All language subtitles for FBFF4A72DEFF5FA2779E17483336A133_eng

The Indian subcontinent is home
to some truly spectacular animals.

Most, like these peafowl,
use colour 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 cheetal deer.

Cheetal have only two types
of colour 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 cheetal don't see her.

The odds appear stacked
in the tiger's favour.

But the deer aren't entirely defenceless.

They have help from an unusual
ally. Langer monkeys. They're

known as the eyes of the
forest and their colour vision is

excellent.

Their eyes, like ours, have three types of
colour receptors and they can see orange.

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

If the Langers 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 Sambar deer. Sambar don't

keep company with monkeys.
They are on their own. They have

the same limited eyesight
as the cheetal, 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 will be even

lower. It is her colours
that are key to her survival.

The Cairngorm 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 colour 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. Or 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 colour
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
colour to declare that they 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 fertilises 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 colour as her
background. She's virtually invisible.

No more honey for her.

But of course the spiders
hunting grounds are limited. Not

all flowers are yellow. But 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 colour 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
the 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 colour
can also be used in a simpler,

even more surprising
way, to confuse the enemy.

And on the plains of Kenya's
Masai 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

colouration 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 boldest-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 prey. 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.

But there's another threat on these plains.

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 coloured neighbours.

Why should that be? It seems it's
another consequence of those stripes.

They confuse the flies
with the other stripes.

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
creates 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 Polymita picta.
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 Polymita here. Each

snail has its own unique
combination of colours and stripes.

Their colours come from their
diet. Lichens 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
defence 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 colour can
both conceal and confuse. And

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

poisonous animals, like a
ladybird, use colour 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

denied butterfly. It has
almost exactly the same

colouration, 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 denied 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 hoverfly 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 coloured 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

Earth. Australia's Great Barrier Reef.

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

But that means there are great
opportunities for deceptions.

A blue-striped blenny.

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 long -standing relationship
that relies on trust.

The big fish get a health
treatment, and the little fish

get a meal. But the blenny
has learned 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 blenny'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 blenny 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 butterfly fish.

The blenny hangs back, allowing an
established cleaner wrasse to start work.

Now the blenny 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
butterfly fish was expecting.

The blenny'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 blenny. Then they
will eventually stop coming to

this cleaning station.

And that is bad for business for the blenny
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
colour for short periods of time

in order to deceive others.
But some use colour 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 waxbills.

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 imposter.

One is significantly bigger
than the rest. It hatched from

an egg that was surreptitiously
laid in the waxbills' nest

by a pint-tailed wider. Having
done so, she flew away,

leaving her young to be cared
for by the waxbills. But why

do the waxbills feed this imposter?

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 imposter's
markings closely mimic those of

its nest mates. And because
it's bigger, it takes nearly

all the food and the young
waxbills get little or none.

Two weeks later. And the
young wider is much bigger.

By now, however, the adult
waxbills have accepted the young

wider as their own. And the
more it begs, the more they give

it.

One last meal from its
luckless foster parents.

And the young wider leaves
its nest. The nest mates behind.

And this is what it will
grow up to be. Quite different

from the hard-working
waxbills that raised it.

All pint-tailed widers 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 Augrabius Falls.

These are the main home of a
particular species of flat -backed lizards.

The males are brilliantly coloured.

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 colourful they

are. And they're not
afraid to make their sinews.

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.

But others, a good place
to hide. Or to get close to the

river, where there's food.

Here on these falls, food
is scarce. Food means flies.

The river is a breeding
ground for blackflies. There are

huge swarms of them. And
they are the favourite food of the

lizards.

They have acrobatic
skills needed to catch them.

Music

While the colourful 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 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

coloured males.

Music

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.

Music He's made it. His disguise
works, 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 colour-dependent mating

systems.

So, animals of all kinds
use colour 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 colour as never before.

Music We're only just
beginning to understand the many

different ways in which
animals use colour, particularly

those colours that we can't even see. Music

For us, colour in the natural
world is a source of beauty

and wonder. But for
animals, it's a tool for survival.

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

So, what happens to animals
when their world changes colour?

The experts we've worked with
in the field have been helping

us to find out.

In the Cairngorms in Scotland,
I met Jim Cornfoot, 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 Cairngorm Plateau, there's

areas where we have snow
patches lasting all year round, but

if you look at the last 20
years, there's five, six times

where the snow's completely
gone. And over 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? Yes, they're not set
up for that, so 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.

But 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.

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.

Now, 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 Joerg Wiedemann
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

photosynthesize during the
daylight hours, use sunlight

to grow, excreting sugars
as a byproduct, 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.

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

colors.

We're just beginning to realize that
corals are using color to fight back.

Jörg is studying how this
works. 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. 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. 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. 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.