How to Impregnate a Rhino

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.

First, they lead each rhino into a specially designed chute with an open panel at the rear. Since rhinos are so large, ultrasound won’t work through their bellies or flanks. You have to go in through the rectum, which means there is, quite literally, a lot of shit in the way. The rhinos’ trainers have conditioned each animal to defecate in the yard before the procedure, but Pennington and Durrant still have to spend a fair amount of time scooping poop out. Once they’re done, they insert a rounded probe that’s the size of two fingers, and is taped to a foot-long long PVC pipe.

The pipe, I suggest to Pennington, surely means that your arm’s not going in there.

“Oh, it is,” she tells me. A rhino’s ovaries lie deep within its body, and the left one, for some reason, lies deeper than the right. For the left ovary, Pennington typically ends up shoulder-deep in rhino. The animals aren’t sedated during any of this, but they seem unperturbed. “I’m sure the sensation is very odd at first,” says Pennington, “but the size of their fecal boluses are definitely larger than the diameter of our arms.”

It helps that white rhinos are docile and sociable by nature. “They’re like big puppy dogs, who just want to be petted,” says Pennington. “They’ll kick a leg out when you’re scratching their belly, and you’re afraid they’ll fall over because they really get into it.” Even for a white rhino, Victoria is affectionate and easy to train, Pennington says. She’s also particularly independent. Unlike some of her peers, who have such strong bonds that they have to be moved as a group, Victoria will readily show up for a medical scan on her own.

Such scans have been invaluable. They revealed that five of the six females were “flatliners”—that is, they weren’t releasing eggs on their own, and had to be induced with a hormone injection. The team spent a full year working out how best to do this. And when they tried the treatment on Victoria, she responded beautifully. On March 22, during one of her ultrasound checkups, the team saw signs of eggs. It was time to add the sperm.

Jill Van Kempen, Victoria’s primary trainer, led her out of the ultrasound chute and sedated her. Meanwhile Pennington donned a long glove. With an audience of around 20 people, including vets, students, and trainers, “I guided a catheter through her cervix,” Pennington says. “I just made it sound way easier than it is.”

Pennington had artificially inseminated horses and cows before, so she knows how to find the entrance to a cervix by touch alone. But a rhino’s cervix not only sits at the end of a much larger vagina, but is also incredibly convoluted. The cervix zigs and zags like a steep mountain road. To navigate these switchbacks, Pennington used a catheter with a 45-degree kink in it, and slowly steered it around the sharp corners.

A rhino’s cervix is also very long: When Pennington first attempted this procedure, on a different female, she ran out of catheter before she reached the uterus. But Victoria, who was smaller, posed no such problem. After 10 minutes, the catheter was in and Pennington was out. Her colleagues thawed out a precious sample of frozen sperm from a southern white male, and sent it through the catheter. “It was a perfect procedure,” she says.

Still, no one on the team actually expected it to work on the first go. Eighteen days later, when they were giving Victoria her routine ultrasound exam, none of them expected to see an embryo. “I remember saying: I’ll hurry up. We have more rhinos to get to,” Pennington recalls. “Then I saw it. I got really quiet because I didn’t want Victoria to hear me and get scared.”

Victoria was actually carrying a calf when she arrived at San Diego, but sadly, the infant was stillborn. For now, her current fetus seems healthy, and the team is scanning it once a week to collect every bit of data they can. It now has a discernible head. Its little heart contracts ferociously around 160 to 200 times a minute, and the team plays a game where they all try to count the rapid beats. Very little is known about the specifics of rhino pregnancies, so such information is priceless.

Only a handful of rhinos from two species—the Indian and southern white—have been successfully bred through artificial insemination. The process is still inefficient. By streamlining and refining it, the San Diego team is learning tricks that they can then share with zoos and sanctuaries around the world. When I spoke to Durrant, she was in South Africa doing just that. “Victoria getting pregnant was a validation of those techniques,” she says. “It really galvanized us as a team, and pulled us together in a whole new way.”

Currently, poachers kill around three rhinos every day, and if those rates continue, assisted reproduction won’t save these animals. Still, it might extend a lifeline to species whose populations are already precariously low. There are, for example, fewer than 100 Sumatran rhinos left in the wild, and only 60 or so Javan rhinos.

Though the insemination was a success, the team’s bigger goal of saving the northern white rhino is still a distant one. “Saving the northern white is an ambitious goal but you’ve got to be ambitious about it,” Pennington says. “I don’t think anyone takes it lightly. Everyone involved is incredibly dedicated, and that’s what makes me optimistic.”

White rhinos have a gestation time of around 16 months, so Victoria’s calf is due in July 2019. Perhaps it will be the first of many. Buoyed by their success, the San Diego team is now planning to artificially inseminate the other five females when they get the chance. “We asked the trainers: How do you feel about six calves? Do you want to stop after two?” Pennington says.

“They said: No, bring it on! Six!”