探索亞馬遜 雨林頂端.doc

Journey into Amazonia: The Big TopNGC全民英檢:探索亞馬遜雨林頂端播出時(shí)間:11月5日 星期六 11:00-12:00The rainforest of Amazonia-where life in all its beauty and myriad formsreigns supreme.Less known then the surface of Mars,its inhabitants stranger than science fiction.this is Earths final, unexplored frontier.This is Amazonias Big Top!The worlds mightiest riverbreaks through the canopyof the largest tropical rainforeston the planet.Combined with its tributaries,the Amazon drains into an areaof almost seven million square kilometres-more than half of South America.Like a giant circus tentnine times the size of Texas,Amazonias tree covered worldhosts the greatest variety of plantsand animals on the planet.Sixty meters above the ground,less studied than the sea floor.Until recently, this incredible spectacledefied even the most intrepid scientistsand explorers.So many of its riches have yet to be recordedthat it is believed that this bizarreand beautiful canopy could househalf of all the worlds species.In addition to millions of insects,Amazonias impressive cast of charactersincludes at least 300 different mammals.At least one hundred seventy-fivedifferent lizards.Over four hundred reptiles and amphibians.Tree climbers of every shape and size, And a third of the worlds birds.These magnificent creaturesall have their own unique tricks and talents,costumes and camouflage,and command performances.A 100 years ago the American explorer,William Beebe, wrote of the Amazon:Yet another continent of liferemains to be discovered,not upon the earth,but one or two hundred feet above it,extending over thousands of square miles.There awaits a rich harvestfor the naturalist who overcomes the obstacles-gravitation, ants, rotten trunks-and mounts to the summit of the jungle trees.Since Beebe marvelledat this incredible spectacle,scientists have had to multiply-many times over- all previous estimatesof the extent of life in these treetops. Only recently, the sheer number of termiteshas come to light- More than 200 speciescall the Amazon river basin their home-a cumulative massthree times that of all the birdsand mammals in the rainforest.Yet almost a hundred years laterAmazonia is revealing her secrets slowlylike crumbs from a giants banquet table.For a vast number of species,the canopy of this tropical rainforestis a desirable place to live.With so many creatures clamouringfor a piece of the pie in this high-wire world,competition for survivalin this big top is fierce.Millions of years of neck-and-neck rivalrymean that these animalshave evolved their own unique strategiesfor survival in the rainforest canopy.Evolution has led the slothup a more leisurely ladderto its place in the canopy.With only half the musclesof other animals its size,the sloth subsists on one of the poorest diets.This languid mammalcan take up to a monthto travel two kilometres.if it had to.Although it can stand,it cant walk on its feet,so it must drag itself around by its hands.In the water, however,this lazy beast becomes somethingof a Bathing Beauty and can swim quite well.Avoiding any strenuous competition for food,the three-toed sloth selects the leavesand twigs only a few other animals can stomach.With this low-cal diet,the sloth has little energy to spare,so it sleeps up to nine-teen hours a day.It locks itself under a hard-to-reach branchto digest-it will take a hundred hoursto process a single belly full.Its ability to rotate its headalmost full circle means this contortionistcan keep an eye out for predators.Its also the only wild animalto have plants living on it.Each hair has microscopic grooveswhich provide a comfortable homefor olive-green algae.Its believed that these plants-and its extended naps-help camouflage the slothfrom its chief predator, the Harpy eagle.Sloths give birth to a single baby-which spends six to nine monthsclinging to its mother.Three-toed sloths are not normally aggressive,but like any mother defending her child,she has a trick or two up her sleeve.You are what you eat in the Rainforestand leaf-eaters fall low on the list.The largest monkeys in the New World,the howler monkeys are not finickywhen it comes to food, which may explainwhy they are also the most common monkeyin Amazonia. It hasnt turnedto the low-calorie extremes of the sloth,but it eats poorer farethan just about any other monkey.Like the sloth, the Howlers slow metabolismforces them into the top-most branchesof the canopy where they can warm upin the morning sunshine and jumpstart their day.They rarely explore much of the forestand when they do, they cover less distancethan other monkeys in the Amazonian Basin.Less energetic. Less fastidious.Less curious.Howlers do one thing more loudlythan just about any other land animal:Howl.In fact, these guttural soundscan travel up to five kilometresthrough the dense forest.It is said that when the first explorerspenetrated the depths of the rainforest,and heard the howlers calls,they fled in terror-fearing that some monster had encircled them.Oddly, these bellicose howls and hootsactually kept the peace by defining territoryand keeping the monkey troopsout of conflict.Standing one meter high,weighing in at eight kilos,with a two meter wingspan,the Harpy Eagle is unequalled in strength.According to Greek mythology,the Harpies were half-woman,half-bird monsters which swooped downfrom the heavens to seize the soulsof the dead and punish them.Today its a tamarin that facesthe most powerful talons of any bird on earth.Unassailable, the Harpy Eagleheadlines Amazonias Big Top.Beneath the multi-layered worldof the canopy, the groundlingscompete for survival.But in the tropics,physical conflict is often a dangerousand deadly last resort.Millions of disease-promoting organismswill invade even the most minor injury,causing fatal infections.Avoiding conflict is a constant pre-occupationin nature, especially here.To avoid surprise encounters,the animals repeatedly announce their presence. While howlers use soundto signal to other groups-the tiny squirrel monkey has evolveda less raucous though no less discreet method.It urinates on its hands and feetto leave its personal signature-a chemical barcode-as it scampers along the branches.But no system is foolproof,and where animals compete for resources,disputes over real estate are inevitable.Although its heavier than the squirrel monkey,the capuchins tail cant grip as strongly.Its completely outmatched.Despite putting up a good fight,it flees the canopyand escapes to the forest floor.Sometimes the reason for these boutsis unclear- especially when the participantsarent obvious competitors-such as parrots and monkeys.According to Indian mythology,the golden-handed tamaringot its conspicuous markingsfrom having to roll out the sun each morning.Tamarins are naturally inquisitive.They like to know what the neighboursare up to.This golden-handed tamarin, however,takes its curiosity to dangerous lengths.Teasing the neighbouring macaws.But the macaws are not amused.Their powerful claws and nut-cracker beaksmake this a risky game of cat and mousefor the tamarin.Out-numbered, the tamarindecides it is time to quitwhile its still ahead.The tamarin is only a minor distraction.The macaws have other, more important mattersto attend to- The breeding seasonis approaching, so the two birdsget in the mood by preening each othersfeathers and faces.They will mate and pair for life. The macaws are some of the forestsmost extravagantly conspicuous inhabitants.But for each known rainforest species,there are many more unknown species.Yet all these creature play a rolein the jungles intricate dramaof interdependence.In the give and take tradings of Amazoniathe most intricate relationshipsin the rainforest are between animals and trees.In this competitive market,leaves are the commonest currency.Some trees produce toxinsto repel insect invaders,but at a cost that drains the treeof valuable energy.Other trees have developeda more diplomatic solution.Theyve struck up an armisticewith some of the ants.These trees provide one particular kind of antwith room and board. At the base of each leafs stem,special nectar spouts provide the antswith a steady supply of high-energy drinks.In return the tiny ant vigilantesact as neighbourhood watchand defend the tree from attack.They will even take on and drive awaythe far larger leaf-cutters.The arrangement suits both parties.Scratch my back and Ill scratch yours.or in this case Feed me sweetsand Ill bite the legs of your enemy.Such interdependence providesa strategic advantage in a deceptively lushenvironment, because its more difficultto survive than it looks.On the darkened forest floor,the lack of sunlight strangles many plants.At the other extreme, the top-most branchesrisk being seared by the sun.But somehow, despite everything.Life thrives.April, and the storm cloudsroll in again across the mantle of Amazonia.The dry season is over.The annual deluge sweeps across the whole faceof this epic wilderness.The waterworlds reassert their dominanceover the land, bringing new life.Aquatic prey and predators,like the giant otters, return to feast.The mighty Amazon and its tributariesescape their banks, taking holdof the land and submergingalmost 350,000 square kilometres,and area larger than Englandto a depth of over ten meters.Here, amidst the flooded forests,the most dramatic events in the lifeof the canopy will soon unfold.The surging water-levels encourage the treesto put on a dazzling displayof floral fireworks.The flooded forests make uponly a small fraction of Amazonia-only two percent- but almost halfof all the flowering trees and plantsin the entire rainforest grow and bloom here.The sudden explosion of colourattracts an equally phenomenalconcentration of life.Sixty meters up in the air,the stage is set for a spectacular flower show.The rains have just begun to slowand the trees begin to reproduce.Flowers will light up these forests continuallyfor the next six to eight months,but the individual bloomswill only last for two weeks at a time.The rain forest has one big thing on its mind-sex.A thick and heady scent fills the air.The variety of colour and formis equally intoxicating.But how does the gene-laden pollenin these flowers fertilize other plants?Its important that the right messengerdelivers the right pollento the right flower.So the forest giants turn to tiny allies.Insects are the most numerous creaturesof the rainforest-perhaps thirty million in all.In this mating game, most pollinatorsare insects, like butterflieswhich flutter and flirtwith one flower and then another.But how do you bring brand loyaltyto the butterfly brain of an insect?The flowers drive this processby luring tiny allieswith their decadent colours,sumptuous scents, and voluptuous shapes.and discourage the less desirable visitors.But insects are not the only cupidsin this complex sex-life beneath the canopy.Hummingbirds, among the smallestwarm-blooded creatures in the world,are the guardian angels of flower nectar.Only a high-energy fuel such as nectarcan drive a metabolism with a heartbeatten times as fast as a humans.Each flower delivers only a few dropsof precious nectar.The hummingbird- like a tropical Cupid-is just one of the many pagesassisting the reproductive liaisonsthat go on beneath the Big Top.Pollen is not the hummingbirds only cargo.Tiny stowaways hitch lifts from bloom to bloom.With so little time at each stopover,these hungry flower mitesmust race up and down to the next meal.It is the equivalent of a hundred-yard dash. In addition to allies,the trees have enemies too.One of the many reasons they needto produce blooms in such profusionis because of flower thieves.These monkeys arent helpingwith the forests fertilization process.Theyre neither pollinating the flowersnor spreading seeds.To do that, the trees have to lookto other rainforest creatures for assistance,and they do it day and night.Evening comes, but this does not meanthat activity ceases. far from it.While others are preparing to wind-down,a whole range of animalsare waking to begin their day.As the night falls, the howler monkeysmake their final calls, and woolly monkeysput on an evening performance of gymnastics.High in the tree-topsthe twenty-four hour circus never sleeps.When one act ends another begins.Its time for the late show.Another cast takes over in the Big Top.The nightshift is beginning-the pollination must go on. The still air fills with the cloying perfumeof night-blooming flowers.Unlike the vivid colours of flowers of the day,these nocturnal blooms wear white.Drab by day, at nightthey come splendidly into their own.Instead of relying on colour,they rely on fragrance to attract visitors.They get fewer takers,but their visitors tend to be more loyal.During the day, flowers attract insectsand birds- but flowers of the nightlure very different clients.More than half of bats in the Amazondepend on plants for their food.These bats use echo locationto navigate the night sky.By producing ultrasound wavesthat bounce off of objectsand produce patterns which help the batsfind their food.They are colour blind,so garish bouquets would be wasted on them.These night flowers need to be largeand conspicuous to be spotted more easily.Its a brief encounter.The plant dusts pollen onto the batas it drinks.Bats and plants get mutual satisfaction-but attracting the wrong sort of attentionis as much a problem at night as it is by day.From the plants point of view,its precious pollen is wastedon a ravenous caterpillar.Bats dont just transfer pollenand fertilise flowers.They provide an important service to the forestby spreading the trees seeds.First the trees bribe the insects, birds,and bats with food and nectarto travel from plant to plant.Now they must spread their seeds somehow.Time for a new incentive: Fruit.This bat gorging on the pulpy fruitof an inga has only one concern-to eat as much as it can.It is oblivious to any assistanceit might bring to the plant.Bats are not the only performance artistswho can hang upside down.A wily Amazonian racooncan always find a wayto reach inaccessible fruit.The kinkajou has its prioritiesthe right side up- but what does the treeget out of the arrangement?Plants produce these deliciousand nutritious gifts at great personal cost-and they need the best start in lifethat they can get. if they are to survive.Any offspring that doesnt fall far enoughfrom the tree can face many difficulties.Its rare that a sapling will survive close by. Only by hitching a ride inside the stomachof a passing animal can the seedstravel away from their parent treeto where conditions may be more favourable.Birds, bats, monkeys, fish, and this kinkajouare all unwitting cargo carriers.The kinkajou and the seedswill be far away when the next day dawns.The flowering crowns of the Amazonian rainforestare a feast for the eyes,but with the harvest that follows,the banqueting truly begins.By day, monkeys take overwhere bats and kinkajous left off.They ransack the heavily laden branches.They are only too pleasedto indulge in the canopys succulent bribes.In doing so, they too will help spreadthe seeds of the trees which will, in turn,literally support their existence.With food so readily available,many species of the canopywill bear their young at this time of year.Its easier now to feed a growing family.This baby attaches itself to its mothers fur,and will get a free ridefor the first six months of its life.Woolly monkeys, like howlers,rarely, if ever, descend to the ground.These youngsters are constantly on the moveand always at risk.Their mothers keep a wary eye out for danger.Rivalries and real estate disputesare set aside for the moment.Young monkeys are favourite preyof forest predators,especially if they too have young to feed. The Harpy eagle breeds at this time of yearas well.The chick hatches after 2 months of incubation.It takes a lot to raise the demanding babywhich must be fed for at least ten months-and the parents will wait another 2 or 3 yearsbefore nesting again.Meanwhile, they bring monkeys, sloths,the occasional reptile and a few birdsfor their fledgling.In Amazonia, the nest will almost invariablybe placed in the fork of the highest treewith an uninterrupted viewof the top of the hunting groundsin the canopy below.With fruiting, the next stageof the forests regeneration has begun.Some birds are allies in this process,but others like the macaw are not.Parrots are seed-destroyers,rejecting the flesh in favour of the seedsthemselves.The tree uses chemical warfarein its defence.seeds containing bitter toxi