The last living members of an extinct species - Jan Stejskal

翻译人员: Nicole Tsang 校对人员: Yolanda Zhang

In the savannahs of Kenya, two female northern white rhinos, Nájin and Fatu,

在肯尼亚的大草原上， 两头雌性北部白犀牛，纳金和法图，

munch contentedly on the grass.

正在草地上大快朵颐。

At the time of this video’s publication,

在这段视频发布的时候，

these are the last two known northern white rhinos left on Earth.

它们是已知地球上仅存的 最后两头北部白犀牛。

Their species is functionally extinct—

这一物种在功能上已经灭绝了，

without a male, Nájin and Fatu can’t reproduce.

没有雄性个体的存在， 纳金和法图根本无法繁衍。

And yet, there’s still hope to revive the northern white rhino.

但是，复兴北部白犀牛 这一物种的希望还存在。

How can that be?

要如何做到呢？

The story starts about 50 years ago,

这个故事始于大约 50 年前，

when poachers began illegally hunting thousands of rhinos

当时的偷猎者在非洲各地

across Africa for their horns.

开始非法狩猎， 捕获了数以千计的犀牛。

This, combined with civil wars in their territory,

再加上它们的领土上发生了内战，

decimated northern white rhino populations.

导致北部白犀牛的数量锐减。

Concerned conservationists began trying to breed them in captivity in the 1970s,

20 世纪 70 年代，环保人士 开始尝试人工饲养这些犀牛，

collecting and storing semen from males.

并收集和储存雄性犀牛的精液。

Only four rhinos were ultimately born through the ambitious breeding program.

尽管存在这项雄心勃勃的繁衍计划， 最终也只诞生了四头犀牛。

Nájin, and her daughter Fatu were the last two.

纳金和女儿法图 是最后两头。

In 2014, conservationists discovered that neither can have a calf.

2014 年，环保主义者发现， 这两头犀牛都无法生育下一代。

Though Nájin gave birth to Fatu, she now has weak hindlegs,

虽然纳金生了法图， 但现在它的后腿很脆弱，

which could harm her health if she became pregnant again.

如果她再次怀孕， 可能会危害她的健康。

Fatu, meanwhile, has a degenerated uterine lining.

同时，法图则出现了子宫内膜退化。

Then, the last northern white rhino male of the species, Sudan, died in 2018.

随后，最后一头雄性北方白犀牛， 苏丹，也于 2018 年死亡。

But there was one glimmer of hope: artificial reproduction.

但是还有一线希望： 人工繁殖。

With no living males and no females able to carry a pregnancy,

没有存世的雄性白犀牛， 也没有能够怀孕的雌性白犀牛，

this is a complicated and risky process to say the least.

这至少也是一个复杂而冒险的过程。

Though scientists had stored semen, they would have to collect the eggs—

尽管科学家们储存了精液， 还不得不收集卵子——

a complex procedure that requires a female to be sedated for up to two hours.

这一复杂的过程需要给雌性白犀牛 注射效力长达两小时的镇静剂。

Then, they’d create a viable embryo in the lab—

然后，他们还需要在实验室里 创造出具备可存活的胚胎。

something that had never been done before, and no one knew how to do.

这是一次前无古人的尝试， 没人知道怎样才能成功。

Even that was just the beginning—

就连这一步也仅仅是开始——

a surrogate mother of another rhino species

另一个代孕犀牛物种

would have to carry the embryo to term.

还必须孕育胚胎至足月。

Females of a closely related species, the southern white rhino,

南方白犀牛是 北方白犀牛的近亲物种，

became both the key to developing a rhino embryo in a lab

于是雌性白犀牛成为了 实验室犀牛胚胎发育的关键，

and the leading candidates for surrogate mothers.

也是代孕母体的首选对象。

Northern and southern white rhinos diverged about a million of years ago

大约在一百万年前， 南北白犀牛就分化成了

into separate— though still closely-related— species.

彼此独立，但仍具备亲缘关系的物种。

They inhabit different regions, and have slightly different physical traits.

它们栖居在不同的地区， 并拥有略微不同的物理特征。

In a fortunate coincidence, several female southern white rhinos

在一个机缘巧合下， 几头雌性南方白犀牛

needed treatment for their own reproductive problems,

刚好出现了生殖问题， 让研究人员得以收集卵子

and researchers could collect eggs as part of that treatment.

作为治疗的一部分。

In Dvůr Králové Zoo in October 2015,

2015 年 10 月，在德武尔·克拉洛维 （Dvůr Králové Zoo）动物园，

experts of IZW Berlin began collecting eggs from southern white rhinos

来自德国莱布尼兹动物园与野生动物研究所 （IZW Berlin）的专家开始收集南部白犀牛的卵，

and sending them to Avantea, an animal reproduction laboratory in Italy.

并把它们送到了意大利的 阿凡提亚（Avantea）动物繁殖实验室。

There, scientists developed and perfected a technique to create a viable embryo.

在那里，科学家发展和完善了 一项能创造可存活胚胎的技术。

Once they mastered the technique,

在掌握了这项技术之后，

researchers extracted Nájin and Fatu’s eggs on August 22, 2019

在 2019 年 8 月 22 日，研究人员 提取了纳金和法图的卵子，

and flew them to Italy.

并把它们送到了意大利。

Three days later, they fertilized the eggs with sperm

三天后，他们用一头 雄性北方白犀牛的精子

from a northern white rhino male.

使卵子受精。

After another week, two of the eggs made it to the stage of development

又过了一周，两颗卵子 进入了发育阶段，

when the embryo can be frozen and preserved for future.

这时就可以对胚胎 进行冷冻保存以备用。

Another collection in December 2019 produced one more embryo.

在 2019 年 12 月搜集的精子和卵子 又生产了一颗新的胚胎。

As of early 2020, the plan is to collect Nájin and Fatu’s eggs three times a year

到 2020 年初，研究人员计划 在保证纳金和法图身体健康的情况下，

if they’re healthy enough.

每年收集三次它们的卵子。

In the meantime, researchers are looking for

同时，研究人员也在寻找

promising southern white rhino surrogate mothers—

潜在的南部白犀牛代孕母体——

ideally who’ve carried a pregnancy to term before.

最理想的是有过足月生育经历的母体。

The surrogacy plan is somewhat of a leap of faith—

这一代孕计划在某种程度上 是信仰的一次飞跃，

southern and northern white rhinos have interbred

南部和北部白犀牛 都是在上一个冰河时期

both during the last glacial period and more recently in 1977,

和最近的 1977 年才进行杂交的，

so researchers are optimistic a southern white rhino

所以研究人员对南部白犀牛 能够孕育北部白犀牛的胚胎至足月

would be able to carry a northern white rhino to term.

持非常乐观的态度。

Also, the two species’ pregnancies are the same length.

另外，这两个物种的孕期相同。

Still, transferring an embryo to a rhino is tricky

尽管如此，由于子宫颈的形状的差异，

犀牛胚胎跨物种移植 依然是一个非常复杂的过程。

because of the shape of the cervix.

The ultimate goal, which will take decades,

最终目标是在数十年的时间内

is to establish a breeding population of northern white rhinos

将北方白犀牛的繁殖数量

in their original range.

恢复到最初的水平。

Studies suggest that we have samples from enough individuals

研究表明，我们拥有的 个体样本数量足以重现

to recreate a population with the genetic diversity the species had a century ago.

一个世纪前该物种拥有的 遗传多样性种群。

Though the specifics of this effort are unique,

虽然这项工作具有其独特性，

as more species face critical endangerment or functional extinction,

但随着更多物种濒临灭绝 或功能性绝种，

it’s also an arena for big questions:

也引出了一些不容忽视的问题：

do we have a responsibility to try to bring species back from the brink,

我们是否有责任尝试挽救

especially when human actions brought them there in the first place?

由于人类行为而导致濒危的物种？

Are there limits to the effort we should expend

我们为拯救濒危动物

on saving animals threatened with extinction?

所付出的努力有上限吗？