Name: 【TED-Ed】為什麼動物要裝死？ (The surprising reasons animals play dead - Tierney Thys)
Uploaded: 2023-07-01T21:01:30.000Z
Duration: 4 min 47 s

Imagine you're being attacked by a ferocious predator.

想像你正被某個兇猛的掠食者攻擊

With no chance of escape, you do what any courageous, self-respecting possum would do:

curl into an immobile state called catatonia, stick out your tongue, drool, and ooze some foul-smelling liquid from your anal glands.

你做了任何一隻勇敢、有自尊的負鼠都會做的事 :

Disgusted, your assailant loosens its grip, decides you're not the dinner it was looking for, and departs.

把自己捲成一團僵硬不動，稱作緊張症的狀態，

After 10 minutes, you resurrect and merrily saunter on.

From lemurs to lizards, ants to amphibians, sharks to chickens, hundreds of animals "play dead" as a survival tactic.

Nicknamed "playing possum"  after its star performer, feigning death is also called thanatosis.

That's from Thanatos, the ancient Greek deity of death.

攻擊者因為覺得噁心而放鬆了鉗制

But most scientists call it tonic immobility, or TI.

How and why TI occurs depends on the species and situation.

Spewing stench and adopting odd postures are common and often play important roles.

10 分鐘過後，你原地復活並興高采烈地繼續遊蕩

Other animals sacrifice their neighbors: quail chicks that freeze while their kin run amok have a better chance of survival  when pursued by a cat.

Speaking of cats, feline mothers can pinch the napes of their kittens' necks and induce another kind of immobility called clipnosis.

This keeps their kittens quiet and easy to transport.

Most of the physiological mechanisms underlying these theatrics originate in the parasympathetic nervous system, better known for controlling cycles of resting and digesting.

數以百計的動物們把「裝死」視為一種求生戰術

In possums, the parasympathetic nervous system causes their heart rates to drop by nearly half, respiration by a third, and body temperatures by more than half a degree Celsius for up to an hour.

以其備受矚目的「假扮負鼠」謔稱之

The neurotransmitter dopamine also plays a part.

Flour beetles with low dopamine levels, play dead more frequently than those with high levels.

這個字源於 Thanatos，古代希臘神祉中的死亡之神

And anything blocking dopamine receptor sites can lengthen catatonia.

但大部分的科學家稱它為緊張性麻痺，或是縮寫為 TI

TI 發生的狀態和原因取決於物種和當時的狀況

The performers are constantly gauging their surroundings for queues on when it's safe to rise.

吐出惡臭跟採取奇特的姿勢都是常見的手段，也經常扮演重要的作用

Chickens, for instance, can sense when a predator's eyes are upon them.

其他物種則把他們的鄰居當作犧牲品 :

Researchers know this, because when they used a stuffed hawk in an experiment, their chicken subjects came out of their catatonia quicker when the hawk's eyes were averted.

在同類四處竄逃時靜止不動的鵪鶉幼雛，

Other animals use TI for purposes other than defense.

在被貓追捕的狀況下生存率較高

When the sleeper cichlid feels peckish, it sinks to the lake floor and lies motionless.

說到貓，身為母親的貓科動物會叼住幼崽的後頸上方，

Its splotchy coloration making it seem like a rotting carcass.

藉以製造稱作 clipnosis 的另一種型態的靜止不動

If a small scavenger investigates, this undead trickster strikes.

這能讓牠們的幼崽保持安靜並易於移動

Some animals even feign death as a sexual ploy.

這些戲劇性效果背後大部分的生理機制

Male nursery spiders offer gifts of silk-wrapped insects in hopes of wooing females.

But those females are known to eat love-seeking males.

以控制休息和消化的周期而聞名

By playing dead while the female eagerly devours her snack, these males can cautiously revive and improve their chances of successfully mating.

So TI can work to an animal's advantage, unless someone else knows its secret.

副交感神經系統使他們的心跳率下降將近一半、

California orcas can flip over young great white sharks, inducing TI for so long the immobilized sharks — who must move to respire — essentially suffocate.

身溫降低超過 0.5 度長達一個小時

By stroking a shark's electrically-sensitive snout and gently turning it over, researchers can induce TI that lasts up to 15 minutes.

神經傳遞物質多巴胺也發揮了作用

That's enough time to insert tags, remove hooks, and even perform surgeries.

體內多巴胺含量低的扁擬穀盜甲蟲會比那些含量高的甲蟲

TI can hamper respiration and induce hyperglycemia, a sign of stress.

任何阻斷多巴胺受點的物質都可以延長緊張症的時間

So this technique should only be used when necessary.

Humans can also experience TI when they freeze with fear during violent assaults.

裝死者不斷地衡量他們周圍的環境，

Recognizing this ancient, involuntary form of self-defense has significant implications when trying to understand why some victims don't flee  or fight in the face of danger.

So, studying TI in non-human animals not only helps us better understand some odd behaviors, it can also help us better understand our own, sometimes counterintuitive, responses to violence.

以雞隻為例，牠們可以感知掠食者的視線何時落在牠們身上

Love animals? Check out this playlist for more videos on some of our favorite furry and not-so-furry friends.

研究人員之所以得知這點，是因為當他們在實驗中使用老鷹絨毛娃娃時，

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【TED-Ed】為什麼動物要裝死？ (The surprising reasons animals play dead - Tierney Thys)

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