行星地球第八集：富饒叢林 Jungles

[00:32.31]This is our planet's hothouse. The jungle. [00:35.52] [00:35.85]The tropical rainforest. [00:38.39] [00:40.54]Forests like these occupy only three percent of the land [00:44.14] [00:44.25]yet they're home to over half of the world's species. [00:48.51] [00:49.64]But how do so many different kinds of plants and animals [00:53.27] [00:53.37]find the space here to live alongside one another? [00:57.17] [01:08.78]On the dark, humid forest floor the jungle appears to be lifeless. [01:14.62] [01:15.62]Often the only signs of life are what you hear. [01:19.63] [01:25.92]A male blue bird of paradise is advertising for a mate. [01:30.50] [01:32.35]It's quite a performance [01:33.83] [01:33.91]but he's not the only bird of paradise here keen to make an impression. [01:38.92] [01:40.18]There are nearly forty different kinds on the island of New Guinea [01:43.80] [01:43.87]each with a display seemingly more bizarre than the rest. [01:47.81] [01:56.48]A riflebird of paradise. [01:59.28] [02:08.85]Like many jungle animals, birds of paradise avoid competing with each other [02:13.86] [02:13.86]and these do so by living in different parts of this jungle covered island. [02:19.38] [02:24.56]The six plumed bird of paradise displays in his special clearing, on the forest floor. [02:31.48] [02:37.62]The magnificent bird of paradise favors the low branches of bushes. [02:43.14] [02:46.45]His female is modestly dressed. [02:50.11] [03:01.17]The male has a good set of lungs [03:03.71] [03:03.77]but he'll have to do more than flutter his eyelids, if he wants to impress her. [03:08.96] [03:15.03]It'll all depend on his performance. [03:17.44] [03:22.38]The females may be dull looking but they're very picky [03:26.13] [03:27.92]and it's time for a really close inspection. [03:31.53] [03:36.83]His right side looks fine... but what about his left? [03:41.50] [03:45.32]Pretty impressive, but is he magnificent enough? [03:49.66] [03:51.57]Oh dear. Her departure says it all. [03:54.83] [03:55.42]Generations of choosy females have driven the evolution [03:59.35] [03:59.45]of these remarkable displays. [04:01.71] [04:02.73]The more extravagant a male is, the more likely he'll be noticed. [04:07.33] [04:31.98]New Guinea lies in a warm tropical belt that girdles our planet around the equator. [04:38.27] [04:38.62]With abundant rainfall and twelve hours of daylight [04:41.88] [04:41.96]three hundred and sixty five days a year, it's here that rainforests flourish. [04:48.23] [04:52.85]Surprisingly only two percent of the sunlight filters down to the forest floor. [04:59.02] [05:00.87]Down here seedlings struggle to grow [05:04.80] [05:05.17]but the gloom is not eternal. [05:08.14] [05:40.28]The death of a forest giant is always saddening [05:44.19] [05:44.40]but it has to happen if the forest is to remain healthy. [05:48.79] [05:50.34]The sudden blaze of sunlight will bring life to the forest floor. [05:56.26] [05:59.24]A single hectare of rainforest may contain as many as 250 species of tree. [06:05.20] [06:05.37]That's nearly ten times the number that grow in Britain [06:08.52] [06:08.77]and the thirst for light triggers a race for a place in the sun. [06:13.96] [06:28.88]There's no time to waste. [06:30.71] [06:30.79]A seed that may have fallen only a few days ago, now bursts through the leaf litter. [06:37.35] [06:50.68]With so many competitors, getting a good start is critical [06:55.83] [06:57.75]but each plant has it's own particular strategy [07:01.39] [07:01.57]for making the most of this rare opportunity. [07:05.10] [07:05.91]The seeds of hardwoods are quick to germinate [07:08.60] [07:08.76]but, like the fabled tortoise, their strategy is to be slow and steady. [07:14.09] [07:18.53]Vines and other climbers put all their energy into rapid vertical growth, rather than girth [07:25.49] [07:25.68]though they'll need to be well supported. [07:28.61] [07:34.33]The climbers' strategy looks chaotic but there's method in their madness. [07:38.77] [07:38.81]Their growing tips circle like lassoes, searching out anchors for their spindly stems. [07:45.53] [07:51.74]They put coils in their tendrils [07:53.83] [07:53.96]so that if their support moves, they will stretch and not snap. [07:58.25] [08:00.78]But the frontrunners at this stage, the first to fill the clearing, [08:04.58] [08:04.73]are pioneers like the macarangas. [08:07.82] [08:08.76]Their immense leaves capture huge amounts of sunlight, so fueling their growth. [08:14.97] [08:20.79]As a result the macarangas grow a remarkable eight meters a year [08:25.13] [08:25.21]surging ahead of almost all their rivals. [08:28.73] [08:40.93]In the race for the top spot hundreds will start [08:44.55] [08:44.67]yet few will ever reach the finishing line, their growth cut short by the diminishing light. [08:51.25] [08:53.65]In less than four years, the gap will have gone [08:57.42] [08:57.72]but that's not the end of the race. [09:01.10] [09:09.35]The ultimate winners are the tortoises, the slow and steady hardwoods. [09:15.45] [09:17.24]When the short lived pioneers have fallen [09:20.30] [09:20.54]it's the hardwoods that take their place, and a fifty meter giant, like this one, [09:26.00] [09:26.20]may keep it's place in the sun for another two hundred years. [09:31.52] [10:06.94]At the top, is the canopy, the engine room of the jungle. [10:11.09] [10:11.36]It's up here that most of the animal life in the rainforest can be found [10:16.81] [10:17.67]But despite the apparent abundance of vegetable food, gathering it is seldom easy. [10:25.04] [10:37.94]With no real seasons [10:39.84] [10:40.20]each tree flowers or fruits at a different time of the year [10:44.26] [10:44.32]which means that food is very widely spaced. [10:48.45] [10:53.27]Monkeys, like these tamarinds, must search the canopy for all kinds of food [10:58.40] [10:58.61]if they're to survive. [11:00.62] [11:03.09]but across the world's rainforests there's one type of fruiting tree [11:07.97] [11:08.05]that always delivers: the fig. [11:11.98] [11:20.92]Wherever they grow, figs are a magnet for the great diversity of animals. [11:27.03] [11:29.06]In the Amazon, the first to appear are the spider monkeys. [11:33.69] [11:34.97]These large primates are big fig eaters [11:38.12] [11:38.21]But they won't have the tree to themselves for long. Others will want a share. [11:43.48] [11:44.52]like the diminutive emperor tamarinds. [11:47.81] [11:50.97]The tamarinds love figs too, but being petite means they're easily scared off. [11:57.00] [12:06.79]Squirrel monkeys are also small but they have strength in numbers. [12:11.71] [12:14.03]Their timeshare on the tree may be short, so their tactics are more smash and grab. [12:19.94] [12:28.55]Capuchin monkeys are the bully boys in these forests [12:31.89] [12:32.05]and they want the ripe figs for themselves. [12:35.45] [12:52.12]Figs are one of the few trees that fruit the year round [12:56.13] [12:56.60]so when other food is scarce, these fruits are always available somewhere or other. [13:03.08] [13:06.86]Even for leaf eaters, like howler monkeys the ripe figs are just too good to miss. [13:12.69] [13:18.43]And howlers are too big for the capuchins to chase off. [13:23.29] [13:26.77]Figs are so popular, that as many as 44 different kinds of bird and monkey [13:32.07] [13:32.19]have been seen working a shift system on a single tree. [13:36.67] [13:45.26]Because fruiting trees are so valuable, many monkeys are territorial [13:50.92] [13:51.08]And if you live in the treetops [13:52.85] [13:52.95]there's perhaps no better way of staking your claim to a territory, than this. [13:58.10] [14:03.97]The calls of the siamang gibbons begin as a duet [14:07.82] [14:07.82]between the dominant male and female. [14:10.36] [14:22.49]The rest of their families soon join in, and it results in a frenzy of activity. [14:28.58] [14:36.72]The calls can carry over a mile, and their message is clear. [14:42.08] [14:46.74]They tell any neighboring siamangs this is our territory. Keep out. [14:51.99] [15:01.81]Up here the calls of siamang gibbons seem to dominate the airwaves [15:07.16] [15:07.20]but with the jungle's incredible diversity [15:09.97] [15:09.97]there are countless others trying to be heard too. [15:13.29] [15:19.25]Every layer seems to beat to a different tune. [15:23.92] [15:40.32]In the early morning the forest's chorus is particularly rich. [15:44.76] [15:45.03]Sounds travel further in the cooler air [15:48.81] [15:52.27]But few calls can penetrate as far through the dense vegetation as this one [15:58.34] [15:58.50]the deep bass solo of a male orangutan. [16:02.78] [16:17.82]In the middle of the day little stirs in the jungle [16:21.14] [16:21.20]and the hot dense air muffles the sound. [16:25.70] [16:28.10]As the afternoon wears on, a different set of players begin to warm up. [16:33.58] [16:35.62]Insects work in harmony, timing their calls to fall between the notes of others. [16:41.80] [16:49.19]Many singers stick to precise schedules [16:52.13] [16:52.33]and right on cue the six o'clock cicadae. [16:56.26] [17:08.05]Night brings out a whole new orchestra. [17:11.89] [17:35.45]The cacophony of competing calls seems deafening to us [17:39.85] [17:40.03]but frogs ears are tuned to hear only the calls of their own kind. [17:45.81] [17:52.61]The songs of courtship echo from all around. [17:56.85] [18:09.20]Male gliding leaf frogs leap from the treetops. [18:14.66] [18:47.99]To slow their descent, they use their huge webbed feet as parachutes. [18:54.54] [18:58.68]These large tree frogs spend most of their lives in the high canopy [19:03.46] [19:03.56]and only come down when it's time to breed. [19:07.19] [19:12.44]Once settled, they begin to serenade their unseen females. [19:17.51] [19:28.81]Now it's time for the females to make their move. [19:33.02] [19:37.21]There's no shortage of suitors, but this female has already made her choice. [19:42.14] [19:42.14]She's heading towards the loudest call, because loud calls come from big frogs [19:47.88] [19:48.35]and big is best, but to reach him she must run the gauntlet of a gang of smaller suitors. [19:55.84] [19:56.25]Their only chance of mating is to make a sneaky interception. [20:00.99] [20:06.30]He's scored. [20:07.71] [20:07.85]But with more females arriving all the time, it's not over until the fat frog stops singing. [20:14.69] [20:20.72]Feet, so vital for gliding, are now put to other uses. [20:26.17] [20:31.00]Two's company, three's inconvenient [20:35.29] [20:35.50]but in any case, all male frogs are equipped with dry thumbs [20:40.00] [20:40.14]which enable them to get a vice like grip on their moist partners. [20:44.80] [20:46.09]It's a case of first come first served. [20:50.32] [20:57.77]Living in such a humid environment, means jungle frogs are less tied to puddles and pools [21:04.27] [21:04.45]and these even lay their eggs out of water. [21:07.91] [21:17.32]There's little chance of them drying out [21:19.78] [21:20.11]and up here they're safer from predators. [21:23.83] [21:30.83]Surprisingly, it doesn't rain every day in the rainforest [21:35.46] [21:36.11]but more still falls here than anywhere else on Earth. [21:39.75] [21:40.12]On average, over two meters a year. [21:43.11] [21:52.90]A single tree can suck up hundreds of tons of water each year [21:58.60] [22:00.97]But the trees can't use all this water [22:03.29] [22:03.41]so, much of it returns to the air as vapor, forming mist and clouds. [22:09.84] [22:14.85]In the Amazon, the largest unbroken stretch of rainforest in the world, [22:19.55] [22:19.74]half of all the rainwater that falls, comes from clouds produced by the trees themselves. [22:26.74] [22:57.72]With so much rain, it's not surprising that many of the worlds largest rivers [23:03.14] [23:03.32]are found in rainforests. [23:05.99] [23:20.44]Inside the forest, the high humidity [23:23.50] [23:23.60]creates the perfect conditions for a strange world, where life is built on decay. [23:31.29] [23:42.72]Amoeba like slime molds cruise the surface, feeding on bacteria and rotting vegetation. [23:51.10] [24:06.45]Fungi also flourish on decay. [24:10.48] [24:11.79]These are the fruiting bodies of the fungi, the only visible sign [24:16.69] [24:16.80]of a vast underground network of fungal filaments. [24:21.95] [24:52.08]In temperate forests, the buildup of leaf litter creates rich stores of nutrients. [24:57.59] [24:57.80]That however, doesn't happen here. [25:00.59] [25:04.23]Nutrients that reach the soil are leeched out by the rain [25:08.24] [25:08.28]but fungi are connected to tree roots by their underground filaments [25:12.62] [25:12.78]and by quickly consuming the dead [25:14.86] [25:14.90]they help to recycle crucial minerals straight back into the trees. [25:20.34] [25:26.73]And this recycling happens faster here, than anywhere else on the planet. [25:32.69] [25:51.87]There are thought to be nearly a million different types of fungi in the tropics. [25:56.98] [25:57.10]The vast majority still unknown to science [26:01.38] [26:07.34]But one thing's for certain [26:09.64] [26:09.83]without fungi, rainforests could not exist. [26:14.65] [26:25.26]Nothing goes to waste in the rainforest. [26:28.13] [26:28.37]The fungi become food for others like these beetle larvae. [26:33.03] [26:37.17]Finding the fungus isn't a problem for the grubs [26:40.14] [26:40.22]since their caring parents actually show them the way. [26:44.62] [26:57.40]Incredibly, 80% of all insects live in jungles [27:02.47] [27:02.84]fewer more successful than the ants. There can be 8 million individuals in a single hectare. [27:09.41] [27:10.70]but jungle ants don't have it all their own way. [27:14.67] [27:21.14]These bullet ants are showing some worrying symptoms. [27:26.19] [27:26.76]Spores from a parasitic fungus called cordyceps [27:30.46] [27:30.50]have infiltrated their bodies and their minds. [27:34.68] [27:40.79]It's infected brain directs this ant upwards [27:45.49] [27:46.91]then, utterly disorientated, it grips a stem with it's mandibles. [27:52.02] [27:52.49]Those afflicted, that are discovered by the workers [27:55.55] [27:55.55]are quickly taken away and dumped far away from the colony. [27:59.82] [28:01.35]It seems extreme, but this is the reason why. [28:06.01] [28:07.50]Like something out of science fiction [28:10.22] [28:10.37]the fruiting body of the cordyceps erupts from the ant's head. [28:15.80] [28:29.77]It can take three weeks to grow [28:32.17] [28:32.52]and when finished, the deadly spores will burst from it's tip [28:36.98] [28:37.20]then, any ant in the vicinity will be in serious risk of death. [28:42.45] [28:44.65]The fungus is so virulent, it can wipe out whole colonies of ants [28:49.11] [28:49.52]and it's not just ants that fall victim to this killer. [28:53.32] [28:55.36]There are literally thousands of different types of cordyceps fungi [28:59.94] [29:00.08]and remarkably, each specializes on just one species [29:05.92] [29:40.23]but these attacks do have a positive effect on the jungle's diversity. [29:45.01] [29:45.28]Since parasites like these stop any one group of animal getting the upper hand. [29:51.61] [29:52.08]The more numerous a species becomes, the more likely it'll be attacked by it's nemesis [29:57.39] [29:57.51]a cordyceps fungus. [29:59.96] [30:22.88]With so much competition, jungles have become the home of the specialist. [30:28.60] [30:28.82]Now this animal, in the island of Borneo, is one of the most unusual. [30:33.87] [30:34.59]It's a colugo, or flying lemur, though this is something of a misnomer [30:39.59] [30:39.60]as it doesn't actually fly and it certainly isn't a lemur [30:43.52] [30:43.69]in fact nobody's quite sure who it's closest relative is. [30:48.59] [31:07.34]The colugo depends on a diet of young leaves [31:11.13] [31:11.27]and to find enough of them, it must move from tree to tree. [31:15.77] [31:17.26]The leaves are not very nutritious, but then, getting around doesn't use much energy. [31:23.63] [31:29.23]In a single night, a colugo might have to travel as far as two miles [31:33.95] [31:34.01]but that task is made easier by it's superior gliding skills. [31:39.55] [32:10.19]The secret of success in the competitive jungle is specializing [32:14.69] [32:14.81]and this has led to the evolution of some very intimate relationships [32:19.12] [32:19.12]between plants and animals. [32:22.44] [32:23.28]These are pitcher plants also from Borneo. [32:27.51] [32:32.48]Adapted to living in very low nutrient soils [32:36.27] [32:36.45]the pitcher plant gets most of it's nourishment from insects lured to nectar glands [32:41.60] [32:41.76]on the underside of the lids. [32:44.45] [32:45.55]Once onboard, the waxy sides of the pitcher ensure there's little chance of escape. [32:51.70] [32:54.83]Most slip to a watery grave. [32:58.49] [33:05.66]At the bottom of the pitcher glands secrete enzymes [33:09.81] [33:09.94]which help to digest the corpses, so feeding the plant. [33:14.70] [33:15.57]But not all visitors have a fatal attraction to the pitchers. [33:19.65] [33:20.75]The red crab spider spends it's entire life in the pitchers, hanging on with threads of silk. [33:28.22] [33:36.77]Instead of building a web, it relies on the water filled pitcher to trap it's food. [33:42.75] [33:45.28]When an ant falls in, the spider simply waits for it to drown [33:49.92] [33:50.08]and then abseils down for a spot of fishing. [33:54.42] [34:00.87]Alive, this ant would be far too dangerous for the spider to tackle [34:05.03] [34:05.15]so, using the pitchers as traps, means it can get bigger meals [34:11.03] [34:12.76]and the spider doesn't rob the pitcher of everything. [34:15.78] [34:15.92]The digested remains of it's booty will end up in the water [34:19.62] [34:19.77]providing instant food for the plant. [34:23.12] [34:27.09]Other food, like mosquito larvae, seems to be out of reach [34:31.53] [34:31.61]but the spider has another sup rising trick. [34:34.67] [34:34.93]By taking it's own air supply trapped in a bubble [34:38.05] [34:38.17]the crab spider can actually dive to the very bottom of the pitcher. [34:43.14] [34:46.15]Once the prey is captured, the spider hauls itself back up it's silken safety line. [34:52.99] [34:59.89]The pitcher is a one stop shop for this spider, but it's not alone. [35:05.43] [35:05.75]In the jungle there's competition for everything, even a small water filled pitcher plant. [35:11.52] [35:27.05]Such specialists create the jungle's remarkable diversity [35:31.73] [35:32.14]but finding enough food to survive is so challenging [35:35.29] [35:35.40]that most animals living here tend to be small [35:38.43] [35:38.69]though there are exceptions. [35:41.08] [35:48.53]This is the Congo in Africa. [35:51.89] [35:52.13]It's a vast wilderness and the least explored of all jungles. [35:57.57] [35:59.87]From up here the forest looks similar to the ones that grow in the Amazon or Southeast Asia. [36:05.65] [36:06.22]but down below there are some unexpected sights. [36:10.51] [36:27.66]Crisscrossing this forest, are countless miles of highways [36:32.56] [36:32.71]and they were made by something big. [36:36.13] [36:45.10]Forest elephants roam great distances in their search for food [36:49.93] [36:50.30]but to survive, they must emerge from the gloom of the forest. [36:55.30] [36:56.77]And clearings like this one, are a magnet for elephants from far and wide. [37:03.02] [37:56.70]These elephants live in much smaller groups than their savanna cousins. [38:02.06] [38:02.59]This might be the first time that one group will have seen another for a month. [38:08.29] [38:17.41]For the adult males it's a welcome break in an otherwise largely solitary existence [38:24.35] [38:32.09]and they're not the only animals attracted to the clearing. [38:36.00] [38:38.46]Forest buffaloes and red river hogs are also regular visitors [38:43.92] [38:44.30]as are bongos, which are very difficult to see outside these clearings. [38:49.56] [38:50.08]All these large forest animals have come here to collect an essential element of their diet [38:55.87] [38:56.03]that lies buried beneath the mud. [38:58.90] [39:03.42]And the elephant's trunk is the perfect tool for reaching it. [39:08.31] [39:21.88]To get what they seek [39:23.29] [39:23.29]the prospecting elephants must first blow away the covering layer of silt. [39:28.62] [39:49.86]Satisfaction at last. [39:52.67] [39:57.45]They're collecting a particular kind of clay [40:00.36] [40:00.48]that contains vital minerals scarce in their natural diet. [40:04.62] [40:04.90]It may be mud, but there's just nothing quite like it for enriching the blood. [40:10.91] [40:11.90]The clay also helps to absorb the toxins found in many leaves that the elephants eat. [40:18.36] [40:23.73]There are other benefits to coming here. [40:26.60] [40:27.40]These clearings are the only places where the forest elephants [40:30.53] [40:30.53]can get together in such numbers. [40:33.32] [40:33.50]When they return to the forest, they will have to go their separate ways, once more. [40:39.57] [40:59.24]If large animals are rare in jungles [41:02.39] [41:02.52]then groups of large animals actually living together, are even rarer. [41:08.05] [41:26.03]This posse of hunters is not only formidable, it's also very large. [41:32.79] [41:51.30]In their search for food chimpanzees move effortlessly [41:55.49] [41:55.49]between the forest floor and the canopy. [41:58.44] [41:58.60]They're one of the few jungle animals able to do so. [42:02.61] [42:16.64]Figs are a vital part of a chimpanzee's diet [42:20.55] [42:20.92]and some just can't seem to get enough of them. [42:24.89] [42:34.05]But there's something special about this stretch of forest in Uganda. [42:38.20] [42:38.28]Fruit is actually abundant [42:41.11] [42:46.49]and a lot of food supports lots of chimps. [42:51.09] [43:07.01]At a hundred and fifty strong, this community of chimps [43:10.92] [43:10.92]is the biggest yet found in Africa. [43:13.63] [43:13.79]Their numbers are so large, that they need a big territory, lots of fig trees [43:19.04] [43:19.16]and they're willing to fight for it. [43:21.59] [43:30.52]These calls announce the start of a raid into land controlled by their neighbors. [43:36.55] [43:42.58]As they leave their core zone, the patrol goes silent, occasionally stopping to listen. [43:49.40] [43:53.55]Signs of the enemy are detected and examined closely. [43:59.11] [44:12.65]The chimp militia are now at the very edge of their territory. [44:17.61] [44:18.35]All need to be on maximum alert. [44:21.93] [44:29.89]Then it's wait and listen. [44:32.86] [44:53.48]An unfamiliar chimp call raises the tension. [44:57.49] [44:57.56]It's an uncertain time. The size of the rival group is as yet unknown. [45:04.70] [45:07.12]Not far away the neighbors are feeding in a fig tree [45:10.69] [45:11.01]oblivious to the approaching dangers. [45:14.19] [45:15.49]The patrol moves off with a sense of purpose. [45:19.11] [45:19.13]They must remain silent until they close in on their rivals. [45:22.86] [45:34.91]The attack is on. [45:36.66] [45:39.13]To intimidate their opponents, the aggressors scream and drum on buttress roots. [45:44.89] [46:04.33]Several males corner an enemy female. [46:07.42] [46:07.42]It's a ferocious attack, and she's lucky to escape with her life. [46:12.21] [46:28.80]Others are not so fortunate. [46:31.53] [46:37.55]The battle won, a grizzly scene unfolds. [46:41.68] [46:42.54]An enemy youngster has been caught and killed. [46:45.66] [46:45.90]The carcass is shared between members of the group, and eaten. [46:51.27] [46:54.41]Killing a competitor makes sense if you want to protect your food supply [46:59.44] [47:02.51]but exactly why they cannibalize the dead chimp, is not fully understood. [47:07.50] [47:08.54]It may simply be a chance for some extra protein. [47:13.30] [47:24.34]Teamwork has brought this group of chimps great success [47:28.35] [47:28.53]but they'll soon reach the limits of their power. [47:32.30] [47:33.07]The competition for resources ensures that no one species dominates the jungle. [47:39.89] [47:46.16]The rainforest's great diversity has come at a cost. [47:50.13] [47:50.31]It has made them the most finely balanced ecosystems in the world [47:54.30] [47:54.49]only too easily upset and destroyed by that other great ape [47:59.31] [47:59.55]the chimpanzee's closest relative [48:02.30] [48:02.62]Ourselves. [48:05.90]

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