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These are the user uploaded subtitles that are being translated: 1 00:00:10,000 --> 00:00:12,520 (HOOTING AND PIPING) 2 00:00:12,560 --> 00:00:13,640 (HONKING) 3 00:00:13,680 --> 00:00:16,760 DAVID ATTENBOROUGH: The natural world is filled with sound. 4 00:00:16,800 --> 00:00:19,440 (CLICKING, THUNDER CRASHING) 5 00:00:19,480 --> 00:00:21,360 (CLUCKING) 6 00:00:21,400 --> 00:00:23,040 (BRAYING) 7 00:00:23,080 --> 00:00:24,200 (GROWLING) 8 00:00:25,120 --> 00:00:28,880 But, so far, we've been hearing only part of it. 9 00:00:31,120 --> 00:00:34,360 Some animals call even before they enter the world. 10 00:00:34,400 --> 00:00:36,880 (SQUEAKING, SOFT HONKING) 11 00:00:36,920 --> 00:00:37,960 (RATTLING SOUND) 12 00:00:40,320 --> 00:00:43,280 Others use sound to communicate with their siblings. 13 00:00:43,320 --> 00:00:45,000 (CHATTERING) 14 00:00:48,520 --> 00:00:49,720 Or call to their parents. 15 00:00:49,760 --> 00:00:51,600 (GROUP SQUAWKING) 16 00:00:51,640 --> 00:00:55,720 Using the most advanced audio technology, 17 00:00:55,760 --> 00:00:57,600 we can listen to them all... (DRAWN-OUT WHINE) 18 00:00:59,280 --> 00:01:02,360 ..to reveal how baby animals use sound to stay alive... 19 00:01:02,400 --> 00:01:03,400 (WHINES) 20 00:01:04,360 --> 00:01:07,160 ..in a world where the odds are stacked against them. 21 00:01:07,200 --> 00:01:08,960 (HOWLING) 22 00:01:16,080 --> 00:01:18,360 (ANIMATED BIRDSONG) 23 00:01:20,920 --> 00:01:23,240 The most perilous time in an animal's life 24 00:01:24,039 --> 00:01:25,960 is at its very beginning. 25 00:01:29,360 --> 00:01:30,480 (CHUCKLES) 26 00:01:32,200 --> 00:01:34,479 These little cygnets are just three days old. 27 00:01:41,680 --> 00:01:44,840 And at this stage of their lives, and for some months to come, 28 00:01:44,880 --> 00:01:47,039 they are unable to fly. 29 00:01:48,520 --> 00:01:53,400 As a consequence, they are easy prey for a gull or a fox. 30 00:01:56,200 --> 00:02:00,800 But there's just one thing that is of extreme importance 31 00:02:00,840 --> 00:02:02,200 to their survival. 32 00:02:02,240 --> 00:02:04,160 And that...is sound. 33 00:02:04,200 --> 00:02:06,280 (CHIRPING) 34 00:02:17,280 --> 00:02:20,720 The Kalahari Desert in southern Africa. 35 00:02:22,160 --> 00:02:24,800 (CHIRRUPING) 36 00:02:24,840 --> 00:02:27,760 This is the home of a kind of burrowing mongoose... 37 00:02:29,600 --> 00:02:30,920 Meerkats. 38 00:02:30,960 --> 00:02:33,000 (HIGH-PITCHED CHIRPING AND GRUNTING) 39 00:02:34,560 --> 00:02:37,520 This season's pups are taking their first steps in the world 40 00:02:37,560 --> 00:02:39,920 outside their family's home. 41 00:02:45,040 --> 00:02:46,200 (CHATTERS) 42 00:02:49,000 --> 00:02:50,920 (SHORT SCREECHES) 43 00:02:55,040 --> 00:02:57,200 (SQUAWKS) 44 00:02:59,960 --> 00:03:03,400 In time, they will get to know the sounds of everything 45 00:03:04,480 --> 00:03:06,800 that's going on around them. 46 00:03:07,800 --> 00:03:09,160 (FLIES BUZZING) 47 00:03:09,200 --> 00:03:10,240 (SNORTS) 48 00:03:10,280 --> 00:03:14,920 But just now, what they want is breakfast. 49 00:03:15,680 --> 00:03:17,960 And to get it, they must make themselves heard. 50 00:03:18,000 --> 00:03:19,480 (SQUEAKS) 51 00:03:20,600 --> 00:03:23,760 The smallest pup has an injured foot 52 00:03:23,800 --> 00:03:25,800 and keeping up with the rest is a struggle. 53 00:03:30,280 --> 00:03:31,680 (HIGH-PITCHED GRUNTS) 54 00:03:35,079 --> 00:03:38,160 Once they emerge, meerkat pups need more food 55 00:03:38,200 --> 00:03:40,840 than their own parents can provide, 56 00:03:40,880 --> 00:03:44,680 so they must persuade other adults to feed them. 57 00:03:44,720 --> 00:03:46,360 (PURRS) 58 00:03:51,600 --> 00:03:54,240 But in this harsh country, 59 00:03:54,280 --> 00:03:56,960 food isn't easy to find. 60 00:03:58,560 --> 00:04:02,120 Temperatures can reach over 45C, 61 00:04:02,160 --> 00:04:04,520 and most food is hidden underground. 62 00:04:07,400 --> 00:04:11,240 So a meerkat's life is dominated by digging. 63 00:04:12,640 --> 00:04:15,280 They may have to shift their entire body weight in sand 64 00:04:15,320 --> 00:04:18,800 to find just one mouthful to eat. 65 00:04:21,399 --> 00:04:24,320 After all this hard work, the helpers can be more interested 66 00:04:24,360 --> 00:04:26,200 in feeding themselves than the pups. 67 00:04:26,240 --> 00:04:28,920 (RAPID PURRING) 68 00:04:33,600 --> 00:04:37,000 So the youngsters beg continuously. 69 00:04:37,040 --> 00:04:39,760 (SQUEAKING AND PURRING) 70 00:04:44,800 --> 00:04:47,600 The moment food is found, 71 00:04:47,640 --> 00:04:50,880 each pup switches to a high-pitched begging call 72 00:04:50,920 --> 00:04:54,280 in an attempt to ensure that it, and not its siblings, 73 00:04:54,320 --> 00:04:55,480 gets the mouthful. 74 00:04:55,520 --> 00:04:56,800 (ALL CHATTERING AND SQUEAKING) 75 00:05:01,760 --> 00:05:04,600 And those who make this begging call more intensely 76 00:05:04,640 --> 00:05:06,880 get the food. 77 00:05:07,800 --> 00:05:12,800 The biggest pup is successful, and the smallest misses out again... 78 00:05:14,240 --> 00:05:15,760 ..and again. 79 00:05:20,400 --> 00:05:24,080 Staying close to an adult increases the chances of being heard 80 00:05:24,120 --> 00:05:25,560 and being fed. 81 00:05:27,800 --> 00:05:31,040 But this brings its own hazards. 82 00:05:33,200 --> 00:05:36,640 (PUP SQUEAKS) 83 00:05:38,159 --> 00:05:40,480 Finally, the small one does get a mouthful. 84 00:05:44,320 --> 00:05:47,520 But he takes a long time to eat it... 85 00:05:51,840 --> 00:05:55,360 ..and when he looks up, everyone else has gone. 86 00:05:55,400 --> 00:05:56,800 (SOFT SQUEAK) 87 00:06:01,520 --> 00:06:04,480 If there's one thing more important to a meerkat than food, 88 00:06:05,440 --> 00:06:06,960 it's family. 89 00:06:08,680 --> 00:06:12,880 Without their guidance, he wouldn't last for long in this intense heat. 90 00:06:15,960 --> 00:06:17,080 (CHIRPS) 91 00:06:17,120 --> 00:06:18,640 He calls for help. 92 00:06:18,680 --> 00:06:20,920 (CHIRPS) 93 00:06:23,720 --> 00:06:25,040 (LONG CHIRP) 94 00:06:25,080 --> 00:06:27,040 Making such a noise, however, has risks. 95 00:06:27,080 --> 00:06:28,200 (CHIRPS) 96 00:06:34,200 --> 00:06:35,800 (DISTANT CHIRP) 97 00:06:37,320 --> 00:06:39,080 At last an adult hears him. 98 00:06:39,960 --> 00:06:41,159 (SQUEAKING) 99 00:07:00,120 --> 00:07:04,200 But the heat and exhaustion have taken their toll. 100 00:07:05,080 --> 00:07:06,600 It may be too late. 101 00:07:08,360 --> 00:07:11,680 His sister encourages him to get back on his feet. 102 00:07:11,720 --> 00:07:14,320 (CHEEPING) 103 00:07:28,680 --> 00:07:32,760 Once again, the little meerkat has been saved...by sound. 104 00:07:35,560 --> 00:07:38,920 (URGENT BARKING) 105 00:07:40,440 --> 00:07:45,240 As the pups grow, they will face many new challenges... 106 00:07:47,159 --> 00:07:49,840 ..including predators. 107 00:07:51,600 --> 00:07:54,880 Sound will be invaluable to help them navigate these dangers. 108 00:07:54,920 --> 00:07:56,920 (CROAKING) 109 00:07:58,080 --> 00:08:02,400 But some baby animals use sound before they even enter the world. 110 00:08:03,280 --> 00:08:04,880 (BIRDS HOOT AND PIPE) 111 00:08:06,360 --> 00:08:08,080 The swamps of South America. 112 00:08:12,320 --> 00:08:13,800 There is danger everywhere. 113 00:08:13,840 --> 00:08:16,480 (SNORTING) 114 00:08:20,240 --> 00:08:23,560 One vigilant mother here is on guard. 115 00:08:25,560 --> 00:08:26,640 A caiman. 116 00:08:28,960 --> 00:08:32,360 Over two metres long and weighing around 60 kilograms, 117 00:08:32,400 --> 00:08:36,840 she lives by ambushing prey in these murky waters. 118 00:08:39,200 --> 00:08:41,559 On the bank, close to the river, 119 00:08:42,280 --> 00:08:43,480 there is a great mound. 120 00:08:47,920 --> 00:08:50,240 It's her nest. 121 00:08:55,200 --> 00:08:56,840 And inside, there are her eggs, 122 00:08:58,960 --> 00:09:00,840 30 or so of them. 123 00:09:05,720 --> 00:09:10,040 Her nest-guarding duties, however, are coming to an end. 124 00:09:13,800 --> 00:09:16,040 The young, still within the eggs, 125 00:09:16,080 --> 00:09:18,760 are approaching one of the most dangerous moments 126 00:09:18,800 --> 00:09:20,560 they will ever face. 127 00:09:20,600 --> 00:09:22,960 And they are squeaking. 128 00:09:24,200 --> 00:09:26,520 (PULSING SQUEAKS) 129 00:09:26,560 --> 00:09:30,040 Their chances of survival will depend on these noises. 130 00:09:32,040 --> 00:09:36,280 We have a special camera with 60 super-sensitive microphones 131 00:09:36,320 --> 00:09:39,960 which can show us which squeak is coming from which egg. 132 00:09:40,000 --> 00:09:41,760 (SQUEAKING) 133 00:09:41,800 --> 00:09:44,480 (SQUEAKING) 134 00:09:46,520 --> 00:09:47,920 The first starts to hatch. 135 00:09:50,080 --> 00:09:52,240 (SQUEAKING) 136 00:09:52,280 --> 00:09:56,000 But the youngsters would stand a much better chance of survival 137 00:09:56,040 --> 00:09:58,880 if they all hatched simultaneously. 138 00:09:58,920 --> 00:10:00,080 (VARIOUS TONES OF SQUEAKING) 139 00:10:00,880 --> 00:10:02,080 So they call to one another 140 00:10:02,120 --> 00:10:05,200 to indicate how close they are to emerging. 141 00:10:06,640 --> 00:10:09,400 (SHORT GRUNTS AND SQUEAKS) 142 00:10:12,000 --> 00:10:14,400 It succeeds in struggling free from the egg. 143 00:10:18,400 --> 00:10:20,120 But it has a problem. 144 00:10:20,160 --> 00:10:21,720 (BIRDS CHIRPING) 145 00:10:23,400 --> 00:10:26,120 The nest that once kept them all safe... 146 00:10:27,640 --> 00:10:29,200 ..now keeps them trapped. 147 00:10:29,240 --> 00:10:31,560 (GULPING SQUEAKS AND HONKS) 148 00:10:35,160 --> 00:10:38,080 The calls of the emerged now encourage the others 149 00:10:38,120 --> 00:10:40,640 to break out of their eggs. 150 00:10:40,680 --> 00:10:42,960 (HONKS) 151 00:10:44,600 --> 00:10:48,440 But they still can't get out of the nest without help. 152 00:10:51,880 --> 00:10:54,320 Individually, they can barely be heard. 153 00:10:54,360 --> 00:10:56,160 (HONKS) 154 00:10:57,320 --> 00:11:01,160 But together they become loud enough for their mother to hear them. 155 00:11:01,200 --> 00:11:04,400 (MANY HONKING SIMULTANEOUSLY) 156 00:11:04,440 --> 00:11:06,760 (CHORUS OF HONKS) 157 00:11:06,800 --> 00:11:10,640 She has been waiting for these sounds for nearly 70 days. 158 00:11:11,800 --> 00:11:15,280 (ANIMATED HONKING) 159 00:11:21,040 --> 00:11:22,760 (HONKING) 160 00:11:24,760 --> 00:11:26,120 And she goes into action. 161 00:11:27,880 --> 00:11:30,720 (HATCHLINGS HONK AND CHITTER) 162 00:11:57,480 --> 00:12:00,120 One by one, she picks her hatchlings up 163 00:12:00,160 --> 00:12:02,360 and takes them down to the water. 164 00:12:19,440 --> 00:12:23,240 The last to hatch are sometimes forgotten. 165 00:12:24,800 --> 00:12:28,680 But with the nest fully opened, they can now get out. 166 00:12:30,600 --> 00:12:33,440 But they have no idea where their mother is. 167 00:12:35,080 --> 00:12:38,360 (HONK AND CHITTER) Once again, they are saved by sound. 168 00:12:42,000 --> 00:12:44,840 They can recognise the voices of their siblings 169 00:12:44,880 --> 00:12:46,840 and follow the sound to the water... 170 00:12:46,880 --> 00:12:49,760 where their mother will guard them all. 171 00:12:50,560 --> 00:12:52,240 (CHITTERING) 172 00:12:53,880 --> 00:12:57,800 Sound has guided them on the first and most hazardous journey 173 00:12:57,840 --> 00:12:59,000 of their lives. 174 00:13:02,880 --> 00:13:05,360 (CHITTERING) 175 00:13:16,640 --> 00:13:17,960 (CUCKOO CALLS) 176 00:13:18,000 --> 00:13:22,000 (SHEEP BLEATS, WOODPECKER TAPS, WOOD PIGEON COOS) 177 00:13:22,040 --> 00:13:25,520 (BLACKBIRDS SING, BEES BUZZING) 178 00:13:25,560 --> 00:13:27,360 The sounds of an English spring. 179 00:13:28,200 --> 00:13:32,040 (BIRDSONG AND BUZZING) 180 00:13:37,080 --> 00:13:39,160 For many of the animals that live here, 181 00:13:39,960 --> 00:13:42,080 they carry important messages. 182 00:13:44,080 --> 00:13:46,120 (BEE BUZZING) 183 00:13:48,000 --> 00:13:52,080 This bee has discovered that the flowers are now producing nectar. 184 00:13:55,560 --> 00:13:57,480 She gathers all she can... 185 00:13:59,920 --> 00:14:02,920 and then flies back with the good news. 186 00:14:02,960 --> 00:14:04,800 (BUZZES) 187 00:14:06,840 --> 00:14:09,920 Her colony has been inactive during the colder months. 188 00:14:11,520 --> 00:14:15,280 But now the time has come for action. 189 00:14:15,320 --> 00:14:17,560 (HIVE BUZZES) 190 00:14:26,000 --> 00:14:27,520 (AMPLIFIED BEATING SOUND) 191 00:14:28,680 --> 00:14:31,040 The forager conveys her news 192 00:14:31,080 --> 00:14:34,440 by repeatedly thumping her abdomen on the comb. 193 00:14:34,480 --> 00:14:41,440 Bees, like many insects, don't have ears, 194 00:14:43,320 --> 00:14:45,920 so they can't hear airborne sounds. 195 00:14:45,960 --> 00:14:49,000 (BEATING SOUNDS) 196 00:14:49,040 --> 00:14:51,280 (BUZZING) 197 00:14:52,040 --> 00:14:56,200 But they can feel the vibrations she makes on the comb... 198 00:14:56,240 --> 00:14:59,560 (RAPID TAPPING) 199 00:14:59,600 --> 00:15:04,800 ..detecting it with the sense organs in their legs. 200 00:15:04,840 --> 00:15:06,640 (ECHOEY TAPS) 201 00:15:11,840 --> 00:15:14,440 And those that are still asleep 202 00:15:14,480 --> 00:15:18,760 are alerted by her signal that drums directly into their body. 203 00:15:18,800 --> 00:15:21,000 (CONSTANT TAPPING) 204 00:15:27,520 --> 00:15:31,480 Eventually, the workers are roused into action. 205 00:15:51,880 --> 00:15:55,240 Within days, the hive's depleted stores 206 00:15:55,280 --> 00:15:58,400 are restocked with nectar and pollen... 207 00:15:59,680 --> 00:16:03,960 ..food that will fuel the production of the next generation of bees. 208 00:16:11,520 --> 00:16:13,840 When a colony has grown so much 209 00:16:13,880 --> 00:16:17,640 that it contains around 40,000 individuals, 210 00:16:17,680 --> 00:16:19,880 it prepares to swarm. 211 00:16:20,920 --> 00:16:26,040 But a new swarm will need a queen, and the old queen has already left. 212 00:16:28,040 --> 00:16:30,280 There are several contenders for the role 213 00:16:30,320 --> 00:16:33,680 who are developing in particularly large cells. 214 00:16:35,800 --> 00:16:38,840 Tiny super-sensitive microphones 215 00:16:38,880 --> 00:16:41,480 enable us to hear an extraordinary call, 216 00:16:41,520 --> 00:16:42,800 like the quacking of a duck. 217 00:16:42,840 --> 00:16:44,480 (REPEATED QUACKS) 218 00:16:50,720 --> 00:16:53,400 The unhatched queens are signalling 219 00:16:53,440 --> 00:16:55,480 that they're ready to emerge. 220 00:16:55,520 --> 00:16:56,840 (QUACK-LIKE CHORUS) 221 00:16:57,960 --> 00:17:01,200 The workers detect the vibrations of these calls 222 00:17:01,240 --> 00:17:05,960 and in response they start to release the first queen. 223 00:17:06,000 --> 00:17:07,079 (QUACKING) 224 00:17:11,200 --> 00:17:13,960 If two queens are released at the same time, 225 00:17:14,000 --> 00:17:16,920 they will fight one another to the death. 226 00:17:18,160 --> 00:17:20,640 So, she does her best to make sure 227 00:17:20,680 --> 00:17:23,680 that her rivals remain in their cells. 228 00:17:24,800 --> 00:17:26,560 (WHINING SOUND) 229 00:17:26,599 --> 00:17:31,280 She does that by making a sound beekeepers call a toot. 230 00:17:31,320 --> 00:17:33,480 (WHINY TOOT) 231 00:17:34,520 --> 00:17:35,680 (DEEPER HUM) 232 00:17:35,720 --> 00:17:37,640 Slowed down a thousand times 233 00:17:37,680 --> 00:17:41,480 and using new software that converts vibration to colour, 234 00:17:41,520 --> 00:17:44,640 we can see how she creates this call. 235 00:17:44,680 --> 00:17:46,880 (HUM) 236 00:17:50,960 --> 00:17:53,280 The vibrations travel down her legs, 237 00:17:53,320 --> 00:17:57,000 across the comb, and are detected by the legs of the workers. 238 00:18:00,880 --> 00:18:04,160 (TOOTING) 239 00:18:04,200 --> 00:18:08,320 As she toots, the whole colony, for a few seconds, 240 00:18:08,360 --> 00:18:12,920 stops moving... (RUSTLING STOPS) 241 00:18:12,960 --> 00:18:16,760 ..in recognition that a new queen has ascended the throne. 242 00:18:18,720 --> 00:18:22,520 Each toot is answered by a chorus of quacks 243 00:18:22,560 --> 00:18:25,600 from the rival queens who are still within their cells 244 00:18:25,640 --> 00:18:27,560 and eager to emerge. 245 00:18:28,680 --> 00:18:31,920 But as long as the new queen continues tooting, 246 00:18:31,960 --> 00:18:34,440 the workers will not release her rivals. 247 00:18:37,120 --> 00:18:40,880 The crowned queen toots repeatedly until, after a few days, 248 00:18:40,920 --> 00:18:44,760 she prepares to depart with half of the workers in a swarm. 249 00:18:44,800 --> 00:18:46,840 (HUGE SQUEAKS AND RUSTLING) 250 00:18:47,800 --> 00:18:50,400 The sounds in the hive become increasingly intense, 251 00:18:50,440 --> 00:18:54,040 until finally the swarm leaves the nest. 252 00:18:55,640 --> 00:18:58,160 (UPLIFTING MUSIC) 253 00:19:05,680 --> 00:19:08,360 They re-assemble on a nearby branch... 254 00:19:11,640 --> 00:19:14,920 ..and a new colony will soon be established. 255 00:19:22,600 --> 00:19:24,400 (CHORUS OF CROAKS AND HONKS) 256 00:19:28,760 --> 00:19:30,360 Many animals, when they first appear, 257 00:19:30,400 --> 00:19:33,920 rely on their parents for everything they need 258 00:19:33,960 --> 00:19:36,240 and use sound to keep in touch with them. 259 00:19:36,280 --> 00:19:40,000 (CROAKING AND HONKING) 260 00:19:42,680 --> 00:19:48,160 20,00 flamingos breeding off the Yucatan coast in Mexico. 261 00:19:51,080 --> 00:19:53,400 The noise here is deafening. 262 00:19:53,440 --> 00:19:55,800 (CHORUS OF GRUNTS AND HONKS) 263 00:19:57,040 --> 00:20:01,240 The chicks, nonetheless, are able to exchange intimate sounds 264 00:20:01,280 --> 00:20:02,440 with their parents. 265 00:20:11,440 --> 00:20:14,200 (CROAKS) 266 00:20:14,240 --> 00:20:16,720 This one has only just hatched. 267 00:20:19,560 --> 00:20:23,040 The colony provides protection for its members. 268 00:20:23,080 --> 00:20:29,000 But living in such a huge crowd is nonetheless hazardous. 269 00:20:29,040 --> 00:20:32,480 the chick's very survival depends on its ability 270 00:20:32,520 --> 00:20:35,840 to recognise the voices of its parents. 271 00:20:38,240 --> 00:20:41,360 So it must learn to do so quickly, 272 00:20:41,400 --> 00:20:42,920 because within ten days of hatching, 273 00:20:42,960 --> 00:20:45,720 it and its parents will leave the nest. 274 00:20:45,760 --> 00:20:46,920 (CROAKS, CHICK CHIRRUPS) 275 00:20:48,320 --> 00:20:51,520 The call of each flamingo is unique. 276 00:20:53,040 --> 00:20:55,440 It's a kind of vocal fingerprint. 277 00:20:55,480 --> 00:20:58,200 (CROAKS) How the chick manages in such a din 278 00:20:58,240 --> 00:21:03,280 to memorise and pick out the calls of its parents is unimaginable. 279 00:21:03,320 --> 00:21:05,280 But it does so. 280 00:21:05,320 --> 00:21:07,000 (CROAKS) 281 00:21:07,040 --> 00:21:09,960 (CHIRRUPING) 282 00:21:13,400 --> 00:21:14,720 (HONKING) 283 00:21:14,760 --> 00:21:16,920 (SOFT MUSIC) 284 00:21:23,160 --> 00:21:27,080 This one is taking its first steps out of the nest. 285 00:21:29,680 --> 00:21:33,200 But it's not really ready for the wider world. 286 00:21:38,520 --> 00:21:40,960 Eventually it becomes a little braver. 287 00:21:42,320 --> 00:21:44,760 but now it has a new problem. 288 00:21:45,920 --> 00:21:49,960 It's growing fast and both it and its parents need food. 289 00:21:51,840 --> 00:21:56,000 To get it, the adults must leave the colony and their chick. 290 00:21:57,840 --> 00:22:00,560 The chick cannot fly and will be unable to do so 291 00:22:00,600 --> 00:22:02,160 for another three months. 292 00:22:02,200 --> 00:22:05,720 So, until then, it's very vulnerable. 293 00:22:07,840 --> 00:22:12,480 There are hundreds of youngsters with the same problem. 294 00:22:12,520 --> 00:22:16,880 The young gather together in an enormous creche. 295 00:22:18,240 --> 00:22:20,040 There's safety in numbers. 296 00:22:24,440 --> 00:22:28,080 A few adults have stayed behind to keep the creche together. 297 00:22:31,600 --> 00:22:34,040 The others eventually return. 298 00:22:35,600 --> 00:22:39,120 But now each must recognise its own chick 299 00:22:39,160 --> 00:22:41,880 among the densely packed flock of thousands. 300 00:22:41,920 --> 00:22:44,600 (CACOPHONY OF CLUCKING AND CHITTERING) 301 00:22:50,840 --> 00:22:53,800 Amazingly, each family trio — male, female and chick — 302 00:22:55,640 --> 00:22:58,240 are able to recognise one another's voices. 303 00:23:01,080 --> 00:23:02,080 (CROAKING) 304 00:23:03,760 --> 00:23:07,080 Distinguishing individual calls among this deafening chorus 305 00:23:07,120 --> 00:23:08,280 must be difficult. 306 00:23:10,080 --> 00:23:12,720 And this male can't find his chick. 307 00:23:12,760 --> 00:23:13,920 (CROAKING) 308 00:23:15,480 --> 00:23:18,840 Adults aren't the only ones who are searching. 309 00:23:22,520 --> 00:23:25,080 A crocodile is lurking nearby. 310 00:23:29,120 --> 00:23:30,840 (CALLS) The chick calls... 311 00:23:30,880 --> 00:23:32,240 (CROAKS) 312 00:23:32,280 --> 00:23:34,800 But it can't hear its father's reply. 313 00:23:39,720 --> 00:23:42,160 The crocodile attacks. 314 00:23:45,080 --> 00:23:47,400 (ANXIOUS CHITTER) 315 00:23:59,560 --> 00:24:01,960 (HUGE CHORUS OF CALLS AND CROAKS) 316 00:24:08,800 --> 00:24:10,680 It's failed to grab a chick, 317 00:24:10,720 --> 00:24:14,880 but it did create dangerous confusion in the flock. 318 00:24:17,240 --> 00:24:19,480 The chick has become separated from the others 319 00:24:19,520 --> 00:24:21,680 and seems to be lost. 320 00:24:21,720 --> 00:24:23,520 (CHITTERS) 321 00:24:27,440 --> 00:24:30,560 It begs for food from any individual that passes. 322 00:24:30,600 --> 00:24:32,400 (CHITTERS) 323 00:24:36,760 --> 00:24:40,200 Its father, in another part of the flock, keeps calling. 324 00:24:40,240 --> 00:24:42,240 (CROAKS) 325 00:24:43,440 --> 00:24:46,360 But the chick is too far away to hear him. 326 00:24:50,760 --> 00:24:54,240 And this is how many chicks meet their end. 327 00:24:58,520 --> 00:25:00,280 But not this one. 328 00:25:07,400 --> 00:25:09,400 (HIGH-PITCHED CHIRRUP) It keeps calling. 329 00:25:11,960 --> 00:25:14,440 And from across the lagoon... (CROAKS) 330 00:25:14,480 --> 00:25:15,560 ..its father replies. 331 00:25:17,520 --> 00:25:20,960 (CHITTERING AND CROAKING) 332 00:25:21,000 --> 00:25:23,720 The unique sound of the chick's voice has been recognised 333 00:25:23,760 --> 00:25:28,200 by its father, and the two at last are re-united. 334 00:25:36,480 --> 00:25:38,480 As young animals grow, 335 00:25:38,520 --> 00:25:42,600 they learn to recognise oncoming dangers and become big enough 336 00:25:42,640 --> 00:25:45,360 for their voices to sound an alarm. 337 00:25:55,160 --> 00:25:57,000 (CHORUS OF HOWLS) 338 00:25:59,880 --> 00:26:01,600 A wolf pack, in Ontario, Canada. 339 00:26:05,400 --> 00:26:08,280 (EERIE HOWLING) 340 00:26:09,320 --> 00:26:12,760 This communal howl binds the pack together 341 00:26:12,800 --> 00:26:15,480 and registers their ownership of a territory. 342 00:26:15,520 --> 00:26:18,560 (WOLVES HOWLING) 343 00:26:22,080 --> 00:26:25,720 With only around 500 of these Eastern wolves left, 344 00:26:25,760 --> 00:26:29,240 this heart-stopping sound is now extremely rare. 345 00:26:29,280 --> 00:26:30,880 (ALL HOWLING) 346 00:26:32,000 --> 00:26:35,400 But this chorus has some new voices. 347 00:26:35,440 --> 00:26:38,040 (HOWLING AND BARKING) 348 00:26:38,080 --> 00:26:41,360 It's August and the pups are joining in. 349 00:26:43,440 --> 00:26:46,080 These youngsters, however, create a problem... 350 00:26:46,920 --> 00:26:49,240 ..one that could endanger them all. 351 00:26:50,080 --> 00:26:52,360 (BIRDSONG) 352 00:26:57,680 --> 00:26:59,600 (DRONE OF BUZZING) 353 00:27:00,520 --> 00:27:02,480 (CHIRPS) 354 00:27:02,520 --> 00:27:05,200 Now, in summer, the days are over 14 hours long. 355 00:27:08,520 --> 00:27:11,400 So the wolves have to hunt in the light. 356 00:27:14,400 --> 00:27:16,520 (WHINES) 357 00:27:18,080 --> 00:27:21,080 The pups are too big to stay in the den, 358 00:27:21,120 --> 00:27:25,480 but too inexperienced to join in the hunt. 359 00:27:25,520 --> 00:27:31,280 So the adults leave them in an open area - a rendezvous site. 360 00:27:32,080 --> 00:27:36,760 Its very openness makes it a great place for play. 361 00:27:36,800 --> 00:27:40,320 But this is a particularly dangerous time in their lives. 362 00:27:41,240 --> 00:27:44,720 Half of them won't live beyond their first year. 363 00:27:46,120 --> 00:27:50,400 What happens here and now will determine whether these will do so. 364 00:27:58,040 --> 00:28:02,120 Two of the youngsters know exactly where they are supposed to stay. 365 00:28:02,160 --> 00:28:05,640 But their sister can't resist exploring. 366 00:28:21,280 --> 00:28:22,680 (HIGH-PITCHED TWEET) 367 00:28:25,720 --> 00:28:29,880 Distracted, she doesn't notice that a black bear is approaching. 368 00:28:33,280 --> 00:28:37,720 This is one of the few animals that will kill a wolf pup. 369 00:28:39,880 --> 00:28:43,240 The wandering youngster seems unaware of the danger. 370 00:28:45,640 --> 00:28:47,360 But her brothers are. 371 00:28:50,640 --> 00:28:53,080 (DISTANT HOWLING) 372 00:28:53,120 --> 00:28:54,960 They sound the alarm. (BOTH HOWL) 373 00:28:57,520 --> 00:29:01,440 Alerted, the wandering pup spots the bear. 374 00:29:03,640 --> 00:29:04,720 (HOWLING) 375 00:29:10,320 --> 00:29:11,440 (BARKS) 376 00:29:16,560 --> 00:29:18,840 (BARKING AND HOWLING) 377 00:29:18,880 --> 00:29:22,640 Now the lives of all three pups are at risk. 378 00:29:25,240 --> 00:29:28,760 But, as the bear moves in, she hears a different call. 379 00:29:32,120 --> 00:29:33,560 It's her own cub. 380 00:29:33,600 --> 00:29:35,240 And he needs his mother. 381 00:29:35,280 --> 00:29:36,320 (GROANS) 382 00:29:38,680 --> 00:29:41,200 (GROANS) 383 00:29:41,240 --> 00:29:42,560 (HOWLS) 384 00:29:42,600 --> 00:29:44,960 It's been a lucky escape for the pups... 385 00:29:45,000 --> 00:29:46,000 (HOWLING) 386 00:29:46,800 --> 00:29:49,160 ..but they are not yet in the clear. 387 00:29:51,360 --> 00:29:53,160 The pups' howls are shorter and higher-pitched 388 00:29:53,200 --> 00:29:55,280 than those of the adults... 389 00:29:57,520 --> 00:30:00,600 ..but they can still be heard many miles away. 390 00:30:03,120 --> 00:30:06,840 (DEEPER HOWL) And they are answered. 391 00:30:08,280 --> 00:30:10,040 (HOWLS) 392 00:30:14,240 --> 00:30:17,080 The sound has alerted an adult wolf. 393 00:30:20,520 --> 00:30:22,800 (PURPOSEFUL MUSIC) 394 00:30:24,920 --> 00:30:27,040 (HOWLS) 395 00:30:28,760 --> 00:30:29,800 It's their father. 396 00:30:31,040 --> 00:30:32,360 (PUPS WHIMPER) 397 00:30:32,400 --> 00:30:34,400 He's returned with food for the pups. 398 00:30:35,440 --> 00:30:37,120 (EXCITED YELPS) 399 00:30:40,200 --> 00:30:45,520 As dusk falls, the pack celebrates with a reunion chorus. 400 00:30:45,560 --> 00:30:48,240 (DISTANT CHORUS OF HOWLS) 401 00:30:49,400 --> 00:30:52,960 Their voices have been crucial in keeping the pack together. 402 00:30:53,000 --> 00:30:55,560 (DISTANT EERIE HOWLS) 403 00:30:55,600 --> 00:30:58,240 But many animals issue warning calls 404 00:30:58,280 --> 00:31:01,160 that contain far more complex information. 405 00:31:01,200 --> 00:31:02,960 (WHIMPERING) 406 00:31:05,760 --> 00:31:09,520 The meerkats, as they grow, learn how to find their own meals. 407 00:31:12,160 --> 00:31:15,120 And they are discovering how to avoid becoming someone else's. 408 00:31:17,400 --> 00:31:20,400 The desert is full of hungry mouths... 409 00:31:21,840 --> 00:31:25,600 ..and meerkats are small and obviously edible. 410 00:31:28,680 --> 00:31:31,480 Their defence is neither armour nor weapon. 411 00:31:33,840 --> 00:31:36,360 Instead, they use sound - 412 00:31:36,400 --> 00:31:38,200 a complicated system of alarms. 413 00:31:41,600 --> 00:31:44,680 These calls are not just generalised alerts. 414 00:31:44,720 --> 00:31:47,360 (SHORT WHOOPS) 415 00:31:50,120 --> 00:31:52,320 This one warns of a flying predator... 416 00:31:53,800 --> 00:31:55,280 (SHORT WHOOPS CONTINUE) 417 00:31:55,320 --> 00:31:58,040 ..and those hearing it look up and scan the sky. 418 00:31:58,080 --> 00:31:59,080 (WHOOPING) 419 00:32:06,760 --> 00:32:10,480 Danger on the ground is indicated by a different call. 420 00:32:10,520 --> 00:32:12,920 (HIGHER-PITCHED HOOTS) 421 00:32:14,000 --> 00:32:15,360 Best to look around. 422 00:32:17,640 --> 00:32:19,400 (GRUNTING) 423 00:32:21,640 --> 00:32:25,960 Snakes are identified by a third signal. 424 00:32:28,320 --> 00:32:31,880 (GRUNTS) 425 00:32:31,920 --> 00:32:34,240 A call from the look-out summons others 426 00:32:34,280 --> 00:32:36,320 to come and help drive it away. 427 00:32:36,360 --> 00:32:38,360 (COBRA HISSES, MEERKATS GROWL) 428 00:32:45,120 --> 00:32:47,560 Meerkat warnings are so detailed 429 00:32:47,600 --> 00:32:50,040 that they can be a bit confusing for youngsters. 430 00:32:54,080 --> 00:32:57,320 So the best thing is to do what everybody else is doing. 431 00:32:58,200 --> 00:32:59,640 (SQUEAKS) 432 00:33:01,920 --> 00:33:04,360 The calls also carry other information, 433 00:33:04,400 --> 00:33:07,680 such as how fast a predator is approaching. 434 00:33:09,160 --> 00:33:12,480 And there is one call which should never be ignored. 435 00:33:12,520 --> 00:33:14,040 (SHORT GRUNTS) 436 00:33:14,080 --> 00:33:19,520 This is the high-urgency call, a warning of immediate danger. 437 00:33:19,560 --> 00:33:23,400 (SERIES OF SHORT GRUNTS) 438 00:33:23,440 --> 00:33:26,120 Not to react to this could be disastrous. 439 00:33:29,640 --> 00:33:33,600 So when you hear this call... (GRUNTING) 440 00:33:33,640 --> 00:33:35,160 ..run for your life! 441 00:33:42,880 --> 00:33:44,920 (GRUNTS) 442 00:33:44,960 --> 00:33:46,960 (BIRDSONG AND CACKLING) 443 00:33:49,520 --> 00:33:53,120 Sounds in the open air are important for many animals. 444 00:33:54,880 --> 00:33:58,720 But there is another world of sound with which we are far less familiar. 445 00:33:59,880 --> 00:34:03,040 We can't hear very well underwater, 446 00:34:03,080 --> 00:34:06,720 because our ears are shaped to work in the air. 447 00:34:07,480 --> 00:34:11,480 But there is a way in which we can eavesdrop on this underwater world, 448 00:34:11,520 --> 00:34:14,880 by using a special kind of underwater microphone 449 00:34:14,920 --> 00:34:17,440 called a hydrophone. 450 00:34:21,400 --> 00:34:24,760 (PULSING CHIRP-LIKE SOUNDS) 451 00:34:24,800 --> 00:34:28,159 I don't know exactly what's making those noises, 452 00:34:28,199 --> 00:34:32,480 it's probably some small invertebrates or maybe a small fish. 453 00:34:32,520 --> 00:34:36,440 We've known for some time that quite a lot of fish produce sounds. 454 00:34:37,440 --> 00:34:40,480 It's only recently, however, that scientists have discovered 455 00:34:40,520 --> 00:34:43,639 just how widespread that ability is. 456 00:34:54,440 --> 00:34:59,880 The ocean covers around 70% of our planet's surface. 457 00:35:06,160 --> 00:35:08,280 And sound also plays a crucial role 458 00:35:08,320 --> 00:35:12,280 in the lives of many of the animals that live in it. 459 00:35:12,320 --> 00:35:14,280 (CROAKING AND CREAKING SOUNDS) 460 00:35:17,800 --> 00:35:20,200 Coral reefs are surprisingly noisy places. 461 00:35:21,320 --> 00:35:22,400 (DEEP CROAKS) 462 00:35:23,960 --> 00:35:25,960 Many of these sounds are made by fish. 463 00:35:27,480 --> 00:35:30,840 (GRUNTING AND CROAKING) 464 00:35:40,400 --> 00:35:42,920 Here too, sound can be important 465 00:35:42,960 --> 00:35:45,680 from the very beginning of an animal's life. 466 00:35:47,320 --> 00:35:51,840 Without it, one of the most strikingly coloured fish on the reef 467 00:35:51,880 --> 00:35:54,200 would never find its way home. 468 00:35:58,440 --> 00:36:00,840 It's just days before a full moon 469 00:36:00,880 --> 00:36:04,560 and this female clownfish is about to lay her eggs. 470 00:36:10,200 --> 00:36:12,280 Clownfish live in small communities, 471 00:36:13,520 --> 00:36:18,280 each based around a particularly large anemone. 472 00:36:23,760 --> 00:36:28,480 In this busy colony, only two adults will reproduce - 473 00:36:28,520 --> 00:36:31,200 the largest, the dominant female... 474 00:36:32,120 --> 00:36:35,680 ..and her partner, the next in size, the dominant male. 475 00:36:37,560 --> 00:36:40,800 There's a strict hierarchy, one that's based on size, 476 00:36:40,840 --> 00:36:43,280 but policed by sound. 477 00:36:44,920 --> 00:36:46,120 (CROAKY GRUNTS) 478 00:36:46,160 --> 00:36:50,280 Her larger body enables her to make the deepest sound 479 00:36:50,320 --> 00:36:54,560 by snapping her teeth together to produce pops and pulses. 480 00:36:54,600 --> 00:36:57,440 (PULSING GRUNTS) 481 00:37:02,320 --> 00:37:04,960 (SHORT GRUNTS) 482 00:37:07,160 --> 00:37:10,000 The male signals his subordinate status 483 00:37:10,040 --> 00:37:12,120 by quivering his head 484 00:37:12,160 --> 00:37:14,360 and producing a purring noise. 485 00:37:16,800 --> 00:37:20,840 And everyone around the anemone knows that she is the boss. 486 00:37:25,840 --> 00:37:28,960 At full moon, she will be ready to lay eggs. 487 00:37:31,440 --> 00:37:34,480 So the group needs to find a firm surface for them. 488 00:37:36,680 --> 00:37:39,000 A coconut shell, brought in by the currents, 489 00:37:39,040 --> 00:37:41,080 would be ideal. 490 00:37:43,480 --> 00:37:45,760 But it needs to be moved into the right position. 491 00:37:47,800 --> 00:37:50,560 She indicates her needs with a low-pitched grunt, 492 00:37:50,600 --> 00:37:55,320 and the juveniles in the colony comply by shaking their heads. 493 00:38:03,000 --> 00:38:04,960 (MYSTERIOUS MUSIC) 494 00:38:05,000 --> 00:38:09,320 Working together, they manoeuvre the coconut shell into position. 495 00:38:12,040 --> 00:38:15,360 Team work takes a lot of co-ordination, 496 00:38:15,400 --> 00:38:18,200 and a lot of grunting and jaw-grinding. 497 00:38:25,960 --> 00:38:30,120 Next, the stage needs to be prepared. 498 00:38:36,360 --> 00:38:38,080 And at last, the moment arrives. 499 00:38:44,680 --> 00:38:48,040 She lays her eggs in neat lines. 500 00:39:02,920 --> 00:39:07,400 The male then makes HIS contribution - fertilising the eggs. 501 00:39:14,440 --> 00:39:16,000 Now he takes charge. 502 00:39:20,240 --> 00:39:24,080 For the next seven days, he will fan and clean the eggs as they develop. 503 00:39:34,160 --> 00:39:37,480 Three more days and the embryos begin to respond 504 00:39:37,520 --> 00:39:39,800 to the sounds around them. 505 00:39:39,840 --> 00:39:41,760 (GRUNTING) 506 00:39:41,800 --> 00:39:45,960 The sounds that they hear now could play a critical role 507 00:39:46,000 --> 00:39:48,400 in the next stage of their lives. 508 00:39:53,680 --> 00:39:58,200 But a different sort of noise is already threatening their survival. 509 00:40:04,480 --> 00:40:07,840 The male reacts to the noise of a boat as he would to a predator. 510 00:40:12,880 --> 00:40:14,800 If there is constant motor traffic, 511 00:40:14,840 --> 00:40:18,840 he spends more time hiding and less tending the eggs... 512 00:40:18,880 --> 00:40:21,320 so they are more vulnerable to predators and disease. 513 00:40:21,360 --> 00:40:24,720 (THRUM OF MOTOR BOAT) 514 00:40:25,920 --> 00:40:29,280 The noise around these reefs has increased dramatically 515 00:40:29,320 --> 00:40:33,840 in recent decades, and that has affected the lives of the fish here. 516 00:40:36,560 --> 00:40:40,240 But the clownfish father has managed to keep his young healthy, 517 00:40:40,280 --> 00:40:43,160 and a week later, they begin to change. 518 00:40:46,280 --> 00:40:49,240 The plankton-sized fry wriggle free 519 00:40:49,280 --> 00:40:53,040 and are then swept away from the reef by ocean currents. 520 00:40:53,080 --> 00:40:55,480 (UPLIFTING CELLO MUSIC) 521 00:41:03,760 --> 00:41:08,680 For ten days, the larval fish drift out in the open ocean. 522 00:41:14,640 --> 00:41:16,240 (BIRDS CRY) 523 00:41:20,200 --> 00:41:24,120 By the time that each is about the size of a grain of rice, 524 00:41:24,160 --> 00:41:27,760 they are strong enough to swim against the current. 525 00:41:28,960 --> 00:41:32,240 And they need to find their way back to a reef. 526 00:41:40,200 --> 00:41:43,560 The key to their homecoming is sound. 527 00:41:45,720 --> 00:41:50,640 Underwater, the sounds of a reef can be heard for many miles around. 528 00:41:50,680 --> 00:41:55,280 The tiny young clownfish can hear this noise and swim towards it. 529 00:41:58,720 --> 00:42:02,080 They can even judge the health of a reef by its sound. 530 00:42:02,120 --> 00:42:05,480 The noisier it is, the more vigorous it is. 531 00:42:05,520 --> 00:42:07,520 (CLACKING AND BUBBLING) 532 00:42:26,160 --> 00:42:29,880 The anemone will provide him with shelter and sanctuary 533 00:42:29,920 --> 00:42:33,640 for the rest of his life. 534 00:42:33,680 --> 00:42:36,320 Sound has brought him home. 535 00:42:36,360 --> 00:42:38,280 (UPLIFTING MUSIC) 536 00:42:40,920 --> 00:42:44,440 For these fish, and for many other baby animals, 537 00:42:44,480 --> 00:42:48,920 sound is crucial for launching themselves into the world 538 00:42:48,960 --> 00:42:53,480 and learning what they need to stay safe and to thrive. 539 00:42:54,560 --> 00:42:58,040 For them, sound is survival. 540 00:43:04,960 --> 00:43:07,440 (GENTLE MUSIC) 541 00:43:22,640 --> 00:43:24,720 What's one of the close ones over here... 542 00:43:24,760 --> 00:43:28,520 Biologist Mark Meekan became fascinated by coral reefs 543 00:43:28,560 --> 00:43:29,840 more than 30 years ago. 544 00:43:31,040 --> 00:43:33,520 'Coral reefs are these incredible habitats 545 00:43:33,560 --> 00:43:37,360 and I've always been struck by their diversity 546 00:43:37,400 --> 00:43:39,720 and just incredible beauty.' 547 00:43:39,760 --> 00:43:43,480 Today he is fighting to save these reefs 548 00:43:43,520 --> 00:43:46,120 from the ravages of climate change. 549 00:43:46,160 --> 00:43:49,800 This is Australia's Ningaloo Reef 550 00:43:49,840 --> 00:43:52,520 that stretches along the country's western coast. 551 00:43:54,480 --> 00:43:55,760 But over decades of research, 552 00:43:55,800 --> 00:43:58,440 Mark discovered something else — 553 00:43:58,480 --> 00:44:01,720 that coral reefs are full of sound. 554 00:44:04,160 --> 00:44:06,480 A hunch about the significance of this inspired him 555 00:44:06,520 --> 00:44:11,400 to try and find a way to use this sound to save coral reefs. 556 00:44:13,000 --> 00:44:14,840 'If we could hear underwater, 557 00:44:14,880 --> 00:44:18,640 we would hear this cacophony of hoots and yowls, 558 00:44:18,680 --> 00:44:21,440 really strange screams made by fish. 559 00:44:22,600 --> 00:44:26,120 And these little fish may actually be helping the coral to grow. 560 00:44:26,160 --> 00:44:31,720 Basically, by sheltering in the coral, pooping in the coral, 561 00:44:31,760 --> 00:44:33,120 fertilising the coral. 562 00:44:35,040 --> 00:44:38,760 A healthy reef is really very noisy.' 563 00:44:38,800 --> 00:44:41,080 This sound is key. 564 00:44:41,120 --> 00:44:44,960 After hatching, reef fish are swept out to sea. 565 00:44:45,000 --> 00:44:48,960 When they return, they use these healthy sounds 566 00:44:49,000 --> 00:44:51,680 to choose the reef that will be their home. 567 00:44:51,720 --> 00:44:54,040 And this was just a wow moment. 568 00:44:54,080 --> 00:44:57,920 We suddenly thought, "We can actually use this to help the reef." 569 00:45:00,480 --> 00:45:05,280 The result is a multi-million-dollar project with one goal — 570 00:45:05,320 --> 00:45:10,320 to discover if sound can also help save a dying reef. 571 00:45:16,000 --> 00:45:20,520 The first step is to collect three and a half tons of coral debris. 572 00:45:22,440 --> 00:45:24,840 It's alive and extremely vulnerable. 573 00:45:28,920 --> 00:45:31,320 Mark's team build 60 experimental reefs. 574 00:45:34,280 --> 00:45:38,440 Underwater speakers are guided to some of these and turned on. 575 00:45:41,120 --> 00:45:43,400 It's their job to attract fish 576 00:45:43,440 --> 00:45:46,160 by playing the sounds of a healthy reef. 577 00:45:47,320 --> 00:45:51,280 The results will be compared to experimental reefs 578 00:45:51,320 --> 00:45:53,240 without speakers. 579 00:45:57,880 --> 00:46:00,960 At Ningaloo, it's a new moon. 580 00:46:03,760 --> 00:46:06,440 Tonight, the reef fish are coming home. 581 00:46:08,320 --> 00:46:09,880 (BUBBLING AND POPPING SOUNDS) 582 00:46:09,920 --> 00:46:13,400 At the experimental sites, speakers are on, 583 00:46:13,440 --> 00:46:17,120 broadcasting the sounds of a healthy reef. 584 00:46:19,280 --> 00:46:20,960 OK, get ready, Daphne. 585 00:46:21,000 --> 00:46:23,440 They are laying out light traps 586 00:46:23,480 --> 00:46:26,680 and assessing if the speakers are attracting fish 587 00:46:26,720 --> 00:46:30,280 to the experimental reefs with sound 588 00:46:30,320 --> 00:46:32,400 versus ones without. 589 00:46:33,360 --> 00:46:34,680 And they are! 590 00:46:34,720 --> 00:46:36,800 'We actually got the fish to come. 591 00:46:38,280 --> 00:46:41,480 They arrived in big numbers on the reefs.' 592 00:46:45,440 --> 00:46:50,360 Mark's team have been photographing these reefs for 12 months. 593 00:46:54,800 --> 00:46:57,760 Now they're going to see if the fish have helped the coral to grow again. 594 00:47:01,240 --> 00:47:05,560 So, on the left here, we've got our patch reef model from one year ago. 595 00:47:05,600 --> 00:47:09,360 And on the right-hand side, our reef model from a couple of days ago. 596 00:47:09,400 --> 00:47:13,400 You can see fairly obviously already 597 00:47:13,440 --> 00:47:16,200 there's been a fair bit of growth over the year. 598 00:47:18,520 --> 00:47:22,240 Wow! This one's roughly 20cm across, 599 00:47:22,280 --> 00:47:23,640 maximum diameter, 600 00:47:23,680 --> 00:47:26,000 and the same colony a year later, it's almost 40. 601 00:47:26,040 --> 00:47:30,040 So we've doubled in size. Fantastic, man. 602 00:47:31,440 --> 00:47:32,680 (LAUGHS) 603 00:47:32,720 --> 00:47:34,400 Wow. 604 00:47:34,440 --> 00:47:35,800 (SOUNDS OF PIPS AND POPS) 605 00:47:37,800 --> 00:47:40,000 oral reefs today are in such a state 606 00:47:40,040 --> 00:47:43,640 that we're beyond shouting to everybody that it's bad. 607 00:47:43,680 --> 00:47:47,240 We have to move into doing something about it. 608 00:47:50,520 --> 00:47:54,560 The sound made by fish might just be a vital tool 609 00:47:54,600 --> 00:47:58,640 to help scientists save coral reefs around the globe. 610 00:48:03,600 --> 00:48:06,640 (SPRINGTIME BIRDSONG) 611 00:48:09,120 --> 00:48:11,400 (CUCKOO CALLS) 612 00:48:13,720 --> 00:48:16,240 (BLACKBIRD SINGS) 613 00:48:17,920 --> 00:48:20,680 (SHEEP BLEATS) 614 00:48:25,800 --> 00:48:27,560 (WOOD PIGEON COOING) 615 00:48:33,600 --> 00:48:36,040 AccessibleCustomerService@sky.uk 46568

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