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The natural
world is filled with sound.
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But, so far, we've been hearing
only part of it.
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Some animals call
even before they enter the world.
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00:00:40,320 --> 00:00:43,280
Others use sound to communicate
with their siblings.
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00:00:48,520 --> 00:00:49,720
Or call to their parents.
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00:00:51,600 --> 00:00:55,720
Using the most advanced
audio technology,
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00:00:55,720 --> 00:00:57,600
we can listen to them all...
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00:00:59,280 --> 00:01:02,360
...to reveal how baby animals
use sound to stay alive...
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00:01:04,360 --> 00:01:07,160
...in a world where the odds
are stacked against them.
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00:01:20,920 --> 00:01:23,240
The most perilous time
in an animal's life
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00:01:24,040 --> 00:01:25,960
is at its very beginning.
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00:01:32,200 --> 00:01:34,480
These little cygnets are just
three days old.
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00:01:41,680 --> 00:01:44,840
And at this stage of their lives,
and for some months to come,
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00:01:44,840 --> 00:01:47,040
they are unable to fly.
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00:01:48,520 --> 00:01:53,400
As a consequence, they are easy prey
for a gull or a fox.
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00:01:56,200 --> 00:02:00,800
But there's just one thing
that is of extreme importance
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00:02:00,800 --> 00:02:02,200
to their survival.
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00:02:02,200 --> 00:02:04,160
And that... is sound.
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00:02:17,280 --> 00:02:20,720
The Kalahari Desert
in southern Africa.
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00:02:24,800 --> 00:02:27,760
This is the home of a kind of
burrowing mongoose...
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Meerkats.
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00:02:34,560 --> 00:02:37,520
This season's pups are taking
their first steps in the world
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00:02:37,520 --> 00:02:39,920
outside their family's home.
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00:02:59,960 --> 00:03:03,400
In time, they will get to know
the sounds of everything
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00:03:04,480 --> 00:03:06,800
that's going on around them.
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00:03:10,240 --> 00:03:14,920
But just now, what they want
is breakfast.
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00:03:15,680 --> 00:03:17,960
And to get it,
they must make themselves heard.
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00:03:20,600 --> 00:03:23,760
The smallest pup has an injured foot
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00:03:23,760 --> 00:03:25,800
and keeping up with the rest is
a struggle.
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00:03:35,080 --> 00:03:38,160
Once they emerge, meerkat pups
need more food
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00:03:38,160 --> 00:03:40,840
than their own parents
can provide,
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00:03:40,840 --> 00:03:44,680
so they must persuade other adults
to feed them.
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00:03:51,600 --> 00:03:54,240
But in this harsh country,
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00:03:54,240 --> 00:03:56,960
food isn't easy to find.
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00:03:58,560 --> 00:04:02,120
Temperatures can reach over 45C,
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00:04:02,120 --> 00:04:04,520
and most food is hidden underground.
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00:04:07,400 --> 00:04:11,240
So a meerkat's life is dominated
by digging.
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00:04:12,640 --> 00:04:15,280
They may have to shift
their entire body weight in sand
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00:04:15,280 --> 00:04:18,800
to find just one mouthful to eat.
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00:04:21,400 --> 00:04:24,320
After all this hard work,
the helpers can be more interested
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00:04:24,320 --> 00:04:26,200
in feeding themselves than the pups.
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00:04:33,600 --> 00:04:37,000
So the youngsters beg continuously.
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00:04:44,800 --> 00:04:47,600
The moment food is found,
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00:04:47,600 --> 00:04:50,880
each pup switches to a high-pitched
begging call
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00:04:50,880 --> 00:04:54,280
in an attempt to ensure that it,
and not its siblings,
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00:04:54,280 --> 00:04:55,480
gets the mouthful.
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00:05:01,760 --> 00:05:04,600
And those who make this begging call
more intensely
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00:05:04,600 --> 00:05:06,880
get the food.
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00:05:07,800 --> 00:05:12,800
The biggest pup is successful,
and the smallest misses out again...
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00:05:14,240 --> 00:05:15,760
...and again.
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00:05:20,400 --> 00:05:24,080
Staying close to an adult
increases the chances of being heard
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00:05:24,080 --> 00:05:25,560
and being fed.
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00:05:27,800 --> 00:05:31,040
But this brings its own hazards.
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00:05:38,160 --> 00:05:40,480
Finally, the small one does get
a mouthful.
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00:05:44,320 --> 00:05:47,520
But he takes a long time
to eat it...
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00:05:51,840 --> 00:05:55,360
...and when he looks up,
everyone else has gone.
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00:06:01,520 --> 00:06:04,480
If there's one thing more important
to a meerkat than food,
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00:06:05,440 --> 00:06:06,960
it's family.
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00:06:08,680 --> 00:06:12,880
Without their guidance, he wouldn't
last for long in this intense heat.
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00:06:17,080 --> 00:06:18,640
He calls for help.
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00:06:25,040 --> 00:06:27,040
Making such a noise, however,
has risks.
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00:06:37,320 --> 00:06:39,080
At last an adult hears him.
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00:07:00,120 --> 00:07:04,200
But the heat and exhaustion
have taken their toll.
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00:07:05,080 --> 00:07:06,600
It may be too late.
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00:07:08,360 --> 00:07:11,680
His sister encourages him
to get back on his feet.
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00:07:28,680 --> 00:07:32,760
Once again, the little meerkat
has been saved... by sound.
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00:07:40,440 --> 00:07:45,240
As the pups grow, they will face
many new challenges...
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00:07:47,160 --> 00:07:49,840
...including predators.
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00:07:51,600 --> 00:07:54,880
Sound will be invaluable to help
them navigate these dangers.
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00:07:58,080 --> 00:08:02,400
But some baby animals use sound
before they even enter the world.
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00:08:06,360 --> 00:08:08,080
The swamps of South America.
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00:08:12,320 --> 00:08:13,800
There is danger everywhere.
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00:08:20,240 --> 00:08:23,560
One vigilant mother here is
on guard.
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00:08:25,560 --> 00:08:26,640
A caiman.
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00:08:28,960 --> 00:08:32,360
Over two metres long and weighing
around 60 kilograms,
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00:08:32,360 --> 00:08:36,840
she lives by ambushing prey
in these murky waters.
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00:08:39,200 --> 00:08:41,560
On the bank, close to the river,
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00:08:42,280 --> 00:08:43,480
there is a great mound.
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00:08:47,920 --> 00:08:50,240
It's her nest.
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00:08:55,200 --> 00:08:56,840
And inside, there are her eggs,
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00:08:58,960 --> 00:09:00,840
30 or so of them.
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00:09:05,720 --> 00:09:10,040
Her nest-guarding duties, however,
are coming to an end.
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00:09:13,800 --> 00:09:16,040
The young, still within the eggs,
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00:09:16,040 --> 00:09:18,760
are approaching one of the most
dangerous moments
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00:09:18,760 --> 00:09:20,560
they will ever face.
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00:09:20,560 --> 00:09:22,960
And they are squeaking.
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00:09:26,520 --> 00:09:30,040
Their chances of survival
will depend on these noises.
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00:09:32,040 --> 00:09:36,280
We have a special camera
with 60 super-sensitive microphones
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00:09:36,280 --> 00:09:39,960
which can show us which squeak
is coming from which egg.
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00:09:46,520 --> 00:09:47,920
The first starts to hatch.
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00:09:52,240 --> 00:09:56,000
But the youngsters would stand
a much better chance of survival
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00:09:56,000 --> 00:09:58,880
if they all hatched simultaneously.
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00:10:00,880 --> 00:10:02,080
So they call to one another
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00:10:02,080 --> 00:10:05,200
to indicate how close they are
to emerging.
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00:10:12,000 --> 00:10:14,400
It succeeds in struggling free
from the egg.
96
00:10:18,400 --> 00:10:20,120
But it has a problem.
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00:10:23,400 --> 00:10:26,120
The nest that once kept them
all safe...
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00:10:27,640 --> 00:10:29,200
...now keeps them trapped.
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00:10:35,160 --> 00:10:38,080
The calls of the emerged
now encourage the others
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00:10:38,080 --> 00:10:40,640
to break out of their eggs.
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00:10:44,600 --> 00:10:48,440
But they still can't get out of
the nest without help.
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00:10:51,880 --> 00:10:54,320
Individually,
they can barely be heard.
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00:10:57,320 --> 00:11:01,160
But together they become loud enough
for their mother to hear them.
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00:11:06,760 --> 00:11:10,640
She has been waiting for these
sounds for nearly 70 days.
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00:11:24,760 --> 00:11:26,120
And she goes into action.
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00:11:57,480 --> 00:12:00,120
One by one,
she picks her hatchlings up
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00:12:00,120 --> 00:12:02,360
and takes them down to the water.
108
00:12:19,440 --> 00:12:23,240
The last to hatch
are sometimes forgotten.
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00:12:24,800 --> 00:12:28,680
But with the nest fully opened,
they can now get out.
110
00:12:30,600 --> 00:12:33,440
But they have no idea
where their mother is.
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00:12:35,080 --> 00:12:38,360
Once again, they are saved by sound.
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00:12:42,000 --> 00:12:44,840
They can recognise the voices
of their siblings
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00:12:44,840 --> 00:12:46,840
and follow the sound to the water...
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00:12:46,840 --> 00:12:49,760
where their mother
will guard them all.
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00:12:53,880 --> 00:12:57,800
Sound has guided them on the first
and most hazardous journey
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00:12:57,800 --> 00:12:59,000
of their lives.
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00:13:25,520 --> 00:13:27,360
The sounds of an English spring.
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00:13:37,080 --> 00:13:39,160
For many of the animals
that live here,
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00:13:39,960 --> 00:13:42,080
they carry important messages.
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00:13:48,000 --> 00:13:52,080
This bee has discovered that the
flowers are now producing nectar.
121
00:13:55,560 --> 00:13:57,480
She gathers all she can...
122
00:13:59,920 --> 00:14:02,920
and then flies back
with the good news.
123
00:14:06,840 --> 00:14:09,920
Her colony has been inactive
during the colder months.
124
00:14:11,520 --> 00:14:15,280
But now the time has come
for action.
125
00:14:28,680 --> 00:14:31,040
The forager conveys her news
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00:14:31,040 --> 00:14:34,440
by repeatedly thumping her abdomen
on the comb.
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00:14:34,440 --> 00:14:41,440
Bees, like many insects,
don't have ears,
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00:14:43,320 --> 00:14:45,920
so they can't hear airborne sounds.
129
00:14:52,040 --> 00:14:56,200
But they can feel the vibrations
she makes on the comb...
130
00:14:59,560 --> 00:15:04,800
...detecting it with the sense organs
in their legs.
131
00:15:11,840 --> 00:15:14,440
And those that are still asleep
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00:15:14,440 --> 00:15:18,760
are alerted by her signal that drums
directly into their body.
133
00:15:27,520 --> 00:15:31,480
Eventually, the workers are roused
into action.
134
00:15:51,880 --> 00:15:55,240
Within days,
the hive's depleted stores
135
00:15:55,240 --> 00:15:58,400
are restocked with nectar
and pollen...
136
00:15:59,680 --> 00:16:03,960
...food that will fuel the production
of the next generation of bees.
137
00:16:11,520 --> 00:16:13,840
When a colony has grown so much
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00:16:13,840 --> 00:16:17,640
that it contains
around 40,000 individuals,
139
00:16:17,640 --> 00:16:19,880
it prepares to swarm.
140
00:16:20,920 --> 00:16:26,040
But a new swarm will need a queen,
and the old queen has already left.
141
00:16:28,040 --> 00:16:30,280
There are several contenders
for the role
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00:16:30,280 --> 00:16:33,680
who are developing in particularly
large cells.
143
00:16:35,800 --> 00:16:38,840
Tiny super-sensitive microphones
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00:16:38,840 --> 00:16:41,480
enable us to hear
an extraordinary call,
145
00:16:41,480 --> 00:16:42,800
like the quacking of a duck.
146
00:16:50,720 --> 00:16:53,400
The unhatched queens are signalling
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00:16:53,400 --> 00:16:55,480
that they're ready to emerge.
148
00:16:57,960 --> 00:17:01,200
The workers detect the vibrations
of these calls
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00:17:01,200 --> 00:17:05,960
and in response they start
to release the first queen.
150
00:17:11,200 --> 00:17:13,960
If two queens are released
at the same time,
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00:17:13,960 --> 00:17:16,920
they will fight one another
to the death.
152
00:17:18,160 --> 00:17:20,640
So, she does her best to make sure
153
00:17:20,640 --> 00:17:23,680
that her rivals remain
in their cells.
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00:17:26,560 --> 00:17:31,280
She does that by making a sound
beekeepers call a toot.
155
00:17:35,680 --> 00:17:37,640
Slowed down a thousand times
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00:17:37,640 --> 00:17:41,480
and using new software that converts
vibration to colour,
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00:17:41,480 --> 00:17:44,640
we can see
how she creates this call.
158
00:17:50,960 --> 00:17:53,280
The vibrations travel down her legs,
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00:17:53,280 --> 00:17:57,000
across the comb, and are detected
by the legs of the workers.
160
00:18:04,160 --> 00:18:08,320
As she toots, the whole colony,
for a few seconds,
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00:18:08,320 --> 00:18:12,920
stops moving...
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00:18:12,920 --> 00:18:16,760
...in recognition that a new queen
has ascended the throne.
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00:18:18,720 --> 00:18:22,520
Each toot
is answered by a chorus of quacks
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00:18:22,520 --> 00:18:25,600
from the rival queens
who are still within their cells
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00:18:25,600 --> 00:18:27,560
and eager to emerge.
166
00:18:28,680 --> 00:18:31,920
But as long as the new queen
continues tooting,
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00:18:31,920 --> 00:18:34,440
the workers will not release
her rivals.
168
00:18:37,120 --> 00:18:40,880
The crowned queen toots
repeatedly until, after a few days,
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00:18:40,880 --> 00:18:44,760
she prepares to depart with half
of the workers in a swarm.
170
00:18:47,800 --> 00:18:50,400
The sounds in the hive become
increasingly intense,
171
00:18:50,400 --> 00:18:54,040
until finally the swarm leaves
the nest.
172
00:19:05,680 --> 00:19:08,360
They re-assemble
on a nearby branch...
173
00:19:11,640 --> 00:19:14,920
...and a new colony
will soon be established.
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00:19:28,760 --> 00:19:30,360
Many animals,
when they first appear,
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00:19:30,360 --> 00:19:33,920
rely on their parents
for everything they need
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00:19:33,920 --> 00:19:36,240
and use sound to keep in touch
with them.
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00:19:42,680 --> 00:19:48,160
20,00 flamingos breeding
off the Yucatan coast in Mexico.
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00:19:51,080 --> 00:19:53,400
The noise here is deafening.
179
00:19:57,040 --> 00:20:01,240
The chicks, nonetheless, are able
to exchange intimate sounds
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00:20:01,240 --> 00:20:02,440
with their parents.
181
00:20:14,200 --> 00:20:16,720
This one has only just hatched.
182
00:20:19,560 --> 00:20:23,040
The colony provides protection
for its members.
183
00:20:23,040 --> 00:20:29,000
But living in such a huge crowd
is nonetheless hazardous.
184
00:20:29,000 --> 00:20:32,480
the chick's very survival depends on
its ability
185
00:20:32,480 --> 00:20:35,840
to recognise the voices
of its parents.
186
00:20:38,240 --> 00:20:41,360
So it must learn to do so quickly,
187
00:20:41,360 --> 00:20:42,920
because within ten days of hatching,
188
00:20:42,920 --> 00:20:45,720
it and its parents will leave
the nest.
189
00:20:48,320 --> 00:20:51,520
The call of each flamingo is unique.
190
00:20:53,040 --> 00:20:55,440
It's a kind of vocal fingerprint.
191
00:20:55,440 --> 00:20:58,200
How the chick manages in such a din
192
00:20:58,200 --> 00:21:03,280
to memorise and pick out the calls
of its parents is unimaginable.
193
00:21:03,280 --> 00:21:05,280
But it does so.
194
00:21:23,160 --> 00:21:27,080
This one is taking its first steps
out of the nest.
195
00:21:29,680 --> 00:21:33,200
But it's not really ready
for the wider world.
196
00:21:38,520 --> 00:21:40,960
Eventually it becomes
a little braver.
197
00:21:42,320 --> 00:21:44,760
but now it has a new problem.
198
00:21:45,920 --> 00:21:49,960
It's growing fast and both it
and its parents need food.
199
00:21:51,840 --> 00:21:56,000
To get it, the adults must leave
the colony and their chick.
200
00:21:57,840 --> 00:22:00,560
The chick cannot fly and will be
unable to do so
201
00:22:00,560 --> 00:22:02,160
for another three months.
202
00:22:02,160 --> 00:22:05,720
So, until then,
it's very vulnerable.
203
00:22:07,840 --> 00:22:12,480
There are hundreds of youngsters
with the same problem.
204
00:22:12,480 --> 00:22:16,880
The young gather together
in an enormous creche.
205
00:22:18,240 --> 00:22:20,040
There's safety in numbers.
206
00:22:24,440 --> 00:22:28,080
A few adults have stayed behind
to keep the creche together.
207
00:22:31,600 --> 00:22:34,040
The others eventually return.
208
00:22:35,600 --> 00:22:39,120
But now each must recognise
its own chick
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00:22:39,120 --> 00:22:41,880
among the densely packed flock
of thousands.
210
00:22:50,840 --> 00:22:53,800
Amazingly, each family trio —
male, female and chick —
211
00:22:55,640 --> 00:22:58,240
are able to recognise
one another's voices.
212
00:23:03,760 --> 00:23:07,080
Distinguishing individual calls
among this deafening chorus
213
00:23:07,080 --> 00:23:08,280
must be difficult.
214
00:23:10,080 --> 00:23:12,720
And this male can't find his chick.
215
00:23:15,480 --> 00:23:18,840
Adults aren't the only ones
who are searching.
216
00:23:22,520 --> 00:23:25,080
A crocodile is lurking nearby.
217
00:23:29,120 --> 00:23:30,840
The chick calls...
218
00:23:32,240 --> 00:23:34,800
But it can't hear
its father's reply.
219
00:23:39,720 --> 00:23:42,160
The crocodile attacks.
220
00:24:08,800 --> 00:24:10,680
It's failed to grab a chick,
221
00:24:10,680 --> 00:24:14,880
but it did create dangerous
confusion in the flock.
222
00:24:17,240 --> 00:24:19,480
The chick has become separated
from the others
223
00:24:19,480 --> 00:24:21,680
and seems to be lost.
224
00:24:27,440 --> 00:24:30,560
It begs for food from any individual
that passes.
225
00:24:36,760 --> 00:24:40,200
Its father, in another part of
the flock, keeps calling.
226
00:24:43,440 --> 00:24:46,360
But the chick is too far away
to hear him.
227
00:24:50,760 --> 00:24:54,240
And this is how many chicks
meet their end.
228
00:24:58,520 --> 00:25:00,280
But not this one.
229
00:25:07,400 --> 00:25:09,400
It keeps calling.
230
00:25:11,960 --> 00:25:14,440
And from across the lagoon...
231
00:25:14,440 --> 00:25:15,560
...its father replies.
232
00:25:20,960 --> 00:25:23,720
The unique sound of the chick's
voice has been recognised
233
00:25:23,720 --> 00:25:28,200
by its father, and the two at last
are re-united.
234
00:25:36,480 --> 00:25:38,480
As young animals grow,
235
00:25:38,480 --> 00:25:42,600
they learn to recognise oncoming
dangers and become big enough
236
00:25:42,600 --> 00:25:45,360
for their voices to sound an alarm.
237
00:25:59,880 --> 00:26:01,600
A wolf pack, in Ontario, Canada.
238
00:26:09,320 --> 00:26:12,760
This communal howl binds the pack
together
239
00:26:12,760 --> 00:26:15,480
and registers their ownership
of a territory.
240
00:26:22,080 --> 00:26:25,720
With only around 500
of these Eastern wolves left,
241
00:26:25,720 --> 00:26:29,240
this heart-stopping sound is now
extremely rare.
242
00:26:32,000 --> 00:26:35,400
But this chorus has some new voices.
243
00:26:38,040 --> 00:26:41,360
It's August and the pups
are joining in.
244
00:26:43,440 --> 00:26:46,080
These youngsters, however,
create a problem...
245
00:26:46,920 --> 00:26:49,240
...one that could endanger them all.
246
00:27:02,480 --> 00:27:05,200
Now, in summer,
the days are over 14 hours long.
247
00:27:08,520 --> 00:27:11,400
So the wolves have to hunt
in the light.
248
00:27:18,080 --> 00:27:21,080
The pups are too big
to stay in the den,
249
00:27:21,080 --> 00:27:25,480
but too inexperienced to join in
the hunt.
250
00:27:25,480 --> 00:27:31,280
So the adults leave them
in an open area - a rendezvous site.
251
00:27:32,080 --> 00:27:36,760
Its very openness makes
it a great place for play.
252
00:27:36,760 --> 00:27:40,320
But this is a particularly dangerous
time in their lives.
253
00:27:41,240 --> 00:27:44,720
Half of them won't live beyond
their first year.
254
00:27:46,120 --> 00:27:50,400
What happens here and now will
determine whether these will do so.
255
00:27:58,040 --> 00:28:02,120
Two of the youngsters know exactly
where they are supposed to stay.
256
00:28:02,120 --> 00:28:05,640
But their sister can't resist
exploring.
257
00:28:25,720 --> 00:28:29,880
Distracted, she doesn't notice that
a black bear is approaching.
258
00:28:33,280 --> 00:28:37,720
This is one of the few animals
that will kill a wolf pup.
259
00:28:39,880 --> 00:28:43,240
The wandering youngster seems
unaware of the danger.
260
00:28:45,640 --> 00:28:47,360
But her brothers are.
261
00:28:53,080 --> 00:28:54,960
They sound the alarm.
262
00:28:57,520 --> 00:29:01,440
Alerted, the wandering pup spots
the bear.
263
00:29:18,840 --> 00:29:22,640
Now the lives of all three pups
are at risk.
264
00:29:25,240 --> 00:29:28,760
But, as the bear moves in,
she hears a different call.
265
00:29:32,120 --> 00:29:33,560
It's her own cub.
266
00:29:33,560 --> 00:29:35,240
And he needs his mother.
267
00:29:42,560 --> 00:29:44,960
It's been a lucky escape
for the pups...
268
00:29:46,800 --> 00:29:49,160
...but they are not yet
in the clear.
269
00:29:51,360 --> 00:29:53,160
The pups' howls are shorter
and higher-pitched
270
00:29:53,160 --> 00:29:55,280
than those of the adults...
271
00:29:57,520 --> 00:30:00,600
...but they can still be heard
many miles away.
272
00:30:03,120 --> 00:30:06,840
And they are answered.
273
00:30:14,240 --> 00:30:17,080
The sound has alerted an adult wolf.
274
00:30:28,760 --> 00:30:29,800
It's their father.
275
00:30:32,360 --> 00:30:34,400
He's returned with food
for the pups.
276
00:30:40,200 --> 00:30:45,520
As dusk falls, the pack celebrates
with a reunion chorus.
277
00:30:49,400 --> 00:30:52,960
Their voices have been crucial
in keeping the pack together.
278
00:30:55,560 --> 00:30:58,240
But many animals issue
warning calls
279
00:30:58,240 --> 00:31:01,160
that contain
far more complex information.
280
00:31:05,760 --> 00:31:09,520
The meerkats, as they grow,
learn how to find their own meals.
281
00:31:12,160 --> 00:31:15,120
And they are discovering how
to avoid becoming someone else's.
282
00:31:17,400 --> 00:31:20,400
The desert is full of
hungry mouths...
283
00:31:21,840 --> 00:31:25,600
...and meerkats are small
and obviously edible.
284
00:31:28,680 --> 00:31:31,480
Their defence is neither armour
nor weapon.
285
00:31:33,840 --> 00:31:36,360
Instead, they use sound -
286
00:31:36,360 --> 00:31:38,200
a complicated system of alarms.
287
00:31:41,600 --> 00:31:44,680
These calls are not just
generalised alerts.
288
00:31:50,120 --> 00:31:52,320
This one warns of
a flying predator...
289
00:31:55,280 --> 00:31:58,040
...and those hearing it look up
and scan the sky.
290
00:32:06,760 --> 00:32:10,480
Danger on the ground is indicated
by a different call.
291
00:32:14,000 --> 00:32:15,360
Best to look around.
292
00:32:21,640 --> 00:32:25,960
Snakes are identified by
a third signal.
293
00:32:31,880 --> 00:32:34,240
A call from the look-out
summons others
294
00:32:34,240 --> 00:32:36,320
to come and help drive it away.
295
00:32:45,120 --> 00:32:47,560
Meerkat warnings are so detailed
296
00:32:47,560 --> 00:32:50,040
that they can be a bit confusing
for youngsters.
297
00:32:54,080 --> 00:32:57,320
So the best thing is to do
what everybody else is doing.
298
00:33:01,920 --> 00:33:04,360
The calls also carry
other information,
299
00:33:04,360 --> 00:33:07,680
such as how fast a predator
is approaching.
300
00:33:09,160 --> 00:33:12,480
And there is one call
which should never be ignored.
301
00:33:14,040 --> 00:33:19,520
This is the high-urgency call,
a warning of immediate danger.
302
00:33:23,400 --> 00:33:26,120
Not to react to this
could be disastrous.
303
00:33:29,640 --> 00:33:33,600
So when you hear this call...
304
00:33:33,600 --> 00:33:35,160
...run for your life!
305
00:33:49,520 --> 00:33:53,120
Sounds in the open air are important
for many animals.
306
00:33:54,880 --> 00:33:58,720
But there is another world of sound
with which we are far less familiar.
307
00:33:59,880 --> 00:34:03,040
We can't hear very well underwater,
308
00:34:03,040 --> 00:34:06,720
because our ears are shaped
to work in the air.
309
00:34:07,480 --> 00:34:11,480
But there is a way in which we can
eavesdrop on this underwater world,
310
00:34:11,480 --> 00:34:14,880
by using a special kind of
underwater microphone
311
00:34:14,880 --> 00:34:17,440
called a hydrophone.
312
00:34:24,760 --> 00:34:28,160
I don't know exactly what's making
those noises,
313
00:34:28,160 --> 00:34:32,480
it's probably some small
invertebrates or maybe a small fish.
314
00:34:32,480 --> 00:34:36,440
We've known for some time that
quite a lot of fish produce sounds.
315
00:34:37,440 --> 00:34:40,480
It's only recently, however,
that scientists have discovered
316
00:34:40,480 --> 00:34:43,640
just how widespread that ability is.
317
00:34:54,440 --> 00:34:59,880
The ocean covers around 70% of
our planet's surface.
318
00:35:06,160 --> 00:35:08,280
And sound also plays a crucial role
319
00:35:08,280 --> 00:35:12,280
in the lives of many of the animals
that live in it.
320
00:35:17,800 --> 00:35:20,200
Coral reefs are surprisingly
noisy places.
321
00:35:23,960 --> 00:35:25,960
Many of these sounds are made
by fish.
322
00:35:40,400 --> 00:35:42,920
Here too, sound can be important
323
00:35:42,920 --> 00:35:45,680
from the very beginning of
an animal's life.
324
00:35:47,320 --> 00:35:51,840
Without it, one of the most
strikingly coloured fish on the reef
325
00:35:51,840 --> 00:35:54,200
would never find its way home.
326
00:35:58,440 --> 00:36:00,840
It's just days before a full moon
327
00:36:00,840 --> 00:36:04,560
and this female clownfish is about
to lay her eggs.
328
00:36:10,200 --> 00:36:12,280
Clownfish live in small communities,
329
00:36:13,520 --> 00:36:18,280
each based around a particularly
large anemone.
330
00:36:23,760 --> 00:36:28,480
In this busy colony,
only two adults will reproduce -
331
00:36:28,480 --> 00:36:31,200
the largest, the dominant female...
332
00:36:32,120 --> 00:36:35,680
...and her partner, the next in size,
the dominant male.
333
00:36:37,560 --> 00:36:40,800
There's a strict hierarchy,
one that's based on size,
334
00:36:40,800 --> 00:36:43,280
but policed by sound.
335
00:36:46,120 --> 00:36:50,280
Her larger body enables her
to make the deepest sound
336
00:36:50,280 --> 00:36:54,560
by snapping her teeth together
to produce pops and pulses.
337
00:37:07,160 --> 00:37:10,000
The male signals
his subordinate status
338
00:37:10,000 --> 00:37:12,120
by quivering his head
339
00:37:12,120 --> 00:37:14,360
and producing a purring noise.
340
00:37:16,800 --> 00:37:20,840
And everyone around the anemone
knows that she is the boss.
341
00:37:25,840 --> 00:37:28,960
At full moon, she will be ready
to lay eggs.
342
00:37:31,440 --> 00:37:34,480
So the group needs to find
a firm surface for them.
343
00:37:36,680 --> 00:37:39,000
A coconut shell, brought in
by the currents,
344
00:37:39,000 --> 00:37:41,080
would be ideal.
345
00:37:43,480 --> 00:37:45,760
But it needs to be moved
into the right position.
346
00:37:47,800 --> 00:37:50,560
She indicates her needs
with a low-pitched grunt,
347
00:37:50,560 --> 00:37:55,320
and the juveniles in the colony
comply by shaking their heads.
348
00:38:04,960 --> 00:38:09,320
Working together, they manoeuvre
the coconut shell into position.
349
00:38:12,040 --> 00:38:15,360
Team work takes a lot of
co-ordination,
350
00:38:15,360 --> 00:38:18,200
and a lot of grunting
and jaw-grinding.
351
00:38:25,960 --> 00:38:30,120
Next, the stage needs
to be prepared.
352
00:38:36,360 --> 00:38:38,080
And at last, the moment arrives.
353
00:38:44,680 --> 00:38:48,040
She lays her eggs in neat lines.
354
00:39:02,920 --> 00:39:07,400
The male then makes HIS contribution
- fertilising the eggs.
355
00:39:14,440 --> 00:39:16,000
Now he takes charge.
356
00:39:20,240 --> 00:39:24,080
For the next seven days, he will fan
and clean the eggs as they develop.
357
00:39:34,160 --> 00:39:37,480
Three more days and the embryos
begin to respond
358
00:39:37,480 --> 00:39:39,800
to the sounds around them.
359
00:39:41,760 --> 00:39:45,960
The sounds that they hear now
could play a critical role
360
00:39:45,960 --> 00:39:48,400
in the next stage of their lives.
361
00:39:53,680 --> 00:39:58,200
But a different sort of noise is
already threatening their survival.
362
00:40:04,480 --> 00:40:07,840
The male reacts to the noise of
a boat as he would to a predator.
363
00:40:12,880 --> 00:40:14,800
If there is constant motor traffic,
364
00:40:14,800 --> 00:40:18,840
he spends more time hiding
and less tending the eggs...
365
00:40:18,840 --> 00:40:21,320
so they are more vulnerable
to predators and disease.
366
00:40:25,920 --> 00:40:29,280
The noise around these reefs
has increased dramatically
367
00:40:29,280 --> 00:40:33,840
in recent decades, and that has
affected the lives of the fish here.
368
00:40:36,560 --> 00:40:40,240
But the clownfish father has managed
to keep his young healthy,
369
00:40:40,240 --> 00:40:43,160
and a week later,
they begin to change.
370
00:40:46,280 --> 00:40:49,240
The plankton-sized fry wriggle free
371
00:40:49,240 --> 00:40:53,040
and are then swept away from
the reef by ocean currents.
372
00:41:03,760 --> 00:41:08,680
For ten days, the larval fish drift
out in the open ocean.
373
00:41:20,200 --> 00:41:24,120
By the time that each is about
the size of a grain of rice,
374
00:41:24,120 --> 00:41:27,760
they are strong enough to swim
against the current.
375
00:41:28,960 --> 00:41:32,240
And they need to find their way
back to a reef.
376
00:41:40,200 --> 00:41:43,560
The key to their homecoming
is sound.
377
00:41:45,720 --> 00:41:50,640
Underwater, the sounds of a reef
can be heard for many miles around.
378
00:41:50,640 --> 00:41:55,280
The tiny young clownfish can hear
this noise and swim towards it.
379
00:41:58,720 --> 00:42:02,080
They can even judge the health of
a reef by its sound.
380
00:42:02,080 --> 00:42:05,480
The noisier it is,
the more vigorous it is.
381
00:42:26,160 --> 00:42:29,880
The anemone will provide him with
shelter and sanctuary
382
00:42:29,880 --> 00:42:33,640
for the rest of his life.
383
00:42:33,640 --> 00:42:36,320
Sound has brought him home.
384
00:42:40,920 --> 00:42:44,440
For these fish, and for many other
baby animals,
385
00:42:44,440 --> 00:42:48,920
sound is crucial for launching
themselves into the world
386
00:42:48,920 --> 00:42:53,480
and learning what they need to stay
safe and to thrive.
387
00:42:54,560 --> 00:42:58,040
For them, sound is survival.
388
00:43:22,640 --> 00:43:24,720
What's one of the close ones
over here...
389
00:43:24,720 --> 00:43:28,520
Biologist Mark Meekan
became fascinated by coral reefs
390
00:43:28,520 --> 00:43:29,840
more than 30 years ago.
391
00:43:31,040 --> 00:43:33,520
'Coral reefs are these incredible
habitats
392
00:43:33,520 --> 00:43:37,360
and I've always been struck by
their diversity
393
00:43:37,360 --> 00:43:39,720
and just incredible beauty.'
394
00:43:39,720 --> 00:43:43,480
Today he is fighting to save
these reefs
395
00:43:43,480 --> 00:43:46,120
from the ravages of climate change.
396
00:43:46,120 --> 00:43:49,800
This is Australia's Ningaloo Reef
397
00:43:49,800 --> 00:43:52,520
that stretches along the country's
western coast.
398
00:43:54,480 --> 00:43:55,760
But over decades of research,
399
00:43:55,760 --> 00:43:58,440
Mark discovered something else —
400
00:43:58,440 --> 00:44:01,720
that coral reefs are full of sound.
401
00:44:04,160 --> 00:44:06,480
A hunch about the significance
of this inspired him
402
00:44:06,480 --> 00:44:11,400
to try and find a way to use
this sound to save coral reefs.
403
00:44:13,000 --> 00:44:14,840
'If we could hear underwater,
404
00:44:14,840 --> 00:44:18,640
we would hear this cacophony of
hoots and yowls,
405
00:44:18,640 --> 00:44:21,440
really strange screams made by fish.
406
00:44:22,600 --> 00:44:26,120
And these little fish may actually
be helping the coral to grow.
407
00:44:26,120 --> 00:44:31,720
Basically, by sheltering in
the coral, pooping in the coral,
408
00:44:31,720 --> 00:44:33,120
fertilising the coral.
409
00:44:35,040 --> 00:44:38,760
A healthy reef is really
very noisy.'
410
00:44:38,760 --> 00:44:41,080
This sound is key.
411
00:44:41,080 --> 00:44:44,960
After hatching, reef fish are swept
out to sea.
412
00:44:44,960 --> 00:44:48,960
When they return,
they use these healthy sounds
413
00:44:48,960 --> 00:44:51,680
to choose the reef
that will be their home.
414
00:44:51,680 --> 00:44:54,040
And this was just a wow moment.
415
00:44:54,040 --> 00:44:57,920
We suddenly thought, "We can
actually use this to help the reef."
416
00:45:00,480 --> 00:45:05,280
The result is a multi-million-dollar
project with one goal —
417
00:45:05,280 --> 00:45:10,320
to discover if sound can also help
save a dying reef.
418
00:45:16,000 --> 00:45:20,520
The first step is to collect three
and a half tons of coral debris.
419
00:45:22,440 --> 00:45:24,840
It's alive and extremely vulnerable.
420
00:45:28,920 --> 00:45:31,320
Mark's team build
60 experimental reefs.
421
00:45:34,280 --> 00:45:38,440
Underwater speakers are guided
to some of these and turned on.
422
00:45:41,120 --> 00:45:43,400
It's their job to attract fish
423
00:45:43,400 --> 00:45:46,160
by playing the sounds of
a healthy reef.
424
00:45:47,320 --> 00:45:51,280
The results will be compared
to experimental reefs
425
00:45:51,280 --> 00:45:53,240
without speakers.
426
00:45:57,880 --> 00:46:00,960
At Ningaloo, it's a new moon.
427
00:46:03,760 --> 00:46:06,440
Tonight,
the reef fish are coming home.
428
00:46:09,880 --> 00:46:13,400
At the experimental sites,
speakers are on,
429
00:46:13,400 --> 00:46:17,120
broadcasting the sounds of
a healthy reef.
430
00:46:19,280 --> 00:46:20,960
OK, get ready, Daphne.
431
00:46:20,960 --> 00:46:23,440
They are laying out light traps
432
00:46:23,440 --> 00:46:26,680
and assessing if the speakers are
attracting fish
433
00:46:26,680 --> 00:46:30,280
to the experimental reefs with sound
434
00:46:30,280 --> 00:46:32,400
versus ones without.
435
00:46:33,360 --> 00:46:34,680
And they are!
436
00:46:34,680 --> 00:46:36,800
'We actually got the fish to come.
437
00:46:38,280 --> 00:46:41,480
They arrived in big numbers
on the reefs.'
438
00:46:45,440 --> 00:46:50,360
Mark's team have been photographing
these reefs for 12 months.
439
00:46:54,800 --> 00:46:57,760
Now they're going to see if the fish
have helped the coral to grow again.
440
00:47:01,240 --> 00:47:05,560
So, on the left here, we've got our
patch reef model from one year ago.
441
00:47:05,560 --> 00:47:09,360
And on the right-hand side, our reef
model from a couple of days ago.
442
00:47:09,360 --> 00:47:13,400
You can see fairly obviously
already
443
00:47:13,400 --> 00:47:16,200
there's been a fair bit of growth
over the year.
444
00:47:18,520 --> 00:47:22,240
Wow!
This one's roughly 20cm across,
445
00:47:22,240 --> 00:47:23,640
maximum diameter,
446
00:47:23,640 --> 00:47:26,000
and the same colony a year later,
it's almost 40.
447
00:47:26,000 --> 00:47:30,040
So we've doubled in size.
Fantastic, man.
448
00:47:32,680 --> 00:47:34,400
Wow.
449
00:47:37,800 --> 00:47:40,000
oral reefs today are in such a state
450
00:47:40,000 --> 00:47:43,640
that we're beyond shouting
to everybody that it's bad.
451
00:47:43,640 --> 00:47:47,240
We have to move into doing something
about it.
452
00:47:50,520 --> 00:47:54,560
The sound made by fish might just be
a vital tool
453
00:47:54,560 --> 00:47:58,640
to help scientists save coral reefs
around the globe.
454
00:48:33,600 --> 00:48:36,040
AccessibleCustomerService@sky.uk
35616
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