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This programme contains scenes
of Repetitive Flashing Images
2
00:00:17,300 --> 00:00:22,340
The natural world is full of colours
that we often take for granted.
3
00:00:31,300 --> 00:00:34,820
There are few animals
more brilliantly coloured
4
00:00:34,820 --> 00:00:36,700
than these scarlet macaws.
5
00:00:37,940 --> 00:00:41,660
Animals can use colour for
all kinds of different reasons
6
00:00:41,660 --> 00:00:46,100
and some have colours
that we ourselves can't even see.
7
00:00:48,780 --> 00:00:51,380
But not all colours are what
they seem.
8
00:00:53,500 --> 00:00:56,860
Some animals also use
colours to hide.
9
00:01:01,580 --> 00:01:03,700
Colours that make them disappear.
10
00:01:05,500 --> 00:01:08,260
Colours that create
optical illusions.
11
00:01:09,540 --> 00:01:12,060
And colours that are used
12
00:01:12,060 --> 00:01:13,820
to trick and deceive.
13
00:01:15,580 --> 00:01:17,820
To understand how these
colours work,
14
00:01:17,820 --> 00:01:21,060
we need to see them
from an animal's perspective.
15
00:01:23,140 --> 00:01:28,140
With the help of our specialist
cameras, we can now do that...
16
00:01:31,260 --> 00:01:36,300
..and discover how some animals
have become masters of disguise.
17
00:02:04,140 --> 00:02:09,580
The Indian subcontinent is home to
some truly spectacular animals.
18
00:02:20,180 --> 00:02:26,300
Most, like these peafowl, use colour
to attract attention and the kinds
19
00:02:26,300 --> 00:02:30,340
they've developed are influenced
by the way they see the world.
20
00:02:34,420 --> 00:02:38,900
But flashy colours
can also come at a cost,
21
00:02:38,900 --> 00:02:42,900
and, sometimes, it's better
to remain out of sight.
22
00:02:48,460 --> 00:02:52,060
So, some animals use their colours
to help them hide
23
00:02:52,060 --> 00:02:53,900
and disappear into the background.
24
00:03:01,060 --> 00:03:05,460
One such animal lives here
in the forests of central India.
25
00:03:07,860 --> 00:03:10,740
It's one of the most formidable
hunters on Earth.
26
00:03:13,300 --> 00:03:14,820
A Bengal tiger.
27
00:03:14,820 --> 00:03:16,420
A female.
28
00:03:19,060 --> 00:03:21,980
She is one of the world's
biggest cats.
29
00:03:21,980 --> 00:03:24,580
And remaining out of sight
is not easy
30
00:03:24,580 --> 00:03:26,900
when you are as large as she is.
31
00:03:31,220 --> 00:03:35,100
Her orange and black coat
is crucial to her success.
32
00:03:38,620 --> 00:03:41,260
To have any chance
of catching a meal,
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00:03:41,260 --> 00:03:45,060
she has to get to within
a few metres of her prey.
34
00:04:06,300 --> 00:04:08,740
She keeps to the cover of the trees
35
00:04:08,740 --> 00:04:11,020
and slowly makes her approach.
36
00:04:17,220 --> 00:04:20,620
She may appear conspicuous
to our eyes,
37
00:04:20,620 --> 00:04:23,740
but not so to these chital deer.
38
00:04:27,300 --> 00:04:31,940
Chital have only two types of colour
receptors in their eyes,
39
00:04:31,940 --> 00:04:36,860
compared to our three, which
means that they are, effectively,
40
00:04:36,860 --> 00:04:39,260
blind to red and orange.
41
00:04:43,180 --> 00:04:46,500
So, to the deer,
the tiger isn't orange at all.
42
00:04:50,660 --> 00:04:53,300
This is how we see world...
43
00:04:55,700 --> 00:04:57,980
..and this is how deer do.
44
00:05:00,100 --> 00:05:05,500
The tiger's orange coat to them
is a muted shade of green,
45
00:05:05,500 --> 00:05:09,180
so it's nearly impossible
for the deer to register.
46
00:05:20,060 --> 00:05:21,780
She creeps closer.
47
00:05:30,060 --> 00:05:32,500
The chital don't see her.
48
00:05:51,140 --> 00:05:55,060
The odds appear stacked in
the tiger's favour.
49
00:06:03,420 --> 00:06:06,260
But the deer aren't entirely
defenceless.
50
00:06:09,140 --> 00:06:12,140
They have help from an unusual ally.
51
00:06:13,820 --> 00:06:16,100
Langur monkeys.
52
00:06:16,100 --> 00:06:19,700
They are known as
"the eyes of the forest"
53
00:06:19,700 --> 00:06:22,060
and their colour vision
is excellent.
54
00:06:31,340 --> 00:06:35,500
Their eyes, like ours, have
three types of colour receptors,
55
00:06:35,500 --> 00:06:37,020
and they can see orange.
56
00:06:44,820 --> 00:06:46,660
MONKEY SCREECHES
57
00:06:46,660 --> 00:06:48,500
SCREECHING ECHOES
58
00:06:54,420 --> 00:06:58,340
The langurs sounded the alarm
before she could get close enough.
59
00:07:07,020 --> 00:07:09,820
If the langurs can easily spot her,
why, then,
60
00:07:09,820 --> 00:07:12,260
is the tiger orange at all?
61
00:07:12,260 --> 00:07:14,020
Why isn't she green?
62
00:07:16,580 --> 00:07:20,580
That's because mammals are unable
to develop green pigments.
63
00:07:21,620 --> 00:07:24,900
So, it seems the next best solution
for the tiger is to have
64
00:07:24,900 --> 00:07:28,900
orange fur, which appears
green to her main prey.
65
00:07:38,100 --> 00:07:41,500
She will have to find a new target.
66
00:07:49,980 --> 00:07:53,540
Down by the water, she finds one.
67
00:07:53,540 --> 00:07:55,500
Sambar deer.
68
00:07:57,380 --> 00:08:00,380
Sambar don't keep company
with monkeys.
69
00:08:00,380 --> 00:08:02,420
They are on their own.
70
00:08:04,300 --> 00:08:08,420
They have the same limited eyesight
as the chital
71
00:08:08,420 --> 00:08:11,340
but ears like satellite dishes.
72
00:08:13,020 --> 00:08:15,860
If she treads on a twig
and it snaps,
73
00:08:15,860 --> 00:08:19,220
the hunt will be over
before it began.
74
00:09:14,300 --> 00:09:16,940
The deer seem to sense danger.
75
00:09:21,780 --> 00:09:23,340
They still can't see her.
76
00:10:12,260 --> 00:10:13,460
WATER SPLASHES
77
00:10:16,300 --> 00:10:19,580
Despite her effective camouflage,
78
00:10:19,580 --> 00:10:21,900
most hunts end like this.
79
00:10:23,420 --> 00:10:27,140
Less than 10% of her attacks
are successful.
80
00:10:30,540 --> 00:10:35,260
But, without her orange fur,
her chances would be even lower.
81
00:10:35,260 --> 00:10:39,180
It is her colours that are key
to her survival.
82
00:10:47,580 --> 00:10:50,420
The Cairngorm Mountains in Scotland.
83
00:10:51,620 --> 00:10:55,100
Here, there are special problems
for the hunted.
84
00:10:58,940 --> 00:11:02,980
Some animals have developed
camouflage of such perfection
85
00:11:02,980 --> 00:11:07,300
that they are virtually invisible
against their surroundings.
86
00:11:07,300 --> 00:11:10,980
But what happens
when those surroundings change?
87
00:11:10,980 --> 00:11:14,180
Well, then, of course,
the animals have to change, too.
88
00:11:18,260 --> 00:11:21,780
These mountains are home
to a particular kind of grouse
89
00:11:21,780 --> 00:11:23,620
called the ptarmigan.
90
00:11:30,020 --> 00:11:32,980
Their mottled brown feathers
make them inconspicuous
91
00:11:32,980 --> 00:11:34,500
among the rocks and heather.
92
00:11:39,420 --> 00:11:44,260
But, in winter, these mountains
are hard places in which to live.
93
00:11:45,900 --> 00:11:47,300
Temperatures drop,
94
00:11:47,300 --> 00:11:49,220
and the land can, overnight,
95
00:11:49,220 --> 00:11:51,340
be covered by a blanket of snow.
96
00:11:53,700 --> 00:11:58,260
Most birds by now have gone south
to warmer parts of the world.
97
00:11:58,260 --> 00:12:00,660
But not the ptarmigan.
98
00:12:02,380 --> 00:12:06,420
When winter comes, they undergo
the most extraordinary change.
99
00:12:07,940 --> 00:12:12,900
They replace their brown feathers
with pure white ones.
100
00:12:15,900 --> 00:12:19,580
They do so for a simple reason -
101
00:12:19,580 --> 00:12:21,820
they must go unnoticed.
102
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They need to hide.
103
00:12:28,620 --> 00:12:31,220
This open habitat
makes the ptarmigan
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00:12:31,220 --> 00:12:33,420
very vulnerable to predators.
105
00:12:37,060 --> 00:12:39,220
Being the right colour is crucial.
106
00:12:40,740 --> 00:12:44,980
Now they are invisible
even to a keen-eyed eagle.
107
00:12:49,300 --> 00:12:53,500
Ptarmigan are not the only animals
to use this disappearing act.
108
00:12:58,580 --> 00:13:00,460
So does the Arctic fox...
109
00:13:02,060 --> 00:13:03,260
..snowshoe hares...
110
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..and weasels.
111
00:13:05,740 --> 00:13:10,220
All, with the coming of winter,
change their coats
112
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and vanish from sight.
113
00:13:15,700 --> 00:13:20,540
Their transformation is triggered
by the decreasing daylight,
114
00:13:20,540 --> 00:13:22,420
and, over several weeks,
115
00:13:22,420 --> 00:13:26,100
they replace their brown costumes
with white ones.
116
00:13:38,180 --> 00:13:42,580
So, changing colour with
the seasons, for some animals,
117
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is the only way
to avoid becoming a meal.
118
00:13:51,860 --> 00:13:55,020
But many plants, of course,
do the reverse.
119
00:13:58,340 --> 00:14:01,380
In spring, they produce colour
120
00:14:01,380 --> 00:14:05,260
to declare that they are
providing food - nectar.
121
00:14:07,300 --> 00:14:09,820
Bees, and many other insects,
love it.
122
00:14:11,900 --> 00:14:15,540
In spring and summer, they travel
busily from flower to flower,
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00:14:15,540 --> 00:14:16,980
collecting it.
124
00:14:18,380 --> 00:14:22,500
And, when the bees leave to look for
more, they inadvertently take pollen
125
00:14:22,500 --> 00:14:24,500
with them which then fertilises
126
00:14:24,500 --> 00:14:26,780
the next flowers they visit.
127
00:14:29,020 --> 00:14:32,700
But there's a hunter here that
exploits this relationship.
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A crab spider.
129
00:14:39,940 --> 00:14:41,180
She's tiny,
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no bigger than a fingernail,
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00:14:43,780 --> 00:14:45,980
and she is waiting for her prey.
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00:14:47,380 --> 00:14:48,500
BUZZING
133
00:14:51,660 --> 00:14:55,140
Almost the same colour
as her background,
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00:14:55,140 --> 00:14:57,020
she's virtually invisible.
135
00:15:19,020 --> 00:15:21,740
No more honey for her!
136
00:15:26,500 --> 00:15:30,740
But, of course, the spider's hunting
grounds are limited.
137
00:15:30,740 --> 00:15:32,580
Not all flowers are yellow.
138
00:15:35,660 --> 00:15:40,260
When she sits on a pure white petal,
she immediately becomes obvious.
139
00:15:44,580 --> 00:15:48,380
She will never catch a bee
while she's so conspicuous.
140
00:15:50,260 --> 00:15:52,260
So, she changes.
141
00:15:55,340 --> 00:15:58,420
She breaks down the yellow pigments
in the outer layer of her skin
142
00:15:58,420 --> 00:16:02,500
to expose special crystals
underneath that act like
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00:16:02,500 --> 00:16:05,300
tiny mirrors and reflect the light.
144
00:16:11,340 --> 00:16:12,980
It may take a few days,
145
00:16:12,980 --> 00:16:15,220
but she turns from yellow
146
00:16:15,220 --> 00:16:16,380
to white.
147
00:16:24,220 --> 00:16:26,780
Changing colour isn't
the spider's only trick.
148
00:16:28,660 --> 00:16:31,060
There's more to this story
than meets the eye.
149
00:16:39,220 --> 00:16:42,220
Bees can see colours that we cannot.
150
00:16:43,260 --> 00:16:46,300
They can see ultraviolet colours.
151
00:16:54,020 --> 00:16:58,300
As they come in to land on a flower,
they use special sensors that
152
00:16:58,300 --> 00:17:02,500
can detect ultra-violet patterns
on the flower's petals.
153
00:17:08,700 --> 00:17:13,340
We can see them, too,
with our special UV camera.
154
00:17:24,380 --> 00:17:26,980
There are dark lines on the petals,
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00:17:26,980 --> 00:17:30,260
that mark the landing
strips for the bees -
156
00:17:30,260 --> 00:17:32,340
guiding them to the nectar.
157
00:17:41,580 --> 00:17:46,620
The spider, however, has developed
a way to exploit these signals.
158
00:17:54,140 --> 00:17:56,980
Watching her with our UV camera,
159
00:17:56,980 --> 00:18:00,340
we can see that she reflects
ultra-violet light.
160
00:18:00,340 --> 00:18:04,100
So she appears even more conspicuous
sitting on a flower.
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00:18:08,020 --> 00:18:11,860
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.
164
00:18:30,740 --> 00:18:34,140
In fact, the bees are more than
three times as likely
165
00:18:34,140 --> 00:18:39,220
to visit flowers with UV-reflecting
spiders on them than those without.
166
00:18:52,460 --> 00:18:56,300
The crab spider uses
a sophisticated range of colours
167
00:18:56,300 --> 00:18:58,740
to deceive its prey.
168
00:19:01,220 --> 00:19:04,580
But colour can also be
used in a simpler,
169
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even more surprising way
to confuse the enemy.
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00:19:10,980 --> 00:19:15,620
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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00:19:29,540 --> 00:19:33,700
Its black and white coat makes it
extremely obvious
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00:19:33,700 --> 00:19:35,940
as it grazes out on the open
grasslands.
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00:19:41,660 --> 00:19:45,620
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.
180
00:20:06,780 --> 00:20:08,420
Lions...
181
00:20:09,700 --> 00:20:10,820
..hyenas...
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00:20:12,020 --> 00:20:13,420
..and cheetah.
183
00:20:19,820 --> 00:20:24,260
The boldly striped zebra seem to
be asking for trouble.
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How do they get away with it?
185
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The question has been hotly debated
by naturalists for centuries.
186
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New research is now
suggesting an answer.
187
00:20:43,580 --> 00:20:45,780
To understand how it might work,
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we need to consider
the particular colours involved.
189
00:20:49,100 --> 00:20:53,740
Black and white are two
of the most contrasting colours.
190
00:20:53,740 --> 00:20:57,380
And no two animals
have exactly the same pattern,
191
00:20:57,380 --> 00:21:01,180
so, each has a unique,
whole-body fingerprint.
192
00:21:07,940 --> 00:21:12,420
But, when the zebras move,
the stripes create confusion.
193
00:21:14,420 --> 00:21:16,660
It's known as motion dazzle.
194
00:21:18,740 --> 00:21:21,940
And it makes it difficult
for a predator to keep focused
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00:21:21,940 --> 00:21:24,300
on one particular target.
196
00:21:39,300 --> 00:21:42,060
The cheetah are looking for a meal.
197
00:21:58,300 --> 00:22:00,180
To make a successful strike,
198
00:22:00,180 --> 00:22:04,340
they must judge the distance
accurately and time it perfectly.
199
00:22:13,540 --> 00:22:16,340
So, if a zebra's stripes
can confuse the cheetah
200
00:22:16,340 --> 00:22:20,580
just for a few crucial seconds,
it may escape.
201
00:22:39,380 --> 00:22:42,660
But there's another
threat on these plains.
202
00:22:44,820 --> 00:22:46,460
BUZZING
203
00:22:46,460 --> 00:22:48,060
Flies!
204
00:22:50,900 --> 00:22:53,420
They are a real pest here.
205
00:22:55,260 --> 00:22:57,260
They're not just a nuisance.
206
00:22:57,260 --> 00:23:00,460
They carry diseases, some of which
are particularly nasty,
207
00:23:00,460 --> 00:23:02,100
even deadly.
208
00:23:09,140 --> 00:23:11,860
Despite the huge numbers of flies,
209
00:23:11,860 --> 00:23:15,540
the zebras appear remarkably
untroubled by them.
210
00:23:21,020 --> 00:23:23,540
There are plenty of flies around.
211
00:23:25,860 --> 00:23:29,300
But few actually land on the zebra.
212
00:23:31,980 --> 00:23:35,260
One theory is that
the black and white stripes
213
00:23:35,260 --> 00:23:38,660
make it difficult
for flies to judge the distance.
214
00:23:41,500 --> 00:23:43,500
To test this idea,
215
00:23:43,500 --> 00:23:46,940
scientists counted how many flies
landed on animals
216
00:23:46,940 --> 00:23:52,860
with gently graded colours and how
many landed on the zebra's stripes.
217
00:23:57,980 --> 00:24:02,260
They found that four times fewer
flies landed on zebras
218
00:24:02,260 --> 00:24:04,660
than on their more plainly
coloured neighbours.
219
00:24:10,140 --> 00:24:11,340
Why should that be?
220
00:24:14,620 --> 00:24:18,100
It seems it's another
consequence of those stripes.
221
00:24:20,740 --> 00:24:24,620
They confuse the flies as they make
their final approach to settle.
222
00:24:28,180 --> 00:24:32,700
Perhaps this creates a visual
blurring for the flies,
223
00:24:32,700 --> 00:24:34,700
much as it does for a cheetah.
224
00:24:37,180 --> 00:24:41,100
So, it seems that the zebra's
patterns of stripes creates
225
00:24:41,100 --> 00:24:44,660
an optical effect that helps
protect them from enemies,
226
00:24:44,660 --> 00:24:46,460
both large and small.
227
00:25:01,540 --> 00:25:06,660
While zebras use different patterns
to confuse their enemies,
228
00:25:06,660 --> 00:25:10,220
on the island of Cuba,
there are smaller
229
00:25:10,220 --> 00:25:12,300
and rather slower-moving creatures
230
00:25:12,300 --> 00:25:14,500
that do a similar thing.
231
00:25:19,660 --> 00:25:25,140
This is Polymita picta,
a Cuban painted snail.
232
00:25:29,300 --> 00:25:32,780
You might think that this one is
an exceptionally lovely,
233
00:25:32,780 --> 00:25:34,620
eye-catching individual.
234
00:25:37,740 --> 00:25:41,340
But it is not by any means
the only snail that is
235
00:25:41,340 --> 00:25:42,900
so beautifully decorated.
236
00:25:49,100 --> 00:25:52,860
No two individuals
are exactly the same,
237
00:25:52,860 --> 00:25:55,340
yet all these belong
to the same species.
238
00:26:01,060 --> 00:26:03,900
There are also five other
species of Polymita here.
239
00:26:05,740 --> 00:26:10,020
Each snail has its own unique
combination of colours and stripes.
240
00:26:28,460 --> 00:26:31,140
Their colours come from their diet -
241
00:26:31,140 --> 00:26:33,780
lichen and mosses rich in minerals
242
00:26:33,780 --> 00:26:37,660
that give the shells
these stunning colours.
243
00:26:37,660 --> 00:26:41,660
They differ according to
the particular mix of plants
244
00:26:41,660 --> 00:26:44,340
that each snail has been eating.
245
00:26:44,340 --> 00:26:47,540
Variations of individuals
within a species is not
246
00:26:47,540 --> 00:26:49,660
uncommon in the natural world.
247
00:26:49,660 --> 00:26:51,580
It's called polymorphism.
248
00:26:53,100 --> 00:26:56,820
But it's particularly
marked among Cuban snails.
249
00:27:05,900 --> 00:27:10,340
Some scientists believe that
the variation in itself may be
250
00:27:10,340 --> 00:27:12,940
a kind of defence against predators.
251
00:27:17,260 --> 00:27:19,140
But how could that work?
252
00:27:22,940 --> 00:27:27,700
Most animals looking for prey
have a search image in their minds.
253
00:27:29,220 --> 00:27:32,300
They scan their surroundings
looking a victim
254
00:27:32,300 --> 00:27:34,060
that matches their expectations.
255
00:27:35,780 --> 00:27:39,140
If they see something
they recognise, they'll go for it.
256
00:27:40,620 --> 00:27:44,620
And that's where the snail's
varying colours may come in.
257
00:27:46,660 --> 00:27:50,020
The great range of different tints
and patterns, it seems,
258
00:27:50,020 --> 00:27:51,140
confuses the birds.
259
00:27:54,020 --> 00:27:56,380
He's never seen one
quite like this before.
260
00:28:02,140 --> 00:28:05,820
And, while the bird is wondering
whether it is edible or not,
261
00:28:05,820 --> 00:28:12,460
the snail can, slowly,
make a getaway!
262
00:28:18,340 --> 00:28:23,300
So, it seems that colour
can both conceal and confuse.
263
00:28:25,100 --> 00:28:29,420
And sometimes it's used in yet
a third, quite different, way.
264
00:28:31,180 --> 00:28:34,820
Some poisonous animals,
like this little ladybird,
265
00:28:34,820 --> 00:28:37,060
use colour as a warning.
266
00:28:38,300 --> 00:28:41,500
It's bright red, and that's
a message which says
267
00:28:41,500 --> 00:28:43,980
"Keep away, I'm poisonous."
268
00:28:45,940 --> 00:28:50,860
Red, black and yellow are widely
understood as warnings.
269
00:28:50,860 --> 00:28:54,300
So, the ladybird's message
is a truthful one.
270
00:28:54,300 --> 00:28:56,060
It is poisonous.
271
00:28:58,980 --> 00:29:02,060
But some animals,
that are in fact harmless,
272
00:29:02,060 --> 00:29:06,580
have found it profitable to develop
these warning colours themselves.
273
00:29:09,780 --> 00:29:13,220
This African queen butterfly,
like the ladybird,
274
00:29:13,220 --> 00:29:15,020
is indeed very poisonous.
275
00:29:17,700 --> 00:29:22,940
But this is a different species
entirely - a danaid butterfly.
276
00:29:24,260 --> 00:29:27,100
It has almost exactly
the same colouration,
277
00:29:27,100 --> 00:29:28,940
yet it's perfectly edible.
278
00:29:30,260 --> 00:29:35,060
It is, you might say, using its
colours and patterns to tell a lie.
279
00:29:37,420 --> 00:29:41,020
To our eyes,
and to that of the predators,
280
00:29:41,020 --> 00:29:45,500
poisonous and non-poisonous
individuals look almost identical.
281
00:29:45,500 --> 00:29:47,380
And that's the point.
282
00:29:47,380 --> 00:29:51,620
The danaid mimics the colours
and patterns of the African queen
283
00:29:51,620 --> 00:29:53,420
and, so, it isn't eaten.
284
00:29:57,340 --> 00:30:00,740
Mimicry like this occurs
quite frequently among insects.
285
00:30:02,820 --> 00:30:06,540
The yellow and black stripes
of this harmless hoverfly resemble
286
00:30:06,540 --> 00:30:10,340
the warning colours of bees
and wasps that sting,
287
00:30:10,340 --> 00:30:12,180
so, it's left alone.
288
00:30:14,340 --> 00:30:17,380
Other animals use mimicry to hide.
289
00:30:19,820 --> 00:30:22,860
This moth resembles a broken twig.
290
00:30:27,980 --> 00:30:32,420
A kind of mantis closely matches
the shape and colours of a leaf.
291
00:30:36,540 --> 00:30:39,940
Another mantis is shaped
and coloured like a flower...
292
00:30:42,420 --> 00:30:44,820
..and gets a reward
for the resemblance.
293
00:30:48,540 --> 00:30:53,140
And one particular caterpillar has
come to look like a tiny snake...
294
00:30:57,460 --> 00:31:01,580
..while this butterfly's wings
take on the appearance
295
00:31:01,580 --> 00:31:02,900
of dead leaves.
296
00:31:14,860 --> 00:31:18,540
which use mimicry for a rather
more sinister purpose.
297
00:31:20,340 --> 00:31:25,060
And one such creature lives here
on Australia's Great Barrier Reef.
298
00:31:29,420 --> 00:31:33,980
Just beneath the surface,
the reef is a riot of colour.
299
00:31:37,740 --> 00:31:42,300
But that means that there are great
opportunities for deceptions.
300
00:31:54,140 --> 00:31:56,300
A bluestriped blenny.
301
00:32:04,700 --> 00:32:08,100
It lives close to
a cleaning station -
302
00:32:08,100 --> 00:32:12,020
a place on the reef where large fish
come to get their parasites
303
00:32:12,020 --> 00:32:15,980
picked off by smaller fish
that feed on what they remove.
304
00:32:25,220 --> 00:32:28,420
This little wrasse
is one of these cleaners.
305
00:32:30,500 --> 00:32:35,300
It has a long-standing relationship
that relies on trust.
306
00:32:37,420 --> 00:32:42,020
The big fish get a health treatment
and the little fish get a meal.
307
00:32:44,500 --> 00:32:48,700
But the blenny has learnt how to
exploit this trusting relationship.
308
00:32:50,980 --> 00:32:54,700
It leaves its hole
and starts looking for a meal.
309
00:32:59,740 --> 00:33:02,500
But the big fish
don't seem to trust it.
310
00:33:05,780 --> 00:33:08,820
It's time for a change of costume.
311
00:33:16,020 --> 00:33:19,660
Filmed close up,
under controlled conditions,
312
00:33:19,660 --> 00:33:23,500
we can see how the blenny's brown
stripes turn black.
313
00:33:31,140 --> 00:33:33,420
The pigment cells in its skin
314
00:33:33,420 --> 00:33:36,980
expand and contract to bring about
this subtle change.
315
00:33:39,660 --> 00:33:41,740
But it's enough to do the trick.
316
00:33:47,060 --> 00:33:51,980
The blenny now looks very similar
to a juvenile cleaner wrasse.
317
00:33:58,500 --> 00:34:01,700
It's a devious disguise
and one that will help it
318
00:34:01,700 --> 00:34:05,060
take advantage of the arrangement
the cleaner wrasse
319
00:34:05,060 --> 00:34:07,140
has developed with its clients.
320
00:34:10,140 --> 00:34:14,860
It's spotted a target,
a butterflyfish.
321
00:34:18,820 --> 00:34:20,780
The blenny hangs back,
322
00:34:20,780 --> 00:34:24,580
allowing an established cleaner
wrasse to start work.
323
00:34:37,500 --> 00:34:40,380
Now the blenny slowly moves in,
324
00:34:40,380 --> 00:34:43,580
as if to offer the same service
as the wrasse.
325
00:34:56,500 --> 00:34:58,300
But once within range...
326
00:35:00,180 --> 00:35:01,900
..it strikes!
327
00:35:06,900 --> 00:35:10,940
Its razor-sharp teeth have removed
not just dead skin
328
00:35:10,940 --> 00:35:13,060
but a chunk of flesh.
329
00:35:18,340 --> 00:35:21,460
This isn't the treatment
the butterflyfish was expecting.
330
00:35:24,780 --> 00:35:27,860
The blenny's deceit
may work for a time,
331
00:35:27,860 --> 00:35:30,540
but, eventually,
it has consequences.
332
00:35:32,500 --> 00:35:35,940
Reef fish begin to associate
the distinctive colours
333
00:35:35,940 --> 00:35:39,340
of a cleaner wrasse with
the pain of the bites of a blenny.
334
00:35:41,420 --> 00:35:45,620
Then they will eventually stop
coming to this cleaning station.
335
00:35:50,020 --> 00:35:53,580
And that is bad for business
for the blenny, too.
336
00:35:56,140 --> 00:35:58,860
So, it's time to let things
cool off.
337
00:36:02,340 --> 00:36:06,780
A quick change back to brown
and its deception is over...
338
00:36:06,780 --> 00:36:08,820
..for now.
339
00:36:10,060 --> 00:36:13,900
All the while, it keeps its eye
on the cleaning station
340
00:36:13,900 --> 00:36:16,940
and waits for its next target.
341
00:36:18,780 --> 00:36:20,820
BIRDS CHIRP
342
00:36:28,340 --> 00:36:30,780
Some animals change colour
343
00:36:30,780 --> 00:36:34,220
for short periods of time
in order to deceive others,
344
00:36:34,220 --> 00:36:38,300
but some use colour mimicry
permanently as a method
345
00:36:38,300 --> 00:36:42,460
of persuading a different species
to rear their young.
346
00:36:45,020 --> 00:36:49,340
One such creature lives here on
the grasslands of southern Zambia.
347
00:36:55,540 --> 00:36:58,180
A nest, hidden in the grass.
348
00:37:00,780 --> 00:37:04,180
It belongs to a pair
of common waxbills.
349
00:37:11,460 --> 00:37:14,180
They are busy feeding their chicks.
350
00:37:16,660 --> 00:37:20,940
The hungry youngsters open their
beaks to display a conspicuously
351
00:37:20,940 --> 00:37:25,860
patterned gape which says,
in effect, "Food here, please."
352
00:37:28,860 --> 00:37:30,460
And the parent obeys.
353
00:37:30,460 --> 00:37:32,900
CHICKS CHEEP
354
00:37:46,700 --> 00:37:50,780
But among them,
in this nest, there is an impostor.
355
00:37:55,180 --> 00:37:58,100
One is significantly
bigger than the rest.
356
00:37:59,900 --> 00:38:01,140
It hatched from an egg
357
00:38:01,140 --> 00:38:03,180
that was surreptitiously laid
358
00:38:03,180 --> 00:38:04,700
in the waxbills' nest
359
00:38:04,700 --> 00:38:07,020
by a pin-tailed whydah.
360
00:38:09,300 --> 00:38:13,100
Having done so, she flew away
leaving her young to be
361
00:38:13,100 --> 00:38:14,980
cared for by the waxbills.
362
00:38:17,420 --> 00:38:20,220
But why do the waxbills feed
this impostor?
363
00:38:23,300 --> 00:38:25,380
The parent birds
recognise their young
364
00:38:25,380 --> 00:38:28,660
by the pattern of their gapes...
365
00:38:31,500 --> 00:38:35,540
..and the black-and-white markings
are characteristic of their species.
366
00:38:37,740 --> 00:38:42,620
But the imposter's markings closely
mimic those of its nest-mates,
367
00:38:42,620 --> 00:38:47,540
and because it is bigger,
it takes nearly all the food,
368
00:38:47,540 --> 00:38:50,300
and the young waxbills
get little or none.
369
00:39:08,820 --> 00:39:10,380
Two weeks later...
370
00:39:11,860 --> 00:39:14,860
..and the young whydah
is much bigger.
371
00:39:19,940 --> 00:39:22,340
CHICKS CHEEP
372
00:39:26,860 --> 00:39:28,260
By now, however,
373
00:39:28,260 --> 00:39:30,460
the adult waxbills have accepted
374
00:39:30,460 --> 00:39:32,820
the young whydah as their own,
375
00:39:32,820 --> 00:39:34,940
and the more it begs,
376
00:39:34,940 --> 00:39:36,420
the more they give it.
377
00:39:57,380 --> 00:40:01,660
One last meal from its luckless
foster parents...
378
00:40:07,580 --> 00:40:08,980
..and the young whydah
379
00:40:08,980 --> 00:40:11,740
leaves its nest-mates behind.
380
00:40:23,540 --> 00:40:27,300
And this is what it will
grow up to be,
381
00:40:27,300 --> 00:40:29,900
quite different
from the hard-working waxbills
382
00:40:29,900 --> 00:40:31,260
that raised it.
383
00:40:33,660 --> 00:40:37,380
All pin-tailed
whydahs are reared like this.
384
00:40:37,380 --> 00:40:39,580
Mimicry wins.
385
00:40:46,500 --> 00:40:49,380
Deceiving a different
species is one thing,
386
00:40:49,380 --> 00:40:55,300
but in South Africa, one animal uses
mimicry to fool its own kind.
387
00:40:58,660 --> 00:41:01,460
The Orange River,
the largest in South Africa,
388
00:41:01,460 --> 00:41:05,780
and on it, the Augrabies Falls.
389
00:41:11,300 --> 00:41:13,140
These are the main home
390
00:41:13,140 --> 00:41:16,660
of a particular species
of flat-back lizards.
391
00:41:20,860 --> 00:41:23,860
The males are brilliantly coloured.
392
00:41:29,980 --> 00:41:33,180
The females, on the other hand,
are very different.
393
00:41:38,500 --> 00:41:40,700
They are plain and drab.
394
00:41:44,820 --> 00:41:48,060
The brilliance of a male's colours
is an indication
395
00:41:48,060 --> 00:41:50,180
of its physical fitness
and strength.
396
00:41:55,380 --> 00:41:58,580
The higher their status,
the more colourful they are...
397
00:42:00,740 --> 00:42:04,700
..and they're not afraid to
make their seniority quite clear.
398
00:42:12,580 --> 00:42:14,020
A side-shuffle dance,
399
00:42:14,020 --> 00:42:15,900
showing off their colours,
400
00:42:15,900 --> 00:42:17,380
is usually quite enough
401
00:42:17,380 --> 00:42:18,900
to settle who is the boss.
402
00:42:21,380 --> 00:42:24,500
But if that doesn't work,
they fight.
403
00:42:38,740 --> 00:42:42,060
Their disputes are all
about location.
404
00:42:46,420 --> 00:42:50,780
Sometimes they want a vantage
point from which to show off.
405
00:42:50,780 --> 00:42:54,380
At others, a good place to hide,
406
00:42:54,380 --> 00:42:56,300
or to get close to the river,
407
00:42:56,300 --> 00:42:57,900
where there's food.
408
00:43:01,340 --> 00:43:05,420
Here on these falls,
food means flies.
409
00:43:09,820 --> 00:43:13,140
The river is a breeding
ground for blackflies.
410
00:43:13,140 --> 00:43:15,180
There are huge swarms of them.
411
00:43:16,620 --> 00:43:20,100
And they are the favourite
food of the lizards.
412
00:43:25,380 --> 00:43:28,180
They have acrobatic skills
needed to catch them.
413
00:43:54,820 --> 00:43:58,580
While the colourful males
are busy feeding,
414
00:43:58,580 --> 00:44:01,900
a different kind of male appears.
415
00:44:04,140 --> 00:44:07,100
He is brown, rather like a female.
416
00:44:12,580 --> 00:44:15,540
There's just a hint of blue
on his throat
417
00:44:15,540 --> 00:44:17,740
that gives him away as a male.
418
00:44:23,220 --> 00:44:25,300
He's fully mature,
419
00:44:25,300 --> 00:44:29,100
but not yet strong enough to compete
with his flashier neighbours.
420
00:44:31,380 --> 00:44:35,820
To avoid fighting, he delays
the development of his colours,
421
00:44:35,820 --> 00:44:38,500
and so mimics a female.
422
00:44:38,500 --> 00:44:42,100
One in ten young males
behave in this way.
423
00:44:43,940 --> 00:44:46,020
But he still needs to eat,
424
00:44:46,020 --> 00:44:50,220
and to do that he's got to get down
to the river where the flies are.
425
00:44:52,100 --> 00:44:56,780
That means getting past the
powerful, highly coloured males.
426
00:45:04,340 --> 00:45:07,340
One thing could reveal
the deception.
427
00:45:07,340 --> 00:45:09,340
He may look like a female,
428
00:45:09,340 --> 00:45:11,380
but he smells like a male.
429
00:45:17,900 --> 00:45:21,300
As long as he keeps his distance,
he'll be all right.
430
00:45:25,020 --> 00:45:28,620
The big male hasn't noticed
that he's not a female.
431
00:45:46,100 --> 00:45:47,700
Almost there.
432
00:45:50,220 --> 00:45:53,380
Only one male now stands
in his way...
433
00:45:56,660 --> 00:45:59,500
..the most dominant and aggressive
of the lot.
434
00:46:22,660 --> 00:46:24,100
He's made it.
435
00:46:25,140 --> 00:46:30,380
His disguise worked
and now he can feast on the flies.
436
00:46:49,580 --> 00:46:52,780
He won't be able to keep
this up for ever.
437
00:46:52,780 --> 00:46:56,700
Ultimately, all males have to
put on their glad rags
438
00:46:56,700 --> 00:47:00,420
and develop those bright colours
if they are to breed.
439
00:47:05,980 --> 00:47:09,260
For now, though, he's developed
a disguise that enables him
440
00:47:09,260 --> 00:47:13,260
to cheat in one of nature's most
colour-dependant mating systems.
441
00:47:19,100 --> 00:47:21,820
So, animals of all kinds
442
00:47:21,820 --> 00:47:25,140
use colour in a multitude of
different ways.
443
00:47:27,100 --> 00:47:30,180
New discoveries are giving us
fresh insights
444
00:47:30,180 --> 00:47:32,580
into the lives of these animals...
445
00:47:33,780 --> 00:47:36,780
..and new cameras
are allowing us to see
446
00:47:36,780 --> 00:47:40,020
into a world of colour
as never before.
447
00:47:53,300 --> 00:47:57,340
We're only just beginning to
understand the many different ways
448
00:47:57,340 --> 00:48:00,220
in which animals use colour,
449
00:48:00,220 --> 00:48:03,980
particularly those colours
that we can't even see.
450
00:48:10,060 --> 00:48:13,100
For us, colour in the natural world
451
00:48:13,100 --> 00:48:16,780
is a source of beauty and wonder,
452
00:48:16,780 --> 00:48:20,260
but for animals,
it's a tool for survival.
453
00:48:40,260 --> 00:48:45,140
We've seen in this series
that colour is crucial for survival.
454
00:48:50,780 --> 00:48:54,820
So what happens to animals
when their world changes colour?
455
00:48:57,300 --> 00:49:00,220
The experts we've worked with
in the field
456
00:49:00,220 --> 00:49:02,500
have been helping us to find out.
457
00:49:05,820 --> 00:49:10,820
In the Cairngorms, in Scotland,
I met Jim Cornfoot, a land manager
458
00:49:10,820 --> 00:49:14,100
and an expert on the natural
history of these mountains.
459
00:49:15,340 --> 00:49:17,820
How long have you been here now?
460
00:49:17,820 --> 00:49:20,020
Over 30 years
since I started up here,
461
00:49:20,020 --> 00:49:23,460
so I've seen a lot of different
changes, you know.
462
00:49:23,460 --> 00:49:24,780
In what way?
463
00:49:24,780 --> 00:49:27,820
On the Cairngorm Plateau, there's
areas where we have snow patches
464
00:49:27,820 --> 00:49:28,980
lasting all the year round,
465
00:49:28,980 --> 00:49:31,020
but if you look at the last
sort of 20 years,
466
00:49:31,020 --> 00:49:34,540
there's five, six times where
the snow's completely gone,
467
00:49:34,540 --> 00:49:38,500
and in over sort of 200, 250 years,
there's only been seven times
468
00:49:38,500 --> 00:49:39,940
that that's happened.
469
00:49:39,940 --> 00:49:42,580
Has that had a great effect
on the wildlife?
470
00:49:42,580 --> 00:49:45,340
You know, they're out of kilter,
basically,
471
00:49:45,340 --> 00:49:47,140
with what's going on around them.
472
00:49:47,140 --> 00:49:49,100
So things like mountain hare,
ptarmigan,
473
00:49:49,100 --> 00:49:52,020
they're standing out with the browns
and the heather behind them.
474
00:49:52,020 --> 00:49:53,220
And they're still white?
475
00:49:53,220 --> 00:49:56,580
And they're still white, yes,
so they're not set up for that,
476
00:49:56,580 --> 00:49:58,820
so if it's a very poor winter,
477
00:49:58,820 --> 00:50:00,620
you know, they're suffering.
478
00:50:01,940 --> 00:50:04,220
Ptarmigan, a kind of grouse,
479
00:50:04,220 --> 00:50:07,540
live year-round
in this exposed environment
480
00:50:07,540 --> 00:50:10,180
where there are few places to hide.
481
00:50:16,500 --> 00:50:21,420
But now, as the world warms,
things are changing dangerously.
482
00:50:23,220 --> 00:50:28,260
The recent decrease in snow cover
has made them only too conspicuous.
483
00:50:32,500 --> 00:50:34,980
Animals like this mountain hare,
484
00:50:34,980 --> 00:50:38,420
also in its winter coat,
can be seen from far away...
485
00:50:40,660 --> 00:50:43,300
..and that makes life
very hazardous.
486
00:50:43,300 --> 00:50:44,340
BIRDS SQUAWK
487
00:50:45,700 --> 00:50:50,780
These changes are affecting animals
all around the northern hemisphere.
488
00:50:52,460 --> 00:50:57,940
In North America, the reduced snow
cover has caused snowshoe hares
489
00:50:57,940 --> 00:51:01,900
to be mismatched on average
for a week a year.
490
00:51:03,420 --> 00:51:06,620
During the time, the hare is 10%
more likely
491
00:51:06,620 --> 00:51:09,260
to end up as someone else's dinner.
492
00:51:10,740 --> 00:51:15,420
By the end of the century, the loss
of snow cover is predicted to expose
493
00:51:15,420 --> 00:51:18,220
the hares
for up to eight weeks a year,
494
00:51:18,220 --> 00:51:22,700
so increasing their annual
mortality by almost a quarter.
495
00:51:23,900 --> 00:51:26,020
Unless they can adapt rapidly,
496
00:51:26,020 --> 00:51:29,020
they could be in serious
danger of extinction.
497
00:51:33,300 --> 00:51:37,500
While a warming climate is causing
problems in northern habitats...
498
00:51:39,180 --> 00:51:43,420
..it's also driving colour changes
in other parts of the world...
499
00:51:47,100 --> 00:51:49,540
..including some
of the most beautiful,
500
00:51:49,540 --> 00:51:52,340
colour-rich habitats
on our planet...
501
00:51:53,980 --> 00:51:55,380
..coral reefs.
502
00:52:01,540 --> 00:52:06,500
Our Australian team spent months
filming on the Great Barrier Reef.
503
00:52:16,340 --> 00:52:20,380
In these sunlit waters,
colour is everywhere.
504
00:52:23,620 --> 00:52:26,500
But this habitat is being subjected
505
00:52:26,500 --> 00:52:30,380
to the most drastic colour
change imaginable,
506
00:52:30,380 --> 00:52:34,180
and our crew witnessed it
first-hand.
507
00:52:38,060 --> 00:52:42,300
The corals have suddenly
turned into white skeletons.
508
00:52:44,660 --> 00:52:47,620
It's called coral bleaching
509
00:52:47,620 --> 00:52:50,020
and it's now happening
only too frequently.
510
00:52:54,700 --> 00:52:56,540
On the Great Barrier Reef,
511
00:52:56,540 --> 00:53:01,420
such events have increased
from once in every 25 years
512
00:53:01,420 --> 00:53:04,100
to three events in the last five.
513
00:53:14,340 --> 00:53:17,780
Professor Jorg Wiedenmann
from the Coral Reef Laboratory
514
00:53:17,780 --> 00:53:20,140
at the University of Southampton
515
00:53:20,140 --> 00:53:23,940
has been working to discover
what is behind these changes.
516
00:53:26,220 --> 00:53:29,500
The key is the relationship
between coral
517
00:53:29,500 --> 00:53:33,300
and the microscopic algae
that live in their tissues.
518
00:53:36,180 --> 00:53:39,740
These algal partners
are called symbionts.
519
00:53:39,740 --> 00:53:42,620
It's they that give
the coral its colour.
520
00:53:44,300 --> 00:53:48,260
The algae, when they photosynthesise
during the daylight hours,
521
00:53:48,260 --> 00:53:53,420
use sunlight to grow,
excreting sugars as a by-product,
522
00:53:53,420 --> 00:53:56,060
which are then
absorbed by the corals.
523
00:54:00,340 --> 00:54:05,020
This partnership was established
during the time of the dinosaurs
524
00:54:05,020 --> 00:54:09,620
and has been such a success
that it has created structures
525
00:54:09,620 --> 00:54:11,260
that are visible from space.
526
00:54:12,580 --> 00:54:16,260
But warming seas are disrupting
this system.
527
00:54:16,260 --> 00:54:21,060
So, when the seawater temperatures
rise above a critical threshold,
528
00:54:21,060 --> 00:54:24,380
the photosynthetic machinery
of the algal symbionts
529
00:54:24,380 --> 00:54:26,020
starts to malfunction.
530
00:54:30,340 --> 00:54:33,580
They begin to produce toxic
compounds which cause
531
00:54:33,580 --> 00:54:36,660
the corals to expel them
from their tissues.
532
00:54:40,780 --> 00:54:43,380
So the coral loses its colour.
533
00:54:44,820 --> 00:54:46,500
It bleaches.
534
00:54:50,700 --> 00:54:56,220
Sometimes the bleached corals die,
and then the entire ecosystem,
535
00:54:56,220 --> 00:54:59,420
together with everything it
supports, is lost.
536
00:55:02,700 --> 00:55:06,780
Almost half of the corals
in the Great Barrier Reef
537
00:55:06,780 --> 00:55:10,460
have died this way
over the last 15 years.
538
00:55:16,100 --> 00:55:18,100
But in the last decade,
539
00:55:18,100 --> 00:55:21,220
there have been reports
from various parts of the world
540
00:55:21,220 --> 00:55:25,260
of coral developing
startling neon colours.
541
00:55:31,100 --> 00:55:33,180
We're just beginning to realise
542
00:55:33,180 --> 00:55:36,580
that corals are using colour
to fight back.
543
00:55:41,500 --> 00:55:44,620
Jorg is studying how this works.
544
00:55:45,980 --> 00:55:49,180
This coral has lost
its algal symbionts,
545
00:55:49,180 --> 00:55:50,860
but instead of turning white,
546
00:55:50,860 --> 00:55:53,860
it's producing these bright,
neon-green pigments.
547
00:55:56,300 --> 00:56:00,180
The coral produces these pigments
to protect the remaining algae
548
00:56:00,180 --> 00:56:04,300
inside of the tissue
from excess light stress.
549
00:56:04,300 --> 00:56:07,620
So they act as a sort of sunscreen
for the symbiont algae.
550
00:56:09,900 --> 00:56:14,700
This coral sunscreen makes it more
likely that the bleached coral
551
00:56:14,700 --> 00:56:17,660
will be able to take
back its algal partners,
552
00:56:17,660 --> 00:56:22,500
restoring its food supply, its
colour, and helping it to recover.
553
00:56:24,780 --> 00:56:28,660
But even this extraordinary
adaptation is not enough
554
00:56:28,660 --> 00:56:33,100
to protect coral against
all the changes it is now facing.
555
00:56:33,100 --> 00:56:36,940
If corals have been exposed
only to mild stress,
556
00:56:36,940 --> 00:56:38,540
then they can
recover from bleaching.
557
00:56:40,420 --> 00:56:43,020
But if corals are subjected
to prolonged
558
00:56:43,020 --> 00:56:45,300
or extreme levels of heat stress,
559
00:56:45,300 --> 00:56:49,740
they lose their ability to create
these sunscreen pigments
560
00:56:49,740 --> 00:56:51,340
and are likely to die.
561
00:56:52,620 --> 00:56:56,420
And unfortunately, global warming
is making this more likely.
562
00:56:57,860 --> 00:56:59,500
There's a severe danger
563
00:56:59,500 --> 00:57:03,780
that corals will be exposed to
episodes of stress
564
00:57:03,780 --> 00:57:07,220
where they can't recover and where
they can't use these pigments
565
00:57:07,220 --> 00:57:09,020
to bounce back from bleaching.
566
00:57:11,100 --> 00:57:13,500
So, although colour
might be helping coral reefs
567
00:57:13,500 --> 00:57:15,940
to tolerate some of the change,
568
00:57:15,940 --> 00:57:21,220
only action to halt global warming
will ensure their survival.
569
00:57:21,220 --> 00:57:24,500
If warming continues, then they,
570
00:57:24,500 --> 00:57:27,540
together with the beautiful array
of colour they provide,
571
00:57:27,540 --> 00:57:30,340
will disappear from the reefs
of the world.
46888
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