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  • 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 til 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

  • to 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.

  • One thousand eggs laid.

  • Eight hundred hatch.

  • Four hundred make it to the water.

  • Two hundred progress toward adulthood.

  • Twenty 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 longshot. It is the exception, not the rule.

  • A jackpot. It is, in a very real sense,

  • a miracle.

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B1 TED-Ed sea sea turtle turtle roughly hatch

【TED-Ed】The survival of the sea turtle - Scott Gass

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    VoiceTube posted on 2013/03/21
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