(音樂)
Sea turtles are miraculous. First, they've been around since the late Jurassic, roughly 150 million years ago. Cohorts of the dinosaurs, sea turtles have survived through the challenges of eons, existing still today, where many others have ended their evolutionary run. Second, throughout the centuries and up till today, every living adult sea turtle has overcome the odds, existing as a consequence of chance, skill, and capability. The gauntlet each sea turtle faces in the course of its lifetime goes thus: First, deposited as a clutch of leathery, ping-pong ball-sized eggs into a nesting pit dug by its mother high on the beach, of the 50 to 200 eggs laid, roughly 20 percent will never hatch. Roughly a month and a half after having been laid, the surviving eggs hatch, and the young turtles, each small enough to fit in the palm of your hand, squirm to the surface, emerging from the sand en masse, and making their desperate dash for the sea. Along the way, debris, pitfalls, crabs, gulls, raccoons, and other threats will claim roughly 50 percent of those who rose from the sand. For those that actually reach the surf, they trade one set of threats for another, as they first face the repelling force of the waves, and then find a whole new host of predators awaiting them: Various fish, dolphins, sharks, and sea birds, as the young turtles come to the surface for air. For their first few days of life, should they count themselves amongst the living, the vulnerable turtles swim frantically forward. Ultimately, they will often look to settle in a patch of flotsam, preferably a patch of floating seaweed. Now for the next several months, they will seek to avoid those that would eat them, find that which they might eat themselves, and not fall to the pressures of challenging weather or unfortunate currents. In this phase, roughly 50 percent of those who reach the surf will perish. Ultimately, with the passage of years, the survivors will increase in size, from that of a dinner plate at year one to that of a dinner table, in the case of one species at least, the leatherback, a decade or so later. With size comes some measure of protection. The only truly worrisome predators now are some of the larger shark species-- bulls, tigers, and whites -- and the occasional killer whale. At approximately two decades of age, the survivors will be old enough themselves to breed, and continue the cycle which their very existence heralds. Of those that began as eggs on a distant beach, now less than 10 percent remain, at least, those were the odds prior to significant human interference. Over the past century, and in particular in the last several decades, human endeavors, from beach development to plastic refuse to poaching, long lines, nets, and even noxious chemicals, including oil, have upped the ante for sea turtles, causing their survival rate to drop to around one percent or less, from each nesting cycle. It is this added human pressure which has pushed each of the eight sea turtle species into either a threatened or endangered state. For while they have evolved to overcome a host of obstacles, the most recent has arisen so quickly and at such scale that the species find themselves overwhelmed. So let's quickly recap this cycle of odds. Using a hypothetical nesting season, for females may nest multiple times in a single year, of 1,000 eggs, for sake of ease. 1000 eggs laid. 800 hatch. 400 make it to the water. 200 progress toward adulthood. 20 survive to breeding age -- that is, without human interference. Two survive to breeding age with human interference. So a breeding adult sea turtle is the very embodiment of a long shot. It is the exception, not the rule. A jackpot. It is, in a very real sense, a miracle.
海龜是奇蹟般的動物 第一,牠們自侏羅紀末就出現在這個世界 大約 1 億 5000 萬年前 身為恐龍的同伴,海龜倖存下來,並存活了長達億年 存活至今日,反觀牠的同伴卻結束了演化的旅程 第二,在過去幾個世紀直到今天 每隻成功存活的成年海龜都克服了難關 牠們的存活總歸機運、技能、及能力 牠們的存活總歸機運、技能、及能力 每隻海龜在牠一生中面臨的挑戰有: 首先,海龜媽媽於海灘高處挖出的窩裡 產下一窩革質、乒乓球大小的蛋 一窩 50-200 蛋中 大約 20%不會孵化 產卵後過了一個半月 還存活的蛋孵化 成為小海龜,每隻比你的手掌要來得小 一群新生命爬上地表 然後開始猛烈地衝向海洋 一路走來,碎片、 坑洞、 螃蟹、 海鷗、 浣熊和其他威脅 會奪走大約 50% 從沙裡爬出的小海龜的生命 會奪走大約 50% 從沙裡爬出的小海龜的生命 對於那些成功抵達浪潮的 牠們將面臨新的威脅 牠們第一次面對海浪的衝擊 然後發現新的獵食者正等待著他們 各種魚類、 海豚、 鯊魚 還有當他們浮出水面呼吸所遇上的海鳥 牠們生命的前幾天 若牠們僥倖活存 脆弱的海龜會瘋狂地向前游 最後,牠們往往會在一團漂浮物下定居 最好是在浮在水面的海草 接下來幾個月,牠們會設法避開天敵 尋找獵物 並不被惡劣的天氣或海洋的亂流所擊倒 在此階段,大約 50% 進入海洋的海龜會死亡 在此階段,大約 50%進入海洋的海龜會死亡 最後,經過了幾年 存活下來的海龜將會慢慢長大 體型從第一年的盤子大小,變成餐桌大小 舉棱皮龜為例,過程可能需要十年以上 舉棱皮龜為例,過程可能需要十年以上 體型變大會帶來一些保護的功用 現在唯一令牠擔憂的掠食者是一些較大的鯊魚: 牛鯊、 虎鯊、大白鯊 和偶爾碰到的殺人鯨 到了約二十歲時 存活下來的海龜將成熟到有繁殖能力 繁衍下一代,見證生命週期的循環 在那些沙灘上的龜卵之中 能活到繁殖年齡的不到一成 至少那是於人類破壞之前的機率 在過去這世紀,特別是在過去的幾十年裡 人類的活動,如開發海灘 塑膠垃圾、盜獵、延繩釣、網捕、 甚至有毒化學品(包括石油) 讓海龜存活下來的困難性增加 導致每一代新生海龜的存活率下降到 百分之一左右或更少 人類所施加的生存壓力讓世界上的八種海龜 都處於受威脅甚至瀕臨絕種的狀態 雖然演化天擇使牠們能夠克服種種障礙 但最近的障礙急速增加 速度如此之快讓海龜無法應變 速度如此之快讓海龜無法應變 現在,讓我們快速回顧海龜在一生中存活的機率 我們利用一個產卵季節來計算 因為母龜可以在一年中多次產卵 為了方便假設牠一次產下 1,000 顆卵 1,000 顆卵之中 800 顆會孵化 400 隻成功進入海洋 200 隻逐步長大至成年 20 隻活到繁殖年齡──這是沒有人為干預的結果 在人為干擾下,只有兩隻會活到繁殖年齡 所以成年海龜是一系列 不可能事件的化身。牠是個例外,不是常態 就像頭獎一樣,牠真的是一個奇蹟