by Najin and her daughter Fatu, the world’s last two northern white rhinos, live in the freshwater evolutionary zone: the last living proof of a lineage that goes back millions of years but is effectively extinct.
But this week, scientists came a step closer to bringing the species back from the brink of oblivion by performing the first successful embryo transfer in a related white rhinoceros species.
The ultimate goal of restoring an entire herd of northern white rhinos using a bank of frozen eggs, sperm and embryos and gene editing technologies may sound like a case of tech junk – scientists trying to play God. But the team behind the project, and others, say IVF and other assisted reproductive technologies (ART) could revolutionize conservation efforts in some species and buffer against the devastating effects of climate change and habitat loss.
“Scientists can offer to reverse some of these dramatic human mistakes,” said Professor Thomas Hildebrandt, from the Leibniz Institute for Zoo and Wildlife Research in Berlin and head of the BioRescue rhino project. “We don’t play God. We try to preserve what God created. We only bring back what was on this planet and was destroyed by humans.”
Hildebrandt sees the technology as a last-ditch insurance policy for “cornerstone” species, such as the northern white rhino, whose loss would lead to a cascade of knock-on effects on entire ecosystems. But in many species, efforts are underway long before species reach those final levels of decline.
“I’ve worked on giant pandas, great apes, elephants,” Hildebrandt said. His team previously coordinated the collection of semen from wild elephants to improve genetic diversity in zoo populations. The practical challenges can be significant: elephants must be immobilized by helicopter and sperm must be extracted by electrolysis. With rhinoceros, the collection of ovaries and embryo transfer is done through the rectum, because the ovaries are almost 2 meters deep inside the abdomen. “We’re dealing with a 2.2-ton animal,” Hildebrandt said.
Adapting IVF protocols developed for commercial livestock is not always simple, according to Dr Andrés Gambini, from the University of Queensland, who is developing IVF techniques for the endangered Somali wild ass – a species of donkey – and koalas.
“We thought the horse is very similar to the 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 can help preserve the genes of populations that are alive today. “We may not transfer the embryos tomorrow or use those samples today but we know we can use them in the future,” he said. “We have to do it.”
Dr. Jennifer Barfield, a veterinary scientist at Colorado State University, is using IVF to help conserve bison in Yellowstone national park. The herd is vulnerable to a bacterial disease, brucellosis, which can cause miscarriages and infertility, but IVF can be used to produce healthy embryos that can be transferred to disease-free centers.
“These technologies are also used to transfer valuable genetics between populations in the form of sperm, eggs, or embryos which are, in many ways, easier than moving live animals,” Barfield said.
Long before species reach critical numbers, genetic diversity can become an issue. Habitat loss may split species into isolated pockets of territory, potentially leading to genetic bottlenecks and exploration. ART can act as a genetic bridge between small and endangered populations.
IVF and artificial insemination are also increasingly being used in zoos, instead of transporting potential replacements around the globe, when animal pairs have failed to reproduce or may have introduced captive to be a danger.
“A lot of animals are selective of each other, but with captive breeding, you often don’t have the ability to choose a mate,” said Professor Simon Girling, head of veterinary services at the Royal Zoological Society of Scotland, who oversaw the pandas. Tian Tian and Yang Guang, who failed to conceive during their ten year stay at Edinburgh zoo.
“When you had one of each – and both of us didn’t – there was no chance,” Girling said. In the absence of a romantic spark, IVF was attempted and Tian Tian had at least four chemical pregnancies, but none of them implanted, for reasons that remain unclear.
“Several eminent scientists came in and wrote reports and we implemented all the recommendations. We have bamboo shipped in from China,” Girling said, adding that several other zoos with pandas have had positive results.
IVF is not going to solve the loss of species and, according to Hildebrandt, there is more to species than just their genes. “We are under a lot of pressure in terms of time to produce the first pups to save the social legacy,” he said. “The living animals speak the language, they know how to behave like a northern white rhino. The whole package must be respected. We want ungulates fit for the wild, not zoo exhibits.”
“We should really change our relationship with nature,” he said. “I can see that the younger generation has a much better attitude towards this.”
