1 00:00:07,840 --> 00:00:10,800 (THEME MUSIC) 2 00:00:34,960 --> 00:00:37,600 DAVID ATTENBOROUGH: One quarter of all the land on Earth 3 00:00:37,680 --> 00:00:41,440 is covered by a single, remarkable type of plant. 4 00:00:47,800 --> 00:00:51,960 Almost indestructible, it can grow half a metre a day. 5 00:00:58,560 --> 00:01:02,000 And be tall enough to hide a giant. 6 00:01:06,160 --> 00:01:08,120 That plant is grass. 7 00:01:08,200 --> 00:01:11,960 And the world it creates is truly unique. 8 00:01:25,520 --> 00:01:29,000 The grass in northern India is the tallest on the planet, 9 00:01:29,080 --> 00:01:33,480 home to some of the most impressive creatures to tread the Earth. 10 00:01:48,240 --> 00:01:50,600 These are the good times 11 00:01:50,680 --> 00:01:54,560 but in just a few months, all this fresh growth will be gone 12 00:01:54,640 --> 00:01:57,920 and the animals will be forced to move on. 13 00:02:00,560 --> 00:02:02,280 That is the way things are 14 00:02:02,360 --> 00:02:05,040 on grasslands across the planet. 15 00:02:08,840 --> 00:02:13,280 A cycle of abundance, destruction and rebirth 16 00:02:13,360 --> 00:02:15,680 that affects every creature that lives here. 17 00:02:23,000 --> 00:02:25,200 (ELEPHANTS GRUNTING) 18 00:02:30,640 --> 00:02:35,600 The largest grassland on Earth, the vast Eurasian Steppe, 19 00:02:35,680 --> 00:02:38,960 stretches one third of the way around our planet. 20 00:02:43,360 --> 00:02:48,520 Spring rain has brought fresh grass, and with it, new life. 21 00:02:52,760 --> 00:02:57,600 A relic from the Ice Age, a baby Saiga antelope, 22 00:02:57,680 --> 00:02:59,520 just three hours old. 23 00:03:02,680 --> 00:03:05,160 His only company, his twin. 24 00:03:06,200 --> 00:03:07,880 Until they can stand, 25 00:03:07,960 --> 00:03:10,880 their mother has left them hidden in the grass. 26 00:03:18,520 --> 00:03:22,280 They should be safe as long as they remain quiet. 27 00:03:24,640 --> 00:03:25,600 (CALLS) 28 00:03:27,440 --> 00:03:30,440 For these calves, the clock is already ticking. 29 00:03:31,920 --> 00:03:33,800 Their herd will soon be moving on, 30 00:03:33,880 --> 00:03:36,440 seeking the freshest new grass. 31 00:03:40,240 --> 00:03:41,480 (CALLS) 32 00:03:53,840 --> 00:03:58,440 Their lanky legs are a sure sign that they're built for a life on the move. 33 00:04:22,760 --> 00:04:25,680 Saiga always give birth to twins, 34 00:04:25,760 --> 00:04:29,200 so their numbers grow rapidly just when grass is plentiful. 35 00:04:32,680 --> 00:04:36,240 Their bizarrely shaped nose can detect fresh growth 36 00:04:36,320 --> 00:04:38,200 from hundreds of kilometres away. 37 00:04:42,200 --> 00:04:43,960 (SAIGAS BAWLING) 38 00:04:50,080 --> 00:04:53,400 The young twins will now begin the nomadic life 39 00:04:53,480 --> 00:04:57,560 they share with most animals on the world's open plains. 40 00:05:12,160 --> 00:05:14,040 (THUNDER RUMBLING) 41 00:05:18,760 --> 00:05:24,320 Grasslands occur where rain is too sporadic for forests to exist. 42 00:05:34,480 --> 00:05:37,920 The rain that a grassland needs to survive for a year 43 00:05:38,000 --> 00:05:40,240 might arrive all at once. 44 00:05:44,120 --> 00:05:45,160 (LIGHTNING CRACKS) 45 00:06:00,760 --> 00:06:05,840 Storms like these can release 30 centimetres of rain in 24 hours. 46 00:06:05,920 --> 00:06:07,360 (HEAVY RAINFALL) 47 00:06:16,560 --> 00:06:19,320 Not much fun if you're out in it. 48 00:06:30,960 --> 00:06:34,120 Eventually the earth can't soak up any more... 49 00:06:35,040 --> 00:06:37,040 (THUNDER CRACKING) 50 00:06:37,120 --> 00:06:40,680 ...and the grassland undergoes a radical change. 51 00:06:41,440 --> 00:06:43,200 (WATER FLOWING) 52 00:06:47,360 --> 00:06:51,920 Many plants would drown here, but grasses thrive. 53 00:06:54,880 --> 00:06:57,120 They grow so fast, their leaves quickly 54 00:06:57,200 --> 00:06:59,840 rise above the water and into the sunlight. 55 00:07:04,160 --> 00:07:06,360 Here in southern Africa, 56 00:07:06,440 --> 00:07:10,720 water transforms one of the most remarkable grasslands on Earth, 57 00:07:13,000 --> 00:07:14,360 the Okavango. 58 00:07:17,720 --> 00:07:22,040 Every year, 8,000 square kilometres of grassland are flooded. 59 00:07:30,000 --> 00:07:34,160 For one pride of lions, this poses a major problem. 60 00:07:36,480 --> 00:07:38,920 There may be plenty of prey around, 61 00:07:39,000 --> 00:07:41,880 but lions struggle to run it down in water. 62 00:07:48,720 --> 00:07:51,560 The pride has three-month-old cubs. 63 00:07:51,640 --> 00:07:53,880 They've never seen water before. 64 00:07:53,960 --> 00:07:55,720 (CUBS MEOWING) 65 00:07:57,480 --> 00:08:00,080 If their mothers don't make a kill soon, 66 00:08:00,160 --> 00:08:02,880 the cubs might not survive the week. 67 00:08:03,640 --> 00:08:04,720 (YOWLS) 68 00:08:12,160 --> 00:08:17,720 But fuelled by the flood, the eruption of grass attracts new possible prey. 69 00:08:20,960 --> 00:08:23,880 Buffalo arrive in herds 2,000 strong. 70 00:08:30,320 --> 00:08:31,760 (GRUNTS) 71 00:08:31,840 --> 00:08:34,680 Powerful, aggressive and united, 72 00:08:34,760 --> 00:08:37,720 they're the most dangerous animal a lion can face. 73 00:09:01,880 --> 00:09:02,840 (BUFFALO GRUNTS) 74 00:09:15,040 --> 00:09:17,120 The biggest bulls don't run. 75 00:09:19,520 --> 00:09:23,080 They're simply too huge to be scared of lions. 76 00:09:25,280 --> 00:09:30,320 At 900 kilos, he weighs more than all five lionesses combined. 77 00:09:34,600 --> 00:09:37,160 The pride do have numbers on their side, 78 00:09:38,360 --> 00:09:41,520 but one sweep of his horns could be deadly. 79 00:09:55,320 --> 00:09:57,160 One distracts the bull up front 80 00:09:57,240 --> 00:09:59,760 while her sisters attack from behind. 81 00:10:10,480 --> 00:10:12,920 The cats must somehow topple the buffalo, 82 00:10:13,000 --> 00:10:16,160 but with swamp under foot, they can't get any traction. 83 00:10:59,200 --> 00:11:00,760 The bull is weakening, 84 00:11:01,680 --> 00:11:03,760 but the lions are tiring, too. 85 00:11:08,840 --> 00:11:12,600 It's now a battle of will as much as strength. 86 00:11:15,440 --> 00:11:19,240 To live, the bull must somehow shake off the lioness. 87 00:11:56,880 --> 00:11:58,520 The bull is wounded, 88 00:11:58,600 --> 00:12:01,760 but thanks to his thick hide, he will recover. 89 00:12:08,160 --> 00:12:11,480 For the pride, these are hungry times. 90 00:12:11,560 --> 00:12:12,880 (CUB WHIMPERS) 91 00:12:19,600 --> 00:12:24,600 But, ultimately, once the water recedes, there will be new life, 92 00:12:25,360 --> 00:12:27,680 and new food to benefit all. 93 00:12:36,680 --> 00:12:40,600 In the right conditions, grasses have the extraordinary ability 94 00:12:40,680 --> 00:12:45,560 to grow from first shoots to flower in a matter of only days. 95 00:12:51,880 --> 00:12:56,360 Grasses become the miniature equivalents of fruiting trees. 96 00:13:01,960 --> 00:13:03,520 (CRICKET CHIRPS) 97 00:13:03,600 --> 00:13:06,120 And for creatures living within the grass, 98 00:13:06,200 --> 00:13:10,440 this is a landscape as vast and towering as any rainforest. 99 00:13:15,560 --> 00:13:18,640 An excellent place to build a tiny tree house 100 00:13:20,960 --> 00:13:22,480 for a harvest mouse. 101 00:13:26,640 --> 00:13:28,240 (SQUEAKS) 102 00:13:34,240 --> 00:13:38,200 During summer, European meadowlands are full of food, 103 00:13:41,720 --> 00:13:43,680 but only for those that can reach it. 104 00:13:59,760 --> 00:14:01,400 (STEM CRACKS) 105 00:14:02,360 --> 00:14:05,400 Climbing grass is harder than climbing trees, 106 00:14:05,480 --> 00:14:08,840 not least because their stems just won't stay still. 107 00:14:16,480 --> 00:14:19,840 Her prehensile tail acts like a fifth limb, 108 00:14:19,920 --> 00:14:23,560 so she's as agile as a monkey clambering around in a tree. 109 00:14:25,280 --> 00:14:26,920 (STEM CREAKS) 110 00:14:31,640 --> 00:14:33,200 And just as well, 111 00:14:33,280 --> 00:14:35,680 for the best food in this tiny forest 112 00:14:35,760 --> 00:14:37,680 is at the very top of its canopy. 113 00:14:48,400 --> 00:14:51,360 Feeding up here, she's exposed. 114 00:14:58,400 --> 00:14:59,880 A barn owl. 115 00:15:30,760 --> 00:15:32,520 Not her finest move... 116 00:15:36,240 --> 00:15:37,560 But it did the trick. 117 00:15:39,760 --> 00:15:43,320 Harvest mice seldom go all the way down to the ground. 118 00:15:46,440 --> 00:15:50,040 It's a tangled and dangerous world down here. 119 00:15:52,480 --> 00:15:54,520 (INSECTS CHITTERING) 120 00:16:02,960 --> 00:16:07,120 But she can read the pattern of the stems overhead like a map, 121 00:16:08,280 --> 00:16:10,440 and so find her way home. 122 00:16:18,200 --> 00:16:20,560 And not a minute too soon. 123 00:16:25,200 --> 00:16:27,440 There are mouths to feed. 124 00:16:36,320 --> 00:16:37,920 (SNIFFS) 125 00:16:40,760 --> 00:16:43,040 Her babies must fatten up quickly. 126 00:16:45,400 --> 00:16:47,960 They need to harvest the summer grasses 127 00:16:48,040 --> 00:16:49,800 while they're still rich with food. 128 00:16:58,160 --> 00:17:03,360 On the African savannah, too, seasonal grasses are filled with life, 129 00:17:03,440 --> 00:17:05,160 but it won't last long. 130 00:17:08,520 --> 00:17:11,960 Carmine bee-eaters are superb aerial hunters, 131 00:17:13,520 --> 00:17:17,200 experts at catching insects in midair. 132 00:17:24,120 --> 00:17:27,640 But they have no way of flushing their prey out of the grass. 133 00:17:35,760 --> 00:17:37,720 (INSECTS CHITTERING) 134 00:17:37,800 --> 00:17:41,480 Once alarmed, most insects stay put. 135 00:17:44,280 --> 00:17:48,040 The bee-eaters need someone to stir things up a bit. 136 00:17:48,120 --> 00:17:49,360 (CALLS) 137 00:17:53,800 --> 00:17:55,320 A Kori bustard. 138 00:18:00,080 --> 00:18:02,480 It's the world's heaviest flying bird, 139 00:18:02,560 --> 00:18:05,560 so it should be bulky enough to kick up some insects. 140 00:18:11,520 --> 00:18:12,920 (INSECT BUZZING) 141 00:18:13,000 --> 00:18:14,120 Bingo! 142 00:18:17,120 --> 00:18:22,400 Until someone else comes along and cramps your style. 143 00:18:26,360 --> 00:18:27,360 (CHIRPS) 144 00:18:28,320 --> 00:18:32,240 Never mind, perhaps there are bigger opportunities ahead. 145 00:18:35,320 --> 00:18:37,080 What about an ostrich? 146 00:18:39,520 --> 00:18:41,040 The heaviest bird of all. 147 00:18:46,880 --> 00:18:50,360 This time there's more than enough transport to go around. 148 00:18:51,960 --> 00:18:54,000 (SQUAWKING) 149 00:19:00,480 --> 00:19:04,040 Soon, almost every ostrich has its own passenger. 150 00:19:12,000 --> 00:19:16,240 But free riders are only tolerated for so long. 151 00:19:22,440 --> 00:19:24,560 What the bee-eaters really need 152 00:19:24,640 --> 00:19:27,720 is a creature so big it won't even notice them. 153 00:19:32,440 --> 00:19:33,800 (GRUNTING) 154 00:19:38,080 --> 00:19:43,200 Nothing cuts a swathe through grass like an African bull elephant. 155 00:19:59,480 --> 00:20:03,600 The trick is to fly as close to the front of the giant as possible. 156 00:20:04,120 --> 00:20:07,480 They only have a split second to grab the prize. 157 00:20:16,840 --> 00:20:21,320 As more insects are stirred up, the competition intensifies. 158 00:20:24,040 --> 00:20:26,120 (FRENZIED CHIRPING) 159 00:20:43,080 --> 00:20:47,320 With summer drawing to a close, the race to stock up is on. 160 00:20:52,760 --> 00:20:57,600 Soon, the grass will wither, and this opportunity will have gone. 161 00:21:07,280 --> 00:21:09,880 As the dry season takes hold, 162 00:21:09,960 --> 00:21:12,840 food becomes increasingly thin on the ground. 163 00:21:15,240 --> 00:21:20,040 Now, only the most specialized predators on the plains can make a living. 164 00:21:25,680 --> 00:21:30,320 She may be spotted like a cheetah, but this cat is no sprinter. 165 00:21:43,040 --> 00:21:48,760 Instead, she has extra-long legs which give her a high vantage point. 166 00:21:59,400 --> 00:22:04,560 But a serval cat's main weapon are enormous radar ears. 167 00:22:04,640 --> 00:22:05,960 (GRASS RUSTLING) 168 00:22:08,760 --> 00:22:12,200 They help her pinpoint prey hiding in the grass. 169 00:22:20,640 --> 00:22:23,640 But the prey she seeks are canny. 170 00:22:27,600 --> 00:22:29,160 Southern vlei rats. 171 00:22:31,880 --> 00:22:35,520 They know that any sustained movement can give them away. 172 00:22:41,080 --> 00:22:43,600 So they move in short bursts. 173 00:22:43,680 --> 00:22:44,880 (RUSTLING) 174 00:22:51,400 --> 00:22:54,920 But even the slightest rustle will give her a clue. 175 00:22:55,000 --> 00:22:56,080 (RUSTLING) 176 00:23:17,160 --> 00:23:18,200 Warm. 177 00:23:24,360 --> 00:23:25,720 (RUSTLING) 178 00:23:27,320 --> 00:23:28,600 (RUSTLES) 179 00:23:30,480 --> 00:23:31,640 Warmer. 180 00:23:45,960 --> 00:23:47,000 Missed. 181 00:24:20,840 --> 00:24:21,800 (RUSTLING) 182 00:24:32,880 --> 00:24:34,400 (ANIMAL CALLS) 183 00:24:43,800 --> 00:24:44,760 (RUSTLING) 184 00:25:01,320 --> 00:25:02,280 (SQUEAKS) 185 00:25:06,240 --> 00:25:09,400 In better times, she could catch 10 a day, 186 00:25:10,920 --> 00:25:15,280 but now, with so few rodents around, she will have to go hungry. 187 00:25:17,600 --> 00:25:22,320 As drought intensifies, life gets tougher for all. 188 00:25:28,960 --> 00:25:32,640 Predators with permanent territories must tough it out, 189 00:25:33,320 --> 00:25:37,360 while most of their prey disappear over the horizon. 190 00:25:38,200 --> 00:25:39,960 (GRUNTING) 191 00:25:41,400 --> 00:25:47,120 To avoid starvation, many grassland animals follow a nomadic way of life. 192 00:25:49,280 --> 00:25:53,480 Over two million wildebeests wander the East African savannahs 193 00:25:53,560 --> 00:25:55,000 chasing the rains. 194 00:26:08,920 --> 00:26:10,920 And they are not alone. 195 00:26:13,320 --> 00:26:14,960 Arriving on the wing, 196 00:26:15,040 --> 00:26:18,560 Jackson's Widowbirds also seek fresh grass. 197 00:26:18,640 --> 00:26:19,800 (CHIRPING) 198 00:26:20,480 --> 00:26:23,840 Although, it's not just food that they're after. 199 00:26:26,000 --> 00:26:26,960 (CHIRPS) 200 00:26:28,520 --> 00:26:30,520 This male wants a mate. 201 00:26:33,800 --> 00:26:37,000 He's grown elaborate breeding plumage for this moment, 202 00:26:38,680 --> 00:26:41,600 but he needs a stage on which to show it off. 203 00:26:46,080 --> 00:26:48,440 By carefully selecting grass blades, 204 00:26:48,520 --> 00:26:51,040 each trimmed to the correct length, 205 00:26:51,120 --> 00:26:53,440 he's creating something very special. 206 00:27:08,200 --> 00:27:10,400 He needs an even surface, 207 00:27:12,600 --> 00:27:14,080 and a centre-piece. 208 00:27:16,800 --> 00:27:18,320 The stage is set. 209 00:27:19,520 --> 00:27:24,280 His bachelor pad is sufficiently neat and tidy to attract a female. 210 00:27:25,880 --> 00:27:27,280 The problem is, 211 00:27:27,360 --> 00:27:28,360 can she see it? 212 00:27:28,440 --> 00:27:29,760 (CHIRPS) 213 00:27:32,360 --> 00:27:33,640 He has competition. 214 00:27:33,720 --> 00:27:35,200 (CHIRPING LOUDLY) 215 00:27:38,080 --> 00:27:39,720 (CHIRPING) 216 00:27:44,040 --> 00:27:48,360 It might take more than a little gardening to impress the ladies. 217 00:27:50,800 --> 00:27:52,640 Jumping is the right idea, 218 00:27:53,800 --> 00:27:56,240 but he's misjudged the height of the grass. 219 00:28:06,240 --> 00:28:08,280 His rival makes it look easy. 220 00:28:31,280 --> 00:28:33,320 Time to raise his game. 221 00:28:38,440 --> 00:28:40,440 (BOTH CHIRPING) 222 00:29:09,000 --> 00:29:11,280 It's not only who jumps the highest, 223 00:29:11,360 --> 00:29:14,000 but who can keep doing so the longest. 224 00:29:22,920 --> 00:29:27,680 Unable to go the distance, his rivals drop out one by one. 225 00:29:32,280 --> 00:29:35,320 Stamina has won him admirers. 226 00:29:36,760 --> 00:29:39,920 Now he can show off his courtship arena 227 00:29:49,440 --> 00:29:52,960 and engage in a little romantic hide-and-seek. 228 00:30:04,920 --> 00:30:07,520 Finally, he's done enough. 229 00:30:19,320 --> 00:30:23,840 The East African savannahs support millions of grazers. 230 00:30:24,800 --> 00:30:28,560 Each year they devour millions of tonnes of grass, 231 00:30:30,440 --> 00:30:32,680 and yet there's one creature here 232 00:30:32,760 --> 00:30:37,760 whose impact is far greater than all these animals combined. 233 00:30:37,840 --> 00:30:39,480 (GRUNTING) 234 00:30:41,560 --> 00:30:44,880 They're found wherever grass grows on the planet, 235 00:30:45,280 --> 00:30:48,560 yet their labours go almost entirely unnoticed. 236 00:30:53,320 --> 00:30:56,280 One of the most remarkable is found here 237 00:30:56,360 --> 00:30:58,840 on the grasslands of South America. 238 00:31:01,680 --> 00:31:03,760 These blades are so tough 239 00:31:03,840 --> 00:31:07,640 that virtually no large grass eaters can stomach them. 240 00:31:08,720 --> 00:31:12,680 Yet they're harvested on an industrial scale... 241 00:31:13,040 --> 00:31:14,320 (CRACKING) 242 00:31:16,360 --> 00:31:19,080 ...by tiny grass cutter ants. 243 00:31:25,960 --> 00:31:28,960 But they themselves can't digest one bit of it. 244 00:31:31,960 --> 00:31:33,480 So, why bother? 245 00:31:37,600 --> 00:31:40,040 The answer is underground, 246 00:31:42,120 --> 00:31:44,400 and it's very ingenious. 247 00:31:48,840 --> 00:31:54,320 Each blade is cut to length and placed into a garden of fungus. 248 00:31:59,120 --> 00:32:02,040 The rotting grass feeds the fungus 249 00:32:02,120 --> 00:32:05,680 and in turn the fungus feeds the ants. 250 00:32:09,120 --> 00:32:11,480 But feeding five million workers 251 00:32:11,560 --> 00:32:13,800 requires intensive agriculture. 252 00:32:16,080 --> 00:32:19,560 Luckily, they are an industrious lot. 253 00:32:23,760 --> 00:32:28,960 This colony alone will collect over half a tonne of grass every year. 254 00:32:32,880 --> 00:32:36,320 With billions of ant colonies across the world's grasslands 255 00:32:36,400 --> 00:32:39,000 all doing exactly the same thing, 256 00:32:39,080 --> 00:32:41,800 that's a mind-boggling amount of grass. 257 00:33:10,080 --> 00:33:14,360 It's estimated that over one third of the grass that grows on Earth 258 00:33:14,440 --> 00:33:17,320 will be harvested by an insect. 259 00:33:23,160 --> 00:33:24,840 In northern Australia, 260 00:33:24,920 --> 00:33:29,120 termites memorialize their industry in sculpture. 261 00:33:37,000 --> 00:33:40,200 These astonishing mounds are three metres tall. 262 00:33:40,760 --> 00:33:43,680 They're always built on a north-south axis, 263 00:33:43,760 --> 00:33:47,200 which is why their builders are called compass termites. 264 00:34:00,640 --> 00:34:03,440 These castles of clay protect their builders 265 00:34:03,520 --> 00:34:06,640 from extremes of heat and seasonal floods 266 00:34:06,720 --> 00:34:09,120 experienced on many grasslands. 267 00:34:20,560 --> 00:34:25,160 Termites manage to do what most grass eaters can't, 268 00:34:25,920 --> 00:34:29,440 break down dead grass and extract the nutrients. 269 00:34:30,600 --> 00:34:34,560 But they themselves can be food for those that can reach them. 270 00:34:35,240 --> 00:34:36,880 (SUCKING) 271 00:34:40,160 --> 00:34:42,240 A half-metre-long tongue 272 00:34:43,360 --> 00:34:45,560 covered in microscopic hooks, 273 00:34:49,080 --> 00:34:53,320 followed by claws longer than those of a velociraptor. 274 00:34:55,360 --> 00:34:56,680 (SNIFFING) 275 00:34:59,320 --> 00:35:02,960 A giant anteater on the plains of South America. 276 00:35:04,080 --> 00:35:05,560 (SLURPING) 277 00:35:07,720 --> 00:35:10,680 It can devour 20,000 insects a day. 278 00:35:16,120 --> 00:35:21,320 Powerful forelegs enable it to rip apart a termite hill with ease. 279 00:35:31,320 --> 00:35:33,960 And as the sun bakes the grass, 280 00:35:34,040 --> 00:35:36,640 the termites face new danger. 281 00:35:45,000 --> 00:35:46,440 (FIRE CRACKLES) 282 00:35:58,520 --> 00:36:02,840 In minutes, fire turns grassland to ash. 283 00:36:16,480 --> 00:36:18,560 But the grasses are not dead. 284 00:36:19,280 --> 00:36:22,120 Their underground stems are unharmed. 285 00:36:25,280 --> 00:36:28,040 Weeks, months may pass, 286 00:36:28,120 --> 00:36:30,840 but eventually the rains will return 287 00:36:30,920 --> 00:36:32,960 and the grass will sprout again. 288 00:36:39,920 --> 00:36:45,280 Some grasslands must endure not only fire, but ice. 289 00:36:50,440 --> 00:36:55,320 As winter approaches, the prairies of North America begin to freeze. 290 00:36:56,360 --> 00:36:57,560 (CRACKING) 291 00:37:05,520 --> 00:37:07,040 (LOW GROWLING) 292 00:37:11,080 --> 00:37:13,760 In summer, bison roamed freely, 293 00:37:13,840 --> 00:37:17,400 almost continuously cropping the abundant green grass. 294 00:37:19,080 --> 00:37:22,720 Now, that grass is not only withered and frozen, 295 00:37:22,800 --> 00:37:24,640 it's about to be buried. 296 00:37:45,880 --> 00:37:50,880 Sixty million tonnes of snow now blanket this herd's territory. 297 00:37:52,480 --> 00:37:53,640 (SNORTING) 298 00:37:54,760 --> 00:37:57,880 Pushing through deep snow is exhausting work, 299 00:37:57,960 --> 00:38:00,880 and the bison are now slowly starving. 300 00:38:07,720 --> 00:38:11,160 Just keeping warm saps huge amounts of energy. 301 00:38:11,840 --> 00:38:13,680 (GROWLS) 302 00:38:17,360 --> 00:38:21,640 Their thick coats can insulate them down to minus 30 Celsius. 303 00:38:22,400 --> 00:38:24,640 It's now minus 40. 304 00:38:27,320 --> 00:38:29,720 The only thing that will keep them alive 305 00:38:29,800 --> 00:38:32,440 is buried beneath a metre of snow. 306 00:38:37,520 --> 00:38:41,240 And that's a problem shared with a surprising neighbour. 307 00:38:58,960 --> 00:39:02,720 The food the fox seeks is also deep beneath the snow. 308 00:39:09,840 --> 00:39:11,680 (GRUNTING) 309 00:39:14,960 --> 00:39:19,840 The survival of both creatures depends on getting through to the ground. 310 00:39:25,280 --> 00:39:28,880 For the bison, it will be a matter of brute strength. 311 00:39:33,600 --> 00:39:38,400 Massive neck muscles enable them to shovel five tonnes of snow a day. 312 00:39:44,600 --> 00:39:47,760 Their light-weight neighbour needs more precision. 313 00:40:07,960 --> 00:40:09,360 (CHEWING) 314 00:40:15,040 --> 00:40:17,800 The bison have reached their goal, 315 00:40:17,880 --> 00:40:20,440 a mouthful of withered grass. 316 00:40:24,160 --> 00:40:26,400 And where the bison have dug, 317 00:40:26,480 --> 00:40:28,840 the fox now spots an opportunity. 318 00:40:37,560 --> 00:40:39,800 Every footstep counts, 319 00:40:42,680 --> 00:40:44,160 but he mustn't break through... 320 00:40:45,200 --> 00:40:46,160 Yet. 321 00:40:49,560 --> 00:40:53,000 He listens carefully to pinpoint his target. 322 00:40:57,280 --> 00:40:58,560 (PATTERING) 323 00:40:58,640 --> 00:40:59,680 It's moving. 324 00:41:17,800 --> 00:41:19,000 (SQUEAKS) 325 00:41:21,320 --> 00:41:22,280 A vole. 326 00:41:24,920 --> 00:41:30,360 Small, but 100 times more nutritious than a mouthful of dried grass. 327 00:41:36,960 --> 00:41:39,360 To get through the winter on these prairies, 328 00:41:39,440 --> 00:41:43,160 sometimes brain beats brawn. 329 00:41:49,640 --> 00:41:52,760 Ultimately, life on all grasslands 330 00:41:52,840 --> 00:41:55,280 depends on the turn of the seasons. 331 00:42:07,640 --> 00:42:09,600 (CRACKING) 332 00:42:19,440 --> 00:42:24,240 Eight hundred kilometres further north than any tree can survive, 333 00:42:24,320 --> 00:42:26,920 grass returns to life. 334 00:42:35,440 --> 00:42:36,520 (CALLS) 335 00:42:37,720 --> 00:42:41,600 Caribou females have journeyed to the far north 336 00:42:41,680 --> 00:42:42,840 to calve. 337 00:42:43,240 --> 00:42:44,280 (CALLS) 338 00:42:46,800 --> 00:42:51,760 Over 70,000 caribou babies will be born in the next few days. 339 00:42:56,240 --> 00:43:01,280 As the calves appear, so too do the leaves of the newly sprouting grass. 340 00:43:04,640 --> 00:43:06,960 And the calves must strengthen quickly. 341 00:43:07,040 --> 00:43:10,320 Within days they will have to keep up with their parents 342 00:43:10,400 --> 00:43:12,440 on a never-ending march. 343 00:43:17,320 --> 00:43:21,840 At one day old, they're already faster than an Olympic sprinter. 344 00:43:23,200 --> 00:43:27,440 They're testing the legs that will carry them thousands of kilometres. 345 00:43:29,040 --> 00:43:31,320 Better to learn their limitations now. 346 00:43:39,440 --> 00:43:40,920 (CALLS) 347 00:43:45,720 --> 00:43:47,760 (CARIBOU GRUNTING) 348 00:43:51,120 --> 00:43:55,360 It may look playful, but there's no harder life on the grasslands 349 00:43:55,440 --> 00:43:58,000 than that facing these infants. 350 00:44:01,480 --> 00:44:03,720 The caribou mothers now join together, 351 00:44:03,800 --> 00:44:07,160 each with an infant exactly the same age. 352 00:44:15,400 --> 00:44:18,760 They're setting off on the greatest overland trek 353 00:44:18,840 --> 00:44:20,800 made by any animal. 354 00:44:43,920 --> 00:44:48,920 But wherever grass eaters travel, predators lie in wait. 355 00:44:50,320 --> 00:44:51,760 (CARIBOU CALLING) 356 00:44:55,680 --> 00:44:59,680 Here they are, Arctic wolves. 357 00:45:06,680 --> 00:45:08,760 They must seize their chance 358 00:45:08,840 --> 00:45:11,200 while the caribou pass through their territory. 359 00:45:43,520 --> 00:45:45,320 (PANTING) 360 00:45:46,880 --> 00:45:51,760 The wolf runs at the herd, trying to flush out the weak or the slow. 361 00:46:01,200 --> 00:46:02,880 A calf is separated. 362 00:46:11,000 --> 00:46:15,880 At full tilt, 60 kilometres an hour, the wolf is just faster. 363 00:46:24,040 --> 00:46:26,400 But the calf has stamina. 364 00:46:56,080 --> 00:46:58,240 Only a few weeks old, 365 00:46:58,320 --> 00:47:01,800 and this calf's will to survive is remarkable. 366 00:47:07,000 --> 00:47:09,000 And it needs to be, 367 00:47:09,080 --> 00:47:12,240 for these young caribou have now started a journey 368 00:47:12,320 --> 00:47:14,520 that will last a lifetime. 369 00:47:17,480 --> 00:47:22,520 Forever chasing the seasonal growth of the grass on which they depend. 370 00:47:31,360 --> 00:47:33,360 Like all grassland creatures, 371 00:47:33,440 --> 00:47:36,440 they are at the mercy of these unpredictable 372 00:47:36,520 --> 00:47:39,240 but ultimately bountiful lands. 373 00:47:45,200 --> 00:47:49,160 Grass can survive some of the harshest conditions on Earth, 374 00:47:49,240 --> 00:47:53,800 flood, fire and frost, and still flourish. 375 00:48:04,000 --> 00:48:07,600 So it is that grasslands provide a stage 376 00:48:07,680 --> 00:48:11,600 for the greatest gatherings of wildlife on planet Earth. 377 00:48:19,560 --> 00:48:20,600 Next time, 378 00:48:21,720 --> 00:48:24,640 we venture to the newest habitat on Earth, 379 00:48:25,200 --> 00:48:26,480 our cities. 380 00:48:27,520 --> 00:48:30,200 To reveal the extraordinary ways 381 00:48:31,000 --> 00:48:34,600 that animals survive in this man-made world. 382 00:48:40,120 --> 00:48:44,600 (ORCHESTRAL MUSIC) 9999 00:00:0,500 --> 00:00:2,00 www.tvsubtitles.net