Scientists get closer to repopulating nearly extinct northern white rhino
A ranger with a northern white rhino.
Efforts to save the northern white rhino are now in the home stretch, with embryos ready to be implanted into a surrogate mother.
On October 31, 2023, a consortium of scientists and conservationists from around the world announced that a total of 29 embryos had been preserved in a laboratory, awaiting the right time to complete the process of in vitro fertilisation (IVF).
Northern white rhinos.
The northern white rhino is perhaps the rarest mammal in existence today, with only two females known to exist, currently being kept under strict protection at the Ol Pejeta Conservancy in Laikipia County. The two, Najin and her daughter Fatu, both born in a zoo in the Czech Republic in 1989 and 2000 respectively, provide oocytes (retrieved immature egg cells) for the advanced breeding programme as they are unable to carry a pregnancy themselves.
For hundreds of years, this subspecies roamed freely across much of the Central African Republic, Chad, Sudan and the Democratic Republic of Congo (DRC), but political instability in the region and demand for their horns led to their extinction in the wild.
With no known subspecies of this rhino in the wild, efforts to prevent total extinction turned to Safari Park Dvůr Králové, a zoo in the Czech Republic, where two males and two females were transferred to Kenya in 2009 in the hope that a natural environment close to their original habitat would encourage them to breed.
Unfortunately, the mating observed did not result in pregnancy and the two males died, with the last, named Sudan, succumbing to age-related complications in 2018.
Samuel Mutisya, Head of Research at Ol Pejeta Conservancy.
The process of harvesting oocytes for fertilisation and later transplantation into a surrogate mother, a southern white rhino, was informed by examinations which showed that neither could support a pregnancy to the full 16-month gestation period.
The project to save the northern white rhino is a collaboration between a team of scientists and conservationists from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW), Ol Pejeta Conservancy, Safari Park Dvůr Králové, Kenya Wildlife Service (KWS) and the Wildlife Research and Training Institute (WRTI) at Ol Pejeta Conservancy in Kenya, collectively known as the BioRescue team.
“Oocytes collected from time to time have been flown to Italy for purposes of maturing them and once they mature you fuse them with preserved sperms collected from male rhinos (Sudan and others) before they died. At this stage we have been able to produce 29 embryos, which are preserved in liquid nitrogen to be implanted on a southern white rhino to carry the pregnancy,” says Samuel Mutisya, the head of Research and Species Conservation at Ol Pejeta Conservancy.
He describes the latest development as a milestone, noting that it has taken a while to make a breakthrough since advanced assisted reproductive technologies (aART) began in 2015. Although IVF has been performed on other mammals, this is the first time it will be attempted on a rhino.
“Efforts to recover this particular subspecies of northern white rhino has taken a group of scientists and rhino managers to consider which particular method of reproduction is to be adopted. After a bit of consultation, we arrived at the IVF method where a sperm cell is fused with an ovum to create an embryo since it is efficient. Unfortunately, the techniques of doing this had not been developed, nor the equipment to be able to undertake some of the detailed and quite complex procedures that need to be done,” explains Mutisya.
He adds that the BioRescue team is currently working on perfecting the technology to implant these special embryos into a southern white rhino once it is on heat. Females for this project have been identified at Ol Pejeta Conservancy and are accompanied by sterilised teaser males to help detect when their mates are on heat.
Mutisya reveals that a southern white rhino was chosen to carry the embryo because it is a close relative of the northern white rhino and has the same gestation period, and the task now is to determine the best time to implant the embryo.
However, in order to perfect the procedure, which has not been done before, the first step would be to implant common white rhino embryos and, if successful, the next step would be to implant a northern white rhino embryo into the identified surrogate mother.
In the meantime, the BioRescue team will continue to make routine visits to Ol Pejeta Conservancy to collect oocytes from Fatu. Her elderly mother has been retired from the project.
Their most recent visit, the thirteenth since 2015, was in May this year, when they harvested 18 eggs. These were matured and fertilised at the Avantea laboratory in Cremona, Italy, resulting in the production of five more embryos, bringing the total to 29. The sperm used for fertilisation came from two different bulls to improve genetic diversity.
