1 00:00:36,804 --> 00:00:39,864 The Amazon is the mightiest river on earth. 2 00:00:41,009 --> 00:00:43,034 A thousand miles before it reaches the sea 3 00:00:43,177 --> 00:00:46,510 its main channel is already ten miles wide. 4 00:00:47,916 --> 00:00:49,440 By the time it meets the ocean 5 00:00:49,584 --> 00:00:53,315 it carries a fifth of all the river water in the world 6 00:00:53,721 --> 00:00:59,216 spilling an incredible forty five million gallons a second into the Atlantic. 7 00:01:08,836 --> 00:01:11,999 Every year, without fail the Amazon bursts its banks 8 00:01:12,140 --> 00:01:15,598 and floods an area of forest the size of England. 9 00:01:30,258 --> 00:01:32,226 This huge change in water level 10 00:01:32,360 --> 00:01:34,055 over such a vast area 11 00:01:34,195 --> 00:01:37,653 affects everything that lives here in a dramatic way. 12 00:01:51,713 --> 00:01:55,809 Over its four thousand mile course from the Andes to the Atlantic 13 00:01:55,950 --> 00:01:59,408 the Amazon is swollen by some eleven hundred tributaries. 14 00:02:00,421 --> 00:02:02,719 Several are massive rivers in their own right. 15 00:02:02,857 --> 00:02:06,759 Between them they drain forty percent of the continent. 16 00:02:08,896 --> 00:02:12,093 Three thousand kinds of fish live in this waterworld. 17 00:02:12,867 --> 00:02:15,961 And where there are fish there are fish hunters. 18 00:02:44,599 --> 00:02:46,157 Giant otters. 19 00:02:46,701 --> 00:02:51,434 They really are giants nearly two metres from nose to tail. 20 00:02:53,141 --> 00:02:58,044 Local people call them 'Iobos del rio' wolves of the river. 21 00:02:58,413 --> 00:03:00,608 They live almost entirely on fish 22 00:03:00,748 --> 00:03:03,740 though they can kill caiman and anacondas. 23 00:03:04,686 --> 00:03:07,120 They're one of the top predators of the Amazon 24 00:03:07,255 --> 00:03:09,951 the aquatic equivalent of the jaguar. 25 00:03:16,998 --> 00:03:20,832 Most otters are solitary but these are very sociable. 26 00:03:21,436 --> 00:03:24,496 They live in family groups of about half a dozen 27 00:03:25,073 --> 00:03:28,531 a mated pair and their full grown young from previous years. 28 00:03:30,011 --> 00:03:32,172 The otters bridge two worlds. 29 00:03:32,447 --> 00:03:34,278 All their food comes from the river 30 00:03:34,415 --> 00:03:37,748 but they sleep and rear their cubs on dry land. 31 00:03:39,253 --> 00:03:43,087 So their lives are profoundly affected by the changing level of the river 32 00:03:43,224 --> 00:03:45,488 which has its origins far to the west 33 00:03:45,626 --> 00:03:48,288 in the distant peaks of the Andes. 34 00:04:05,713 --> 00:04:08,546 After a first precipitous rush from the mountains 35 00:04:08,683 --> 00:04:11,311 the river's course is flat and winding. 36 00:04:12,453 --> 00:04:15,183 For the next three and a half thousand miles 37 00:04:15,323 --> 00:04:18,315 it drops barely two inches a mile. 38 00:04:19,427 --> 00:04:22,157 As sluggish meanders twist across the floodplain 39 00:04:22,296 --> 00:04:24,161 their course is constantly changing 40 00:04:24,298 --> 00:04:26,391 creating new channels and lakes. 41 00:04:28,269 --> 00:04:30,328 This is more than just a river 42 00:04:30,471 --> 00:04:32,234 it's a whole river system. 43 00:04:41,516 --> 00:04:45,111 It's October the height of the dry season. 44 00:04:45,386 --> 00:04:47,411 The Amazon is at its lowest ebb 45 00:04:47,555 --> 00:04:49,523 and showing its bare bones. 46 00:04:54,595 --> 00:04:56,460 For just a few weeks each year 47 00:04:56,597 --> 00:04:59,430 sandbanks rise clear of the water 48 00:04:59,567 --> 00:05:01,501 giving a brief window of opportunity 49 00:05:01,636 --> 00:05:04,537 for one of the Amazon's most remarkable animals. 50 00:05:16,984 --> 00:05:18,645 Giant river turtles. 51 00:05:18,786 --> 00:05:21,812 They're one of the largest fresh water turtles in the world 52 00:05:21,989 --> 00:05:25,584 over a metre long and weighing more than forty kilos. 53 00:05:27,862 --> 00:05:31,491 They come back to the same place each year to lay their eggs. 54 00:05:31,833 --> 00:05:33,596 But this is a race against time 55 00:05:33,734 --> 00:05:36,726 because the sandbanks will soon be flooded again. 56 00:05:49,517 --> 00:05:50,984 For two weeks after they arrive 57 00:05:51,118 --> 00:05:53,416 the pregnant females bask in the sun. 58 00:05:56,691 --> 00:05:58,750 This hastens the development of the eggs 59 00:05:58,893 --> 00:06:00,326 still inside their bodies. 60 00:06:08,536 --> 00:06:09,332 When she's ready 61 00:06:09,470 --> 00:06:12,564 each huge female digs a hole a metre deep. 62 00:06:13,074 --> 00:06:16,271 In it she'll lay a hundred soft-shelled eggs. 63 00:06:18,813 --> 00:06:21,782 But all this activity doesn't go unnoticed. 64 00:06:25,753 --> 00:06:28,244 Good sandbanks are few and far between 65 00:06:28,389 --> 00:06:31,552 so early clutches of eggs are often accidentally dug up 66 00:06:31,692 --> 00:06:33,421 by turtles nesting later. 67 00:06:38,766 --> 00:06:42,258 For the vultures too this is a once a year opportunity. 68 00:06:48,075 --> 00:06:49,975 But it only lasts a few days. 69 00:06:50,578 --> 00:06:52,739 The turtles will soon be gone. 70 00:07:23,511 --> 00:07:26,776 In forty five days the surviving eggs will hatch 71 00:07:26,981 --> 00:07:29,176 far quicker than other turtles. 72 00:07:31,052 --> 00:07:32,110 Just a week or two later 73 00:07:32,253 --> 00:07:34,380 the sandbanks will be drowned again. 74 00:07:35,323 --> 00:07:38,417 If the rivers rise early all the eggs are lost. 75 00:07:46,300 --> 00:07:47,824 At the peak of the dry season 76 00:07:48,002 --> 00:07:51,199 broad reaches of river can be almost cut off 77 00:07:51,339 --> 00:07:54,240 as sandbars separate them from the main flow. 78 00:07:59,714 --> 00:08:02,182 Fish become concentrated in these lagoons 79 00:08:02,316 --> 00:08:05,114 so for predators the killing is easy. 80 00:08:06,520 --> 00:08:11,048 Caiman and egrets gather to take advantage of the best hunting of the year. 81 00:08:19,800 --> 00:08:21,927 The fish take shelter in the reeds 82 00:08:22,036 --> 00:08:25,005 but in shallow water they're easier to catch. 83 00:08:30,211 --> 00:08:33,009 Striking low and from the side makes it harder 84 00:08:33,147 --> 00:08:37,015 for the egrets' prey to see them until it's too late. 85 00:08:41,789 --> 00:08:43,950 Sometimes the caiman seem to work together 86 00:08:44,058 --> 00:08:45,958 to herd fish into the shallows. 87 00:08:59,306 --> 00:09:02,605 The shoals of prey become even more concentrated. 88 00:09:15,489 --> 00:09:18,390 The water literally heaves with fish. 89 00:09:19,093 --> 00:09:20,458 With so many to choose from 90 00:09:20,594 --> 00:09:23,085 there's no need to single out a target. 91 00:09:23,664 --> 00:09:26,224 A random lunge can be just as effective 92 00:09:27,001 --> 00:09:28,593 and as each caiman strikes 93 00:09:28,736 --> 00:09:31,398 it panics fish into the jaws of another. 94 00:09:35,843 --> 00:09:37,606 But the good times won't last long. 95 00:09:37,745 --> 00:09:40,270 The caiman must make the most of them while they can. 96 00:10:08,742 --> 00:10:11,836 A feast like this could keep them going for months. 97 00:10:21,889 --> 00:10:25,188 For most fish the dry season is not a good time. 98 00:10:25,793 --> 00:10:27,624 They're on everyone's menu 99 00:10:27,761 --> 00:10:31,197 and their own food's so scarce that many will not eat for months. 100 00:10:39,340 --> 00:10:42,036 Some of the birds are having a hard time too. 101 00:10:42,743 --> 00:10:45,075 Tui parakeets are seed eaters 102 00:10:45,212 --> 00:10:49,012 and the seeds of this munguba tree are a rare treat 103 00:10:52,686 --> 00:10:55,883 The munguba uses the wind to scatter its seeds. 104 00:10:57,591 --> 00:11:00,424 Each one is carried on a parachute of fluff 105 00:11:00,561 --> 00:11:02,119 but if it lands in the water 106 00:11:02,263 --> 00:11:04,663 there's not much chance of it germinating. 107 00:11:11,505 --> 00:11:15,236 These are Brycon sometimes called South American trout. 108 00:11:22,016 --> 00:11:22,744 They're so hungry 109 00:11:22,883 --> 00:11:26,284 they jump at the chance of even these meagre mouthfuls. 110 00:11:52,580 --> 00:11:55,811 They can leap up to four times their body length. 111 00:12:12,833 --> 00:12:16,769 Even at low water the larger rivers are still navigable. 112 00:12:17,238 --> 00:12:18,728 On the Amazon's main channel 113 00:12:18,872 --> 00:12:22,069 seagoing ships can reach as far as the city of lquitos 114 00:12:22,209 --> 00:12:24,643 over two thousand miles from the ocean. 115 00:12:29,650 --> 00:12:32,312 The rivers are the main arteries of travel. 116 00:12:32,453 --> 00:12:35,320 Local people depend on them throughout the year. 117 00:12:43,097 --> 00:12:46,999 Riverside communities rely heavily on fish for their livelihood. 118 00:12:48,502 --> 00:12:51,096 For the people as for the natural predators 119 00:12:51,238 --> 00:12:54,537 low water is also the best time to make a catch. 120 00:13:06,587 --> 00:13:08,987 Laden with silt from the distant mountains 121 00:13:09,123 --> 00:13:11,114 the rivers are often very muddy. 122 00:13:12,459 --> 00:13:15,121 It's hard to see much under water during the day 123 00:13:15,629 --> 00:13:17,961 At night, the problem is even worse. 124 00:13:18,999 --> 00:13:23,095 Infra-red cameras let us follow the action in total darkness. 125 00:13:23,570 --> 00:13:26,403 But how do the fish find their way? 126 00:13:29,209 --> 00:13:32,406 Some, like these Candiru have an acute sense of smell. 127 00:13:33,347 --> 00:13:36,680 They can detect the slightest trace of blood or decay. 128 00:13:41,655 --> 00:13:45,056 Fish trapped in fishermen's nets are easy meat. 129 00:13:45,926 --> 00:13:47,291 Like aquatic vultures 130 00:13:47,428 --> 00:13:50,056 the Candiru home in on the scent of flesh 131 00:13:50,197 --> 00:13:52,791 and strip the carcass from within. 132 00:13:58,105 --> 00:14:01,939 A close relative of these Candiru has the most unsavoury reputation 133 00:14:02,042 --> 00:14:03,509 of any fish in the Amazon. 134 00:14:03,977 --> 00:14:06,377 It's a parasite rather than a scavenger 135 00:14:06,580 --> 00:14:08,639 and it's attracted to blood and urine. 136 00:14:09,483 --> 00:14:12,509 It's been known to swim right up into people's bodies 137 00:14:12,653 --> 00:14:16,521 wedging itself inside with backward-pointing spines. 138 00:14:24,231 --> 00:14:27,132 Other fish deploy much stranger senses 139 00:14:30,371 --> 00:14:33,568 ...ones that we can scarcely begin to visualise. 140 00:14:38,712 --> 00:14:42,170 They generate an electric field around their body. 141 00:14:42,516 --> 00:14:45,679 Any object in their path distorts the field. 142 00:14:46,120 --> 00:14:49,248 They detect the changes with receptors in their skin. 143 00:14:53,494 --> 00:14:56,520 This extraordinary sense allows them to find their way 144 00:14:56,663 --> 00:14:58,858 around in the murkiest of water 145 00:14:59,199 --> 00:15:01,667 and to detect and catch their prey. 146 00:15:07,074 --> 00:15:09,440 They also use it to communicate. 147 00:15:14,815 --> 00:15:18,012 Most electric fish generate a very weak field 148 00:15:18,152 --> 00:15:19,380 but not this one. 149 00:15:20,254 --> 00:15:21,243 To local people 150 00:15:21,388 --> 00:15:24,016 it's one of the most feared fish in the Amazon 151 00:15:24,391 --> 00:15:25,949 the electric eel. 152 00:15:31,598 --> 00:15:35,090 Its two metre long body is a gigantic battery. 153 00:15:35,235 --> 00:15:39,296 It can deliver a jolt of six hundred volts a shocking defence 154 00:15:39,440 --> 00:15:41,067 enough to kill a child 155 00:15:41,208 --> 00:15:43,574 and more than enough to stun its prey. 156 00:15:53,887 --> 00:15:56,117 As the rivers shrink to their very lowest 157 00:15:56,256 --> 00:15:59,020 some of the channels are entirely cut off. 158 00:15:59,293 --> 00:16:03,423 Here, predators and prey become even more concentrated. 159 00:16:06,800 --> 00:16:09,963 Territorial male caiman have put aside their differences 160 00:16:10,103 --> 00:16:12,264 to take advantage of the glut of food 161 00:16:13,073 --> 00:16:16,804 but in such cramped conditions disputes are inevitable. 162 00:16:27,588 --> 00:16:28,612 Despite the crowds 163 00:16:28,755 --> 00:16:31,053 there are still plenty of fish to go round. 164 00:16:34,528 --> 00:16:38,157 But that doesn't remove the temptation to steal someone else's. 165 00:17:07,761 --> 00:17:10,559 Even theft is scarcely worth the energy. 166 00:17:10,731 --> 00:17:12,426 The heron keeps its meal. 167 00:17:16,203 --> 00:17:18,535 For fish hunters these are the good times 168 00:17:18,672 --> 00:17:21,072 though not without their annoyances. 169 00:17:21,975 --> 00:17:23,840 Caiman may look armour plated 170 00:17:23,977 --> 00:17:26,138 but there are chinks in their defences. 171 00:17:29,650 --> 00:17:31,242 With only their heads out of water 172 00:17:31,385 --> 00:17:34,752 they're still a target for blood-sucking horseflies. 173 00:17:37,691 --> 00:17:40,524 Even a harmless butterfly can be a nuisance. 174 00:17:54,074 --> 00:17:57,202 The first showers hint at a change of season 175 00:17:57,344 --> 00:17:58,902 a promise of rising water 176 00:17:59,046 --> 00:18:01,139 and better times to come for fish now 177 00:18:01,281 --> 00:18:04,910 trapped at the mercy of predators like caiman and egret 178 00:18:12,526 --> 00:18:13,618 For the cormorants too 179 00:18:13,760 --> 00:18:16,285 the best of the fishing will soon be over. 180 00:18:18,832 --> 00:18:20,800 Released from their dry season prison 181 00:18:20,968 --> 00:18:23,937 the fish will spread out and become harder to catch. 182 00:18:24,671 --> 00:18:27,538 They'll be too scattered to feed a flock like this. 183 00:18:45,892 --> 00:18:49,419 The dry season may be coming to an end but not just yet. 184 00:18:50,764 --> 00:18:53,096 This is only an isolated shower. 185 00:18:53,367 --> 00:18:56,234 It will take much more to set the fish free. 186 00:19:00,574 --> 00:19:05,034 The first rain can even make things worse for them... much worse. 187 00:19:05,779 --> 00:19:07,337 The cold rainwater sinks 188 00:19:07,481 --> 00:19:11,713 displacing warmer and less oxygenated water below. 189 00:19:16,556 --> 00:19:21,789 Decaying vegetation and bubbles of hydrogen sulphide rise from the depths. 190 00:19:22,162 --> 00:19:25,290 This lethal cocktail makes oxygen levels plummet 191 00:19:25,432 --> 00:19:28,128 and fish are soon gasping for breath 192 00:19:30,971 --> 00:19:33,633 The topmost film of water where it touches the air 193 00:19:33,774 --> 00:19:35,537 still has the most oxygen 194 00:19:35,676 --> 00:19:39,544 so desperate fish skim the surface to avoid suffocation. 195 00:19:51,558 --> 00:19:54,459 Most kinds of fish seem to be affected. 196 00:20:05,772 --> 00:20:06,397 For the birds 197 00:20:06,540 --> 00:20:09,703 this may be the last opportunity to make a killing. 198 00:20:19,920 --> 00:20:24,254 The distressed fish are easy prey for the cormorants and egrets. 199 00:20:33,433 --> 00:20:37,301 With so much on the menu they ignore the dead and dying 200 00:20:37,704 --> 00:20:40,036 but not all of these will go to waste. 201 00:20:44,644 --> 00:20:45,406 For the vultures 202 00:20:45,545 --> 00:20:48,275 this is another brief window of opportunity. 203 00:20:49,382 --> 00:20:53,842 Fish kills are sudden and short-lived and the dead fish soon sink. 204 00:20:55,589 --> 00:20:58,490 Black vultures have an acute sense of smell. 205 00:20:58,625 --> 00:21:03,153 The stench of rotting fish draws them to the feast in increasing numbers. 206 00:21:24,918 --> 00:21:27,478 There is too much even for the vultures. 207 00:21:27,621 --> 00:21:32,058 The victims of this natural disaster can number tens of thousands. 208 00:21:45,038 --> 00:21:48,872 Isolated local showers turn to more general rain. 209 00:21:54,247 --> 00:21:58,650 The Amazon basin gets a massive three metres of rain a year 210 00:22:00,053 --> 00:22:03,284 most of it concentrated in just a few months. 211 00:22:05,992 --> 00:22:07,857 The timing of the rainy season varies 212 00:22:07,994 --> 00:22:10,963 from one part of this vast catchment to another 213 00:22:11,097 --> 00:22:13,065 but the result is the same everywhere 214 00:22:13,333 --> 00:22:16,234 a slow but inexorable rise in the river level. 215 00:22:22,676 --> 00:22:26,874 The changing season has a profound effect on everything that lives here. 216 00:22:27,047 --> 00:22:29,641 Swollen by the rain that falls within the basin 217 00:22:29,783 --> 00:22:32,183 the rivers are soon full to the brim. 218 00:22:40,660 --> 00:22:42,355 But there's more to come. 219 00:22:46,633 --> 00:22:48,464 In the cloud forests of the Andes 220 00:22:48,602 --> 00:22:52,663 the annual rainfall can be an incredible six metres. 221 00:23:00,714 --> 00:23:03,581 When that joins with snowmelt from the high peaks 222 00:23:03,717 --> 00:23:05,708 the results are dramatic. 223 00:23:35,548 --> 00:23:38,244 It may be days or even weeks before these torrents 224 00:23:38,385 --> 00:23:41,149 make their full impact on the floodplain forest 225 00:23:41,288 --> 00:23:43,279 hundreds of miles to the east. 226 00:23:45,725 --> 00:23:48,592 But already, animals are on the move. 227 00:23:54,467 --> 00:23:57,630 The rain that has already fallen here waterlogs the soil 228 00:23:57,771 --> 00:23:59,295 and raises the humidity 229 00:23:59,773 --> 00:24:02,571 and that triggers a remarkable migration. 230 00:24:10,650 --> 00:24:14,609 The small creatures of the leaf litter move upwards, into the trees. 231 00:24:16,189 --> 00:24:19,090 Soon, their world will be transformed. 232 00:24:27,834 --> 00:24:31,531 But up in the treetops predators are waiting for them. 233 00:25:08,174 --> 00:25:09,698 For many of the leaf litter animals 234 00:25:09,843 --> 00:25:12,368 the shift to the treetops proves fatal. 235 00:25:12,645 --> 00:25:14,203 So why do they move? 236 00:25:21,654 --> 00:25:23,349 It can take two months 237 00:25:23,490 --> 00:25:27,449 but finally the rain and snowmelt from the Andes make their mark. 238 00:25:28,061 --> 00:25:30,552 The rivers are already full from rain in the lowlands 239 00:25:30,697 --> 00:25:32,324 and can take no more. 240 00:25:32,632 --> 00:25:35,157 Now they overflow into the forest. 241 00:25:39,339 --> 00:25:43,400 The reason for that mass migration from the leaf litter becomes clear. 242 00:25:43,543 --> 00:25:46,706 The forest floods to a depth of ten metres. 243 00:25:48,882 --> 00:25:50,975 The flood changes the lives of everything 244 00:25:51,084 --> 00:25:52,312 that lives here. 245 00:25:53,820 --> 00:25:56,311 Even the giant otters are on the move. 246 00:25:57,023 --> 00:25:59,787 Their dry season dens are now underwater 247 00:25:59,959 --> 00:26:02,553 so they have to move their young to higher ground. 248 00:26:04,264 --> 00:26:07,290 This year's cubs are still too small to swim far 249 00:26:07,434 --> 00:26:10,062 so the adults carry them in their jaws. 250 00:26:26,686 --> 00:26:28,551 Giant otters are territorial 251 00:26:28,688 --> 00:26:32,954 and the group's range has to include dens for both low and high water. 252 00:26:51,277 --> 00:26:54,713 The whole family share the task of looking after the young. 253 00:26:56,082 --> 00:26:58,744 It will be two or three years before their elder brothers 254 00:26:58,885 --> 00:27:02,150 and sisters leave to start a family of their own. 255 00:27:10,497 --> 00:27:13,625 Few predators will tackle a full grown giant otter 256 00:27:13,766 --> 00:27:17,827 but infants can be killed especially by caiman. 257 00:27:40,160 --> 00:27:42,060 Safely installed in their new home 258 00:27:42,195 --> 00:27:45,961 the otters will stay here until the floodwater recedes. 259 00:27:53,406 --> 00:27:54,737 At the height of the flood 260 00:27:54,874 --> 00:27:57,240 Amazonia is transformed. 261 00:27:57,844 --> 00:28:00,472 An entirely new habitat has been created 262 00:28:00,613 --> 00:28:02,945 a waterworld that can drown the forest 263 00:28:03,082 --> 00:28:06,984 for ten miles either side of the main river channel. 264 00:28:17,797 --> 00:28:19,355 At the peak of this inundation 265 00:28:19,499 --> 00:28:25,062 the rivers engulf an incredible fifty seven thousand square miles of forest 266 00:28:25,205 --> 00:28:27,730 an area the size of England. 267 00:28:31,878 --> 00:28:35,575 The trees can stand in water for six months or more. 268 00:28:35,848 --> 00:28:38,510 But this drowning is something that happens every year 269 00:28:38,651 --> 00:28:41,484 and many will turn the flood to their advantage. 270 00:28:51,364 --> 00:28:55,300 Branches where birds once perched now shelter fish. 271 00:28:56,002 --> 00:28:58,766 Freed from the dry season confines of the riverbed 272 00:28:58,905 --> 00:29:00,896 they spread out into the forest. 273 00:29:01,941 --> 00:29:04,432 This is their season of plenty. 274 00:29:16,222 --> 00:29:18,383 Predators follow the fish into the forest 275 00:29:18,524 --> 00:29:21,015 but now it's much harder for them to hunt. 276 00:29:21,227 --> 00:29:22,660 Their prey are more scattered 277 00:29:22,795 --> 00:29:24,922 and have more places to hide. 278 00:29:27,767 --> 00:29:32,329 The hunters include one of the Amazon's most remarkable animals. 279 00:29:35,642 --> 00:29:37,166 The Boto dolphin. 280 00:29:37,810 --> 00:29:40,210 This river dolphin is almost blind 281 00:29:40,346 --> 00:29:44,043 but the water here is often so muddy that eyes are useless. 282 00:29:44,183 --> 00:29:47,744 It finds its way through the branches by using sonar. 283 00:29:49,222 --> 00:29:52,953 Unlike its marine relatives it has a very flexible neck 284 00:29:53,092 --> 00:29:57,620 so it can sweep its head from side to side to scan the water ahead 285 00:29:57,997 --> 00:30:00,022 and to catch fish. 286 00:30:20,219 --> 00:30:22,585 Because there is so much decaying vegetation 287 00:30:22,722 --> 00:30:26,488 the water in the flooded forest is very low in oxygen. 288 00:30:27,994 --> 00:30:30,588 That's no problem for an air-breathing dolphin 289 00:30:30,730 --> 00:30:32,925 but how do fish survive here? 290 00:30:35,935 --> 00:30:39,962 The Pirarucu is the largest freshwater fish in the world. 291 00:30:40,973 --> 00:30:42,565 It can grow to three metres 292 00:30:42,709 --> 00:30:46,042 and weigh nearly a hundred and fifty kilos. 293 00:30:48,781 --> 00:30:52,217 Like the dolphin this giant has to breathe air. 294 00:30:56,155 --> 00:30:56,985 Every few minutes 295 00:30:57,123 --> 00:31:00,320 it comes to the surface and takes a gulp of oxygen. 296 00:31:01,861 --> 00:31:04,625 All sorts of other fish share this ability. 297 00:31:08,401 --> 00:31:12,360 The electric eel absorbs oxygen through the lining of its mouth. 298 00:31:14,540 --> 00:31:16,235 It acts like a lung. 299 00:31:18,845 --> 00:31:22,747 Many of the Amazon's fish have a high concentration of red blood cells 300 00:31:22,882 --> 00:31:24,975 which makes their gills more effective 301 00:31:25,118 --> 00:31:27,416 but they also take air from the surface. 302 00:31:34,360 --> 00:31:38,592 A swamp eel traps great gulps of air in its inflated throat. 303 00:31:45,772 --> 00:31:47,262 Animals that live in the trees 304 00:31:47,407 --> 00:31:51,104 also need special skills to survive in the flooded forest 305 00:31:51,244 --> 00:31:53,075 like being able to swim. 306 00:32:03,289 --> 00:32:06,690 Sloth and spider may seem unlikely swimmers 307 00:32:06,826 --> 00:32:09,590 but their own form of freestyle is now the best way 308 00:32:09,729 --> 00:32:11,287 for them to move between trees. 309 00:32:26,579 --> 00:32:30,310 If you can't swim, climb or fly you can't stay here 310 00:32:31,217 --> 00:32:33,981 so this waterworld has none of the usual forest animals 311 00:32:34,120 --> 00:32:36,213 like deer or peccaries. 312 00:32:43,796 --> 00:32:45,354 The sloth may not be fast 313 00:32:45,498 --> 00:32:47,898 but it's a good swimmer and climber. 314 00:32:59,745 --> 00:33:03,112 The most unexpected creatures take to the water. 315 00:33:05,885 --> 00:33:09,412 Fire ants even turn the flood to their advantage. 316 00:33:11,557 --> 00:33:13,752 When their forest floor nests are drowned 317 00:33:13,893 --> 00:33:15,952 they set sail on a living raft 318 00:33:16,062 --> 00:33:19,122 formed from their own inter-linked bodies. 319 00:33:26,739 --> 00:33:28,001 Drifting with the current 320 00:33:28,140 --> 00:33:31,166 they can end up far away from their old home. 321 00:33:32,378 --> 00:33:35,245 All they need for a new colony is on the raft 322 00:33:35,381 --> 00:33:38,475 including the next generation. 323 00:33:42,455 --> 00:33:44,787 But the voyage has its hazards. 324 00:33:46,125 --> 00:33:48,025 Fire ants have a painful sting 325 00:33:48,160 --> 00:33:50,094 but that doesn't stop fish picking them off 326 00:33:50,229 --> 00:33:52,026 as they drift through the forest. 327 00:34:08,614 --> 00:34:11,777 Eventually the rafting ants make landfall. 328 00:34:13,486 --> 00:34:16,546 This tree will provide a refuge until the waters fall 329 00:34:16,689 --> 00:34:20,352 and they can return once more to the forest floor. 330 00:34:25,197 --> 00:34:26,687 If their eggs are to survive 331 00:34:26,832 --> 00:34:30,268 they must find shelter from the drying heat of the sun. 332 00:34:39,545 --> 00:34:42,571 A crack in the bark is a perfect nest site 333 00:34:45,184 --> 00:34:47,880 and the tree comes with a built-in food supply. 334 00:34:49,288 --> 00:34:51,415 Others have already taken refuge here. 335 00:34:51,557 --> 00:34:54,685 They arrived even before the flood had started. 336 00:35:01,233 --> 00:35:03,667 The lizard has now got competition. 337 00:35:14,780 --> 00:35:17,340 These insects are all on the fire ant menu 338 00:35:17,483 --> 00:35:20,145 but they seem strangely reluctant to jump. 339 00:35:25,858 --> 00:35:27,826 Those that do take the plunge may find 340 00:35:27,994 --> 00:35:31,327 that they've leapt from the frying pan into the fire. 341 00:36:04,096 --> 00:36:06,496 Fish are quick to take advantage of any insects 342 00:36:06,632 --> 00:36:08,293 that fall into the water. 343 00:36:08,968 --> 00:36:11,061 For some, like the metre-Iong Aruana 344 00:36:11,203 --> 00:36:13,364 they're a large part of their diet. 345 00:36:19,679 --> 00:36:21,579 The fish may not have eaten for months 346 00:36:21,714 --> 00:36:24,342 so now it's time to fatten up. 347 00:36:27,720 --> 00:36:30,518 Wind and rain dislodge a steady supply of insects 348 00:36:30,656 --> 00:36:32,954 from the crowded canopy above. 349 00:36:40,266 --> 00:36:42,461 Even if it's not actually in the water 350 00:36:42,601 --> 00:36:45,434 an insect still may not be safe. 351 00:36:52,211 --> 00:36:55,806 All sorts of other fish make the most of the windfalls. 352 00:36:57,650 --> 00:37:01,552 Needle fish cruise the surface picking off anything small. 353 00:37:04,957 --> 00:37:06,652 Like some other fish in the Amazon 354 00:37:06,792 --> 00:37:10,922 and the dolphins these little fish have a marine origin. 355 00:37:13,799 --> 00:37:16,359 They spend most of their time near the water surface 356 00:37:16,502 --> 00:37:17,969 hunting by sight. 357 00:37:18,537 --> 00:37:22,268 That slim profile may help to camouflage them. 358 00:37:32,618 --> 00:37:36,145 Their long 'beak' is ideal for seizing prey. 359 00:37:40,793 --> 00:37:42,818 The rising water triggers an event 360 00:37:42,995 --> 00:37:46,396 that will affect the lives of almost everything that lives here. 361 00:37:58,410 --> 00:38:01,971 It's now that the trees in the flooded forest fruit. 362 00:38:16,962 --> 00:38:20,398 Many trees depend on the flood to disperse their seeds. 363 00:38:21,133 --> 00:38:22,498 By the time they germinate 364 00:38:22,635 --> 00:38:26,071 the water will have carried them far away from their parent tree. 365 00:38:27,540 --> 00:38:31,806 But drifting with the flow isn't the only way seeds can travel. 366 00:38:34,513 --> 00:38:36,140 In this strange new world 367 00:38:36,282 --> 00:38:39,513 some trees use fish to scatter their seed. 368 00:38:42,087 --> 00:38:44,317 The fish eat the fleshy part of the fruit 369 00:38:44,456 --> 00:38:47,425 but the hard seeds pass through their gut unharmed. 370 00:39:02,508 --> 00:39:04,533 This is a good time for fish. 371 00:39:04,677 --> 00:39:07,237 They gather wherever fruit falls. 372 00:39:09,748 --> 00:39:12,911 And where there are fish there are fishers. 373 00:39:26,265 --> 00:39:28,130 Most of the predatory birds have gone 374 00:39:28,267 --> 00:39:31,566 but not this one a little green heron. 375 00:39:49,054 --> 00:39:52,455 Most fruit-eaters have an equal partnership with the trees. 376 00:39:52,591 --> 00:39:55,389 They spread their seeds in return for food. 377 00:40:00,099 --> 00:40:02,465 But some fish don't play by the rules. 378 00:40:04,103 --> 00:40:05,627 They eat the seeds 379 00:40:05,771 --> 00:40:09,639 crunching them up and destroying rather than dispersing them. 380 00:40:10,976 --> 00:40:16,073 Tambaqui have a powerful sense of smell to lead them to fruiting trees. 381 00:40:23,122 --> 00:40:25,022 They have powerful jaws, too 382 00:40:25,157 --> 00:40:29,992 well able to crush hard seeds such as this walnut-like supacaio. 383 00:40:31,397 --> 00:40:34,833 Little of what they eat will ever get the chance to germinate. 384 00:40:51,684 --> 00:40:54,778 The flood is also a good time for the Uakari. 385 00:40:58,724 --> 00:41:02,592 These monkeys live in loose groups of thirty to fifty. 386 00:41:05,130 --> 00:41:07,030 They seldom come down to the ground 387 00:41:07,166 --> 00:41:11,432 preferring to travel through the treetops in elegant leaps and bounds. 388 00:41:13,272 --> 00:41:14,830 So when the forest floods 389 00:41:15,007 --> 00:41:16,736 they have no need to swim. 390 00:41:22,648 --> 00:41:26,015 These bizarre monkeys live only in floodplain forests 391 00:41:26,151 --> 00:41:29,552 where they take full advantage of the flush of new fruit. 392 00:41:55,080 --> 00:41:58,049 Local people call this 'the English monkey'. 393 00:41:58,350 --> 00:42:01,786 Its red face reminds them of a gin-swilling white man 394 00:42:01,987 --> 00:42:04,114 who's been out too long in the sun. 395 00:42:04,390 --> 00:42:06,950 In fact the red face is a sexual signal 396 00:42:07,026 --> 00:42:09,859 a sign of potency and good health. 397 00:42:12,831 --> 00:42:14,731 Uakaris are one of the few monkeys 398 00:42:14,867 --> 00:42:18,030 that live in this riverine forest all year round 399 00:42:18,170 --> 00:42:21,367 surviving on leaves and unripe fruit. 400 00:42:21,707 --> 00:42:22,799 With their strong jaws 401 00:42:23,008 --> 00:42:26,569 they can tackle food that would be too tough for other animals. 402 00:42:32,918 --> 00:42:36,877 The seasonal flooding of the forest leaves nothing untouched. 403 00:42:37,056 --> 00:42:40,685 Everything that lives here has to adapt... or move on. 404 00:42:41,326 --> 00:42:44,659 Remarkably people stay here right through the year. 405 00:42:44,797 --> 00:42:47,630 Their houses are built on stilts or rafts 406 00:42:47,766 --> 00:42:49,529 to raise them above the flood 407 00:42:49,668 --> 00:42:51,693 as are their chicken coups. 408 00:43:07,686 --> 00:43:09,517 Watering the plants may be easy 409 00:43:09,655 --> 00:43:13,785 but a floating platform is now the only place to grow vegetables. 410 00:43:14,593 --> 00:43:16,220 This is a challenging time. 411 00:43:16,361 --> 00:43:18,352 Most people depend on fish 412 00:43:18,497 --> 00:43:21,830 but the shoals of the dry season are scattered through the forest 413 00:43:22,000 --> 00:43:24,161 and so harder to catch. 414 00:43:27,806 --> 00:43:31,173 All sorts of predator are having a hard time. 415 00:43:31,777 --> 00:43:37,374 Even fearsome hunters like piranhas are reduced to scavenging for scraps. 416 00:43:41,520 --> 00:43:43,215 Of all the Amazon's fish 417 00:43:43,355 --> 00:43:46,449 these have the most notorious reputation. 418 00:43:47,426 --> 00:43:50,156 They could strip a chicken to the bone in seconds 419 00:43:50,295 --> 00:43:52,855 if it were careless enough to fall in. 420 00:44:07,679 --> 00:44:10,273 Living on the water does have some advantages 421 00:44:10,415 --> 00:44:12,246 at least for children 422 00:44:12,384 --> 00:44:13,578 though most of us wouldn't 423 00:44:13,719 --> 00:44:16,017 want piranhas in our swimming pool. 424 00:44:19,491 --> 00:44:20,185 In fact 425 00:44:20,325 --> 00:44:23,021 their ferocious reputation is undeserved. 426 00:44:23,162 --> 00:44:24,527 Only in the dry season 427 00:44:24,663 --> 00:44:26,961 when they're concentrated in landlocked pools 428 00:44:27,099 --> 00:44:28,794 are they truly dangerous 429 00:44:30,002 --> 00:44:32,334 So for now it's safe to swim. 430 00:45:25,891 --> 00:45:27,654 People can live without dry land 431 00:45:27,793 --> 00:45:31,160 at least for a while but otters can't. 432 00:45:31,730 --> 00:45:35,427 They need a dry den to sleep in and rear their young. 433 00:45:36,602 --> 00:45:38,729 They're now deep in the flooded forest 434 00:45:38,870 --> 00:45:40,770 well away from the open river 435 00:45:40,906 --> 00:45:43,397 hunting fish hidden in the trees. 436 00:45:46,845 --> 00:45:49,712 The easy times of the dry season may have gone 437 00:45:49,848 --> 00:45:52,976 but otters are supreme predators. 438 00:45:59,458 --> 00:46:01,926 Their webbed feet and paddle-like tails 439 00:46:02,027 --> 00:46:06,964 their strength and agility make them a match for even the most elusive fish. 440 00:46:38,997 --> 00:46:42,091 If fish are hard pressed to escape an otter hunting alone 441 00:46:42,234 --> 00:46:46,034 they're even less able to get away when they hunt as a pack. 442 00:46:51,276 --> 00:46:53,176 Often the whole family fishes together 443 00:46:53,312 --> 00:46:55,644 driving their prey into a tight shoal 444 00:46:55,781 --> 00:46:57,806 or trapping them against a bank. 445 00:47:06,091 --> 00:47:07,615 The rewards of communal fishing 446 00:47:07,759 --> 00:47:10,990 are one of the most important benefits of family life. 447 00:47:20,105 --> 00:47:21,265 Over the months to come 448 00:47:21,406 --> 00:47:24,466 the floodwater will slowly drain from the forest. 449 00:47:24,810 --> 00:47:27,779 The rivers will once again be confined to their channels 450 00:47:27,979 --> 00:47:31,278 and the otters will return to their dry season dens. 451 00:47:37,456 --> 00:47:40,948 Giant otters are an indicator of a healthy river. 452 00:47:41,059 --> 00:47:43,391 Only where they have a plentiful supply of fish 453 00:47:43,528 --> 00:47:46,691 and can live undisturbed do they survive. 454 00:47:54,139 --> 00:47:57,575 There are many threats to the world's last wild places 455 00:47:57,709 --> 00:48:01,372 but the sheer scale of the Amazon could be its salvation. 456 00:48:01,513 --> 00:48:06,041 It's far too mighty to control dam, or divert. 457 00:48:08,653 --> 00:48:11,178 The massive yearly flood makes it a hostile home 458 00:48:11,323 --> 00:48:13,587 for all but a few people 459 00:48:13,725 --> 00:48:19,220 and means this watery wilderness may always remain untamed.