive Victorian butterfly collectors. 0:16:30 0:16:34

In 1848, a young British naturalist, called Henry Bates, 0:16:34 0:16:38

began a collecting expedition to the Amazon 0:16:38 0:16:41

that would continue for 11 years. 0:16:41 0:16:43

Bates was of humble origin and largely self-educated, 0:16:43 0:16:48

so he was rather different from other scholars of the time. 0:16:48 0:16:52

He travelled to the Amazon with fellow naturalist, 0:16:52 0:16:55

Alfred Russell Wallace, who wrote that the aim of their journey 0:16:55 0:16:58

wasn't just to collect, but to "gather facts towards solving 0:16:58 0:17:02

"the problem of the origin of species." 0:17:02 0:17:05

He stayed on the Amazon for more than a decade 0:17:05 0:17:08

and amassed thousands of specimens, as well as discovering more than 0:17:08 0:17:12

100 new species of butterfly. 0:17:12 0:17:15

His work wasn't just an insight 0:17:15 0:17:16

into the diversity of life in the tropics. 0:17:16 0:17:18

It was his theory on butterfly colouration that would 0:17:18 0:17:22

bring him to the attention of the great Charles Darwin. 0:17:22 0:17:26

He recorded differences in butterfly behaviour. 0:17:27 0:17:31

Some species flew in a purposeful way. 0:17:31 0:17:35

Others were slow, and fluttery, fliers, 0:17:35 0:17:39

Yet they were left largely alone, despite their conspicuous markings. 0:17:39 0:17:43

Bates was aware that some of the butterflies in his collection 0:17:45 0:17:48

were distasteful to predators. 0:17:48 0:17:50

He knew from his time in the Amazon that some species, like these 0:17:50 0:17:53

on the left, avoid predation because they contain poisons. 0:17:53 0:17:58

But here was a butterfly that was almost identical, but not quite. 0:17:58 0:18:04

In fact, it belongs to a totally different group. 0:18:04 0:18:08

As he worked through his huge collection, he began to see a trend. 0:18:08 0:18:12

Each poisonous, or distasteful, species of butterfly 0:18:12 0:18:16

had a matching copycat and he drew them side by side in his book. 0:18:16 0:18:22

He called these copycats mimics. 0:18:22 0:18:26

Bates had stumbled upon a different reason for butterfly patterns, 0:18:26 0:18:31

one where colours are a warning sign of danger to would-be predators. 0:18:31 0:18:36

Those mimics with a similar wing pattern to the distasteful species 0:18:36 0:18:41

were more likely to be avoided by predators. 0:18:41 0:18:44

Those that looked less convincing were more likely to be killed. 0:18:44 0:18:47

So, over time, evolution causes these copycats to be 0:18:47 0:18:51

almost identical in pattern and colour to the model they mimic. 0:18:51 0:18:56

Darwin was delighted with Bates' observations. 0:18:56 0:19:00

The butterfly wing pattern 0:19:00 0:19:01

fitted nicely into his new theory of evolution. 0:19:01 0:19:04

Bates also discovered that the wing pattern of a butterfly 0:19:04 0:19:09

could vary over distance. 0:19:09 0:19:12

This is the butterfly called Heliconius, 0:19:12 0:19:15

and this is what it looks like in the south of the Amazon basin. 0:19:15 0:19:19

But this is what it looks like in the north. 0:19:19 0:19:23

But, even more remarkably, he also discovered that the mimic 0:19:23 0:19:28

varies in the same sort of way. 0:19:28 0:19:31

That is what the mimic looks like in the south 0:19:31 0:19:35

and this is what it looks like in the north. 0:19:35 0:19:39

While Bates explained the importance of wing pattern in anti-predation, 0:19:41 0:19:45

there was one question he was never able to answer... 0:19:45 0:19:48

..how did the mimic avoid mating with the model? 0:19:50 0:19:54

After all, they're almost identical, to our eyes, at any rate. 0:19:54 0:20:00

We now know that many butterflies can see a much broader band 0:20:00 0:20:05

of the light spectrum, even the ultraviolet end. 0:20:05 0:20:09

This Heliconius butterfly on the left is closely matched 0:20:09 0:20:14

by its mimic, on the right. 0:20:14 0:20:16

To our eyes, they look very similar, but view them in ultraviolet, 0:20:16 0:20:21

and we can see that, now, the mimic is more drab and darker. 0:20:21 0:20:25

So butterflies themselves 0:20:25 0:20:27

can see the difference more easily than we can. 0:20:27 0:20:30

The evolution of wing pattern in butterflies 0:20:33 0:20:35

is clearly more complex than those early Victorian collectors 0:20:35 0:20:39

could have imagined. 0:20:39 0:20:41

Indeed, many different factors may play a role in shaping 0:20:41 0:20:45

the colour and pattern of each species' wing. 0:20:45 0:20:49

But we have Henry Bates to thank for revealing the connection 0:20:49 0:20:52

between colour and defence. 0:20:52 0:20:55

When Henry Bates returned from the Amazon, 0:20:55 0:20:58

he described his 11 years in the tropics as the best of his life. 0:20:58 0:21:03

He would spend the remainder of his career 0:21:03 0:21:05

working as Assistant Secretary to the Royal Geographical Society, 0:21:05 0:21:09

a job that really didn't stretch his amazing scientific mind. 0:21:09 0:21:13

Many collectors have contributed butterfly specimens 0:21:13 0:21:17

to this impressive collection in the Natural History Museum, 0:21:17 0:21:20

but thanks to Bates, we are able to see beyond 0:21:20 0:21:23

the dazzling variety of wing colours and find the evolutionary connection 0:21:23 0:21:27

between the many different patterns on the butterfly wing. 0:21:27 0:21:31

So, the striped coat of the zebra 0:21:31 0:21:35

and the colourful markings of a butterfly's wing 0:21:35 0:21:38

may play similar roles, 0:21:38 0:21:41

helping protect the animals they decorate. 0:21:41 0:21:43