1 00:00:05,200 --> 00:00:06,880 The Great Barrier Reef. 2 00:00:12,160 --> 00:00:15,720 It's home to an extraordinarily diverse community 3 00:00:15,720 --> 00:00:17,880 of animals and plants. 4 00:00:25,760 --> 00:00:29,720 'Here, unknown species are still being found 5 00:00:29,720 --> 00:00:33,880 'and astonishing things discovered about creatures we thought we knew. 6 00:00:36,960 --> 00:00:39,800 'In this series, our research vessel, the Alucia, 7 00:00:39,800 --> 00:00:44,040 'will allow us to explore and understand the reef as never before. 8 00:00:47,480 --> 00:00:50,040 'This marine paradise may be best known 9 00:00:50,040 --> 00:00:52,280 'for its spectacular coral reefs... 10 00:00:54,320 --> 00:00:56,960 '..but it also has 300 sand islands.' 11 00:01:00,280 --> 00:01:02,280 600 continental islands. 12 00:01:06,120 --> 00:01:08,120 Miles of lush forest. 13 00:01:11,160 --> 00:01:13,480 And deep ocean channels. 14 00:01:16,080 --> 00:01:19,840 Each of these habitats attracts a very different set of visitors. 15 00:01:23,960 --> 00:01:26,760 When I first came here almost 60 years ago, 16 00:01:26,760 --> 00:01:29,360 we knew very little about these communities. 17 00:01:31,440 --> 00:01:34,200 But today, new tracking systems are allowing us 18 00:01:34,200 --> 00:01:37,440 to follow the lives of these creatures in new ways. 19 00:01:39,080 --> 00:01:41,200 From the ocean's great predators... 20 00:01:43,200 --> 00:01:46,640 ..to a mysterious whale that seeks out human contact. 21 00:01:50,640 --> 00:01:54,600 I'll discover their surprising reasons for visiting 22 00:01:54,600 --> 00:01:57,480 and reveal why the reef is so important for their survival. 23 00:02:28,000 --> 00:02:31,480 Last time, we looked at the rich community of animals 24 00:02:31,480 --> 00:02:33,760 that lives among the coral, 25 00:02:33,760 --> 00:02:36,960 but the reef also receives visitors. 26 00:02:36,960 --> 00:02:41,680 Some travel for thousands of miles in order to get here 27 00:02:41,680 --> 00:02:43,800 and stay for only a few weeks. 28 00:02:43,800 --> 00:02:47,920 Others linger on the fringes and come in every day. 29 00:02:47,920 --> 00:02:51,640 Each has its own particular reason for doing so. 30 00:02:53,640 --> 00:02:59,040 The Great Barrier Reef consists of 3,000 individual coral reefs. 31 00:02:59,040 --> 00:03:04,920 It stretches for 1,400 miles along Australia's northeast coast. 32 00:03:04,920 --> 00:03:09,240 And every year, it attracts over a million migrating animals. 33 00:03:14,000 --> 00:03:16,760 We're beginning our exploration in the north, 34 00:03:16,760 --> 00:03:19,680 on the outskirts of this vast wilderness. 35 00:03:25,400 --> 00:03:27,280 Our research vessel, the Alucia, 36 00:03:27,280 --> 00:03:30,360 has brought us out here to Osprey Reef. 37 00:03:30,360 --> 00:03:34,400 90 miles, 150 kilometres out in the Coral Sea 38 00:03:34,400 --> 00:03:37,360 from the edge of the Great Barrier. 39 00:03:37,360 --> 00:03:40,400 Isolated though it is, it nonetheless plays a crucial part 40 00:03:40,400 --> 00:03:44,200 in the lives of many of the inhabitants of the Barrier Reef. 41 00:03:45,960 --> 00:03:48,040 What makes Osprey so interesting 42 00:03:48,040 --> 00:03:52,320 is that it lies in the path of the south equatorial current. 43 00:03:54,760 --> 00:03:57,280 This is a moving highway 44 00:03:57,280 --> 00:04:00,560 that sweeps a host of different visitors towards the great reef. 45 00:04:03,000 --> 00:04:04,440 We are here to discover 46 00:04:04,440 --> 00:04:07,640 why this remote outpost is so important to them. 47 00:04:11,320 --> 00:04:15,760 To do that, we're going to use a very special piece of technology, 48 00:04:15,760 --> 00:04:18,000 the Alucia's Triton submarine. 49 00:04:24,560 --> 00:04:28,400 It's the first submersible of its kind ever to dive in these waters. 50 00:04:33,800 --> 00:04:38,880 Huh! It does look as though water's gurgling up here, 51 00:04:38,880 --> 00:04:41,080 but in fact, my feet aren't wet. 52 00:04:44,400 --> 00:04:48,840 S-O, S-O, this is Nadir. Am I clear to vent? Over. 53 00:04:48,840 --> 00:04:53,560 'Copy Nadir. So you are clear to vent, clear to vent. 54 00:04:53,560 --> 00:04:55,800 'Have a good dive, guys.' 55 00:04:55,800 --> 00:04:57,280 Roger. Venting now. 56 00:05:00,640 --> 00:05:01,960 There we are! 57 00:05:04,200 --> 00:05:09,400 'The sub not only gives us stunning 360-degree views, 58 00:05:09,400 --> 00:05:14,960 'it allows us to dive to depths where no unprotected human has ever been.' 59 00:05:18,120 --> 00:05:21,880 For this dive, we are only going down to about 35 metres, 60 00:05:21,880 --> 00:05:23,720 just over 100 feet, 61 00:05:23,720 --> 00:05:27,360 where much of the wildlife we're hoping to film will be feeding. 62 00:05:32,800 --> 00:05:36,200 Marine geologists have recently gathered sufficient data 63 00:05:36,200 --> 00:05:39,440 for us to create an accurate three-dimensional picture 64 00:05:39,440 --> 00:05:42,120 of Osprey Reef for the very first time. 65 00:05:44,280 --> 00:05:48,480 It is, in fact, a huge mountain hidden beneath the waves 66 00:05:48,480 --> 00:05:52,920 and rising steeply from the seafloor 2,400 metres below. 67 00:05:55,160 --> 00:05:59,360 The top of this vast seamount creates a shallow lagoon 68 00:05:59,360 --> 00:06:02,240 that supports a flourishing community of corals. 69 00:06:07,920 --> 00:06:12,760 This wall of rock ahead of me is the flank of Osprey Reef. 70 00:06:12,760 --> 00:06:16,880 When cold, deep, nutrient-rich currents from the ocean 71 00:06:16,880 --> 00:06:20,680 come in and strike it, they defect it upwards. 72 00:06:20,680 --> 00:06:25,560 And that creates an oasis for living creatures of all kinds. 73 00:06:32,000 --> 00:06:34,600 Many creatures live here throughout the year. 74 00:06:34,600 --> 00:06:38,160 And the boss of them all is one kind, sharks. 75 00:06:46,080 --> 00:06:47,720 There's one! Close up. 76 00:06:49,720 --> 00:06:53,760 Whatever else you say about sharks, they are so beautiful in the water. 77 00:06:56,160 --> 00:06:59,360 Resident predators mean one thing - 78 00:06:59,360 --> 00:07:01,240 a plentiful supply of food. 79 00:07:04,920 --> 00:07:08,320 For creatures travelling vast distances to get to the reef, 80 00:07:08,320 --> 00:07:11,920 that makes Osprey a very desirable waypoint on their journey. 81 00:07:16,840 --> 00:07:19,720 Seamounts are stopping-off points for visitors. 82 00:07:19,720 --> 00:07:21,560 They come from far and wide. 83 00:07:21,560 --> 00:07:23,880 From tiger sharks to turtles. 84 00:07:23,880 --> 00:07:29,200 And they come to refuel and also, it seems, recalibrate. 85 00:07:37,440 --> 00:07:40,160 It appears that this is a signpost 86 00:07:40,160 --> 00:07:42,640 and a checkpoint on the way to the reef. 87 00:07:46,200 --> 00:07:48,640 Visitors arrive year round. 88 00:07:50,320 --> 00:07:52,440 Among them are hammerheads. 89 00:07:57,080 --> 00:08:00,760 Like all sharks, they have tiny sensors on their nose 90 00:08:00,760 --> 00:08:04,120 which can pick up signals from the earth's magnetic field. 91 00:08:05,600 --> 00:08:09,560 And that helps them navigate through the blue infinity of the open ocean. 92 00:08:18,520 --> 00:08:20,440 There are tiger sharks here, too. 93 00:08:23,560 --> 00:08:25,440 They come to the reef to feed. 94 00:08:25,440 --> 00:08:27,920 And they seem to know exactly where they're going. 95 00:08:34,680 --> 00:08:38,280 The proportion of their brain dedicated to smell 96 00:08:38,280 --> 00:08:40,360 is the largest of any shark. 97 00:08:42,760 --> 00:08:44,840 Their two nostrils work independently, 98 00:08:44,840 --> 00:08:49,160 allowing them to smell in stereo and track prey over huge distances. 99 00:08:52,680 --> 00:08:54,720 From Osprey, some tiger sharks 100 00:08:54,720 --> 00:08:58,000 travel to a very specific destination on the reef. 101 00:09:02,600 --> 00:09:06,480 230 miles north of Osprey lies Raine Island. 102 00:09:12,240 --> 00:09:16,400 Every summer, the tiger sharks arrive without fail. 103 00:09:16,400 --> 00:09:20,320 They're here to take advantage of a major event on the reef - 104 00:09:20,320 --> 00:09:24,200 the arrival of the female green turtles. 105 00:09:30,680 --> 00:09:35,320 The tiger sharks aren't here to kill, they've come to scavenge on the dead. 106 00:09:35,320 --> 00:09:38,120 The unlucky turtles who have not survived 107 00:09:38,120 --> 00:09:40,320 their exhausting immigration. 108 00:09:41,840 --> 00:09:45,560 This is why the tiger shark has earned the unflattering title... 109 00:09:47,440 --> 00:09:49,160 ..Dustbin of the Sea. 110 00:09:54,240 --> 00:09:57,440 They prefer the easy life of the scavenger, 111 00:09:57,440 --> 00:10:02,000 so the majority of green turtles have little to fear from these predators. 112 00:10:08,240 --> 00:10:12,680 In the summer months, the turtles arrive in thousands. 113 00:10:16,240 --> 00:10:19,720 They have come from as far as New Guinea, Vanuatu 114 00:10:19,720 --> 00:10:21,960 and New Caledonia to the east, 115 00:10:21,960 --> 00:10:25,440 as well as from the Torres Straits and beyond to the west. 116 00:10:28,560 --> 00:10:32,320 Some have travelled an impressive 1,500 miles 117 00:10:32,320 --> 00:10:34,800 to reach this particular beach. 118 00:10:36,040 --> 00:10:39,120 It measures only a few hundred metres across, 119 00:10:39,120 --> 00:10:41,880 a tiny speck in a vast ocean. 120 00:10:41,880 --> 00:10:45,760 But Raine Island plays a major role in their lives. 121 00:10:48,680 --> 00:10:52,800 70% of the Barrier Reef's breeding green turtles come here to lay. 122 00:10:54,880 --> 00:10:58,160 It's one of the most important nesting sites in the world. 123 00:11:03,080 --> 00:11:06,160 I first visited Raine for a television series 124 00:11:06,160 --> 00:11:09,720 called Zoo Quest back in 1957. 125 00:11:11,520 --> 00:11:14,840 At the time, Raine was little known and rarely visited. 126 00:11:16,880 --> 00:11:20,600 It was then I met my first green turtle hatchling. 127 00:11:26,560 --> 00:11:28,360 Back then, we had no idea 128 00:11:28,360 --> 00:11:31,640 just how extraordinary a story these turtles had to tell. 129 00:11:35,440 --> 00:11:37,400 We now know that if they survive, 130 00:11:37,400 --> 00:11:40,760 they'll spend the next 40 years of their lives at sea. 131 00:11:43,720 --> 00:11:46,960 Only then do they return to Raine to breed. 132 00:11:49,520 --> 00:11:53,160 And astonishingly, they return to exactly the same beach 133 00:11:53,160 --> 00:11:55,440 where they themselves hatched. 134 00:11:59,080 --> 00:12:01,480 How they find their way back after decades at sea 135 00:12:01,480 --> 00:12:04,560 is one of the mysteries that surround this species. 136 00:12:08,160 --> 00:12:11,400 But new research is suggesting that, just like the sharks, 137 00:12:11,400 --> 00:12:14,480 they navigate using the earth's magnetic field. 138 00:12:16,080 --> 00:12:18,440 They weigh up to 130 kilos, 139 00:12:18,440 --> 00:12:21,920 so hauling themselves up the beach is a gruelling task. 140 00:12:23,880 --> 00:12:26,200 But it's expected that 30,000 of them 141 00:12:26,200 --> 00:12:29,400 will come ashore to lay their eggs this year. 142 00:12:37,240 --> 00:12:40,920 With space in short supply, it's every female for herself. 143 00:12:53,320 --> 00:12:56,480 Once they've dug a hole, laying can begin. 144 00:13:01,200 --> 00:13:04,760 Each egg is roughly the size of a Ping-Pong ball. 145 00:13:04,760 --> 00:13:08,160 A female may lay up to 120 of them at a time 146 00:13:08,160 --> 00:13:12,440 and she's able to do this six times in a single breeding season. 147 00:13:20,640 --> 00:13:23,480 Once the eggs are laid, she buries them. 148 00:13:23,480 --> 00:13:27,680 For the next 60 days, the sand will conceal them from predators 149 00:13:27,680 --> 00:13:30,720 and protect them from the blistering sun. 150 00:13:46,080 --> 00:13:49,400 Keeping a very close eye on the turtles' progress 151 00:13:49,400 --> 00:13:54,200 is Dr Andy Dunstan of the Great Barrier Reef Marine Park Authority. 152 00:13:56,720 --> 00:14:01,120 Raine Island is the biggest green turtle rookery in the world. 153 00:14:01,120 --> 00:14:03,040 So it's incredibly important 154 00:14:03,040 --> 00:14:05,960 with the state of green turtles at the moment. 155 00:14:05,960 --> 00:14:09,840 Because of this, Raine is the most protected island on the reef. 156 00:14:14,960 --> 00:14:18,320 Only a handful of biologists are allowed to land here 157 00:14:18,320 --> 00:14:21,520 and Andy and his team have done so for very good reason. 158 00:14:27,320 --> 00:14:30,160 A huge number of turtles are certainly coming ashore 159 00:14:30,160 --> 00:14:32,080 to lay their eggs on the island, 160 00:14:32,080 --> 00:14:35,680 but the team's observations have revealed a worrying trend. 161 00:14:38,440 --> 00:14:42,120 The number of young hatchlings surviving incubation in the sand 162 00:14:42,120 --> 00:14:44,920 has dropped to just 20%. 163 00:14:44,920 --> 00:14:46,960 It's a serious cause for concern. 164 00:14:49,280 --> 00:14:51,320 The hatchlings we're seeing coming out 165 00:14:51,320 --> 00:14:54,120 are nowhere near the numbers that they should be. 166 00:14:54,120 --> 00:14:57,040 The nests, when we dig them up, 167 00:14:57,040 --> 00:15:01,840 have got really low levels of successful eggs hatching. 168 00:15:03,040 --> 00:15:05,960 And that is happening because of the very substance 169 00:15:05,960 --> 00:15:10,720 that makes this island so suitable for nest-building in the first place. 170 00:15:10,720 --> 00:15:13,880 Raine Island's a sand island. They move. 171 00:15:13,880 --> 00:15:17,040 But specifically for the green turtles here, 172 00:15:17,040 --> 00:15:22,040 the nesting area has become lower, so what we're seeing now 173 00:15:22,040 --> 00:15:27,600 that we never saw 30 years ago is inundation of tidal waters. 174 00:15:29,440 --> 00:15:33,680 This means that at high tide, the island is being flooded from below 175 00:15:33,680 --> 00:15:36,960 and the developing turtle eggs are being drowned. 176 00:15:38,640 --> 00:15:43,200 75% of the beach-nesting area is not suitable. 177 00:15:44,840 --> 00:15:47,120 Because turtles take a long time to mature, 178 00:15:47,120 --> 00:15:51,920 we expect to see a crash in those adult turtle numbers in the future. 179 00:15:51,920 --> 00:15:56,400 If we do something about hatchling success and nesting success now, 180 00:15:56,400 --> 00:15:58,320 we should see that recover again. 181 00:16:00,000 --> 00:16:03,880 Last year, Andy and his team made an ambitious plan. 182 00:16:07,440 --> 00:16:10,840 In a trial sector, they have raised the turtles nesting area 183 00:16:10,840 --> 00:16:13,640 by one and a half metres. 184 00:16:13,640 --> 00:16:16,160 They hope this will keep the developing eggs 185 00:16:16,160 --> 00:16:19,800 clear of the tidal waters and out of harm's way. 186 00:16:26,120 --> 00:16:28,800 Two long months after the egg laying began, 187 00:16:28,800 --> 00:16:31,560 the team returns to see if their plan is working. 188 00:16:36,160 --> 00:16:37,760 Under the cover of darkness, 189 00:16:37,760 --> 00:16:42,080 the first of the evening's hatchlings start to emerge. 190 00:16:45,480 --> 00:16:47,440 They started to push their way up 191 00:16:47,440 --> 00:16:50,280 through the sand about two days earlier. 192 00:16:57,440 --> 00:17:01,160 Now comes the moment that Andy and his team have been waiting for. 193 00:17:11,760 --> 00:17:16,040 A shallow trench helps to delay the new arrivals temporarily 194 00:17:16,040 --> 00:17:17,880 and allow the team to count them. 195 00:17:25,000 --> 00:17:27,680 So far, the signs are very encouraging. 196 00:17:27,680 --> 00:17:30,640 And as the night wears on, it gets better and better. 197 00:17:33,320 --> 00:17:37,240 This is looking great. We're getting much better nesting success, 198 00:17:37,240 --> 00:17:39,400 much better hatching success, 199 00:17:39,400 --> 00:17:42,920 the turtles are nesting right across the whole area 200 00:17:42,920 --> 00:17:45,200 and not disturbing each other so much. 201 00:17:45,200 --> 00:17:47,600 And those clutches which are underneath the sand 202 00:17:47,600 --> 00:17:49,800 are hatching much more successfully. 203 00:17:51,880 --> 00:17:55,560 It's confirmation that Andy and his team have found the right way 204 00:17:55,560 --> 00:17:57,760 to restore this vital breeding area. 205 00:18:01,600 --> 00:18:06,000 But for the young hatchlings, the trials of life have only just begun. 206 00:18:07,960 --> 00:18:12,680 Each new arrival will have to make a perilous dash to reach the ocean. 207 00:18:16,840 --> 00:18:18,240 Now they're on their own. 208 00:18:18,240 --> 00:18:21,120 Andy and his team must not interfere at this stage. 209 00:18:23,800 --> 00:18:26,800 Inevitably, the tiny, defenceless hatchlings 210 00:18:26,800 --> 00:18:28,800 attract scores of predators. 211 00:18:28,800 --> 00:18:31,000 SQUAWKING 212 00:18:32,040 --> 00:18:34,360 Terns and herons patrol the beach. 213 00:18:45,800 --> 00:18:49,080 And in the shallows, reef sharks lie in wait. 214 00:19:42,760 --> 00:19:44,720 Great numbers are lost, 215 00:19:44,720 --> 00:19:49,480 but enough will make it to the ocean to ensure the species' survival. 216 00:20:00,360 --> 00:20:03,240 As the young turtles leave the reef, 217 00:20:03,240 --> 00:20:07,240 they get a helping hand from the ocean currents. 218 00:20:07,240 --> 00:20:12,440 Swept out into the open ocean and there, they face new hazards. 219 00:20:12,440 --> 00:20:15,760 If they survive, they will eventually return 220 00:20:15,760 --> 00:20:19,280 to the very same beaches where they hatched. 221 00:20:22,160 --> 00:20:25,560 Remote islands like Raine are hugely important 222 00:20:25,560 --> 00:20:27,920 to both turtles and birds 223 00:20:27,920 --> 00:20:30,360 that come to the reef to lay their eggs. 224 00:20:33,080 --> 00:20:37,840 There are 900 isolated islands on the Great Barrier from which to choose 225 00:20:37,840 --> 00:20:40,880 and there's a habitat to suit every visitor. 226 00:20:43,720 --> 00:20:46,400 Turtles need sandy beaches 227 00:20:46,400 --> 00:20:48,880 and many birds need trees. 228 00:20:51,680 --> 00:20:55,440 'The Alucia is taking us to one of these wooded islands 229 00:20:55,440 --> 00:20:58,000 'near the southern end of the Great Barrier.' 230 00:21:00,160 --> 00:21:04,120 Almost 1,000 miles south of Raine is Heron Island. 231 00:21:04,120 --> 00:21:05,720 And every year, it attracts 232 00:21:05,720 --> 00:21:08,760 thousands of birds seeking somewhere safe to nest. 233 00:21:12,000 --> 00:21:15,520 The island is surrounded by fragile coral reef. 234 00:21:15,520 --> 00:21:20,000 So to reach the shore, I'm leaving the Alucia anchored in deeper water. 235 00:21:29,920 --> 00:21:31,560 FAINT BIRDSONG 236 00:21:38,320 --> 00:21:42,120 The warm waters of the Barrier Reef are full of fish. 237 00:21:42,120 --> 00:21:44,800 Full of food, as far as birds are concerned. 238 00:21:44,800 --> 00:21:50,160 There are immense numbers of seabirds throughout the year on the reef. 239 00:21:50,160 --> 00:21:54,200 But the moment comes in the year when, in fact, a bird has to lay. 240 00:21:54,200 --> 00:21:57,960 And to do that, it has to go onto land. 241 00:21:57,960 --> 00:22:02,280 And the number of sites where they can build a nest are very limited. 242 00:22:02,280 --> 00:22:06,000 So they will put up with a great deal of crowding 243 00:22:06,000 --> 00:22:10,800 and even with intruders, like myself, without deserting their nest. 244 00:22:14,400 --> 00:22:16,280 Hello. 245 00:22:17,640 --> 00:22:20,720 'Noddies are very protective parents. 246 00:22:20,720 --> 00:22:24,320 'Very little deters them from their chick-rearing duties.' 247 00:22:30,920 --> 00:22:33,200 Over one-and-a-half million birds 248 00:22:33,200 --> 00:22:36,440 come to the Great Barrier's islands every year to breed. 249 00:22:39,560 --> 00:22:43,600 To see one of the most intriguing, you'll have to wait until after dark. 250 00:22:53,960 --> 00:22:55,440 WAILING 251 00:22:56,800 --> 00:23:00,640 'The first indication that this secretive character has arrived 252 00:23:00,640 --> 00:23:03,320 'is its rather unusual song.' 253 00:23:03,320 --> 00:23:05,480 WAILING 254 00:23:10,840 --> 00:23:13,600 The old sailors used to call it the ghost bird 255 00:23:13,600 --> 00:23:16,360 because of its extraordinary call. 256 00:23:16,360 --> 00:23:19,800 More properly known as the wedge-tailed shearwater. 257 00:23:19,800 --> 00:23:21,880 WAILING 258 00:23:29,160 --> 00:23:34,040 'The birds' haunting calls guide me to their breeding grounds.' 259 00:23:34,040 --> 00:23:36,600 WAILING 260 00:23:51,160 --> 00:23:55,640 These are true seafaring birds. Out at sea when they're feeding, 261 00:23:55,640 --> 00:23:58,640 they are very expert at flying just above the surface, 262 00:23:58,640 --> 00:24:01,840 or indeed swimming on the surface, catching their fish. 263 00:24:01,840 --> 00:24:04,000 But when they come into land, well, 264 00:24:04,000 --> 00:24:06,680 they have to come in in the dark, for a start. 265 00:24:06,680 --> 00:24:09,440 And their landing is sometimes not very expert. 266 00:24:12,680 --> 00:24:14,720 Night-vision cameras probably give us 267 00:24:14,720 --> 00:24:18,360 better pictures of their landing ground than they seem to have. 268 00:24:33,440 --> 00:24:36,520 Their legs with which they paddle over the surface of the sea 269 00:24:36,520 --> 00:24:41,040 are placed far back on their body, and that makes them clumsy walkers. 270 00:24:44,120 --> 00:24:46,040 These birds have travelled 271 00:24:46,040 --> 00:24:48,080 an extraordinary 4,000 miles to get here. 272 00:24:52,360 --> 00:24:54,560 After spending months feeding at sea, 273 00:24:54,560 --> 00:24:56,680 they've had to come to land in order to breed. 274 00:24:59,440 --> 00:25:01,600 Once paired, they're devoted couples 275 00:25:01,600 --> 00:25:04,880 and both male and female share the tasks of parenthood. 276 00:25:09,800 --> 00:25:11,760 Even though there are trees here, 277 00:25:11,760 --> 00:25:15,080 the shearwaters prefer to make their nests underground. 278 00:25:21,000 --> 00:25:24,440 At the bottom of the nest hole, their three-week-old chick 279 00:25:24,440 --> 00:25:27,000 is waiting for its next meal. 280 00:25:30,160 --> 00:25:32,000 TWEETING 281 00:25:35,120 --> 00:25:37,840 Being a shearwater parent is a demanding job. 282 00:25:40,280 --> 00:25:42,880 Their young requires constant feeding. 283 00:25:44,280 --> 00:25:45,960 It consumes so much food 284 00:25:45,960 --> 00:25:49,600 that eventually, it'll outweigh its own parents. 285 00:25:52,560 --> 00:25:57,320 But its demands compel the adults to continually fly out to sea 286 00:25:57,320 --> 00:25:59,400 and come back again with more food. 287 00:26:01,360 --> 00:26:05,200 And their takeoffs are often just as clumsy as their landings. 288 00:26:37,000 --> 00:26:39,160 Fortunately for their nestlings, 289 00:26:39,160 --> 00:26:41,960 there's no shortage of fish in the summer months. 290 00:26:43,760 --> 00:26:47,360 And scientists have only just discovered why that is. 291 00:26:54,240 --> 00:26:57,560 In the waters just beyond Heron Island, 292 00:26:57,560 --> 00:27:01,920 there's a rich, swirling current known as the Capricorn Eddy. 293 00:27:06,360 --> 00:27:10,760 As it spins clockwise, it pulls up cool waters from below, 294 00:27:10,760 --> 00:27:15,600 which bring rich nutrients to the surface. 295 00:27:15,600 --> 00:27:21,040 That fuels the growth of huge blooms of tiny marine creatures, plankton, 296 00:27:21,040 --> 00:27:23,960 the foundation of the entire marine food web. 297 00:27:25,840 --> 00:27:29,840 So this part of the reef is particularly rich with fish. 298 00:27:29,840 --> 00:27:32,560 Vital food for the hungry young. 299 00:27:37,320 --> 00:27:40,280 By choosing Heron Island as a nesting ground, 300 00:27:40,280 --> 00:27:44,040 the birds can give their nestlings the best possible start in life. 301 00:27:49,760 --> 00:27:52,440 When I first came to the Barrier Reef, 302 00:27:52,440 --> 00:27:55,400 we knew very little about these seasonal visitors. 303 00:27:57,000 --> 00:27:59,920 We could only speculate as to why they came here 304 00:27:59,920 --> 00:28:02,080 and where they came from. 305 00:28:04,640 --> 00:28:08,320 Today, new research is enabling us to understand more clearly 306 00:28:08,320 --> 00:28:13,800 why, every year, particular species come to specific locations to breed. 307 00:28:15,920 --> 00:28:17,800 But there are still large animals 308 00:28:17,800 --> 00:28:21,880 whose movements remain something of a mystery. 309 00:28:21,880 --> 00:28:25,240 Manta rays are the nomads of the reef. 310 00:28:25,240 --> 00:28:27,520 They're huge creatures. 311 00:28:27,520 --> 00:28:31,120 They can measure 15 feet, five metres across 312 00:28:31,120 --> 00:28:34,680 and weigh almost one-and-a-half tonnes. 313 00:28:34,680 --> 00:28:37,720 They come to the reef to feed on plankton, 314 00:28:37,720 --> 00:28:40,320 but they also use it as a sanctuary, 315 00:28:40,320 --> 00:28:43,440 where they can breed, or get a good clean. 316 00:28:47,160 --> 00:28:51,440 Many make their way to the waters that surround Lady Elliot Island 317 00:28:51,440 --> 00:28:53,840 on the southern end of the Great Barrier. 318 00:28:58,160 --> 00:29:01,680 For the visiting manta rays, this is a paradise. 319 00:29:01,680 --> 00:29:05,120 A place where these ocean giants can get a little pampering. 320 00:29:13,120 --> 00:29:16,080 These are the beauty salons of the reef. 321 00:29:16,080 --> 00:29:19,040 And they're often run by a pair of wrasse, 322 00:29:19,040 --> 00:29:22,160 small fish with a stripe running from head to tail. 323 00:29:27,680 --> 00:29:29,160 These committed cleaners 324 00:29:29,160 --> 00:29:31,960 regularly tend to a host of different creatures. 325 00:29:36,440 --> 00:29:38,280 They provide a vital service, 326 00:29:38,280 --> 00:29:42,120 removing the dead skin and parasites from outside 327 00:29:42,120 --> 00:29:45,280 and even inside their clients' bodies. 328 00:29:48,760 --> 00:29:50,880 It may seem like a thankless task, 329 00:29:50,880 --> 00:29:53,920 but the cleaner fish are getting a good meal out of it. 330 00:29:58,320 --> 00:30:02,160 And of all their clients, the manta rays are their star customers. 331 00:30:09,000 --> 00:30:12,040 When business is brisk, they patiently wait in line. 332 00:30:18,920 --> 00:30:20,680 Like planes in a holding pattern, 333 00:30:20,680 --> 00:30:23,640 they circle until an opportunity arrives. 334 00:30:32,840 --> 00:30:36,960 When it's their turn, the manta rays surrender themselves completely. 335 00:30:40,000 --> 00:30:43,080 Within seconds, a host of fish rush to their side. 336 00:30:44,480 --> 00:30:47,800 Manta rays are rarely left waiting for long. 337 00:30:56,240 --> 00:31:00,480 Each fish tends to a very specific part of the manta's body. 338 00:31:01,840 --> 00:31:04,480 And the cleaning can last a full hour. 339 00:31:09,760 --> 00:31:12,880 For the most part, the service is second to none. 340 00:31:12,880 --> 00:31:16,440 But occasionally, the cleaners can get a little carried away. 341 00:31:22,720 --> 00:31:26,600 A female wrasse has taken a nibble out of the manta ray's flesh. 342 00:31:27,720 --> 00:31:31,680 She's broken the rules, and there's a price to pay. 343 00:31:31,680 --> 00:31:34,440 Her partner chases after her. 344 00:31:34,440 --> 00:31:37,680 It's the cleaner fish equivalent of a stern telling off. 345 00:31:40,560 --> 00:31:44,440 Scientists believe males do this to protect future business. 346 00:31:46,640 --> 00:31:50,480 If the bite is a one-off, the manta ray will return. 347 00:31:50,480 --> 00:31:53,680 But research has shown that if it happens too often, 348 00:31:53,680 --> 00:31:57,160 the pair risks driving regular visitors away. 349 00:32:02,120 --> 00:32:04,400 Fortunately, it seems her indiscretion 350 00:32:04,400 --> 00:32:06,560 hasn't put their client off. 351 00:32:06,560 --> 00:32:10,440 The manta is back and business has resumed. 352 00:32:14,400 --> 00:32:17,040 Manta rays come here in such numbers 353 00:32:17,040 --> 00:32:21,280 that the island has become the focal point for a research project. 354 00:32:27,120 --> 00:32:30,600 Dr Kathy Townsend has been tracking the manta's movements 355 00:32:30,600 --> 00:32:32,960 and numbers for the last seven years. 356 00:32:43,560 --> 00:32:46,440 Lady Elliot Island is like the centre of the universe 357 00:32:46,440 --> 00:32:49,720 for manta rays on the east coast of Australia. 358 00:32:49,720 --> 00:32:51,480 We come back time and time again 359 00:32:51,480 --> 00:32:54,720 because we get large aggregations of these animals. 360 00:32:55,880 --> 00:32:58,200 We are doing several things with the manta rays. 361 00:32:58,200 --> 00:33:00,160 First of all, we're trying to understand 362 00:33:00,160 --> 00:33:02,000 how many there are potentially here. 363 00:33:02,000 --> 00:33:04,800 And to do that, you need to do some sort of tagging. 364 00:33:07,040 --> 00:33:11,520 This is a key part of Kathy's work in tracking these gentle ocean giants. 365 00:33:11,520 --> 00:33:14,880 And the team has already attached acoustic tags 366 00:33:14,880 --> 00:33:18,200 to a large number of study animals. 367 00:33:18,200 --> 00:33:22,560 We have six acoustic listening stations around Lady Elliot Island. 368 00:33:22,560 --> 00:33:24,320 And as an animal goes past, 369 00:33:24,320 --> 00:33:27,880 within a 500-metre radius of this listening station, 370 00:33:27,880 --> 00:33:31,240 it picks up the tag and we know that that animal's been past. 371 00:33:34,720 --> 00:33:37,920 That has revealed that many of the mantas have travelled 372 00:33:37,920 --> 00:33:41,560 hundreds of miles up the eastern coast of Australia to get here. 373 00:33:45,200 --> 00:33:47,760 One of the lovely things about working with manta rays 374 00:33:47,760 --> 00:33:49,440 is that they're extremely curious 375 00:33:49,440 --> 00:33:52,680 and they'll seek you out to come and see what you're up to. 376 00:34:07,200 --> 00:34:09,200 It's really unusual behaviour. 377 00:34:09,200 --> 00:34:11,120 Most sharks and rays have no interest 378 00:34:11,120 --> 00:34:13,960 in having any interaction with people whatsoever. 379 00:34:13,960 --> 00:34:17,840 But for whatever reason, manta rays are highly-curious creatures 380 00:34:17,840 --> 00:34:20,160 and will basically look at you eye to eye. 381 00:34:22,520 --> 00:34:26,920 The manta ray's inquisitive nature works to Kathy's advantage. 382 00:34:26,920 --> 00:34:31,280 It means she can get close enough to photograph them for identification. 383 00:34:32,920 --> 00:34:37,000 And one of the best places to do that is at the cleaning stations. 384 00:34:49,480 --> 00:34:51,560 We need to get in underneath the animal 385 00:34:51,560 --> 00:34:54,080 and take a photograph from below. 386 00:34:54,080 --> 00:34:58,000 Each individual has a very unique spot pattern 387 00:34:58,000 --> 00:35:01,920 that stays with them from birth until they pass away. 388 00:35:01,920 --> 00:35:03,520 That's very handy for us. 389 00:35:08,760 --> 00:35:11,440 When Project Manta began seven years ago, 390 00:35:11,440 --> 00:35:15,960 it was thought that fewer than 40 individuals came to Lady Elliot. 391 00:35:15,960 --> 00:35:20,160 Today, Kathy and her team have catalogued more than 800. 392 00:35:23,560 --> 00:35:26,120 I think manta ray research is quite important 393 00:35:26,120 --> 00:35:29,000 because first of all, this is a very large-bodied animal 394 00:35:29,000 --> 00:35:32,360 that very little information is known about. 395 00:35:32,360 --> 00:35:34,080 Various places around the world, 396 00:35:34,080 --> 00:35:37,040 the manta ray populations have declined dramatically, 397 00:35:37,040 --> 00:35:40,760 to the point where they've now been listed as threatened 398 00:35:40,760 --> 00:35:42,880 on that list for endangered species. 399 00:35:45,280 --> 00:35:49,440 For the visiting mantas, the Great Barrier Reef really is a sanctuary. 400 00:35:51,360 --> 00:35:54,200 Here, this ocean giant is properly protected. 401 00:35:56,080 --> 00:35:57,560 While they're in these waters, 402 00:35:57,560 --> 00:36:01,200 they're safe from the fisheries that threaten them elsewhere. 403 00:36:05,000 --> 00:36:08,280 Manta rays aren't the only animals that find refuge here. 404 00:36:09,800 --> 00:36:13,520 The Great Barrier protects its visitors in many different ways. 405 00:36:20,120 --> 00:36:24,520 'That becomes clear when you look at the reef from above. 406 00:36:27,840 --> 00:36:29,800 'This part of tropical Australia 407 00:36:29,800 --> 00:36:33,440 'lies right in the path of regular seasonal cyclones. 408 00:36:33,440 --> 00:36:36,840 'And from up here, you can see what valuable protection 409 00:36:36,840 --> 00:36:38,560 'the reef can provide.' 410 00:36:40,880 --> 00:36:42,920 This tangle of limestone walls 411 00:36:42,920 --> 00:36:47,000 acts as a barrier against the open ocean. 412 00:36:47,000 --> 00:36:51,480 Between it and the land, the waters are warm and shallow. 413 00:36:51,480 --> 00:36:54,400 An ideal haven for visitors. 414 00:36:56,360 --> 00:36:59,280 In the winter, many creatures come up here to escape 415 00:36:59,280 --> 00:37:01,880 the freezing temperatures of the Antarctic. 416 00:37:09,320 --> 00:37:12,600 Among them are humpback whales. 417 00:37:32,880 --> 00:37:34,320 WHALE SONG 418 00:37:34,320 --> 00:37:36,000 Weighing up to 40 tonnes, 419 00:37:36,000 --> 00:37:39,160 they're the largest of the Great Barrier Reef's visitors 420 00:37:39,160 --> 00:37:42,440 and they have also travelled great distances to get here. 421 00:37:52,440 --> 00:37:57,040 Each year, they make an exhausting 6,000-mile-round trip 422 00:37:57,040 --> 00:37:59,400 from the Antarctic and back again. 423 00:38:04,280 --> 00:38:06,720 Incredibly, 20,000 of them do it. 424 00:38:13,440 --> 00:38:15,840 Here, in these warm and sheltered waters, 425 00:38:15,840 --> 00:38:18,640 they give birth and suckle their newborn calves. 426 00:38:23,720 --> 00:38:26,160 But in fact, we still know very little 427 00:38:26,160 --> 00:38:28,560 about what else they do once they get here. 428 00:38:33,320 --> 00:38:36,400 Where exactly do they go during their time on the reef? 429 00:38:40,560 --> 00:38:42,040 The fact that we don't know 430 00:38:42,040 --> 00:38:45,680 is a reminder of just how vast this great wilderness is. 431 00:38:49,040 --> 00:38:52,280 But not all whales make the task of tracking them so hard. 432 00:38:55,200 --> 00:38:58,480 In fact, there's one species which does quite the opposite. 433 00:38:58,480 --> 00:39:02,400 Incredibly, this whale actively seeks out the scientists 434 00:39:02,400 --> 00:39:04,560 who are trying to study them. 435 00:39:15,240 --> 00:39:19,920 This endearing little character is the dwarf minke whale. 436 00:39:22,640 --> 00:39:25,120 And surprisingly, it was only first observed 437 00:39:25,120 --> 00:39:27,400 here on the reef in the 1980s. 438 00:39:30,720 --> 00:39:35,000 But since then, we've realised that they're extremely faithful visitors, 439 00:39:35,000 --> 00:39:38,800 returning every year to the same location on the northern reef. 440 00:39:47,240 --> 00:39:50,080 Why they do so, we still don't understand. 441 00:39:52,640 --> 00:39:55,440 But research is beginning to reveal their story. 442 00:39:57,960 --> 00:40:00,760 Dr Alistair Birtles knows more about 443 00:40:00,760 --> 00:40:04,440 this still-mysterious species than anyone else. 444 00:40:04,440 --> 00:40:07,960 So he's affectionately known as Professor Minke. 445 00:40:10,600 --> 00:40:15,080 To observe the whales in detail, he has to step into their world. 446 00:40:17,280 --> 00:40:20,160 The very first time I got in the water, um... 447 00:40:20,160 --> 00:40:26,320 was with a degree of apprehension, great excitement. 448 00:40:26,320 --> 00:40:30,440 Um...I don't think I'd ever been in the water with a whale before. 449 00:40:30,440 --> 00:40:34,840 And the first thing you see is the white shoulder, um... 450 00:40:34,840 --> 00:40:38,840 and then the rest of the grey animal emerges around it. 451 00:40:38,840 --> 00:40:42,200 It's very special being in the water 452 00:40:42,200 --> 00:40:45,080 with these animals in their own environment. 453 00:40:45,080 --> 00:40:48,000 It's an extraordinary experience. 454 00:40:51,280 --> 00:40:54,080 Every year, Alistair and his research team 455 00:40:54,080 --> 00:40:56,840 return to spend time with the dwarf minkes. 456 00:40:59,360 --> 00:41:03,400 These annual reunions are beginning to reveal more and more 457 00:41:03,400 --> 00:41:05,520 about these fascinating creatures. 458 00:41:08,000 --> 00:41:12,160 It seems that they spend most of their lives out in the open ocean, 459 00:41:12,160 --> 00:41:15,120 leading what's thought to be a solitary existence. 460 00:41:18,000 --> 00:41:21,600 But surprisingly, when they get here, on the Great Reef, 461 00:41:21,600 --> 00:41:23,800 they actively seek human contact. 462 00:41:28,000 --> 00:41:30,480 Behaviour like this happens nowhere else. 463 00:41:32,360 --> 00:41:35,640 It is entirely the whale's curiosity that brings them in. 464 00:41:35,640 --> 00:41:38,760 I think we're a rather strange object. 465 00:41:38,760 --> 00:41:41,520 We're a visitor into their world. 466 00:41:41,520 --> 00:41:45,200 I'm sure they're wondering exactly what we are 467 00:41:45,200 --> 00:41:48,960 and what we're doing, just as we're wondering what they're doing. 468 00:41:51,480 --> 00:41:54,760 For Birtles, there are many familiar faces here. 469 00:41:54,760 --> 00:41:57,840 And he has his own pet names for regular visitors. 470 00:42:00,040 --> 00:42:04,360 Bento, I have seen every year for the last eight years. 471 00:42:05,720 --> 00:42:07,520 She has a bent-over dorsal fin 472 00:42:07,520 --> 00:42:12,200 from I think where she was fairly savagely mauled by a shark. 473 00:42:12,200 --> 00:42:15,440 And last year's encounter was a particularly special one 474 00:42:15,440 --> 00:42:17,640 because she had a calf with her. 475 00:42:17,640 --> 00:42:21,640 That's the first time in eight years that we've known she had a calf. 476 00:42:21,640 --> 00:42:25,920 And it was a little male and it was a very special interaction. 477 00:42:34,640 --> 00:42:37,320 What Birtles and his team want to discover 478 00:42:37,320 --> 00:42:39,720 is why this usually-solitary whale 479 00:42:39,720 --> 00:42:43,320 suddenly becomes so extremely social when it gets here. 480 00:42:45,040 --> 00:42:47,240 There are a number of clues. 481 00:42:47,240 --> 00:42:51,080 We know they're not feeding. We've never seen them feed. 482 00:42:51,080 --> 00:42:53,680 But we see a lot of socialising going on. 483 00:42:55,040 --> 00:42:58,560 Minkes were known as the silent whale when we began working on them 484 00:42:58,560 --> 00:43:01,160 and there were no recordings of dwarf minkes. 485 00:43:02,800 --> 00:43:06,760 It went on for quite a while before we heard any sounds. 486 00:43:13,480 --> 00:43:15,800 And then there's an extraordinary sound they make 487 00:43:15,800 --> 00:43:19,040 which the researcher who labelled it 488 00:43:19,040 --> 00:43:22,120 called it the Star Wars sound. 489 00:43:22,120 --> 00:43:25,320 I thought it was a little more like Beethoven's Fifth 490 00:43:25,320 --> 00:43:29,640 because it's got a triple beat and then a long shwang 491 00:43:29,640 --> 00:43:31,600 that he thought was the lightsaber. 492 00:43:31,600 --> 00:43:34,080 So it goes, da-da-da-dang. 493 00:43:35,200 --> 00:43:37,120 WHALE SONG 494 00:43:38,400 --> 00:43:39,640 WHALE SONG 495 00:43:39,640 --> 00:43:43,760 When you hear it underwater, it kind of reverberates through your chest. 496 00:43:43,760 --> 00:43:45,840 It's a very powerful sound. 497 00:43:45,840 --> 00:43:47,880 WHALE SONG 498 00:43:51,440 --> 00:43:53,960 The song is only produced by males 499 00:43:53,960 --> 00:43:56,880 and it's thought to be related to courtship. 500 00:43:56,880 --> 00:43:58,960 WHALE SONG 501 00:43:58,960 --> 00:44:01,920 Curiously, two thirds of the individuals 502 00:44:01,920 --> 00:44:04,480 Alistair encounters are adolescents. 503 00:44:06,280 --> 00:44:10,680 One theory is that the whales are coming here to find potential mates 504 00:44:10,680 --> 00:44:14,240 and learn the dos and don'ts of minke social behaviour. 505 00:44:16,360 --> 00:44:18,240 Though Birtles' team has amassed 506 00:44:18,240 --> 00:44:20,440 a huge amount of data over the decades, 507 00:44:20,440 --> 00:44:23,520 there is clearly still much to learn. 508 00:44:24,920 --> 00:44:29,680 Where, for example, do the whales go after this social gathering? 509 00:44:32,760 --> 00:44:35,280 But now, a brand-new tagging programme 510 00:44:35,280 --> 00:44:38,040 is shedding more light on their annual journey. 511 00:44:41,720 --> 00:44:44,440 Tagging is not easy. 512 00:44:47,720 --> 00:44:49,720 The diver has to get into position, 513 00:44:49,720 --> 00:44:52,800 choose his mark and then discharge the tag, 514 00:44:52,800 --> 00:44:54,960 all on a single breath. 515 00:44:57,880 --> 00:45:00,040 There's no room for error. 516 00:45:22,000 --> 00:45:23,600 After initially taking fright, 517 00:45:23,600 --> 00:45:26,800 the whale comes back to the dive boat. 518 00:45:26,800 --> 00:45:30,160 It seems that minkes aren't too distressed by the process. 519 00:45:34,360 --> 00:45:37,000 The tracking data the team is now collecting 520 00:45:37,000 --> 00:45:41,080 may reveal the piece of the puzzle that, until now, has been missing. 521 00:45:41,080 --> 00:45:44,720 So for 20 years, we've been studying what the whales do 522 00:45:44,720 --> 00:45:47,200 in this area of the Great Barrier Reef. 523 00:45:47,200 --> 00:45:50,000 We know they're only here for a few weeks 524 00:45:50,000 --> 00:45:52,000 and we had no idea where they went 525 00:45:52,000 --> 00:45:54,320 when they left the Great Barrier Reef 526 00:45:54,320 --> 00:45:56,360 at the end of their sojourn here. 527 00:45:58,440 --> 00:46:00,440 It really is an extraordinary journey 528 00:46:00,440 --> 00:46:02,640 that we now know that they make. 529 00:46:02,640 --> 00:46:06,200 Spot, the young male that was the first ever minke 530 00:46:06,200 --> 00:46:10,760 to have a satellite tag attached in 2013, 531 00:46:10,760 --> 00:46:16,560 he travelled over 7,000 kilometres deep into the Subantarctic. 532 00:46:16,560 --> 00:46:22,080 That's an extraordinary journey for what is a little whale, to make. 533 00:46:22,080 --> 00:46:26,040 The tagging tells us where the whales are travelling fast 534 00:46:26,040 --> 00:46:28,920 and where they're spending extra time. 535 00:46:28,920 --> 00:46:32,600 There's a few places along the east coast of Australia and Bass Strait 536 00:46:32,600 --> 00:46:36,600 where they may spend one, two or even three weeks of time 537 00:46:36,600 --> 00:46:39,680 milling around, probably feeding. 538 00:46:39,680 --> 00:46:43,520 So we may have discovered some of these feeding sites 539 00:46:43,520 --> 00:46:46,680 for the dwarf minke whale along their migration path. 540 00:46:48,480 --> 00:46:50,120 For Birtles, it's not just about 541 00:46:50,120 --> 00:46:53,080 solving the mystery of where the whales go. 542 00:46:53,080 --> 00:46:56,560 I am worried about them when they leave the reef. 543 00:46:56,560 --> 00:46:58,800 The dwarf minkes are well protected 544 00:46:58,800 --> 00:47:00,760 when they're in the Great Barrier Reef, 545 00:47:00,760 --> 00:47:06,120 but when they leave there, they face many threats and dangers 546 00:47:06,120 --> 00:47:09,840 and they have to cross major shipping channels. 547 00:47:09,840 --> 00:47:13,800 There are all sorts of threats from fishing. 548 00:47:13,800 --> 00:47:18,600 I mean, if commercial whaling is resumed in the Southern Ocean, 549 00:47:18,600 --> 00:47:22,360 which is the objective of the research that's going on 550 00:47:22,360 --> 00:47:26,320 at the moment from the Japanese, then these whales would be at risk. 551 00:47:31,480 --> 00:47:35,000 It's hoped the new tagging programme may help us understand 552 00:47:35,000 --> 00:47:39,240 how best to protect these whales throughout the entire year. 553 00:47:41,960 --> 00:47:46,040 By venturing into their underwater world, Birtles and his team 554 00:47:46,040 --> 00:47:49,280 are discovering valuable new facts about these whales. 555 00:47:50,880 --> 00:47:53,160 But their research has only just begun. 556 00:47:57,400 --> 00:48:01,280 The more we learn about the creatures that come here, the more we discover 557 00:48:01,280 --> 00:48:04,920 just how important the Great Barrier Reef is to their survival. 558 00:48:08,160 --> 00:48:09,840 The reef is immense. 559 00:48:11,320 --> 00:48:15,400 Millions of visitors travel great distances to get to it. 560 00:48:15,400 --> 00:48:19,800 And there, find food, shelter and an opportunity to meet a mate. 561 00:48:23,040 --> 00:48:26,960 A global community of animals rely on this great wilderness. 562 00:48:29,480 --> 00:48:31,840 And that makes it one of the most important 563 00:48:31,840 --> 00:48:34,320 and influential habitats on the planet. 564 00:48:39,000 --> 00:48:42,120 Next time, in our final programme... 565 00:48:43,400 --> 00:48:47,120 ..we'll investigate the dangers that now threaten the reef 566 00:48:47,120 --> 00:48:48,640 and its inhabitants. 567 00:48:52,640 --> 00:48:54,480 THUNDERCLAP 568 00:48:54,480 --> 00:48:56,560 We'll meet the extraordinary people 569 00:48:56,560 --> 00:48:58,680 who are doing everything in their power 570 00:48:58,680 --> 00:49:00,960 to protect this marine paradise. 571 00:49:00,960 --> 00:49:05,000 It is one of the most magnificent ecosystems on the planet. 572 00:49:05,000 --> 00:49:07,320 What's really quite shocking is that we may lose it 573 00:49:07,320 --> 00:49:10,080 before we truly understand it. 574 00:49:10,080 --> 00:49:13,480 And we'll attempt our most ambitious dive yet. 575 00:49:13,480 --> 00:49:18,560 Nobody has ever dived as deep as this before on the Great Barrier Reef. 576 00:49:20,640 --> 00:49:25,320 As we search for new species and try to predict what the future holds 577 00:49:25,320 --> 00:49:27,800 for the Great Barrier. 578 00:49:45,840 --> 00:49:48,480 For this episode, one of our underwater teams 579 00:49:48,480 --> 00:49:51,240 travelled to Lady Elliot Island in the south. 580 00:49:55,840 --> 00:49:58,360 Here, the reef's majestic manta rays 581 00:49:58,360 --> 00:50:02,800 are stripped of dead skin and parasites by tiny cleaner fish. 582 00:50:05,280 --> 00:50:08,080 The crew's goal was to film a rare behaviour. 583 00:50:09,600 --> 00:50:12,760 The moment when the cleaner fish breaks the rules 584 00:50:12,760 --> 00:50:15,480 and bites a manta ray's flesh. 585 00:50:17,160 --> 00:50:19,440 To film the story, the team worked closely 586 00:50:19,440 --> 00:50:21,960 with marine biologist, Dr Kathy Townsend. 587 00:50:25,360 --> 00:50:29,640 Manta rays will often seek out and spend time with divers, 588 00:50:29,640 --> 00:50:33,560 which, of course, makes them amazing animals to be in the water with. 589 00:50:34,880 --> 00:50:38,560 Manta rays may be inquisitive, but they can easily be spooked. 590 00:50:38,560 --> 00:50:41,320 The challenge for cameraman, Mike Pitts, 591 00:50:41,320 --> 00:50:44,400 was to make himself as unobtrusive as possible. 592 00:50:46,520 --> 00:50:48,520 You are bulky and clumsy, 593 00:50:48,520 --> 00:50:50,680 you've got large cameras, lights. 594 00:50:50,680 --> 00:50:55,680 So what you don't want to do is to obstruct the manta ray. 595 00:50:55,680 --> 00:50:59,400 The manta ray might get disturbed and it'll just swim off. 596 00:50:59,400 --> 00:51:01,640 I generally keep as low as possible. 597 00:51:01,640 --> 00:51:04,440 So your profile sort of matches in with the reef. 598 00:51:04,440 --> 00:51:06,600 And so what you notice after a while is 599 00:51:06,600 --> 00:51:09,920 the manta rays will come closer and closer and closer to you. 600 00:51:09,920 --> 00:51:14,800 And I can literally... I feel them brushing over my head as they go. 601 00:51:14,800 --> 00:51:17,760 While the team's objective was to film the cleaning station, 602 00:51:17,760 --> 00:51:19,480 on the fourth day of the shoot, 603 00:51:19,480 --> 00:51:22,360 they were treated to something truly unexpected. 604 00:51:25,320 --> 00:51:27,200 We were close to the end of the dive 605 00:51:27,200 --> 00:51:30,040 and we hadn't really seen anything for about 58 minutes 606 00:51:30,040 --> 00:51:32,200 and then I spotted a pair. 607 00:51:35,240 --> 00:51:39,040 I saw Kathy and suddenly she zoomed off and we followed. 608 00:51:39,040 --> 00:51:42,720 And I could see out in the distance, there was a male above a female 609 00:51:42,720 --> 00:51:45,920 and he was following her every move 610 00:51:45,920 --> 00:51:48,120 as she moved through the water. 611 00:51:48,120 --> 00:51:49,880 Kathy got really excited. 612 00:51:52,240 --> 00:51:54,720 They were undergoing behaviour I'd never seen before. 613 00:51:54,720 --> 00:51:56,840 I'd seen various types of courtship behaviour 614 00:51:56,840 --> 00:51:59,000 that involves having trains, 615 00:51:59,000 --> 00:52:02,280 where there's a female at the front followed by several males. 616 00:52:02,280 --> 00:52:06,280 What was happening between these two was really quite unique. 617 00:52:06,280 --> 00:52:09,440 The male was obviously trying to court her, 618 00:52:09,440 --> 00:52:11,960 but in a very unusual way. 619 00:52:11,960 --> 00:52:14,000 He was taking his front cephalic lobes 620 00:52:14,000 --> 00:52:16,560 and he was actually stroking her on her back. 621 00:52:18,640 --> 00:52:20,840 Obviously trying to entice her to say, 622 00:52:20,840 --> 00:52:23,120 "Listen, you know, I'm the one for you". 623 00:52:24,240 --> 00:52:27,080 She, on the other hand, was not quite enthusiastic 624 00:52:27,080 --> 00:52:30,640 about the attention that he was bestowing upon her. 625 00:52:31,680 --> 00:52:34,640 And all of sudden, she'd just fling up into the air to shake him off 626 00:52:34,640 --> 00:52:36,760 and say, "No, it's not ready for that yet". 627 00:52:36,760 --> 00:52:38,840 And then she would settle back down. 628 00:52:47,360 --> 00:52:49,840 I knew it was something very special because, 629 00:52:49,840 --> 00:52:52,920 seeing Kathy's reactions to what was going on, 630 00:52:52,920 --> 00:52:56,280 she was so excited about it, she was bubbling. 631 00:52:58,680 --> 00:53:01,120 You could wait a lifetime to see something like that. 632 00:53:01,120 --> 00:53:02,800 Just a very rare event. 633 00:53:05,400 --> 00:53:08,800 In the far north, another wildlife crew had their sights set 634 00:53:08,800 --> 00:53:12,560 on filming a very special seasonal visitor. 635 00:53:12,560 --> 00:53:16,160 In winter, dwarf minke whales come to the reef 636 00:53:16,160 --> 00:53:18,560 for just a few short weeks. 637 00:53:20,120 --> 00:53:22,160 Wildlife cameraman, Dean Miller, 638 00:53:22,160 --> 00:53:25,240 has been documenting these whales for 15 years. 639 00:53:27,200 --> 00:53:29,600 It's a little bit unnerving sometimes jumping in 640 00:53:29,600 --> 00:53:33,080 and seeing a seven-tonne, seven-metre animal 641 00:53:33,080 --> 00:53:35,040 come out from the gloom. 642 00:53:35,040 --> 00:53:37,760 And you're hoping that it is going to be the whale 643 00:53:37,760 --> 00:53:40,040 and not something with a few more teeth. 644 00:53:41,360 --> 00:53:43,520 Every animal presents a very different challenge 645 00:53:43,520 --> 00:53:45,600 when it comes to filming behaviour, 646 00:53:45,600 --> 00:53:49,360 but over the years, Dean has learned the minke tricks of the trade. 647 00:53:52,040 --> 00:53:54,680 It's sometimes a game of cat and mouse, in a way. 648 00:53:54,680 --> 00:53:57,520 Because if you're not looking, they tend to come a lot closer. 649 00:53:57,520 --> 00:54:00,320 So if I can see a whale approaching in the distance 650 00:54:00,320 --> 00:54:02,960 and I know it's going to be a good approach this time, 651 00:54:02,960 --> 00:54:05,120 I'll purposely hold off and turn my dome around 652 00:54:05,120 --> 00:54:08,240 and actually see in the reflection of the dome the whale coming to me 653 00:54:08,240 --> 00:54:11,400 and then, when I think it's probably about five to six metres away, 654 00:54:11,400 --> 00:54:14,400 I'll turn around and get the best shot I've had all day. 655 00:54:14,400 --> 00:54:16,280 They sneak up on you. 656 00:54:17,760 --> 00:54:19,720 Over time, they build up that confidence 657 00:54:19,720 --> 00:54:23,640 and they just really, really try to edge much closer 658 00:54:23,640 --> 00:54:25,560 each and every time and get a good look. 659 00:54:27,840 --> 00:54:30,840 I do have other tricks, as well. I'll sing through my snorkel. 660 00:54:30,840 --> 00:54:32,680 HUMMING 661 00:54:34,480 --> 00:54:37,160 You can be in the water for seven, eight hours a day 662 00:54:37,160 --> 00:54:39,760 and you might only get two of these passes for that whole day. 663 00:54:39,760 --> 00:54:43,000 And when they happen, they're just mind-blowing. 664 00:54:43,000 --> 00:54:44,800 You've got this big, big animal. 665 00:54:44,800 --> 00:54:47,360 I mean, it's the size of a minibus, coming to look at you. 666 00:54:50,320 --> 00:54:53,440 You can get out at the end of a day and just have the biggest smile. 667 00:54:53,440 --> 00:54:55,720 I've just watched the sunset from in the water. 668 00:54:55,720 --> 00:54:59,600 A whale nearly touched me. It just doesn't get any better. 669 00:55:04,920 --> 00:55:06,640 'While our underwater crews 670 00:55:06,640 --> 00:55:09,320 'were rewarded with spectacular interactions, 671 00:55:09,320 --> 00:55:12,240 'on Heron Island, I had the opportunity 672 00:55:12,240 --> 00:55:14,360 'to meet one of my favourite visitors.' 673 00:55:17,040 --> 00:55:18,520 The noddy. 674 00:55:20,000 --> 00:55:23,880 The birds' relaxed nature and attachment to their nests 675 00:55:23,880 --> 00:55:27,160 meant we could tell their story without disturbing them. 676 00:55:28,200 --> 00:55:30,000 Without deserting their nest. 677 00:55:33,560 --> 00:55:34,920 Hello. 678 00:55:34,920 --> 00:55:37,240 But when cameraman, Mike Pitts returns 679 00:55:37,240 --> 00:55:39,680 to film the hatchlings three months later, 680 00:55:39,680 --> 00:55:42,680 disaster hits the island on his first night. 681 00:55:44,200 --> 00:55:45,920 THUNDERCLAP 682 00:55:50,440 --> 00:55:52,760 WIND GUSTS 683 00:56:00,000 --> 00:56:03,720 The following morning, Mike discovers that the storm has destroyed 684 00:56:03,720 --> 00:56:05,920 the very spot where I had filmed. 685 00:56:08,000 --> 00:56:10,200 It was shattered. It was like a warzone. 686 00:56:10,200 --> 00:56:13,360 You think of these idyllic, tropical islands 687 00:56:13,360 --> 00:56:15,560 and you couldn't be further from the truth. 688 00:56:22,320 --> 00:56:23,880 Are you still rolling? 689 00:56:23,880 --> 00:56:26,400 You can see that many of the trees are down. 690 00:56:26,400 --> 00:56:29,120 And it's brought down the chicks with them and the nests. 691 00:56:29,120 --> 00:56:31,880 Eggs are smashed, chicks are dying. 692 00:56:31,880 --> 00:56:33,960 And the chicks that have survived 693 00:56:33,960 --> 00:56:36,440 are now on these trunks and branches 694 00:56:36,440 --> 00:56:38,280 and on the ground of the forest itself, 695 00:56:38,280 --> 00:56:40,440 hoping for their parent birds 696 00:56:40,440 --> 00:56:42,640 to find them and bring the food they need. 697 00:56:42,640 --> 00:56:44,440 But the parent birds are so confused 698 00:56:44,440 --> 00:56:46,520 because so many of the trees are gone. 699 00:56:46,520 --> 00:56:50,360 It's very disheartening to see it, and, er...it's a real sad sight. 700 00:56:54,200 --> 00:56:57,480 I'd never seen the aftermath of such a strong storm. 701 00:56:58,480 --> 00:57:01,920 But, of course, your emotions always get the better of you. 702 00:57:05,880 --> 00:57:10,040 You still see survivors, just sitting on the nest, 703 00:57:10,040 --> 00:57:12,680 protecting the egg or the chick. 704 00:57:12,680 --> 00:57:15,520 It really is quite amazing, their resilience. 705 00:57:16,920 --> 00:57:20,360 It puts the whole reef into a context whereby 706 00:57:20,360 --> 00:57:23,240 you're following the rhythms of life. 707 00:57:23,240 --> 00:57:26,040 We were there to record it and film it 708 00:57:26,040 --> 00:57:28,320 and that's part of the Great Reef story.