A Genetic Future For A Near-Extinct Rhino?

9:06 minutes

white rhino looking at camera
A southern white rhino. Scientists are working to create hybrid embryos of southern white rhino eggs fertilized by northern white rhino sperm. Photo by: William Murphy/flickr/CC BY-NC-SA 2.0

After the death of the last surviving male northern white rhino, the future looked dim for the endangered subspecies, which now numbers two infertile females.

But scientists have been working on a number of methods to rescue the rhino after all. Collections of sperm and DNA could allow southern white rhinos, which are a closely related but a separate subspecies, to carry lab-created embryos to term.

sudan the northern white rhino laying down
Sudan, the last male northern white rhino. Credit: Shutterstock

Writing in Nature Communications this week, one research group describes success at creating hybrid embryos—southern white rhino eggs fertilized by preserved northern white rhino sperm—in the lab. Such hybrids could be bred together until northern white rhino DNA dominated, essentially recreating the species. But how financially and scientifically feasible would this rescue effort be?

Terri Roth, director of the Center for Conservation and Research for Endangered Wildlife (CREW) at the Cincinnati Zoo and Botanical Garden, explains the methods and ethics of such a rescue.

Segment Guests

Terri Roth

Terri Roth is director of the Center for Conservation and Research for Endangered Wildlife at the Cincinnati Zoo & Botanical Garden in Cincinnati, Ohio.

Segment Transcript

JOHN DANKOSKY: This is Science Friday. I’m John Dankosky. Earlier this year, the world mourned the death of Sudan, the last male northern white rhino. Only his daughter and granddaughter remain of the subspecies, both unable to give birth to young. But researchers hoping to save them from extinction, have been working on assisted reproductive techniques with some help from the southern white rhino, a closely related subspecies.

Our research team in Italy, writing in Nature Communications this week, reports successfully creating hybrid embryos using northern white rhino sperm and southern white rhino eggs. Note that I said hybrid here, so how could this help to save the northern white rhino? Here to explain the how and why of all this is Terri Roth, director of the Center for Conservation and Research for Endangered Wildlife at the Cincinnati Zoo and Botanical Garden. Welcome, Terri to the show.

TERRI ROTH: Well, thanks, John.

JOHN DANKOSKY: So let’s start with this process. How hard is it to create embryos like the ones that the team in Italy is reporting working on?

TERRI ROTH: Well, you know it’s interesting, and it varies by species. But in the rhinoceros, it actually has been extremely difficult to develop embryos in the lab in an in-vitro system. So the progress they’ve made recently is really quite commendable. I think in the past we’ve only been able to produce a couple of embryos. And they only developed to two to five cells in number. And these are very well developed embryos. So it’s a big advancement.

JOHN DANKOSKY: Is this type of assisted reproductive technology being used in preserving other endangered species?

TERRI ROTH: To a very limited extent it is. And it’s being investigated for a number of other species. But these folks are taking a high-tech approach, and so a lot of what they’re doing has not yet been applied to the endangered species.

JOHN DANKOSKY: So why exactly do we need southern white rhino genetic material in this? Explain what we need here.

TERRI ROTH: I think a lot of people get tripped up on that a little bit. But there’s two parts to this. In one part, it’s just, scientists like to work on something that’s a little bit more plentiful to work out the kinks and to prove kind of proof of concept that this can be done. So I think in this case, of course no rhino oocyte is available in large numbers, but there are more southern white rhinos clearly, than northern. So by working with the southern white rhino they’re developing the protocols that they think will work pretty well when applied to the northern white rhino.

But the second piece to it, and I think this is what the scientists are hopeful about, is that these hybrid embryos do carry the genes of the northern white rhino. And we all are hoping that we can save some of those genes. And so, even by producing hybrids we’ve at least rescued some of the gene pool, and the idea would be long term to try to inbreed those hybrid offspring with each other to eventually dilute out the southern white rhino genes and concentrate the northern white rhino so that we have more of a northern white rhino population at the end of the day. Now, that is going to be full of challenges, because of course, you’re going to be inbreeding significantly and that often leads to inbreeding depression.

JOHN DANKOSKY: But you also say it’s going to take some time, right? I mean, this is not something that’s going to happen over the course of a couple of years.

TERRI ROTH: It will take some time, definitely. I think the scientists are hoping to produce their first offspring in three years. And I think even that is optimistic. But that’s only a start, because we’re going to need numerous offspring. And like I said, then they are going to have to breed together successfully.

And in the past, breeding the northern white rhino in a managed program has failed. So there are some challenges just in doing that as well.

JOHN DANKOSKY: I’ve said subspecies a few times. The northern white and the southern whites are closely enough related to create these hybrids in the first place. So tell us more, Terri, about the urgency to save this northern white rhino. If these animals are genetically so similar that they can be bred in this way, why is it so important to save this northern subspecies?

TERRI ROTH: Yeah, you know, there are some geneticists that disagree that they’re subspecies, and actually claim they’re almost so different you could call them species. So given that, we have to believe that there has been enough selection pressure on the northern white rhino to make them pretty different from the southern white rhino, at least in their ability to adapt to the northern habitats where they live. Therefore, if we want rhinos back in the northern habitats of Africa, we’re probably going to be better off to have northern white rhinos that we can put in those habitats.

I think there’s probably a good chance southern white rhinos could adapt. But we don’t really know for sure, and we don’t really like to take that kind of risk. So I think that’s why folks really want to save the northern white rhino. And it’s also the principle of the matter. We should not be letting species go extinct on our watch.

JOHN DANKOSKY: It’s on our watch, but it’s also because of us. I mean, tell us a little bit more about why the northern white rhino is so endangered.

TERRI ROTH: Yeah, the northern white rhino was actually on its way to becoming a conservation success story in late 1990s, early 2000s. There was a population of them in Garamba National Park and it was protected by rangers, who are supported by the International Rhino Foundation, and the numbers were increasing. And we believed at one point, we were up to at least 30 rhinos, which is a low number. But they were increasing and they were reproducing and they were doing well.

And then civil unrest broke out. And at that point, things got so dangerous in the territory that the rangers had to be removed from their work, because their lives were at risk. And once they were pulled out and the protection stopped, the rhinos were decimated by poaching, and just by the civil unrest that was going on in the country.

So really, in most cases that’s the kind of thing that’s driving rhinos to extinction more than anything else. It’s the loss of habitat, and it’s the poaching and the killing for various reasons. When we get to a point where we’re using these high-tech reproductive technologies, we’re acting as a triage unit. It’s a last gasp. And we really don’t want to get to this point with these animals.

JOHN DANKOSKY: But that’s such an important piece of this, though. If we are successful in getting the northern white rhino to breed again, and we’re getting more of them back in, but we’re not able to protect the species, then what happens? I mean, that’s part of conservation as well.

TERRI ROTH: It absolutely is, yes. Yes. This reproductive technology is just one tiny piece of it. And it can play an important role, but it can’t alone save the species. We need to have the habitat where the species can live. We need to be able to protect them.

Right now, we are facing a poaching epidemic in Africa that’s just been out of control now for the last eight years. And it’s extreme. It’s to the point where the animal populations that used to be increasing are now plateaued, and pretty soon they’re going to start to decrease. And so we’re going to start losing them again. That’s the thing we have to really get a handle on. And that requires a lot of work by a lot of countries. Even though it’s in Africa, it’s not just Africa’s problem. The consumers are in a lot of other countries.

JOHN DANKOSKY: Does this effort on behalf of the northern white rhino, does it point to us in a direction to protect other species? We’ve talked about this a little bit, but I’m wondering how widely this can be applied to species beyond the rhino?

TERRI ROTH: It’s a good question. You know, some of the techniques that have been used in this research have really only had some success in mice so far. So these scientists have taken those techniques and they’re starting to apply it to the rhinoceros. But every species is extremely different biologically. And so it’s going to be more challenging. We’re pretty certain of that. And whether or not it can ever succeed in the rhinoceros and how that applies to other endangered species, I’m not really sure. It could be a stretch to say it’s really going to be a panacea. I don’t see it as such.

JOHN DANKOSKY: In just a minute, we’re going to talk about Jurassic World and de-extinct dinosaurs. You mentioned this before, the idea of our obligation to bring things back from extinction. I am wondering if you’ve thought widely about this? If indeed, the northern white rhino goes away completely and we’re able to bring it or other species back, is that something that, if we have the power to do we should, Terri?

TERRI ROTH: You know, you could go either way with that question. On the one hand, with the northern white rhino, because it actually still is here and it hasn’t been that long– I mean, it’s probably been functionally extinct for five to 10 years, but we’ve still been living with it. There still is habitat that would support it. I believe it’s worth doing what we can to save the northern white rhino.

On the flip side, I don’t think it’s worthwhile putting a lot of resources into trying to bring back things like the woolly mammoth and the dinosaurs. We don’t have the proper habitat. Too much time has gone by. Too many things have changed. And the amount of resources and effort that would go into an effort like that, and the likelihood of it paying off is really pretty questionable.

JOHN DANKOSKY: Terri Roth is director of the Center for Conservation and Research for Endangered Wildlife at the Cincinnati Zoo and Botanical Garden. Terri, thanks so much for joining us. I appreciate it.

TERRI ROTH: You bet. Thanks, John.

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