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This programme contains scenes
of Repetitive Flashing Images
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00:00:16,840 --> 00:00:21,920
The natural world is full of colours
that we often take for granted.
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There are few animals
more brilliantly coloured
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than these scarlet macaws.
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Animals can use colour for
all kinds of different reasons
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and some have colours
that we ourselves can't even see.
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But not all colours are what
they seem.
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00:00:53,040 --> 00:00:56,440
Some animals also use
colours to hide.
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Colours that make them disappear.
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Colours that create
optical illusions.
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And colours that are used
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to trick and deceive.
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00:01:15,160 --> 00:01:17,390
To understand how these
colours work,
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we need to see them
from an animal's perspective.
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With the help of our specialist
cameras, we can now do that...
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..and discover how some animals
have become masters of disguise.
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00:02:03,680 --> 00:02:09,160
The Indian subcontinent is home to
some truly spectacular animals.
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Most, like these peafowl, use colour
to attract attention and the kinds
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they've developed are influenced
by the way they see the world.
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But flashy colours
can also come at a cost,
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00:02:38,440 --> 00:02:42,600
and, sometimes, it's better
to remain out of sight.
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So, some animals use their colours
to help them hide
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and disappear into the background.
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One such animal lives here
in the forests of central India.
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It's one of the most formidable
hunters on Earth.
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A Bengal tiger.
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A female.
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She is one of the world's
biggest cats.
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And remaining out of sight
is not easy
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when you are as large as she is.
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Her orange and black coat
is crucial to her success.
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To have any chance
of catching a meal,
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she has to get to within
a few metres of her prey.
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She keeps to the cover of the trees
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and slowly makes her approach.
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She may appear conspicuous
to our eyes,
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but not so to these chital deer.
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00:04:26,840 --> 00:04:31,510
Chital have only two types of colour
receptors in their eyes,
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compared to our three, which
means that they are, effectively,
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00:04:36,440 --> 00:04:38,880
blind to red and orange.
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So, to the deer,
the tiger isn't orange at all.
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This is how we see world...
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..and this is how deer do.
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The tiger's orange coat to them
is a muted shade of green,
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00:05:05,040 --> 00:05:08,800
so it's nearly impossible
for the deer to register.
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She creeps closer.
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The chital don't see her.
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00:05:50,680 --> 00:05:54,680
The odds appear stacked in
the tiger's favour.
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00:06:02,960 --> 00:06:05,880
But the deer aren't entirely
defenceless.
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00:06:08,760 --> 00:06:11,800
They have help from an unusual ally.
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00:06:13,440 --> 00:06:15,670
Langur monkeys.
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00:06:15,680 --> 00:06:19,270
They are known as
"the eyes of the forest"
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and their colour vision
is excellent.
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Their eyes, like ours, have
three types of colour receptors,
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and they can see orange.
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The langurs sounded the alarm
before she could get close enough.
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If the langurs can easily spot her,
why, then,
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is the tiger orange at all?
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00:07:11,880 --> 00:07:13,640
Why isn't she green?
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00:07:16,080 --> 00:07:20,200
That's because mammals are unable
to develop green pigments.
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00:07:21,240 --> 00:07:24,510
So, it seems the next best solution
for the tiger is to have
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orange fur, which appears
green to her main prey.
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She will have to find a new target.
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Down by the water, she finds one.
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Sambar deer.
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Sambar don't keep company
with monkeys.
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They are on their own.
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00:08:03,880 --> 00:08:08,030
They have the same limited eyesight
as the chital
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but ears like satellite dishes.
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00:08:12,520 --> 00:08:15,430
If she treads on a twig
and it snaps,
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the hunt will be over
before it began.
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The deer seem to sense danger.
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They still can't see her.
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00:10:16,000 --> 00:10:19,190
Despite her effective camouflage,
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most hunts end like this.
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Less than 10% of her attacks
are successful.
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But, without her orange fur,
her chances would be even lower.
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It is her colours that are key
to her survival.
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The Cairngorm Mountains in Scotland.
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Here, there are special problems
for the hunted.
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Some animals have developed
camouflage of such perfection
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that they are virtually invisible
against their surroundings.
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But what happens
when those surroundings change?
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00:11:10,480 --> 00:11:13,800
Well, then, of course,
the animals have to change, too.
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These mountains are home
to a particular kind of grouse
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called the ptarmigan.
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Their mottled brown feathers
make them inconspicuous
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among the rocks and heather.
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00:11:38,960 --> 00:11:43,920
But, in winter, these mountains
are hard places in which to live.
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Temperatures drop,
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and the land can, overnight,
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be covered by a blanket of snow.
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Most birds by now have gone south
to warmer parts of the world.
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But not the ptarmigan.
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When winter comes, they undergo
the most extraordinary change.
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They replace their brown feathers
with pure white ones.
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They do so for a simple reason -
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they must go unnoticed.
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They need to hide.
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00:12:28,160 --> 00:12:30,830
This open habitat
makes the ptarmigan
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very vulnerable to predators.
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Being the right colour is crucial.
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Now they are invisible
even to a keen-eyed eagle.
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Ptarmigan are not the only animals
to use this disappearing act.
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So does the Arctic fox...
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00:13:01,720 --> 00:13:02,920
..snowshoe hares...
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00:13:03,960 --> 00:13:05,230
..and weasels.
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00:13:05,240 --> 00:13:09,830
All, with the coming of winter,
change their coats
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and vanish from sight.
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Their transformation is triggered
by the decreasing daylight,
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and, over several weeks,
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they replace their brown costumes
with white ones.
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So, changing colour with
the seasons, for some animals,
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is the only way
to avoid becoming a meal.
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But many plants, of course,
do the reverse.
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In spring, they produce colour
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to declare that they are
providing food - nectar.
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Bees, and many other insects,
love it.
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In spring and summer, they travel
busily from flower to flower,
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collecting it.
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And, when the bees leave to look for
more, they inadvertently take pollen
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with them which then fertilises
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the next flowers they visit.
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00:14:28,520 --> 00:14:32,360
But there's a hunter here that
exploits this relationship.
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A crab spider.
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She's tiny,
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no bigger than a fingernail,
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and she is waiting for her prey.
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Almost the same colour
as her background,
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she's virtually invisible.
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No more honey for her!
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But, of course, the spider's hunting
grounds are limited.
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Not all flowers are yellow.
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When she sits on a pure white petal,
she immediately becomes obvious.
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She will never catch a bee
while she's so conspicuous.
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So, she changes.
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She breaks down the yellow pigments
in the outer layer of her skin
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to expose special crystals
underneath that act like
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tiny mirrors and reflect the light.
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00:16:10,960 --> 00:16:12,590
It may take a few days,
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but she turns from yellow
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to white.
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00:16:23,760 --> 00:16:26,440
Changing colour isn't
the spider's only trick.
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There's more to this story
than meets the eye.
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Bees can see colours that we cannot.
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They can see ultraviolet colours.
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As they come in to land on a flower,
they use special sensors that
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00:16:57,920 --> 00:17:02,080
can detect ultra-violet patterns
on the flower's petals.
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We can see them, too,
with our special UV camera.
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There are dark lines on the petals,
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that mark the landing
strips for the bees -
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guiding them to the nectar.
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The spider, however, has developed
a way to exploit these signals.
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Watching her with our UV camera,
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we can see that she reflects
ultra-violet light.
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So she appears even more conspicuous
sitting on a flower.
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This extra brilliance acts
as a kind of super-signal
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which the bee can't resist.
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And the spider benefits.
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In fact, the bees are more than
three times as likely
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to visit flowers with UV-reflecting
spiders on them than those without.
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The crab spider uses
a sophisticated range of colours
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to deceive its prey.
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00:19:00,760 --> 00:19:04,110
But colour can also be
used in a simpler,
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even more surprising way
to confuse the enemy.
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And, on the plains of Kenya's Maasai
Mara, there's one animal
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that uses just two colours
to outwit its predators.
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The zebra.
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Its black and white coat makes it
extremely obvious
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as it grazes out on the open
grasslands.
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Other grazers have softer,
gently varied colouration,
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which blends with their background.
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So, it seems strange that zebras,
apparently, do quite the opposite...
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..particularly as they live
in a world
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where there are so many hunters.
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Lions...
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..hyenas...
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..and cheetah.
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The boldly striped zebra seem to
be asking for trouble.
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How do they get away with it?
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The question has been hotly debated
by naturalists for centuries.
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New research is now
suggesting an answer.
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To understand how it might work,
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we need to consider
the particular colours involved.
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Black and white are two
of the most contrasting colours.
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And no two animals
have exactly the same pattern,
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so, each has a unique,
whole-body fingerprint.
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But, when the zebras move,
the stripes create confusion.
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It's known as motion dazzle.
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00:21:18,240 --> 00:21:21,630
And it makes it difficult
for a predator to keep focused
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on one particular target.
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The cheetah are looking for a meal.
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To make a successful strike,
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they must judge the distance
accurately and time it perfectly.
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So, if a zebra's stripes
can confuse the cheetah
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just for a few crucial seconds,
it may escape.
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00:22:38,960 --> 00:22:42,320
But there's another
threat on these plains.
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Flies!
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They are a real pest here.
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They're not just a nuisance.
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They carry diseases, some of which
are particularly nasty,
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even deadly.
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Despite the huge numbers of flies,
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00:23:11,480 --> 00:23:15,200
the zebras appear remarkably
untroubled by them.
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There are plenty of flies around.
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00:23:25,480 --> 00:23:29,000
But few actually land on the zebra.
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00:23:31,560 --> 00:23:34,830
One theory is that
the black and white stripes
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make it difficult
for flies to judge the distance.
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00:23:41,120 --> 00:23:43,030
To test this idea,
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scientists counted how many flies
landed on animals
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with gently graded colours and how
many landed on the zebra's stripes.
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00:23:57,560 --> 00:24:01,790
They found that four times fewer
flies landed on zebras
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00:24:01,800 --> 00:24:04,280
than on their more plainly
coloured neighbours.
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00:24:09,720 --> 00:24:11,080
Why should that be?
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00:24:14,120 --> 00:24:17,760
It seems it's another
consequence of those stripes.
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00:24:20,360 --> 00:24:24,280
They confuse the flies as they make
their final approach to settle.
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00:24:27,720 --> 00:24:32,390
Perhaps this creates a visual
blurring for the flies,
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00:24:32,400 --> 00:24:34,360
much as it does for a cheetah.
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00:24:36,760 --> 00:24:40,670
So, it seems that the zebra's
patterns of stripes creates
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an optical effect that helps
protect them from enemies,
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both large and small.
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00:25:01,040 --> 00:25:06,190
While zebras use different patterns
to confuse their enemies,
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00:25:06,200 --> 00:25:09,830
on the island of Cuba,
there are smaller
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00:25:09,840 --> 00:25:11,910
and rather slower-moving creatures
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00:25:11,920 --> 00:25:14,080
that do a similar thing.
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00:25:19,160 --> 00:25:24,760
This is Polymita picta,
a Cuban painted snail.
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You might think that this one is
an exceptionally lovely,
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eye-catching individual.
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But it is not by any means
the only snail that is
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00:25:40,960 --> 00:25:42,520
so beautifully decorated.
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No two individuals
are exactly the same,
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00:25:52,400 --> 00:25:55,040
yet all these belong
to the same species.
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00:26:00,680 --> 00:26:03,560
There are also five other
species of Polymita here.
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Each snail has its own unique
combination of colours and stripes.
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Their colours come from their diet -
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00:26:30,800 --> 00:26:33,230
lichen and mosses rich in minerals
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00:26:33,240 --> 00:26:37,150
that give the shells
these stunning colours.
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00:26:37,160 --> 00:26:41,350
They differ according to
the particular mix of plants
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00:26:41,360 --> 00:26:43,910
that each snail has been eating.
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00:26:43,920 --> 00:26:47,070
Variations of individuals
within a species is not
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uncommon in the natural world.
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It's called polymorphism.
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00:26:52,600 --> 00:26:56,440
But it's particularly
marked among Cuban snails.
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00:27:05,440 --> 00:27:09,950
Some scientists believe that
the variation in itself may be
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00:27:09,960 --> 00:27:12,600
a kind of defence against predators.
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00:27:16,920 --> 00:27:18,760
But how could that work?
247
00:27:22,480 --> 00:27:27,280
Most animals looking for prey
have a search image in their minds.
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00:27:28,840 --> 00:27:31,950
They scan their surroundings
looking a victim
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00:27:31,960 --> 00:27:33,680
that matches their expectations.
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00:27:35,400 --> 00:27:38,760
If they see something
they recognise, they'll go for it.
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00:27:40,240 --> 00:27:44,240
And that's where the snail's
varying colours may come in.
252
00:27:46,200 --> 00:27:49,670
The great range of different tints
and patterns, it seems,
253
00:27:49,680 --> 00:27:50,720
confuses the birds.
254
00:27:53,640 --> 00:27:55,960
He's never seen one
quite like this before.
255
00:28:01,640 --> 00:28:05,430
And, while the bird is wondering
whether it is edible or not,
256
00:28:05,440 --> 00:28:12,120
the snail can, slowly,
make a getaway!
257
00:28:17,880 --> 00:28:22,960
So, it seems that colour
can both conceal and confuse.
258
00:28:24,680 --> 00:28:29,040
And sometimes it's used in yet
a third, quite different, way.
259
00:28:30,680 --> 00:28:34,470
Some poisonous animals,
like this little ladybird,
260
00:28:34,480 --> 00:28:36,680
use colour as a warning.
261
00:28:37,800 --> 00:28:41,070
It's bright red, and that's
a message which says
262
00:28:41,080 --> 00:28:43,640
"Keep away, I'm poisonous."
263
00:28:45,520 --> 00:28:50,350
Red, black and yellow are widely
understood as warnings.
264
00:28:50,360 --> 00:28:53,910
So, the ladybird's message
is a truthful one.
265
00:28:53,920 --> 00:28:55,680
It is poisonous.
266
00:28:58,520 --> 00:29:01,590
But some animals,
that are in fact harmless,
267
00:29:01,600 --> 00:29:06,240
have found it profitable to develop
these warning colours themselves.
268
00:29:09,280 --> 00:29:12,830
This African queen butterfly,
like the ladybird,
269
00:29:12,840 --> 00:29:14,640
is indeed very poisonous.
270
00:29:17,200 --> 00:29:22,600
But this is a different species
entirely - a danaid butterfly.
271
00:29:23,840 --> 00:29:26,710
It has almost exactly
the same colouration,
272
00:29:26,720 --> 00:29:28,600
yet it's perfectly edible.
273
00:29:29,800 --> 00:29:34,640
It is, you might say, using its
colours and patterns to tell a lie.
274
00:29:37,000 --> 00:29:40,550
To our eyes,
and to that of the predators,
275
00:29:40,560 --> 00:29:45,110
poisonous and non-poisonous
individuals look almost identical.
276
00:29:45,120 --> 00:29:46,870
And that's the point.
277
00:29:46,880 --> 00:29:51,230
The danaid mimics the colours
and patterns of the African queen
278
00:29:51,240 --> 00:29:53,040
and, so, it isn't eaten.
279
00:29:56,840 --> 00:30:00,440
Mimicry like this occurs
quite frequently among insects.
280
00:30:02,320 --> 00:30:06,070
The yellow and black stripes
of this harmless hoverfly resemble
281
00:30:06,080 --> 00:30:09,950
the warning colours of bees
and wasps that sting,
282
00:30:09,960 --> 00:30:11,840
so, it's left alone.
283
00:30:14,040 --> 00:30:17,040
Other animals use mimicry to hide.
284
00:30:19,360 --> 00:30:22,520
This moth resembles a broken twig.
285
00:30:27,480 --> 00:30:32,080
A kind of mantis closely matches
the shape and colours of a leaf.
286
00:30:36,080 --> 00:30:39,600
Another mantis is shaped
and coloured like a flower...
287
00:30:41,920 --> 00:30:44,440
..and gets a reward
for the resemblance.
288
00:30:48,160 --> 00:30:52,840
And one particular caterpillar has
come to look like a tiny snake...
289
00:30:57,000 --> 00:31:01,190
..while this butterfly's wings
take on the appearance
290
00:31:01,200 --> 00:31:02,520
of dead leaves.
291
00:31:12,600 --> 00:31:14,390
But there are some animals
292
00:31:14,400 --> 00:31:18,160
which use mimicry for a rather
more sinister purpose.
293
00:31:19,920 --> 00:31:24,640
And one such creature lives here
on Australia's Great Barrier Reef.
294
00:31:29,000 --> 00:31:33,600
Just beneath the surface,
the reef is a riot of colour.
295
00:31:37,320 --> 00:31:41,920
But that means that there are great
opportunities for deceptions.
296
00:31:53,800 --> 00:31:55,920
A bluestriped blenny.
297
00:32:04,240 --> 00:32:07,590
It lives close to
a cleaning station -
298
00:32:07,600 --> 00:32:11,590
a place on the reef where large fish
come to get their parasites
299
00:32:11,600 --> 00:32:15,600
picked off by smaller fish
that feed on what they remove.
300
00:32:24,720 --> 00:32:28,120
This little wrasse
is one of these cleaners.
301
00:32:30,040 --> 00:32:34,920
It has a long-standing relationship
that relies on trust.
302
00:32:37,040 --> 00:32:41,720
The big fish get a health treatment
and the little fish get a meal.
303
00:32:44,040 --> 00:32:48,400
But the blenny has learnt how to
exploit this trusting relationship.
304
00:32:50,560 --> 00:32:54,360
It leaves its hole
and starts looking for a meal.
305
00:32:59,320 --> 00:33:02,120
But the big fish
don't seem to trust it.
306
00:33:05,360 --> 00:33:08,480
It's time for a change of costume.
307
00:33:15,560 --> 00:33:19,190
Filmed close up,
under controlled conditions,
308
00:33:19,200 --> 00:33:23,160
we can see how the blenny's brown
stripes turn black.
309
00:33:30,680 --> 00:33:32,950
The pigment cells in its skin
310
00:33:32,960 --> 00:33:36,640
expand and contract to bring about
this subtle change.
311
00:33:39,240 --> 00:33:41,320
But it's enough to do the trick.
312
00:33:46,600 --> 00:33:51,640
The blenny now looks very similar
to a juvenile cleaner wrasse.
313
00:33:58,080 --> 00:34:01,190
It's a devious disguise
and one that will help it
314
00:34:01,200 --> 00:34:04,670
take advantage of the arrangement
the cleaner wrasse
315
00:34:04,680 --> 00:34:06,800
has developed with its clients.
316
00:34:09,640 --> 00:34:14,440
It's spotted a target,
a butterflyfish.
317
00:34:18,480 --> 00:34:20,350
The blenny hangs back,
318
00:34:20,360 --> 00:34:24,280
allowing an established cleaner
wrasse to start work.
319
00:34:37,120 --> 00:34:39,910
Now the blenny slowly moves in,
320
00:34:39,920 --> 00:34:43,200
as if to offer the same service
as the wrasse.
321
00:34:56,120 --> 00:34:57,960
But once within range...
322
00:34:59,880 --> 00:35:01,520
..it strikes!
323
00:35:06,480 --> 00:35:10,510
Its razor-sharp teeth have removed
not just dead skin
324
00:35:10,520 --> 00:35:12,680
but a chunk of flesh.
325
00:35:17,920 --> 00:35:21,160
This isn't the treatment
the butterflyfish was expecting.
326
00:35:24,320 --> 00:35:27,430
The blenny's deceit
may work for a time,
327
00:35:27,440 --> 00:35:30,200
but, eventually,
it has consequences.
328
00:35:32,080 --> 00:35:35,510
Reef fish begin to associate
the distinctive colours
329
00:35:35,520 --> 00:35:38,960
of a cleaner wrasse with
the pain of the bites of a blenny.
330
00:35:40,960 --> 00:35:45,240
Then they will eventually stop
coming to this cleaning station.
331
00:35:49,560 --> 00:35:53,200
And that is bad for business
for the blenny, too.
332
00:35:55,680 --> 00:35:58,440
So, it's time to let things
cool off.
333
00:36:01,920 --> 00:36:06,390
A quick change back to brown
and its deception is over...
334
00:36:06,400 --> 00:36:08,480
..for now.
335
00:36:09,600 --> 00:36:13,470
All the while, it keeps its eye
on the cleaning station
336
00:36:13,480 --> 00:36:16,560
and waits for its next target.
337
00:36:27,880 --> 00:36:30,230
Some animals change colour
338
00:36:30,240 --> 00:36:33,750
for short periods of time
in order to deceive others,
339
00:36:33,760 --> 00:36:37,910
but some use colour mimicry
permanently as a method
340
00:36:37,920 --> 00:36:42,080
of persuading a different species
to rear their young.
341
00:36:44,560 --> 00:36:48,960
One such creature lives here on
the grasslands of southern Zambia.
342
00:36:55,160 --> 00:36:57,760
A nest, hidden in the grass.
343
00:37:00,280 --> 00:37:03,840
It belongs to a pair
of common waxbills.
344
00:37:11,080 --> 00:37:13,760
They are busy feeding their chicks.
345
00:37:16,160 --> 00:37:20,590
The hungry youngsters open their
beaks to display a conspicuously
346
00:37:20,600 --> 00:37:25,520
patterned gape which says,
in effect, "Food here, please."
347
00:37:28,520 --> 00:37:30,120
And the parent obeys.
348
00:37:46,200 --> 00:37:50,440
But among them,
in this nest, there is an impostor.
349
00:37:54,760 --> 00:37:57,800
One is significantly
bigger than the rest.
350
00:37:59,480 --> 00:38:00,790
It hatched from an egg
351
00:38:00,800 --> 00:38:02,750
that was surreptitiously laid
352
00:38:02,760 --> 00:38:04,270
in the waxbills' nest
353
00:38:04,280 --> 00:38:06,680
by a pin-tailed whydah.
354
00:38:08,920 --> 00:38:12,750
Having done so, she flew away
leaving her young to be
355
00:38:12,760 --> 00:38:14,680
cared for by the waxbills.
356
00:38:17,040 --> 00:38:19,840
But why do the waxbills feed
this impostor?
357
00:38:22,840 --> 00:38:24,990
The parent birds
recognise their young
358
00:38:25,000 --> 00:38:28,280
by the pattern of their gapes...
359
00:38:31,080 --> 00:38:35,200
..and the black-and-white markings
are characteristic of their species.
360
00:38:37,280 --> 00:38:42,190
But the imposter's markings closely
mimic those of its nest-mates,
361
00:38:42,200 --> 00:38:47,070
and because it is bigger,
it takes nearly all the food,
362
00:38:47,080 --> 00:38:49,920
and the young waxbills
get little or none.
363
00:39:08,480 --> 00:39:10,040
Two weeks later...
364
00:39:11,360 --> 00:39:14,440
..and the young whydah
is much bigger.
365
00:39:26,480 --> 00:39:27,870
By now, however,
366
00:39:27,880 --> 00:39:30,030
the adult waxbills have accepted
367
00:39:30,040 --> 00:39:32,430
the young whydah as their own,
368
00:39:32,440 --> 00:39:34,550
and the more it begs,
369
00:39:34,560 --> 00:39:36,040
the more they give it.
370
00:39:56,880 --> 00:40:01,320
One last meal from its luckless
foster parents...
371
00:40:07,240 --> 00:40:08,630
..and the young whydah
372
00:40:08,640 --> 00:40:11,400
leaves its nest-mates behind.
373
00:40:23,040 --> 00:40:26,830
And this is what it will
grow up to be,
374
00:40:26,840 --> 00:40:29,550
quite different
from the hard-working waxbills
375
00:40:29,560 --> 00:40:30,880
that raised it.
376
00:40:33,200 --> 00:40:36,990
All pin-tailed
whydahs are reared like this.
377
00:40:37,000 --> 00:40:39,200
Mimicry wins.
378
00:40:46,000 --> 00:40:48,910
Deceiving a different
species is one thing,
379
00:40:48,920 --> 00:40:54,960
but in South Africa, one animal uses
mimicry to fool its own kind.
380
00:40:58,200 --> 00:41:01,070
The Orange River,
the largest in South Africa,
381
00:41:01,080 --> 00:41:05,440
and on it, the Augrabies Falls.
382
00:41:10,920 --> 00:41:12,710
These are the main home
383
00:41:12,720 --> 00:41:16,280
of a particular species
of flat-back lizards.
384
00:41:20,480 --> 00:41:23,440
The males are brilliantly coloured.
385
00:41:29,560 --> 00:41:32,880
The females, on the other hand,
are very different.
386
00:41:38,120 --> 00:41:40,360
They are plain and drab.
387
00:41:44,360 --> 00:41:47,630
The brilliance of a male's colours
is an indication
388
00:41:47,640 --> 00:41:49,840
of its physical fitness
and strength.
389
00:41:54,920 --> 00:41:58,200
The higher their status,
the more colourful they are...
390
00:42:00,280 --> 00:42:04,360
..and they're not afraid to
make their seniority quite clear.
391
00:42:12,200 --> 00:42:13,710
A side-shuffle dance,
392
00:42:13,720 --> 00:42:15,550
showing off their colours,
393
00:42:15,560 --> 00:42:16,990
is usually quite enough
394
00:42:17,000 --> 00:42:18,520
to settle who is the boss.
395
00:42:20,960 --> 00:42:24,080
But if that doesn't work,
they fight.
396
00:42:38,320 --> 00:42:41,680
Their disputes are all
about location.
397
00:42:46,000 --> 00:42:50,390
Sometimes they want a vantage
point from which to show off.
398
00:42:50,400 --> 00:42:53,990
At others, a good place to hide,
399
00:42:54,000 --> 00:42:55,870
or to get close to the river,
400
00:42:55,880 --> 00:42:57,520
where there's food.
401
00:43:00,880 --> 00:43:05,120
Here on these falls,
food means flies.
402
00:43:09,400 --> 00:43:12,710
The river is a breeding
ground for blackflies.
403
00:43:12,720 --> 00:43:14,800
There are huge swarms of them.
404
00:43:16,200 --> 00:43:19,760
And they are the favourite
food of the lizards.
405
00:43:24,880 --> 00:43:27,760
They have acrobatic skills
needed to catch them.
406
00:43:54,360 --> 00:43:58,190
While the colourful males
are busy feeding,
407
00:43:58,200 --> 00:44:01,520
a different kind of male appears.
408
00:44:03,760 --> 00:44:06,680
He is brown, rather like a female.
409
00:44:12,160 --> 00:44:15,190
There's just a hint of blue
on his throat
410
00:44:15,200 --> 00:44:17,320
that gives him away as a male.
411
00:44:22,800 --> 00:44:24,870
He's fully mature,
412
00:44:24,880 --> 00:44:28,800
but not yet strong enough to compete
with his flashier neighbours.
413
00:44:30,920 --> 00:44:35,350
To avoid fighting, he delays
the development of his colours,
414
00:44:35,360 --> 00:44:38,030
and so mimics a female.
415
00:44:38,040 --> 00:44:41,760
One in ten young males
behave in this way.
416
00:44:43,560 --> 00:44:45,590
But he still needs to eat,
417
00:44:45,600 --> 00:44:49,880
and to do that he's got to get down
to the river where the flies are.
418
00:44:51,640 --> 00:44:56,480
That means getting past the
powerful, highly coloured males.
419
00:45:03,920 --> 00:45:06,990
One thing could reveal
the deception.
420
00:45:07,000 --> 00:45:08,990
He may look like a female,
421
00:45:09,000 --> 00:45:11,000
but he smells like a male.
422
00:45:17,440 --> 00:45:20,920
As long as he keeps his distance,
he'll be all right.
423
00:45:24,600 --> 00:45:28,280
The big male hasn't noticed
that he's not a female.
424
00:45:45,760 --> 00:45:47,320
Almost there.
425
00:45:49,800 --> 00:45:53,000
Only one male now stands
in his way...
426
00:45:56,160 --> 00:45:59,120
..the most dominant and aggressive
of the lot.
427
00:46:22,280 --> 00:46:23,720
He's made it.
428
00:46:24,720 --> 00:46:30,000
His disguise worked
and now he can feast on the flies.
429
00:46:49,160 --> 00:46:52,390
He won't be able to keep
this up for ever.
430
00:46:52,400 --> 00:46:56,270
Ultimately, all males have to
put on their glad rags
431
00:46:56,280 --> 00:47:00,080
and develop those bright colours
if they are to breed.
432
00:47:05,520 --> 00:47:08,790
For now, though, he's developed
a disguise that enables him
433
00:47:08,800 --> 00:47:12,920
to cheat in one of nature's most
colour-dependant mating systems.
434
00:47:18,720 --> 00:47:21,430
So, animals of all kinds
435
00:47:21,440 --> 00:47:24,720
use colour in a multitude of
different ways.
436
00:47:26,640 --> 00:47:29,790
New discoveries are giving us
fresh insights
437
00:47:29,800 --> 00:47:32,200
into the lives of these animals...
438
00:47:33,320 --> 00:47:36,270
..and new cameras
are allowing us to see
439
00:47:36,280 --> 00:47:39,600
into a world of colour
as never before.
440
00:47:52,920 --> 00:47:56,990
We're only just beginning to
understand the many different ways
441
00:47:57,000 --> 00:47:59,790
in which animals use colour,
442
00:47:59,800 --> 00:48:03,600
particularly those colours
that we can't even see.
443
00:48:09,640 --> 00:48:12,710
For us, colour in the natural world
444
00:48:12,720 --> 00:48:16,270
is a source of beauty and wonder,
445
00:48:16,280 --> 00:48:19,880
but for animals,
it's a tool for survival.
446
00:48:39,880 --> 00:48:44,800
We've seen in this series
that colour is crucial for survival.
447
00:48:50,360 --> 00:48:54,440
So what happens to animals
when their world changes colour?
448
00:48:56,880 --> 00:48:59,790
The experts we've worked with
in the field
449
00:48:59,800 --> 00:49:02,080
have been helping us to find out.
450
00:49:05,360 --> 00:49:10,350
In the Cairngorms, in Scotland,
I met Jim Cornfoot, a land manager
451
00:49:10,360 --> 00:49:13,720
and an expert on the natural
history of these mountains.
452
00:49:14,880 --> 00:49:17,390
How long have you been here now?
453
00:49:17,400 --> 00:49:19,590
Over 30 years
since I started up here,
454
00:49:19,600 --> 00:49:23,070
so I've seen a lot of different
changes, you know.
455
00:49:23,080 --> 00:49:24,350
In what way?
456
00:49:24,360 --> 00:49:27,390
On the Cairngorm Plateau, there's
areas where we have snow patches
457
00:49:27,400 --> 00:49:28,590
lasting all the year round,
458
00:49:28,600 --> 00:49:30,470
but if you look at the last
sort of 20 years,
459
00:49:30,480 --> 00:49:34,070
there's five, six times where
the snow's completely gone,
460
00:49:34,080 --> 00:49:38,110
and in over sort of 200, 250 years,
there's only been seven times
461
00:49:38,120 --> 00:49:39,470
that that's happened.
462
00:49:39,480 --> 00:49:42,150
Has that had a great effect
on the wildlife?
463
00:49:42,160 --> 00:49:44,910
You know, they're out of kilter,
basically,
464
00:49:44,920 --> 00:49:46,670
with what's going on around them.
465
00:49:46,680 --> 00:49:48,630
So things like mountain hare,
ptarmigan,
466
00:49:48,640 --> 00:49:51,590
they're standing out with the browns
and the heather behind them.
467
00:49:51,600 --> 00:49:52,790
And they're still white?
468
00:49:52,800 --> 00:49:56,270
And they're still white, yes,
so they're not set up for that,
469
00:49:56,280 --> 00:49:58,390
so if it's a very poor winter,
470
00:49:58,400 --> 00:50:00,320
you know, they're suffering.
471
00:50:01,560 --> 00:50:03,750
Ptarmigan, a kind of grouse,
472
00:50:03,760 --> 00:50:07,110
live year-round
in this exposed environment
473
00:50:07,120 --> 00:50:09,800
where there are few places to hide.
474
00:50:16,080 --> 00:50:21,080
But now, as the world warms,
things are changing dangerously.
475
00:50:22,840 --> 00:50:27,920
The recent decrease in snow cover
has made them only too conspicuous.
476
00:50:32,120 --> 00:50:34,550
Animals like this mountain hare,
477
00:50:34,560 --> 00:50:38,120
also in its winter coat,
can be seen from far away...
478
00:50:40,240 --> 00:50:42,920
..and that makes life
very hazardous.
479
00:50:45,280 --> 00:50:50,400
These changes are affecting animals
all around the northern hemisphere.
480
00:50:52,040 --> 00:50:57,470
In North America, the reduced snow
cover has caused snowshoe hares
481
00:50:57,480 --> 00:51:01,480
to be mismatched on average
for a week a year.
482
00:51:03,000 --> 00:51:06,230
During the time, the hare is 10%
more likely
483
00:51:06,240 --> 00:51:08,920
to end up as someone else's dinner.
484
00:51:10,320 --> 00:51:14,950
By the end of the century, the loss
of snow cover is predicted to expose
485
00:51:14,960 --> 00:51:17,750
the hares
for up to eight weeks a year,
486
00:51:17,760 --> 00:51:22,320
so increasing their annual
mortality by almost a quarter.
487
00:51:23,600 --> 00:51:25,630
Unless they can adapt rapidly,
488
00:51:25,640 --> 00:51:28,680
they could be in serious
danger of extinction.
489
00:51:32,840 --> 00:51:37,160
While a warming climate is causing
problems in northern habitats...
490
00:51:38,760 --> 00:51:43,080
..it's also driving colour changes
in other parts of the world...
491
00:51:46,680 --> 00:51:49,150
..including some
of the most beautiful,
492
00:51:49,160 --> 00:51:51,960
colour-rich habitats
on our planet...
493
00:51:53,680 --> 00:51:55,080
..coral reefs.
494
00:52:01,120 --> 00:52:06,120
Our Australian team spent months
filming on the Great Barrier Reef.
495
00:52:15,960 --> 00:52:19,960
In these sunlit waters,
colour is everywhere.
496
00:52:23,240 --> 00:52:25,950
But this habitat is being subjected
497
00:52:25,960 --> 00:52:29,950
to the most drastic colour
change imaginable,
498
00:52:29,960 --> 00:52:33,840
and our crew witnessed it
first-hand.
499
00:52:37,680 --> 00:52:41,960
The corals have suddenly
turned into white skeletons.
500
00:52:44,320 --> 00:52:47,150
It's called coral bleaching
501
00:52:47,160 --> 00:52:49,680
and it's now happening
only too frequently.
502
00:52:54,320 --> 00:52:56,070
On the Great Barrier Reef,
503
00:52:56,080 --> 00:53:01,070
such events have increased
from once in every 25 years
504
00:53:01,080 --> 00:53:03,720
to three events in the last five.
505
00:53:13,880 --> 00:53:17,390
Professor Jorg Wiedenmann
from the Coral Reef Laboratory
506
00:53:17,400 --> 00:53:19,670
at the University of Southampton
507
00:53:19,680 --> 00:53:23,520
has been working to discover
what is behind these changes.
508
00:53:25,840 --> 00:53:29,110
The key is the relationship
between coral
509
00:53:29,120 --> 00:53:32,880
and the microscopic algae
that live in their tissues.
510
00:53:35,760 --> 00:53:39,270
These algal partners
are called symbionts.
511
00:53:39,280 --> 00:53:42,240
It's they that give
the coral its colour.
512
00:53:43,840 --> 00:53:47,830
The algae, when they photosynthesise
during the daylight hours,
513
00:53:47,840 --> 00:53:52,950
use sunlight to grow,
excreting sugars as a by-product,
514
00:53:52,960 --> 00:53:55,680
which are then
absorbed by the corals.
515
00:53:59,920 --> 00:54:04,630
This partnership was established
during the time of the dinosaurs
516
00:54:04,640 --> 00:54:09,230
and has been such a success
that it has created structures
517
00:54:09,240 --> 00:54:10,960
that are visible from space.
518
00:54:12,200 --> 00:54:15,830
But warming seas are disrupting
this system.
519
00:54:15,840 --> 00:54:20,630
So, when the seawater temperatures
rise above a critical threshold,
520
00:54:20,640 --> 00:54:23,990
the photosynthetic machinery
of the algal symbionts
521
00:54:24,000 --> 00:54:25,680
starts to malfunction.
522
00:54:29,840 --> 00:54:33,150
They begin to produce toxic
compounds which cause
523
00:54:33,160 --> 00:54:36,240
the corals to expel them
from their tissues.
524
00:54:40,440 --> 00:54:43,040
So the coral loses its colour.
525
00:54:44,400 --> 00:54:46,120
It bleaches.
526
00:54:50,240 --> 00:54:55,710
Sometimes the bleached corals die,
and then the entire ecosystem,
527
00:54:55,720 --> 00:54:59,080
together with everything it
supports, is lost.
528
00:55:02,240 --> 00:55:06,350
Almost half of the corals
in the Great Barrier Reef
529
00:55:06,360 --> 00:55:10,080
have died this way
over the last 15 years.
530
00:55:15,720 --> 00:55:17,630
But in the last decade,
531
00:55:17,640 --> 00:55:20,790
there have been reports
from various parts of the world
532
00:55:20,800 --> 00:55:24,880
of coral developing
startling neon colours.
533
00:55:30,680 --> 00:55:32,790
We're just beginning to realise
534
00:55:32,800 --> 00:55:36,280
that corals are using colour
to fight back.
535
00:55:41,120 --> 00:55:44,280
Jorg is studying how this works.
536
00:55:45,560 --> 00:55:48,790
This coral has lost
its algal symbionts,
537
00:55:48,800 --> 00:55:50,430
but instead of turning white,
538
00:55:50,440 --> 00:55:53,440
it's producing these bright,
neon-green pigments.
539
00:55:55,840 --> 00:55:59,750
The coral produces these pigments
to protect the remaining algae
540
00:55:59,760 --> 00:56:03,830
inside of the tissue
from excess light stress.
541
00:56:03,840 --> 00:56:07,240
So they act as a sort of sunscreen
for the symbiont algae.
542
00:56:09,440 --> 00:56:14,270
This coral sunscreen makes it more
likely that the bleached coral
543
00:56:14,280 --> 00:56:17,270
will be able to take
back its algal partners,
544
00:56:17,280 --> 00:56:22,120
restoring its food supply, its
colour, and helping it to recover.
545
00:56:24,360 --> 00:56:28,190
But even this extraordinary
adaptation is not enough
546
00:56:28,200 --> 00:56:32,670
to protect coral against
all the changes it is now facing.
547
00:56:32,680 --> 00:56:36,430
If corals have been exposed
only to mild stress,
548
00:56:36,440 --> 00:56:38,240
then they can
recover from bleaching.
549
00:56:40,000 --> 00:56:42,630
But if corals are subjected
to prolonged
550
00:56:42,640 --> 00:56:44,870
or extreme levels of heat stress,
551
00:56:44,880 --> 00:56:49,350
they lose their ability to create
these sunscreen pigments
552
00:56:49,360 --> 00:56:51,040
and are likely to die.
553
00:56:52,200 --> 00:56:56,000
And unfortunately, global warming
is making this more likely.
554
00:56:57,440 --> 00:56:58,990
There's a severe danger
555
00:56:59,000 --> 00:57:03,270
that corals will be exposed to
episodes of stress
556
00:57:03,280 --> 00:57:06,790
where they can't recover and where
they can't use these pigments
557
00:57:06,800 --> 00:57:08,680
to bounce back from bleaching.
558
00:57:10,600 --> 00:57:13,150
So, although colour
might be helping coral reefs
559
00:57:13,160 --> 00:57:15,430
to tolerate some of the change,
560
00:57:15,440 --> 00:57:20,830
only action to halt global warming
will ensure their survival.
561
00:57:20,840 --> 00:57:24,030
If warming continues, then they,
562
00:57:24,040 --> 00:57:27,070
together with the beautiful array
of colour they provide,
563
00:57:27,080 --> 00:57:29,960
will disappear from the reefs
of the world.
46486
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