spadefoot toad tadpoles hatch in tiny oases.

鋤足蟾蝌蚪正在小型綠洲中孵化

Until they develop into toadlets, they can't survive outside of water,

在成為蟾蜍前，他們都必須生活在水裡

but these ponds are transient and quickly evaporate.

但這些池塘只是暫時的，很快就會蒸發消失

The tadpoles are in a race against the clock

這些蝌蚪正在和時間賽跑

to grow up before their nurseries disappear.

必須在他們的安身之地消失前趕緊長大

So nearly overnight, some of the brood explode in size.

幾乎是一夜之間，其中幾群蝌蚪會突然茁壯許多

They use their jack-o-lantern teeth and huge jaw muscles

他們靠著尖銳的牙齒和發達的下巴肌肉

to devour their smaller pond mates.

將池塘中比較瘦弱的同伴吞噬掉

Nourished by this extra fuel,

因著這些額外的滋養

they develop quicker, leaving the pond before it can dry out.

他們發育得比較快，因而能夠趕在池塘乾涸前離去

The spadefoot toad is far from the only animal

鋤足蟾絕非唯一一種

to eat members of its own species as a normal part of its life cycle.

會把同類互食視為成長必經過程的動物

All of these animals do.

所有這些動物都會如此

If that surprises you, you're in good company.

如果你很驚訝的話，你絕不是孤身一人

Until recently, scientists thought cannibalism

直到最近，科學家都認為同類相食

was a rare response to starvation or other extreme stress.

只是一種對於飢餓或是其他高壓才會有的罕見反應

Well-known cannibals,

幾種有名的同類殘殺者

like the praying mantis and black widow spider,

比如螳螂或是黑寡婦蜘蛛

were considered bizarre exceptions.

都只是被視為特殊例外

But now, we know they more or less represent the rule.

但是現在，我們得知這兩種動物的行為多少代表了一種法則

While it may seem counterproductive for members of the same species to eat each other,

雖然對於同種族的成員來說，同類相食看似毫無用意

cannibalism can promote the survival of the species as a whole

但那其實可以促進整個種族的存活

by reducing competition,

畢竟競爭減少了

culling the weak,

弱者也被篩選了出來

and bolstering the strong.

強者則得到助益

Some species, like the spadefoot toad,

有些物種，譬如鋤足蟾

cannibalize in response to environmental pressures.

是因為環境壓力促使他們出此手段

Their situation is precarious,

他們的情況很危急

but cannibalism for them isn't a last-ditch attempt to avoid starvation.

但是同類互食並不是他們避免飢餓的最終手段

Rather, it's a way to more quickly outgrow a stage where they're especially vulnerable to predation

相反的，那是為了盡快發育，好趕緊脫離那段淪為獵物的脆弱時期

or dangerous environmental conditions.

或是身處的危險環境

Other species, including many fish,

其他物種，包含許多魚類

indiscriminately cannibalize each other during foraging behavior.

在覓食時也會無差別地吃掉同類

Fish produce large numbers of tiny young,

魚一次會產下大量的後代

and adults exhibit about as much individual recognition of their offspring

成年的魚對於這些後代的個體認同程度

as humans do for a handful of raisins.

大概就像人類看待一大把的葡萄乾

Fish eggs, larvae, and juveniles are easily available, nutrient-rich meals,

魚卵、魚仔和幼魚是容易取得且豐富營養的餐點

and with thousands of eggs in a clutch,

而且由於一小窩就會含有上千顆卵

plenty are still available to hatch after the adults have snacked.

在被成年魚類吃完前尚還有許多來得及孵出來

Baby fish aren't just at risk of being cannibalized by adults—

幼魚並不單單冒著會被成年魚吃掉的風險

siblings eat each other, too.

下毒手的也可能是自己的手足

Sand tiger shark eggs develop and hatch inside their mother's oviducts at different times.

沙虎鯊的卵在母體輸卵管中，分別發育孵化的階段皆不相同

When the hatchlings run out of yolk from their own eggs,

當幼體將自己的蛋黃消耗完時

they eat the other eggs and hatchlings

他們會吃其他的卵和幼體

until one baby shark from each oviduct remains.

直到最終輸卵管分別只剩一隻鯊魚寶寶

When they emerge, the young sharks are well-nourished, experienced predators

待他們出生時，年幼的鯊魚吃飽喝足，而且已經是有經驗的狩獵者

who stand a better chance of surviving.

因此有較高的幾率生存

Even when they aren't consumed for nutrition,

即使不是因為營養攝取而被吃掉

young animals are especially vulnerable to cannibalism.

年幼的動物仍然特別容易淪為同類的食物

Hamsters,

倉鼠

rats,

老鼠

and other rodent mothers

和其他嚙齒類動物媽媽

will eat some of their young if they're sick,

會因為小孩生病而把他們吃了

dead,

或因為小孩死了

or simply too numerous to feed.

或者純粹因為太多了養不起

In other mammals, including bears and lions,

其他哺乳類動物，比如熊和獅子

males will kill offspring sired by another.

他們的雄性會殺害其他同類的後代

That's because childless females become receptive to mating more quickly than if they were caring for a cub.

那是因為相對於要照顧幼獸的雌性，沒有小孩的雌性會較快願意再次交配

Rather than waste nutritious meat, the males then eat the dead cubs.

雄性動物也不會浪費富含營養的肉，他們會把死去的幼獸吃掉

Meanwhile, cannibalism is less common in birds than in other groups,

不過在鳥類圈，同類相食的情況比較少見

but certain species will eat diseased or dead hatchlings

但其中一些特定物種也會將生病或是死去的雛鳥吃掉

as a way of disposing of the bodies before they can attract maggots.

這樣才能在生蛆前把屍體處理掉

When adults eat each other, males are cannibalized more often than females,

當說到成年互食時，比較多情況是雄性的被雌性吃

usually during mating and generally because they're smaller.

而且通常發生在交配期間，原因一般是因為雄性身型比較小

Male Australian redback spiders mate with much larger females.

雄性的澳洲紅背蜘蛛和比他們龐大許多的雌性交配

Rather than scrambling away after mating, the tiny male does a somersault,

交配完成後，嬌小的公蜘蛛不會趕緊爬走，而是翻個筋斗

bringing his abdomen into contact with his mate's mouthparts.

將他的腹部靠到他伴侶的口器旁

The female showers him with enzyme-rich gut juice and consumes his abdomen.

雌性會向他噴射富含消化酶的內臟汁液，消化他的腹部

Males not killed in the initial mating crawl back into the fray,

經過第一次交配沒有死透的公蜘蛛會爬回原位

often half-eaten,

通常都是拖著被吃了一半的身軀

to mate again, after which they're dispatched to the spider pantry.

好再戰一場，結束後他們會被收藏到母蜘蛛的食物櫃裡

So not only does the male provide the female with his sperm,

所以雄性不只提供了他們的精子給雌性

but he also provides her with a nutritious meal

還供應了豐盛的一餐

to better ensure that she'll survive to pass on his genes.

如此可以確保雌性能夠活下去，繁衍他的基因

All in all, it's clear that cannibalism is

整體來說，同類相食很明顯是

as much a part of life in the animal kingdom

動物界生命循環再正常不過的一環

as other, better-recognized behaviors.

就和其他行為一樣正常

As we sink our teeth into the evidence of cannibalism in nature,

當我們深入了解自然界同類相食的現象時

we might ask ourselves,

我們或許會如此自問

what else have we missed by applying human standards to the natural world?

當把人類標準套用到自然界時，我們是否還忽略了什麼？