TedEd: The last living members of an extinct species

A TedEd by Jan Stejskal

Nájin and Fatu, who live in the savannahs of Kenya, are the last remaining members of their species, the northern white rhinoceros. Unfortunately, they are both female, meaning the species is functionally extinct because they cannot reproduce. But what if we could still save them? About 50 years ago, poachers began illegally killing thousands of these animals for their horns. The northern white rhino population quickly shrank, and panicked researchers tried to breed them in captivity. Nájin and Fatu are the last two remaining from the total of 4 bred in captivity. Neither can have a calf due to medical issues. In 2018, Sudan, the last male of their speices, died. The only hope is artificial breeding from stored semen. First, eggs would have to be removed from a sedated rhino in a procedure that takes up to 2 hours. Then, the cells would be used to create an embryo in a lab, which no one knew how to do. Then, a surrogate mother in another species would have to bear the calf. The southern white rhino, which is a closely related species that diverged from their northern counterparts a million years ago, could work. Researchers experimented with southern rhino eggs and discovered a way to create an embryo in an Italian lab. In 2018~19, Nájin and Fatu's eggs were sent there, and 3 viable embryos were created and frozen for later use. Researchers will continue taking eggs three times a year. When a good surrogate southern rhino mother is found, she would be injected with the embryo. It helps that the two species have similar pregnancy lengths. If this works, researchers hope to create a breeding population with genetic diversity from a century ago over the next few decades. This opens up more questions. Humans have driven many animals to the brink of extinction. Is it our duty to bring them back, and how far should we go to do it?