The northern white rhino used to be widespread, but thanks primarily to poaching, today, there are only two left alive in the entire world Both are female, and both are infertile.

Unfortunately, that’s pretty much the end  of the road for any species. However, there’s a group of scientists out there that has an ambitious plan to revive the species using  in vitro fertilization.

That is to say, creating new, baby northern white rhinos in a lab. Can they really do it? Maybe.

Their preliminary results look pretty good. But… should we bring these animals back? It’s a more complicated  question than you might think.

I’m Jessie Kndusen Castenada, wildlife educator. I’m here to help break it down [intro]

In vitro fertilization is a technique where sperm and egg are brought together in a lab, rather than inside an animal’s body. And for a while now, some conservationists have eyed using IVF to save endangered species.

The idea is that we could use IVF to create a ton of embryos, and thus babies, from a  relatively small number of donors It’s fairly common to do this  with domesticated animals, and we have been able to do it  with a number of wild animals, like tigers for example. In January 2024, a group called BioRescue reported that they’d been able to induce a pregnancy using IVF in the southern white rhino, the sister subspecies to the northern white rhino. They kind of have to do it that way because of the lack of northern  white rhinos to try it out on, but they’re closely related enough that the plan would be to  use southern white rhinos as surrogates to carry northern white rhino embryos.

BioRescue has been aiming to do IVF in northern white rhinos for a while, so this seems like a big breakthrough. Because even though there are no living males left for the northern white rhino, we do have preserved sperm samples. Even more ambitiously, we also have preserved non-reproductive cells that we could coax into  turning back into stem cells – the kind of blank slate of our biology.

It hasn’t happened in rhinos, but we have done it in mice. Those stem cells could then be turned into reproductive cells. BioRescue has reported that they’ve been able to create and preserve about two dozen fertilized  northern white rhino eggs.

This all raises the hopes that  this can be part of a larger, step-by-step plan that would ultimately end in returning northern white  rhinos to the wild again. And… that’s great. Right?

The thing is, even though the idea of bringing  back an endangered species from the brink seems like an inherently good idea, this one is so close to gone that it’s worth carefully examining our assumptions and our reasoning. Notably, we want to hit three big questions: What’s the risk? What’s the payoff?

And will it fix the real problem? So first off, let’s talk about the risks. Specifically, the risks to the animals themselves.

They’re living creatures, and we have an ethical duty to make sure we’re not putting them through needless pain or danger. In order to perform IVF on a given species, you need to know a lot about that animal’s reproductive biology , like what triggers ovulation  and how often it happens. Knowing how to do it in tigers doesn’t tell you much about how to do it in rhinos.

Meaning you have to start from scratch, posing a risk to the animals used in that research. Furthermore, IVF can be a risky and complicated procedure. In order to harvest viable egg cells from  the rhinos, vets had to put these big, multi-ton animals under anesthesia, lie them down on their sides or their chests, and then use a needle to get to their ovaries.

That carries real risks. BioRescue noted that the rhinos they worked on seemed to recover quickly, and there were no adverse side effects reported. But if we’re going to apply this approach to saving other species, we’ll have to reinvent the wheel every time.

For some species, the risks or unknowns may be  too great to justify any payoff. And talking about payoff, that  brings us to the second question: will this actually work? Could we actually bring back the species with this scheme?

There are only two northern white rhinos left, and they’re not healthy. Najin is 31, and has an ovarian tumor and weak hind legs. Her daughter Fatu has untreatable degenerative endometriosis.

Neither can realistically carry a pregnancy, hence the need for southern  white rhinos as surrogates. This hasn’t been done yet, but the species are closely related enough to have produced one hybrid calf that we know of. So it should work.

But that’s not the only issue. Rebuilding a population  this way would take a while. Rhinos don’t grow all that quickly.

It would probably take at least 40 years to arrive at a herd of only a  couple dozen northern white rhinos. But such a herd could hypothetically exist. rebuilding a population this way would take a while But would it be a healthy, viable population? We’re down to two living individuals and frozen tissue from a handful more.

This is a textbook case of what’s known in population genetics as a bottleneck. No matter how much genetic diversity the ancestral population once had, the only genes that can ever be passed down now are the ones in those freezers. And a lack of genetic diversity makes it very difficult for a population to respond to other threats.

You could establish a breeding population only for them all to succumb to disease. That said, there’s some hope for  northern white rhinos in this regard. There’s evidence that the other subspecies, the southern white rhino, also went through a bottleneck.

One that might have been even more severe in terms of genetic loss, compared to if we used all the on-ice  northern white rhino material available to us. They were able to bounce  back to about 18,000 today. So maybe northern white rhinos have the capacity to be resilient too.

But that might not be true  for every endangered species: for another species in the same position, it might truly be too late. So with proper care, we may be able to reduce the  risk to individual animals and make any risks worth it, but here’s our final, and maybe the biggest question. Even if it does work, will it fix the real problem?.

Poaching is cited as the main  reason the species collapsed, and if they were to return, would likely be the greatest threat once again. IVF by itself wouldn’t fix this. And some experts have voiced worries that focusing on a technological solution may end up diverting resources away from existing conservation efforts.

Like, if you know you can  just press a “fix it” button to bring back a species later, are you still putting in the work to eliminate the threats to that species now? Is it still going to have a habitat to live in? That’s not an accusation, but it’s something to keep in mind.

It’s kinda like how reducing waste is better than recycling it. BioRescue, to their credit, has published their own ethical tools to address some of these points. Other experts have highlighted the need to find a way to protect these animals from poachers and other threats, and the importance of including local communities.

So, why are we talking about this? Saving endangered species is good. It’s important.

The thing is… it’s also hard. Human mistakes are what got these animals into this mess. More human mistakes could doom them forever.

It’s incredible that reproductive technology has a chance to bring back a species that is otherwise past the point of no return. It’s a wonderful glimpse of hope, made possible by science. Like with any new technology, it’s just really important to understand what  we’re doing and what the consequences might be.

Thanks for watching this episode of SciShow. I wanted to host it because I’m incredibly interested in conservation of endangered species. But there’s another place where you can see me every week, a nd that’s SciShow Kids!

It’s all about the adventures of my friend Squeaks the robot rat and his curiosity about everyday things. SciShow Kids is meant for first through third graders, and uses Next Generation Science Standards to teach science and inspire young minds. So point the young learner in your life to youtube.com/scishowkids. [ OUTRO ]