The lovable (and lethal) sea lion - Claire Simeone

譯者: Ann Chen 審譯者: Carol Wang

Sunning themselves on rocks or waddling awkwardly across the beach,

看到牠們在石頭上曬太陽 或笨手笨腳搖晃地走過沙灘，

it’s easy to think of these immobile mammals less as sea lions,

我們很容易把這些不太動的 哺乳動物視為海家貓，

and more as sea house cats.

而不是海獅。

But don’t be fooled by their beachside behavior.

但不要被牠們在海灘上的舉止欺騙。

Under the waves, sea lions are incredible endurance hunters.

在海裡，海獅是有驚人耐力的捕獵者。

Hurtling around at speeds from 4 to 18 miles an hour

以每小時 4 到 18 英里的速度衝馳，

and hunting for up to 30 hours at a time,

每次獵捕可長達 30 小時，

these majestic mammals live up to their name.

這魁梧的哺乳動物真不負其名。

And thanks to a suite of physical adaptations,

由於身體經過一系列的演化，

finely tuned over millions of years, they make for resourceful foragers.

歷經數百萬年不斷微調， 牠們變成很機智的覓食者。

To find their favorite food,

為了尋找喜歡的食物，

sea lions hunt much deeper than many of their semi-aquatic peers.

海獅會潛入 比半水生同類動物更深處捕食。

With some species diving to depths of nearly 400 meters,

有些種類會潛入約 400 米深，

they’re able to cope with the mounting pressure

牠們能對抗漸增的水壓──

by collapsing their pliable rib cage, and compressing a pair of springy lungs.

藉由塌扁柔軟的胸腔 和壓縮兩個富彈性的肺。

This pushes air up through the smaller airways,

空氣會被推過較小呼吸道，

collapsing rings of cartilage as oxygen travels out from the lungs,

當氧氣離開肺時，導致軟骨環塌扁，

to be held in the larger, upper airways.

如此空氣會停留在較大的上呼吸道。

Upon surfacing, this air will be used to re-inflate the lungs,

浮到水面時， 這空氣會使肺重新膨脹，

but for now their heart slows down to preserve oxygen.

但在水裡時， 心跳會減慢以保留氧氣。

Blood flow is redirected towards only the most essential organs

血流只會流向最重要的器官，

like the heart, lungs, and brain,

如心臟、肺及腦，

which rely on reserve oxygen stored in blood and muscle.

這些器官仰賴 貯存於血和肌肉的氧氣。

Once they arrive at their hunting ground,

抵達獵場時，

sea lions depend on their superior vision to find their prey.

海獅靠牠們的超級視力尋獲獵物。

Most mammal eyes have a structure called a lens–

大部份哺乳動物眼睛有個構造 稱為「水晶體」，

a transparent, convex structure whose shape refracts light to enable sight.

一種透明的凸形構造， 可折射光線成為可見影像。

In humans, this lens is curved to process light waves traveling through air.

人類水晶體是弧形結構， 以處理通過空氣的光波。

But sea lions need to see their best at hundreds of meters deep.

但海獅需在數百米深處仍能看清楚，

To accommodate, their eyes have a much rounder lens to refract light underwater,

為了適應，牠們有 更圓的水晶體以反射水中的光，

as well as teardrop-shaped pupils

並且其淚滴狀的瞳孔

which can expand to 25 times their original size.

可放大到原來的 25 倍。

This lets in as much light as possible,

這能儘可能讓光進入，

helping them pinpoint their prey in even the dimmest conditions.

使牠們在極暗處 也可精確看清獵物所在。

But once they’ve closed in,

但當靠近獵物時，

they rely on something akin to a sixth sense to actually catch their meal.

牠們依賴一種 類似第六感的感覺以捕獲食物。

Their whiskers, or vibrissae,

牠們的觸鬚──也稱為感覺毛，

are composed of keratin and full of nerve fibers

是由角蛋白所組成，

並佈滿連到臉部 結締組織深處的神經纖維。

that run deep into the connective tissue of their face.

Sea lions have full directional control over these whiskers,

海獅能隨意控制這些觸鬚，

which can lie flat against their face, or stick out at a 90-degree angle.

讓它們可以完全貼臉， 或以 90 度角伸出去。

When properly tuned,

經由適當的調整，

these whiskers can sense the slim trails of moving water fish leave in their wake.

觸鬚能覺察到魚游過後的細長水跡。

And they’re precise enough to let blindfolded sea lions

它們準確力高到 即使矇住眼睛的海獅

tell the difference between objects less than two centimeters different in size.

也能分辨物體之間 小於兩公分的差異。

With these tools a healthy sea lion can catch generous helpings of fish

用這些能力，健康的海獅 每次狩獵都可捕獲大量的魚，

such as anchovy, mackerel, and squid on every outing.

例如鯷魚、鯖魚及魷魚。

And with their exceptional memories, they can remember multiple hunting grounds,

憑著極佳的記憶力， 牠們能記住許多獵場，

including those they haven’t visited in decades.

包括數十年未再造訪的場所。

This memory also extends to breeding territories and birthing areas,

這記憶力還涵蓋到繁殖地及生產地，

as well as which neighbors are friend and foe.

以及哪些鄰居是敵或友。

There’s even evidence that sea lions can remember how to perform tasks

還有証據顯示 海獅能記得如何執行技能，

after 10 years with no practice in between,

僅管十多年都沒再練習。

letting them navigate old stomping grounds with ease.

這讓牠們在舊時的出沒場所 可輕鬆遨遊。

Yet despite these incredible adaptations,

雖有這些驚人的演化，

there are changes unfolding in their habitats

但海獅棲息地的一些改變 發生得太快，

too rapidly for sea lions to handle.

使牠們來不及適應。

As climate change warms the oceans, certain toxic algae species thrive.

隨著氣候改變暖化了海洋， 有些毒海藻繁殖茂盛。

This algae is harmless to the fish who eat it,

這些海藻對吃它們的魚無害，

but for the sea lions which ingest those fish,

但對於吃這些魚的海獅，

the algae’s domoic acid can trigger seizures and brain damage.

海藻的軟骨藻酸 能誘發痙攣及腦損傷。

Changing ocean conditions keep this algae blooming year round,

海洋環境的改變 使得海藻整年不斷地繁盛，

causing more and more sea lions to wash up on beaches.

這使得愈來愈多的海獅屍體 被沖到海灘上。

This tragic discovery is just one of the many ways

這悲慘的發現僅是其中一個

the health of aquatic animal communities can help us

水生生物群的健康

better understand Earth’s oceans.

能協助我們 更理解地球的海洋的方式。

These red flags help us take action

這些危險訊號促使我們採取行動

to protect ourselves and other maritime mammals.

保護自己及其他海洋哺乳動物。

And the more we can learn about the changing ocean that sea lions inhabit,

對海獅居住的海洋環境變化了解愈多，

the better equipped we’ll be to help these clever creatures thrive.

我們愈能有充份準備， 幫助這些聰明的生物繁衍。