Ten years ago, the last wild northern white rhinos (Ceratotherium simum cottoni) were killed in the Democratic Republic of the Congo. These magnificent mammals, which once roamed the central African savannahs by the thousands, were relentlessly poached to extinction for their horns. Their survival in captivity has been equally ill-fated. Following the death of Nola, a 41-year-old captive female in 2015, just 3 of these Critically Endangered beasts remain on the planet. This trio, kept highly guarded in the Ol Pejeta Conservancy in Kenya, are the species’ last and only hope.

In a last-ditch effort to save this white rhino sub-species, which currently appears doomed for extinction, an international group of scientists met to discuss an enterprising plan to rejuvenate the breeding population. The proposed ideas and strategies have been published in the international journal Zoo Biology.

The reason this plan is so audacious is that it will not be using standard breeding techniques. Natural reproduction is not an option. 42-year-old Sudan, the only surviving male, has a very low sperm count; his daughter Najin has very weak legs and therefore would not be able support the weight of a mounting male or the strength to carry a baby; and her daughter Fatu has an untreatable uterine disorder, preventing her from becoming pregnant. Many would therefore consider the subspecies functionally extinct.

But teams from San Diego Zoo Global and the Leibniz Institute for Zoo and Wildlife Research, as well as specialists in stem-cell and reproductive biology, propose that in vitro fertilisation (IVF) techniques should be implemented. Using previously frozen sperm cells from Sudan and four other males, and eggs from Najin and Fatu, the hope is to create and implant an embryo into a surrogate rhinoceros, who will then give birth to a northern white rhino. This surrogate mother would be a southern white rhinoceros, a separate sub-species that currently numbers around 20,000 individuals.

There are many hurdles to overcome. “The attempt to save the northern white rhinoceros, requires new technologies, new approaches and solutions to prevent the imminent extinction,” says Dr. Joseph Saragusty, andrologist at the Leibniz Institute for Zoo and Wildlife Research in Berlin.

A viable rhino embryo has never been created using IVF, let alone implanted into a surrogate. Furthermore, the scientists need to breed a population with a diverse gene pool, to give them the best chance of thriving in the wild. This cannot be achieved with eggs from the current females, so artificial gametes must be created using frozen stem cells, a technique that has previously been demonstrated in mice. Scaling this technique to rhinos is a grand challenge, and would be a major scientific step.

This ambitious plan hasn’t been received well by all scientists. “This says we can let species go to the very brink of extinction and modern technology can bring them back,” says Stuart Pimm, a conservation biologist at Duke University in Durham. “There is a very substantial moral hazard in that.”

To be successful, this conservation strategy will require many resources and a substantial amount of money – into the several millions of pounds. Funding available for global conservation efforts is limited, and many think that this money would be better spent protecting habitats, or species that have not yet disappeared from the wild. “They should not be pushing this idea that they’re saving a species.” Argues Michael Knight, chair of the IUCN’s African Rhino Specialist Group. “If you want to save a [rhino] species, put your money into southern white conservation.”

The researchers have considered the moral issues and costs of saving the northern white rhino, but remain adamant that these drawbacks can be outweighed by future benefits. They hope that if successful this effort could pave the way for the conservation of other mammals on the brink of extinction.

REFERENCES

Saragusty, J., Diecke, S., Drukker, M., Durrant, B., Friedrich Ben-Nun, I., Galli, C., Göritz, F., Hayashi, K., Hermes, R., Holtze, S., Johnson, S., Lazzari, G., Loi, P., Loring, J. F., Okita, K., Renfree, M. B., Seet, S., Voracek, T., Stejskal, J., Ryder, O. A. and Hildebrandt, T. B. (2016), Rewinding the process of mammalian extinction. Zoo Biol.. doi: 10.1002/zoo.21284

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