Peering into the eyes of different animals, you'll see some extraordinarily shaped pupils.

凝視不同動物的眼睛，你會發現一些形狀奇特的瞳孔。

But why?

但這是為什麼呢？

It turns out that pupil shape is a powerful indicator of what role an animal plays in its ecosystem.

原來，瞳孔的形狀可以有力地說明動物在其生態系統中扮演的角色。

Pupils mark the hollow opening in the iris, the eye's band of pigmented muscle.

瞳孔標記了虹膜中的空心開口，而虹膜是眼睛的色素沉著肌肉帶。

They're the portholes through which light enters the eye, where it then strikes the retina and activates light-sensitive cells, setting the process of vision in motion.

它們是讓光線進入眼睛的舷窗，而光線在撞擊視網膜後觸發了光敏細胞，使視覺活動起來。

Pupils are black because most of the light that enters them is absorbed.

瞳孔之所以是黑色的，是因為進入瞳孔的光線大部分都被吸收了。

Their size changes in response to brightness, as well as certain drugs and emotional and mental states—but their basic form varies greatly among species.

它們的大小會隨著亮度以及某些藥物、情緒和精神狀態的改變而變化—但它們的基本形態在物種之間差別甚大。

House cats, for one, are twilight hunters with vertically elongated pupils.

舉個例子，家貓是黃昏獵手，瞳孔垂直拉長。

In the dark, these structures expand dramatically, taking in the available light.

在黑暗中，這些結構會急劇擴張，吸收所有可用的光線。

When it's bright, they shrink into slits.

在明亮時，它們則會縮成狹縫。

In fact, cat pupils are so flexible that their maximum area is 135 times greater than their minimum area—whereas our pupils only shrink and expand 15-fold.

事實上，貓的瞳孔非常靈活，它們的瞳孔最大面積是最小面積的 135 倍，而我們的瞳孔只能縮小或擴大 15 倍。

And because of how the slit pupil takes in light, it creates sharp, vertical contours.

而由於瞳孔的狹縫吸收光線的方式，它便有了尖銳的垂直輪廓。

When the cat's brain processes the visuals from each eye, the small but sharp differences between them help the cat judge the precise distance of its target.

當貓的大腦處理兩顆眼睛各自帶來的視覺資訊時，它們之間微小但確切的差異能幫助貓判斷與目標之間的精確距離。

In fact, many other ambush hunters also have vertically elongated pupils—but mainly those whose eyes are located closer to the ground.

事實上，許多其他的伏擊獵者也具備垂直伸長的瞳孔—但主要是眼睛離地面更近的那些。

This may be because these pupils are especially useful in perceiving objects at the relative short distances these animals tend to hunt.

這可能是因為這種瞳孔在這些動物較常進行狩獵的較短的距離上，特別能夠精確感知與物體的距離。

The world looks very different from behind the horizontally elongated pupils of many grazing and browsing animals, like goats.

而從許多放牧和食草動物的橫向拉長瞳孔所看出去的世界，例如像山羊等等，則看起來非常不同。

These pupils, situated on either side of the head, let horizontal bands of light in that give the goat a near-360-degree view and provide it with sharp, horizontal images.

這些位於頭部兩側的瞳孔讓水平的光線直接進入，使山羊具有近 360 度的視野，以及清晰的水平視覺。

This helps goats detect any disruption to the horizon—alerting them to potential predators— while still enabling them to see ahead and detect obstacles as they make their escape.

這能幫助山羊探測到地平線上的任何擾動，提醒它們注意潛在的捕食者，同時還能讓它們在逃跑時看得到前方並探測到障礙物。

In fact, goats always keep their pupils aligned with the horizon, rotating their eyeballs in their sockets as they move their heads up and down.

事實上，山羊在頭部上下移動時，瞳孔仍然永遠與地平線保持一致，並將眼球保持在眼窩裡轉動。

Meanwhile, nocturnal geckos have pupils that shrink into slits studded with pinholes in higher light conditions.

與此同時，夜間活動的壁虎在較高的光照條件下，瞳孔則會收縮成佈滿針孔的狹縫。

Each pinhole projects a separate, sharp image onto the geckos retina.

每個針孔都能將一個單獨的清晰圖像投射到壁虎視網膜上。

Scientists think that comparing these different inputs might help the gecko judge distance without having to move.

科學家們認為，比較這些不同的輸入資訊可能有助於壁虎無需移動就能判斷距離。

And while they might have fooled you, mantises and other insects and crustaceans have "pseudopupils."

雖然它們可能騙倒你了，但螳螂和其他昆蟲以及甲殼類動物都有「偽瞳孔」。

These aren't optical structures; they're optical illusions experienced by the observer.

這些不是光學結構，而是觀察者體驗到的視覺錯覺。

Mantises have compound eyes composed of thousands of light-sensing units.

螳螂的複眼由數千個感光單元組成。

When some are aimed at you, they appear black because they're absorbing most wavelengths of incoming light—but there's no actual opening.

當它們瞄準著你的時候，因為吸收了入射光的大部分波長而看起來是黑色的－但上面其實沒有實際的開口。

So, why do we have round pupils?

那麼，為什麼我們人類的瞳孔是圓的呢？

Elongated pupils help sharpen certain dimensions of an animal's vision.

細長的瞳孔有助於提升動物在某些維度下的視覺。

But scientists think that, for animals like us with circular pupils, this is a lower priority.

但科學家們認為，對於像我們這樣瞳孔呈圓形的動物來說，這樣的需求優先順序較低。

Instead of seeing some elements of a scene in extreme focus, we see a larger picture in relative detail, which enables more general skills of observation.

我們看到的不是極端聚焦的場景中的一些元素，而是一個更廣泛場景中香對細節的事物，並讓我們能更廣泛地進行觀察。

This may be especially helpful for foragers looking for food, hunters eyeballing and chasing their prey, and social animals recognizing other faces.

這可能對尋找食物的覓食者、注視和追逐獵物的捕獵者，以及需要識別其他面孔的社會動物來說特別有幫助。

As we peer at different pupils, patterns emerge.

隨著我們觀察到各種不同的瞳孔，便能找出幾個規律。

And yet there are exceptions.

然而其中仍有例外。

For example, Pallas's cats and mongooses are both small ambush predators, but the Pallas's cat has round pupils and mongooses have goat-like pupils.

例如，帕拉斯貓和貓鼬都是小型伏擊捕食者，但帕拉斯貓有圓形的瞳孔，貓鼬則有山羊般的瞳孔。

And we've only explored a few pupil shapes.

而我們在這裡還只探索了幾種瞳孔形狀而已。

Other animals have crescent- or heart-shaped pupils.

其他動物還有著新月形或心形的瞳孔。

And the cuttlefish has perhaps some of the most bizarre: their pupils are circular in the dark, but W-shaped in the light.

或許墨魚的是最奇特的：它們的瞳孔在黑暗中是圓形的，但在光線下是 W 形的。

So, what's going on here?

那麼，這到底是怎麼回事呢？

Well, wouldn't we all like to know?

我們都想知道答案，不是嗎？

But are some adaptations just cooler than others? Allow us to introduce you to the aphid: a bug that poops candy.

但是不是有些動物的適應就是比較酷一些呢？容我們向你介紹蚜蟲：這是種會排泄出糖果的蟲子。

Or, if you think the variety of pupils in the animal kingdom is impressive, wait until you see the variety of genitalia.

或者，如果你覺得動物王國中千奇百怪的瞳孔形狀已經夠讓人印象深刻了，等你看到各種不同的生殖器再來驚訝也不遲。

Keep exploring with these videos.

繼續觀賞這些影片來探索新知吧。