The three different ways mammals give birth - Kate Slabosky

譯者: Josephine Chen 審譯者: Helen Chang

What do these animals have in common?

這些動物的共通處是甚麼?

More than you might think.

比你想的還要多

Along with over 5,000 other species, they're mammals,

除了有五千多種種類外 牠們是哺乳類動物

or members of class mammalia.

或是隸屬哺乳綱目

All mammals are vertebrates, meaning they have backbones.

所有的哺乳動物都是脊椎動物 這代表牠們都有脊骨

But mammals are distinguished from other vertebrates

但哺乳動物跟其他脊椎動物的區分法

by a number of shared features.

來自若干個相同特徵

That includes warm blood,

包括溫血

body hair or fur,

毛髮或毛皮

the ability to breathe using lungs,

使用肺呼吸的能力

and nourishing their young with milk.

以母乳哺育稚子

But despite these similarities,

儘管有這些相似處

these creatures also have many biological differences,

這些生物仍存在著許多生物差異

and one of the most remarkable is how they give birth.

其中一項令人驚異的差異在生產方式

Let's start with the most familiar, placental mammals.

讓我們從大家最熟悉的 胎盤哺乳類（真獸類）動物談起

This group includes humans,

這類組包括：人類

cats,

dogs,

貓、狗、長頸鹿

giraffes,

and even the blue whale, the biggest animal on Earth.

甚至藍鯨——世界上最大的哺乳類動物

Its placenta, a solid disk of blood-rich tissue,

哺乳動物的胎盤—— 紮實的碟狀充血組織

attaches to the wall of the uterus to support the developing embryo.

附著在子宮壁上 提供發育中的胚胎養分

The placenta is what keeps the calf alive during pregnancy.

藍鯨寶寶在孕期靠胎盤維生

Directly connected to the mother's blood supply,

從母體血液直接獲得養分

it funnels nutrients and oxygen straight into the calf's body

運輸養分與氧氣直達藍鯨寶寶體內

via the umbilical cord,

臍帶就是運輸通道

and also exports its waste.

臍帶也排出代謝廢物

Placental mammals can spend far longer inside the womb than other mammals.

胎盤哺乳類比其他哺乳類在子宮內待得更久

Baby blue whales, for instance, spend almost a full year inside their mother.

以藍鯨寶寶為例 在媽媽體內幾乎待滿一年

The placenta keeps the calf alive right up until its birth,

出生前胎盤持續維持胎兒的生命

when the umbilical cord breaks

當臍帶斷落

and the newborn's own respiratory,

新生兒的呼吸系統

circulatory,

循環系統

and waste disposal systems take over.

和代謝系統會取代臍帶

Measuring about 23 feet, a newborn calf is already able to swim.

大約23英尺長 新生藍鯨寶寶已經會游泳了

It will spend the next six months

藍鯨寶寶接下來大約六個月

drinking 225 liters of its mothers thick, fatty milk per day.

每天會喝下225公升、醇濃全脂的母乳

Meanwhile, in Australia, you can find a second type of mammal -

同時在澳洲，你會發現第二種哺乳動物

marsupials.

有袋類哺乳動物

Marsupial babies are so tiny and delicate when they're born

有袋類寶寶剛出生時小巧嬌弱

that they must continue developing in the mother's pouch.

必須繼續在媽媽的育兒袋內茁壯

Take the quoll, one of the world's smallest marsupials,

舉例來說：袋鼬—— 世界上最小的有袋類動物之一

which weighs only 18 milligrams at birth,

出生時只有18毫克重

the equivalent of about 30 sugar grains.

相當於30顆糖粒的重量

The kangaroo, another marsupial,

另一種有袋動物—袋鼠

gives birth to a single jelly bean-sized baby at a time.

一次只產下一隻 果凍豆糖大小的袋鼠寶寶

The baby crawls down the middle of the mother's three vaginas,

袋鼠寶寶爬到媽媽三個陰道中間

then must climb up to the pouch,

然後必須爬到育兒袋

where she spends the next 6-11 months suckling.

在接下來的六到十一個月 在育兒袋裡吸奶

Even after the baby kangaroo leaves this warm haven,

儘管袋鼠寶寶離開這個溫暖的天堂

she'll return to suckle milk.

仍然會回到育兒袋吸奶

Sometimes, she's just one of three babies her mother is caring for.

有時牠只是袋鼠媽媽照顧的 三寶中的其中一寶

A female kangaroo can often simultaneously support one inside her uterus

母袋鼠通常能同時一邊提供養分 給子宮裡的寶寶

and another in her pouch.

一邊在育兒袋中哺乳另一寶寶

In unfavorable conditions,

在不佳的環境下

female kangaroos can pause their pregnancies.

母袋鼠會滯育

When that happens, she's able to produce two different kinds of milk,

子宮休眠下，牠能夠產出兩種母乳

one for her newborn,

一種供給新生的二寶

and one for her older joey.

另一種供給大寶

The word mammalia means of the breast,

mammalia 這個字的意思 是「來自乳房」

which is a bit of a misnomer

似乎有點用詞不當

because while kangaroos do produce milk from nipples in their pouches,

袋鼠媽媽的確 自育兒袋裡的奶頭產出母奶

they don't actually have breasts.

但牠們並沒有乳房

Nor do monotremes, the third and arguably strangest example of mammalian birth.

單孔目哺乳動物也沒有乳房

第三種，也可能是 最怪異的哺乳動物例子

There were once hundreds of monotreme species,

世界上曾經有數百種單孔目動物

but there are only five left:

現今只剩下五種

four species of echidnas and the duck-billed platypus.

針鼴科四種與鴨嘴獸一種

“monotreme”這個字的意思是「單孔」

The name monotreme means one hole

referring to the single orifice they use for reproduction,

意指單孔目哺乳動物 以同一泄殖腔繁衍

excretion,

排泄

and egg-laying.

以及產卵

類似鳥類、爬蟲類、魚類

Like birds,

reptiles,

fish,

dinosaurs,

恐龍和其他生物

and others,

these species lay eggs instead of giving birth to live young.

這些物種不是產下胎兒而是產卵

Their eggs are soft-shelled,

牠們的殼質地薄軟

and when their babies hatch, they suckle milk from pores on their mother's body

孵化後，寶寶們 會從媽媽身上的毛孔吸允母乳

到牠們會自己覓食為止

until they're large enough to feed themselves.

Despite laying eggs and other adaptations that we associate more with non-mammals,

儘管我們把產卵和其他的演化調適 連結到非哺乳類較多

like the duck-bill platypus's webbed feet,

就像鴨嘴獸的蹼

bill,

喙 雄鴨嘴獸腳上的毒刺

and the venomous spur males have on their feet,

事實上，牠們是哺乳動物

they are, in fact, mammals.

That's because they share the defining characteristics of mammalia

因為牠們與哺乳動物有一樣的界定特徵

and are evolutionarily linked to the rest of the class.

也與其他的哺乳綱動物有演化關聯

Whether placental,

不論是胎盤哺乳類

marsupial,

有袋哺乳類或單孔目類

or monotreme,

each of these creatures and its unique birthing methods, however bizarre,

這些生物擁有獨特的哺育方式

不管多麼地奇特

have succeeded for many millennia in bringing new life and diversity

數千年來已成功地賦予新生命 和生物多樣性

到這個哺乳動物王國

into the mammal kingdom.