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."
Since rhinos are so large, ultrasound won't work through their bellies or flanks.