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The Last Two of Their Kind

An international team of researchers from Berlin headed by Professor Thomas Hildebrandt is trying to use state-of-the-art reproductive medicine to save the critically endangered northern white rhinoceros from extinction – a race against time.

Oct 02, 2019

Literally unique: These two rhinoceros cows, Najin (left) and Fatu, are the last northern white rhinoceroses in the world. Since all the bulls have died off, researchers are taking an innovative tack to harvest reproductive cells.

Literally unique: These two rhinoceros cows, Najin (left) and Fatu, are the last northern white rhinoceroses in the world. Since all the bulls have died off, researchers are taking an innovative tack to harvest reproductive cells.
Image Credit: Elodie Sampere

Najin and her daughter, Fatu, are the last of their kind: the only two remaining northern white rhinoceroses in the world. Born at a wildlife park in the Czech Republic, the two rhinos now live on a reserve in Kenya – protected against poachers, who ruthlessly hunt these animals for their valuable horns.

By the traditional definition, that means the northern white rhinoceros is extinct: There are no living bulls, and neither Najin nor Fatu can bear any calves due to health problems.

To save the subspecies from complete extinction, a team of researchers from Berlin headed by Thomas Hildebrandt, a professor at the Department of Veterinary Medicine of Freie Universität and a department head at the Leibniz Institute for Zoo and Wildlife Research (IZW), is taking an unusual approach. Their goal is to use in vitro fertilization and an innovative technique of harvesting reproductive cells to breed new rhinos.

“BioRescue” is the name of the large-scale project, on which researchers from the IZW and the Max Delbrück Center for Molecular Medicine are working together with international partners. The German Federal Ministry of Education and Research (BMBF) has pledged four million euros in support.

The team of researchers is pursuing an ambitious goal: The idea is to harvest egg cells from Najin and Fatu and then fertilize them using frozen sperm taken from the last four northern white rhinoceros bulls, all dead in the meantime. The embryos created will be implanted in females of the southern white rhinoceros subspecies, which is closely related to their northern counterparts. Even just harvesting the egg cells is a tricky process, says Hildebrandt, who describes it as a milestone in the project. That milestone was reached in August, when five egg cells each were taken from Najin and Fatu.

But even if the plan is a success and the researchers manage to produce a northern white rhinoceros through artificial insemination in the next three years, that will not mean the subspecies is safe from extinction. “Sudan, one of the donor bulls, is Fatu’s father, which means there is too little genetic diversity between the frozen sperm and the egg cells taken from Najin and Fatu.”

With that in mind, researchers from the Max Delbrück Center for Molecular Medicine (MDC), Helmholtz-Zentrum München, and Kyushu University, in Japan, are working with American partners on a second approach at the same time. “They are trying to extract reproductive cells from the bodily cells of other dead northern white rhinoceroses. These artificially cultivated cells could be used to enlarge the gene pool enough to build a new population,” explains Sebastian Diecke, head of the stem cell lab at the MDC.

Professor Thomas Hildebrandt studies egg cells taken from female rhinoceros Fatu under a microscope.

Professor Thomas Hildebrandt studies egg cells taken from female rhinoceros Fatu under a microscope.
Image Credit: Elodie Sampere

This method has only been tested on mice so far; researchers will have to wait and see whether it is also suitable for rhinoceroses. “That won't happen from one day to the next, of course,” Hildebrandt says. The research project is due to run for 25 years. That sounds like a lot, but Hildebrandt and his team are currently hard at work.

After all, aside from the genetic aspect, there is also a social inheritance to take into account. Without Najin and Fatu, any young northern white rhinoceros the scientists manage to breed will never learn how to behave. “Our goal is for the next generation to get to know both of the ladies and grow up with them,” Hildebrandt explains.

Project Intended as a Call for Greater Conservation Efforts

The researchers’ work goes beyond simply trying to save one subspecies of rhinoceros from extinction: “We are developing a new concept for conserving species, one that can be used as a blueprint for other species as well. That’s why the project is called BioRescue, and not just RhinoRescue.”

The northern white rhinoceros is viewed as a key species. Its disappearance would upset the entire ecological balance, Hildebrandt explains. “Other animal species are already affected by the rhino’s absence today. For example, there are insects that live off these rhinos’ dung, and plants whose seeds are spread by rhinoceroses.” If the insects disappear, insect eaters could also move to other areas.

And that, in turn, could affect people. Bats, for example, are among the most dangerous vectors for diseases that can pass to humans. If they can no longer find enough insects and plants to eat, they may move elsewhere – causing a threat to the people who live there. “Thinking that you can take such an important element out of the natural world and nothing will happen is grossly negligent,” the veterinary researcher says.

The funding received from the German federal government and the support shown by the business sector and private donors are hugely important to the project, Hildebrandt points out. In principle, though, the issue of protecting nature and prompting people to be better stewards of natural resources is less of a financial question. That is what the team aims to urge people to do. “Our work is about making sure we move back toward balance in the natural world. In this way, we might be able to fix mistakes that humans have made in the past – in hopes that they won’t be made again at all in the future. We always say that evolution has given us a library, and we humans are destroying the books without ever having seen them.”

This text originally appeared in German on September 26, 2019, in the Tagesspiegel newspaper supplement published by Freie Universität.