New Artificial Insemination Technique Successfully Breeds Critically Endangered Scimitar-Horned Oryx

On June 30, the Smithsonian Conservation Biology Institute (SCBI) welcomed a new scimitar-horned oryx, born to mother Rizzo after she was impregnated by an assisted reproduction procedure in October of 2017. The calf’s arrival marks the first birth of an oryx to be conceived through artificial insemination without the need for risky anesthesia. This success sets a landmark precedent as scientists continue to push for the reintroduction of this critically endangered species into the wild, where it is has been, until very recently, considered extinct.

As little as a hundred years ago, large, bustling herds of these long-horned antelope roamed the arid plains of Northern Africa. To cope with dry desert climate, oryx have a remarkable tolerance for sweltering heat and are able to withstand an internal body temperature of 116 degrees Fahrenheit, minimizing loss of water through sweat. In their natural habitat, where temperatures regularly soar into the triple digits, their white coats keep them cool in the harsh sunlight.

But subsequent overhunting and the encroachment of human-fed livestock throughout the 20th century quickly drove the scimitar-horned oryx to the point of critical endangerment, and scientists could find no evidence of wild populations beginning in the early 1990s until 2016.

However, two years ago, SCBI, in collaboration with the Sahara Conservation Fund and the governments of Abu Dhabi and Chad, released the first round of oryx raised in captivity into the wild. Due to successive rewildings and continued breeding in their natural environment, Chad’s oryx population now numbers around 100. Even with these early successes, the scimitar-horned oryx’s conservation status remains the priority of zoologists around the world, and scientists will continue to breed calves in captivity for the purposes of reintroduction.

At their headquarters in Front Royal, Virginia, SCBI scientists performed Rizzo’s artificial insemination with a sample of approximately 300 million motile oryx sperm—10 times more than previously used for such procedures. The sire, whose sperm was frozen in 2011, was himself a calf born of the SCBI's early artificial insemination pilot programs in the 1990s.

To maximize chances of pregnancy, biologists hormonally induced Rizzo to ovulate in time for the procedure. Treatment with prostaglandins, which are naturally produced in almost every tissue of humans and other animals, safely and effectively hits the reset button on a non-pregnant female’s reproductive cycle, all but guaranteeing that she will go into estrus, or heat, within a few days. This particular protocol, which is routinely used in farmed cattle, was developed specifically for use with scimitar-horned oryx at SCBI in 2000.

Previous iterations of this procedure relied on anesthesia to keep the oryx manageably calm. However, the same drugs used to dial down pain can also have compromising effects on fertility, including disrupting ovulation or fertilization.

“In general, it’s much better to be able to perform these techniques while not under anesthesia—it’s always a risk,” explains Smithsonian wildlife veterinarian Pierre Comizzoli. “But most of the wild species we deal with are easily stressed, so most of the time, it’s really difficult to handle them.”

And so, to avoid the complications associated with anesthesia, SCBI scientists trained Rizzo to situate herself in a hydraulic restraint that would restrict her movement during the insemination. The procedure was a success, and without anesthetization, Rizzo’s recovery time was also minimized. Her pregnancy lasted about eight months, a typical time frame for the scimitar-horned oryx.

At this critical juncture in the fight to save the scimitar-horned oryx, artificial insemination remains one of the most powerful tools at conservationists’ disposal. Not only does it complement the effectiveness of natural conception, but it also circumvents the risk of sexually transmitted disease and affords scientists a degree of control in ensuring genetic diversity in the growing oryx population. For instance, scientists can now exchange oryx sperm overseas to avoid the consequences of inbreeding within zoo populations, and employ the option of preemptively inseminating females before their release into the wild. The resulting diversity will increase oryx herds’ resistance to disease and other potential hazards in the future.

In their future work, the SCBI will continue to tinker with artificial insemination techniques to increase reproductive success. Rizzo was the only one of eight females who were artificially inseminated last October to become pregnant.

Just under two weeks old, the female calf, who has yet to be named, clocks in at 22 pounds and is reportedly healthy. She is one of several calves to be born at SCBI in the last several years. As she matures into adulthood, she will grow to a height of about four feet, weighing between 200 and 300 pounds on the SCBI’s prescribed diet of hay and herbivore pellets. According to Dolores Reed, an oryx caretaker at SCBI who was present for the insemination and birth, the calf has already begun to tentatively engage with the rest of the herd of 27 oryx at SCBI.

“This gives me a lot of satisfaction,” Reed says. “These animals went extinct in the wild and we’re putting them back. We just added another little piece to help them survive.”

Katherine J. Wu | | READ MORE

Katherine J. Wu is a Boston-based science journalist and Story Collider senior producer whose work has appeared in National Geographic, Undark magazine, Popular Science and more. She holds a Ph.D. in Microbiology and Immunobiology from Harvard University, and was Smithsonian magazine's 2018 AAAS Mass Media Fellow.