1 00:00:00,000 --> 00:00:25,000 © anoXmous @ http://thepiratebay.sx/user/Zen_Bud 1 00:00:42,680 --> 00:00:46,850 A third of the land on our planet is desert. 2 00:00:56,060 --> 00:00:59,190 These great scars on the face of the Earth 3 00:00:59,270 --> 00:01:01,110 appear to be lifeless, 4 00:01:01,190 --> 00:01:04,360 but surprisingly none are. 5 00:01:10,870 --> 00:01:14,080 In all of them life manages somehow 6 00:01:14,120 --> 00:01:16,920 to keep a precarious hold. 7 00:01:37,900 --> 00:01:40,480 Not all deserts are hot. 8 00:01:40,860 --> 00:01:44,490 Fifty-mile-an-hour winds blowing in from Siberia 9 00:01:44,570 --> 00:01:48,660 bring snow to the Gobi Desert in Mongolia. 10 00:02:14,480 --> 00:02:18,060 From a summer high of 50 degrees centigrade 11 00:02:18,150 --> 00:02:22,270 the temperature in midwinter can drop to minus 40, 12 00:02:22,360 --> 00:02:26,490 making this one of the harshest deserts of all. 13 00:02:35,410 --> 00:02:40,540 Few animals can survive these extreme changes. 14 00:02:46,880 --> 00:02:49,390 Wild Bactrian camels, 15 00:02:49,470 --> 00:02:52,140 one of the rarest mammals on the planet. 16 00:02:52,220 --> 00:02:54,970 And perhaps the hardiest. 17 00:02:56,140 --> 00:02:58,730 Their biggest problem is the lack of water, 18 00:02:58,810 --> 00:03:00,560 particularly now, in winter, 19 00:03:00,650 --> 00:03:04,110 when the little there is is locked up as ice. 20 00:03:11,120 --> 00:03:15,330 Surprisingly, snow here never melts. 21 00:03:15,490 --> 00:03:20,330 The air is just too cold and too dry for it to do so. 22 00:03:25,460 --> 00:03:29,260 The sun's rays turn it straight into vapour. 23 00:03:29,300 --> 00:03:31,390 It evaporates. 24 00:03:39,350 --> 00:03:42,520 But it is the only source of water, 25 00:03:42,560 --> 00:03:45,650 so Bactrian camels eat it. 26 00:03:46,480 --> 00:03:47,990 Elsewhere in the world 27 00:03:48,070 --> 00:03:54,700 a camel at a waterhole can drink as much as 200 litres during a single visit. 28 00:03:56,620 --> 00:04:00,160 Here the strategy is to take little and often. 29 00:04:00,250 --> 00:04:01,710 And with good reason, 30 00:04:01,790 --> 00:04:05,590 for filling the stomach with snow could be fatal. 31 00:04:11,090 --> 00:04:13,180 The camels must limit themselves 32 00:04:13,260 --> 00:04:17,260 to the equivalent of just 10 litres a day. 33 00:04:33,820 --> 00:04:36,780 Winter is the time for breeding. 34 00:04:41,370 --> 00:04:45,830 This extraordinary performance is a male Bactrian camel's way 35 00:04:45,920 --> 00:04:49,420 of attracting the attention of a passing female. 36 00:04:51,470 --> 00:04:56,010 In summer the camels can't stray far from waterholes. 37 00:04:56,260 --> 00:04:59,850 But now, with mouthfuls of snow lying everywhere 38 00:04:59,890 --> 00:05:03,350 they can travel widely in search of mates. 39 00:05:07,400 --> 00:05:13,650 Today less than a thousand of these desert specialists remain in the wild. 40 00:05:13,740 --> 00:05:19,280 The Gobi, hostile though it is, is their last stronghold. 41 00:05:25,540 --> 00:05:28,920 There's no other desert quite like the Gobi, 42 00:05:29,000 --> 00:05:32,170 but why is this place a desert? 43 00:05:33,420 --> 00:05:36,720 There is one simple and massive cause - 44 00:05:36,800 --> 00:05:38,350 the Himalayas. 45 00:05:42,890 --> 00:05:47,060 Clouds blowing from the south hit this gigantic barrier. 46 00:05:47,150 --> 00:05:48,610 As they're forced upwards 47 00:05:48,690 --> 00:05:52,150 so they empty their moisture on the mountain slopes, 48 00:05:52,190 --> 00:05:56,070 leaving little for the land on the other side. 49 00:06:00,580 --> 00:06:04,960 From the space deserts are very conspicuous. 50 00:06:07,290 --> 00:06:12,300 Dunes of sand hundreds of miles long streak their surface. 51 00:06:17,050 --> 00:06:20,260 With no cloak of vegetation to conceal them 52 00:06:20,350 --> 00:06:25,060 strange formations are exposed in the naked rock. 53 00:06:30,690 --> 00:06:34,650 Africa's Sahara is the largest desert of all. 54 00:06:34,740 --> 00:06:37,110 It's the size of the United States 55 00:06:37,150 --> 00:06:42,330 and the biggest source of sand and dust in the entire world. 56 00:07:22,240 --> 00:07:25,660 Sandstorms like these appear without warning 57 00:07:25,700 --> 00:07:30,790 and reduce visibility for days over areas the size of Britain. 58 00:07:39,720 --> 00:07:45,510 Dromedaries, single-humped camels, take these storms in their stride. 59 00:07:48,560 --> 00:07:53,190 The heaviest sand rises only a few metres above the ground, 60 00:07:53,270 --> 00:07:58,740 but the dust can be blown 5,000 metres up into the sky. 61 00:08:03,740 --> 00:08:07,700 The ferocious wind, armed with grains of sand, 62 00:08:07,790 --> 00:08:11,670 is the agent that shapes all deserts. 63 00:08:20,670 --> 00:08:27,770 Reptiles have armoured scaly skins that protect them from the stinging grains. 64 00:08:29,810 --> 00:08:34,980 For insects the bombardment can be very severe indeed. 65 00:08:36,770 --> 00:08:40,030 The only escape is below the surface. 66 00:08:57,000 --> 00:09:01,260 As the winds rise and fall, swallow and eddy 67 00:09:01,340 --> 00:09:04,930 so they pile the sand into dunes. 68 00:09:08,560 --> 00:09:12,770 These sand scenes can be hundreds of miles across. 69 00:09:17,020 --> 00:09:21,940 In Namibia the winds have built some of the biggest dunes in the world. 70 00:09:29,620 --> 00:09:33,910 Star dunes like these can be 300 metres high. 71 00:09:33,960 --> 00:09:38,840 Grains, swept up the flanks, are blown off the crests of the ridges 72 00:09:38,880 --> 00:09:41,670 so it's only the tops that are moving. 73 00:09:48,510 --> 00:09:54,890 The main body of these dunes may not have shifted for 5,000 years. 74 00:10:06,160 --> 00:10:12,700 Few rocks can resist the continuous blast of the sand carrying wind. 75 00:10:12,830 --> 00:10:17,830 These outcrops are standing in Egypt's White Desert. 76 00:10:18,170 --> 00:10:21,170 But they will not do so for much longer. 77 00:10:22,630 --> 00:10:25,170 They're being inexorably chiseled away 78 00:10:25,220 --> 00:10:28,340 and turned into more sand. 79 00:11:07,550 --> 00:11:14,970 Now lumps of heavily eroded rocks have been marooned in a sea of sand. 80 00:11:31,910 --> 00:11:35,620 These jagged pyramids a hundred metres tall 81 00:11:35,700 --> 00:11:39,370 were once part of a continuous rocky plateau. 82 00:11:39,460 --> 00:11:44,130 The blasting sand will eventually eliminate them altogether. 83 00:11:52,390 --> 00:11:58,930 The relentless power of the wind ensures that the face of a desert is continually changing. 84 00:11:58,980 --> 00:12:02,440 But there is one constant presence - 85 00:12:10,200 --> 00:12:12,160 the desert sun. 86 00:12:26,750 --> 00:12:30,380 The sun's heat and power to evaporate water 87 00:12:30,470 --> 00:12:36,680 has had a profound effect on the bodies and habits of everything that lives here. 88 00:12:40,390 --> 00:12:43,980 This sun potentially is a killer. 89 00:12:45,270 --> 00:12:49,400 And the red kangaroos must acknowledge that. 90 00:12:50,490 --> 00:12:52,780 Right now, while the sun is low, 91 00:12:52,860 --> 00:12:56,160 there's no immediate cause for concern. 92 00:12:56,700 --> 00:12:59,950 But this situation won't last long. 93 00:13:00,700 --> 00:13:07,250 Australia is the world's most arid continent with blistering daytime temperatures. 94 00:13:14,180 --> 00:13:20,310 Every hour the temperature rises by five degrees centigrade. 95 00:13:26,860 --> 00:13:31,320 Soon the heat will reach a critical point. 96 00:13:40,740 --> 00:13:47,000 Any kangaroo out in the open is in serious danger of overheating. 97 00:13:52,420 --> 00:13:58,890 In the full sun the temperature on the ground soars to 70 degrees. 98 00:14:03,100 --> 00:14:08,900 By midday the radiation is so intense they must take shelter. 99 00:14:29,210 --> 00:14:32,880 In the shade they're shielded from much of the sun's energy 100 00:14:32,960 --> 00:14:35,970 but their body temperature can still rise. 101 00:14:38,640 --> 00:14:42,350 So they lick saliva on to their forearms 102 00:14:42,390 --> 00:14:46,520 where there is a network of blood vessels close to the surface of the skin 103 00:14:46,560 --> 00:14:51,320 and, as the saliva evaporates, their blood is cooled. 104 00:14:53,900 --> 00:14:58,740 This thermal image shows just how effective the process is. 105 00:14:58,820 --> 00:15:02,950 The blue areas on the body are the cooler parts. 106 00:15:11,710 --> 00:15:15,550 As the saliva dries it has to be replaced 107 00:15:15,630 --> 00:15:19,970 and this is a real drain on the kangaroo's body fluids. 108 00:15:30,270 --> 00:15:34,270 Even in the shade the earth is baking hot 109 00:15:34,860 --> 00:15:38,400 so the kangaroos dig away the warmed topsoil 110 00:15:38,450 --> 00:15:41,740 to get at the cooler ground beneath. 111 00:16:04,260 --> 00:16:08,980 By staying in the shade and licking to control their body temperature 112 00:16:09,060 --> 00:16:12,310 kangaroos manage to get through the hottest part of the day 113 00:16:12,400 --> 00:16:14,060 without heat stroke. 114 00:16:14,980 --> 00:16:17,570 But for the majority of desert animals 115 00:16:17,610 --> 00:16:21,160 this strategy would not be enough for survival. 116 00:16:44,260 --> 00:16:49,310 The extraordinary ears of the fennec foxes of Africa radiate heat 117 00:16:49,390 --> 00:16:52,900 but the animals have another way of keeping cool. 118 00:17:02,490 --> 00:17:04,910 They spend their days underground 119 00:17:04,990 --> 00:17:08,080 and only emerge at sunset. 120 00:17:20,090 --> 00:17:23,510 Darkness brings huge changes. 121 00:17:23,590 --> 00:17:28,560 In the Sahara the temperature can drop as much as 30 degrees during the night, 122 00:17:28,640 --> 00:17:33,440 so it's cool enough to allow these desert fox cubs to play. 123 00:17:41,030 --> 00:17:43,700 All sorts of creatures now appear 124 00:17:43,780 --> 00:17:47,070 including some really unexpected ones. 125 00:17:49,990 --> 00:17:52,330 Toads have permeable skins 126 00:17:52,370 --> 00:17:56,420 and would quickly die from desiccation out in the daytime heat. 127 00:17:56,460 --> 00:17:59,130 It's only now that they can leave shelter. 128 00:18:02,090 --> 00:18:04,090 The same is true for scorpions, 129 00:18:04,170 --> 00:18:07,850 even though their shells are actually watertight. 130 00:18:19,940 --> 00:18:23,900 In fact, most small desert creatures are nocturnal. 131 00:18:23,990 --> 00:18:26,240 so it's only now that you can judge 132 00:18:26,320 --> 00:18:29,620 just how much life there can be in the desert. 133 00:18:30,490 --> 00:18:36,330 But moisture, lost even at night, has to be replaced sometime somehow 134 00:18:36,420 --> 00:18:41,130 and that problem dominates the lives of all desert dwellers. 135 00:18:49,300 --> 00:18:51,680 The Atacama in Chile. 136 00:18:51,720 --> 00:18:55,310 This is the driest desert in the world. 137 00:18:56,890 --> 00:18:59,980 Some parts may not see rain for fifty years 138 00:19:00,020 --> 00:19:01,440 and with such a record 139 00:19:01,480 --> 00:19:05,360 you'd expect the place to be completely barren. 140 00:19:10,280 --> 00:19:14,700 These are South America's camels, guanacos. 141 00:19:16,120 --> 00:19:18,500 They're very good at conserving moisture 142 00:19:18,580 --> 00:19:22,000 but they nonetheless need a regular supply of water. 143 00:19:34,970 --> 00:19:38,310 They get it partly from cactus flowers 144 00:19:38,350 --> 00:19:42,060 but that explanation raises another question. 145 00:19:44,270 --> 00:19:47,900 How do the cacti survive without rain? 146 00:19:54,660 --> 00:20:00,040 Hot winds suck all the moisture from the surface of the land. 147 00:20:01,380 --> 00:20:06,550 Clearly there must be something else that takes the place of rain. 148 00:20:07,800 --> 00:20:13,890 The secret is a cold sea current that runs parallel to the land. 149 00:20:30,820 --> 00:20:34,280 The cold water cools the moist warm air above it 150 00:20:34,370 --> 00:20:37,450 and that produces banks of fog. 151 00:21:00,640 --> 00:21:07,860 At the same time wind blowing on to the shore sweeps the fog inland. 152 00:21:22,620 --> 00:21:27,500 Before long the cacti are dripping with dew. 153 00:21:35,970 --> 00:21:38,010 The fog is so regular 154 00:21:38,100 --> 00:21:41,730 that moisture loving lichens are able to grow on the cacti 155 00:21:41,810 --> 00:21:45,190 and they absorb liquid like a sponge. 156 00:21:47,610 --> 00:21:50,400 In the land of almost no rain 157 00:21:50,480 --> 00:21:56,320 these precious drops are life-savers for many different creatures. 158 00:22:04,870 --> 00:22:10,880 Further inland the air remains so warm that its moisture does not condense 159 00:22:10,920 --> 00:22:15,630 so this slender strip of desert is virtually the only part of the Atacama 160 00:22:15,720 --> 00:22:17,800 where life can exist. 161 00:22:22,390 --> 00:22:23,890 Without the fog, 162 00:22:24,100 --> 00:22:26,850 this land, too, would be empty. 163 00:22:40,530 --> 00:22:43,790 The guanacos make the most of the dew 164 00:22:43,870 --> 00:22:46,750 but it will not remain for long. 165 00:22:47,420 --> 00:22:50,380 In an hour or two the sun will have burnt it off 166 00:22:50,460 --> 00:22:53,090 and dry the surface of the cacti. 167 00:23:01,930 --> 00:23:07,480 The Sonoran desert in Arizona is not quite so dry as the Atacama - 168 00:23:07,560 --> 00:23:09,810 some rain does fall. 169 00:23:10,610 --> 00:23:12,360 But it is infrequent 170 00:23:12,400 --> 00:23:13,940 and when it does arrive 171 00:23:13,980 --> 00:23:17,910 animals and plants have to be ready to make the most of it. 172 00:23:19,320 --> 00:23:21,120 And it's coming. 173 00:23:29,750 --> 00:23:31,960 When the summer monsoon blows in 174 00:23:32,040 --> 00:23:35,630 the giant saguaros, one of the biggest of all cacti, 175 00:23:35,670 --> 00:23:38,470 are ready to take full advantage of it. 176 00:24:12,670 --> 00:24:19,380 After a rainstorm the saguaro's long shallow root system sucks up the water 177 00:24:19,430 --> 00:24:24,560 and the pleats on its trunk enable it to expand rapidly. 178 00:24:32,440 --> 00:24:37,900 When full, a saguaro stem can store up to five tonnes of water 179 00:24:37,990 --> 00:24:42,530 and that's enough to see it through many months of drought. 180 00:24:46,700 --> 00:24:52,460 The trunks of these huge plants provide homes for the gila woodpecker. 181 00:24:54,460 --> 00:25:01,180 But birds are not the only animals to benefit from the presence of the cacti. 182 00:25:17,480 --> 00:25:19,490 During four weeks of the summer 183 00:25:19,570 --> 00:25:25,280 the saguaros bloom at night to attract visitors. 184 00:25:28,240 --> 00:25:31,580 The pollen and nectar with which these flowers are loaded 185 00:25:31,660 --> 00:25:36,000 attract long-nosed and long-tongued bats. 186 00:25:51,180 --> 00:25:56,400 The bats left Mexico a few days earlier to escape the heat of summer 187 00:25:56,480 --> 00:26:00,780 and are on their way north to the southern United States. 188 00:26:02,570 --> 00:26:06,740 To get there, they have to cross the Sonoran desert. 189 00:26:12,500 --> 00:26:14,670 But the desert is so big 190 00:26:14,750 --> 00:26:18,420 that for most of the year they would be unable to cross it. 191 00:26:18,500 --> 00:26:20,920 Now, with the saguaro in bloom, 192 00:26:21,010 --> 00:26:23,840 they can refuel on the way. 193 00:26:33,640 --> 00:26:37,690 So the saguaro's success in developing a way to store water 194 00:26:37,770 --> 00:26:45,610 is now crucial to most of the animals that live or even travel through this land. 195 00:27:24,360 --> 00:27:29,110 The scarcity of rain determined the shape of this icon of the desert 196 00:27:29,200 --> 00:27:31,280 but water, scarce thought it is, 197 00:27:31,370 --> 00:27:35,580 has also, like the wind, shaped the land itself. 198 00:27:52,720 --> 00:27:54,640 In the deserts of Utah 199 00:27:54,720 --> 00:28:00,480 ancient rivers flowing across sandstone country steadily widen their canyons 200 00:28:00,560 --> 00:28:07,030 until now the land between them has been reduced to spires and pinnacles. 201 00:28:36,600 --> 00:28:41,900 With little or no soil to retain the water on the surface of the land 202 00:28:41,980 --> 00:28:45,150 life here is scarce indeed. 203 00:28:46,730 --> 00:28:48,820 And when resources are limited, 204 00:28:48,900 --> 00:28:51,530 conflict is never far away. 205 00:29:02,120 --> 00:29:04,880 These are Nubian ibex 206 00:29:04,960 --> 00:29:07,800 and they are squaring up for a duel. 207 00:29:14,010 --> 00:29:15,510 And when trouble starts, 208 00:29:15,600 --> 00:29:21,140 a smart ibex knows that the best thing to do is to gain higher ground. 209 00:29:38,450 --> 00:29:41,790 These are actually subordinate male ibex, 210 00:29:41,870 --> 00:29:44,420 but their fights are nonetheless serious. 211 00:29:44,460 --> 00:29:49,760 Losing one might mean never getting the chance to breed ever. 212 00:30:12,070 --> 00:30:15,660 When competitors are evenly matched as they are here, 213 00:30:15,740 --> 00:30:18,780 duels can last for an hour. 214 00:30:38,550 --> 00:30:42,930 In this heat the effort is trully exhausting. 215 00:30:44,730 --> 00:30:51,280 But victory here will gain important ranking points on a male's way to the top. 216 00:31:22,510 --> 00:31:24,220 There's so much at stake 217 00:31:24,310 --> 00:31:26,640 that not all play fair. 218 00:31:41,870 --> 00:31:44,330 The battle has produced the winner, 219 00:31:44,410 --> 00:31:48,500 but the ultimate prize is not his yet. 220 00:31:51,920 --> 00:31:56,260 That currently belongs to the dominant male ibex. 221 00:31:58,380 --> 00:32:02,510 His rank earns him the loyalty of a harem of females 222 00:32:02,600 --> 00:32:06,270 and they follow him closely as he travels across this desert 223 00:32:06,350 --> 00:32:08,560 searching for foof and water. 224 00:32:10,690 --> 00:32:13,820 He doesn't have to waste time looking for mates - 225 00:32:13,900 --> 00:32:15,530 they're his for the taking, 226 00:32:15,610 --> 00:32:20,530 so he can concentrate with them on keeping fit and healthy. 227 00:32:35,840 --> 00:32:38,970 Lizards are desert specialists. 228 00:32:42,010 --> 00:32:45,890 But here, their numbers are extraordinary. 229 00:32:51,270 --> 00:32:57,570 These crevices in South Africa contain the highest density of lizards in the world. 230 00:33:07,370 --> 00:33:11,080 They're called flat lizards for obvious reasons, 231 00:33:11,170 --> 00:33:16,210 and they flaunt their multi-coloured bellies in territorial disputes. 232 00:33:18,630 --> 00:33:20,170 He's made his point, 233 00:33:20,260 --> 00:33:23,220 and now it's time to find some food. 234 00:33:25,010 --> 00:33:26,600 As the day warms up, 235 00:33:26,680 --> 00:33:28,970 the lizards move away from their cracks 236 00:33:29,060 --> 00:33:31,770 and head down to the bottom of the gorge. 237 00:33:32,980 --> 00:33:35,230 Their goal is the river. 238 00:33:37,610 --> 00:33:40,070 There is no food at the edge, 239 00:33:40,150 --> 00:33:43,910 but this desert river holds a secret. 240 00:33:50,370 --> 00:33:55,960 Each day blackfly rise from turbulent stretches of the river. 241 00:33:56,000 --> 00:33:58,920 This is what the lizards have come for. 242 00:34:14,020 --> 00:34:16,190 The black fly never land, 243 00:34:16,270 --> 00:34:19,980 so the lizards have to leap for their food. 244 00:34:32,200 --> 00:34:38,670 In one day each of these acrobatic little lizards may catch 50 flies. 245 00:34:48,800 --> 00:34:51,180 There are plenty of flies to go round, 246 00:34:51,270 --> 00:34:54,770 even with hundreds of lizards competing for them. 247 00:35:08,620 --> 00:35:14,910 Away from these rapids flat lizard populations are found much smaller numbers. 248 00:35:15,000 --> 00:35:20,040 But here one unusual abundance has produced another. 249 00:35:31,060 --> 00:35:34,100 Deserts are created by the lack of water, 250 00:35:34,180 --> 00:35:38,520 but what actually kills animals here is not heat or thirst, 251 00:35:38,600 --> 00:35:40,610 but lack of food. 252 00:35:59,000 --> 00:36:03,170 So how on earth does a plant-eater this size 253 00:36:03,250 --> 00:36:09,090 survive in a place apparently totally devoid of vegetation? 254 00:36:15,310 --> 00:36:19,480 Elephants in Namibia are the toughest in Africa. 255 00:36:19,560 --> 00:36:21,560 And they need to be. 256 00:36:38,620 --> 00:36:41,920 What little food exists is so dispersed 257 00:36:42,000 --> 00:36:45,090 that these elephants walk up to 50 miles a day 258 00:36:45,170 --> 00:36:50,970 as they travel up the dry river channels searching for something to eat. 259 00:37:05,610 --> 00:37:09,900 At times the task looks truly helpless. 260 00:37:44,610 --> 00:37:48,400 Elephants may seem out of place in this landscape, 261 00:37:48,480 --> 00:37:51,200 but they're not the only ones. 262 00:38:07,590 --> 00:38:11,380 Amazingly, lions live here, too. 263 00:38:15,890 --> 00:38:20,020 In savanah country huge herds of games support prides 264 00:38:20,100 --> 00:38:22,730 containing 20 lions or more. 265 00:38:22,810 --> 00:38:26,730 But to live here lions have had to change their habits - 266 00:38:26,810 --> 00:38:28,570 prides are much smaller 267 00:38:28,650 --> 00:38:31,740 and their home ranges are very much bigger. 268 00:38:32,700 --> 00:38:35,200 And there's an added problem - 269 00:38:36,490 --> 00:38:40,120 their food is always on the move. 270 00:38:48,710 --> 00:38:50,170 Like the elephants, 271 00:38:50,250 --> 00:38:55,260 the lions must travel great distances to find enough to live on. 272 00:39:10,440 --> 00:39:13,280 But lions can't go everywhere - 273 00:39:13,360 --> 00:39:17,740 they won't attempt to cross this field of sand dunes 274 00:39:17,820 --> 00:39:19,780 and the oryx know it. 275 00:40:19,680 --> 00:40:23,810 The lions must wait for the oryx to leave the safety of the dunes, 276 00:40:23,890 --> 00:40:26,890 which eventually they must to find food and water. 277 00:40:26,980 --> 00:40:29,480 And then the lions will ambush them. 278 00:41:35,210 --> 00:41:39,670 The elephants have found some of their favourite food. 279 00:41:46,220 --> 00:41:49,310 Grasses are the staple diet of all elephants, 280 00:41:49,390 --> 00:41:52,810 but this herd concentrates on digging up the roots, 281 00:41:52,900 --> 00:41:57,070 which have more nutrition and moisture than the stems. 282 00:41:57,150 --> 00:41:58,610 It's the sort of behaviour 283 00:41:58,690 --> 00:42:02,950 that can make all the difference in a place of serious shortages. 284 00:42:03,610 --> 00:42:07,450 Yet all this can change in an instant. 285 00:42:24,550 --> 00:42:29,390 The fortunes of many deserts are ruled by distant rains. 286 00:42:29,470 --> 00:42:34,900 This water fell as rain in mountains more than a hundred miles away. 287 00:42:40,360 --> 00:42:42,280 It's known as a flash flood 288 00:42:42,360 --> 00:42:46,740 and called that because the water may run for just a single day. 289 00:42:46,820 --> 00:42:51,580 It's an event that only happens once or twice a year at the most. 290 00:43:12,350 --> 00:43:16,810 The sandy riverbed acts like a giant strip of blotting paper 291 00:43:16,900 --> 00:43:20,230 sucking up the water as soon as it appears. 292 00:43:29,700 --> 00:43:33,200 But every square metre of soil moistened by this river 293 00:43:33,290 --> 00:43:37,830 will increase the chances of survival for those that live here. 294 00:43:43,420 --> 00:43:46,840 Waterholes are filled temprorarily. 295 00:43:51,470 --> 00:43:55,020 Elsewhere in Africa elephants drink every day, 296 00:43:55,100 --> 00:43:56,690 but the lack of water here 297 00:43:56,770 --> 00:44:03,530 means that desert elephants can only refill their tanks once every four or five days. 298 00:44:04,610 --> 00:44:08,950 Within a week the flash flood has produced a flush of green, 299 00:44:09,030 --> 00:44:13,370 more than enough to draw the oryx out of the dunes. 300 00:44:15,200 --> 00:44:19,330 It's a rare chance for them to build up their food reserves. 301 00:44:27,930 --> 00:44:32,510 The flood has made life easier for the lions, too. 302 00:44:34,850 --> 00:44:39,980 The flesh of this oryx will keep the family going for a week at the most. 303 00:44:40,060 --> 00:44:42,560 But for a while the hunting will be easier, 304 00:44:42,650 --> 00:44:45,820 now that river channel has turned green. 305 00:44:49,740 --> 00:44:52,620 The good times for lions and oryx are brief, 306 00:44:52,740 --> 00:44:54,790 but these are the short moments 307 00:44:54,870 --> 00:44:59,040 that make it possible to live in deserts the year round. 308 00:45:04,750 --> 00:45:07,880 Death Valley is the hottest place on Earth. 309 00:45:07,970 --> 00:45:12,260 Yet even this furnace can be transformed by water. 310 00:45:22,810 --> 00:45:27,900 A single shower can enable seeds that have lain dormant for 30 years or more 311 00:45:27,990 --> 00:45:30,150 to burst into life. 312 00:45:38,500 --> 00:45:42,960 And there hasn't been a bloom like this one for a century. 313 00:45:55,140 --> 00:45:58,850 The periods of boom in Death Valley are short. 314 00:45:58,930 --> 00:46:03,230 but they're just frequent enough to keep life ticking over. 315 00:46:11,740 --> 00:46:16,410 A sudden flush of vegetation is what every desert dweller waits for, 316 00:46:16,490 --> 00:46:19,830 and when it happens they must make the most of it. 317 00:46:40,270 --> 00:46:42,640 There is no other species on the planet 318 00:46:42,730 --> 00:46:49,730 that responds as quickly and as dramatically to the good times as the desert locust. 319 00:46:50,030 --> 00:46:55,200 Eggs that have remained in the ground for 20 years begin to hatch. 320 00:47:07,790 --> 00:47:09,960 The young locusts are known as hoppers, 321 00:47:10,050 --> 00:47:12,420 for at this stage they're flightless. 322 00:47:12,630 --> 00:47:19,260 They find new feeding grounds by following the smell of sprouting grass. 323 00:47:25,060 --> 00:47:29,060 Normally it takes four weeks for hoppers to become adults, 324 00:47:29,150 --> 00:47:31,690 but when the conditions are right as now 325 00:47:31,780 --> 00:47:35,570 their development switches to the fast track. 326 00:47:40,530 --> 00:47:43,790 As the vegetation in one place begins to run out 327 00:47:43,870 --> 00:47:47,460 the winged adults release pheromones - scent messages, 328 00:47:47,540 --> 00:47:51,130 which tell others in the group that they must move on. 329 00:48:03,060 --> 00:48:04,680 And when groups merge, 330 00:48:04,770 --> 00:48:07,060 they form a swarm. 331 00:48:29,630 --> 00:48:33,800 An adult locust eats its entire body weight every day, 332 00:48:33,880 --> 00:48:39,470 and a whole swarm can consume literally hundreds of tonnes of vegetation. 333 00:48:40,970 --> 00:48:43,310 They have to keep on moving. 334 00:48:44,720 --> 00:48:46,980 The swarm travels with the wind - 335 00:48:47,020 --> 00:48:50,480 it's the most energy-saving way of flying. 336 00:48:54,020 --> 00:48:59,610 Following the flow of wind means that they're always heading toward areas of low pressure, 337 00:48:59,700 --> 00:49:05,120 places where wind meets rain and vegetation starts to grow. 338 00:49:07,000 --> 00:49:08,040 As they fly, 339 00:49:08,120 --> 00:49:10,830 swarms join up with other swarms 340 00:49:10,920 --> 00:49:14,920 to form gigant­­­ic plagues several billions strong 341 00:49:15,000 --> 00:49:17,590 and as much as 40 miles wide. 342 00:49:19,590 --> 00:49:24,220 They will consume every edible thing that lies in their path. 343 00:49:37,530 --> 00:49:41,740 This is one of planet Earth's greatest spectacles. 344 00:49:41,820 --> 00:49:43,820 It's rarely seen on this scale 345 00:49:43,910 --> 00:49:45,990 and it won't last long. 346 00:49:46,080 --> 00:49:47,790 Once the food is gone, 347 00:49:47,870 --> 00:49:53,830 the steady roar of a billion beating locust wings will once again be replaced 348 00:49:53,920 --> 00:49:58,630 by nothing more than the sound of the desert wind. 282 00:50:00,136 --> 00:50:25,136 © anoXmous @ http://thepiratebay.sx/user/Zen_Bud