When Parker Pennington first saw the embryo, she gasped—but very quietly.
At the time, as is often the case for her these days, she had her arm fully inside the rectum of a white rhino, and she didn’t want to alarm the animal by yelping excitedly.
In her immersed hand, she held an ultrasound probe, which revealed that the rhino, who goes by Victoria, had a tiny marble in her uterus. She was pregnant. If everything goes well, the marble will grow into a baby, who will greet the world in the summer of 2019, and eventually become a two-ton, two-horned behemoth. But even as a small, grainy orb on a black-and-white screen, its very existence felt miraculous. It meant that Pennington’s very first attempt to artificially inseminate Victoria, just 18 days earlier, had worked.
All rhinos are endangered to varying degrees. The northern white—one of two white rhino subspecies—is in especially dire straits after Sudan, the last surviving male, died in March at the conservancy in Kenya where he lived. Only two females remain, and they are both so inbred that neither of them can reproduce naturally. The only way to save the northern white is through artificial means. Eggs from the two last females could be fertilized in a test tube with Sudan’s frozen sperm, and then implanted into females of the southern white subspecies. That’s never been done before. If that works, they’ll eventually try implanting them with artificially fertilized northern white rhino eggs.
To artificially impregnate a white rhino, you must first work out when she’s fertile. You can do this by scanning her ovaries with an ultrasound machine, to see if any of the egg-producing follicles within them have grown. Pennington takes turns with Barbara Durrant, who directs the San Diego Zoo’s reproductive sciences team, to scan each of the six females, twice a week.