Name: The last living members of an extinct species - Jan Stejskal
Uploaded: 2020-10-19T21:01:10.000Z
Duration: 5 min 32 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

In the savannahs of Kenya, two female northern white rhinos, Nájin and Fatu, munch contentedly on the grass.

At the time of this video's publication, these are the last two known northern white rhinos left on Earth.

Their species is functionally extinct — without a male,  Nájin and Fatu can't reproduce.

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

The story starts about 50 years ago, when poachers began illegally hunting thousands of rhinos across Africa for their horns.

This, combined with civil wars in their territory, decimated northern white rhino populations.

Concerned conservationists began trying to breed them in captivity in the 1970s, collecting and storing semen from males.

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

Nájin, and her daughter Fatu  were the last two.

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

Though Nájin gave birth to Fatu, she now has weak hind legs, which could harm her health if she became pregnant again.

Fatu, meanwhile,  has a degenerated uterine lining.

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

But there was one glimmer of hope: artificial reproduction.

With no living males and no females able to carry a pregnancy, this is a complicated and risky process to say the least.

Though scientists had stored semen,  they would have to collect the eggs — a complex procedure that requires a female to be sedated for up to two hours.

Then, they'd create a viable embryo in the lab — something that had never been done before, and no one knew how to do.

Even that was just the beginning — a surrogate mother of another rhino species would have to carry the embryo to term.

Females of a closely related species,  the southern white rhino, became both the key to developing a rhino embryo in a lab and the leading candidates for surrogate mothers.

Northern and southern white rhinos diverged about a million of years ago into separate — though still closely-related — species.

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

In a fortunate coincidence,  several female southern white rhinos needed treatment for their own reproductive problems, and researchers could collect eggs as part of that treatment.

In Dvůr Králové Zoo in October 2015, experts of IZW Berlin began collecting eggs from southern white rhinos and sending them to Avantea, an animal reproduction laboratory in Italy.

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

Once they mastered the technique, researchers extracted Nájin and Fatu's eggs on August 22, 2019 and flew them to Italy.

Three days later, they fertilized the eggs with sperm from a northern white rhino male.

After another week, two of the eggs made it to the stage of development when the embryo can be frozen and preserved for the future.

Another collection in December 2019  produced one more embryo.

As of early 2020, the plan is to collect Nájin and Fatu's eggs three times a year if they're healthy enough.

In the meantime,  researchers are looking for promising southern white rhino surrogate mothers — ideally who've carried a pregnancy to term before.

The surrogacy plan is somewhat of a leap of faith — southern and northern white rhinos have interbred both during the last glacial period and more recently in 1977, so researchers are optimistic a southern white rhino would be able to carry a northern white rhino to term.

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

Still, transferring an embryo to a rhino is tricky because of the shape of the cervix.

The ultimate goal, which will take decades, is to establish a breeding population of northern white rhinos in their original range.

Studies suggest that we have samples from enough individuals to recreate a population with the genetic diversity the species had a century ago.

Though the specifics of this effort are unique, as more species face critical endangerment or functional extinction,  it's also an arena for big questions.

Do we have a responsibility to try  to bring species back from the brink, especially when human actions brought them there in the first place?

Are there limits to the effort we should expend on saving animals threatened with extinction?

How are conservationists and communities helping endangered species recover?

See how some regions are working to repopulate vulture communities by opening vulture restaurants with this video, or explore how we can sustainably farm the ocean to prevent overfishing with this video.