Najin and her daughter Fatu, the world’s last two living northern white rhinos, live in an evolutionary twilight zone: the last living evidence of a lineage that dates back millions of years but is functionally extinct.
But this week, scientists moved one step closer to bringing the species back from the brink of extinction by performing the first successful embryo transfer in a related white rhino species.
The ultimate goal of reviving an entire herd of northern white rhinos using a bank of frozen eggs, sperm and embryos and gene-editing technologies may seem like a case of technological hubris, with scientists trying to play god. But the team behind the project and others say IVF and other assisted reproductive technologies (ART) could transform conservation efforts in some species and buffer against the devastating effects of climate disruption and habitat loss.
“Scientists may offer to rewind some of these dramatic mistakes made by humans,” said Prof Thomas Hildebrandt, from the Leibniz Institute for Zoo and Wildlife Research in Berlin and head of the rhino BioRescue project. “We are not playing God. We are trying to protect God’s creation. “We are only bringing back what was on this planet and what was destroyed by humans.”
Hildebrandt sees the technology as an insurance policy of last resort for “cornerstone” species like the northern white rhino, whose loss would have knock-on effects for the entire ecosystem. But in many species, efforts are underway long before species reach such eventual levels of decline.
“I’ve studied giant pandas, great apes and elephants,” Hildebrandt said. His team had previously coordinated the collection of sperm from wild elephants to increase genetic diversity in zoo populations. Practical difficulties can be significant: Elephants must be immobilized using a helicopter and sperm must be extracted using electro-ejaculation. In rhinos, ovarian collection and embryo transfer are carried out through the rectum, since the ovaries are located almost 2 meters deep in the abdomen. “We are dealing with a 2.2-ton animal,” Hildebrandt said.
Dr. from the University of Queensland, who developed IVF techniques for the endangered Somali wild ass (a type of donkey) and koalas. According to Andrés Gambini, it is not always easy to adapt IVF protocols developed for commercial livestock farming.
“We thought the horse was a lot like a donkey, but we did the same thing and it didn’t work,” he said. “They have a different biology.”
The work is still ongoing, but it could help preserve the genes of populations alive today. “We may not be able to transfer embryos tomorrow or use these samples today, but we know we can use them in the future,” he said. “This is a must for us.”
Dr Jennifer Barfield, a veterinary scientist at Colorado State University, is using IVF to help protect bison in Yellowstone national park. The herd is vulnerable to brucellosis, a bacterial disease that can cause miscarriage and infertility, but IVF can be used to produce healthy embryos that can be transferred to disease-free surrogate mothers.
“These technologies are also being used to move valuable genetics in the form of sperm, eggs or embryos between populations, which in many ways is easier than moving live animals,” Barfield said.
Genetic diversity may become a problem long before species reach critical numbers. Habitat loss can cause species to fragment into isolated areas, potentially causing genetic bottlenecks and inbreeding. ART may serve as a genetic bridge between small at-risk populations.
Instead of transporting potential mates around the world, IVF and artificial insemination are increasingly being used in zoos when animal pairs are not breeding or where introduction into captivity would pose a danger.
“Many animals are mate-selective, but in captivity breeding you often don’t have the ability to choose a mate,” said Prof Simon Girling, head of veterinary services at the Royal Zoological Society of Scotland, which oversees pandas. Tian Tian and Yang Guang, who were unable to conceive during their ten-year stay at Edinburgh Zoo.
“When you have both and we didn’t get along, we didn’t stand a chance,” Girling said. In the absence of a romantic spark, in vitro fertilization was attempted and Tian Tian experienced at least four chemical pregnancies, but none of them implanted for reasons that are still unclear.
“Many important scientists came and wrote reports and we implemented all the recommendations. “We brought bamboo from China,” said Girling, adding that some other zoos have achieved positive results regarding pandas.
In vitro fertilization will not solve species loss, and Hildebrandt points out that species are more than just genes. “We are really under time pressure to produce the first calves to save the social legacy,” he said. “Living animals speak the language, they know how to behave like the northern white rhino. The whole package needs to be respected. “We do not want animals to be exhibited in the zoo, but rather animals with hoofs suitable for nature.”
“We must dramatically change our relationship with nature,” he added. “I can see that the younger generation has a much better attitude about this.”