The surprising reasons animals play dead - Tierney Thys

譯者: Lilian Chiu 審譯者: Helen Chang

Imagine you’re being attacked by a ferocious predator.

想像一下，一隻兇猛的 肉食動物正要攻擊你。

With no chance of escape,

沒有逃脫的機會，

you do what any courageous, self-respecting possum would do:

你會和任何勇敢、自重的 負鼠做出一樣的反應：

curl into an immobile state called catatonia,

蜷縮起來，進入動也不動的 「緊張症」狀態，

stick out your tongue,

把你的舌頭伸出來，

drool,

流口水，

and ooze some foul-smelling liquid from your anal glands.

肛門腺分泌出一些帶著惡臭的液體。

Disgusted, your assailant loosens its grip,

攻擊者感到噁心，因而放開了你，

decides you’re not the dinner it was looking for,

認定你不是牠在尋找的晚餐，

and departs.

便離開了。

After 10 minutes, you resurrect and merrily saunter on.

10 分鐘後，你復活了， 開心且從容地離去。

From lemurs to lizards,

從狐猴到蜥蜴，

ants to amphibians,

從螞蟻到兩棲動物，

sharks to chickens,

從鯊魚到雞，

hundreds of animals "play dead" as a survival tactic.

數以百計的動物都會用 「裝死」這種生存戰略。

Nicknamed "playing possum" after its star performer,

裝死的暱稱叫做「扮演負鼠」， 因為負鼠是最會裝死的明星演員，

feigning death is also called thanatosis.

也被稱為「假死狀態」。

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

假死狀態這個詞源自 古希臘的死神桑納托斯。

But most scientists call it tonic immobility, or TI.

但大部分科學家稱之為 「僵直靜止狀態」，簡稱 TI。

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

TI 如何／為何發生， 會依物種及情況而異。

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

發出惡臭和採用怪異姿勢是 常見的方式，經常扮演重要角色。

Other animals sacrifice their neighbors:

其他動物則會犧牲周圍的夥伴：

quail chicks that freeze while their kin run amok

當貓追來時，若其他 同類都在瘋狂逃竄，

have a better chance of survival when pursued by a cat.

定住不動的小鵪鶉反而 比較有機會活下來。

Speaking of cats, feline mothers can pinch the napes of their kittens’ necks

說到貓，貓科母親 能叼起小貓的頸背，

and induce another kind of immobility called clipnosis.

造成另一種不動的狀態， 叫做「夾式催眠」。

This keeps their kittens quiet and easy to transport.

這麼做能讓小貓保持安靜， 且很容易帶著走。

Most of the physiological mechanisms underlying these theatrics

在這些戲劇性演出背後的 大部分生理機制，

originate in the parasympathetic nervous system,

來自副交感神經系統，

better known for controlling cycles of resting and digesting.

這系統較為人所知的功能 是控制休息循環和消化。

In possums,

在負鼠體內，

the parasympathetic nervous system causes their heart rates to drop by nearly half,

副交感神經系統會造成牠們的 心跳率下降到幾乎只有一半，

respiration by a third,

呼吸減少三分之一，

and body temperatures by more than half a degree Celsius for up to an hour.

體溫下降超過攝氏半度， 可持續一小時之久。

The neurotransmitter dopamine also plays a part.

神經遞質多巴胺也有所貢獻。

Flour beetles with low dopamine levels play dead more frequently

低多巴胺的擬穀盜（一種甲蟲）

比高多巴胺的擬穀盜更常裝死，

than those with high levels,

and anything blocking dopamine receptor sites can lengthen catatonia.

只要阻擋多巴胺接收器， 就能延長「緊張症」。

But maintaining a death ruse isn’t easy.

但要維持死亡詐術並不容易。

The performers are constantly gauging their surroundings

表演者要經常評估牠們的環境，

for cues on when it’s safe to rise.

尋找線索，知道何時起身是安全的。

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

以雞為例，牠們能感受到 獵食者的目光是否在牠們身上。

Researchers know this because when they used a stuffed hawk in an experiment,

研究者知道這點，是因為他們 在實驗中使用絨毛玩具鷹，

their chicken subjects came out of their catatonia quicker

當絨毛玩具鷹移開視線時，

when the hawk’s eyes were averted.

身為目標的雞從「緊張症」狀態 恢復的速度比較快。

Other animals use TI for purposes other than defense.

其他動物把 TI 用在防禦以外的用途。

When the sleeper cichlid feels peckish,

當雨麗魚感到有點餓時，

it sinks to the lake floor and lies motionless,

牠會沉到湖底，躺著一動也不動，

its splotchy coloration making it seem like a rotting carcass.

因為外表天然色看起來髒髒的， 牠看起來就像腐屍一樣。

If a small scavenger investigates, this undead trickster strikes.

如果有小型腐食動物來查看， 這隻沒死的騙子就會立馬攻擊。

Some animals even feign death as a sexual ploy.

有些動物甚至會為了性活動裝死。

Male nursery spiders offer gifts of silk-wrapped insects

雄盜蛛會用蜘蛛絲包裹昆蟲當禮物，

in hopes of wooing females.

希望能追到雌盜蛛。

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

但眾所皆知，雌盜蛛會 吃掉前來求愛的雄盜蛛。

By playing dead while the female eagerly devours her snack,

當雌盜蛛在狼吞虎嚥吃點心時， 雄盜蛛會先裝死，

these males can cautiously revive

然後小心地復甦過來，

and improve their chances of successfully mating.

就會更有機會能成功交配。

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

TI 對於動物來說是個優勢， 除非別人知道這個秘密。

California orcas can flip over young great white sharks,

加州虎鲸會把年幼的大白鯊翻過來，

inducing TI for so long the immobilized sharks,

造成 TI，時間長到 讓無法動彈的鯊魚

who must move to respire, essentially suffocate.

因無法移動而無法呼吸，最終窒息。

Humans can also flip sharks into TI.

人類也可以把鯊魚翻到 TI。

By stroking a shark’s electrically-sensitive snout

撫摸鯊魚對電很敏感的鼻部，

and gently turning it over,

輕柔地將牠翻過來，

researchers can induce TI that lasts up to 15 minutes.

研究者可以造成 長達 15 分鐘的 TI。

That’s enough time to insert tags,

這時間足以插入標籤，

remove hooks,

移除鉤子，

and even perform surgeries.

甚至可以進行手術。

There are risks however:

然而，還是有風險：

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

TI 可能會阻礙呼吸， 造成血糖過高，這是壓力的徵兆。

So this technique should only be used when necessary.

所以只有在必要時才會用這種方式。

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

人類也會發生 TI，在暴力攻擊的 過程中會因為恐懼而靜止不動。

Recognizing this ancient, involuntary form of self-defense

認清這項古老、非自願性的 自我防禦形式，

has significant implications when trying to understand

有很重大的意義，能夠協助了解

why some victims don’t flee or fight in the face of danger.

為什麼在面臨危險時， 有些受害者不會逃跑或抵抗。

So, studying TI in non-human animals

針對非人類的動物來研究 TI，

not only helps us better understand some odd behaviors,

不只能協助我們 更了解一些奇怪的行為，

it can also help us better understand our own,

也能協助我們更了解我們自己

sometimes counterintuitive,

在面對暴力時，何以有時會 做出違背直覺的反應。

responses to violence.