Staving off extinction is an incredible challenge and race against time. In the case of the northern white rhino, the situation is about as dire as it could be.
"There has been recorded mating between different pairs over the last few years, but not conceptions," said George Paul, the deputy veterinarian at the conservancy. "Based on a recent health examination conducted, both animals have a regular estrus cycle, but no conception has been recorded."
In the absence of a natural solution, international experts are exploring alternatives to keep the subspecies present in the animal kingdom. One potential option, though it would not be 100 percent genetically pure, is to have Sudan mate with a southern white rhino, another rhino subspecies that is not endangered.
Other experts say a more promising route would be to pursue alternative reproductive techniques, such as in vitro fertilization.
"Realistically, we are looking at these animals dying in the next decade or so. But hopefully, using artificial methods of reproduction, we might be able to bring them back in the future," Paul said. "This might mean that it will happen when the current animals are already deceased, but it could happen."
A total of five northern white rhinos remain in captivity, including the three in Kenya and one each at zoos in San Diego and the Czech Republic.
Below is a video of Sudan, Fatu, and Najin at the Ol Pejeta Conservancy.