1 00:00:10,005 --> 00:00:13,325 (ANIMALS HOOT AND CHATTER) 2 00:00:15,325 --> 00:00:19,165 The natural world is filled with sound. 3 00:00:19,205 --> 00:00:21,285 (THUNDERCLAP) 4 00:00:21,325 --> 00:00:24,765 But so far, we've been hearing only part of it. 5 00:00:24,805 --> 00:00:26,565 (CHITTERS) 6 00:00:26,605 --> 00:00:28,565 (GROWLS) 7 00:00:28,605 --> 00:00:30,885 (CHIRPS) (BUZZES) 8 00:00:30,925 --> 00:00:36,645 New audio technology now captures sounds that we can't even hear. 9 00:00:36,685 --> 00:00:39,445 (DEEP, RESONANT RUMBLING) 10 00:00:42,085 --> 00:00:46,485 For some animals, sound is the key to finding a mate... 11 00:00:46,525 --> 00:00:48,925 (CHIRPS) 12 00:00:50,845 --> 00:00:52,405 ..to impress others... 13 00:00:52,445 --> 00:00:55,325 (CHIRPING, WHISTLING) 14 00:00:55,365 --> 00:00:58,005 (RUMBLING, POPPING) 15 00:00:58,045 --> 00:01:00,325 ..and to warn off the competition. 16 00:01:01,405 --> 00:01:03,885 (BELLOWS) 17 00:01:11,605 --> 00:01:15,005 (ANIMALS CHIRP AND CALL) 18 00:01:23,085 --> 00:01:25,085 (TWEETS) 19 00:01:26,165 --> 00:01:29,925 (CHIRPS, CHITTERS) 20 00:01:37,645 --> 00:01:39,645 (SINGS) 21 00:01:40,764 --> 00:01:43,365 (BIRDS CHIRP AND WHISTLE) 22 00:01:48,484 --> 00:01:51,125 (SINGS, CHIRPS) 23 00:01:51,165 --> 00:01:54,685 A British woodland in spring. 24 00:01:54,725 --> 00:01:59,445 The air is filled with the sound of bird song. 25 00:01:59,484 --> 00:02:04,765 It's a sound that brings a lot of people a lot of pleasure... 26 00:02:04,805 --> 00:02:06,845 including me. 27 00:02:06,885 --> 00:02:11,325 And all these birds are singing for two reasons... 28 00:02:11,365 --> 00:02:14,685 one - to establish a territory, 29 00:02:14,725 --> 00:02:18,005 and two - to attract a mate. 30 00:02:18,045 --> 00:02:20,045 (BIRDS SING AND CHIRP) 31 00:02:23,245 --> 00:02:26,965 Song travels well in an open woodland. 32 00:02:28,365 --> 00:02:33,405 But making yourself heard can be more challenging in a noisier environment. 33 00:02:35,605 --> 00:02:39,525 And there is one creature here that has risen to that challenge. 34 00:02:46,525 --> 00:02:51,525 This delightful little bird is a white-throated dipper. 35 00:02:52,845 --> 00:02:54,845 For most birds of its size, 36 00:02:54,885 --> 00:02:58,925 living beside streams is rather a dangerous place. 37 00:03:03,085 --> 00:03:05,965 Feathers, when they are wet, on a bird of this size, 38 00:03:06,005 --> 00:03:08,565 aren't much good for flying, 39 00:03:08,605 --> 00:03:11,685 but the dipper knows how to deal with that. 40 00:03:13,445 --> 00:03:16,084 As it searches for food between the rocks, 41 00:03:16,125 --> 00:03:21,125 it stops frequently to cover its feathers with oil from a preen gland 42 00:03:21,165 --> 00:03:23,805 so that they stay waterproof and dry. 43 00:03:27,365 --> 00:03:30,205 Reaching your food underwater... 44 00:03:30,245 --> 00:03:33,045 is just one of the problems faced by the dipper. 45 00:03:33,084 --> 00:03:35,925 Another is how do you send messages 46 00:03:35,965 --> 00:03:40,565 above the noise of the fast-flowing stream by which you live? 47 00:03:41,365 --> 00:03:44,285 But the dipper has a way of dealing with that as well. 48 00:03:46,325 --> 00:03:48,485 It's the breeding season... 49 00:03:49,805 --> 00:03:53,605 ..and this male uses his voice to find a partner. 50 00:03:54,605 --> 00:03:56,605 (WATER RUSHING, SOFT CHIRPING) 51 00:03:59,045 --> 00:04:02,245 To our ears, his singing can hardly be heard 52 00:04:02,285 --> 00:04:04,925 above the sound of the water. 53 00:04:07,885 --> 00:04:11,045 But eliminating the sounds of the river 54 00:04:11,085 --> 00:04:15,845 reveals a surprisingly complex and melodious song. 55 00:04:15,885 --> 00:04:18,885 (ARTICULATED CHIRPS) 56 00:04:25,525 --> 00:04:28,045 Most of the dipper's notes are higher-pitched 57 00:04:28,085 --> 00:04:30,485 than the noise of the water. 58 00:04:30,525 --> 00:04:32,965 (MELODIC CHIRPING) 59 00:04:34,805 --> 00:04:38,405 This allows others to hear his song more easily. 60 00:04:43,685 --> 00:04:47,685 He has attracted the attention of a female. 61 00:04:47,725 --> 00:04:51,725 (ELABORATE CHIRPING) 62 00:04:56,725 --> 00:05:01,605 Only males in peak condition can sing complex tunes like this. 63 00:05:07,445 --> 00:05:10,605 (SINGING) 64 00:05:10,645 --> 00:05:12,645 His song has impressed, 65 00:05:12,685 --> 00:05:16,325 and his new mate will stay with him for the rest of the year 66 00:05:16,365 --> 00:05:18,765 and help him defend this territory. 67 00:05:18,805 --> 00:05:21,605 (COMPLEX CHIRPING) 68 00:05:33,485 --> 00:05:36,925 Six weeks later, and the pair have been busy. 69 00:05:44,365 --> 00:05:48,164 Concealed behind the waterfall is their nest. 70 00:06:01,605 --> 00:06:05,205 To ensure a steady supply of food for the chicks, 71 00:06:05,245 --> 00:06:08,765 the pair have to defend their stretch of river from others. 72 00:06:10,445 --> 00:06:14,565 And its their song that acts as a warning to rivals. 73 00:06:14,605 --> 00:06:16,405 (SINGS) 74 00:06:23,845 --> 00:06:27,205 Together, they present a united front. 75 00:06:27,245 --> 00:06:29,805 (SINGING) 76 00:06:35,085 --> 00:06:39,125 For any intruders, the message is loud and clear. 77 00:06:39,164 --> 00:06:42,925 (ELABORATE CHIRPING AND SINGING) 78 00:06:51,885 --> 00:06:54,645 Keeping the chicks well-fed is crucial, 79 00:06:54,685 --> 00:06:57,445 and not just for their growth. 80 00:06:58,885 --> 00:07:01,965 It's needed to develop the part of the brain 81 00:07:02,005 --> 00:07:04,445 responsible for learning song. 82 00:07:06,125 --> 00:07:09,845 So, they will, one day, become proficient singers, 83 00:07:09,885 --> 00:07:11,885 like their parents. 84 00:07:17,165 --> 00:07:22,245 Two weeks on, and all three chicks have fledged successfully. 85 00:07:28,405 --> 00:07:30,285 (CHIRPING) 86 00:07:30,325 --> 00:07:34,485 These youngsters have had the best possible start in life... 87 00:07:36,605 --> 00:07:39,605 ..thanks to their parents and their song. 88 00:07:39,645 --> 00:07:41,685 (SINGS) 89 00:07:47,285 --> 00:07:49,605 When it comes to finding a mate, 90 00:07:49,645 --> 00:07:52,685 power, not melody, is sometimes needed. 91 00:07:56,725 --> 00:08:01,925 (HIGH-PITCHED CALLS) 92 00:08:04,005 --> 00:08:07,045 (RESONANT CALLS AND GRUNTS) 93 00:08:13,685 --> 00:08:17,445 Autumn in the Rocky Mountains of Canada. 94 00:08:17,485 --> 00:08:20,165 (SNORTS) 95 00:08:23,165 --> 00:08:25,405 (HIGH-PITCHED CALL) 96 00:08:32,804 --> 00:08:37,405 This bugling call of the elk marks the change of season... 97 00:08:37,445 --> 00:08:41,405 and the beginning of the annual rut. 98 00:08:48,285 --> 00:08:51,805 (DEEP VOCALISATIONS) 99 00:08:53,525 --> 00:08:57,565 This bull is in his prime, and over the next six weeks, 100 00:08:57,605 --> 00:09:02,245 he will push himself close to death in order to mate. 101 00:09:07,845 --> 00:09:12,645 The females will only accept the largest and strongest male. 102 00:09:15,525 --> 00:09:19,565 And his success will depend on the power of his voice. 103 00:09:23,045 --> 00:09:25,565 Stretching his vocal chords, 104 00:09:25,605 --> 00:09:29,885 he produces a high-pitched shriek through his nose. 105 00:09:34,405 --> 00:09:36,965 It travels over a mile... 106 00:09:37,005 --> 00:09:41,125 and announces his presence to distant females. 107 00:09:41,165 --> 00:09:44,325 (BELLOWS) 108 00:09:50,285 --> 00:09:53,805 At the same time, he makes a guttural groan... 109 00:09:53,845 --> 00:09:57,365 (RESONANT BELLOW) 110 00:09:57,405 --> 00:10:01,765 ..which signals his size and strength to nearby males. 111 00:10:03,845 --> 00:10:08,205 The deeper his voice, the bigger and stronger he is. 112 00:10:11,325 --> 00:10:14,485 And he backs it up with a physical display. 113 00:10:28,845 --> 00:10:33,165 (BELLOWS, CALLS) 114 00:10:37,045 --> 00:10:40,445 His goal is to gather as many females as possible... 115 00:10:40,485 --> 00:10:45,445 to ensure that his genes are the ones that are passed on. 116 00:10:45,485 --> 00:10:47,725 (BLEATING) 117 00:11:04,685 --> 00:11:06,885 (HIGH-PITCHED CALL) 118 00:11:06,925 --> 00:11:09,125 (DEEP, RESONANT VOCALISATIONS) 119 00:11:10,285 --> 00:11:13,125 Now he switches to a different call... 120 00:11:13,165 --> 00:11:15,525 (VOCALISATION CONTINUES) 121 00:11:16,405 --> 00:11:21,645 ..a low 'glunking' sound to encourage the females to join him. 122 00:11:25,285 --> 00:11:30,365 A successful bull can attract up to 20 females in one season. 123 00:11:30,405 --> 00:11:33,205 (DEEP VOCALISATIONS) 124 00:11:34,045 --> 00:11:36,765 Chemical cues, detected with his tongue, 125 00:11:36,805 --> 00:11:39,525 tell him which cows are fertile. 126 00:11:51,045 --> 00:11:55,605 But retaining so many females is easier said than done. 127 00:11:55,645 --> 00:11:57,645 (HIGH-PITCHED CALL) 128 00:12:05,525 --> 00:12:08,205 A rival enters the arena. 129 00:12:10,845 --> 00:12:14,085 (BELLOWING) 130 00:12:20,285 --> 00:12:23,805 Their bugles signal that they are equally matched. 131 00:12:26,085 --> 00:12:28,645 There's only one way to settle this. 132 00:12:28,685 --> 00:12:32,605 He must stand his ground or surrender his females. 133 00:13:00,005 --> 00:13:04,965 These battles can result in serious injury, even death. 134 00:13:07,045 --> 00:13:09,325 (HIGH-PITCHED CALL) 135 00:13:22,205 --> 00:13:24,525 For the moment, at least, 136 00:13:24,565 --> 00:13:27,365 his legacy is secure. 137 00:13:36,845 --> 00:13:39,850 (RUMBLING) 138 00:13:41,850 --> 00:13:44,845 (RUMBLING) 139 00:13:46,565 --> 00:13:49,245 On the vast grasslands of Alberta, 140 00:13:49,285 --> 00:13:51,925 it takes teamwork to get noticed. 141 00:13:52,805 --> 00:13:55,045 (COOING) 142 00:13:56,365 --> 00:13:58,725 (RESONANT RATTLING) 143 00:14:00,805 --> 00:14:02,605 Every spring, 144 00:14:02,645 --> 00:14:07,485 male sharp-tailed grouse gather on traditional breeding grounds... 145 00:14:07,525 --> 00:14:09,525 (RATTLING) 146 00:14:09,565 --> 00:14:13,285 ..practising for their most important performance of the year. 147 00:14:14,325 --> 00:14:16,725 (CLUCKING, RATTLING) 148 00:14:16,765 --> 00:14:19,045 And they have a remarkable array 149 00:14:19,085 --> 00:14:21,805 of musical instruments at their disposal. 150 00:14:26,165 --> 00:14:28,125 Feet are stamped, 151 00:14:28,165 --> 00:14:32,485 and tail feathers rattled, to produce a rhythmic beat. 152 00:14:38,325 --> 00:14:40,845 A low cooing sound, 153 00:14:40,885 --> 00:14:43,805 amplified by inflatable air sacs, 154 00:14:43,845 --> 00:14:47,045 provides the accompanying tune. 155 00:14:47,085 --> 00:14:48,885 (CLUCKING, RATTLING) 156 00:14:48,925 --> 00:14:52,725 And it's all to attract the attention of the females. 157 00:14:54,405 --> 00:14:58,325 The more males, the louder and more impressive their performance. 158 00:14:58,365 --> 00:15:01,565 (COOING, RATTLING) 159 00:15:01,605 --> 00:15:04,925 But sometimes, tensions boil over. 160 00:15:15,005 --> 00:15:18,205 (CLUCKING) 161 00:15:22,325 --> 00:15:25,405 They need to stop squabbling and work together. 162 00:15:25,445 --> 00:15:27,445 (RATTLING) 163 00:15:48,285 --> 00:15:52,485 Their combined song and dance has attracted a female. 164 00:15:54,885 --> 00:15:57,405 (CLUCKING) 165 00:15:58,525 --> 00:16:02,285 Time for the synchronised finale. 166 00:16:07,205 --> 00:16:09,805 They all freeze. 167 00:16:11,605 --> 00:16:15,405 She takes the opportunity to assess each male. 168 00:16:18,885 --> 00:16:20,925 (RATTLING RESUMES) 169 00:16:33,645 --> 00:16:37,805 Now she's looking for the fastest tail rattle. 170 00:16:43,085 --> 00:16:45,685 And a sound like the popping of a cork... 171 00:16:45,725 --> 00:16:48,485 (POPPING) 172 00:16:51,645 --> 00:16:54,325 ..which females find irresistible. 173 00:16:56,525 --> 00:17:00,365 Their display will help her find the fittest male in the group. 174 00:17:02,845 --> 00:17:05,485 And this one has caught her attention. 175 00:17:07,965 --> 00:17:11,885 But not everyone is sticking to the dance routine. 176 00:17:13,525 --> 00:17:16,165 A young, over-enthusiastic male 177 00:17:16,205 --> 00:17:19,245 is ruining the performance for everyone. 178 00:17:19,285 --> 00:17:21,485 (CLUCKS) 179 00:17:26,124 --> 00:17:28,084 She's seen enough. 180 00:17:28,124 --> 00:17:30,125 And she's off. 181 00:17:32,605 --> 00:17:34,605 (RATTLING) 182 00:17:36,005 --> 00:17:39,005 Today didn't go as planned. 183 00:17:39,045 --> 00:17:41,005 (CLUCKS) 184 00:17:41,045 --> 00:17:45,805 But tomorrow, they'll have the chance to do it all over again. 185 00:17:48,885 --> 00:17:52,165 While grouse benefit from joining forces, 186 00:17:52,205 --> 00:17:56,325 others must find a way to stand out from the crowd. 187 00:17:56,365 --> 00:17:58,365 (HIGH-PITCHED SHRIEKS) 188 00:18:01,725 --> 00:18:03,805 In the deserts of Arizona, 189 00:18:03,845 --> 00:18:08,085 temperatures can soar above 40 degrees Celsius. 190 00:18:10,325 --> 00:18:13,605 Rain hasn't fallen here for several months. 191 00:18:19,925 --> 00:18:22,645 But things are about to change. 192 00:18:22,685 --> 00:18:24,965 (THUNDER RUMBLES) 193 00:18:26,205 --> 00:18:28,485 (WIND HOWLS) 194 00:18:28,525 --> 00:18:30,525 (CRACKLES) 195 00:18:31,965 --> 00:18:34,605 (THUNDERCLAP) 196 00:18:50,525 --> 00:18:52,445 (THUNDERCLAP) 197 00:19:05,125 --> 00:19:08,605 Within hours, the rains flood the ground... 198 00:19:08,645 --> 00:19:11,325 and temporary pools appear. 199 00:19:16,565 --> 00:19:20,365 The thunder sends shockwaves through the ground... 200 00:19:20,405 --> 00:19:24,005 (THUNDERCLAP) 201 00:19:27,445 --> 00:19:30,485 ..which trigger an annual uprising. 202 00:19:45,125 --> 00:19:47,685 Breaking free from their underground vaults, 203 00:19:47,725 --> 00:19:51,245 desert frogs and toads emerge to breed. 204 00:19:52,925 --> 00:19:56,205 (CROAKS) 205 00:19:57,645 --> 00:20:00,725 (CACOPHONOUS CROAKING) 206 00:20:00,765 --> 00:20:04,445 They will have just one or two nights to find a mate. 207 00:20:04,485 --> 00:20:07,685 And there are hundreds of frogs in this one pool. 208 00:20:08,925 --> 00:20:11,285 (CROAKING CONTINUES) 209 00:20:16,605 --> 00:20:18,605 Not only that, 210 00:20:18,645 --> 00:20:23,005 at least five different species are all trying to make themselves heard. 211 00:20:25,765 --> 00:20:27,965 (CROAKS) 212 00:20:28,005 --> 00:20:32,165 How is a female to find a male of her own kind? 213 00:20:32,205 --> 00:20:35,165 (CROAKING) 214 00:20:35,205 --> 00:20:39,085 The answer, it seems, lies in their voice. 215 00:20:42,565 --> 00:20:45,685 Each species has its own distinctive call. 216 00:20:47,125 --> 00:20:50,365 (CROAKING, CHIRPING) 217 00:20:53,445 --> 00:20:54,765 (DEEP, RATTLING CROAK) 218 00:20:54,805 --> 00:20:56,885 (GROANS) 219 00:20:56,925 --> 00:21:01,445 And now we can see just how the females do it. 220 00:21:03,325 --> 00:21:06,965 A specialised acoustic camera shows sounds 221 00:21:07,005 --> 00:21:09,845 of different frequencies in different colours... 222 00:21:09,885 --> 00:21:12,445 (GROANING, CROAKING, CHIRPING) 223 00:21:14,125 --> 00:21:19,645 ..and reveals that each species favours different notes and rhythms, 224 00:21:19,685 --> 00:21:24,045 allowing females to pinpoint males of their own kind. 225 00:21:32,445 --> 00:21:34,445 When it comes to mating, 226 00:21:34,485 --> 00:21:37,805 it generally makes sense to stick with your own species. 227 00:21:40,885 --> 00:21:45,205 But desperate times can lead to desperate measures. 228 00:21:46,445 --> 00:21:48,445 On the other side of the valley, 229 00:21:48,485 --> 00:21:50,685 the rains have been less plentiful, 230 00:21:50,725 --> 00:21:53,845 and the pools here are dangerously shallow. 231 00:21:54,645 --> 00:21:57,045 (CROAKING) 232 00:21:57,085 --> 00:22:01,565 This plains spadefoot needs her young to develop quickly 233 00:22:01,605 --> 00:22:03,605 before the water disappears. 234 00:22:06,045 --> 00:22:08,325 It's a race against the clock, 235 00:22:08,365 --> 00:22:11,685 and the calls of two different species are deafening. 236 00:22:11,725 --> 00:22:13,885 (CROAKING, CHIRPING) 237 00:22:27,885 --> 00:22:32,285 She tunes into the calls of her own kind of male. 238 00:22:32,325 --> 00:22:35,765 (CROAKS RHYTHMICALLY) 239 00:22:43,605 --> 00:22:47,685 But surprisingly, she sidesteps them. 240 00:22:54,845 --> 00:22:58,365 The pulsing call of a Mexican spadefoot 241 00:22:58,405 --> 00:23:00,405 has attracted her attention. 242 00:23:05,005 --> 00:23:07,525 He belongs to a different species, 243 00:23:07,565 --> 00:23:12,125 but, remarkably, she can still mate with him if she so chooses. 244 00:23:14,965 --> 00:23:17,485 And in this case, she does... 245 00:23:17,525 --> 00:23:19,925 and for a specific reason. 246 00:23:22,685 --> 00:23:28,245 His tadpoles will develop faster than those fathered by her own kind 247 00:23:28,285 --> 00:23:33,045 and give her young a chance to reach maturity before the pond dries up. 248 00:23:35,205 --> 00:23:37,685 It's an unusual practice... 249 00:23:37,725 --> 00:23:39,725 but an effective one. 250 00:23:39,765 --> 00:23:43,045 And in an unpredictable and warming climate, 251 00:23:43,085 --> 00:23:46,525 solutions like this may help ensure their survival. 252 00:23:52,525 --> 00:23:55,805 But her decision comes at a price. 253 00:23:58,845 --> 00:24:03,885 Only female offspring produced from this liaison will be fertile. 254 00:24:05,965 --> 00:24:10,205 But she's ensured that at least some of her genes are passed on. 255 00:24:12,525 --> 00:24:15,528 (RUMBLING) 256 00:24:17,528 --> 00:24:20,525 (RUMBLING) 257 00:24:22,685 --> 00:24:24,685 Frogs aren't the only ones 258 00:24:24,725 --> 00:24:27,365 to use their voice under the cover of darkness. 259 00:24:28,205 --> 00:24:30,925 (RESONANT HUMMING) 260 00:24:36,925 --> 00:24:39,645 On the Pacific Coast of North America, 261 00:24:39,685 --> 00:24:43,605 the night air resonates with an eerie hum. 262 00:24:48,925 --> 00:24:52,605 It's a sound that baffled people for years. 263 00:24:59,645 --> 00:25:04,845 It coincides with the arrival of a fish from the open ocean... 264 00:25:09,805 --> 00:25:11,845 ..a plainfin midshipman. 265 00:25:15,285 --> 00:25:17,445 For the next three to four months, 266 00:25:17,485 --> 00:25:21,965 this male will risk his life in the shallow intertidal zone. 267 00:25:24,365 --> 00:25:28,125 He's searching for a suitable spot to make a nest. 268 00:25:41,405 --> 00:25:43,405 This one looks ideal. 269 00:25:45,005 --> 00:25:47,245 Time for some housekeeping. 270 00:26:08,765 --> 00:26:10,885 One final mouthful... 271 00:26:14,605 --> 00:26:16,605 ..and it's complete. 272 00:26:19,765 --> 00:26:23,365 But the females are still in deeper water. 273 00:26:23,405 --> 00:26:26,645 He needs a way of attracting their attention. 274 00:26:28,605 --> 00:26:32,325 The onset of night is his cue. 275 00:26:32,365 --> 00:26:34,565 (DRONING HUM) 276 00:26:38,965 --> 00:26:42,205 By vibrating muscles attached to his swim bladder, 277 00:26:42,245 --> 00:26:45,325 he produces a low-frequency hum 278 00:26:45,365 --> 00:26:47,525 that travels well through water. 279 00:26:47,565 --> 00:26:50,085 (HUMMING CONTINUES) 280 00:26:52,165 --> 00:26:54,245 And he's not alone. 281 00:26:54,285 --> 00:26:56,325 (CHORUS OF HUMMING) 282 00:26:57,165 --> 00:26:59,605 He's joined by dozens of others. 283 00:27:10,925 --> 00:27:15,325 The sound reaches a staggering 110dB - 284 00:27:15,365 --> 00:27:18,485 as loud as a lion's roar... 285 00:27:18,525 --> 00:27:20,245 (HUMMING CONTINUES) 286 00:27:20,285 --> 00:27:23,485 ..giving rise to the mysterious drone 287 00:27:23,525 --> 00:27:27,365 that once puzzled the people who lived on these shores. 288 00:27:28,725 --> 00:27:31,525 (DRONING HUM) 289 00:27:36,165 --> 00:27:40,125 This sound is loud enough to be heard by the females. 290 00:27:46,245 --> 00:27:50,765 Guided by the hum, a female arrives, swollen with eggs. 291 00:27:52,405 --> 00:27:54,165 (DRONING HUM) 292 00:27:54,205 --> 00:27:57,965 The harmonics produced by each male are slightly different, 293 00:27:58,005 --> 00:28:01,085 like a sonic fingerprint, 294 00:28:01,125 --> 00:28:04,125 and help him stand out from the crowd. 295 00:28:08,645 --> 00:28:11,445 His song has drawn her this far, 296 00:28:11,485 --> 00:28:14,885 but now his nest is under scrutiny. 297 00:28:19,245 --> 00:28:21,285 It's to her liking. 298 00:28:24,565 --> 00:28:26,565 Hovering upside down, 299 00:28:26,605 --> 00:28:29,165 she lays her eggs on the roof. 300 00:28:43,965 --> 00:28:46,925 The next morning, she has gone. 301 00:28:48,565 --> 00:28:53,245 The male alone will protect the eggs for the next three months. 302 00:28:55,325 --> 00:28:59,405 During this time, he won't feed or leave them unattended. 303 00:29:03,485 --> 00:29:06,205 A crab...looking for a snack. 304 00:29:07,285 --> 00:29:10,245 (GROWLS) 305 00:29:10,285 --> 00:29:12,965 (GRUNTS) 306 00:29:13,005 --> 00:29:15,725 He sends a warning growl... 307 00:29:15,765 --> 00:29:17,925 (GROWLS) 308 00:29:17,965 --> 00:29:20,885 (GRUNTING) 309 00:29:22,005 --> 00:29:24,325 ..and a grunt. 310 00:29:24,365 --> 00:29:26,565 (GRUNTING) 311 00:29:26,605 --> 00:29:29,285 The crab finally gets the message. 312 00:29:32,885 --> 00:29:35,405 But the biggest challenge he faces 313 00:29:35,445 --> 00:29:38,685 comes with the daily changing of the tides. 314 00:29:50,725 --> 00:29:54,525 Midshipman fish are adapted to breathe air, 315 00:29:54,565 --> 00:29:57,765 but the low tide leaves him defenceless. 316 00:30:03,485 --> 00:30:07,285 With no means of escape, it's now down to luck. 317 00:30:33,485 --> 00:30:36,165 On this tide, he's made it. 318 00:30:37,165 --> 00:30:41,365 If he and his eggs can survive the hazardous months ahead, 319 00:30:41,405 --> 00:30:46,405 he will have helped father the next generation of midshipman singers. 320 00:30:50,525 --> 00:30:53,485 Sound travels well underwater. 321 00:30:56,285 --> 00:30:58,925 On land, however, it is often deflected, 322 00:30:58,965 --> 00:31:01,285 or absorbed, by the surroundings. 323 00:31:03,925 --> 00:31:08,725 Thick rainforests pose a particular challenge. 324 00:31:08,765 --> 00:31:10,765 (HOOTING, CHITTERING) 325 00:31:10,805 --> 00:31:14,485 The dense vegetation acts as a sound barrier... 326 00:31:15,645 --> 00:31:17,965 ..and despite the many voices, 327 00:31:18,005 --> 00:31:20,765 most messages don't travel far. 328 00:31:22,445 --> 00:31:24,685 (DEEP CHIRPING) 329 00:31:26,085 --> 00:31:29,085 (HOOTS) 330 00:31:32,605 --> 00:31:35,285 (CHIRPS) 331 00:31:35,325 --> 00:31:36,965 (CHIRPS SQUEAKILY) 332 00:31:38,205 --> 00:31:41,085 (CHITTERS) 333 00:31:41,125 --> 00:31:42,925 (CHITTERS) 334 00:31:42,965 --> 00:31:46,085 (HIGH-PITCHED CROAKS) 335 00:31:49,045 --> 00:31:53,485 In the forests of Southeast Asia, however, there is one animal 336 00:31:53,525 --> 00:31:56,445 that knows exactly how to make its message heard... 337 00:32:02,005 --> 00:32:05,325 ..a yellow-cheeked crested gibbon. 338 00:32:07,645 --> 00:32:12,565 He moves to a higher position where the canopy is less dense. 339 00:32:14,645 --> 00:32:18,405 (HIGH-PITCHED HOOTING) 340 00:32:29,685 --> 00:32:31,725 Unobstructed by trees, 341 00:32:31,765 --> 00:32:36,085 his call carries for over a mile across the forest. 342 00:32:36,125 --> 00:32:38,205 (HIGH-PITCHED HOOTING CONTINUES) 343 00:32:40,085 --> 00:32:42,285 And he's not alone. 344 00:32:42,325 --> 00:32:45,045 His partner and baby are close by. 345 00:32:46,565 --> 00:32:50,765 The female now joins in with her own song. 346 00:32:50,805 --> 00:32:53,725 (HIGH-PITCHED HOOTING) 347 00:32:58,965 --> 00:33:03,525 Together, their duet sends a message to other gibbons. 348 00:33:03,565 --> 00:33:07,885 (HIGH-PITCHED HOOTING) 349 00:33:10,445 --> 00:33:13,925 It's a declaration that this patch is taken, 350 00:33:13,965 --> 00:33:16,525 and the fruiting trees within it. 351 00:33:16,565 --> 00:33:19,765 (HIGH-PITCHED HOOTING) 352 00:33:25,165 --> 00:33:27,485 (HIGH-PITCHED HOOTING) 353 00:33:30,765 --> 00:33:34,205 Their calls spark responses from other pairs, 354 00:33:34,245 --> 00:33:36,805 each protecting their own territory. 355 00:33:42,245 --> 00:33:46,365 It's a noisy but effective early-morning roll call 356 00:33:46,405 --> 00:33:49,085 to establish the order of the forest. 357 00:33:56,565 --> 00:34:00,085 While gibbons sing over the forest canopy... 358 00:34:01,965 --> 00:34:06,605 ..deep within the forest, some animals use the plants themselves 359 00:34:06,645 --> 00:34:08,724 to transmit their messages. 360 00:34:09,765 --> 00:34:13,125 It's a world of sound that we can't hear... 361 00:34:14,164 --> 00:34:16,244 ..but is clear to those that can. 362 00:34:24,005 --> 00:34:26,085 A male treehopper. 363 00:34:28,285 --> 00:34:30,204 Only half an inch long, 364 00:34:30,244 --> 00:34:34,845 it lives in an acoustic world entirely unlike our own. 365 00:34:36,965 --> 00:34:39,845 But with a special laser vibrometer, 366 00:34:39,885 --> 00:34:42,605 we can now hear these sounds. 367 00:34:42,644 --> 00:34:45,325 (DEEP, RESONANT RUMBLING) 368 00:34:51,125 --> 00:34:54,405 He shakes his abdomen a hundred times a second 369 00:34:54,445 --> 00:34:59,085 to produce a low sound that vibrates through the stem. 370 00:34:59,125 --> 00:35:01,405 (DEEP, RESONANT RUMBLING) 371 00:35:02,205 --> 00:35:06,925 It's a courtship song that spreads through every part of the plant. 372 00:35:18,125 --> 00:35:22,005 A female receives his message through her legs... 373 00:35:22,045 --> 00:35:24,125 loud and clear. 374 00:35:27,165 --> 00:35:30,805 She's ready to mate, and she answers back. 375 00:35:30,845 --> 00:35:33,445 (DEEP, RESONANT RUMBLING) 376 00:35:37,765 --> 00:35:40,925 But she could be anywhere on the plant. 377 00:35:43,605 --> 00:35:47,605 To find her, he needs to keep the conversation flowing. 378 00:35:47,645 --> 00:35:51,125 (DEEP, RESONANT RUMBLING) 379 00:36:00,765 --> 00:36:02,765 Using her sound to navigate, 380 00:36:02,805 --> 00:36:05,885 his direction of travel is determined 381 00:36:05,925 --> 00:36:09,925 by whether it hits his front or rear legs first. 382 00:36:16,205 --> 00:36:18,205 He must be quick. 383 00:36:18,245 --> 00:36:21,845 Her signal may be picked up by other males on the same plant. 384 00:36:28,565 --> 00:36:32,325 But this crossroad is proving hard to read. 385 00:36:36,045 --> 00:36:37,725 He checks for directions. 386 00:37:06,765 --> 00:37:09,245 (DEEP, RESONANT RUMBLING) 387 00:37:09,285 --> 00:37:12,285 Now the signal is coming from behind. 388 00:37:13,845 --> 00:37:16,485 He's taken a wrong turn. 389 00:37:23,685 --> 00:37:27,005 His detour has cost him valuable time. 390 00:37:33,925 --> 00:37:36,005 Found her at last. 391 00:37:37,445 --> 00:37:39,445 But he's too late. 392 00:37:39,485 --> 00:37:41,845 Another male has beaten him to it. 393 00:37:45,285 --> 00:37:49,525 However, there are plenty more treehoppers in the forest. 394 00:37:57,205 --> 00:38:00,206 (RUMBLING) 395 00:38:02,206 --> 00:38:05,165 (RUMBLING) 396 00:38:05,205 --> 00:38:07,205 (CHIRPING) 397 00:38:08,125 --> 00:38:12,405 Most animal calls are encoded in their DNA. 398 00:38:12,445 --> 00:38:16,845 But some can enhance their repertoire in other ways. 399 00:38:16,885 --> 00:38:20,205 (CHIRPS AND SINGS) 400 00:38:34,285 --> 00:38:36,365 A starling. 401 00:38:36,405 --> 00:38:39,605 Ah! Ooh, and a hungry one at that. 402 00:38:39,645 --> 00:38:44,085 They are, in fact, one of our most accomplished singers. 403 00:38:44,125 --> 00:38:47,765 And they not only have their own songs, 404 00:38:47,805 --> 00:38:52,205 but they can also mimic the songs of other species. 405 00:38:52,245 --> 00:38:55,525 And it's all done in order to impress the females. 406 00:38:56,805 --> 00:39:00,725 And they're not the only bird that can imitate others. 407 00:39:05,205 --> 00:39:07,925 The forests of Eastern Australia... 408 00:39:07,965 --> 00:39:11,445 are home to one of nature's most accomplished mimics... 409 00:39:14,925 --> 00:39:17,845 (CHIRPS) 410 00:39:22,645 --> 00:39:26,725 (MIMICS MECHANICAL SOUND) 411 00:39:26,765 --> 00:39:28,285 (CHIRPS) 412 00:39:29,965 --> 00:39:33,285 (CHIRPS) 413 00:39:35,845 --> 00:39:38,765 ..the superb lyrebird. 414 00:39:43,805 --> 00:39:47,365 And this mound of earth is his stage. 415 00:39:48,845 --> 00:39:50,845 (MIMICS MECHANICAL SOUND) 416 00:39:50,885 --> 00:39:52,885 (CHIRPS) 417 00:39:54,485 --> 00:39:56,405 (CHIRPS) 418 00:39:56,445 --> 00:39:59,485 This modest performance won't be enough. 419 00:40:00,325 --> 00:40:05,245 Female lyrebirds are fussy and demand more complex songs. 420 00:40:08,165 --> 00:40:10,245 But he has a solution. 421 00:40:10,285 --> 00:40:14,165 He listens carefully to the sounds around him... 422 00:40:14,205 --> 00:40:17,085 (MIMICS ANIMAL HOOTING) 423 00:40:17,125 --> 00:40:22,605 (MIMICS HOOTING AND HOLLERING) 424 00:40:22,645 --> 00:40:28,005 (CONTINUES HOOTING) 425 00:40:28,045 --> 00:40:30,365 ..and mimics them perfectly. 426 00:40:30,405 --> 00:40:33,565 (HIGH-PITCHED SINGING) 427 00:40:33,605 --> 00:40:38,805 (IMITATES BIRD SONG) 428 00:40:43,245 --> 00:40:45,525 (CHIRPS) 429 00:40:45,565 --> 00:40:47,805 (IMITATES CHIRPING) 430 00:40:51,125 --> 00:40:55,165 He can learn the songs of over 20 different birds. 431 00:40:56,045 --> 00:40:58,205 (SINGS) 432 00:40:59,765 --> 00:41:02,605 And he's not only a mimic - 433 00:41:02,645 --> 00:41:05,965 by stringing the songs together in his own way, 434 00:41:06,005 --> 00:41:08,125 he's also a composer. 435 00:41:09,445 --> 00:41:13,605 (WHISTLES, CHIRPS) 436 00:41:22,805 --> 00:41:26,365 (MIMICS MECHANICAL SOUND) 437 00:41:26,405 --> 00:41:30,925 No two lyrebirds sing exactly the same tune. 438 00:41:30,965 --> 00:41:34,125 (CHIRPS, HOOTS) 439 00:41:34,165 --> 00:41:37,805 With age, his songs become more intricate 440 00:41:37,845 --> 00:41:40,845 and give him greater success with the females. 441 00:41:40,885 --> 00:41:46,205 (HOOTS, CHIRPS, SINGS) 442 00:41:48,805 --> 00:41:51,725 But the lyrebird's world is changing, 443 00:41:51,765 --> 00:41:57,125 and urban settlements have replaced much of its natural home. 444 00:41:58,565 --> 00:42:00,925 (HORNS HONK) 445 00:42:00,965 --> 00:42:03,885 And with it have gone many of the songsters 446 00:42:03,925 --> 00:42:06,405 that he relied on for his tunes. 447 00:42:08,645 --> 00:42:13,125 Luckily, this bird is a virtuoso. 448 00:42:13,165 --> 00:42:15,885 (ALARM WAILS) 449 00:42:17,365 --> 00:42:19,405 A car alarm... 450 00:42:21,085 --> 00:42:24,565 (IMITATES ALARM) 451 00:42:24,605 --> 00:42:27,885 (IMITATES CAMERA SHUTTER CLICKING) 452 00:42:27,925 --> 00:42:30,525 ..a camera shutter... 453 00:42:31,365 --> 00:42:33,245 (BABY CRIES) 454 00:42:33,285 --> 00:42:36,205 ..and even a crying human baby. 455 00:42:36,245 --> 00:42:40,605 (IMITATES BABY CRYING) 456 00:42:41,525 --> 00:42:45,565 (WAILS) 457 00:42:45,605 --> 00:42:49,245 This sound...is anyone's guess. 458 00:42:54,365 --> 00:42:57,805 But it's done the trick and got him noticed... 459 00:42:59,285 --> 00:43:01,605 ..a female. 460 00:43:01,645 --> 00:43:04,965 He may have an unusual choice of tunes, 461 00:43:05,005 --> 00:43:08,965 but they add to his repertoire, and that's all matters. 462 00:43:09,005 --> 00:43:11,805 (CHIRPS) 463 00:43:11,845 --> 00:43:15,525 If she is impressed, she'll choose him to father 464 00:43:15,565 --> 00:43:19,485 the next generation of master songsters and mimics. 465 00:43:19,525 --> 00:43:22,925 (HOOTS, CHIRPS) 466 00:43:27,565 --> 00:43:30,325 (HONKING, CHIRPING) 467 00:43:30,365 --> 00:43:34,565 (ANIMALS CALL AND HOOT) 468 00:43:37,245 --> 00:43:41,725 Many of the sounds we hear in nature are the voices of animals. 469 00:43:44,405 --> 00:43:46,725 But some creatures are so quiet, 470 00:43:46,765 --> 00:43:49,805 they appear to be making no sound at all. 471 00:43:51,445 --> 00:43:55,405 We wanted to film one of these - the treehopper. 472 00:43:55,445 --> 00:43:58,405 But how do you record the sound of a creature 473 00:43:58,445 --> 00:44:00,285 we ourselves can't even hear? 474 00:44:02,445 --> 00:44:07,725 Dr Rex Cocroft is a biologist at the University of Missouri. 475 00:44:09,885 --> 00:44:15,485 He's fascinated by creatures that communicate using just vibrations. 476 00:44:18,765 --> 00:44:22,205 There are at least 200,000 species out there 477 00:44:22,245 --> 00:44:25,285 singing in ways that are silent to us. 478 00:44:25,325 --> 00:44:29,445 And that's way more songs than if you add up all of the birds, 479 00:44:29,485 --> 00:44:32,765 and the fish and the whales, and the frogs out there. So... 480 00:44:32,805 --> 00:44:37,045 the majority of animal sounds are ones that we don't actually hear. 481 00:44:38,005 --> 00:44:40,605 Which makes them a challenge to study. 482 00:44:44,565 --> 00:44:49,365 But a special sound-recording device solved the problem. 483 00:44:51,525 --> 00:44:54,205 It's called a vibrometer... 484 00:44:54,245 --> 00:44:57,445 and uses a laser beam to detect the slightest vibrations 485 00:44:57,485 --> 00:44:59,765 on the surface of an object. 486 00:45:01,925 --> 00:45:03,925 By amplifying these sounds, 487 00:45:03,965 --> 00:45:08,965 the vibrometer allowed Rex to listen in on treehopper communication. 488 00:45:10,125 --> 00:45:12,525 (TREEHOPPER CHIRPING AND TAPPING) 489 00:45:14,205 --> 00:45:17,845 This little treehopper sounds like a tap-dancing monkey. 490 00:45:20,325 --> 00:45:23,765 (RHYTHMIC HOOTING) 491 00:45:23,805 --> 00:45:27,805 Another one sounded like an owl laughing at its own joke. 492 00:45:27,845 --> 00:45:29,765 (RHYTHMIC HOOTING) 493 00:45:29,805 --> 00:45:34,205 (CLUCKING) 494 00:45:34,245 --> 00:45:38,005 One male treehopper sounded like a clucking hen. 495 00:45:39,645 --> 00:45:41,525 (CLUCKS) 496 00:45:41,565 --> 00:45:44,325 (TREEHOPPER RATTLING) 497 00:45:44,365 --> 00:45:47,085 Another one sounded like a woodpecker... 498 00:45:47,125 --> 00:45:49,285 followed by a tiny car honking. 499 00:45:49,325 --> 00:45:53,245 (HONKS AND RATTLES) 500 00:45:53,285 --> 00:45:57,565 Oh, my gosh. I was just lost at that moment. 501 00:45:57,605 --> 00:46:02,085 There was no going back because I heard these wonderful...sounds 502 00:46:02,125 --> 00:46:05,085 that were right there in one small plant. 503 00:46:07,125 --> 00:46:10,325 Let me put this here. And how high do you want this? 504 00:46:10,365 --> 00:46:14,965 Rex's discovery proved irresistible to our film crew, 505 00:46:15,005 --> 00:46:18,005 led by Director Nalini Crack. 506 00:46:19,765 --> 00:46:23,885 Nalini wants to record the courtship duet of a treehopper. 507 00:46:28,085 --> 00:46:31,845 Helping her is Vikrant Palan from Polytec, 508 00:46:31,885 --> 00:46:34,765 with his company's most advanced vibrometer. 509 00:46:34,805 --> 00:46:36,525 Yeah. 510 00:46:36,565 --> 00:46:39,085 Getting there. Yeah. Good, good, good. Good, good. 511 00:46:39,125 --> 00:46:43,605 Nalini has placed a female on the stem of the plant. 512 00:46:43,645 --> 00:46:46,885 Let's try putting a male on there 513 00:46:46,925 --> 00:46:48,925 and see if we can get him calling. 514 00:46:52,885 --> 00:46:56,805 The male song will vibrate through the stem. 515 00:46:56,845 --> 00:47:00,605 If the female answers, he'll follow her call. 516 00:47:02,405 --> 00:47:04,405 Go on, little guy. 517 00:47:07,085 --> 00:47:09,125 (DEEP, RESONANT RUMBLING) 518 00:47:09,165 --> 00:47:11,805 (GASPS)Here he goes. Yeah, that was it.That was it? 519 00:47:11,845 --> 00:47:13,245 That was him. Yeah. 520 00:47:14,685 --> 00:47:16,765 (DEEP, RESONANT RUMBLING) Wow!Oh, my God! 521 00:47:21,245 --> 00:47:25,005 But his vibrations aren't having the desired effect. 522 00:47:26,045 --> 00:47:28,725 She doesn't want him. (LAUGHS) 523 00:47:28,765 --> 00:47:30,885 She's not into it. 524 00:47:32,285 --> 00:47:34,325 (DEEP, RESONANT RUMBLING) 525 00:47:37,325 --> 00:47:39,205 (FEMALE TREEHOPPER RUMBLES) Oh, wow. 526 00:47:39,245 --> 00:47:42,325 Finally, his love song is answered. 527 00:47:42,365 --> 00:47:44,005 (LAUGHS) It's amazing. 528 00:47:59,325 --> 00:48:01,765 These insects that sing silently 529 00:48:01,805 --> 00:48:04,445 are just as magical in their way. 530 00:48:06,805 --> 00:48:09,405 We're only just beginning to understand 531 00:48:09,445 --> 00:48:13,885 the secret sounds of nature's smallest creatures. 532 00:48:27,205 --> 00:48:30,325 The story of sound continues... 533 00:48:30,365 --> 00:48:32,445 (CHIRPING) 534 00:48:32,485 --> 00:48:36,245 ..as baby animals attempt to survive 535 00:48:36,285 --> 00:48:38,525 in a perilous world... 536 00:48:38,565 --> 00:48:41,405 with the help of their voices. (CHIRPS)(YELPS) 537 00:48:41,445 --> 00:48:44,885 (HOWLING) 538 00:48:47,285 --> 00:48:50,885 (WHISTLING, CHIRPING) 539 00:48:50,925 --> 00:48:53,925 AccessibleCustomerService@sky.uk