(CNN) Sudan, the world's last male northern white rhino, has died. But the effort to save the subspecies from extinction lives on.

For nearly a decade, Sudan lived in a 700-acre enclosure at the Ol Pejeta Conservancy, against the backdrop of the hulking Mount Kenya.

Armed guards protected him 24 hours a day because he belonged to a subspecies on the verge of extinction from poachers. Rhinos are targeted by poachers fueled by the belief in Asia that the horns cure various ailments.

The need to preserve the northern white rhino is dire -- there are no known animals left in the wild.

Old and frail

At 45, Sudan was elderly in rhino years. His daughter Najin, 28, and granddaughter, Fatu, 17, are considered spring chickens.

The elderly rhino was fraught with problems normally associated with age. During his final years, he was not able to naturally mount a female and suffered from a low sperm count, which made his ability to procreate difficult.

"There has been recorded mating between different pairs over the last few years, but not conceptions," George Paul, the deputy veterinarian at the conservancy, said. "Based on a recent health examination conducted, both animals have a regular estrus cycle, but no conception has been recorded."

And if one is not recorded soon, the beloved animal will go extinct.

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Alternative methods to conceive

In a race against time, international experts are resorting to science to try to sustain the subspecies.

The northern white rhino cannot mate with a black rhino, but there is a chance it could mate with a southern white rhino, Paul said. While southern white rhinos are not endangered -- Ol Pejeta has 19 -- they are a different subspecies from the northern white rhino genetically. Though the offspring would not be 100% northern white rhino, it would be better than nothing, experts say.

A committee at the conservancy is also looking at various alternative reproduction techniques, including in vitro fertilization.

"In other countries, success has been achieved with embryo transfer in a different rhino species, thus that, as a technique, can be presupposed to be the most promising," Paul said. "However, consultations are ongoing amongst different reproductive technique experts on the way forward."

Researchers were able to save some of Sudan's genetic material in the hopes of successfully artificially inseminating one of the two females left, said Elodie Sampere, a representative for Ol Pejeta.

They are also retrieving and storing eggs from southern white rhino females in European zoos, and fertilizing them in in vitro conditions, Sampere said. Experts will also retrieve eggs from the last two northern white rhino females in Kenya.

"The plan is now to isolate the potential southern white rhino female surrogates from any males, ensuring they are 'empty' and ready for receiving a northern white rhino embryo in 2018," Sampere said.

Countdown to extinction

Paul said he's optimistic.

"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," he said. "This might mean that it will happen when the current animals are already deceased, but it could happen."

The conservancy acquired the northern white rhinos -- two males and two females -- in 2009 from a zoo in the Czech Republic. Suni, the other male northern white rhino at the conservancy, died last year.

It's now up to Najin and Fatu to help keep the subspecies alive.