1
00:01:03,287 --> 00:01:06,085
(HE MAKES BIRD-LIKE CALL)

2
00:01:14,207 --> 00:01:16,596
(BIRD RESP0NDS)

3
00:01:18,487 --> 00:01:22,958
This bird is communicating directly with me.

4
00:01:23,127 --> 00:01:29,077
What's more, the call is one it only uses
when it's signalling to human beings,

5
00:01:29,247 --> 00:01:32,717
and its message is quite explicit and precise.

6
00:01:32,887 --> 00:01:38,484
It's saying, ''Follow me.'' It's just flown off, so
why don't we do just that and see what happens?

7
00:01:40,487 --> 00:01:43,559
The bird, here in Kenya, is a honey guide,

8
00:01:43,727 --> 00:01:47,561
and my companion has summoned it
with a special call.

9
00:01:50,207 --> 00:01:53,279
Man and bird have a mutual understanding

10
00:01:53,447 --> 00:01:59,522
which began in prehistory and which still today
enables them to speak to one another.

11
00:02:01,567 --> 00:02:07,517
The bird flies ahead, alights on a conspicuous
perch and then waits for us to catch up.

12
00:02:09,807 --> 00:02:14,801
We don't know how far it'll take us.
It may be a mile or so.

13
00:02:19,647 --> 00:02:24,516
Now the bird has stopped its chatter
and for the first time is perching low down.

14
00:02:24,687 --> 00:02:28,362
A buzzing is coming from the rocks
within a few yards of it.

15
00:02:31,687 --> 00:02:34,076
There are certainly some bees coming out,

16
00:02:34,247 --> 00:02:38,286
so with any luck there's some honey inside,
and if we can get it out,

17
00:02:38,447 --> 00:02:42,326
then we will be able to complete
our share of the bargain with that bird.

18
00:02:43,367 --> 00:02:46,200
African bees have got very effective stings,

19
00:02:46,367 --> 00:02:51,282
so it's sensible to stupefy them a bit with smoke
before you attempt to steal their honey.

20
00:02:58,007 --> 00:02:59,998
The bird sits quietly by,

21
00:03:00,167 --> 00:03:04,683
waiting for us to do
the part of the job that it can't manage.

22
00:03:15,247 --> 00:03:17,238
Mmm!

23
00:03:17,887 --> 00:03:19,878
It's delicious!

24
00:03:20,047 --> 00:03:23,403
If the bird hadn't shown us
where this bees' nest was,

25
00:03:23,567 --> 00:03:26,604
I'd have never got this sweet reward.

26
00:03:27,407 --> 00:03:32,879
But if we hadn't broken open the bees' nest,
the bird would never have got at the honey.

27
00:03:33,047 --> 00:03:38,679
So this is the result of a message
sent by a bird to a man.

28
00:03:39,327 --> 00:03:44,276
Since it is a partnership, it's only fair
that the bird should get a reward.

29
00:03:44,447 --> 00:03:48,042
So it's the custom in these parts
not to take all the honey,

30
00:03:48,207 --> 00:03:51,199
but to leave some of it for the bird.

31
00:03:54,687 --> 00:03:59,397
So two different species solve
the trial of talking to strangers.

32
00:03:59,567 --> 00:04:05,199
You have to get your message through,
and not only to friends but to enemies.

33
00:04:21,847 --> 00:04:26,716
As the wild dogs start hunting,
the gazelles don't simply run away.

34
00:04:27,687 --> 00:04:32,203
They make these extraordinary leaps. They stot.

35
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This action is a message which says, in effect,

36
00:04:44,487 --> 00:04:48,799
''My jumps show that I am strong
and could probably outrun you.

37
00:04:48,967 --> 00:04:52,721
''Someone else would be an easier catch.''

38
00:05:01,767 --> 00:05:06,318
As the dogs rush across the plain,
they choose which gazelle to go for

39
00:05:06,487 --> 00:05:09,081
on the basis of this information.

40
00:05:31,127 --> 00:05:33,482
These messages are truthful,

41
00:05:33,647 --> 00:05:37,640
for the frequency of a gazelle's leaps
do indicate its strength.

42
00:05:40,247 --> 00:05:44,843
And the dogs hardly ever select
those that stot with vigour.

43
00:05:51,807 --> 00:05:56,198
Interestingly, the gazelles rarely stot
when pursued by a cheetah,

44
00:05:56,367 --> 00:06:01,236
for the cheetah selects its prey before
the chase begins and catches it with a sprint.

45
00:06:01,407 --> 00:06:03,796
There's no time for messages.

46
00:06:05,047 --> 00:06:07,880
But with dogs, it's different.

47
00:06:09,527 --> 00:06:13,679
Dogs are not sprinters,
they're long-distance runners,

48
00:06:13,847 --> 00:06:16,919
and they catch their victims by tiring them out.

49
00:06:20,487 --> 00:06:23,047
A gazelle's message is inevitably honest.

50
00:06:23,207 --> 00:06:26,517
A weak individual can't counterfeit strength.

51
00:06:26,687 --> 00:06:29,599
But animals don't always tell the truth.

52
00:06:29,767 --> 00:06:32,520
This bird, for example, tells downright lies.

53
00:06:35,127 --> 00:06:40,281
It's a ringed plover, and it makes its nest
on the shingle of European beaches.

54
00:06:41,807 --> 00:06:44,275
Its eggs are perfectly camouflaged.

55
00:06:44,447 --> 00:06:49,043
The bird itself, when sitting on them,
is much more obvious than they would be.

56
00:06:53,407 --> 00:06:56,797
So when danger threatens,
the logical course is clear.

57
00:06:59,287 --> 00:07:02,882
A possible predator like me
is unlikely to find the eggs

58
00:07:03,047 --> 00:07:08,644
and much more likely to follow the bird, and
the bird has a way of persuading me to do so.

59
00:07:08,807 --> 00:07:11,719
(C0NSTANT CHIRPING)

60
00:07:11,887 --> 00:07:15,926
It's saying, in effect,
''I'm injured. I've got a broken wing.

61
00:07:16,087 --> 00:07:20,080
''If you're looking for an easy meal,
why not pick me up?''

62
00:07:31,487 --> 00:07:33,717
But, of course, it's not true.

63
00:07:33,887 --> 00:07:36,845
It's just a device to lure me away from its eggs.

64
00:07:38,847 --> 00:07:41,645
Suddenly, its broken wing gets better.

65
00:07:41,807 --> 00:07:47,404
Since I'm now so far away from its nest
that I'm no longer likely to blunder into its eggs,

66
00:07:47,567 --> 00:07:50,161
back it goes.

67
00:07:51,687 --> 00:07:57,239
Whether honest or dishonest, communication
often demands a great deal from the sender.

68
00:07:59,287 --> 00:08:02,085
A skylark sings for hours, high in the sky,

69
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to proclaim ownership of the territory beneath.

70
00:08:05,007 --> 00:08:07,396
This not only uses up energy,

71
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but also risks the attention
of one of their main predators - the merlin.

72
00:08:19,607 --> 00:08:24,601
Amazingly, even while they're being chased,
many larks continue to sing.

73
00:08:25,767 --> 00:08:28,156
(SINGING)

74
00:08:29,887 --> 00:08:34,005
The meaning of this song
is the same as the stot of the gazelles.

75
00:08:34,167 --> 00:08:37,637
''I'm fit. You won't catch me.
Chase a weaker bird.''

76
00:08:48,167 --> 00:08:52,365
And the evidence for that -
in 80% of these encounters,

77
00:08:52,527 --> 00:08:57,647
merlins either ignore or quickly stop
chasing birds that continue to sing.

78
00:08:57,807 --> 00:09:02,164
The ones they pursue
are nearly always the silent ones.

79
00:09:13,567 --> 00:09:17,719
The skylark's song, like that
of most birds that live on grasslands,

80
00:09:17,887 --> 00:09:20,606
is high-pitched and very complex

81
00:09:20,767 --> 00:09:24,885
because that kind of song
travels well over open country.

82
00:09:25,047 --> 00:09:29,916
And obviously the way an animal communicates
must be governed to a considerable degree

83
00:09:30,087 --> 00:09:32,476
by the sort of place in which it lives.

84
00:09:32,647 --> 00:09:34,683
Here in Israel, for example,

85
00:09:34,847 --> 00:09:39,875
there's an animal that spends
its entire life underground.

86
00:09:40,047 --> 00:09:44,165
Molehills like these are normally
the only sign one has of its presence.

87
00:09:44,327 --> 00:09:48,525
It's totally blind, it can hardly smell,
and it has very poor hearing,

88
00:09:48,687 --> 00:09:51,804
and yet individuals 40 or 50 yards apart

89
00:09:51,967 --> 00:09:55,721
can communicate with one another
through the solid earth.

90
00:09:56,487 --> 00:09:59,047
This is a geophone.

91
00:09:59,207 --> 00:10:03,246
Basically, it's just a device which turns
vibrations in the ground into sound

92
00:10:03,407 --> 00:10:06,205
which I can hear and record on this.

93
00:10:06,367 --> 00:10:10,485
With it, maybe I can have
an underground conversation.

94
00:10:12,087 --> 00:10:14,601
That's my message.

95
00:10:17,167 --> 00:10:19,158
- (THUDDING)
- And there's a reply.

96
00:10:22,727 --> 00:10:27,676
The animal's not hearing sound, it's just
responding to vibrations in the ground.

97
00:10:30,447 --> 00:10:33,325
I'm talking to a mole rat.

98
00:10:34,527 --> 00:10:38,679
This hairy mole rat, very different
from the naked mole rat of Africa,

99
00:10:38,847 --> 00:10:43,477
sends messages by beating
the roof of the tunnel with its head

100
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and receives them by pressing its jaw
against the tunnel wall to feel the vibration.

101
00:10:49,447 --> 00:10:53,486
They burrow continuously,
and their tunnels extend for hundreds of yards,

102
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winding circuitously
and often crossing those of others,

103
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as they search for roots and tubers.

104
00:11:00,567 --> 00:11:03,559
But outside the breeding season
they're very antisocial

105
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and they do all they can to avoid
meeting a rival coming the other way.

106
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So they constantly send signals
saying where they are

107
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and listen out for messages from others.

108
00:11:34,927 --> 00:11:37,236
They exchange challenges.

109
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Who will give way?

110
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If they're both so confident of themselves
that they ignore these warnings

111
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and the two tunnels actually meet,
then there is always a fight.

112
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Unless one retires and surrenders its tunnel,
this can only end in the death of one of them.

113
00:12:25,407 --> 00:12:30,242
Soil is not the only medium
that can be used to carry messages.

114
00:12:32,887 --> 00:12:38,484
By shaking their bodies, lacewings
send vibrations down stems and leaves.

115
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Special equipment converts these
into sounds which we can hear

116
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and different species use characteristic
frequencies and rhythms.

117
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(L0W VIBRATI0N)

118
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(PR0L0NGED VIBRATI0N)

119
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(RHYTHMIC VIBRATI0N)

120
00:13:03,807 --> 00:13:08,198
Lacewings are tiny and their quiverings travel
just a couple of inches,

121
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so they're only detectable at close quarters,

122
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but they reassure males and females
that they are suitable mates.

123
00:13:20,247 --> 00:13:23,637
Even the surfaces of ponds carry messages.

124
00:13:23,807 --> 00:13:27,641
A male water strider
creates ripples with its front legs.

125
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This lily pad is his territory and
his rippled message will travel up to a yard.

126
00:13:47,447 --> 00:13:51,804
A stranger. It, too, creates ripples,
which means that it's a rival,

127
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for females don't communicate in this way.

128
00:13:56,887 --> 00:14:02,200
To send messages further still,
you have to make vibrations in the air. Sound.

129
00:14:05,407 --> 00:14:09,605
This palm cockatoo deliberately breaks off
branches to use as drumsticks

130
00:14:09,767 --> 00:14:12,565
and beats out his claims for this nest hole.

131
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And he backs up his messages
with ear-splitting calls.

132
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(SQUAWKS)

133
00:14:33,087 --> 00:14:36,875
Sound travels best
when the air is cool and still,

134
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at dawn.

135
00:14:39,007 --> 00:14:43,603
The songs that penetrate farthest through
the foliage of the forest are not complex,

136
00:14:43,767 --> 00:14:46,235
like the skylark's, but simple.

137
00:14:52,727 --> 00:14:54,160
(SQUAWKS)

138
00:14:54,327 --> 00:14:57,683
The bell bird's call
can be heard three miles away.

139
00:15:05,007 --> 00:15:06,998
(SQUAWKS)

140
00:15:07,167 --> 00:15:09,727
(''W0LF WHISTLE'' CALL)

141
00:15:09,887 --> 00:15:15,086
The aptly named screaming piha
produces a call almost as ear-splitting.

142
00:15:20,287 --> 00:15:24,883
With a call like that, you don't need
bright feathers to impress a mate,

143
00:15:25,047 --> 00:15:27,436
and the piha is not only drably dressed,

144
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but sends its piercing messages
from inconspicuous perches in the undergrowth.

145
00:15:33,527 --> 00:15:38,647
Up to eight males will sit in a small patch
of forest trying to outscream one another

146
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in a competition to attract a passing female.

147
00:15:45,287 --> 00:15:48,677
When male and female birds
do eventually pair in the forest,

148
00:15:48,847 --> 00:15:53,716
they may need to keep in touch with one another
and some do that by singing duets.

149
00:15:54,487 --> 00:15:56,717
(H00TING CALLS)

150
00:15:56,887 --> 00:15:59,355
The African round hornbill.

151
00:16:08,687 --> 00:16:12,680
Duetting like this
is obviously useful in thick vegetation,

152
00:16:12,847 --> 00:16:18,046
but the birds may do it wherever they are,
so strengthening the bond between them.

153
00:16:26,007 --> 00:16:29,522
Calls in the forest
also serve to keep animals apart.

154
00:16:29,687 --> 00:16:32,076
This is Madagascar.

155
00:16:34,127 --> 00:16:36,641
(L0UD WH00PING CALL)

156
00:16:47,287 --> 00:16:49,721
The indri, the largest of lemurs.

157
00:16:49,887 --> 00:16:54,961
They live in families -
a male, a female with her baby

158
00:16:56,207 --> 00:16:59,404
and, often, a half-grown youngster.

159
00:17:03,367 --> 00:17:05,676
The female is the lead singer.

160
00:17:11,927 --> 00:17:17,718
The group's message proclaims its ownership
of a territory and of the food it contains.

161
00:17:20,007 --> 00:17:24,046
Neighbours, when they hear it,
defiantly respond with their own claims,

162
00:17:24,207 --> 00:17:28,598
so soon the forest is ringing
with the calls of many groups.

163
00:17:37,127 --> 00:17:39,687
(INCREASING DIN 0F CALLS)

164
00:17:46,367 --> 00:17:51,600
The chorus is a marvellous one,
but each call, in structure, is simple.

165
00:17:51,767 --> 00:17:55,999
The Malaysian forest at dawn
awakes to a much more complex song.

166
00:17:57,247 --> 00:18:00,045
(DISTANT WH00PING)

167
00:18:05,287 --> 00:18:08,563
These calls are a well-structured
and intricate duet.

168
00:18:08,727 --> 00:18:12,879
They're made by the black gibbon, the siamang.

169
00:18:26,087 --> 00:18:31,081
The male starts, his voice amplified
by a resonating throat pouch.

170
00:18:32,887 --> 00:18:35,355
The female joins in.

171
00:18:39,487 --> 00:18:41,876
The male screams

172
00:18:42,047 --> 00:18:44,038
and the female barks again.

173
00:18:47,047 --> 00:18:51,723
And, for the finale, the whole family
crashes about in the branches.

174
00:18:55,687 --> 00:19:00,841
Singing together like this serves to bind a pair
in a partnership that lasts a lifetime,

175
00:19:01,007 --> 00:19:03,680
but it's primarily a way of declaring ownership

176
00:19:03,847 --> 00:19:07,203
and ensures that gibbon families
are well spread out,

177
00:19:07,367 --> 00:19:10,962
each knowing the whereabouts
and identity of its neighbours

178
00:19:11,127 --> 00:19:15,120
and so avoiding
unnecessary territorial squabbles.

179
00:19:18,287 --> 00:19:22,519
0ther calls that cleverly establish
who is who and who is where

180
00:19:22,687 --> 00:19:26,646
can be heard on the banks
of the Tana river in Kenya.

181
00:19:32,007 --> 00:19:33,998
A mangabey.

182
00:19:34,167 --> 00:19:40,083
Unlike the indri and the siamang, these monkeys
don't defend a permanent territory.

183
00:19:40,247 --> 00:19:45,719
Instead, they are constantly searching
for an unpredictable food supply.

184
00:19:49,527 --> 00:19:53,076
Having found it,
they lay claim to it with a two-part call.

185
00:19:53,247 --> 00:19:57,126
The first section, a whoop,
means simply, ''Listen.''

186
00:20:02,007 --> 00:20:06,876
The second part, a kind of gobble,
is a statement of who they are.

187
00:20:07,047 --> 00:20:10,960
0n hearing it,
the males take up listening positions.

188
00:20:12,727 --> 00:20:16,037
The gobble part of the call
is slightly different for each group,

189
00:20:16,207 --> 00:20:19,005
so the males know exactly who is around.

190
00:20:26,087 --> 00:20:29,318
There are two ways of responding to this threat.

191
00:20:29,487 --> 00:20:31,921
If food is short,
everyone rushes out to defend it

192
00:20:32,087 --> 00:20:35,159
with a display of aggressive yawns.

193
00:20:36,447 --> 00:20:40,963
But if there's plenty for everyone,
they just ignore it.

194
00:20:43,487 --> 00:20:47,878
The most complex of all monkey communications
so far analysed, however,

195
00:20:48,047 --> 00:20:52,120
can be heard on the shores
of Lake Naivasha in Kenya's Rift Valley.

196
00:21:03,087 --> 00:21:08,878
At dawn, vervet monkeys come down from
the trees to search for food on the ground.

197
00:21:19,527 --> 00:21:23,918
Down here, of course, they're much
more vulnerable than in the trees,

198
00:21:24,087 --> 00:21:26,476
but there's always a sentinel on watch.

199
00:21:37,287 --> 00:21:40,438
The sentinel gives a call which means, ''Snake!''

200
00:21:41,287 --> 00:21:43,278
(CLICKING N0ISE)

201
00:21:48,967 --> 00:21:53,438
The meaning is very precise
and is only made when a snake appears.

202
00:21:53,607 --> 00:21:57,361
It could be called a word,
and when other vervets hear it,

203
00:21:57,527 --> 00:22:00,121
they know exactly what the danger is.

204
00:22:03,727 --> 00:22:08,118
Calls with such specific meanings
are very rare in the animal world,

205
00:22:08,287 --> 00:22:11,563
but vervets have developed several of them.

206
00:22:13,047 --> 00:22:15,845
Apart from man, no other animal in the wild

207
00:22:16,007 --> 00:22:20,797
has been shown to use
so many different word-like alarm calls.

208
00:22:29,727 --> 00:22:31,957
A call that means, ''Danger from the air!''

209
00:22:33,407 --> 00:22:37,446
The vervets run into the denser branches
where the eagle won't go

210
00:22:37,607 --> 00:22:39,757
for fear of damaging its wings.

211
00:22:45,687 --> 00:22:50,807
From the safety of the thorny branches,
the vervets scream furiously.

212
00:22:50,967 --> 00:22:55,279
And one is even brave enough
to launch a lightning attack.

213
00:23:00,407 --> 00:23:06,801
Monkeys are not the only ones to fear eagles -
so do small birds, such as the superb starling.

214
00:23:14,327 --> 00:23:17,683
Vervets understand the starling's vocabulary.

215
00:23:19,327 --> 00:23:23,479
The bird shrieks a warning,
''Danger on the ground!''

216
00:23:23,647 --> 00:23:29,199
The monkeys repeat it
using their own term, and everyone runs for it.

217
00:23:34,767 --> 00:23:38,760
So vervets,
with such a wide vocabulary of alarm calls,

218
00:23:38,927 --> 00:23:42,920
show that sound can carry
a great deal of vital information,

219
00:23:43,087 --> 00:23:47,080
a function that becomes
even more important at night.

220
00:23:51,087 --> 00:23:55,399
With the coming of darkness,
everybody seems to be using sound,

221
00:23:55,567 --> 00:23:58,035
and that can be a problem.

222
00:23:59,487 --> 00:24:04,481
In a Panama swamp, fifteen different species
of frog are starting to sing.

223
00:24:09,127 --> 00:24:12,403
In this tumult,
it's very difficult to make yourself heard,

224
00:24:12,567 --> 00:24:17,083
but males of this species, starting
on their serenades, carefully time their calls

225
00:24:17,247 --> 00:24:20,000
to fit in between those of their neighbours.

226
00:24:21,967 --> 00:24:23,958
(''CRICK-CRICK'' S0UND )

227
00:24:31,287 --> 00:24:34,085
To our ears, the calls may sound continuous,

228
00:24:34,247 --> 00:24:39,480
but a female frog is able to select the male
with the loudest call and will mate with him.

229
00:24:46,967 --> 00:24:50,880
Males of this species, however,
deliberately jam one another.

230
00:24:57,247 --> 00:25:01,525
The female pays most attention
to the second half of the call,

231
00:25:01,687 --> 00:25:06,238
so if a rival starts up nearby,
a male deliberately re-times his call

232
00:25:06,407 --> 00:25:11,197
so that the first part exactly jams
the second crucial part of his neighbour's.

233
00:25:14,407 --> 00:25:17,001
(0VERLAPPING CALLS)

234
00:25:18,367 --> 00:25:23,282
A male, frustrated in this way,
will resort to violence,

235
00:25:23,447 --> 00:25:27,838
but the intruder goes on calling,
even as they wrestle.

236
00:25:42,487 --> 00:25:48,881
So, every evening, there is a continuous battle
for the supremacy of the airwaves.

237
00:25:58,447 --> 00:26:01,996
Sound is not the only way
of communicating at night.

238
00:26:02,167 --> 00:26:05,477
When the sun goes down
on the tidal rivers of Malaysia,

239
00:26:05,647 --> 00:26:11,165
the trees on the banks become alive
with animals communicating with light.

240
00:26:14,927 --> 00:26:18,920
At first, there are just
a few twinkles in the branches,

241
00:26:19,087 --> 00:26:23,956
but about three quarters of an hour
after sunset, the show begins.

242
00:26:50,687 --> 00:26:56,637
These are fireflies, thousands and thousands
of tiny beetles only about 5mm long,

243
00:26:56,807 --> 00:27:02,120
each sending a message in Morse code
with a lantern in its abdomen.

244
00:27:02,287 --> 00:27:05,404
All those that are flashing are males,

245
00:27:05,567 --> 00:27:09,446
and their message is directed
to the females, and it's a simple one:

246
00:27:09,607 --> 00:27:11,723
''Come hither, mate with me.''

247
00:27:11,887 --> 00:27:17,405
This particular species, as well as
one or two others here in South-East Asia,

248
00:27:17,567 --> 00:27:22,243
reinforce that message and send it
the farthest possible distance

249
00:27:22,407 --> 00:27:26,605
by all flashing in perfect time together,
in perfect synchrony.

250
00:27:26,767 --> 00:27:31,522
The result is that, even after
I've drifted many yards downriver,

251
00:27:31,687 --> 00:27:37,159
looking back I can still see
their tree outlined with pulsing light.

252
00:27:50,847 --> 00:27:55,796
This display continues throughout
the hours of darkness every night of the year

253
00:27:55,967 --> 00:27:58,720
and extends for miles along the river.

254
00:27:58,887 --> 00:28:02,516
The combined light
of all these tiny beetles is so bright

255
00:28:02,687 --> 00:28:06,726
that fishermen out at sea can use them
as navigating beacons

256
00:28:06,887 --> 00:28:10,277
to guide them back to their home rivers.

257
00:28:10,447 --> 00:28:16,397
0nly in South-East Asia do fireflies coordinate
their flashings in this spectacular way.

258
00:28:16,567 --> 00:28:19,923
Elsewhere in the world,
fireflies operate independently,

259
00:28:20,087 --> 00:28:24,956
each beaming its own
individual invitation to mate.

260
00:28:27,327 --> 00:28:32,003
Walk in the woodlands of the eastern
United States at dusk in summer,

261
00:28:32,167 --> 00:28:35,443
and you can find fireflies all around you.

262
00:28:35,607 --> 00:28:39,646
What's more, with these
you can actually communicate,

263
00:28:39,807 --> 00:28:43,004
if you have a small torch like this.

264
00:28:44,927 --> 00:28:49,398
To communicate with the males,
which are flying a foot above the ground,

265
00:28:49,567 --> 00:28:53,719
I have to accurately imitate the call of a female.

266
00:28:53,887 --> 00:28:56,117
In the species that's flashing now,

267
00:28:56,287 --> 00:29:00,678
the female observes the flash of the male
and then waits two seconds

268
00:29:00,847 --> 00:29:05,284
and produces a half-second flash
of her own like this.

269
00:29:05,767 --> 00:29:08,156
Let's see if I can do it.

270
00:29:10,687 --> 00:29:13,076
Ah! There's one!

271
00:29:14,727 --> 00:29:17,685
Flash, two...for me.

272
00:29:19,807 --> 00:29:23,197
0ne, two, flash. He's coming.

273
00:29:24,047 --> 00:29:27,483
Flash from him, one, two, flash from me.

274
00:29:27,647 --> 00:29:30,207
Here he comes. Here he comes!

275
00:29:31,007 --> 00:29:34,317
There we are. He's settled on my finger.

276
00:29:38,047 --> 00:29:40,641
Got him!

277
00:29:40,807 --> 00:29:42,798
There he is.

278
00:29:46,487 --> 00:29:49,684
Well, I'm afraid I'm a disappointment to you.

279
00:29:53,007 --> 00:29:56,238
Communication with light
is not restricted to the land.

280
00:29:56,407 --> 00:29:58,796
It's even more widely used in the sea.

281
00:30:02,087 --> 00:30:04,999
This bay in Bermuda, on a few nights each month,

282
00:30:05,167 --> 00:30:08,842
puts on a particularly dramatic light show.

283
00:30:12,287 --> 00:30:17,281
About an hour after sunset,
strange lights appear in the water.

284
00:30:23,887 --> 00:30:26,720
They're produced by female fireworms.

285
00:30:26,887 --> 00:30:29,321
As each one spirals on the surface,

286
00:30:29,487 --> 00:30:34,038
she releases two substances from
different glands, which, as they combine,

287
00:30:34,207 --> 00:30:36,721
generate this chemical light.

288
00:30:47,167 --> 00:30:49,556
Each is a sexual summons.

289
00:30:49,727 --> 00:30:55,006
The males, who have big eyes,
respond by swimming swiftly towards them

290
00:30:55,167 --> 00:30:57,635
emitting a chain of brief flashes.

291
00:31:09,447 --> 00:31:13,360
As a male arrives,
she releases another cloud of light

292
00:31:13,527 --> 00:31:17,520
and, with it, her eggs, which he then fertilises.

293
00:31:19,847 --> 00:31:24,443
After 10 minutes,
the bay is thick with rising females.

294
00:31:28,727 --> 00:31:32,276
This mating fiesta can only occur
on nights when the moon rises

295
00:31:32,447 --> 00:31:34,438
after it's already dark.

296
00:31:34,607 --> 00:31:39,397
0nce it's high in the sky, its light on the water
would overwhelm that of the worms.

297
00:31:39,567 --> 00:31:44,004
The males would no longer be able
to discern their luminous invitations.

298
00:31:44,167 --> 00:31:49,161
After 20 minutes, the females sink
back to the depths. The show is over.

299
00:32:04,687 --> 00:32:08,999
If you want to find the greatest
number and variety of animals

300
00:32:09,167 --> 00:32:14,400
that communicate with light,
you have to go to the darkest place on Earth,

301
00:32:14,567 --> 00:32:18,606
somewhere far beyond
the reach of the sun's rays,

302
00:32:18,767 --> 00:32:22,840
where human beings hardly ever go -
to the depths of the ocean.

303
00:32:23,727 --> 00:32:26,161
This is the Johnson Sealink.

304
00:32:26,327 --> 00:32:31,526
At the front is an array of remotely controlled
television cameras and searchlights.

305
00:32:31,687 --> 00:32:35,316
I'm sitting beside the pilot
in the bubble in the middle,

306
00:32:35,487 --> 00:32:37,921
and the whole craft is massively strengthened

307
00:32:38,087 --> 00:32:40,885
to withstand the huge pressures of the depths.

308
00:32:45,327 --> 00:32:48,956
As we go down, it gets darker and darker.

309
00:32:50,887 --> 00:32:54,960
The water is thick with small floating organisms.

310
00:33:01,287 --> 00:33:07,806
At 600 feet, the water outside
is 20 times atmospheric pressure,

311
00:33:07,967 --> 00:33:11,004
the temperature is within
a few degrees of freezing

312
00:33:11,167 --> 00:33:14,125
and we are far beyond the reach of the sunshine.

313
00:33:14,287 --> 00:33:17,006
You might think in such a hostile environment

314
00:33:17,167 --> 00:33:20,682
there would be very few animals living,
but watch this.

315
00:33:23,247 --> 00:33:28,446
The chorus of lights is being made
by hundreds of small deep-sea creatures

316
00:33:28,607 --> 00:33:31,440
which are flashing in response to my light.

317
00:33:37,567 --> 00:33:41,606
And now,
if I turn on the lights of the submersible,

318
00:33:41,767 --> 00:33:46,795
we may catch a glimpse of one of these
strange deep-sea creatures as it drifts by.

319
00:33:48,007 --> 00:33:52,000
The pilot has remote controls
for the camera outside the sub

320
00:33:52,167 --> 00:33:54,886
to search for them in the blackness.

321
00:33:58,327 --> 00:34:01,444
This is a comb jelly as big as a football.

322
00:34:01,607 --> 00:34:05,998
It's been nicknamed ''Big Red'',
but it has yet to be given a proper name.

323
00:34:06,167 --> 00:34:08,158
It's new to science.

324
00:34:10,327 --> 00:34:12,716
Another new, undescribed comb jelly.

325
00:34:12,887 --> 00:34:15,242
Although specimens have been brought up,

326
00:34:15,407 --> 00:34:20,322
it's only been seen alive through the windows
of deep-sea craft like this.

327
00:34:20,487 --> 00:34:25,242
It uses a pair of long
retractable tentacles to catch fish.

328
00:34:30,607 --> 00:34:33,644
A jellyfish, Solmissus, two feet across,

329
00:34:33,807 --> 00:34:39,325
which, in spite of the changes of pressure,
sometimes swims quite close to the surface.

330
00:34:45,567 --> 00:34:47,683
Kiyohimea, another comb jelly,

331
00:34:47,847 --> 00:34:50,998
one that is surrounded by gauzy skirts.

332
00:34:56,287 --> 00:35:01,839
But for the most sensational spectacle,
you have to turn the lights of the submarine off.

333
00:35:06,287 --> 00:35:11,202
A jellyfish outlined
by its own pulsing illuminations.

334
00:35:19,767 --> 00:35:23,555
A squid, its lights moving as its body throbs.

335
00:35:23,727 --> 00:35:27,686
Displays like this may serve
for defence or to send messages.

336
00:35:27,847 --> 00:35:30,042
No one knows.

337
00:35:34,207 --> 00:35:36,323
And most spectacular of all,

338
00:35:36,487 --> 00:35:41,481
another jellyfish with its own
amazing rhythmic flashing system.

339
00:35:52,887 --> 00:35:55,276
The Golden Gate Bridge, San Francisco.

340
00:35:55,447 --> 00:35:58,883
In one of the smaller bays
that rim this superb harbour,

341
00:35:59,047 --> 00:36:03,120
the wealthier citizens
have taken to living on boats.

342
00:36:03,287 --> 00:36:05,323
A few years ago,

343
00:36:05,487 --> 00:36:09,958
when the campaign to clear up San Francisco Bay
was just beginning to have an effect,

344
00:36:10,127 --> 00:36:14,120
the people who lived here
on these houseboats in Sausalito found

345
00:36:14,287 --> 00:36:18,280
that the quietness of their lifestyle
was being interrupted

346
00:36:18,447 --> 00:36:21,086
by a strange and very irritating noise.

347
00:36:21,247 --> 00:36:26,002
What's more, it was inescapable.
They could hear it out here over the water,

348
00:36:26,167 --> 00:36:29,603
but inside it was even louder.

349
00:36:29,767 --> 00:36:33,999
Every night, throughout the summer,
at around nine o'clock,

350
00:36:34,167 --> 00:36:39,002
this strange noise would reverberate
through the houseboat as it's doing now.

351
00:36:39,167 --> 00:36:43,365
0ften it went on all night,
preventing people from sleeping.

352
00:36:43,527 --> 00:36:45,916
There were various theories about its cause.

353
00:36:46,087 --> 00:36:50,717
Some people suggested
that it was the local sewage company

354
00:36:50,887 --> 00:36:53,685
secretly pumping effluent into the bay at night.

355
00:36:53,847 --> 00:36:59,763
0thers tried to sue the electricity company,
which had recently laid a cable across the bay.

356
00:36:59,927 --> 00:37:04,921
But, finally, a marine biologist suggested
that it came from an animal.

357
00:37:05,087 --> 00:37:09,399
And we can prove that he was right
by playing back the sound

358
00:37:09,567 --> 00:37:11,956
through an underwater speaker.

359
00:37:16,567 --> 00:37:19,081
(EERIE HUM)

360
00:37:20,927 --> 00:37:24,761
A toadfish. Normally a shy, skulking creature.

361
00:37:31,887 --> 00:37:34,276
And not just one. Several.

362
00:37:34,447 --> 00:37:39,043
They're all females
and they seem to find the sound irresistible.

363
00:37:44,447 --> 00:37:47,519
Sound travels far more easily
through water than through air

364
00:37:47,687 --> 00:37:52,238
and females are attracted to the speaker
from considerable distances.

365
00:37:57,007 --> 00:38:01,842
This is the fish that created the sound
in the first place - the male toadfish.

366
00:38:02,007 --> 00:38:05,204
He does it by vibrating his swim bladder.

367
00:38:05,367 --> 00:38:07,756
(C0NTINU0US HUM)

368
00:38:12,487 --> 00:38:17,402
He's guarding an old abalone shell
within which he has young.

369
00:38:21,407 --> 00:38:25,116
The babies are of different sizes.
There are several broods here.

370
00:38:25,287 --> 00:38:29,678
A succession of females have
laid their eggs in his nest, each attracted,

371
00:38:29,847 --> 00:38:33,044
one after the other, by his song.

372
00:38:35,887 --> 00:38:38,560
And it's not only his song that brings them.

373
00:38:38,727 --> 00:38:41,287
He has spots along his flanks.

374
00:38:41,447 --> 00:38:43,563
Each one is a light

375
00:38:43,727 --> 00:38:48,357
and he treats his females
to a full show of ''son et lumiére''.

376
00:38:53,487 --> 00:38:56,126
The undersea world is full of sound.

377
00:38:56,287 --> 00:39:00,280
0ver 200 species of fish
create simple sound messages

378
00:39:00,447 --> 00:39:02,836
that travel easily through the water.

379
00:39:11,487 --> 00:39:16,242
Sea lions, which evolved on land
but spend so much of their time at sea,

380
00:39:16,407 --> 00:39:21,401
have developed ears that enable them to hear
all these sounds much more clearly than we can.

381
00:39:42,847 --> 00:39:46,601
They haven't got special ways
of making underwater sounds themselves,

382
00:39:46,767 --> 00:39:50,157
but, on occasion, they bark as they do on land.

383
00:39:50,327 --> 00:39:52,124
(BARKING)

384
00:39:58,687 --> 00:40:02,680
Tusked whales - narwhals,
the unicorns of the sea.

385
00:40:04,287 --> 00:40:06,676
They joust on the surface.

386
00:40:07,287 --> 00:40:10,518
Underwater, they produce a tumult of sound.

387
00:40:12,687 --> 00:40:15,281
(BLEEPS AND CRIES)

388
00:40:28,407 --> 00:40:31,638
The female narwhal has no tusk,
but, like the male,

389
00:40:31,807 --> 00:40:35,197
she does have a huge bulge on her forehead.

390
00:40:35,367 --> 00:40:38,916
From this comes a stream of high-pitched clicks.

391
00:40:39,087 --> 00:40:41,476
These, by a form of echo location,

392
00:40:41,647 --> 00:40:44,684
enable a narwhal to detect obstacles
out of sight ahead

393
00:40:44,847 --> 00:40:49,796
and also, grouped together in pulses,
may serve to identify individuals.

394
00:40:55,287 --> 00:40:59,997
But they also make a great variety
of other sounds - groaning and squealing

395
00:41:00,167 --> 00:41:03,557
and blowing bubbles through their blowholes.

396
00:41:03,727 --> 00:41:08,960
Sound travels so well through water that the big
whales, which can make immensely loud calls,

397
00:41:09,127 --> 00:41:13,120
can probably communicate
over several hundred miles.

398
00:41:16,287 --> 00:41:21,156
But narwhals are by no means
the most loquacious animals in the sea.

399
00:41:26,087 --> 00:41:30,683
These creatures can't communicate with sound
for they are totally deaf,

400
00:41:30,847 --> 00:41:34,396
but they can send and receive
such complex messages

401
00:41:34,567 --> 00:41:37,843
that they could be considered
to be carrying on a conversation.

402
00:41:38,007 --> 00:41:41,636
And they do it entirely visually. They are squid.

403
00:41:41,807 --> 00:41:45,959
The variety and subtlety
of their colour changes are so great

404
00:41:46,127 --> 00:41:51,155
that it's hardly possible for us to keep up
with their conversational exchanges.

405
00:42:02,087 --> 00:42:06,763
They produce these changes of colour
and pattern with tiny sacs of pigment

406
00:42:06,927 --> 00:42:09,600
which can expand from an almost invisible speck

407
00:42:09,767 --> 00:42:12,964
to a large blotch and back again
in a fraction of a second.

408
00:42:13,127 --> 00:42:17,166
They're all under the control
of a highly complex nervous system.

409
00:42:22,167 --> 00:42:26,160
It's not only colour changes they use
in their visual conversations -

410
00:42:26,327 --> 00:42:29,125
the position of the body also has significance.

411
00:42:29,287 --> 00:42:32,757
Researchers have so far
discovered 35 different postures

412
00:42:32,927 --> 00:42:35,236
which act, as it were, as adverbs,

413
00:42:35,407 --> 00:42:40,356
qualifying the intensity of the message
sent by the colour change.

414
00:42:41,287 --> 00:42:45,678
This male reef squid appears to be
saying nothing, seen from this side.

415
00:42:45,847 --> 00:42:51,843
Its flank is a blank. But his other side
is vivid with swift colour changes.

416
00:42:52,007 --> 00:42:54,999
He's chatting up the female beside him.

417
00:42:55,607 --> 00:43:00,920
Rival males passing by
would never know what he's up to.

418
00:43:04,127 --> 00:43:06,766
The male at the back
has developed a striped pattern.

419
00:43:06,927 --> 00:43:09,077
That's an invitation to mate.

420
00:43:09,247 --> 00:43:12,080
The female goes white - that's a refusal.

421
00:43:14,527 --> 00:43:19,999
When another male tries to edge in,
they exchange a whole series of swift messages.

422
00:43:20,167 --> 00:43:22,601
That is the beginning of an argument.

423
00:43:48,847 --> 00:43:52,886
The reef squids' system of communication
is certainly complex

424
00:43:53,047 --> 00:43:55,038
and we don't fully understand it.

425
00:43:55,207 --> 00:43:58,438
But there are other animals
in these waters off the Bahamas

426
00:43:58,607 --> 00:44:02,885
that have a system that is
even more complicated still.

427
00:44:03,047 --> 00:44:05,481
They're mammals like ourselves,

428
00:44:05,647 --> 00:44:08,798
they seem positively to enjoy our company,

429
00:44:08,967 --> 00:44:12,880
and most ships have them
riding on their bow waves

430
00:44:13,047 --> 00:44:15,197
apparently just for the fun of it.

431
00:44:15,367 --> 00:44:17,562
They're dolphins.

432
00:44:23,847 --> 00:44:26,361
This crystal-clear patch of the ocean

433
00:44:26,527 --> 00:44:30,725
is the home of a group
of 60 or so spotted dolphins.

434
00:44:56,767 --> 00:45:00,203
Even though our ears are not well adapted
to hearing underwater,

435
00:45:00,367 --> 00:45:05,760
swimming with them I could catch something
of their near-continuous conversations.

436
00:45:05,927 --> 00:45:10,717
They're full of curiosity. They play
with odd things they find, such as twigs.

437
00:45:10,887 --> 00:45:15,597
Swimming among them leaves you
in no doubt that they are highly intelligent.

438
00:45:17,727 --> 00:45:20,685
(CLICKING)

439
00:45:28,207 --> 00:45:32,041
Like narwhals and other whales,
they use ultrasonic clicks.

440
00:45:34,087 --> 00:45:37,682
And they have a huge range of whistles.

441
00:45:37,847 --> 00:45:42,443
0ver 30 sounds have been identified,
each with a different meaning.

442
00:45:50,487 --> 00:45:54,639
Every dolphin has its own particular name whistle.

443
00:45:56,007 --> 00:46:00,080
0ne will attract the attention of another
by whistling this call sign

444
00:46:00,247 --> 00:46:03,637
just as we will shout to someone using his name.

445
00:46:09,207 --> 00:46:13,200
Baby dolphins have name whistles
that are derived from their mother's -

446
00:46:13,367 --> 00:46:17,121
inherited, in fact, rather like human surnames.

447
00:46:17,287 --> 00:46:21,724
This baby is accompanied
by a young female who is looking after it,

448
00:46:21,887 --> 00:46:26,677
but now its mother returns
and the baby whistles to her excitedly.

449
00:46:34,327 --> 00:46:37,239
When they are close to one another,
they may rub fins,

450
00:46:37,407 --> 00:46:40,319
just as we might shake hands.

451
00:46:41,407 --> 00:46:43,398
Most remarkable of all, perhaps,

452
00:46:43,567 --> 00:46:48,960
they combine both sound and visual
signals in their communications.

453
00:46:49,127 --> 00:46:51,482
They will often take up a particular position,

454
00:46:51,647 --> 00:46:55,526
hanging vertically in the water
or lying still on the bottom.

455
00:46:55,687 --> 00:46:59,316
Each posture gives each sound
a different meaning,

456
00:46:59,487 --> 00:47:02,285
so enormously increasing their vocabulary.

457
00:47:02,447 --> 00:47:06,645
They enjoy mimicking,
as though agreeing with one another.

458
00:47:06,807 --> 00:47:11,278
They will even mimic you,
as you spin or hang in the water.

459
00:47:27,967 --> 00:47:33,360
So these animals can communicate
in four different ways -

460
00:47:33,527 --> 00:47:35,961
with sounds which we can hear,

461
00:47:36,127 --> 00:47:38,800
with ultrasounds which we can't,

462
00:47:38,967 --> 00:47:45,236
with body postures which change
the meaning of any one sound, and with touch.

463
00:47:45,407 --> 00:47:49,400
The result is an amazingly complex
web of communication,

464
00:47:49,567 --> 00:47:53,162
unexcelled by any other animal except ourselves.

465
00:47:53,327 --> 00:47:57,923
But how marvellous it would be
if we could become a part of that.