1 00:00:07,341 --> 00:00:09,843 Planet Earth is so spectacular, 2 00:00:10,677 --> 00:00:13,680 it's easy to miss the smaller things in life. 3 00:00:15,766 --> 00:00:17,643 But take a closer look... 4 00:00:18,101 --> 00:00:20,562 and there's a whole undiscovered world. 5 00:00:22,648 --> 00:00:24,983 A world where tiny heroes... 6 00:00:26,485 --> 00:00:27,819 and little monsters... 7 00:00:28,987 --> 00:00:31,406 need incredible superpowers... 8 00:00:34,618 --> 00:00:40,040 to help them triumph against giant odds. 9 00:00:58,141 --> 00:01:02,104 Coral reefs are some of the most diverse places on the planet. 10 00:01:05,190 --> 00:01:09,319 Home to massive shoals and magnificent creatures. 11 00:01:13,031 --> 00:01:14,241 But beneath them... 12 00:01:14,908 --> 00:01:16,493 is a miniature metropolis... 13 00:01:19,830 --> 00:01:23,250 bustling with extraordinary little lives. 14 00:01:27,129 --> 00:01:28,964 These animals may be small... 15 00:01:29,882 --> 00:01:32,092 but the work they do is essential. 16 00:01:35,387 --> 00:01:38,390 And right now, they're busier than ever. 17 00:01:40,684 --> 00:01:44,897 Once a year, the reef stages a spectacular breeding event... 18 00:01:45,772 --> 00:01:48,025 vital to securing its future. 19 00:01:50,277 --> 00:01:53,780 But it's not easy being a small fish on a big reef. 20 00:01:56,658 --> 00:02:03,290 Tiny animals must overcome huge challenges to keep their coral city alive. 21 00:02:15,511 --> 00:02:19,723 The coral reef is as complex and crowded as any city. 22 00:02:23,227 --> 00:02:27,564 Each day starts busy and noisy. 23 00:02:30,817 --> 00:02:36,323 All the citizens calling to each other in a rousing underwater dawn chorus... 24 00:02:39,576 --> 00:02:41,495 of popping muscles... 25 00:02:43,288 --> 00:02:44,706 snapping claws... 26 00:02:46,083 --> 00:02:47,501 and chattering teeth. 27 00:02:53,507 --> 00:02:58,220 Only a healthy reef with a thriving community of tiny creatures 28 00:02:58,887 --> 00:03:00,389 sings this loud. 29 00:03:09,815 --> 00:03:13,193 Half the fish here are barely bigger than a bottle cap. 30 00:03:17,447 --> 00:03:20,075 But their services are in high demand. 31 00:03:28,834 --> 00:03:31,128 A turtle checks into the cleaning station... 32 00:03:33,005 --> 00:03:34,673 for a little shell shine. 33 00:03:49,688 --> 00:03:53,317 It's a job too big for a tiny blenny to manage alone. 34 00:03:57,988 --> 00:04:02,284 So a crew of algae-removal specialists help polish it off. 35 00:04:18,550 --> 00:04:21,970 A clown fish family is busy tending their anemone home. 36 00:04:25,724 --> 00:04:28,936 Few predators dare enter its stinging tentacles. 37 00:04:31,438 --> 00:04:34,399 But clown fish have a protective shield of mucus 38 00:04:34,483 --> 00:04:36,485 that allows them to live here permanently. 39 00:04:42,699 --> 00:04:46,578 In return, they keep the anemone clean and oxygenated. 40 00:04:51,792 --> 00:04:56,255 Hidden underneath, the male has 500 eggs to look after. 41 00:04:58,131 --> 00:05:00,843 Each smaller than a grain of rice. 42 00:05:05,514 --> 00:05:08,600 If they hatch on the same night the reef breeds, 43 00:05:08,684 --> 00:05:11,520 it will give them the best chance of survival. 44 00:05:17,609 --> 00:05:20,028 Until then, they should be safe. 45 00:05:21,613 --> 00:05:24,616 This is one of the most secure homes on the reef. 46 00:05:26,785 --> 00:05:28,662 And the family never stray far. 47 00:05:33,208 --> 00:05:36,837 Out here, there's always a bigger fish. 48 00:05:43,760 --> 00:05:45,762 The leopard coral grouper. 49 00:06:02,946 --> 00:06:05,949 Little damselfish take cover in the maze of coral... 50 00:06:07,826 --> 00:06:09,661 beyond the grouper's reach. 51 00:06:12,664 --> 00:06:14,499 But this smart fish doesn't give up. 52 00:06:16,001 --> 00:06:17,336 He just calls in... 53 00:06:18,295 --> 00:06:19,296 more arms. 54 00:06:25,969 --> 00:06:28,847 An octopus may seem an unlikely accomplice. 55 00:06:30,682 --> 00:06:33,393 But together, they make a killer team. 56 00:06:37,439 --> 00:06:40,359 When the grouper changes its colors to camouflage... 57 00:06:41,818 --> 00:06:43,946 the hunt is on. 58 00:07:00,754 --> 00:07:02,965 It's double trouble for damselfish. 59 00:07:15,769 --> 00:07:17,980 The grouper locates their hiding place. 60 00:07:19,815 --> 00:07:21,900 Then turns pale to point it out. 61 00:07:30,075 --> 00:07:31,285 Tentacles descend. 62 00:07:32,578 --> 00:07:34,121 Fish panic. 63 00:07:35,622 --> 00:07:37,791 Straight into the grouper's jaws. 64 00:07:43,338 --> 00:07:44,923 It's a terrible choice. 65 00:07:46,633 --> 00:07:50,679 Stay put, and risk the octopus's deadly reach. 66 00:07:52,347 --> 00:07:53,432 Or flee... 67 00:07:55,017 --> 00:07:57,686 and get picked off by the grouper. 68 00:08:05,027 --> 00:08:06,612 With no safe escape... 69 00:08:08,071 --> 00:08:11,283 sometimes the only option is to fight back. 70 00:08:18,957 --> 00:08:21,293 The damselfish mob the octopus... 71 00:08:22,669 --> 00:08:24,296 and try to drive it away. 72 00:08:29,134 --> 00:08:33,013 But the commotion attracts even bigger fish. 73 00:08:41,063 --> 00:08:43,899 It's a chance for the little fish to make their escape. 74 00:08:50,948 --> 00:08:52,616 With sharks circling... 75 00:08:55,035 --> 00:08:58,872 suddenly, it's everyone for themselves. 76 00:09:04,670 --> 00:09:06,088 So much for teamwork. 77 00:09:16,640 --> 00:09:19,059 Large sharks don't bother with small fry. 78 00:09:22,104 --> 00:09:27,943 But by scaring off other predators, they help tiny animals get back to work. 79 00:09:32,865 --> 00:09:35,075 Grazers keep the reef free of algae. 80 00:09:39,121 --> 00:09:41,748 Allowing slow-growing coral to thrive. 81 00:09:47,629 --> 00:09:51,675 Coral is actually made up of colonies of tiny animals. 82 00:09:53,468 --> 00:09:59,516 And each one contains microscopic plant cells that convert light into food. 83 00:10:02,644 --> 00:10:06,648 An amazing alliance on which the whole reef is built. 84 00:10:10,819 --> 00:10:14,198 Together, billions of little lives... 85 00:10:15,782 --> 00:10:18,994 create the largest living structures on Earth. 86 00:10:26,668 --> 00:10:28,879 But these coral cities are fragile. 87 00:10:32,090 --> 00:10:34,301 Vulnerable to warming seas... 88 00:10:35,969 --> 00:10:37,179 pollution... 89 00:10:38,222 --> 00:10:39,348 overfishing... 90 00:10:40,516 --> 00:10:42,601 and invasion. 91 00:10:46,396 --> 00:10:48,690 Crawling on hundreds of tubed feet. 92 00:10:52,444 --> 00:10:54,655 Armed with venomous spines. 93 00:11:02,788 --> 00:11:03,997 A monstrous... 94 00:11:04,915 --> 00:11:06,124 coral-eating... 95 00:11:07,084 --> 00:11:09,503 crown-of-thorns starfish. 96 00:11:13,632 --> 00:11:16,927 It can devour hundreds of corals each year. 97 00:11:20,722 --> 00:11:22,933 And there's not just one. 98 00:11:24,101 --> 00:11:26,103 There's a whole army of them... 99 00:11:27,479 --> 00:11:30,607 decimating the homes of all the tiny creatures. 100 00:11:38,866 --> 00:11:41,285 But unaware of the threat heading their way... 101 00:11:42,703 --> 00:11:47,332 the residents of the reef are busy, preparing to breed. 102 00:11:48,750 --> 00:11:50,377 And searching for food. 103 00:11:55,966 --> 00:11:59,178 The most complex eyes in the animal kingdom. 104 00:12:00,596 --> 00:12:03,807 With four times as many color receptors as a human's... 105 00:12:05,142 --> 00:12:10,147 the peacock mantis shrimp sees the world in a completely different light. 106 00:12:14,026 --> 00:12:19,740 She's no bigger than a tube of toothpaste, but far from defenseless. 107 00:12:22,743 --> 00:12:28,790 She packs a punch that rivals the acceleration of a 9-millimeter bullet. 108 00:12:30,626 --> 00:12:33,629 So fast, it vaporizes water. 109 00:12:39,176 --> 00:12:41,512 And can even create a flash of light. 110 00:12:50,854 --> 00:12:53,982 But even well-armed mantis shrimp need a safe place. 111 00:12:58,445 --> 00:13:01,448 Her burrow, and soon to be her nursery. 112 00:13:03,700 --> 00:13:05,327 Once renovations are complete. 113 00:13:12,543 --> 00:13:14,378 She already has a male visitor... 114 00:13:16,213 --> 00:13:17,464 looking for a mate. 115 00:13:18,799 --> 00:13:20,801 Or to steal her home. 116 00:13:27,766 --> 00:13:28,809 Either way... 117 00:13:30,602 --> 00:13:33,856 her lightning fists will make it very clear... 118 00:13:37,276 --> 00:13:39,403 she's not ready for guests. 119 00:13:44,616 --> 00:13:47,786 But this is a dangerous place to be caught out in the open. 120 00:14:01,341 --> 00:14:02,801 A voracious predator. 121 00:14:08,599 --> 00:14:09,933 The size of a... 122 00:14:12,227 --> 00:14:13,228 teacup. 123 00:14:16,690 --> 00:14:18,525 A dwarf cuttlefish. 124 00:14:19,484 --> 00:14:23,322 If this one is to reach breeding condition, he needs to get bigger. 125 00:14:24,364 --> 00:14:26,658 And that means a lot of eating. 126 00:14:29,494 --> 00:14:32,331 But he's a soft target himself. 127 00:14:34,750 --> 00:14:39,421 So the trick is to hunt without being hunted. 128 00:14:42,174 --> 00:14:47,012 This master of disguise can change the color and texture of his skin... 129 00:14:48,764 --> 00:14:50,182 to outwit predators... 130 00:14:51,308 --> 00:14:52,476 and prey. 131 00:15:02,611 --> 00:15:06,156 He'll live less than a year, so he needs to grow fast... 132 00:15:07,241 --> 00:15:09,576 eating pretty much anything that moves. 133 00:15:14,790 --> 00:15:17,376 Waving its arms to catch a meal of plankton... 134 00:15:19,920 --> 00:15:24,174 a button-sized boxer crab seems oblivious to the threat. 135 00:15:33,475 --> 00:15:34,893 A painful mistake. 136 00:15:38,772 --> 00:15:42,568 This crab holds miniature stinging anemones in its claws. 137 00:15:44,278 --> 00:15:47,322 Tiny Tasers to fend off predators. 138 00:15:51,493 --> 00:15:53,161 They're so effective, 139 00:15:53,245 --> 00:15:56,456 rivals will do anything to get hold of them. 140 00:16:05,048 --> 00:16:07,092 It's a remarkably delicate struggle. 141 00:16:10,387 --> 00:16:13,015 Neither crab wants to damage the anemones. 142 00:16:17,978 --> 00:16:23,192 With his opponent in a lock, the rival carefully extracts his prize. 143 00:16:32,326 --> 00:16:34,161 Now they have one each, 144 00:16:34,244 --> 00:16:39,166 both crabs will split them to regrow a full pair of stinging gloves. 145 00:16:45,005 --> 00:16:48,467 Anemones offer protection to all kinds of little creatures. 146 00:16:52,137 --> 00:16:54,139 Tiny see-through anemone shrimp. 147 00:16:56,141 --> 00:16:58,101 Cohabiting with the clown fish. 148 00:17:01,772 --> 00:17:03,982 They may only be the size of a paper clip... 149 00:17:06,443 --> 00:17:10,280 but they are brave enough to do business with the big fish on the reef. 150 00:17:19,289 --> 00:17:22,917 The shrimp advertise their services by rocking. 151 00:17:26,880 --> 00:17:29,007 And if the customer is a predator... 152 00:17:31,552 --> 00:17:35,264 they make sure their sales pitch is absolutely clear... 153 00:17:35,347 --> 00:17:36,974 by clapping. 154 00:17:53,824 --> 00:17:55,951 Once she's sure it's safe, 155 00:17:56,869 --> 00:17:58,829 one little shrimp gets to work. 156 00:18:00,539 --> 00:18:02,416 Exfoliating dead skin... 157 00:18:03,667 --> 00:18:05,294 picking off parasites... 158 00:18:06,086 --> 00:18:07,796 and cleaning the gills. 159 00:18:16,763 --> 00:18:20,934 She even braves the jaws for a little dental hygiene. 160 00:18:26,899 --> 00:18:30,277 Health services provided by tiny cleaners 161 00:18:30,360 --> 00:18:33,864 are essential for keeping big fish in top condition. 162 00:18:39,953 --> 00:18:44,833 All over the reef preparations for mating are underway. 163 00:18:50,756 --> 00:18:53,634 The mantis shrimp is almost done building her nursery. 164 00:18:57,638 --> 00:19:01,683 She's lifted a massive 3 kilos of debris to make it secure. 165 00:19:06,480 --> 00:19:12,194 And cleared her emergency exits, so she can keep her enemies guessing. 166 00:19:15,155 --> 00:19:20,452 Her building work is so extensive, others find a home here too. 167 00:19:25,249 --> 00:19:29,086 But she has one neighbor who's more of a problem. 168 00:19:34,091 --> 00:19:35,384 A tuskfish. 169 00:19:36,468 --> 00:19:39,096 One of the few fish known to use tools. 170 00:19:41,807 --> 00:19:44,935 It even has its own anvil for cracking clams. 171 00:19:53,068 --> 00:19:55,404 He's unlikely to eat a mantis shrimp. 172 00:19:58,156 --> 00:20:01,827 But his smash-and-grab approach to feeding could wreck her home. 173 00:20:05,581 --> 00:20:09,418 He shifts huge piles of rubble looking for food. 174 00:20:20,971 --> 00:20:22,306 He's got what he wanted. 175 00:20:24,641 --> 00:20:28,520 But now her nursery construction is way behind schedule. 176 00:20:32,900 --> 00:20:37,487 As the day draws to a close, the reef is getting busier. 177 00:20:43,702 --> 00:20:46,121 The clown fish eggs are close to hatching. 178 00:20:52,920 --> 00:20:55,130 And a fleet of cleaner wrasse are hard at work. 179 00:20:58,258 --> 00:21:00,177 Only the length of a finger, 180 00:21:00,260 --> 00:21:03,555 they're easily identified by their black and blue stripes. 181 00:21:17,569 --> 00:21:21,156 But not all are quite as well-intentioned as they appear. 182 00:21:27,162 --> 00:21:28,580 A fangblenny. 183 00:21:32,626 --> 00:21:36,547 This impostor changes his colors to mimic cleaner wrasse 184 00:21:36,630 --> 00:21:38,841 and slips among them unnoticed. 185 00:21:44,972 --> 00:21:46,515 But he's not here to clean. 186 00:21:54,439 --> 00:21:57,985 Raking his fangs across the skin of the unsuspecting fish... 187 00:22:01,154 --> 00:22:03,574 he steals a meal of scales. 188 00:22:13,750 --> 00:22:16,003 And before his victims know what hit them... 189 00:22:17,004 --> 00:22:19,506 this devious trickster disappears... 190 00:22:20,924 --> 00:22:22,176 back to his lair. 191 00:22:25,554 --> 00:22:29,975 Operating undercover helps many little animals survive on a big reef. 192 00:22:34,605 --> 00:22:37,941 It's how the dwarf cuttlefish has managed to stay alive... 193 00:22:39,318 --> 00:22:40,777 and stay fed. 194 00:22:47,868 --> 00:22:50,537 With each hunting success, he grows bigger. 195 00:22:58,712 --> 00:23:00,714 This female seems impressed. 196 00:23:01,381 --> 00:23:05,219 And for once, food isn't his first priority. 197 00:23:13,685 --> 00:23:16,522 The mantis shrimp has been getting her home back in order. 198 00:23:21,527 --> 00:23:22,778 Clearing out clutter. 199 00:23:24,905 --> 00:23:27,032 Making sure everything's in place. 200 00:23:29,785 --> 00:23:31,954 And adding the finishing touches. 201 00:23:43,715 --> 00:23:47,511 Finally, she's ready to receive a guest. 202 00:24:00,816 --> 00:24:04,069 Just as the reef is set for the most important event of the year, 203 00:24:04,945 --> 00:24:06,864 the coral killers arrive. 204 00:24:15,497 --> 00:24:17,916 Hordes of crown-of-thorns starfish. 205 00:24:26,216 --> 00:24:30,429 Extruding their stomachs, they digest the coral's living tissue. 206 00:24:33,682 --> 00:24:36,602 And leave only the white skeletons behind. 207 00:24:49,114 --> 00:24:52,409 There seems to be little the reef residents can do 208 00:24:52,492 --> 00:24:57,706 to stop the swarm of starfish from devouring every coral in their path. 209 00:25:08,675 --> 00:25:12,638 The home of this tiny crab is next on the menu. 210 00:25:22,564 --> 00:25:24,775 No matter how hard she tries... 211 00:25:26,777 --> 00:25:29,613 the starfish's body is almost impenetrable. 212 00:25:34,284 --> 00:25:36,745 But the soft sensitive base of its spines... 213 00:25:38,580 --> 00:25:40,249 is the chink in its armor. 214 00:25:44,253 --> 00:25:46,213 Time for one little crab... 215 00:25:47,339 --> 00:25:49,007 to take down a monster. 216 00:26:09,736 --> 00:26:13,407 Contending with guard crabs just isn't worth the pain. 217 00:26:24,418 --> 00:26:27,045 A diverse community of tiny creatures... 218 00:26:28,088 --> 00:26:29,756 all playing their part... 219 00:26:31,216 --> 00:26:37,431 keeps coral reefs healthy and far more resilient to the many threats they face. 220 00:26:44,938 --> 00:26:48,942 Even damaged areas of these living cities can regenerate. 221 00:26:55,032 --> 00:26:56,825 Once a year 222 00:26:56,909 --> 00:27:00,913 the perfect tide and the perfect temperature coincide. 223 00:27:08,795 --> 00:27:10,380 Tonight is the night... 224 00:27:11,715 --> 00:27:14,801 when the reef itself begins to breed. 225 00:27:22,017 --> 00:27:26,480 A tiny bundle, only the size of a peppercorn. 226 00:27:28,440 --> 00:27:33,654 All the ingredients to make baby corals in one package. 227 00:27:37,241 --> 00:27:39,034 The coral is spawning. 228 00:27:42,746 --> 00:27:45,541 Many other little reef animals are breeding too. 229 00:27:48,335 --> 00:27:50,921 The dwarf cuttlefish has secured his mate. 230 00:27:56,093 --> 00:27:59,972 Now it's time for her to tuck their eggs safely into the coral. 231 00:28:03,934 --> 00:28:06,103 The mantis shrimp also has eggs. 232 00:28:07,229 --> 00:28:08,480 Twenty thousand of them. 233 00:28:16,238 --> 00:28:18,740 And after one more cleaning from Dad... 234 00:28:21,493 --> 00:28:25,038 hundreds of clown fish larvae are cast adrift. 235 00:28:35,215 --> 00:28:39,386 Spawning together ensures as many new lives as possible... 236 00:28:40,429 --> 00:28:42,764 are carried safely away on the tide. 237 00:28:52,107 --> 00:28:55,152 Soon, small wonders are growing. 238 00:29:00,908 --> 00:29:03,035 No bigger than a peanut, 239 00:29:03,118 --> 00:29:07,497 a cuttlefish hatchling is just beginning its ocean adventure. 240 00:29:13,795 --> 00:29:19,468 And perhaps most important of all, a one-millimeter coral planula. 241 00:29:25,265 --> 00:29:27,351 Drawn toward the sound of the reef... 242 00:29:36,193 --> 00:29:39,738 a tiny brick that will grow into a mighty coral. 243 00:29:41,865 --> 00:29:46,745 And help build a future for all the residents of this coral city.