Females Najin and Fatu at Ol Pejeta Conservancy, Kenya, are the only remaining northern white rhinos in the world. To prevent the extinction of the northern white rhino, an international consortium of scientists and conservationists called BioRescue led by Leibniz-IZW has been harvesting immature egg cells (oocytes) from the two females and artificially inseminating these using frozen sperm from deceased males in order to create viable northern white rhino embryos since 2019. In the near future, the embryos will be transferred to southern white rhino surrogate mothers to create northern white rhino offspring.

On March 28th, 2021, 19 oocytes were retrieved from Fatu’s ovaries using a probe guided by ultrasound, after the animal was placed under general anaesthesia. Fatu is the younger of the two northern white rhinos, Najin’s daughter and Sudan’s granddaughter. Both the anaesthesia and the ovum pickup procedure went smoothly and without complications. After incubating and maturing the egg cells at Avantea’s laboratory in Italy, 14 of them were fertilised with thawed sperm from deceased northern white rhino bull Suni using a procedure called intra-cytoplasmic sperm injection (ICSI). Four fertilised oocytes developed into viable embryos that are now stored in liquid nitrogen along with the five embryos already created in previous procedures. There are now a total of nine embryos, all derived from oocytes collected from Fatu.

“We are excited with the laboratory outcome of the last ovum pick-up in March. With nine pure northern white rhino embryos now developed, the partners in the project should embark on the next phase of the project –embryo transfer to the surrogate southern white females at Ol Pejeta Conservancy. We are eager to get the progeny from the project that will guarantee survival of the species”, says Kenya’s Tourism and Wildlife Cabinet Secretary, Hon. Najib Balala.

Embryo development was achieved with the help of Geri®, an innovative benchtop incubator with integrated continuous embryo monitoring capabilities designed to provide an individualised and undisturbed incubation environment, and donated by Merck.

During the most recent procedure, Najin, who is now 31 years old, was put under light sedation whilst standing and examined via ultrasound. After the results of the ultrasound, the team decided not to attempt the procedure as she had not appeared to have developed enough promising oocytes. The consortium will soon thoroughly discuss if and how to continue the oocyte collections with Najin, as ethical risk assessments are a pivotal part of the programme.

Another very important step in the success of the BioRescue programme was the selection and sterilisation of the southern white rhino bull Owuan in December 2020. The animal was sterilised by the BioRescue team with a minimally invasive non-surgical procedure using state-of-the-art equipment. The sterilisation went smoothly and without any complications. In March 2021, the BioRescue team confirmed via electroejaculation that the sterilisation was indeed successful. Owuan has recovered well from the examinations and is up to his future role: as a sterilised bull, he will reliably indicate through his behaviour the reproductive cycle of potential surrogate mothers without any risk of impregnating them. This information is a crucial prerequisite for transferring the embryos to surrogate mothers at the correct timing of their reproductive cycle. Under the guidance of Kenya Wildlife Service, the team carefully planned the location of selected southern white rhino females for Owuan’s company and his introduction to them will take place in the coming weeks.

The BioRescue research programme, significantly funded by the German Federal Ministry of Education and Research (BMBF) and additional donors such as foundation Nadace ČEZ, the philanthropist Dr Richard McLellan and Merck EMD foundation, will continue with its ambitious plan to create more embryos from oocytes collected from the northern white rhino females in a three to four-month cycle as long as the COVID-19 pandemic allows for the team to travel to Kenya. With the sterilisation confirmed and relocation of surrogates planned, the next milestone of the programme is getting within reach.