With only two remaining northern white rhinos, a groundbreaking in vitro fertilization (IVF) success offers hope to avert their extinction. Scientists achieved the first-ever rhino pregnancy, raising prospects for the endangered species' survival and potential benefits for other critically endangered rhinos.
Fatu (background), 19, and her mother Najin, 30, two female northern white rhinos, the last two northern white rhinos left on the planet, graze in their secured paddock on August 23, 2019 at the Ol Pejeta Conservancy in Nanyuki, 147 kilometres north of the Kenyan capital, Nairobi.
Revolutionizing Rhinoceros Reproduction
Using an embryo transfer technique akin to human IVF, scientists combined male and female rhino sex cells to create embryos. These embryos were implanted into a surrogate female for potential pregnancy and birth, a method previously employed in dogs and cloning horses and wolves.
The focus of this technique was the critically endangered northern white rhino subspecies, with the last known male, "Sudan," passing away in 2018, leaving only two females, Najin and Fatu, under armed protection at the Ol Pejeta Conservancy in Kenya. Without males to father new offspring, the northern white rhinos are deemed "functionally extinct."
In September 2023, BioRescue scientists implanted two embryos into a southern white rhino, a closely related and critically endangered subspecies, proving the technique's potential for white rhinos. These embryos were created from the gametes of captive southern white rhinos in Belgium and Austria and implanted into a surrogate residing in the Ol Pejeta Conservancy.
Despite the successful pregnancy, scientists only discovered it during a necropsy of the deceased surrogate, Curra, who succumbed to a bacterial infection unrelated to the embryo transfer procedure. Retrieving a lifeless 70-day-old fetus, measuring just 2.5 inches, from the rhino's womb, the BioRescue team, while saddened by Curra's death, remains optimistic about future embryo transfers.
Thomas Hildebrandt, project leader at BioRescue, expressed overwhelming satisfaction with proof of the technique's success, considering it a pivotal moment for the northern white rhino's survival despite the tragic circumstances.
Had Curra survived, the chances of a successful birth were estimated at around 95%, according to Cesare Galli, CEO of Avantea Laboratories, emphasizing that most complications with embryo transfers occur within the first 50 days. Once past this period, pregnancies generally proceed to term.
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Impregnating Northern White Rhino Via IVF
The BioRescue team plans to conduct another southern white rhino embryo transfer later this year, with future aspirations to attempt the procedure on Najin and Fatu, the last two northern white rhinos. The researchers anticipate success in implanting a northern white rhino embryo into a southern white rhino surrogate, as the two subspecies are deemed sufficiently similar for development.
The innovative approach holds promise for aiding other critically endangered rhino species, such as the Asian Javan rhinoceros and the Sumatran rhinoceros, both with populations under 100 individuals.
BioRescue has generated 30 viable northern white rhino embryos using frozen sperm from deceased males and eggs from Fatu. The first embryo transplants into living females are expected within the next few years, potentially as early as May or June
To determine the optimal fertile period, regular ultrasounds aren't immediately feasible at the conservancy. Instead, a sterilized male rhino acts as a "teaser" for the female, and the success of the recently sterilized male's freedom from residual sperm must be confirmed over a few months.
Once the ideal time is identified, the mating act signals readiness for a successful surgical embryo implant about a week later. Conservationists at the conservancy are vigilant during this time, as white rhinos typically mate for an extended period, and the act serves essential reproductive functions for the female.
Precautions, including a new enclosure and disinfection protocols, are established to protect the selected surrogate mother from bacterial infections during the process. The final step involves waiting for the female rhino to enter estrus, signaling her readiness for the egg implant.
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