Original subtitles

SIR DAVID ATTENBOROUGH: The natural world is full of colours

that we often take for granted.

There are few animals more brilliantly colored

than these scarlet macaws.

Animals can use color for all kinds of different reasons

and some have colours that we ourselves can't even see.

But not all colours are what they seem.

Some animals also use colours to hide.

Colours that make them disappear.

Colours that create optical illusions.

And colours that are used to trick and deceive.

To understand how these colours work,

we need to see them from an animal's perspective.

With the help of our specialist cameras,

we can now do that...

...and discover how some animals have become masters of disguise.

The Indian subcontinent is home to some truly spectacular animals.

PEAFOWL CALL

Most, like these peafowl, use color to attract attention

and the kinds they've developed

are influenced by the way they see the world.

But flashy colours can also come at a cost,

and sometimes it's better to remain out of sight.

So some animals use their colours

to help them hide and disappear into the background.

One such animal lives here in the forests of central India.

It's one of the most formidable hunters on earth.

A Bengal tiger. A female.

She's one of the world's biggest cats,

and remaining out of sight is not easy

when you are as large as she is.

Her orange and black coat is crucial to her success.

To have any chance of catching a meal,

she has to get to within a few metres of her prey.

She keeps to the cover of the trees

and slowly makes her approach.

She may appear conspicuous to our eyes,

but not so to these chiral deer.

Ch ital have only two types of color receptors in their eyes,

compared to our three,

which means that they are effectively blind to red and orange.

So to the deer, the tiger isn't orange at all.

This is how we see the world...

...and this is how the deer do.

The tiger's orange coat to them is a muted shade of green,

so it's nearly impossible for the deer to register.

She creeps closer.

The chiral don't see her.

The odds appear stacked in the tiger's favour.

But the deer aren't entirely defenseless.

They have help from an unusual ally.

Languor monkeys.

They're known as 'the eyes of the forest'

and their color vision is excellent.

Their eyes, like ours, have three types of color receptors

and they CAN see orange.

MONKEY GROWLS

The languors sounded the alarm before she could get close enough.

If the languors can easily spot her,

why then is the tiger orange at all?

Why isn't she green?

That's because mammals are unable to develop green pigments,

so it seems the next best solution for the tiger is to have orange fur,

which appears green to her main prey.

She will have to find a new target.

Down by the water, she finds one -

samba deer.

Samar don't keep company with monkeys.

They are on their own.

They have the same limited eyesight as the chiral,

but ears like satellite dishes.

If she treads on a twig and it snaps,

the hunt will be over before it began.

The deer seem to sense danger.

They still can't see her.

Despite her effective camouflage,

most hunts end like this.

Less than 10% of her attacks are successful.

But without her orange fur, her chances would be even lower.

It is her colours that are key to her survival.

The Cairn Mountains in Scotland.

Here there are special problems for the hunted.

Some animals have developed camouflage of such perfection

that they are virtually invisible against their surroundings.

But what happens when those surroundings change?

Well, then, of course, the animals have to change too.

These mountains are home to a particular kind of grouse

called the ptarmigan.

Their mottled brown feathers make them inconspicuous

among the rocks and heather.

But in winter,

these mountains are hard places in which to live.

Temperatures drop

and the land can overnight be covered by a blanket of snow.

Most birds by now have gone south to warmer parts of the world,

but not the ptarmigan.

When winter comes, they undergo the most extraordinary change.

They replace their brown feathers with pure white ones.

They do so for a simple reason -

they must go unnoticed.

They need to hide.

This open habitat makes the ptarmigan

very vulnerable to predators.

Being the right color is crucial.

Now they are invisible even to a keen-eyed eagle.

Ptarmigan are not the only animals to use this disappearing act.

So does the arctic fox...

...snowshoe hares...

...and weasels.

All, with the coming of winter, change their coats

and vanish from sight.

Their transformation is triggered by the decreasing daylight,

and over several weeks,

they replace their brown costumes with white ones.

So, changing color with the seasons,

for some animals,

is the only way to avoid becoming a meal.

But many plants, of course, do the reverse.

In spring, they produce color

to declare that are providing food - nectar.

Bees and many other insects love it.

In spring and summer,

they travel busily from flower to flower collecting it.

And when the bees leave to look for more,

they inadvertently take pollen with them,

which then fertilizes the next flowers they visit.

But there's a hunter here that exploits this relationship.

A crab spider.

She's tiny - no bigger than a fingernail -

and she's waiting for her prey.

Almost the same color as her background,

she's virtually invisible.

No more honey for her.

But of course, the spider's hunting grounds are limited.

Not all flowers are yellow.

When she sits on a pure white petal, she immediately becomes obvious.

She will never catch a bee while she's so conspicuous.

So she changes.

She breaks down the yellow pigments in the outer layer of her skin

to expose special crystals underneath

that act like tiny mirrors and reflect the light.

It may take a few days,

but she turns from yellow to white.

Changing color isn't the spider's only trick.

There's more to this story than meets the eye.

Bees can see colours that we cannot.

They can see ultraviolet colours.

As they come in to land on a flower,

they use special sensors that can detect ultraviolet patterns

on the flower's petals.

We can see them too

with our special UV camera.

There are dark lines on the petals

that mark the landing strips for the bees,

guiding them to the nectar.

The spider, however, has developed a way to exploit these signals.

Watching her with our UV camera,

we can see that she reflects ultraviolet light,

SO she appears even more conspicuous sitting on a flower.

This extra brilliance acts as a kind of super signal

which the bee can't resist.

And the spider benefits.

In fact, the bees are more than three times as likely

to visit flowers with UV-reflecting spiders on them

than those without.

The crab spider uses a sophisticated range of colours

to deceive its prey.

But color can also be used in a simpler, even more surprising way

to confuse the enemy.

And on the plains of Kenya's Maasai Mara,

there's one animal that uses just two colours

to outwit its predators.

The zebra.

Its black and white coat makes it extremely obvious

as it grazes out on the open grasslands.

Other grazers have softer, gently varied coloration,

which blends with their background.

So, it seems strange that zebras apparently do quite the opposite.

Particularly as they live in a world where there are so many hunters.

Lions...

...hyenas...

...and cheetah.

The boldly-striped zebra seem to be asking for trouble.

How do they get away with it?

The question has been hotly debated by naturalists for centuries.

New research is now suggesting an answer.

To understand how it might work,

we need to consider the particular colours involved.

Black and white are two of the most contrasting colours

and no two animals have exactly the same pattern,

so each has a unique whole-body fingerprint.

But when the zebras move, the stripes create confusion.

It's known as motion dazzle...

...and it makes it difficult for a predator

to keep focused on one particular target.

The cheetah, looking for a meal.

To make a successful strike,

they must judge the distance accurately and time it perfectly.

So if a zebra's stripes can confuse the cheetah

just for a few crucial seconds,

it may escape.

ZEBRAS CALL

But there's another threat on these plains.

BUZZING

Flies.

They are a real pest here.

They're not just a nuisance - they carry diseases,

some of which are particularly nasty, even deadly.

Despite the huge numbers of flies,

the zebras appear remarkably untroubled by them.

There are plenty of flies around...

...but few actually land on the zebra.

One theory is that the black and white stripes

make it difficult for flies to judge the distance.

To test this idea,

scientists counted how many flies landed

on animals with gently graded colours

and how many landed on the zebra's stripes.

They found that four times fewer flies landed on zebras

than on their more plainly-colored neighbours.

Why should that be?

It seems it's another consequence of those stripes.

They confuse the flies as they make their final approach to settle.

Perhaps this creates a visual blurring for the flies,

much as it does for a cheetah.

So, it seems that the zebra's patterns of stripes

create an optical effect that helps protect them

from enemies both large and small.

While zebras use different patterns to confuse their enemies,

on the island of Cuba

there are smaller and rather slower-moving creatures

that do a similar thing.

This is Polymath pica,

a Cuban painted snail.

You might think that this one is

an exceptionally lovely, eye-catching individual.

But it's not by any means the only snail

that is so beautifully decorated.

No two individuals are exactly the same,

yet all these belong to the same species.

There are also five other species of Polymath here.

Each snail has its own unique combination

of colours and stripes.

Their colours come from their diet -

lichen and mosses rich in minerals

that give the shells these stunning colours.

They differ according to the particular mix of plants

that each snail has been eating.

Variations of individuals within a species

is not uncommon in the natural world.

It's called polymorphism.

But it's particularly marked among Cuban snails.

Some scientists believe that the variation in itself

may be a kind of defense against predators.

But how could that work?

Most animals looking for prey have a search image in their minds.

They scan their surroundings

looking for a victim that matches their expectations.

If they see something they recognise, they'll go for it.

And that's where the snail's varying colours may come in.

The great range of different tints and patterns,

it seems, confuses the birds.

He's never seen one quite like this before.

And while the bird is wondering whether it's edible or not,

the snail can - slowly - make a getaway.

So, it seems that color can both conceal and confuse.

And sometimes it's used in yet a third, quite different, way.

Some poisonous animals,

like this little ladybird,

use color as a warning.

It's bright red,

and that's a message which says,

"Keep away. I'm poisonous."

Red, black and yellow are widely understood as warnings,

so the ladybird's message is a truthful one -

it is poisonous.

But some animals that are in fact harmless

have found it profitable to develop these warning colours themselves.

This African queen butterfly, like the ladybird,

is indeed very poisonous.

But this is a different species entirely -

a Dana butterfly.

It has almost exactly the same coloration,

yet it's perfectly edible.

It is, you might say, using its colours and patterns

to tell a lie.

To our eyes and to that of the predators,

poisonous and non-poisonous individuals look almost identical -

and that's the point.

The Dana mimics the colours and patterns of the African queen

and so it isn't eaten.

Mimicry like this occurs quite frequently among insects.

The yellow and black stripes of this harmless overfly

resemble the warning colours of bees and wasps that sting,

so it's left alone.

Other animals use mimicry to hide.

This moth resembles a broken twig.

A kind of mantis closely matches the shape and colours of a leaf.

Another mantis is shaped and colored like a flower...

...and gets a reward for the resemblance.

And one particular caterpillar has come to look like a tiny snake.

While this butterfly's wings take on the appearance of dead leaves.

But there are some animals which use mimicry

for a rather more sinister purpose.

And one such creature lives here on Australia's Great Barrier Reef.

Just beneath the surface, the reef is a riot of color.

But that means there are great opportunities for deceptions.

A blue striped Lenny.

It lives close to a cleaning station -

a place on the reef where large fish come

to get their parasites picked off by smaller fish

that feed on what they remove.

This little wrasse is one of these cleaners.

It has a longstanding relationship that relies on trust.

The big fish get a health treatment

and the little fish get a meal.

But the Lenny has learn how to exploit this trusting relationship.

It leaves its hole and starts looking for a meal.

But the big fish don't seem to trust it.

It's time for a change of costume.

Filmed close up under controlled conditions,

we can see how the Lenny’s brown stripes turn black.

The pigment cells in its skin expand and contract

to bring about this subtle change.

But it's enough to do the trick.

The Lenny now looks very similar to a juvenile cleaner wrasse.

It's a devious disguise

and one that will help it take advantage of the arrangement

the cleaner wrasse has developed with its clients.

It's spotted a target -

a butterflyfish.

The Lenny hangs back,

allowing an established cleaner wrasse to start work.

Now the Lenny slowly moves in,

as if to offer the same service as the wrasse.

But once within range...

...it strikes!

Its razor-sharp teeth have removed not just dead skin

but a chunk of flesh.

This isn't the treatment the butterflyfish was expecting.

The Lenny's deceit may work for a time,

but eventually it has consequences.

Reef fish begin to associate

the distinctive colours of a cleaner wrasse

with the pain of the bites of a Lenny.

Then they will eventually stop coming to this cleaning station.

And that is bad for business for the Lenny too.

So it's time to let things cool off.

A quick change back to brown

and its deception is over - for now.

All the while, it keeps its eye on the cleaning station

and waits for its next target.

Some animals change color for short periods of time

in order to deceive others,

but some use color mimicry permanently

as a method of persuading a different species

to rear their young.

One such creature lives here on the grasslands of southern Zambia.

A nest hidden in the grass.

It belongs to a pair of common waybills.

They are busy feeding their chicks.

The hungry youngsters open their beaks

to display a conspicuously patterned gape

which says, in effect, "Food here, please!”

And the parent obeys.

But among them, in this nest, there is an impostor.

One is significantly bigger than the rest.

It hatched from an egg

that was surreptitiously laid in the waybills' nest

by a pin-tailed why.

Having done so, she flew away,

leaving her young to be cared for by the waybills.

But why do the waybills feed this impostor?

The parent birds recognise their young

by the pattern of their gapes.

And the black and white markings are characteristic of their species.

But the impostor's markings closely mimic those of its nest-mates,

and because it's bigger, it takes nearly all the food

and the young waybills get little or none.

Two weeks later,

and the young why is much bigger.

By now, however,

the adult waybills have accepted the young why as their own,

and the more it begs, the more they give it.

One last meal from its luckless foster-parents...

...and the young why leaves its nest-mates behind.

And this is what it will grow up to be -

quite different from the hardworking waybills that raised it.

All pin-tailed howdahs are reared like this.

Mimicry wins.

Deceiving a different species is one thing,

but in South Africa, one animal uses mimicry to fool its own kind.

The Orange River, the largest in South Africa,

and on it, the Aug rabies Falls.

These are the main home

of a particular species of flat-backed lizards.

The males are brilliantly colored.

The females, on the other hand, are very different.

They are plain and drab.

The brilliance of a male's colours is an indication

of its physical fitness and strength.

The higher their status, the more colorful they are.

And they're not afraid to make their seniority quite clear.

A side-shuffle dance showing off their colours

is usually quite enough to settle who is the boss.

But if that doesn't work,

they fight.

Their disputes are all about location.

Sometimes they want a vantage point from which to show off.

At others, a good place to hide,

or to get close to the river where there's food.

Here on these falls, food means flies.

The river is a breeding ground for black flies.

There are huge swarms of them.

And they are the favourite food of the lizards.

They have acrobatic skills needed to catch them.

While the colorful males are busy feeding,

a different kind of male appears.

He is brown, rather like a female.

There's just a hint of blue on his throat

that gives him away as a male.

He's fully mature,

but not yet strong enough to compete with his flashier neighbours.

To avoid fighting, he delays the development of his colours

and so mimics a female.

One in ten young males behave in this this way.

But he still needs to eat,

and to do that, he's got to get down to the river where the flies are.

That means getting past the powerful, highly-colored males.

One thing could reveal the deception -

he may look like a female, but he smells like a male.

As long as he keeps his distance, he'll be alright.

The big male hasn't noticed that he's not a female.

Almost there.

Only one male now stands in his way.

The most dominant and aggressive of the lot.

He's made it.

His disguise worked and now he can feast on the flies.

He won't be able to keep this up forever.

Ultimately, all males have to put on their glad rags

and develop those bright colours if they are to breed.

For now, though, he's developed a disguise that enables him to cheat

in one of nature's most color-dependent mating systems.

So, animals of all kinds use color in a multitude of different ways.

New discoveries are giving us fresh insights

into the lives of these animals,

and new cameras are allowing us to see into a world of color

as never before.

We're only just beginning to understand

the many different ways in which animals use color,

particularly those colours that we can't even see.

For us, color in the natural world is a source of beauty and wonder,

but for animals, it's a tool for survival.

We've seen in this series that color is crucial for survival.

So what happens to animals when their world changes color?

The experts we've worked with in the field

have been helping us to find out.

In the Cairns in Scotland, I met Jim Corn foot,

a land manager and an expert

on the natural history of these mountains.

How long have you been here now?

Over 30 years since I started up here,

so I've seen a lot of different changes.

In what way?

On the Cairn plateau,

there's areas where we have snow patches lasting all year round,

but if you look at the last, sort of, 20 years,

there's five, six times where the snow has completely gone,

and in over, sort of, 200, 250 years,

there's only been seven times that that's happened.

Has that had a great effect on the wildlife?

You know, they're out of kilter, basically,

with what's going on around them.

So, things like mountain hare, ptarmigan,

they're standing out with the browns and the heather behind them.

And they're still white?

And they're still white, yeah, so they're not set up for that.

So if it's a very poor winter, you know, they're suffering.

Ptarmigan, a kind of grouse,

live year round in this exposed environment,

where there are few places to hide.

And now, as the world warms, things are changing dangerously.

The recent decrease in snow cover has made them only too conspicuous.

Animals like this mountain hare, also in its winter coat,

can be seen from far away.

And that makes life very hazardous.

BIRDS CAW

These changes are affecting animals all around the Northern Hemisphere.

In North America, the reduced snow cover has caused snowshoe hares

to be mismatched on average for a week a year.

During this time,

the hare is 10% more likely to end up as someone else's dinner.

By the end of the century,

the loss of snow cover is predicted to expose the hares

for up to eight weeks a year,

so increasing their annual mortality by almost a quarter.

Unless they can adapt rapidly,

they could be in serious danger of extinction.

While a warming climate is causing problems

in northern habitats...

...it's also driving color changes in other parts of the world.

Including some of the most beautiful, color-rich habitats

on our planet...

...coral reefs.

Our Australian team spent months

filming on the Great Barrier Reef.

In these sunlit waters, color is everywhere.

But this habitat is being subjected

to the most drastic color change imaginable.

And our crew witnessed it firsthand.

The corals have suddenly turned into white skeletons.

It's called coral bleaching

and it's now happening only too frequently.

On the Great Barrier Reef, such events have increased

from once in every 25 years

to three events in the last five.

Professor Jorge Weizmann

from the Coral Reef Laboratory at the University of Southampton

has been working to discover what is behind these changes.

The key is the relationship between coral

and the microscopic algae that live in their tissues.

These algal partners are called symbionts.

It's they that give the coral its color.

The algae, when they photosynthesis during the daylight hours,

use sunlight to grow,

excreting sugars as a by-product,

which are then absorbed by the corals.

This partnership was established during the time of the dinosaurs

and has been such a success

that it has created structures that are visible from space.

But warming seas are disrupting this system.

So, when the seawater temperatures rise above a critical threshold,

the photosynthetic machinery of the algal symbionts

starts to malfunction.

SIR DAVID: They begin to produce toxic compounds

which cause the corals to expel them from their tissues.

So the coral loses its color.

It bleaches.

Sometimes the bleached corals die,

and then the entire ecosystem,

together with everything it supports, is lost.

Almost half of the corals in the Great Barrier Reef

have died this way over the last 15 years.

But in the last decade,

there have been reports from various parts of the world

of coral developing startling neon colours.

We are just beginning to realise

that corals are using color to fight back.

Org is studying how this works.

JOG: This coral has lost its algal symbionts,

but instead of turning white,

it's producing these bright neon green pigments.

The coral produces these pigments

to protect the remaining algae inside of the tissue

from excess light stress,

so they act as a sort of sunscreen for the symbiont algae.

SIR DAVID: This coral sunscreen makes it more likely

that the bleached coral will be able to take back its algal partners,

restoring its food supply, its color,

and helping it to recover.

But even this extraordinary adaptation is not enough

to protect coral against all the changes it is now facing.

If corals have been exposed only to mild stress,

then they can recover from bleaching.

SIR DAVID: But if corals are subjected

to prolonged or extreme levels of heat stress,

they lose their ability to create these sunscreen pigments

and are likely to die -

and unfortunately, global warming is making this more likely.

There's a severe danger

that corals will be exposed to episodes of stress

where they can't recover

and where they can't use these pigments

to bounce back from bleaching.

SIR DAVID: So although color might be helping coral reefs

to tolerate some of the change,

only action to halt global warming will ensure their survival.

If warming continues, then they,

together with the beautiful array of color they provide,

will disappear from the reefs of the world.