The natural world is full of colours.
Colours that attract attention.
Colours that blend beautifully with their background.
And colours that create extraordinary displays.
There are few animals more brilliantly coloured
than these scarlet macaws.
Animals can use colour for all kinds of different reasons,
and some have colours that we ourselves can't even see.
But with new cameras,
some developed especially for this series,
we can reveal a world that has long been hidden from our eyes.
A world of colours that only some animals can see.
Secret communication channels for the most private of messages.
And colours so bold and brilliant,they dazzle our senses.
Whether to win a mate…
or beat a rival,
to warn off an enemy
or to hide from one.
We will reveal extraordinary stories about Life in Colour.
The rocky hills of Southern India.
The stage is setxa0for a performance
of one of the most spectacular dances in the natural world.
Peacocks are gathering.
is one of the most glamorous of all sights in nature.
A hundred and fifty shimmering eyespots,
carried on tail feathers that are six feet long.
So how did such glories evolve?
It seems it's all down to the female.
The brighter a male's colours
and the greater the number of his featheryxa0eyespots,
the more attractive she will find him.
But colours and plumes like these come at a cost.
The immense tail makes flying difficult.
The males are literally weighed down by their feathers.
Yet the colours they carry are clearly very important to them.
So why and how has colour taken on such value?
To understand that,
we have to think back to when it all began.
Seven hundred million years ago,
our planet was far less colourful.
But the first animals, it seems,
had eyes that were unable to distinguish colours anyway.
Gradually, however, this changed.
I am in Costa Rica…
a good place to see how valuable colour can be.
This toucan likes fruit,
and its ability to choose ripe fruit from unripexa0depends on colour,
because the ripe ones are black.
And this capacity of choosing between different colours
close relatives of dinosaurs,
appeared before mammals.
The first mammals, as far as we can tell,
were mostly nocturnal.
Colours are not easily distinguishable
so why evolve the ability to detect them?
So it seems that the first mammals themselves
were not very colourful.
And this is still largely true today.
Most are shades of black and white.
But there are exceptions.
And one of the most dramatic
lives in the forests of Gabon in West Africa.
These monkeys are mandrills,
a kind of baboon.
They live in large troops.
Most are females and youngsters,
both of which are brown.
But the males are different.
They, when they're young,
have very plain faces with naked muzzles.
As they grow, their faces begin to change.
Testosterone begins to flow through their veins.
When they're about six years old,
they leave the troop and start to fend for themselves.
As they become sexually mature,
colour appears in their faces.
And what colour!
weighing over 30 kilos.
Enormously, frighteningly powerful.
And their colours say so.
It is not only his face which is coloured.
So is his rump.
Both are fearless declarations
of his health and strength.
And this male is more than happy to prove just how strong he is
should any male dare to challenge him.
mandrill eyes are particularly sensitive to colour.
And it's the brightness of their colours which signals their status.
There are four males in this troop,
and they're constantly flexing their muscles
and displaying theirxa0colours to establish who is the strongest.
And not all disputes are settled peacefully.
They emphasise their ferocity by gestures,
such as grinding their teeth.
If that doesn't work,
the highest-ranking male will fight…
and the others know it.
It's better to let colour do the talking.
Mandrills see the world much as we do
and have three kinds of colour-sensitive cells.
But another group of animals has colour vision that's far superior
to that of any mammal.
Their ability varies from group to group,
but you can judge how good they are
from the colours they use to signal to one another.
Hummingbirds have excellent colour vision,
because that enables them to spot brightly coloured flowers,
which contains the nectar on which they feed.
So this artificial feeder is a big success.
Brightly coloured down here
and containing sugar solution,artificial nectar, up there.
But hummingbirds also use their ability to see colour in a different way,
to attract a mate.
Most species live in South America,
where there are flowers of some sort all year round.
A few, however, have spread northwards
into the deserts of the American Southwest.
In this vastness,
it's hard to get noticed,
especially if you're a small hummingbird looking for a mate.
But this male Costa's hummingbird uses his colours to send a secret message.
Out in the open,
flashy colours can attract unwanted attention,