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  • In 1796, Thomas Jefferson received a box of bones he couldn't identify.

    1796 年,湯瑪士・傑弗遜收到一盒骨頭,他無法辨別其中的骨頭為何者

  • A long, sharp claw reminded him of a lion,

    又長又尖的爪子讓他想起獅子

  • but the arm bones suggested a larger animal,

    但從臂骨判斷,應該是身形更長的動物

  • one about three meters long.

    身長約莫有三尺長

  • Thinking it might be huge unknown species of North American lion,

    猜測可能是隸屬北美獅類的大型不知名品種

  • Jefferson warned explorers Lewis and Clark

    傑弗遜警告路易斯與克拉克兩位考察家

  • to keep an eye out for this mysterious predator.

    多留心注意這神秘的掠食者

  • But Jefferson's box of bones didn't come from a lion.

    但傑佛遜盒子內的骨頭來源並非是一頭獅子

  • They came from an extinct giant sloth.

    而是來自已滅絕的巨型樹懶

  • Prehistoric ground sloths first appeared around 35 million years ago.

    史前陸地樹懶初次出現於三千五百萬年前

  • Dozens of species lived across North, Central and South America,

    當時住在北、中、南美的許多種

  • alongside other ancient creatures like mastodons

    與其他古生物像是乳齒象

  • and giant armadillos.

    與巨型犰狳

  • Some ground sloths, like the megalonychidae, were cat-sized,

    有些陸地型樹懶,像是大地樹懶,體型似貓

  • but many were massive.

    但多數體型龐大

  • Jefferson's sloth, Megalonyx, weighed about a ton,

    傑弗遜收到的樹懶遺骨 — 巨爪地懶,體重約一噸

  • and that was small compared to megatherium,

    和大地樹懶相比,巨爪地懶體型已經算小了

  • which could reach six metric tons, as much as an elephant.

    大地樹懶可達六公噸,近似於一隻大象的重量

  • They ambled through the forests and savannas using their strong arms

    大地樹懶在森林、草原漫步,使用強而有力的手臂

  • and sharp claws

    及尖銳的腳爪

  • to uproot plants and climb trees,

    把植物連根拔起與爬樹

  • grazing on grasses, leaves, and prehistoric avocados.

    採食青草、樹葉與史前酪梨

  • In fact, we might not have avocados today if not for the giant sloths.

    事實上,假如沒有巨型樹懶,我們今日可能沒有酪梨

  • Smaller animals couldn't swallow the avocado's huge seed,

    小型動物無法吞食酪梨的大種子

  • but the sloths could,

    但樹懶辦得到

  • and they spread avocado trees far and wide.

    牠們不斷散播酪梨子,散播得又遠又廣

  • Ground sloths flourished for millions of years,

    大地樹懶世代綿延數百萬年

  • but around 10,000 years ago, they started disappearing

    但差不多在一萬多年前,大地樹懶開始漸漸消失

  • along with the Western Hemisphere's other giant mammals.

    跟著其他西半球的大型哺乳類一同消失在地球上

  • Researchers think that ground sloths could have been pushed out

    研究者認為,大地樹懶可能遭到

  • by an oncoming ice age,

    接續的冰河時期所排斥

  • or competition with other species, maybe humans,

    或是跟其他物種競爭,可能是人類

  • who arrived in the region around the time most of the sloths went extinct.

    人類約莫在這個時期到達樹懶生存區域,與樹懶絕種的時期恰好吻合

  • Some of the smaller sloths did survive and migrated to the treetops.

    有些小型樹懶存活下來,但移居到樹上

  • Today, there are six species left living in the rainforest canopies of Central and South America.

    如今,六種樹懶族群生活在中南美洲雨林的樹冠層

  • Hanging out in the trees is a good way to avoid predators,

    在樹上遊蕩是避免天敵的好方法

  • and there are plenty of leaves to eat.

    而且樹冠層上有許多樹葉可以吃

  • But this diet has its drawbacks.

    但這樣的飲食方式也有缺點

  • Animals extract energy from food and use that energy to move around,

    動物從食物中萃取能量,能量讓動物有力量移動

  • maintain their body temperature,

    維持體溫

  • keep their organs working,

    保持器官運作

  • and all the other activities necessary for survival.

    以及其他涉及生存相關的必要活動

  • But leaves don't contain much energy,

    但樹葉並無法帶給樹懶的身體許多能量

  • and that which they do have is tough to extract.

    而樹懶攝取的食物又很難萃取出能量

  • Most herbivores supplement a leafy diet with higher energy foods

    許多草食動物攝取的「素食餐」以高能量食物為主

  • like fruit and seeds.

    像是水果和種子

  • But sloths, especially three-toed sloths, rely on leaves almost exclusively.

    但樹懶,特別是只有三指樹懶,大多只攝取樹葉而已

  • They've evolved finely tuned strategies for coping with this restricted diet.

    樹懶演化成能完美調整的策略來應對如此拘束的飲食方式

  • First, they extract as much energy from their food as possible.

    首先,牠們盡其所能從食物中萃取能量最大值

  • Sloths have a multi-chambered stomach that takes up a third of their body,

    樹懶擁有多腔胃,幾乎佔整個身體的三分之一空間

  • and depending on the species,

    不同種類的樹懶

  • they can spend five to seven days, or even weeks, processing a meal.

    可能花五到七天,甚至幾個禮拜,來消化一餐

  • The other piece of the puzzle is to use as little energy as possible.

    另外一個秘訣是使用越少能量越好

  • One way sloths do this is, of course, by not moving very much.

    其中一個樹懶運用的方法,毋庸置疑的就是,盡量不要移動

  • They spend most of their time eating, resting, or sleeping.

    牠們大多數的時間都用在吃、休息與睡覺

  • They descend from the canopy just once a week for a bathroom break.

    牠們每週只會從樹冠層下來一次,只為了洗澡上廁所

  • When sloths do move, it's not very fast.

    樹懶移動的時候,速度並不快

  • It would take a sloth about five minutes to cross an average neighborhood street.

    樹懶會花費將近五分鐘橫越平均一條道路

  • This unhurried approach to life means that sloths don't need very much muscle.

    如此不疾不徐的生活方式讓樹懶不需常常用到肌肉

  • In fact, they have about 30% less muscle mass than other animals their size.

    事實上,和同樣體型大小的動物相比,樹懶的肌肉量少約百分之三十

  • Sloths also use less energy to keep themselves warm

    樹懶也運用很少能量來維持體溫

  • because their body temperature can fluctuate by about five degrees Celsius,

    因為牠們的體溫能夠有攝氏五度左右的變動調整

  • less than a cold-blooded reptile, but more than most mammals.

    比冷血爬蟲類變動幅度小,但比多數哺乳類還要大了

  • These physical and behavioral adaptations minimize the sloth's energy expenditure,

    這些生理與習慣適應縮減了樹懶的能量支出

  • or metabolic rate.

    或代謝率

  • Three-toed sloths have the slowest metabolism of any mammal.

    三指樹懶的代謝率是所有哺乳類中最慢的

  • The giant panda is second slowest,

    巨型熊貓則排名哺乳類第二慢

  • and two-toed sloths come in third.

    而兩指樹懶則名列第三慢

  • Moving slowly has allowed sloths to thrive in their treetop habitat.

    移動緩慢讓樹懶得以在樹冠層棲地繁榮發展

  • But it's also made the sloths themselves a great habitat for other organisms,

    但如此一來也為其他有機類生物提供良好的棲地

  • including algae, which provides a little extra camouflage, and maybe even a snack.

    包含藻類,提供樹懶一點額外的掩護,甚至成為小點心

  • Sloths may not be giant anymore,

    或許樹懶不再如此巨大

  • but that doesn't make them any less remarkable.

    但這並未減損樹懶引人注目的特質

In 1796, Thomas Jefferson received a box of bones he couldn't identify.

1796 年,湯瑪士・傑弗遜收到一盒骨頭,他無法辨別其中的骨頭為何者

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B2 中高級 中文 美國腔 TED-Ed 樹懶 大地 能量 巨型 樹葉

【TED-Ed】真實的樹懶真的像動物方城市裡一樣動作緩慢嗎? (Why are sloths so slow? - Kenny Coogan)

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    Anita Lin 發佈於 2017 年 06 月 01 日
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