1 00:00:01,139 --> 00:00:03,244 Viewers like you make this program possible. 2 00:00:02,000 --> 00:00:07,000 Downloaded from YTS.MX 3 00:00:03,279 --> 00:00:05,350 Support your local PBS station. 4 00:00:08,000 --> 00:00:13,000 Official YIFY movies site: YTS.MX 5 00:00:15,084 --> 00:00:18,432 Alone, a single fish may be insignificant. 6 00:00:21,745 --> 00:00:26,198 But together, they can hold the fate of an entire coastline. 7 00:00:29,581 --> 00:00:32,239 In the deep, billions of sardines 8 00:00:32,273 --> 00:00:35,069 begin a mass migration... 9 00:00:35,104 --> 00:00:39,142 sparked by a whisper of cool water. 10 00:00:39,177 --> 00:00:44,354 It's the largest movement of living things on Earth. 11 00:00:44,389 --> 00:00:48,531 And it's about to become nature's greatest ambush. 12 00:00:53,812 --> 00:00:57,643 Every predator along the coast is counting on this event... 13 00:00:59,818 --> 00:01:02,786 ...to feast on the abundance the sardines bring... 14 00:01:08,620 --> 00:01:11,519 ...before they slip away into the deep. 15 00:01:44,897 --> 00:01:46,934 Off the southern tip of Africa, 16 00:01:46,968 --> 00:01:51,318 the frigid South Atlantic mixes with the milder Indian ocean. 17 00:01:54,044 --> 00:01:57,600 The waters are cold and rich with plankton, 18 00:01:57,634 --> 00:02:00,396 fed by upwellings from the mighty Atlantic. 19 00:02:03,502 --> 00:02:06,885 Perfect conditions for a tiny fish to thrive. 20 00:02:13,892 --> 00:02:18,345 Sardines by the billions live here year-round, 21 00:02:18,379 --> 00:02:21,279 swimming and feeding together in loose shoals 22 00:02:21,313 --> 00:02:23,971 of hundreds of thousands of individuals. 23 00:02:26,353 --> 00:02:31,289 Then in late April, ocean currents undergo a subtle shift. 24 00:02:37,847 --> 00:02:40,021 As the southern winter approaches, 25 00:02:40,056 --> 00:02:43,439 upwellings and eddies force a tendril of cold water 26 00:02:43,473 --> 00:02:46,959 toward the east. 27 00:02:46,994 --> 00:02:50,549 The warm Agulhas Current moves further offshore, 28 00:02:50,584 --> 00:02:53,725 allowing the cold stream to gain momentum. 29 00:02:56,314 --> 00:02:59,351 The cold-water sardines instinctively cluster 30 00:02:59,386 --> 00:03:01,250 in the chillier current. 31 00:03:06,600 --> 00:03:10,673 150 miles out to sea, on the Agulhas Banks, 32 00:03:10,707 --> 00:03:13,158 schools begin to mass together... 33 00:03:15,125 --> 00:03:19,509 ...until they form a mega shoal 20 miles long. 34 00:03:22,961 --> 00:03:25,239 Then the single superorganism 35 00:03:25,274 --> 00:03:28,000 pours into the cold-water highway 36 00:03:28,035 --> 00:03:30,762 toward the coast and shallower water. 37 00:03:34,490 --> 00:03:38,183 It's the biggest biomass migration on the planet, 38 00:03:38,218 --> 00:03:42,774 exceeding the great herds of the Serengeti. 39 00:03:42,808 --> 00:03:48,504 Yet, exactly why they do it remains a mystery. 40 00:03:48,538 --> 00:03:51,955 The journey serves no apparent benefit to the fish. 41 00:03:54,717 --> 00:03:57,685 It will inevitably dead-end in a warm sea, 42 00:03:57,720 --> 00:03:59,791 unsuitable for sardines. 43 00:04:01,793 --> 00:04:04,796 How far they travel depends entirely on the vagaries 44 00:04:04,830 --> 00:04:06,901 of this year's cold current. 45 00:04:09,110 --> 00:04:10,698 But one thing is certain... 46 00:04:10,733 --> 00:04:14,978 an entire food web is counting on the sardines to make the run. 47 00:04:22,676 --> 00:04:26,196 Some predators will follow the shoal for weeks. 48 00:04:27,577 --> 00:04:31,409 Others wait for the feast to pass close to shore. 49 00:04:32,513 --> 00:04:35,861 Some even race hundreds of miles to intercept it. 50 00:04:45,215 --> 00:04:48,426 To the multitude, this year's sardine run can mean 51 00:04:48,460 --> 00:04:52,222 the difference between abundance and deprivation. 52 00:04:54,501 --> 00:04:57,124 All are at the mercy of the current. 53 00:05:02,440 --> 00:05:05,719 If the water temperature stays below 70 degrees, 54 00:05:05,753 --> 00:05:08,653 the sardines could travel 1,000 miles 55 00:05:08,687 --> 00:05:11,311 up the Eastern coast of South Africa. 56 00:05:12,898 --> 00:05:15,418 But if the tendril of cold water fades, 57 00:05:15,453 --> 00:05:20,078 the shoals will turn, disperse, or disappear into the deep. 58 00:05:29,156 --> 00:05:31,192 The coastline waits. 59 00:05:35,818 --> 00:05:38,890 The first hazard for the fish lies just 100 miles 60 00:05:38,924 --> 00:05:40,823 from the sardine's home turf... 61 00:05:46,415 --> 00:05:50,211 ...a colony of some 4,000 Cape fur seals. 62 00:05:52,317 --> 00:05:54,008 They're local predators, 63 00:05:54,043 --> 00:05:56,528 patrolling the shallows close to shore. 64 00:06:02,085 --> 00:06:05,054 The pups need milk every four hours... 65 00:06:07,470 --> 00:06:09,886 ...so moms can't go far to hunt. 66 00:06:17,963 --> 00:06:20,034 And they're reluctant to leave the safety 67 00:06:20,069 --> 00:06:22,002 of coastal kelp forests. 68 00:06:24,625 --> 00:06:26,731 The towering plants offer protection 69 00:06:26,765 --> 00:06:28,767 from great white sharks. 70 00:06:31,080 --> 00:06:33,841 If the seals are to feast on sardines, 71 00:06:33,876 --> 00:06:37,707 they need the shoals to come to them. 72 00:06:37,742 --> 00:06:43,333 Mothers depend on the oily fish to fuel their milk supply. 73 00:06:43,368 --> 00:06:46,060 And they're already pregnant with next year's baby... 74 00:06:53,551 --> 00:06:56,692 ...a precarious position when your food source is fickle. 75 00:07:01,110 --> 00:07:04,562 The colony is crowded. 76 00:07:04,596 --> 00:07:06,633 Pups cling to mothers. 77 00:07:09,670 --> 00:07:11,258 Tempers fray. 78 00:07:18,541 --> 00:07:21,648 But this year, the sea delivers. 79 00:07:25,790 --> 00:07:28,689 The cold current pushes clouds of zooplankton 80 00:07:28,724 --> 00:07:31,796 toward the coast and the seal colony. 81 00:07:34,764 --> 00:07:36,870 The little fish follow their food... 82 00:07:40,770 --> 00:07:43,463 ...directly into the kelp beds. 83 00:07:51,747 --> 00:07:54,508 For the seals, it's the moment of the year. 84 00:08:03,448 --> 00:08:07,314 Their front flippers are large and incredibly powerful. 85 00:08:11,456 --> 00:08:15,909 Like paddles, they propel the seals at 15 miles per hour. 86 00:08:22,363 --> 00:08:26,402 And they provide control when maneuverability matters most. 87 00:09:00,056 --> 00:09:02,576 Every seal cooperates. 88 00:09:10,411 --> 00:09:12,759 The seals swallow fish whole... 89 00:09:15,244 --> 00:09:17,695 ...even when they're underwater. 90 00:09:40,510 --> 00:09:45,619 In the onslaught, the sardines school in an ever tighter mass. 91 00:09:45,654 --> 00:09:49,071 It's a proven defense. 92 00:09:49,105 --> 00:09:51,832 Every fish is equipped with a lateral line... 93 00:09:51,867 --> 00:09:55,422 sensory cells in its head, trunk, and tail. 94 00:09:57,010 --> 00:09:59,944 It's sensitive enough to pick up the slightest change 95 00:09:59,978 --> 00:10:01,497 in water pressure. 96 00:10:04,673 --> 00:10:07,537 When a fish feels its neighbor move, 97 00:10:07,572 --> 00:10:10,333 it instantly responds in kind. 98 00:10:11,956 --> 00:10:16,719 Millions of tiny, synchronized movements combine into one, 99 00:10:16,754 --> 00:10:19,653 forming a superorganism that shape-shifts 100 00:10:19,688 --> 00:10:21,897 and slips just out of reach. 101 00:10:26,142 --> 00:10:29,145 The assault by thousands of hungry seals 102 00:10:29,180 --> 00:10:31,631 barely makes a dent in the giant shoal. 103 00:10:34,323 --> 00:10:36,843 The sardines make their getaway up the coast, 104 00:10:36,877 --> 00:10:38,603 and the seals don't follow. 105 00:10:41,157 --> 00:10:43,539 They need to get back to their hungry pups. 106 00:10:46,749 --> 00:10:50,546 The shoal always stays in the cold current, 107 00:10:50,580 --> 00:10:52,997 covering up to 40 miles a day. 108 00:10:56,310 --> 00:11:00,073 Now the females drop eggs as they move up the coast... 109 00:11:01,937 --> 00:11:03,490 ...prompting some to suggest 110 00:11:03,524 --> 00:11:07,459 that this is an annual spawning run. 111 00:11:07,494 --> 00:11:11,325 Others say it's simply driven by wind and cold water. 112 00:11:13,569 --> 00:11:17,607 With each mile, the water grows imperceptibly warmer. 113 00:11:20,541 --> 00:11:23,683 There's no telling where or when, 114 00:11:23,717 --> 00:11:27,169 but the cold current will eventually dissipate. 115 00:11:32,346 --> 00:11:36,419 For now, it remains strong, impelling the fish onward. 116 00:11:58,131 --> 00:12:01,962 By early May, the sardines approach another landmark... 117 00:12:04,171 --> 00:12:06,898 ...400 miles east of the seal colony. 118 00:12:10,799 --> 00:12:12,490 Bird Island. 119 00:12:18,599 --> 00:12:22,155 It's the world's biggest colony of Cape gannets. 120 00:12:25,089 --> 00:12:26,849 For three months, the birds have been 121 00:12:26,884 --> 00:12:29,093 feeding their growing chicks. 122 00:12:34,063 --> 00:12:36,548 They may be fierce ocean predators, 123 00:12:36,583 --> 00:12:38,930 but they're also devoted parents. 124 00:12:44,764 --> 00:12:46,006 They're monogamous, 125 00:12:46,041 --> 00:12:49,147 always returning to the same nest. 126 00:12:53,600 --> 00:12:55,050 It's crowded. 127 00:12:55,084 --> 00:12:57,984 That means competition for real estate... 128 00:12:58,018 --> 00:12:59,571 and food. 129 00:13:07,303 --> 00:13:10,928 With over 200,000 birds in the colony, 130 00:13:10,962 --> 00:13:15,484 they need 9,000 tons of fish in one breeding season. 131 00:13:26,633 --> 00:13:29,636 The gannets have pinned their entire breeding cycle 132 00:13:29,670 --> 00:13:32,777 on the unpredictable arrival of sardines. 133 00:13:40,958 --> 00:13:44,616 Scouts return with full bellies and good news. 134 00:13:47,102 --> 00:13:49,069 The fish are coming. 135 00:13:54,350 --> 00:13:58,285 The sardine superorganism is 20 miles offshore... 136 00:14:01,185 --> 00:14:04,015 ...within striking distance of the colony. 137 00:14:16,890 --> 00:14:21,101 The birds appear awkward on the ground, even comical. 138 00:14:21,136 --> 00:14:26,003 But once they achieve air speed, they are all grace and danger. 139 00:14:52,961 --> 00:14:55,549 They soar 100 feet in the air. 140 00:14:57,966 --> 00:15:01,003 They scan the shoal with binocular vision... 141 00:15:16,501 --> 00:15:18,020 ...lock on to a target... 142 00:15:20,229 --> 00:15:23,163 ...then dive. 143 00:15:27,374 --> 00:15:31,206 Gannets hit the water at 60 miles per hour. 144 00:15:39,939 --> 00:15:43,045 Muscles lock their neck vertebrae into place. 145 00:15:51,743 --> 00:15:55,161 Airbags in the face and chest absorb impact. 146 00:16:06,655 --> 00:16:10,866 The sardines swim deeper to escape, 147 00:16:10,900 --> 00:16:13,524 but the birds' momentum carries them down... 148 00:16:17,355 --> 00:16:21,187 ...30 feet underwater. 149 00:16:21,221 --> 00:16:24,052 If a gannet misses the target, it holds its breath 150 00:16:24,086 --> 00:16:27,779 and paddles, penguin-like, for a second grab. 151 00:16:53,426 --> 00:16:56,360 This first hunt is all for the youngsters. 152 00:16:56,394 --> 00:16:58,569 Gannet parents load up their gizzards 153 00:16:58,603 --> 00:17:01,503 and return at high speed to Bird Island. 154 00:17:18,382 --> 00:17:22,282 Every parent knows exactly where to find its chick. 155 00:17:43,131 --> 00:17:45,616 The food cargo is precious. 156 00:17:48,653 --> 00:17:51,760 A healthy sardine run means more young gannets 157 00:17:51,794 --> 00:17:53,900 are given a chance to survive. 158 00:17:58,146 --> 00:18:01,149 But this is the fledglings' last free meal. 159 00:18:04,152 --> 00:18:08,087 The parent birds will leave them forever and follow the shoals. 160 00:18:11,573 --> 00:18:13,299 Any gannet that wants to eat 161 00:18:13,333 --> 00:18:16,302 must get on the wing and follow the fish. 162 00:18:20,478 --> 00:18:23,550 This is motivation for the chicks to fly. 163 00:18:30,454 --> 00:18:33,664 The hungrier they get, the harder they try. 164 00:18:43,191 --> 00:18:45,158 The learning curve is steep, 165 00:18:45,193 --> 00:18:48,161 against howling wind and rough seas. 166 00:19:01,692 --> 00:19:04,833 Crash-landing in the waves is their first pitfall... 167 00:19:13,082 --> 00:19:16,293 ...but the wild surf is not the real danger. 168 00:19:18,916 --> 00:19:21,919 Fur seals hunt these shores, too. 169 00:20:12,935 --> 00:20:15,731 Fledglings don't have the strength or experience 170 00:20:15,766 --> 00:20:17,319 for a water take-off. 171 00:20:22,082 --> 00:20:24,533 Soaked feathers weigh them down. 172 00:20:59,568 --> 00:21:03,676 Just as the gannets exacted their toll on the sardines, 173 00:21:03,710 --> 00:21:07,852 the bird colony now suffers its own losses. 174 00:21:49,722 --> 00:21:53,967 The lucky ones must dry their feathers and try again. 175 00:21:56,625 --> 00:22:00,629 They can't miss out on the first sardine hunt of their lives. 176 00:22:36,355 --> 00:22:40,048 The sardines move east at 6 miles per hour. 177 00:22:42,844 --> 00:22:46,365 They're approaching the first real crux of their journey. 178 00:22:49,954 --> 00:22:54,511 600 miles into the run, the coastline bends north, 179 00:22:54,545 --> 00:22:57,203 and the continental shelf starts to narrow. 180 00:22:59,792 --> 00:23:03,105 Their cold-water ribbon is pinched against the coast 181 00:23:03,140 --> 00:23:05,660 by warm offshore currents. 182 00:23:07,524 --> 00:23:09,664 Billions of sardines must squeeze 183 00:23:09,698 --> 00:23:12,252 into the cold but narrowing channel. 184 00:23:16,153 --> 00:23:19,467 The shoal is stretched longer and thinner. 185 00:23:19,501 --> 00:23:21,745 The fish pack tighter together. 186 00:23:28,476 --> 00:23:32,687 This current delivers them to a place called the Wild Coast. 187 00:23:34,896 --> 00:23:39,935 It's a 200-mile stretch... a pristine, untouched transition 188 00:23:39,970 --> 00:23:43,007 between temperate and tropical biomes. 189 00:23:49,186 --> 00:23:52,085 It's not only a mix of water temperatures, 190 00:23:52,120 --> 00:23:55,848 it's also a crossroads for myriad species. 191 00:23:57,366 --> 00:24:00,715 It's June and humpback whales pass from Antarctica 192 00:24:00,749 --> 00:24:02,820 to breeding grounds farther north. 193 00:24:10,379 --> 00:24:12,830 Others live here all year round. 194 00:24:27,880 --> 00:24:32,436 50 miles ahead of the shoal, resident bottlenose dolphins 195 00:24:32,471 --> 00:24:34,231 relish winter's arrival. 196 00:24:40,548 --> 00:24:44,517 Dolphins live in social groups of about 25 members. 197 00:24:49,142 --> 00:24:53,146 Their play reveals why they're such formidable hunters. 198 00:24:57,496 --> 00:25:00,533 They're fast, they communicate, 199 00:25:00,568 --> 00:25:02,362 and they move as a unit. 200 00:25:05,193 --> 00:25:08,127 A real-life sardine nemesis. 201 00:25:10,025 --> 00:25:13,166 And this resident pod is just the advance guard 202 00:25:13,201 --> 00:25:15,272 for an even greater army. 203 00:25:25,282 --> 00:25:27,215 Common dolphins. 204 00:25:35,326 --> 00:25:38,122 They spend most of their lives in warmer waters 205 00:25:38,157 --> 00:25:41,574 along the coast. 206 00:25:41,609 --> 00:25:45,302 This time of year, their calves are just beginning to hunt. 207 00:25:47,925 --> 00:25:51,998 Mothers need to wean them before next spring's breeding season. 208 00:25:53,897 --> 00:25:57,003 A glut of fish would be a crucial windfall. 209 00:26:01,663 --> 00:26:06,495 There's no guarantee the sardine run will reach them. 210 00:26:06,530 --> 00:26:08,843 So they come to it. 211 00:26:14,711 --> 00:26:19,578 As they head south, hundreds of small family pods converge. 212 00:26:32,004 --> 00:26:34,938 A dolphin super pod begins to form, 213 00:26:34,972 --> 00:26:37,630 streaming to intercept the shoal. 214 00:26:47,675 --> 00:26:53,128 100 miles to the south, the fish pour along the Wild Coast... 215 00:26:53,163 --> 00:26:55,303 unaware of what lies ahead. 216 00:26:57,512 --> 00:27:00,929 As the narrowing current pushes them to the shallows, 217 00:27:00,964 --> 00:27:04,346 the shoal fragments. 218 00:27:04,381 --> 00:27:10,076 Smaller, isolated bait balls offer a new opportunity... 219 00:27:10,111 --> 00:27:11,733 for sharks. 220 00:27:17,566 --> 00:27:20,811 These migratory blacktips and dusky sharks 221 00:27:20,846 --> 00:27:24,401 have moved down from the warmer waters farther north. 222 00:27:26,679 --> 00:27:28,992 Little is known of their lives, 223 00:27:29,026 --> 00:27:31,926 but shark nurseries have been discovered nearby, 224 00:27:31,960 --> 00:27:33,479 suggesting that the sharks... 225 00:27:33,513 --> 00:27:35,584 like other creatures along the coast... 226 00:27:35,619 --> 00:27:39,002 may time their breeding cycle to the sardine run. 227 00:27:42,937 --> 00:27:46,665 Tiny fish face off with dozens of sharks. 228 00:27:50,289 --> 00:27:54,327 It seems an unfair match... 229 00:27:54,362 --> 00:27:57,537 but the sardines launch their schooling defense. 230 00:28:08,514 --> 00:28:12,691 As the sharks move, they send a pressure wave through the water. 231 00:28:14,416 --> 00:28:17,972 The fish detect it through their sensitive lateral lines. 232 00:28:21,630 --> 00:28:24,116 Just one moves out of harm's way, 233 00:28:24,150 --> 00:28:26,981 and every fish around it follows. 234 00:28:33,194 --> 00:28:35,299 It's incredibly effective. 235 00:28:41,823 --> 00:28:44,792 The sharks simply can't turn and bite quick enough. 236 00:29:03,742 --> 00:29:06,606 The predators change tactics. 237 00:29:14,856 --> 00:29:18,377 With sudden bursts of speed, they try and carve the shoal 238 00:29:18,411 --> 00:29:20,620 into even smaller balls... 239 00:29:23,727 --> 00:29:26,385 ...but they just don't coordinate enough. 240 00:29:36,015 --> 00:29:39,708 A school of 60-pound tuna gets in on the action. 241 00:29:43,782 --> 00:29:46,508 Normally the sharks hunt tuna, 242 00:29:46,543 --> 00:29:49,546 but they seem to know help when they see it. 243 00:29:50,892 --> 00:29:55,000 The smaller tuna are much more agile. 244 00:29:55,034 --> 00:29:59,245 Within seconds, they slice a bait ball from the shoal 245 00:29:59,280 --> 00:30:01,351 and trap it against the surface, 246 00:30:01,385 --> 00:30:03,802 where it's easier for everyone to feed. 247 00:30:28,481 --> 00:30:32,485 Game fish and sharks enjoy a temporary truce 248 00:30:32,520 --> 00:30:35,040 as they feast on the same prey. 249 00:31:24,779 --> 00:31:27,402 The main shoal flees north, 250 00:31:27,437 --> 00:31:30,992 leaving this fragment behind to be obliterated. 251 00:31:50,667 --> 00:31:53,290 Even the gulls get their share. 252 00:32:21,008 --> 00:32:24,908 The mega shoal is now way out of its home habitat. 253 00:32:27,152 --> 00:32:31,294 As long as it's cold, they swim blindly along. 254 00:32:31,328 --> 00:32:34,469 They're heading toward a feature of the South African coast 255 00:32:34,504 --> 00:32:37,265 that will prove the most consequential milestone 256 00:32:37,300 --> 00:32:40,855 of their journey... 257 00:32:40,889 --> 00:32:44,410 a sandstone buttress called Waterfall Bluff. 258 00:32:51,314 --> 00:32:55,387 This rocky promontory shoves the cold current eastward 259 00:32:55,421 --> 00:32:58,390 to collide with the warm water just offshore. 260 00:33:07,813 --> 00:33:13,612 Some years the cold water can blast beyond this point... 261 00:33:13,646 --> 00:33:15,165 but not this year. 262 00:33:15,200 --> 00:33:17,996 The vital current thins to a trickle. 263 00:33:21,240 --> 00:33:25,486 The sardines follow into the bottleneck as if spellbound. 264 00:33:28,075 --> 00:33:31,561 Every single fish follows the same mission... 265 00:33:31,595 --> 00:33:34,426 stick with the school and stay in the middle. 266 00:33:34,460 --> 00:33:36,738 But in the fading current, 267 00:33:36,773 --> 00:33:40,949 the already fractured shoal breaks up even further. 268 00:33:40,984 --> 00:33:44,919 Small schools follow shifting pockets of cool water 269 00:33:44,953 --> 00:33:46,438 into oblivion. 270 00:33:50,649 --> 00:33:53,583 The great journey stalls for the fish 271 00:33:53,617 --> 00:33:56,931 and conditions align for every predator. 272 00:34:01,039 --> 00:34:04,283 A familiar enemy has trailed them all this way. 273 00:34:06,596 --> 00:34:09,323 Some gannets will fly for 24 hours 274 00:34:09,357 --> 00:34:12,636 to intercept the bottleneck... 275 00:34:12,671 --> 00:34:15,915 and there are plenty more roosting on the nearby coast. 276 00:34:18,642 --> 00:34:21,438 It's a true test for the rookies. 277 00:34:26,581 --> 00:34:28,859 The sharks are back for more, too. 278 00:34:32,863 --> 00:34:36,108 Until now, the sardines have managed to slough off 279 00:34:36,143 --> 00:34:40,595 small bait balls as sacrificial decoys. 280 00:34:40,630 --> 00:34:44,461 But now they're more vulnerable than they've ever been. 281 00:34:47,602 --> 00:34:50,018 The high-flying gannets are the first to spot 282 00:34:50,053 --> 00:34:51,641 a stalling shoal. 283 00:34:56,335 --> 00:34:58,682 The birds stand out against the sky 284 00:34:58,717 --> 00:35:02,307 like a homing beacon, guiding in an army. 285 00:35:06,345 --> 00:35:08,209 It's the dolphin super pod... 286 00:35:11,833 --> 00:35:15,941 ...now grown to 20,000 strong. 287 00:35:45,004 --> 00:35:48,456 The sardines now face an unprecedented assault 288 00:35:48,491 --> 00:35:51,942 from a fleet of swift ocean-going hunters... 289 00:35:58,673 --> 00:36:02,608 ...and a far-flung deadly air force assembling above. 290 00:36:43,442 --> 00:36:47,274 The sardines turn to the only defense they know... 291 00:36:47,308 --> 00:36:50,380 schooling up as tight as they can. 292 00:36:54,557 --> 00:36:57,353 One moves, and they all move. 293 00:37:12,920 --> 00:37:15,371 But the dolphins are prepared for this. 294 00:37:19,478 --> 00:37:22,964 Their goal is to prevent the shoal from diving deep. 295 00:37:28,453 --> 00:37:32,250 They coordinate their efforts, blocking the sardines' evasion. 296 00:37:35,391 --> 00:37:36,909 With surgical precision, 297 00:37:36,944 --> 00:37:39,878 they slice balls away from the main shoal. 298 00:37:47,817 --> 00:37:52,028 They blow bubbles to corral any fish that tries to break form... 299 00:37:58,103 --> 00:38:01,175 ...forcing the fish tighter and tighter together. 300 00:38:02,763 --> 00:38:04,868 Every fish instinctively tries to get 301 00:38:04,903 --> 00:38:06,456 into the middle of the pack. 302 00:38:08,907 --> 00:38:12,738 But now exhausted gills struggle to suck oxygen 303 00:38:12,773 --> 00:38:14,671 from turbulent water. 304 00:38:29,893 --> 00:38:34,415 Ball after ball is dissected from the shoal and obliterated. 305 00:38:36,348 --> 00:38:39,040 The dolphins get what they've waited for. 306 00:39:15,249 --> 00:39:17,527 The toll is exponential. 307 00:39:22,152 --> 00:39:25,397 The dolphins are so effective at herding the fish 308 00:39:25,432 --> 00:39:28,952 that every other predator is also more successful. 309 00:39:59,880 --> 00:40:02,572 As the fish are driven to the surface, 310 00:40:02,607 --> 00:40:06,058 gannets get easy access. 311 00:41:03,357 --> 00:41:06,774 Dark fledglings now hunt like experts. 312 00:41:43,811 --> 00:41:46,573 Sharks follow and wait for the perfect moment 313 00:41:46,607 --> 00:41:49,127 to cash in on the tight balls. 314 00:41:51,439 --> 00:41:53,476 They pick off the edges at first... 315 00:41:56,893 --> 00:41:58,550 ...then they plough in. 316 00:42:13,600 --> 00:42:15,912 The dolphins are relentless. 317 00:42:22,367 --> 00:42:26,578 Youngsters take the cue and feed on fish for the first time. 318 00:42:48,911 --> 00:42:53,674 Along miles of coastline, every predator is synchronized. 319 00:43:09,483 --> 00:43:12,762 Unlikely accomplices of all stripes work together 320 00:43:12,797 --> 00:43:15,178 toward one brutal goal. 321 00:44:10,924 --> 00:44:13,029 And then, with the fish exhausted 322 00:44:13,064 --> 00:44:16,274 and thousands of predators well fed, 323 00:44:16,308 --> 00:44:18,207 the biggest arrives... 324 00:44:26,802 --> 00:44:29,805 ...a 20-ton Bryde's whale. 325 00:44:33,878 --> 00:44:38,227 Thousands of sardines gone in a single gulp. 326 00:44:58,419 --> 00:45:00,974 The feast goes on for days. 327 00:45:05,081 --> 00:45:08,084 The great shoal is in tatters. 328 00:45:20,856 --> 00:45:24,722 It's now a 3-mile buffet. 329 00:45:31,625 --> 00:45:36,803 Too confused and spent to reform their shoal, 330 00:45:36,837 --> 00:45:39,978 they're almost 800 miles from home. 331 00:45:50,851 --> 00:45:55,580 They've been duped by the vanishing current. 332 00:45:55,614 --> 00:45:59,998 Now they're lost and scattered in a strange, warm ocean... 333 00:46:02,690 --> 00:46:04,865 ...simply food for others. 334 00:46:07,972 --> 00:46:10,422 And yet it isn't over. 335 00:46:14,633 --> 00:46:17,671 The predator of all predators arrives. 336 00:46:22,193 --> 00:46:23,884 Orcas. 337 00:46:28,302 --> 00:46:31,685 As smart and cooperative as a common dolphin 338 00:46:31,719 --> 00:46:33,687 and three times bigger. 339 00:46:36,863 --> 00:46:40,176 Orcas never used to travel for the sardine run, 340 00:46:40,211 --> 00:46:44,767 but now they swim thousands of miles to intercept the shoals. 341 00:46:54,984 --> 00:46:57,642 But it's not the sardines they're after. 342 00:47:07,548 --> 00:47:10,413 They're here to hunt dolphins. 343 00:47:20,009 --> 00:47:23,944 Not chasing anymore but running. 344 00:47:23,979 --> 00:47:26,498 The orcas are not only more powerful, 345 00:47:26,533 --> 00:47:28,397 they have more stamina. 346 00:47:36,060 --> 00:47:38,925 Just as the dolphins corralled the fish, 347 00:47:38,959 --> 00:47:41,755 now the orcas work the dolphins. 348 00:47:46,484 --> 00:47:48,831 They isolate one from the pod. 349 00:48:00,429 --> 00:48:04,122 Once they've locked onto their target, they tag-team... 350 00:48:06,849 --> 00:48:08,437 ...chasing it... 351 00:48:11,923 --> 00:48:15,237 ...exhausting it... 352 00:48:15,271 --> 00:48:17,929 then... ramming it. 353 00:49:01,697 --> 00:49:03,871 They attack again and again 354 00:49:03,906 --> 00:49:07,220 until the dolphin can no longer swim. 355 00:49:32,417 --> 00:49:35,800 Before they can feast, they drown it. 356 00:49:53,645 --> 00:49:57,028 The orcas have scattered the dolphin super pod. 357 00:49:59,410 --> 00:50:02,309 Without the organizing force of the dolphins, 358 00:50:02,344 --> 00:50:07,694 the sardines regroup and slip away into deep, cold water. 359 00:50:10,421 --> 00:50:14,149 The massive cloud of fish that dominated the coastline 360 00:50:14,183 --> 00:50:18,049 suddenly vanishes, as if absorbed by the sea. 361 00:50:25,884 --> 00:50:29,888 As July concludes, the sated hunters disperse. 362 00:50:32,891 --> 00:50:36,378 Gannets proceed to travel up to 60 miles a day 363 00:50:36,412 --> 00:50:38,449 searching for more food. 364 00:50:41,797 --> 00:50:44,593 Sharks continue their migrations, 365 00:50:44,627 --> 00:50:47,147 fully fed and stronger for it. 366 00:50:54,775 --> 00:50:58,676 Dolphins have successfully weaned their calves. 367 00:51:04,992 --> 00:51:08,548 Super pods thin out as family units regroup 368 00:51:08,582 --> 00:51:11,516 and return to their regular hunting grounds. 369 00:51:15,831 --> 00:51:18,040 The cold current has delivered the feast 370 00:51:18,075 --> 00:51:20,353 that all the animals were counting on. 371 00:51:24,184 --> 00:51:28,809 Now it fades away, mixing with the warm Indian Ocean. 372 00:51:35,782 --> 00:51:39,268 Some believe the sardines ride the current down 373 00:51:39,303 --> 00:51:41,891 to secretly spawn in the deep. 374 00:51:43,514 --> 00:51:46,033 Others say they follow it all the way back, 375 00:51:46,068 --> 00:51:49,175 1,000 miles to their home off the Cape. 376 00:51:52,281 --> 00:51:55,077 Next year the cold current will reform, 377 00:51:55,112 --> 00:51:59,150 stronger or weaker than the last... 378 00:51:59,185 --> 00:52:00,738 and billions of little fish 379 00:52:00,772 --> 00:52:03,706 will be driven to follow its call, 380 00:52:03,741 --> 00:52:09,816 to face hardship and sacrifice, toward a purpose yet unknown.