1 00:00:38,080 --> 00:00:39,200 The open ocean. 2 00:00:41,280 --> 00:00:45,560 It covers more than half the surface of our planet. 3 00:00:45,560 --> 00:00:49,280 Yet, for the most part, it's a watery desert, 4 00:00:49,280 --> 00:00:51,320 empty of life. 5 00:00:54,920 --> 00:00:59,400 Hunters here spend their lives in a constant search 6 00:00:59,400 --> 00:01:02,080 for scarce and elusive prey. 7 00:01:16,960 --> 00:01:20,960 Remarkably, this seemingly barren wilderness 8 00:01:20,960 --> 00:01:24,560 is home to the largest hunter of them all... 9 00:01:29,360 --> 00:01:31,080 ..the blue whale. 10 00:01:40,880 --> 00:01:43,120 Weighing 200 tonnes 11 00:01:43,120 --> 00:01:45,280 and 30 metres long, 12 00:01:45,280 --> 00:01:48,800 these are the biggest animals ever to have lived. 13 00:02:02,560 --> 00:02:05,000 Despite their immense size, 14 00:02:05,000 --> 00:02:08,560 blue whales are one of the most streamlined 15 00:02:08,560 --> 00:02:11,640 and energy-efficient of all swimmers. 16 00:02:22,400 --> 00:02:25,800 Their food is so scarce and widely spread 17 00:02:25,800 --> 00:02:30,200 that blue whales must journey across whole oceans 18 00:02:30,200 --> 00:02:33,400 just to find a single meal. 19 00:02:40,240 --> 00:02:45,400 They can travel over 100 miles a day for weeks at a time. 20 00:02:58,600 --> 00:03:03,200 The ocean's largest animal feeds on one of its smallest. 21 00:03:05,240 --> 00:03:08,680 Krill - small shrimp-like crustaceans. 22 00:03:16,160 --> 00:03:20,080 Opening its gigantic mouth takes so much effort 23 00:03:20,080 --> 00:03:21,440 that they only do so 24 00:03:21,440 --> 00:03:24,560 when the swarms of krill are rich and concentrated. 25 00:03:31,280 --> 00:03:34,240 The krill here is too scattered - 26 00:03:34,240 --> 00:03:36,520 not even worth slowing down for. 27 00:04:09,360 --> 00:04:13,200 This blue whale's lonely search for food 28 00:04:13,200 --> 00:04:14,920 must go on. 29 00:04:21,120 --> 00:04:26,040 Out here, feeding opportunities are always few and far between. 30 00:04:27,920 --> 00:04:29,360 And they never last long. 31 00:04:36,000 --> 00:04:38,080 Prey is devoured within minutes. 32 00:04:48,440 --> 00:04:49,800 When it's all over, 33 00:04:49,800 --> 00:04:53,000 the hunters must resume their endless search. 34 00:04:57,000 --> 00:04:58,760 Frigatebirds - 35 00:04:58,760 --> 00:05:00,880 the pirates of the high seas. 36 00:05:02,760 --> 00:05:06,000 Soaring effortlessly on the gentle trade winds, 37 00:05:06,000 --> 00:05:09,520 they can scan vast tracts of ocean for food. 38 00:05:12,200 --> 00:05:14,440 Frigates must be so lightweight 39 00:05:14,440 --> 00:05:16,840 that they can't afford the heavy oils 40 00:05:16,840 --> 00:05:20,040 that waterproof the plumage of other sea birds. 41 00:05:20,040 --> 00:05:23,000 So getting wet would be lethal. 42 00:05:24,920 --> 00:05:29,280 This may seem an impossible limitation for a seafaring hunter. 43 00:05:29,280 --> 00:05:31,880 But frigatebirds overcome this handicap 44 00:05:31,880 --> 00:05:33,360 with help from others. 45 00:05:42,240 --> 00:05:43,440 Dorado. 46 00:05:45,240 --> 00:05:48,800 One of the fastest and most voracious of ocean predators. 47 00:05:52,040 --> 00:05:55,240 They patrol close to the surface, searching for prey. 48 00:06:05,520 --> 00:06:09,640 Little fish try to hide amidst the undulating swell of the ocean - 49 00:06:09,640 --> 00:06:11,040 the only cover there is. 50 00:06:18,560 --> 00:06:20,600 It's a game of hide and seek 51 00:06:20,600 --> 00:06:22,640 played out amongst the waves. 52 00:06:26,920 --> 00:06:28,320 Their cover blown... 53 00:06:30,560 --> 00:06:32,240 ..escape seems impossible. 54 00:06:41,400 --> 00:06:44,520 But these particular fish have a unique ability. 55 00:06:59,200 --> 00:07:01,280 They're flying fish. 56 00:07:23,800 --> 00:07:26,120 With an extra thrust from their tails, 57 00:07:26,120 --> 00:07:28,560 the flying fish get airborne once more. 58 00:07:37,320 --> 00:07:38,760 With a good wind, 59 00:07:38,760 --> 00:07:40,960 they can glide for hundreds of metres. 60 00:07:58,720 --> 00:08:01,000 But this is just what the frigatebirds 61 00:08:01,000 --> 00:08:02,360 have been waiting for. 62 00:08:06,880 --> 00:08:08,800 When frigates join the hunt, 63 00:08:08,800 --> 00:08:12,560 the flying fish are literally caught between the devil... 64 00:08:14,760 --> 00:08:16,560 ..and the deep blue sea. 65 00:08:36,400 --> 00:08:38,800 If the flying fish get too much lift 66 00:08:38,800 --> 00:08:41,080 they become easy prey for the frigates. 67 00:08:56,200 --> 00:08:59,280 If they dive to evade attack from above... 68 00:09:03,920 --> 00:09:06,680 ..they could fall into the mouths of the dorado. 69 00:09:48,000 --> 00:09:49,880 With the help of the dorado, 70 00:09:49,880 --> 00:09:54,280 the wily frigatebird has become a flying fish specialist... 71 00:09:55,560 --> 00:09:58,280 ..and without getting a single feather wet. 72 00:10:04,640 --> 00:10:07,840 Not all open-ocean hunters are able to travel 73 00:10:07,840 --> 00:10:10,440 in search of their food. 74 00:10:10,440 --> 00:10:15,720 Some have no choice but wait for a meal to come to them. 75 00:10:19,640 --> 00:10:24,040 A mat of sargassum weed drifts in the middle of the Atlantic. 76 00:10:30,600 --> 00:10:34,920 Sargassum is the only seaweed to live entirely at the surface. 77 00:10:36,080 --> 00:10:38,240 It never attaches to the sea floor. 78 00:10:42,840 --> 00:10:45,120 This floating tangle of fronds 79 00:10:45,120 --> 00:10:49,520 is home to a surprising open-ocean predator - 80 00:10:49,520 --> 00:10:51,720 the sargassum fish. 81 00:10:55,600 --> 00:10:58,560 Every part of his body mimics the weed. 82 00:11:01,720 --> 00:11:04,640 His fins are more suited to walking than swimming. 83 00:11:06,680 --> 00:11:09,240 In fact, he can barely swim at all. 84 00:11:11,840 --> 00:11:16,480 He will spend his entire life marooned on this weedy raft. 85 00:11:24,800 --> 00:11:28,080 This sargassum fish must lie in wait 86 00:11:28,080 --> 00:11:31,000 for those seeking shelter amongst the weed. 87 00:11:44,000 --> 00:11:47,200 Unfortunately his mat is empty for now. 88 00:11:49,760 --> 00:11:52,160 But at least he's not wasting valuable energy 89 00:11:52,160 --> 00:11:53,600 searching for food. 90 00:12:00,000 --> 00:12:02,240 In the featureless ocean, 91 00:12:02,240 --> 00:12:06,040 these mats are much-sought-after sanctuary for juvenile fish. 92 00:12:23,640 --> 00:12:25,920 At last - 93 00:12:25,920 --> 00:12:29,120 his first opportunity for weeks. 94 00:12:36,080 --> 00:12:37,560 He must get closer. 95 00:12:38,680 --> 00:12:43,400 He can only strike when he's within a few centimetres of his prey. 96 00:12:53,640 --> 00:12:56,320 Trusting his perfect camouflage, 97 00:12:56,320 --> 00:12:58,280 he hides in the weed. 98 00:13:04,200 --> 00:13:05,480 Patience. 99 00:13:10,920 --> 00:13:12,680 Still not close enough. 100 00:13:24,520 --> 00:13:27,080 Hunger is clearly getting the better of him. 101 00:13:40,320 --> 00:13:42,120 Surely this time. 102 00:13:46,040 --> 00:13:47,280 Blown it. 103 00:13:49,920 --> 00:13:53,120 It may be weeks before he gets another chance. 104 00:14:08,120 --> 00:14:10,680 The open ocean is so vast 105 00:14:10,680 --> 00:14:13,760 that some hunters can only find enough prey 106 00:14:13,760 --> 00:14:15,920 by searching as a team. 107 00:14:30,040 --> 00:14:34,320 Dolphins live in highly sophisticated social groups. 108 00:14:43,440 --> 00:14:44,840 Working together, 109 00:14:44,840 --> 00:14:47,440 they can cover a huge area of ocean. 110 00:14:52,240 --> 00:14:54,720 These are spinner dolphins. 111 00:14:57,400 --> 00:15:00,880 Why they make these twisting leaps is still debatable. 112 00:15:00,880 --> 00:15:03,560 Perhaps it's a form of communication... 113 00:15:07,560 --> 00:15:09,600 ..or perhaps it's just fun. 114 00:15:11,840 --> 00:15:14,280 Small groups sometimes come together, 115 00:15:14,280 --> 00:15:17,760 forming superpods 5,000 strong. 116 00:15:24,320 --> 00:15:26,720 And these are on the hunt. 117 00:15:34,440 --> 00:15:36,120 SONAR CLICKS 118 00:15:36,120 --> 00:15:39,640 Spinners are the most vocal of all the dolphins. 119 00:15:39,640 --> 00:15:41,560 CLICKING AND CRACKLING 120 00:15:42,840 --> 00:15:47,360 They use echolocation, a kind of sonar, to find their prey. 121 00:15:48,960 --> 00:15:52,280 Each hunter sends out a series of clicks 122 00:15:52,280 --> 00:15:55,520 and then listens for returning echoes... 123 00:15:58,520 --> 00:16:01,040 ..allowing them to scan for distant prey, 124 00:16:01,040 --> 00:16:02,680 hundreds of metres away. 125 00:16:02,680 --> 00:16:05,200 CLICKS CONTINUE 126 00:16:08,480 --> 00:16:12,760 The superpod spreads out into a wide hunting line, 127 00:16:12,760 --> 00:16:14,160 up to a mile across... 128 00:16:15,880 --> 00:16:18,440 ..producing a wall of sound. 129 00:16:18,440 --> 00:16:21,360 CONSTANT CLICKING 130 00:16:30,360 --> 00:16:33,320 They're searching for their favourite prey. 131 00:16:36,480 --> 00:16:38,160 Lanternfish. 132 00:16:38,160 --> 00:16:41,320 They are the most numerous fish on the planet. 133 00:16:43,680 --> 00:16:46,560 But these small fish spend most of their time 134 00:16:46,560 --> 00:16:51,160 down in the deep ocean, way beyond the reach of dolphins. 135 00:16:51,160 --> 00:16:54,240 It's only when they come up to the surface to feed 136 00:16:54,240 --> 00:16:55,800 that they become prey. 137 00:16:59,840 --> 00:17:01,320 Once they've found a shoal, 138 00:17:01,320 --> 00:17:04,400 the dolphins use their sonar in a different way. 139 00:17:04,400 --> 00:17:06,720 SONAR BLASTS 140 00:17:06,720 --> 00:17:09,440 They stun the fish with loud blasts, 141 00:17:09,440 --> 00:17:11,400 then simply gather them up. 142 00:17:26,760 --> 00:17:30,680 As they feed, the dolphins work the underside of the shoal 143 00:17:30,680 --> 00:17:34,400 to stop their prey from escaping back into the safety of the deep. 144 00:17:55,240 --> 00:17:56,600 Within a few minutes, 145 00:17:56,600 --> 00:17:59,840 all that's left is a shower of scales 146 00:17:59,840 --> 00:18:03,000 drifting downwards to the ocean depths. 147 00:18:15,200 --> 00:18:17,680 The deep ocean is by far 148 00:18:17,680 --> 00:18:20,880 the largest habitat for life on Earth... 149 00:18:22,600 --> 00:18:26,200 ..and home to some of the most bizarre hunters of all. 150 00:18:29,920 --> 00:18:34,360 Down here, food is much scarcer than at the surface, 151 00:18:34,360 --> 00:18:39,640 so deep-sea predators must do all they can to save precious energy. 152 00:18:48,960 --> 00:18:52,440 Waiting patiently, a viperfish. 153 00:18:52,440 --> 00:18:55,720 Special light-producing organs on its head 154 00:18:55,720 --> 00:18:58,680 entice prey towards fearsome teeth. 155 00:19:03,920 --> 00:19:07,960 Strange yet deadly jelly hunters also live here. 156 00:19:10,440 --> 00:19:12,320 Most simply drift, 157 00:19:12,320 --> 00:19:16,120 trailing tentacles loaded with lethal stings. 158 00:19:21,760 --> 00:19:25,040 Others, propelled by lines of beating hairs, 159 00:19:25,040 --> 00:19:28,120 glide gently through the darkness. 160 00:19:43,360 --> 00:19:44,720 Beroe - 161 00:19:44,720 --> 00:19:47,760 the top deep-sea jelly predator. 162 00:19:54,120 --> 00:19:56,760 They actively hunt other jellies... 163 00:19:59,280 --> 00:20:01,000 ..like this ctenophore. 164 00:20:15,760 --> 00:20:18,760 To grasp its gelatinous prey, 165 00:20:18,760 --> 00:20:23,360 Beroe has special teeth-like spikes in its mouth. 166 00:20:37,680 --> 00:20:42,480 Many deep-sea hunters just hang in the abyss, 167 00:20:42,480 --> 00:20:44,960 saving their energy, 168 00:20:44,960 --> 00:20:47,880 luring their prey to come to them. 169 00:20:53,560 --> 00:20:55,200 Chiroteuthis. 170 00:20:56,440 --> 00:21:01,840 This deep-sea squid fishes for prey using long, sticky tentacles. 171 00:21:03,040 --> 00:21:05,160 Each has a glowing lure, 172 00:21:05,160 --> 00:21:07,480 pulsing to attract passing prey. 173 00:21:24,440 --> 00:21:29,800 A gentle twitch adds to the temptation. 174 00:21:56,760 --> 00:22:01,600 Down here in the darkness, this meal is a rare bonanza. 175 00:22:10,000 --> 00:22:15,200 The open ocean may be a vast blue desert, 176 00:22:15,200 --> 00:22:19,280 but like all deserts, it has oases. 177 00:22:27,240 --> 00:22:30,800 Scattered widely across this endless space 178 00:22:30,800 --> 00:22:33,200 are thousands of small islands. 179 00:22:37,960 --> 00:22:40,760 These are the summits of underwater mountains, 180 00:22:40,760 --> 00:22:43,880 which rise up from the sea floor many miles below. 181 00:22:51,560 --> 00:22:55,840 The seamounts deflect deep-ocean currents upwards, 182 00:22:55,840 --> 00:22:58,760 forcing nutrient-laden water to the surface. 183 00:23:06,600 --> 00:23:10,720 A busy oasis in the emptiness of the big blue. 184 00:23:31,720 --> 00:23:35,680 For potential prey, there's plenty of shelter amongst the coral... 185 00:23:38,000 --> 00:23:41,560 ..and in the caves that are hidden beneath the reef itself. 186 00:23:52,600 --> 00:23:55,080 Small fish take refuge here, 187 00:23:55,080 --> 00:23:57,600 out of the reach of most of their predators. 188 00:24:00,120 --> 00:24:01,680 But not all. 189 00:24:03,400 --> 00:24:05,160 Lionfish. 190 00:24:10,840 --> 00:24:12,800 They're not built for speed - 191 00:24:12,800 --> 00:24:16,560 success here depends on delicate manoeuvring. 192 00:24:18,800 --> 00:24:22,440 Their strategy is to hide in plain sight, 193 00:24:22,440 --> 00:24:25,920 lulling their prey into a false sense of security. 194 00:24:33,840 --> 00:24:36,760 The lionfish's stripes are visually confusing, 195 00:24:36,760 --> 00:24:40,120 making it difficult for their prey to judge how close it is. 196 00:24:54,360 --> 00:25:01,480 Using its extravagant fins to hide slow and deliberate tail movements, 197 00:25:01,480 --> 00:25:03,200 it edges ever closer. 198 00:25:07,760 --> 00:25:10,240 It must get to within a few centimetres, 199 00:25:10,240 --> 00:25:12,400 close enough for a sudden strike. 200 00:25:25,320 --> 00:25:26,600 Got one. 201 00:25:37,920 --> 00:25:41,560 The deep-water currents that sustain so many residents 202 00:25:41,560 --> 00:25:44,560 also attract visitors to these oases. 203 00:25:49,880 --> 00:25:51,680 Silky sharks. 204 00:25:56,560 --> 00:25:59,720 They journey hundreds of miles between seamounts, 205 00:25:59,720 --> 00:26:03,000 using them as gathering places in the featureless ocean. 206 00:26:09,800 --> 00:26:11,680 They're joined by hammerheads. 207 00:26:16,920 --> 00:26:19,360 Both these sharks constantly travel 208 00:26:19,360 --> 00:26:22,880 between the Galapagos and other isolated seamounts 209 00:26:22,880 --> 00:26:24,320 in the Eastern Pacific. 210 00:26:30,160 --> 00:26:33,960 No-one knows for sure why they gather in such numbers, 211 00:26:33,960 --> 00:26:38,080 but some certainly come to these oases in search of food. 212 00:26:46,200 --> 00:26:50,560 A school of resident silversides cloaks the seamount. 213 00:26:52,160 --> 00:26:54,760 If these little fish stay close to the coral, 214 00:26:54,760 --> 00:26:57,080 the sharks won't be able to get at them. 215 00:27:17,440 --> 00:27:21,640 Other, more agile visitors are attracted by the potential feast. 216 00:27:24,800 --> 00:27:25,920 Striped bonito... 217 00:27:28,200 --> 00:27:29,880 ..and golden trevalley. 218 00:27:36,440 --> 00:27:40,440 To get a meal, they'll need to drive their prey up and away from the reef 219 00:27:40,440 --> 00:27:41,680 into open water. 220 00:27:45,080 --> 00:27:48,640 As long as the silversides stick close to the sea floor, 221 00:27:48,640 --> 00:27:50,720 they should evade their predators. 222 00:28:12,640 --> 00:28:16,720 This time, the frustrated hunters will have to search elsewhere - 223 00:28:16,720 --> 00:28:20,560 there's never an easy meal in the open ocean. 224 00:28:33,680 --> 00:28:37,120 The Southern Ocean encircling Antarctica. 225 00:28:42,120 --> 00:28:44,200 The wildest seas on our planet. 226 00:28:47,040 --> 00:28:52,160 Here, it's the storm-tossed waters that bring nutrients to the surface, 227 00:28:52,160 --> 00:28:54,840 creating isolated patches of richness. 228 00:28:58,040 --> 00:28:59,880 Far from the calm tropics, 229 00:28:59,880 --> 00:29:03,400 this weather-beaten ocean is home to the albatross. 230 00:29:12,320 --> 00:29:16,120 Black-browed albatross are the same size as frigatebirds 231 00:29:16,120 --> 00:29:18,400 but three times as heavy, 232 00:29:18,400 --> 00:29:21,760 and so they need a totally different flying technique. 233 00:29:26,640 --> 00:29:30,960 Albatross have the longest wingspan of any bird, 234 00:29:30,960 --> 00:29:33,800 and that enables them to exploit the power 235 00:29:33,800 --> 00:29:35,520 of the Southern Ocean winds. 236 00:29:40,000 --> 00:29:42,280 First, they glide into the wind, 237 00:29:42,280 --> 00:29:45,120 harnessing its energy to give them lift. 238 00:29:48,320 --> 00:29:52,200 Then they turn and descend downwind, picking up speed. 239 00:29:59,920 --> 00:30:02,800 Soaring on wind fronts like this, 240 00:30:02,800 --> 00:30:04,480 an albatross can travel 241 00:30:04,480 --> 00:30:07,320 hundreds of miles of ocean in a day... 242 00:30:09,040 --> 00:30:11,120 ..barely beating its wings. 243 00:30:16,760 --> 00:30:19,520 They often spend weeks at sea, 244 00:30:19,520 --> 00:30:23,440 searching for prey without ever returning to land. 245 00:30:35,200 --> 00:30:40,520 Food at last - a patch of krill close to the surface. 246 00:30:43,520 --> 00:30:45,920 Because the winds are so strong here, 247 00:30:45,920 --> 00:30:48,240 albatrosses can afford the extra weight 248 00:30:48,240 --> 00:30:50,760 of waterproofing oils on their feathers. 249 00:30:53,360 --> 00:30:55,760 They can duck-dive to no more than a metre, 250 00:30:55,760 --> 00:30:59,160 so they rely on the churning of the Southern Ocean 251 00:30:59,160 --> 00:31:01,080 to bring their prey up into range. 252 00:31:31,360 --> 00:31:34,920 Like all birds, albatross have to breed on land, 253 00:31:34,920 --> 00:31:38,200 but suitable islands are so few in the South Atlantic 254 00:31:38,200 --> 00:31:40,520 that most are heavily overcrowded. 255 00:31:45,800 --> 00:31:50,720 Steeple Jason - one of the largest albatross colonies in the world. 256 00:31:50,720 --> 00:31:53,920 ALBATROSS SQUAWK 257 00:31:58,240 --> 00:32:02,520 Nearly half a million come back here each year to raise their young. 258 00:32:11,400 --> 00:32:13,760 Adults share parenting duties, 259 00:32:13,760 --> 00:32:16,600 returning every few days to feed their chick. 260 00:32:25,880 --> 00:32:31,000 Feeding done, it's time to head out to sea. 261 00:32:37,120 --> 00:32:40,320 They need to make their way to the edge of the packed colony 262 00:32:40,320 --> 00:32:42,920 where there's more room for takeoff. 263 00:32:42,920 --> 00:32:45,600 CHICK CRIES 264 00:32:45,600 --> 00:32:49,360 Albatross are so heavy that they can only get airborne 265 00:32:49,360 --> 00:32:51,760 in places where the wind is strong enough. 266 00:32:55,440 --> 00:32:57,360 Using a special runway... 267 00:33:00,200 --> 00:33:01,720 ..with a good headwind... 268 00:33:08,360 --> 00:33:09,400 ..she's off. 269 00:33:19,720 --> 00:33:24,040 From the air, the ocean may appear featureless, 270 00:33:24,040 --> 00:33:26,120 but beneath the surface, 271 00:33:26,120 --> 00:33:30,360 a network of powerful currents is constantly on the move. 272 00:33:33,080 --> 00:33:36,240 It's these currents, more than any other force, 273 00:33:36,240 --> 00:33:39,480 that determine the distribution of life out here. 274 00:33:42,360 --> 00:33:44,720 A whole community of ocean drifters 275 00:33:44,720 --> 00:33:47,640 hitches rides on these rivers in the sea. 276 00:33:50,440 --> 00:33:52,560 Pelagic red crabs. 277 00:34:03,320 --> 00:34:06,960 They've gathered to feed on tiny floating plants and animals, 278 00:34:06,960 --> 00:34:09,680 a bloom of plankton fuelled by the currents. 279 00:34:20,920 --> 00:34:24,320 Fine hairs on their legs slow their descent... 280 00:34:26,880 --> 00:34:29,440 ..and then, with a few flicks of the tail, 281 00:34:29,440 --> 00:34:32,600 they swim back up to continue feeding. 282 00:34:42,880 --> 00:34:45,680 The currents that carry these wandering crabs 283 00:34:45,680 --> 00:34:49,800 also serve as highways for the ocean's larger predators. 284 00:34:54,920 --> 00:34:56,480 Striped marlin. 285 00:35:01,880 --> 00:35:03,360 Beautifully streamlined, 286 00:35:03,360 --> 00:35:07,000 they can travel huge distances with minimum effort. 287 00:35:09,040 --> 00:35:12,720 These hunters patrol the boundaries between ocean currents, 288 00:35:12,720 --> 00:35:14,720 where their prey often gathers. 289 00:35:18,320 --> 00:35:21,360 Each predator has an incredible sense of smell, 290 00:35:21,360 --> 00:35:24,760 able to detect faint trails left by their prey. 291 00:35:29,840 --> 00:35:33,240 Somewhere out here is the big prize... 292 00:35:35,240 --> 00:35:37,840 ..and hunters of all kinds are looking for it. 293 00:35:55,160 --> 00:35:59,560 Great shoals of fish are attracted to a plankton bloom. 294 00:36:01,120 --> 00:36:04,520 A single school of sardines can be many miles long. 295 00:36:10,280 --> 00:36:15,120 The fish swim tightly together - there's safety in numbers. 296 00:36:19,760 --> 00:36:22,560 Their defence relies on coordination. 297 00:36:27,120 --> 00:36:30,320 When attacked, the sardines move as one. 298 00:36:39,720 --> 00:36:43,480 Each fish instantly matches the movements of its neighbour... 299 00:36:45,040 --> 00:36:48,040 ..and the whole shoal moves in synchrony. 300 00:36:55,200 --> 00:36:59,000 A lone sea lion can't keep up with their rapid reactions. 301 00:37:08,840 --> 00:37:11,440 Even when more sea lions arrive, 302 00:37:11,440 --> 00:37:15,840 they can't seem to break down the sardines' coordinated defences. 303 00:37:33,760 --> 00:37:37,320 With a shoal this big, the sea lions need to isolate 304 00:37:37,320 --> 00:37:39,760 a smaller, more manageable group of fish. 305 00:37:45,360 --> 00:37:49,760 But with so few predators, the fish still have the advantage. 306 00:37:55,200 --> 00:37:59,680 All the sea lions can do is keep the sardines at the surface 307 00:37:59,680 --> 00:38:01,680 and wait for others to join them. 308 00:38:11,120 --> 00:38:13,720 Tuna. 309 00:38:13,720 --> 00:38:16,680 Their arrival changes everything. 310 00:38:29,280 --> 00:38:31,280 Tuna attack from below, 311 00:38:31,280 --> 00:38:34,800 cutting off the sardines' escape route down to deeper water. 312 00:38:43,680 --> 00:38:47,120 Next to appear, shearwaters - 313 00:38:47,120 --> 00:38:51,440 excellent fliers, but also surprisingly agile underwater. 314 00:38:55,200 --> 00:38:58,440 With so many predators attacking from all sides, 315 00:38:58,440 --> 00:39:02,120 the advantage starts to shift away from the sardines. 316 00:39:22,720 --> 00:39:24,840 As the fish pack ever tighter, 317 00:39:24,840 --> 00:39:28,560 their shoaling strategy now makes it easier for the hunters. 318 00:39:53,600 --> 00:39:55,240 Copper sharks. 319 00:39:55,240 --> 00:39:58,640 They've scented blood in the water. 320 00:40:04,440 --> 00:40:08,480 Surprisingly, perhaps, the predators never attack one another. 321 00:40:08,480 --> 00:40:11,560 They work together to corral the ball of fish, 322 00:40:11,560 --> 00:40:14,320 taking turns to grab a mouthful. 323 00:40:23,840 --> 00:40:25,240 Common dolphins. 324 00:40:28,720 --> 00:40:30,760 As the shoal gets ever smaller, 325 00:40:30,760 --> 00:40:34,720 each sardine scrambles desperately to hide in the middle. 326 00:40:34,720 --> 00:40:37,360 But now, there's no escape. 327 00:40:56,440 --> 00:41:01,240 A Bryde's whale finishes off the feast - 328 00:41:01,240 --> 00:41:05,520 tonnes of sardines devoured in less than an hour. 329 00:41:17,040 --> 00:41:19,960 The predators melt away into the blue... 330 00:41:23,000 --> 00:41:25,960 ..going their separate ways once more. 331 00:41:36,320 --> 00:41:39,760 This blue whale is still searching for a meal 332 00:41:39,760 --> 00:41:42,240 to satisfy its giant hunger. 333 00:41:45,080 --> 00:41:46,600 Being so large, 334 00:41:46,600 --> 00:41:50,240 it must catch an average of four tonnes of food a day. 335 00:41:55,760 --> 00:41:59,360 But many days may pass without feeding at all. 336 00:42:04,840 --> 00:42:11,520 It is their great size that enables blue whales to travel the furthest, 337 00:42:11,520 --> 00:42:15,640 roaming every ocean from the tropics to the poles. 338 00:42:15,640 --> 00:42:17,640 BLUE WHALE SPOUTS 339 00:42:29,240 --> 00:42:32,320 Trapped against the surface by fish, 340 00:42:32,320 --> 00:42:34,640 a dense patch of krill. 341 00:42:39,480 --> 00:42:41,200 This blue has finally found 342 00:42:41,200 --> 00:42:44,440 what it's been searching for for so long. 343 00:42:46,480 --> 00:42:51,200 A meal big enough to make opening its massive mouth worthwhile. 344 00:42:56,040 --> 00:42:59,840 The krill swarm is hundreds of metres across 345 00:42:59,840 --> 00:43:01,440 and packed tight. 346 00:43:09,440 --> 00:43:12,360 The whale lines up on its prey, 347 00:43:12,360 --> 00:43:14,880 targeting the densest part of the shoal. 348 00:43:55,280 --> 00:43:59,880 It takes so much effort to swim with a fully extended throat 349 00:43:59,880 --> 00:44:03,240 that the whale virtually comes to a standstill. 350 00:44:16,520 --> 00:44:21,240 The whale uses its tongue to force the water out of its mouth, 351 00:44:21,240 --> 00:44:26,040 trapping the krill on plates of hairy bristles that line its jaw. 352 00:44:30,320 --> 00:44:33,600 But it takes time to sieve so much water. 353 00:44:36,640 --> 00:44:39,440 And that gives more nimble hunters their chance. 354 00:44:54,440 --> 00:44:58,000 Blue whales may not be as agile as other hunters, 355 00:44:58,000 --> 00:45:00,120 but they don't need to be. 356 00:45:02,920 --> 00:45:04,760 In one giant mouthful, 357 00:45:04,760 --> 00:45:07,800 they can swallow whole swarms of krill. 358 00:45:59,160 --> 00:46:02,120 No other predator is better suited 359 00:46:02,120 --> 00:46:07,320 to exploit the scattered riches that the open ocean can provide. 360 00:46:11,320 --> 00:46:14,600 The blue whale - 361 00:46:14,600 --> 00:46:18,640 the greatest hunter in all the world's oceans. 362 00:46:55,880 --> 00:46:59,760 The open ocean created many challenges for the Hunt team. 363 00:47:01,800 --> 00:47:05,680 But none came bigger than trying to film blue whales underwater. 364 00:47:07,840 --> 00:47:11,520 Achieving this was to turn into a two-year mission. 365 00:47:13,800 --> 00:47:16,560 The crew teamed up with John Calambokidis, 366 00:47:16,560 --> 00:47:19,120 the world's foremost blue whale scientist. 367 00:47:21,160 --> 00:47:25,240 John gets crucial information from these harmless tags. 368 00:47:27,720 --> 00:47:32,160 But he can only observe blue whales for the brief time they surface. 369 00:47:34,680 --> 00:47:37,200 Well, part of this research and part of the reason 370 00:47:37,200 --> 00:47:39,880 that, er, we're working with film-makers 371 00:47:39,880 --> 00:47:44,000 is it gives us an unique chance to get scientific information 372 00:47:44,000 --> 00:47:45,720 we wouldn't be able to otherwise. 373 00:47:45,720 --> 00:47:47,680 So we are doing this under our research permit 374 00:47:47,680 --> 00:47:50,640 to get an insight into what they're doing underwater - 375 00:47:50,640 --> 00:47:53,400 how they're diving, how they're swimming, how they're feeding. 376 00:47:56,240 --> 00:47:59,160 Pictures of blue whales are rare. 377 00:47:59,160 --> 00:48:01,800 They're the biggest animal ever to live on the planet, 378 00:48:01,800 --> 00:48:05,280 but there are only a few underwater pictures that exist today. 379 00:48:05,280 --> 00:48:07,200 A few where you can actually see the animal. 380 00:48:07,200 --> 00:48:10,880 First, they have to find a blue whale. 381 00:48:10,880 --> 00:48:13,080 Well, I always feel really embarrassed, you know, 382 00:48:13,080 --> 00:48:16,640 because how can you lose the biggest animal that's ever lived, you know? 383 00:48:16,640 --> 00:48:20,360 But...er, while the whale is big, the ocean is even bigger. 384 00:48:25,120 --> 00:48:26,720 Just over here. 385 00:48:28,160 --> 00:48:32,120 The team's success will depend on good water visibility. 386 00:48:34,680 --> 00:48:38,920 Too murky, and the whale literally disappears into the gloom. 387 00:48:43,640 --> 00:48:44,920 No shot. 388 00:48:46,760 --> 00:48:49,760 The first year was blighted by poor visibility 389 00:48:49,760 --> 00:48:51,680 and the shoot ended in failure. 390 00:48:56,200 --> 00:49:01,000 Year two, and the sea conditions are much better. 391 00:49:04,240 --> 00:49:06,120 Oh, here he is, right here. 392 00:49:06,120 --> 00:49:09,520 Blue whales only surface for two to three minutes at a time 393 00:49:09,520 --> 00:49:13,280 before diving for up to 15 minutes. 394 00:49:13,280 --> 00:49:16,800 It's a narrow window for everything to come together. 395 00:49:16,800 --> 00:49:18,960 There's a bit of tricky manoeuvring here for John. 396 00:49:18,960 --> 00:49:21,080 He's got to try and get the boat 397 00:49:21,080 --> 00:49:23,440 ahead of the whale but not in front of it. 398 00:49:27,560 --> 00:49:29,120 Then David has to swim out 399 00:49:29,120 --> 00:49:32,320 and hope the whale passes close enough to get a shot. 400 00:49:39,280 --> 00:49:41,160 It's too far. 401 00:49:41,160 --> 00:49:44,040 It's a little too far that time. 402 00:49:52,680 --> 00:49:55,440 This year, the water is exceptionally clear... 403 00:49:58,000 --> 00:50:01,440 ..but getting David in the right position still takes time. 404 00:50:03,720 --> 00:50:05,560 He went by, I definitely got a shot. 405 00:50:05,560 --> 00:50:06,960 It's not one of our best. 406 00:50:17,160 --> 00:50:18,240 Missed it. 407 00:50:21,400 --> 00:50:22,720 After weeks of effort, 408 00:50:22,720 --> 00:50:24,880 all the elements finally come together, 409 00:50:24,880 --> 00:50:27,840 giving David the chance of a lifetime. 410 00:50:30,680 --> 00:50:34,280 Like, I got down to about 25 feet. I knew that whale was out there. 411 00:50:34,280 --> 00:50:38,560 But, er...he just came out of the blue, right to me. 412 00:50:44,760 --> 00:50:47,720 I could see his eye, the details of his mouth, 413 00:50:47,720 --> 00:50:51,000 every scratch on his skin. 414 00:50:51,000 --> 00:50:53,920 And he cruised on by - it took forever. 415 00:50:53,920 --> 00:50:57,400 You know, they're so big - it just went by like a freight train. 416 00:51:02,080 --> 00:51:04,240 I saw his tail slide by. 417 00:51:04,240 --> 00:51:07,160 And he slipped back into the blue. 418 00:51:07,160 --> 00:51:09,360 It...it was awesome. 419 00:51:09,360 --> 00:51:12,720 That is awesome - I have never, of all my years of doing this, 420 00:51:12,720 --> 00:51:14,120 I've never got a shot like that. 421 00:51:14,120 --> 00:51:15,280 That was amazing. 422 00:51:16,640 --> 00:51:19,640 Images of blue whales underwater are so rare 423 00:51:19,640 --> 00:51:25,360 that this shot of one simply swimming by is a major success. 424 00:51:25,360 --> 00:51:28,160 But the crew need more. 425 00:51:28,160 --> 00:51:30,280 This series is all about hunting, 426 00:51:30,280 --> 00:51:33,920 and so, nice though it is to have that shot, to make a sequence, 427 00:51:33,920 --> 00:51:37,880 we've got to get shots of blue whales eating krill. 428 00:51:37,880 --> 00:51:39,480 And what we've got to wait for 429 00:51:39,480 --> 00:51:41,680 is when the krill actually comes to the surface. 430 00:51:41,680 --> 00:51:44,080 It might happen once, maybe twice a month. 431 00:51:46,560 --> 00:51:49,080 The crew come across an encouraging sign, 432 00:51:49,080 --> 00:51:52,520 from a rather unsavoury source. 433 00:51:52,520 --> 00:51:55,080 That's some whale faeces. 434 00:51:56,680 --> 00:51:59,840 So we've found a big whale poo in the water. 435 00:51:59,840 --> 00:52:03,200 Um, it's a good sign for us, we know that they're feeding here, 436 00:52:03,200 --> 00:52:04,720 so maybe they'll stick around. 437 00:52:07,120 --> 00:52:10,280 Finally, the crew find what they've been looking for - 438 00:52:10,280 --> 00:52:12,120 krill at the surface. 439 00:52:12,120 --> 00:52:13,960 Look at those birds in the water. 440 00:52:13,960 --> 00:52:16,080 So there's a small krill ball. 441 00:52:16,080 --> 00:52:18,040 We're going to go take a look at it. 442 00:52:18,040 --> 00:52:20,400 All right - remember, don't put me right on top of it. 443 00:52:20,400 --> 00:52:22,600 All right, ready? OK, the ball's right here. 444 00:52:22,600 --> 00:52:24,800 - Right here, right here. - Is it on the surface? - Yeah. 445 00:52:24,800 --> 00:52:26,280 - Good red? - Up at the top. 446 00:52:26,280 --> 00:52:28,600 - Got it? - Yeah, got it. 447 00:52:32,480 --> 00:52:35,560 No-one was prepared for what happened next. 448 00:52:36,760 --> 00:52:40,400 Right behind you! Hey, Hugh, here he comes! 449 00:52:40,400 --> 00:52:41,800 Oh! 450 00:52:43,920 --> 00:52:45,320 Massive surfacing. 451 00:52:46,400 --> 00:52:49,360 Oh, God - that's a shot. I bet you he got it. 452 00:52:50,800 --> 00:52:52,160 I bet you he got it. 453 00:52:52,160 --> 00:52:53,280 Oh! 454 00:52:57,200 --> 00:53:00,320 - MAN ON BOAT: - God, they're beautiful, aren't they? 455 00:53:00,320 --> 00:53:03,560 - What did you guys get? What did you guys get? - Oh, my God. 456 00:53:04,800 --> 00:53:06,200 Oh, my God. 457 00:53:07,960 --> 00:53:11,760 I still... I can't actually quite get my head around what I just saw. 458 00:53:11,760 --> 00:53:14,720 We were down there, Dave was filming the krill balls, 459 00:53:14,720 --> 00:53:18,120 and I just noticed, literally between his fins, 460 00:53:18,120 --> 00:53:22,080 this massive great whale just loomed out. 461 00:53:22,080 --> 00:53:24,240 David saw him, panned down. 462 00:53:24,240 --> 00:53:26,760 I don't know where it came from. 463 00:53:29,200 --> 00:53:31,440 Well, when I first looked down and I saw this whale, 464 00:53:31,440 --> 00:53:33,240 I was a little bit stressed out, 465 00:53:33,240 --> 00:53:37,840 because 95 feet of blue whale is going between my fins. 466 00:53:37,840 --> 00:53:42,320 He hooks around, comes up and just grabs a big mouthful. 467 00:53:48,360 --> 00:53:50,360 They're called blue whales for a reason, 468 00:53:50,360 --> 00:53:51,960 you just see them underwater, 469 00:53:51,960 --> 00:53:54,360 this bright, iridescent cobalt blue 470 00:53:54,360 --> 00:53:56,480 just pops out of the blue of the ocean. 471 00:54:00,080 --> 00:54:01,760 Finally, I get round to the other side, 472 00:54:01,760 --> 00:54:04,640 I go "OK, he left," we're like, "Phew! That was pretty intense." 473 00:54:04,640 --> 00:54:06,840 So I'm up trying to get just another shot of the krill 474 00:54:06,840 --> 00:54:09,440 and sure enough, wide open, he comes through one last time. 475 00:54:09,440 --> 00:54:10,960 I was kind of in the wrong spot, 476 00:54:10,960 --> 00:54:13,320 I had to do some serious evasive manoeuvres. 477 00:54:13,320 --> 00:54:15,120 But he comes through, closes his mouth... 478 00:54:15,120 --> 00:54:17,240 It was just amazing. 479 00:54:23,320 --> 00:54:25,600 The whole thing probably lasted ten minutes 480 00:54:25,600 --> 00:54:29,200 but it was hands down, without a doubt, no questions, 481 00:54:29,200 --> 00:54:31,840 the most intense, amazing thing that I've ever seen. 482 00:54:41,840 --> 00:54:45,120 To share the water and to look eye-to-eye with a blue whale 483 00:54:45,120 --> 00:54:47,400 is something I will never, ever forget. 484 00:54:50,560 --> 00:54:53,040 These shots gives John a unique insight 485 00:54:53,040 --> 00:54:55,760 into the feeding behaviour of blue whales. 486 00:54:55,760 --> 00:54:58,200 Let's just look at the side of his mouth there. 487 00:54:58,200 --> 00:55:00,600 So, basically, the water flow, you'd expect, 488 00:55:00,600 --> 00:55:02,560 would be coming out the back there. 489 00:55:02,560 --> 00:55:04,600 Yeah, look at that little fold there, 490 00:55:04,600 --> 00:55:06,240 that is really interesting. 491 00:55:10,320 --> 00:55:12,480 That's a great view. 492 00:55:12,480 --> 00:55:14,520 That's fantastic. 493 00:55:14,520 --> 00:55:18,000 Notice the full rotation there. Oh, that is... 494 00:55:18,000 --> 00:55:20,560 And the full inversion. 495 00:55:20,560 --> 00:55:22,680 OK - that's, again, a unique chance 496 00:55:22,680 --> 00:55:24,760 to see a perspective we don't get to see. 497 00:55:27,040 --> 00:55:29,360 With this close collaboration, 498 00:55:29,360 --> 00:55:33,160 the team have filmed blue whales as never before 499 00:55:33,160 --> 00:55:35,640 and at last have started to reveal 500 00:55:35,640 --> 00:55:38,920 the secret life of the ocean's greatest hunter. 501 00:55:45,760 --> 00:55:48,640 Next time, the hunt is on out in the open. 502 00:55:50,720 --> 00:55:52,560 On the deserts and grasslands... 503 00:55:59,840 --> 00:56:03,440 ..where hunters and hunted have nowhere to hide. 504 00:56:08,960 --> 00:56:12,760 For a free interactive Open University poster, call... 505 00:56:16,960 --> 00:56:18,240 ..or go to... 506 00:56:21,120 --> 00:56:23,680 ..and follow the links to the Open University.