1 00:01:29,487 --> 00:01:32,445 The savage rocky shores of Christmas Island, 2 00:01:32,607 --> 00:01:35,838 200 miles south of Java, in the Indian 0cean. 3 00:01:36,007 --> 00:01:39,397 It's November, the moon is in its third quarter, 4 00:01:39,567 --> 00:01:41,797 and the sun is just setting. 5 00:01:41,967 --> 00:01:45,004 And in a few hours from now, on this very shore, 6 00:01:45,167 --> 00:01:48,637 a thousand million lives will be launched. 7 00:01:56,927 --> 00:01:59,122 These crabs are all females, 8 00:01:59,287 --> 00:02:02,279 and of a kind that occurs only on Christmas Island. 9 00:02:02,447 --> 00:02:06,122 As darkness falls, more and more of them appear, 10 00:02:06,287 --> 00:02:08,926 clambering resolutely down to the sea. 11 00:02:12,007 --> 00:02:13,998 Now it's nearing midnight. 12 00:02:14,167 --> 00:02:16,317 Their numbers can only be guessed at, 13 00:02:16,487 --> 00:02:20,878 but on the whole island there are probably 120 million of these crabs, 14 00:02:21,047 --> 00:02:24,323 and nearly all the adult females among them 15 00:02:24,487 --> 00:02:27,524 have chosen this time for their annual spawning. 16 00:02:44,047 --> 00:02:48,040 A crab like this is carrying about 100,000 eggs, 17 00:02:48,207 --> 00:02:52,519 and she has to shed them directly into the sea if they are to hatch. 18 00:02:52,687 --> 00:02:55,042 That's a hazardous business for her 19 00:02:55,207 --> 00:02:58,836 because although her distant ancestors came from the sea, 20 00:02:59,007 --> 00:03:02,795 she is a land crab...and she can't swim. 21 00:03:02,967 --> 00:03:07,199 So if a wave sweeps her away, she will assuredly drown. 22 00:03:07,367 --> 00:03:12,725 But, nonetheless, her compulsion to launch the next generation is irresistible, 23 00:03:12,887 --> 00:03:15,162 and when she does reach the sea, 24 00:03:15,327 --> 00:03:17,636 her triumph is apparently ecstatic. 25 00:03:31,887 --> 00:03:36,039 The crabs have picked the moment when the tide is at its highest, 26 00:03:36,207 --> 00:03:40,837 so they have the shortest distance to travel to reach the water. 27 00:03:41,007 --> 00:03:45,159 The astronomical numbers of their eggs turn the clear ocean water 28 00:03:45,327 --> 00:03:47,636 into a black turbid soup. 29 00:03:57,287 --> 00:04:00,279 As dawn approaches and the tide recedes, 30 00:04:00,447 --> 00:04:03,564 so the eggs are swept out to sea. 31 00:04:06,047 --> 00:04:09,676 Since life began, the sea has been full of eggs. 32 00:04:09,847 --> 00:04:14,967 The most ancient animals on the planet still live and breed there. 33 00:04:16,287 --> 00:04:20,041 Some, such as sea urchins, may be male or female. 34 00:04:20,207 --> 00:04:24,405 Both sexes discharge their sex cells during the same short period, 35 00:04:24,567 --> 00:04:28,355 so that they unite in the water and form fertile eggs. 36 00:04:29,647 --> 00:04:31,638 The sea brings them together, 37 00:04:31,807 --> 00:04:34,924 keeps the fertilised eggs at the stable temperature 38 00:04:35,087 --> 00:04:36,759 necessary for development, 39 00:04:36,927 --> 00:04:41,284 and transports them for hundreds of miles to new environments. 40 00:04:43,447 --> 00:04:47,963 This perpetually-renewed soup provides a vast banquet 41 00:04:48,127 --> 00:04:50,163 for other floating creatures. 42 00:04:50,327 --> 00:04:52,761 Small complex globes of jelly 43 00:04:52,927 --> 00:04:57,000 drive themselves through the water with lines of beating hairs 44 00:04:57,167 --> 00:05:00,716 and filter out the majority of the eggs. 45 00:05:35,807 --> 00:05:39,561 Many fish also scatter their eggs in the water 46 00:05:39,727 --> 00:05:42,195 and abandon them in a similar way. 47 00:05:42,607 --> 00:05:45,485 But the most stupendous egg producer of all 48 00:05:45,647 --> 00:05:48,844 lies beneath, nearly buried in the reef. 49 00:05:50,487 --> 00:05:53,684 The giant clam first discharges sperm... 50 00:05:55,287 --> 00:05:57,164 and then, half an hour later - 51 00:05:57,327 --> 00:06:00,683 because it's both male and female - eggs. 52 00:06:00,847 --> 00:06:05,762 In each annual spasm, it discharges a thousand million. 53 00:06:20,687 --> 00:06:22,837 In the north eastern Pacific, 54 00:06:23,007 --> 00:06:27,762 vast shoals of herring are moving towards the coast of Alaska. 55 00:06:39,487 --> 00:06:42,718 These must be the densest concentrations of animal bodies 56 00:06:42,887 --> 00:06:45,765 to be found anywhere in the world. 57 00:06:45,927 --> 00:06:50,398 Throughout their lives they move in huge assemblies, millions strong, 58 00:06:50,567 --> 00:06:53,843 sieving their floating food from the ocean waters. 59 00:06:54,087 --> 00:06:56,885 Now, even more tightly packed together, 60 00:06:57,047 --> 00:06:59,038 they start to spawn. 61 00:07:08,687 --> 00:07:10,837 Their eggs are sticky 62 00:07:11,007 --> 00:07:13,760 and cover the leaves of the sea plants. 63 00:07:39,607 --> 00:07:42,075 As the waves stir the waters, 64 00:07:42,247 --> 00:07:45,284 some of the vast deposit floats up to the surface. 65 00:07:46,447 --> 00:07:50,918 These milky slicks, miles long, stretching around the coast, 66 00:07:51,087 --> 00:07:54,966 may look like mud washed into the sea by a great river. 67 00:07:55,127 --> 00:07:58,756 But they're made up of nothing but eggs and milt, 68 00:07:58,927 --> 00:08:02,522 the annual legacy of the departed herring shoals. 69 00:08:16,687 --> 00:08:18,723 Many of the eggs are washed ashore 70 00:08:18,887 --> 00:08:22,163 and the receding tide leaves them stranded on the rocks 71 00:08:22,327 --> 00:08:24,887 like drifts of snow. 72 00:08:26,287 --> 00:08:29,882 And this provides a feast for birds. 73 00:08:31,087 --> 00:08:33,521 Gulls gorge on them. 74 00:08:50,287 --> 00:08:53,245 Thousands upon thousands of turnstones, 75 00:08:53,407 --> 00:08:56,558 sandpipers and other small waders also come. 76 00:08:56,727 --> 00:09:00,163 For them, this bonanza could not be better timed, 77 00:09:00,327 --> 00:09:03,125 for they are about to set off on their spring migration 78 00:09:03,287 --> 00:09:07,758 and they need to stock up with fuel before starting on their long flight. 79 00:09:23,687 --> 00:09:28,283 It's effective to lay vast numbers of eggs when there's water to distribute them. 80 00:09:28,447 --> 00:09:31,519 0n land, such numbers would be less practical. 81 00:09:31,687 --> 00:09:35,885 Even so, some land animals produce them in hundreds. 82 00:09:38,087 --> 00:09:40,078 These are young mantis. 83 00:09:40,247 --> 00:09:43,239 Their mother surrounded her batch of eggs with a liquid froth, 84 00:09:43,407 --> 00:09:45,398 which rapidly hardened. 85 00:09:45,567 --> 00:09:50,402 The young developed within and now they're ready for independent life. 86 00:09:53,007 --> 00:09:56,124 Their infant bodies are covered with a thin membrane 87 00:09:56,287 --> 00:09:59,484 and each hangs suspended by a thread of silk, 88 00:09:59,647 --> 00:10:02,366 while it slowly disentangles itself. 89 00:10:03,607 --> 00:10:06,519 0ne egg mass produced by a single female 90 00:10:06,687 --> 00:10:09,838 may release as many as 400 young. 91 00:10:18,687 --> 00:10:21,247 While latecomers continue to emerge, 92 00:10:21,407 --> 00:10:23,443 the first-born clamber up over them 93 00:10:23,607 --> 00:10:26,280 and prepare themselves for adult life. 94 00:10:36,687 --> 00:10:41,283 Frogs produce young that swim and breathe through gills - tadpoles. 95 00:10:41,447 --> 00:10:44,519 Most frogs lay their eggs in ponds and streams. 96 00:10:44,687 --> 00:10:46,245 But not all. 97 00:10:46,407 --> 00:10:51,276 This Trinidad tree frog creates its own watery nursery up in a tree, 98 00:10:51,447 --> 00:10:55,804 where there are no predatory fish to worry them or their babies. 99 00:10:56,687 --> 00:10:59,884 The female pulls two leaves together with her hind legs 100 00:11:00,047 --> 00:11:03,244 and extrudes her eggs between them. 101 00:11:09,927 --> 00:11:12,521 The eggs are surrounded by a sticky jelly 102 00:11:12,687 --> 00:11:14,518 which holds the leaves together. 103 00:11:14,687 --> 00:11:16,006 As they emerge, 104 00:11:16,167 --> 00:11:21,366 so the male on her back discharges his sperm and fertilises them. 105 00:11:35,087 --> 00:11:39,842 0ver the next eight days, the eggs slowly turn into tadpoles. 106 00:11:41,167 --> 00:11:45,046 0nce the first eggs hatch, the jelly begins to dissolve. 107 00:11:45,207 --> 00:11:49,564 The leaves separate and the liquid within starts to trickle out. 108 00:11:52,847 --> 00:11:55,520 And with it come the tadpoles. 109 00:11:59,847 --> 00:12:01,917 But this is no disaster. 110 00:12:02,087 --> 00:12:04,806 The tadpoles drop into a new existence, 111 00:12:04,967 --> 00:12:09,836 for their parents always build the nurseries overhanging water. 112 00:12:22,007 --> 00:12:25,044 Here, they can find something to eat 113 00:12:25,207 --> 00:12:27,880 and start to build their adult bodies. 114 00:12:30,927 --> 00:12:35,637 This South American rain frog is totally independent of pools and rivers. 115 00:12:35,807 --> 00:12:37,957 It lays its eggs on the ground. 116 00:12:38,127 --> 00:12:41,199 But each small globe is full of liquid. 117 00:12:41,367 --> 00:12:46,361 The tadpole not only develops inside this capsule, but stays there - 118 00:12:46,527 --> 00:12:51,362 swimming in its own personal pond until tadpole becomes frog. 119 00:13:37,247 --> 00:13:39,078 When the young finally emerge, 120 00:13:39,247 --> 00:13:41,556 they have no need to swim. 121 00:13:41,727 --> 00:13:45,037 Like their parents, they have lungs and legs. 122 00:13:54,007 --> 00:13:58,558 These elegant eggs are only the size of grains of sand. 123 00:14:16,007 --> 00:14:18,965 The young of the owl butterfly. 124 00:14:23,287 --> 00:14:27,166 Their beautiful shells are not just protective, they're edible. 125 00:14:27,327 --> 00:14:31,002 The mother butterfly built them from her bodily reserves of protein, 126 00:14:31,167 --> 00:14:36,366 so her young, when they emerge, have their first meal immediately to hand. 127 00:14:56,447 --> 00:15:00,235 There's another way of providing food for your developing young. 128 00:15:00,407 --> 00:15:02,398 Instead of getting it from your own body, 129 00:15:02,567 --> 00:15:04,762 you can get it from somebody else's. 130 00:15:04,927 --> 00:15:09,205 That, of course, involves the grisly process of body snatching, 131 00:15:09,367 --> 00:15:12,916 and that's just what's going on in this dried-up mudflat 132 00:15:13,087 --> 00:15:15,078 in the western United States. 133 00:15:16,767 --> 00:15:18,758 This strange insect 134 00:15:18,927 --> 00:15:22,602 is a murderous and very hard-working wasp. 135 00:15:25,167 --> 00:15:29,001 She is digging a tunnel to serve as her nursery. 136 00:15:30,687 --> 00:15:33,759 The sun-baked ground she selects is rock hard, 137 00:15:33,927 --> 00:15:36,316 and digging a hole in it is not easy. 138 00:15:48,687 --> 00:15:51,565 A lot of work is invested in one of these holes, 139 00:15:51,727 --> 00:15:55,561 and if one seems vacant, another wasp will try to claim it. 140 00:15:59,007 --> 00:16:00,725 0nce the burrow is finished, 141 00:16:00,887 --> 00:16:03,720 the female performs an elaborate dance around it - 142 00:16:03,887 --> 00:16:08,802 remembering its surroundings so she knows exactly where it is. 143 00:16:11,207 --> 00:16:15,997 And then she conceals it, so that none but she is likely to find it. 144 00:16:24,487 --> 00:16:26,478 Her nursery must now be provisioned, 145 00:16:26,647 --> 00:16:29,798 and for that she needs fresh meat. 146 00:16:32,367 --> 00:16:33,925 A caterpillar. 147 00:16:34,087 --> 00:16:36,521 First, she paralyses it with her sting. 148 00:16:42,487 --> 00:16:47,163 Thanks to her dance, she knows exactly where her hidden hole lies. 149 00:16:55,487 --> 00:16:58,524 Each burrow will have several caterpillars in it, 150 00:16:58,687 --> 00:17:04,080 and each addition requires the same stopping and unstopping of the tunnel entrance. 151 00:17:10,007 --> 00:17:13,158 The urge to collect caterpillars is so strong 152 00:17:13,327 --> 00:17:17,115 that they'll pick them up anywhere. Watch this. 153 00:17:26,007 --> 00:17:30,239 She has already laid a long yellow egg on the first caterpillar. 154 00:17:32,287 --> 00:17:36,246 When the tunnel is full, she seals it with special care. 155 00:17:47,767 --> 00:17:51,362 She uses a grain of gravel like a pneumatic ram, 156 00:17:51,527 --> 00:17:53,995 vibrating it by buzzing her wing muscles - 157 00:17:54,167 --> 00:17:57,637 one of the few instances of an insect using a tool. 158 00:18:00,687 --> 00:18:03,155 In a few days, when the egg hatches, 159 00:18:03,327 --> 00:18:05,966 the grub will find fresh meat awaiting it. 160 00:18:07,447 --> 00:18:11,235 These cabbage white caterpillars are also doomed. 161 00:18:11,407 --> 00:18:14,240 Another species of wasp injects them - 162 00:18:14,407 --> 00:18:18,002 not with paralysing poison, but with eggs. 163 00:18:32,087 --> 00:18:37,719 Day after day, the caterpillars grow and mature, apparently unaffected. 164 00:18:37,887 --> 00:18:41,277 But inside them the wasp eggs are developing. 165 00:19:10,167 --> 00:19:14,240 Having fed so richly on the entrails of their caterpillar host, 166 00:19:14,407 --> 00:19:18,958 the wasp grubs are ready to pupate as soon as they emerge. 167 00:19:19,127 --> 00:19:22,563 They start straightaway to spin their silken cocoons. 168 00:19:26,887 --> 00:19:30,323 Ten days later, they have become adult wasps, 169 00:19:30,487 --> 00:19:33,604 and are themselves searching for caterpillars. 170 00:19:39,687 --> 00:19:43,123 Just where eggs are placed can be very important. 171 00:19:43,287 --> 00:19:47,724 These mosquitoes in Trinidad deposit theirs on the surface of water, 172 00:19:47,887 --> 00:19:50,003 where they float like rafts. 173 00:19:55,247 --> 00:19:57,124 The females signal with their legs, 174 00:19:57,287 --> 00:20:01,917 perhaps warning other flying females that this place is already taken. 175 00:20:06,007 --> 00:20:08,680 They lay in tiny pools of standing water 176 00:20:08,847 --> 00:20:11,759 and particularly favour nut shells. 177 00:20:21,367 --> 00:20:24,723 Heavy raindrops might sink the tiny rafts. 178 00:20:24,887 --> 00:20:29,199 If there is a shower, the adults row the eggs to shelter. 179 00:20:30,287 --> 00:20:33,677 When the young hatch, they drop from the bottom of the raft 180 00:20:33,847 --> 00:20:36,315 and swim down to start collecting food. 181 00:20:47,527 --> 00:20:51,406 These fish also care for their eggs with great solicitude. 182 00:20:51,567 --> 00:20:54,161 They are Midas cichlids from Nicaragua. 183 00:20:55,367 --> 00:20:57,597 0nce a pair has selected their territory, 184 00:20:57,767 --> 00:21:00,520 the male digs a small pit in the ground. 185 00:21:15,487 --> 00:21:17,284 The golden-coloured female, 186 00:21:17,447 --> 00:21:21,326 meanwhile, has meticulously cleaned the surface of a rock with her mouth 187 00:21:21,487 --> 00:21:26,242 and now she's moving slowly over it, laying lines of sticky eggs. 188 00:21:32,087 --> 00:21:34,123 As she completes each pass, 189 00:21:34,287 --> 00:21:37,882 the male follows behind and discharges his sperm. 190 00:21:44,687 --> 00:21:49,807 Within an hour, there are as many as 2,000 fertilised eggs on the rock wall. 191 00:21:51,767 --> 00:21:54,964 Three days later, they begin to hatch. 192 00:22:04,287 --> 00:22:08,041 The female gently picks off the wriggling young. 193 00:22:15,527 --> 00:22:19,156 In they go - into the cradle that the male dug for them, 194 00:22:19,327 --> 00:22:21,602 even before they were spawned. 195 00:22:34,287 --> 00:22:36,357 They have a sticky pad on their heads 196 00:22:36,527 --> 00:22:39,405 that enables them to stay attached to the gravel. 197 00:22:39,567 --> 00:22:41,762 They can hardly yet be called fish. 198 00:22:41,927 --> 00:22:46,443 They have no mouths and nourish themselves from a speck of yolk within their body 199 00:22:46,607 --> 00:22:48,677 that is bigger than they are. 200 00:22:49,087 --> 00:22:52,284 As they wriggle, they create a current that brings them oxygen. 201 00:22:54,087 --> 00:22:57,238 Their eyes have now developed and much of their yolk has been used up 202 00:22:57,407 --> 00:22:59,875 in building their growing bodies. 203 00:23:01,687 --> 00:23:03,678 They begin to swim. 204 00:23:12,167 --> 00:23:15,762 All the time their parents remain above them, 205 00:23:15,927 --> 00:23:19,317 to defend them against anything that might make a meal of them. 206 00:23:21,607 --> 00:23:23,643 Now their yolk is almost gone 207 00:23:23,807 --> 00:23:26,958 and they must sustain themselves in a different way. 208 00:23:27,127 --> 00:23:29,197 Five days after becoming free-swimming, 209 00:23:29,367 --> 00:23:32,837 they start to graze over the bodies of their parents. 210 00:23:33,007 --> 00:23:36,920 The adults are producing a nutritious slime from their skins, 211 00:23:37,087 --> 00:23:42,445 so their cloud of babies can find food without straying too far away. 212 00:23:59,087 --> 00:24:02,397 Many parents put their own personal safety at risk 213 00:24:02,567 --> 00:24:04,637 in order to protect their eggs. 214 00:24:04,807 --> 00:24:10,200 In Brazil, a sawfly crouches over her eggs for three long weeks, 215 00:24:10,367 --> 00:24:13,677 threatening any intruder with an aggressive buzz, 216 00:24:13,847 --> 00:24:17,601 flicking her wings with which she will strike if necessary, 217 00:24:17,767 --> 00:24:20,679 and displaying her formidable jaws. 218 00:24:24,167 --> 00:24:28,365 Even an assassin bug knows when it has met its match. 219 00:24:33,007 --> 00:24:34,998 As a result of her dedication, 220 00:24:35,167 --> 00:24:38,523 90% of her eggs survive to hatch. 221 00:24:38,687 --> 00:24:41,326 Even then, she won't desert. 222 00:24:41,487 --> 00:24:44,445 She stays with her caterpillars to protect them. 223 00:24:45,007 --> 00:24:48,636 But a single guard can't be everywhere at the same time. 224 00:24:48,807 --> 00:24:53,403 So her young, instead of scattering to feed, remain together. 225 00:25:13,767 --> 00:25:16,486 Bigger parents have similar problems. 226 00:25:16,647 --> 00:25:18,763 Snow geese in the Russian Arctic 227 00:25:18,927 --> 00:25:22,636 have to be just as vigilant if they are to rear their babies. 228 00:25:29,687 --> 00:25:31,678 Eggs packed with yolk 229 00:25:31,847 --> 00:25:34,759 are splendid food and tempt a lot of thieves. 230 00:25:40,607 --> 00:25:43,917 For Arctic foxes, this is a time of plenty. 231 00:25:44,087 --> 00:25:47,602 Hundreds of eggs are lying around on the cold tundra. 232 00:25:47,767 --> 00:25:50,235 But they're all defended. 233 00:26:48,607 --> 00:26:50,245 Got one! 234 00:27:02,687 --> 00:27:04,678 But why doesn't it eat it? 235 00:27:11,367 --> 00:27:13,801 This glut of eggs won't be here for long. 236 00:27:13,967 --> 00:27:17,323 With so many around, it's better to hide away the swag 237 00:27:17,487 --> 00:27:19,955 to be eaten later and go back for more. 238 00:27:20,127 --> 00:27:22,118 In the cold, near-freezing earth, 239 00:27:22,287 --> 00:27:25,757 an egg will remain fresh and edible for a long time. 240 00:27:28,967 --> 00:27:32,403 Those still in the nest, kept warm by their parents, 241 00:27:32,567 --> 00:27:35,035 are beginning the universal process 242 00:27:35,207 --> 00:27:38,279 that is still one of the most mysterious events in life. 243 00:27:39,007 --> 00:27:41,760 The greater part of a bird's egg - the yolk, 244 00:27:41,927 --> 00:27:44,282 is food for the developing young. 245 00:27:44,447 --> 00:27:47,564 0n its surface, beneath the cushion of clear albumen, 246 00:27:47,727 --> 00:27:50,321 lies just one fertile cell. 247 00:27:50,487 --> 00:27:55,163 In the sustained warmth, it grows, divides and grows again. 248 00:27:56,167 --> 00:27:59,842 Within two days, a beating heart has appeared. 249 00:28:00,007 --> 00:28:02,282 Blood vessels spread around the yolk, 250 00:28:02,447 --> 00:28:06,520 collecting its nourishment and transporting it to the embryo. 251 00:28:17,927 --> 00:28:21,806 Twelve days later, the little creature has legs. 252 00:28:21,967 --> 00:28:24,276 And beneath the tracery of blood vessels, 253 00:28:24,447 --> 00:28:26,802 the tiny head is virtually complete. 254 00:28:38,607 --> 00:28:42,282 15 days, and feathers are beginning to sprout. 255 00:28:48,607 --> 00:28:51,440 21 days after incubation started, 256 00:28:51,607 --> 00:28:54,405 the moment for hatching has arrived. 257 00:29:10,527 --> 00:29:12,802 (CHIRPING) 258 00:29:39,007 --> 00:29:43,956 0nce dried, the downy feathers help the tiny body to retain its warmth. 259 00:29:44,127 --> 00:29:47,836 The chick is ready to start a new stage in its life. 260 00:29:53,607 --> 00:29:57,725 There are few more formidable mothers than this one. 261 00:29:59,927 --> 00:30:06,275 The salt water crocodile of Australia builds her nest on a river bank. 262 00:30:19,007 --> 00:30:22,397 She digs a deep hole in the peaty soil. 263 00:30:30,007 --> 00:30:33,317 In it, she lays several dozen eggs. 264 00:30:36,527 --> 00:30:39,724 These eggs have one strange characteristic - 265 00:30:39,887 --> 00:30:41,878 even though they have left her body, 266 00:30:42,047 --> 00:30:45,437 the sex of the babies within them is not yet fixed. 267 00:30:45,607 --> 00:30:48,326 It will depend on how she looks after them. 268 00:30:54,687 --> 00:30:58,646 She covers them with dead leaves which, as they decay, 269 00:30:58,807 --> 00:31:02,197 will produce the heat the eggs need in order to develop. 270 00:31:08,287 --> 00:31:12,599 And it is this that determines the sex of the babies. 271 00:31:16,527 --> 00:31:19,803 At 30 degrees centigrade, they will all be female. 272 00:31:19,967 --> 00:31:23,482 Two degrees higher, and they will be all male. 273 00:31:23,647 --> 00:31:27,276 In between, they will be exactly half and half. 274 00:31:27,447 --> 00:31:30,598 If the nest temperature rises two degrees higher still, 275 00:31:30,767 --> 00:31:34,123 then a third of the eggs will be male, a third female, 276 00:31:34,287 --> 00:31:36,517 and a third will die. 277 00:31:39,287 --> 00:31:42,404 Their emergence is less arduous than that of a baby bird, 278 00:31:42,567 --> 00:31:46,446 for reptilian shells are leathery and easily broken. 279 00:31:58,167 --> 00:32:00,158 The babies are so well formed 280 00:32:00,327 --> 00:32:03,683 that even before they leave the shell, they can bite. 281 00:32:14,087 --> 00:32:16,999 The technique of warming eggs with rotting leaves 282 00:32:17,167 --> 00:32:21,365 has been brought to a fine art by the mallee fowl of southern Australia. 283 00:32:23,167 --> 00:32:26,523 A pair build themselves a huge mound of sand. 284 00:32:26,687 --> 00:32:29,281 In its heart lies a layer of leaves. 285 00:32:30,607 --> 00:32:34,520 Every few days throughout the breeding season, the female comes to lay 286 00:32:34,687 --> 00:32:38,521 and the male kicks away sand to expose that layer. 287 00:32:39,487 --> 00:32:42,843 Her egg, compared with her body, is gigantic, 288 00:32:43,007 --> 00:32:46,204 and as soon as she has produced it, the male covers it over. 289 00:32:50,087 --> 00:32:52,999 Now the temperature must be carefully monitored. 290 00:32:53,167 --> 00:32:55,556 The male measures it with its beak. 291 00:32:59,607 --> 00:33:01,598 Even when visitors approach, 292 00:33:01,767 --> 00:33:04,964 he stays bravely beside the mound to keep an eye on things. 293 00:33:07,087 --> 00:33:10,523 If the mound is too cold, he piles sand on top. 294 00:33:10,687 --> 00:33:13,679 If it's too hot, he kicks it away. 295 00:33:15,607 --> 00:33:19,839 So obsessed is he with managing this mound... 296 00:33:20,007 --> 00:33:22,237 that if someone interferes with it, 297 00:33:22,407 --> 00:33:26,241 his first instinct is to put that right. 298 00:33:28,007 --> 00:33:31,556 If I flick sand off, he flicks it back. 299 00:34:00,167 --> 00:34:03,716 The chick has to dig its own way up through the sand. 300 00:34:03,887 --> 00:34:08,324 It's able to do so because that huge egg contains so much yolk 301 00:34:08,487 --> 00:34:12,765 that the chick could stay in it, gathering strength, for 49 days. 302 00:34:12,927 --> 00:34:16,317 It'll be able to fly within 24 hours. 303 00:34:18,287 --> 00:34:19,766 In the trees above, 304 00:34:19,927 --> 00:34:23,886 there are chicks that are having a much harder, hungrier time. 305 00:34:25,687 --> 00:34:29,521 The crested hawks laid three eggs, each a day apart, 306 00:34:29,687 --> 00:34:32,076 but they started incubation when the first arrived. 307 00:34:32,247 --> 00:34:35,683 So the first laid was the first to hatch, 308 00:34:35,847 --> 00:34:38,281 and that chick was the first to get a meal. 309 00:34:38,447 --> 00:34:39,880 With such a start, 310 00:34:40,047 --> 00:34:42,800 it's already bigger than the two younger ones. 311 00:34:44,167 --> 00:34:47,398 The parents work hard bringing food. 312 00:34:58,527 --> 00:35:01,678 But the eldest chick nearly always gets it. 313 00:35:01,847 --> 00:35:04,964 To him that hath, it shall be given. 314 00:35:08,607 --> 00:35:12,759 The youngest - the smallest - stands little chance of a mouthful 315 00:35:12,927 --> 00:35:16,476 as long as either of the bigger ones are in the least hungry. 316 00:35:24,167 --> 00:35:27,239 0nce again, the youngest gets nothing. 317 00:35:38,167 --> 00:35:40,522 And now it's dead. 318 00:35:43,727 --> 00:35:46,036 This was a gamble by the adults. 319 00:35:46,207 --> 00:35:48,277 Had it been a specially good year, 320 00:35:48,447 --> 00:35:52,440 then they would have been ready to take advantage of it and rear three chicks. 321 00:35:52,607 --> 00:35:57,078 But this year, as in most years, the gamble didn't pay off. 322 00:36:10,607 --> 00:36:13,917 The little body is not totally wasted. 323 00:36:14,087 --> 00:36:17,875 Some of its flesh is fed to the survivors. 324 00:36:34,447 --> 00:36:38,565 Animals care for their eggs and young in many different ways, 325 00:36:38,727 --> 00:36:42,766 but peripatus - a curious creature, half worm, half centipede - 326 00:36:42,927 --> 00:36:45,919 provides the ultimate in parental protection. 327 00:36:46,887 --> 00:36:48,764 The eggs develop inside the female 328 00:36:48,927 --> 00:36:51,521 and stay there until they're so advanced 329 00:36:51,687 --> 00:36:54,440 that they can survive without the protection of a shell. 330 00:37:27,847 --> 00:37:31,965 So the young peripatus gets a good start in life. 331 00:37:35,687 --> 00:37:38,759 No waiting around defenceless, imprisoned in an egg. 332 00:37:38,927 --> 00:37:43,318 It's able to feed and hide itself just as soon as it leaves Mother. 333 00:37:45,167 --> 00:37:49,479 All kinds of creatures have, independently, adopted this strategy. 334 00:37:51,447 --> 00:37:52,880 The tsetse fly. 335 00:37:53,047 --> 00:37:56,403 The bigger the young, the fewer a female can produce, 336 00:37:56,567 --> 00:37:59,877 and the tsetse fly's baby is a whopper. 337 00:38:15,447 --> 00:38:17,881 In the whole of her six-month life, 338 00:38:18,047 --> 00:38:21,926 she can only give birth to a dozen of these plump grubs. 339 00:38:22,087 --> 00:38:24,885 It crawls away to turn into a pupa 340 00:38:25,047 --> 00:38:28,084 from which the adult fly will quickly emerge. 341 00:38:29,447 --> 00:38:33,281 These baby beetles are also long past the egg stage. 342 00:38:33,447 --> 00:38:36,120 Their transformation into an adult 343 00:38:36,287 --> 00:38:39,484 will also take place inside the protective shell of a pupa, 344 00:38:39,647 --> 00:38:42,878 but meanwhile they work as small eating machines, 345 00:38:43,047 --> 00:38:47,245 gathering the food necessary to construct an adult body. 346 00:38:57,767 --> 00:39:02,079 These gnat grubs avoid the pupal stage altogether. 347 00:39:02,247 --> 00:39:06,240 They feed on mushrooms which disappear after a few days. 348 00:39:06,407 --> 00:39:09,763 So the grubs must eat all they can while they have the chance. 349 00:39:09,927 --> 00:39:14,284 To do that, they reproduce even before they become adult. 350 00:39:14,447 --> 00:39:16,915 The unfertilised eggs of the female grub 351 00:39:17,087 --> 00:39:19,203 begin to develop within her body. 352 00:39:19,367 --> 00:39:22,916 They feed by browsing on their mother's internal organs, 353 00:39:23,087 --> 00:39:28,764 so that eventually she herself is reduced by her own young to a sausage skin, 354 00:39:28,927 --> 00:39:34,399 through which 30 or so grubs force their way - coming out at both ends. 355 00:39:35,447 --> 00:39:37,278 Each is a clone - 356 00:39:37,447 --> 00:39:40,007 genetically identical to its single parent. 357 00:39:40,167 --> 00:39:44,080 Each of these 30 can do the same trick in six days' time. 358 00:39:44,247 --> 00:39:50,516 In six weeks, if there were enough mushrooms, there could be 20,000 million - all identical. 359 00:39:52,767 --> 00:39:55,725 A mother sea louse, a kind of crustacean, 360 00:39:55,887 --> 00:39:59,880 also commits suicide in order to launch the next generation. 361 00:40:01,447 --> 00:40:06,521 The mass of babies within her tiny shell have consumed so much of her energies 362 00:40:06,687 --> 00:40:11,158 that as the last leaves, she, exhausted, will die. 363 00:40:19,767 --> 00:40:22,122 It's not only females that can give birth. 364 00:40:22,287 --> 00:40:25,882 A few exceptional males also get pregnant. 365 00:40:27,087 --> 00:40:30,284 The male pipefish develops a sticky underside 366 00:40:30,447 --> 00:40:32,403 where the female deposits her eggs. 367 00:40:32,567 --> 00:40:36,196 Flaps of skin grow round them, and when the time comes, 368 00:40:36,367 --> 00:40:40,679 the young wriggle out to take their chances in a dangerous world. 369 00:41:06,847 --> 00:41:09,725 0nce they leave their father's body, 370 00:41:09,887 --> 00:41:13,641 they're easily picked off by hungry sticklebacks. 371 00:41:17,167 --> 00:41:20,876 The babies who remain in their mother's body for the longest time, 372 00:41:21,047 --> 00:41:24,119 and who are cared for in the most comprehensive way of all, 373 00:41:24,287 --> 00:41:26,403 are those of mammals. 374 00:41:26,567 --> 00:41:29,877 These female sea lions mated a year ago. 375 00:41:30,047 --> 00:41:33,756 The fertilised egg fixed itself to the womb wall, 376 00:41:33,927 --> 00:41:37,761 tapped the mother's blood supply and grew, month after month. 377 00:41:37,927 --> 00:41:40,236 Now that long development is over 378 00:41:40,407 --> 00:41:44,241 and the labour of entering the outside world has begun. 379 00:41:57,767 --> 00:42:01,362 The membranes that held the fluid within which the infant swam 380 00:42:01,527 --> 00:42:05,679 while it was within its mother's body still partially enclose it. 381 00:42:36,207 --> 00:42:39,483 For all mammal babies, the shock of leaving the warm, 382 00:42:39,687 --> 00:42:42,406 totally protected haven of a mother's body 383 00:42:42,567 --> 00:42:47,846 and entering the harsh, relatively cold, danger-filled world outside 384 00:42:48,007 --> 00:42:50,157 is inevitably traumatic. 385 00:42:56,247 --> 00:43:00,604 Baby antelopes, whose parents have to travel continuously to find food, 386 00:43:00,767 --> 00:43:03,725 must be as fully developed as possible, 387 00:43:03,887 --> 00:43:08,039 for they need to walk within hours, groggy though they may be. 388 00:43:29,927 --> 00:43:33,124 Chinchillas are born in the high Andes. 389 00:43:33,287 --> 00:43:35,847 Their world is a very cold one. 390 00:43:36,007 --> 00:43:40,683 Their mothers make no nest for them, so they are born fully furred. 391 00:43:40,847 --> 00:43:43,998 Were they not, they might freeze to death. 392 00:44:09,847 --> 00:44:14,557 Hyena babies need not be so advanced, for they are born within a den, 393 00:44:14,727 --> 00:44:18,037 where their powerful mother has little difficulty in defending them. 394 00:44:18,207 --> 00:44:20,482 She can get rid of their bulk and weight 395 00:44:20,647 --> 00:44:24,196 while they're still at an early stage of their development. 396 00:44:24,367 --> 00:44:27,040 As soon as they emerge, like all young mammals, 397 00:44:27,207 --> 00:44:30,836 they must find their mother's teat and start to suckle. 398 00:44:46,687 --> 00:44:50,885 Perhaps the trickiest mammal birth of all is that of the bat. 399 00:44:51,047 --> 00:44:54,164 For it, after all, has to arrive in this world 400 00:44:54,327 --> 00:44:57,717 while its mother hangs upside-down from the ceiling. 401 00:45:02,287 --> 00:45:05,245 Whatever happens, the baby mustn't fall. 402 00:45:05,407 --> 00:45:08,319 While mother hangs acrobatically from one leg, 403 00:45:08,487 --> 00:45:12,082 she stretches out the other so that the web connecting it to the tail 404 00:45:12,247 --> 00:45:15,717 forms a cradle in which to catch her newborn babe. 405 00:45:27,167 --> 00:45:31,718 0ne infant is all that a bat of this species can produce at one time. 406 00:45:31,887 --> 00:45:35,357 Her mammalian nature dictates that she keeps it within her body 407 00:45:35,527 --> 00:45:37,165 until it's well developed, 408 00:45:37,327 --> 00:45:40,239 and even one is a very heavy load when flying. 409 00:45:40,407 --> 00:45:45,162 Now she feeds it from her own body with that special food - milk - 410 00:45:45,327 --> 00:45:48,239 which is all that a newly-born mammal can digest. 411 00:45:48,407 --> 00:45:51,319 The arrival in the world of this baby, 412 00:45:51,487 --> 00:45:53,921 so tenderly nurtured by its mother, 413 00:45:54,087 --> 00:45:58,603 could hardly be more different from that of so many creatures that live in the sea. 414 00:46:03,167 --> 00:46:05,601 Birth for the Christmas Island crabs 415 00:46:05,767 --> 00:46:07,917 is a comparatively protracted affair. 416 00:46:08,087 --> 00:46:11,318 For 28 days they float helplessly in the sea, 417 00:46:11,487 --> 00:46:15,321 slowly increasing the size and complexity of their body, 418 00:46:15,487 --> 00:46:19,196 until at last they are just recognisable as miniature crabs, 419 00:46:19,367 --> 00:46:21,961 but very few of them live as long as that. 420 00:46:22,127 --> 00:46:26,996 Fish eat them in huge quantities, currents sweep them away into the open ocean. 421 00:46:27,167 --> 00:46:33,003 So, most years, the entire spawning of billions is totally lost. 422 00:46:33,167 --> 00:46:37,399 But almost miraculously, about one year in five, 423 00:46:37,567 --> 00:46:41,276 a few hundred thousand appear in the waves off the coasts 424 00:46:41,447 --> 00:46:44,564 where they first fell into the water as eggs. 425 00:46:44,727 --> 00:46:47,321 Then these little creatures, no bigger than ants, 426 00:46:47,487 --> 00:46:49,717 valiantly struggle ashore. 427 00:46:50,927 --> 00:46:53,566 A single female crab, during her lifetime, 428 00:46:53,727 --> 00:46:55,797 may produce a million eggs. 429 00:46:55,967 --> 00:46:57,605 If just one survives, 430 00:46:57,767 --> 00:47:01,123 then she may be just as successful as a bat, a sea lion, 431 00:47:01,287 --> 00:47:06,566 or any other creature that each year lavishes its care on a single baby. 432 00:47:08,687 --> 00:47:11,485 So, in a multitude of different ways, 433 00:47:11,647 --> 00:47:14,115 new lives appear on Earth, 434 00:47:14,287 --> 00:47:17,643 and each starts off on its own individual odyssey. 435 00:47:17,807 --> 00:47:20,560 They've survived the first of their trials, 436 00:47:20,727 --> 00:47:22,843 but they'll have to face many more 437 00:47:23,007 --> 00:47:27,444 before, in turn, they too will have a chance to give birth.