The last living members of an extinct species Jan Stejskal
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.
How can that be?
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 hindlegs,
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 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?