1 00:00:38,620 --> 00:00:40,952 Africa is a parched continent... 2 00:00:42,324 --> 00:00:45,691 ...where the driving force of life is fresh water. 3 00:00:55,737 --> 00:00:58,297 Often sparse - but sometimes torrential 4 00:00:58,440 --> 00:01:00,931 water is an architect of landscapes... 5 00:01:01,777 --> 00:01:06,111 and a catalyst for some of the most dazzling wildlife spectacles. 6 00:01:11,587 --> 00:01:14,750 This is the story of Africa's most precious commodity... 7 00:01:14,890 --> 00:01:18,223 and of the many enchanting worlds it has created. 8 00:01:37,045 --> 00:01:41,505 The source of all of Africa's fresh water are rain-bearing clouds, 9 00:01:41,650 --> 00:01:45,142 rising off the warm oceans which surround the continent. 10 00:01:48,190 --> 00:01:51,523 Washing over the land, their destination is uncertain... 11 00:01:51,660 --> 00:01:53,787 and ruled by fickle winds. 12 00:01:57,966 --> 00:02:01,060 But it's Africa's high ground the hills and mountains 13 00:02:01,136 --> 00:02:03,764 which catch most of their precious cargo. 14 00:02:07,909 --> 00:02:09,240 The contours of the land... 15 00:02:09,378 --> 00:02:13,109 the troughs and valleys first channel the flow of water... 16 00:02:21,556 --> 00:02:23,490 Gathering in volume and strength, 17 00:02:23,625 --> 00:02:28,460 water increasingly takes control... carving its own path. 18 00:02:52,587 --> 00:02:55,147 Victoria Falls in Zimbabwe... 19 00:02:55,290 --> 00:02:58,225 the greatest single curtain of water in the world... 20 00:02:58,694 --> 00:03:03,256 little wonder, the local tribes call it 'the smoke that thunders.' 21 00:03:32,861 --> 00:03:37,025 With thousands of streams now channelled into one powerful river... 22 00:03:37,165 --> 00:03:40,566 the waters become their own natural architect. 23 00:03:57,185 --> 00:03:59,210 Boulders hammer at the river bed... 24 00:03:59,554 --> 00:04:03,251 making the Falls ever higher, the gorges deeper. 25 00:04:09,131 --> 00:04:14,899 This body of water has a name... the Zambezi River. 26 00:04:25,914 --> 00:04:27,279 As the land levels out, 27 00:04:27,416 --> 00:04:30,783 the river becomes a frontier of opportunity... 28 00:04:44,766 --> 00:04:46,996 The waters are calmer... warmer... 29 00:04:47,169 --> 00:04:51,333 rich with oxygen and dissolved minerals... crucial ingredients for life. 30 00:04:56,445 --> 00:04:57,707 And the fishing's good! 31 00:05:00,415 --> 00:05:04,215 The reed cormorant is beautifully streamlined to pursue catfish... 32 00:05:07,389 --> 00:05:10,654 Fish is also the staple of the local Tokaleya people. 33 00:05:19,668 --> 00:05:22,569 From its source over a thousand kilometres away, 34 00:05:22,704 --> 00:05:24,729 the Zambezi waters are now tamed... 35 00:05:25,207 --> 00:05:27,641 gentle and rich enough to support life. 36 00:05:37,152 --> 00:05:39,643 The Zambezi is one of four major rivers 37 00:05:39,788 --> 00:05:42,985 which originate in equatorial Africa and branch out 38 00:05:43,158 --> 00:05:46,594 like giant arteries across the continent. 39 00:05:52,000 --> 00:05:53,558 Clearly visible from space, 40 00:05:53,702 --> 00:05:59,663 the Congo drains over 3 million square kilometres of tropical rainforest. 41 00:06:02,744 --> 00:06:04,769 The Nile is the world's longest river... 42 00:06:04,913 --> 00:06:08,610 flowing almost 7000 kilometres to the Mediterranean. 43 00:06:08,884 --> 00:06:10,078 And the mighty Niger... 44 00:06:10,185 --> 00:06:13,177 bringing life to West Africa's Sahel desert. 45 00:06:16,858 --> 00:06:20,521 Feeding these great rivers are a myriad of tributaries... 46 00:06:21,196 --> 00:06:24,563 branching like capillaries across the face of Africa. 47 00:06:27,269 --> 00:06:31,603 Tributaries yes - but by any standards still great rivers. 48 00:06:32,007 --> 00:06:34,942 Like the Luangwa, which feeds the Zambezi. 49 00:06:40,549 --> 00:06:42,540 Winding its way from the high ground, 50 00:06:42,684 --> 00:06:45,414 the Luangwa has slowed and collected silt... 51 00:06:45,620 --> 00:06:48,987 which it now sheds... to form a near-desert landscape. 52 00:07:05,807 --> 00:07:06,535 For land animals, 53 00:07:06,675 --> 00:07:09,974 the river is one of the few places to get a much-needed drink. 54 00:07:12,714 --> 00:07:17,083 Here - as in most of Africa the rains are sparse and unpredictable. 55 00:07:17,619 --> 00:07:19,780 The drought can last 8 months or more... 56 00:07:20,455 --> 00:07:22,923 the Luangwa a dwindling resource. 57 00:07:28,630 --> 00:07:33,693 Though 57 million tonnes of rain falls on the African continent every day, 58 00:07:33,835 --> 00:07:39,000 as much as 80o/o of it is lost by evaporation or absorbed by the ground... 59 00:07:39,808 --> 00:07:41,867 so the rest is precious... 60 00:07:50,719 --> 00:07:52,346 Such is the demand for water, 61 00:07:52,487 --> 00:07:55,217 that all sorts of takers crowd the riverbank... 62 00:07:55,490 --> 00:07:57,754 assuming a temporary truce. 63 00:08:12,107 --> 00:08:15,304 But quenching a thirst is not without risk. 64 00:08:19,114 --> 00:08:23,073 The Nile crocodile... a creature older than Africa itself... 65 00:08:23,785 --> 00:08:27,346 its hunting skills honed over 200 million years. 66 00:08:39,200 --> 00:08:41,100 Using extreme stealth, 67 00:08:41,202 --> 00:08:44,194 the crocodile needs to get within a metre of its prey. 68 00:08:50,712 --> 00:08:53,875 Desperate to drink, the buffalo seem blind to the danger. 69 00:09:46,634 --> 00:09:48,864 ...just too much for a croc out of water... 70 00:09:53,608 --> 00:09:54,939 ...but they'll be another chance. 71 00:09:58,747 --> 00:10:02,274 The dry season brings plenty of opportunity for crocodiles, 72 00:10:02,417 --> 00:10:03,384 but it's a real problem 73 00:10:03,518 --> 00:10:07,682 for Africa's other large freshwater animal the hippopotamus. 74 00:10:17,599 --> 00:10:21,262 Hippos need deep water to protect their skin from the harsh sun. 75 00:10:21,870 --> 00:10:24,395 And when the river falls to a critically low level, 76 00:10:24,539 --> 00:10:27,133 the males become fired with aggression... 77 00:10:42,323 --> 00:10:45,884 These brutal battles are all about winning deep-water territory, 78 00:10:46,027 --> 00:10:47,790 which the females prefer. 79 00:11:02,844 --> 00:11:04,971 For the victors the rewards of deep water 80 00:11:05,146 --> 00:11:07,512 and numerous females will be enormous... 81 00:11:39,881 --> 00:11:43,510 The lives of hippos are ruled by the ebb and flow of the seasons, 82 00:11:43,985 --> 00:11:47,580 but these small savannah finches known as "quelea" 83 00:11:47,722 --> 00:11:49,155 are totally nomadic, 84 00:11:49,324 --> 00:11:52,919 instinctively finding water from hundreds of kilometres away. 85 00:11:53,628 --> 00:11:56,426 Like locusts, they swarm in their millions, 86 00:11:56,564 --> 00:11:59,692 forming flocks up to 4kms wide. 87 00:12:10,578 --> 00:12:13,411 Quelea - like many birds in subtropical Africa 88 00:12:13,548 --> 00:12:16,415 breed when food and rainfall are plentiful. 89 00:12:17,619 --> 00:12:21,783 But here in Luangwa, one spectacular bird does the opposite. 90 00:12:26,828 --> 00:12:30,127 Carmine bee-eaters breed at the hottest time of the year, 91 00:12:30,465 --> 00:12:34,128 when the sandy banks of the river are exposed by the low water. 92 00:12:39,874 --> 00:12:42,138 He's not banging his head against a brick wall 93 00:12:42,210 --> 00:12:44,610 but excavating a nest chamber. 94 00:12:45,046 --> 00:12:46,138 It's a yearly chore, 95 00:12:46,247 --> 00:12:48,807 as the river is always reshaping the banks. 96 00:12:55,657 --> 00:12:59,991 The steepest cliffs are most in demand because they're safest from predators. 97 00:13:01,663 --> 00:13:04,598 Some bee-eaters will try anything to get what they want... 98 00:13:15,944 --> 00:13:18,742 But owning a nest doesn't guarantee a mate... 99 00:13:19,747 --> 00:13:22,648 she must also be seduced with a gift. 100 00:13:26,187 --> 00:13:28,985 He offers her a bee to seal the bond. 101 00:13:33,761 --> 00:13:37,561 In a crowded colony like this, parasites and ticks are rife, 102 00:13:37,832 --> 00:13:41,928 so carmine bee-eaters take time out to burn them off in the sun. 103 00:13:48,776 --> 00:13:50,368 But they can't afford to relax... 104 00:13:50,578 --> 00:13:54,173 the racket of breeding birds always attracts trouble. 105 00:14:01,723 --> 00:14:03,418 Enter the dragon. 106 00:14:06,928 --> 00:14:11,194 Monitor lizards are formidable scavengers and competent swimmers 107 00:14:11,332 --> 00:14:13,892 quite at ease along Africa's rivers. 108 00:14:17,305 --> 00:14:20,832 The bee-eaters are powerless to stop this determined egg thief. 109 00:14:29,717 --> 00:14:31,776 But by breeding in huge numbers 110 00:14:31,919 --> 00:14:34,911 only a small proportion of the nests are raided. 111 00:14:35,690 --> 00:14:38,124 And many of the eggs are out of reach. 112 00:14:44,832 --> 00:14:48,131 It's not just monitor lizards that the bee-eaters need to fear. 113 00:14:49,170 --> 00:14:52,936 Along the banks of the Luangwa is a far greater threat. 114 00:14:56,878 --> 00:14:58,812 ...the African fish eagle... 115 00:15:00,615 --> 00:15:02,606 ...also partial to birds. 116 00:15:51,933 --> 00:15:55,164 For male hippos it's the drought that can be a killer. 117 00:15:56,671 --> 00:16:02,303 Under baking skies, those wounded and exhausted from battle can easily succumb. 118 00:16:03,111 --> 00:16:07,070 And waiting in the wings... the patient undertaker. 119 00:16:10,918 --> 00:16:13,352 Though their diet is usually small fish, 120 00:16:13,488 --> 00:16:16,787 crocodiles can get by on just one big meal a year... 121 00:16:19,427 --> 00:16:23,090 ...and a large male hippo carries more than two tonnes of flesh. 122 00:16:30,938 --> 00:16:34,738 A crocodile's stomach juices are more acidic than any other animal 123 00:16:34,876 --> 00:16:40,439 strong enough to digest every part of the carcass - even hooves, bones and skin. 124 00:16:58,166 --> 00:17:01,624 Despite their massive jaws, crocodiles can't chew, 125 00:17:01,769 --> 00:17:07,332 but they can tear off large chunks of meat by gripping the carcass and spinning. 126 00:17:45,379 --> 00:17:49,179 The largest crocs can gorge nearly half a tonne of flesh. 127 00:17:50,251 --> 00:17:54,915 Under such an assault the carcass can vanish in a matter of hours. 128 00:18:14,141 --> 00:18:16,632 Africa's rivers are vital lifelines, 129 00:18:16,777 --> 00:18:19,177 bringing relief to the harshest of places, 130 00:18:19,313 --> 00:18:23,249 yet they hold only a fraction of the continent's fresh water. 131 00:18:24,719 --> 00:18:26,380 Over the last 20 million years 132 00:18:26,520 --> 00:18:30,513 Africa has been tearing apart along the Great Rift Valley, 133 00:18:30,658 --> 00:18:34,185 creating new basins which have since filled with water. 134 00:18:35,663 --> 00:18:38,461 The result is a string of giant lakes... 135 00:18:39,233 --> 00:18:43,499 such as Tanganyika, Kivu... and Malawi. 136 00:18:54,448 --> 00:18:58,214 Lake Malawi is an ocean of permanent fresh water... 137 00:18:58,519 --> 00:19:02,387 nearly a kilometre deep and 600 kms long. 138 00:19:12,433 --> 00:19:16,164 The birth of this great lake brought with it a rapid explosion of life. 139 00:19:16,570 --> 00:19:21,337 More than 700 types of cichlid fish have evolved from a single species 140 00:19:21,475 --> 00:19:23,966 which first entered the lake from nearby rivers. 141 00:19:27,915 --> 00:19:30,213 Through competition for food and space, 142 00:19:30,351 --> 00:19:34,117 each type of cichlid has developed its own special habits. 143 00:19:37,792 --> 00:19:39,191 Many feed on algae 144 00:19:39,327 --> 00:19:42,854 each evolved to harvest different types of rock face. 145 00:19:55,776 --> 00:19:58,370 But not all cichlids are vegetarians. 146 00:20:00,915 --> 00:20:05,579 Stalking the mid-water shoals is a fish which is fast as lightning... 147 00:20:08,989 --> 00:20:10,957 ...the barracuda of Lake Malawi. 148 00:20:22,937 --> 00:20:26,998 And lurking beneath, the only fish in the world who plays dead. 149 00:20:36,083 --> 00:20:39,780 This cichlid lures prey by mimicking a rotting corpse. 150 00:20:57,605 --> 00:21:00,870 In such a dangerous world, young cichlids need cover. 151 00:21:05,913 --> 00:21:09,280 Many Malawi mothers protect their brood in their mouths. 152 00:21:22,696 --> 00:21:25,563 It works fine until the youngsters get too big... 153 00:21:29,770 --> 00:21:33,399 When that happens, these particular cichlids swim deep... 154 00:21:40,448 --> 00:21:43,940 Fifty metres down they find new child minders... 155 00:21:44,485 --> 00:21:45,850 a pair of catfish. 156 00:21:49,590 --> 00:21:52,150 The catfish already have a large brood of their own, 157 00:21:52,526 --> 00:21:55,859 yet they tolerate adopting hundreds of young cichlids. 158 00:22:07,475 --> 00:22:11,571 This remarkable behaviour is so new to science that no one yet knows how 159 00:22:11,712 --> 00:22:13,737 or why it has evolved. 160 00:22:26,994 --> 00:22:29,224 Lake Malawi is a stable body of water, 161 00:22:29,363 --> 00:22:31,991 where life is sheltered from extremes of climate... 162 00:22:33,067 --> 00:22:36,036 but the arrival of the rains has a profound influence 163 00:22:36,170 --> 00:22:38,035 on all its inhabitants. 164 00:22:47,848 --> 00:22:51,306 Erupting from the lake surface, billions of flies... 165 00:22:51,852 --> 00:22:56,152 forming clouds 2 kms high and 5 kms wide. 166 00:22:57,992 --> 00:22:59,983 No-one knows what triggers this event... 167 00:23:00,361 --> 00:23:01,555 the cycle of the moon... 168 00:23:01,695 --> 00:23:04,391 or maybe the hammering of raindrops on water. 169 00:23:09,703 --> 00:23:12,729 For the flies, the journey from the lake bed is perilous... 170 00:23:13,774 --> 00:23:16,402 Their larvae must ascend 40m... 171 00:23:16,544 --> 00:23:19,411 running the gauntlet of a thousand mouths. 172 00:23:42,903 --> 00:23:44,871 Even when they've reached the breeding swarm, 173 00:23:45,005 --> 00:23:46,666 the lake flies aren't safe... 174 00:23:47,174 --> 00:23:50,507 they're a feast for swallows, swifts and martins... 175 00:23:51,011 --> 00:23:53,980 fattening up before their long migration to Europe. 176 00:24:19,974 --> 00:24:23,842 After mating the females lay their eggs on the lake surface... 177 00:24:23,978 --> 00:24:27,243 and then they die... all within a few days. 178 00:24:31,819 --> 00:24:33,878 Another bonanza for cichlids. 179 00:24:43,697 --> 00:24:47,155 But feeding at the lake surface is dicing with death. 180 00:24:53,874 --> 00:24:57,139 The pied kingfisher... an open-water marksman... 181 00:25:05,486 --> 00:25:08,683 Pied kingfishers are the largest kingfishers in Africa, 182 00:25:08,822 --> 00:25:12,087 able to fly 20 kms offshore to hunt. 183 00:25:48,062 --> 00:25:51,998 Lake Malawi is so productive that nearly a quarter of a million people 184 00:25:52,166 --> 00:25:53,531 make their living from it. 185 00:26:00,040 --> 00:26:01,598 Seventy per cent of all the protein 186 00:26:01,742 --> 00:26:04,802 in the local diet comes directly from fish. 187 00:26:19,126 --> 00:26:21,993 With their abundant riches and endless fresh water, 188 00:26:22,129 --> 00:26:27,829 Africa's Great Lakes are like vast oases in a predominantly dry continent. 189 00:26:28,902 --> 00:26:32,167 But their influence stretches far beyond their shores. 190 00:26:45,552 --> 00:26:48,112 During the rainy season the level of the Great Lakes 191 00:26:48,188 --> 00:26:50,850 can rise by over three metres. 192 00:26:51,925 --> 00:26:54,758 Spread over an area twice the size of Ireland 193 00:26:54,895 --> 00:26:58,422 this represents trillions of tonnes of extra water. 194 00:27:13,947 --> 00:27:16,973 The swollen lakes can't hold all the surplus water. 195 00:27:18,118 --> 00:27:21,383 It floods into surrounding rivers which overspill their banks... 196 00:27:21,655 --> 00:27:27,093 priming new types of water world... Africa's wetlands. 197 00:27:31,799 --> 00:27:36,793 Each year the Chambeshi river inundates 10,000 sq kms of Zambia... 198 00:27:37,571 --> 00:27:40,233 turning it into the vast Bengweulu swamp. 199 00:27:47,247 --> 00:27:49,238 Its waters are warm and shallow... 200 00:27:49,683 --> 00:27:52,880 thick with nutrients... and bursting with life. 201 00:28:19,713 --> 00:28:22,580 Mobility is the key to survival in wetlands, 202 00:28:22,716 --> 00:28:24,741 where food is often hard to reach. 203 00:28:28,488 --> 00:28:29,284 With their long legs, 204 00:28:29,423 --> 00:28:32,654 black lechwe can wade to the richest water meadows. 205 00:28:34,728 --> 00:28:39,756 ...and by flying, herons, egrets and storks can find the best fishing grounds. 206 00:28:55,015 --> 00:28:56,744 In the furthest reaches of Bengweulu 207 00:28:56,884 --> 00:29:00,285 lives one of Africa's rarest and most secretive birds... 208 00:29:04,858 --> 00:29:06,416 ...the shoebill stork. 209 00:29:08,228 --> 00:29:10,059 It's a stealthy, sharp-eyed hunter... 210 00:29:10,297 --> 00:29:13,494 able to spot the slightest stirrings beneath the surface. 211 00:29:20,507 --> 00:29:21,565 A lungfish. 212 00:29:33,654 --> 00:29:37,681 Shoebills specialise in ambushing large fish in small territories, 213 00:29:38,358 --> 00:29:42,294 but most birds in the Benguelu swamp need to search far and wide 214 00:29:42,429 --> 00:29:46,661 to find the richest gatherings of insects, frogs and fish fry. 215 00:29:57,744 --> 00:29:59,769 By displaying and calling to one another, 216 00:29:59,913 --> 00:30:03,246 groups of wattled cranes can even communicate information 217 00:30:03,383 --> 00:30:05,214 about the best feeding grounds. 218 00:30:10,157 --> 00:30:12,819 Teamwork is also crucial for spoonbills. 219 00:30:13,193 --> 00:30:17,289 Advancing like a Roman legion, they drive small fish before them. 220 00:30:25,739 --> 00:30:27,263 Swinging from side to side, 221 00:30:27,407 --> 00:30:29,500 their bills create swirling eddies 222 00:30:29,643 --> 00:30:32,305 which help them to sense and scoop up the fish. 223 00:30:44,758 --> 00:30:48,159 Ahead of them, black egrets intercept the fleeing prey. 224 00:30:50,063 --> 00:30:51,428 They're canny hunters... 225 00:30:51,698 --> 00:30:54,428 using their wings as umbrellas to create shade... 226 00:30:54,568 --> 00:30:58,197 luring unsuspecting fish right to their feet. 227 00:31:12,152 --> 00:31:14,712 Rising and falling with the seasons, the still, 228 00:31:14,855 --> 00:31:19,918 shallow waters of Bengweulu have created a simple - but magical wetland. 229 00:31:46,219 --> 00:31:47,914 Far to the south of Bengweulu, 230 00:31:48,055 --> 00:31:52,185 there's a very different type of wetland ...much more complex. 231 00:31:56,430 --> 00:31:58,728 The Okavango in Botswana... 232 00:31:59,266 --> 00:32:03,464 a river delta fanning out across the land ...never reaching the sea... 233 00:32:06,473 --> 00:32:09,772 It's one vast tapestry of waterways. 234 00:32:22,322 --> 00:32:25,155 Okavango is shaped by the land... the water... 235 00:32:25,292 --> 00:32:27,192 and sheer brute force. 236 00:32:33,266 --> 00:32:35,757 Hippos are wetland bulldozers... 237 00:32:35,902 --> 00:32:39,133 carving out channels that direct the flow of water... 238 00:32:52,185 --> 00:32:54,380 These waterways are always changing. 239 00:32:54,988 --> 00:32:57,855 Vegetation and sediment close old routes... 240 00:32:59,559 --> 00:33:01,686 ...and flooding opens up new lakes. 241 00:33:06,133 --> 00:33:08,795 In the central swamp there is permanent water... 242 00:33:09,269 --> 00:33:10,896 it's a mecca for hippos. 243 00:33:20,046 --> 00:33:22,674 Here there's no fear of death from drought. 244 00:33:44,204 --> 00:33:48,698 Together this group represents 40 tonnes of earth-moving equipment. 245 00:34:01,721 --> 00:34:04,690 It's not just the hippo's power which shapes the delta... 246 00:34:05,125 --> 00:34:07,787 their dung also enriches the waterways... 247 00:34:07,928 --> 00:34:11,329 which flush the valuable fertiliser through the whole system. 248 00:34:16,136 --> 00:34:21,233 The land here is almost flat and the Okavango waters flow ever-so gently 249 00:34:21,908 --> 00:34:25,002 ...taking a full 6 months to cross the delta. 250 00:34:28,448 --> 00:34:31,906 Stands of fast-growing papyrus dominate the upper reaches 251 00:34:32,052 --> 00:34:34,020 where the water is a little faster... 252 00:34:43,763 --> 00:34:47,893 Moving among these lazy waters are fish like African pike... 253 00:34:48,034 --> 00:34:51,197 seeking out new frontiers to spawn and feed. 254 00:34:57,043 --> 00:34:58,840 And tracking the movements of fish... 255 00:34:58,979 --> 00:35:02,938 a range of hunters... like the Bayei of Botswana... 256 00:35:06,686 --> 00:35:10,087 ...they net off channels to intercept the migrating fish. 257 00:35:18,665 --> 00:35:23,295 The clear calm waters of Okavango make spotting prey from above easy... 258 00:35:25,138 --> 00:35:28,107 ...and African fish eagles are sharp eyed hunters... 259 00:35:36,049 --> 00:35:40,611 Eagles are spear fishermen... but others here prefer to trawl. 260 00:35:43,890 --> 00:35:46,791 Skimmers have a lower beak longer than the upper, 261 00:35:46,926 --> 00:35:49,895 allowing them to snap small fish from the surface. 262 00:36:00,206 --> 00:36:01,639 Nowhere else in Africa has such 263 00:36:01,775 --> 00:36:05,302 a variety of different types of water as Okavango... 264 00:36:05,845 --> 00:36:08,439 the greatest inland delta in the world. 265 00:36:41,014 --> 00:36:42,481 Seeing Okavango today, 266 00:36:42,615 --> 00:36:45,106 it's hard to believe that this region of Africa 267 00:36:45,185 --> 00:36:47,415 was once a sun-baked desert. 268 00:36:48,688 --> 00:36:50,849 It was only the chance movements of the earth, 269 00:36:50,990 --> 00:36:54,323 causing a river to alter its course and spill across the land, 270 00:36:54,461 --> 00:36:57,555 that created this waterlogged paradise. 271 00:36:58,765 --> 00:37:01,757 And it's is not just a place for swamp creatures... 272 00:37:06,106 --> 00:37:10,566 ...many savannah animals have also found ways to exploit Okavango. 273 00:37:12,545 --> 00:37:14,376 With their great powers of memory, 274 00:37:14,514 --> 00:37:17,381 elephants quickly learn to navigate the driest routes 275 00:37:17,517 --> 00:37:19,246 between their feeding grounds. 276 00:37:35,468 --> 00:37:39,199 It's not easy finding sure footing in this boggy terrain... 277 00:37:49,048 --> 00:37:53,314 The ever-changing flow of water is always revealing new pastures, 278 00:37:53,453 --> 00:37:55,444 so animals need to keep moving. 279 00:38:00,660 --> 00:38:03,322 For lions, this means keeping up with their prey... 280 00:38:03,463 --> 00:38:05,192 which is no easy task. 281 00:38:13,540 --> 00:38:15,940 Impala can take the water in their stride... 282 00:38:17,677 --> 00:38:21,408 ...but for lions - like most cats it's a real obstacle. 283 00:38:34,861 --> 00:38:38,126 Buffalo are a potential target for a large pride of lions. 284 00:38:39,532 --> 00:38:41,227 ...if only they could reach them... 285 00:38:53,012 --> 00:38:54,377 There's only one thing for it... 286 00:39:11,631 --> 00:39:13,496 Now the tables are turned. 287 00:39:14,167 --> 00:39:16,727 The buffalo may have reached their grassy island... 288 00:39:17,904 --> 00:39:19,872 ...but so have the hunters. 289 00:39:50,670 --> 00:39:53,161 The waters now play to the lions advantage 290 00:39:53,306 --> 00:39:55,399 ...helping them to corral the herd. 291 00:40:58,404 --> 00:41:01,567 These are crucial contests of strength and cunning... 292 00:41:03,676 --> 00:41:08,113 ...but all life in Africa is at the mercy of a far greater force... 293 00:41:10,216 --> 00:41:11,410 ...fresh water. 294 00:41:18,458 --> 00:41:21,757 The water of Okavango has no great lake to flow into, 295 00:41:21,894 --> 00:41:23,725 nor does it ever reach the sea... 296 00:41:25,164 --> 00:41:28,133 ...all that life-giving water going nowhere 297 00:41:28,201 --> 00:41:32,467 ...sucked away in the great emptiness of the Kalahari desert. 298 00:41:43,850 --> 00:41:46,318 Drought is the reality for much of Africa 299 00:41:46,452 --> 00:41:48,977 ...a continent so vast and so hot 300 00:41:49,188 --> 00:41:52,248 that clouds can rarely penetrate the interior. 301 00:41:59,098 --> 00:42:01,259 But there is one other place in Africa 302 00:42:01,401 --> 00:42:04,427 where wildlife can find water in abundance. 303 00:42:06,139 --> 00:42:09,006 In the central and northern reaches of the Great Rift Valley 304 00:42:09,142 --> 00:42:11,736 are a chain of weird and wonderful lakes 305 00:42:11,878 --> 00:42:16,474 with names like Magadi, Nakuru, Natron and Bogoria. 306 00:42:20,887 --> 00:42:24,584 Though they look enticing... these are no ordinary lakes. 307 00:42:24,724 --> 00:42:27,124 Trapped in a world of volcanic turmoil, 308 00:42:27,193 --> 00:42:33,132 their precious waters are contaminated by sodium carbonate... the soda lakes. 309 00:42:35,802 --> 00:42:37,133 Caustic and alkaline... 310 00:42:37,236 --> 00:42:39,534 they are the fiercest waters in Africa... 311 00:43:09,168 --> 00:43:11,193 More like a scene from another planet, 312 00:43:11,337 --> 00:43:14,170 these bitter cauldrons are alien worlds. 313 00:43:17,443 --> 00:43:19,502 But they are not lifeless. 314 00:43:21,814 --> 00:43:25,215 One remarkable creature has found a way to conquer them. 315 00:43:37,697 --> 00:43:42,157 Flamingos, in their countless millions, migrate up and down the Rift Valley. 316 00:43:43,970 --> 00:43:45,301 They seem to instinctively know 317 00:43:45,438 --> 00:43:49,898 when each lake has just the right balance of water and soda to support them. 318 00:43:59,852 --> 00:44:01,547 A riot of pink... 319 00:44:01,888 --> 00:44:04,755 one of Africa's most dazzling spectacles. 320 00:44:56,776 --> 00:44:58,573 With their long, thick-skinned legs, 321 00:44:58,711 --> 00:45:01,612 flamingos can tolerate water so alkaline 322 00:45:01,747 --> 00:45:04,682 it would scour the flesh off other animals. 323 00:45:07,119 --> 00:45:12,113 Though harsh, the soda-rich waters teem with a unique form of blue-green algae, 324 00:45:12,258 --> 00:45:16,558 which the flamingos siphon through fine combs in their beaks... 325 00:45:18,598 --> 00:45:20,327 By using the beak upside down, 326 00:45:20,466 --> 00:45:23,799 flamingos avoid wetting their heads in the bitter water... 327 00:45:24,737 --> 00:45:26,796 it's a miracle of evolution. 328 00:45:37,917 --> 00:45:40,886 Like all animals, flamingos still need to drink 329 00:45:41,654 --> 00:45:46,250 ...but where can they possibly find sweet fresh water in a place this? 330 00:45:52,398 --> 00:45:54,832 Luckily for them, around the margins of the lakes 331 00:45:54,967 --> 00:45:56,832 there are clear-running springs, 332 00:45:56,969 --> 00:45:59,802 bringing relief from the depths of the earth. 333 00:46:06,946 --> 00:46:10,814 It's also a chance to wash any soda off their feathers and skin. 334 00:46:17,223 --> 00:46:18,451 And every few years... 335 00:46:18,591 --> 00:46:20,718 when the feeding conditions are perfect... 336 00:46:20,860 --> 00:46:25,194 flamingos join together in a magical courtship dance... 337 00:47:25,825 --> 00:47:29,283 Africa's precious water dictates the terms of life. 338 00:47:31,731 --> 00:47:35,531 Even here in the harshest waters, life can still triumph. 339 00:47:45,144 --> 00:47:47,339 The waters of Africa's lakes and rivers 340 00:47:47,480 --> 00:47:50,972 have shaped the evolution of some remarkable animals... 341 00:47:51,317 --> 00:47:53,342 ...they unite its many worlds... 342 00:47:56,389 --> 00:47:59,825 They are the life-blood of the continent...