Successful embryo transfer gives hope for the northern white rhino

The critically endangered northern white rhino subspecies (Ceratotherium simum cottoni), whose population has fallen to two female animals, could be saved thanks to a major success in reproductive medicine. Scientists have successfully carried out an embryo transfer in the southern white rhinoceros (Ceratotherium simum simum), even though the first attempt ended tragically: the surrogate mother died together with the 70-day-old fetus because of a bacterial infection unrelated to the procedure. Despite the unfortunate outcome, the incident underscores the progress being made in reproductive medicine for animals and the potential possibility of breeding endangered species in the laboratory.

The fetus, which would have grown into a bull, measured 6.4 centimeters at the time of death. The Italian geneticist Cesare Galli, whose laboratory cultured the embryo from egg and sperm cells, emphasized that the chances of survival had been above 95 percent.

A team of international researchers from BioRescue, a German government-supported conservation consortium, has carried out the first successful embryo transfer in southern white rhinoceroses. This project paves the way for applying this promising technique to the rare northern relatives. Although this method is common in humans, horses, and cattle, it had never before been used in rhinoceroses. The fact that embryo transfer works in rhinoceroses therefore represents a decisive breakthrough.

Hope for the northern white rhino

After the death of the last male northern white rhinoceros in 2018, the fate of the subspecies seemed sealed. At present, only two infertile female northern white rhinos remain, mother and daughter, living under constant guard in a wildlife reserve in Kenya. But the successful embryo transfer in the southern subspecies is now opening up new possibilities.

By May or June of this year, the scientists plan to implant the first northern white rhinoceros embryo. The 30 remaining embryos, created from sperm of deceased males and egg cells from a living female, are being stored at -196 °C in liquid nitrogen in Berlin, Germany, and Cremona, Italy.

The embryo is injected through the rectum of the surrogate mother, a southern white rhino. If the pregnancy is successful, lasting 16 months, this would result in the first northern white rhinoceros since 2000. This breakthrough could also pave the way for protecting the equally endangered Sumatran rhinoceros, of which only 40 individuals still exist in the wild.