The survival of the world's population of northern white rhinos rests on the shoulders of Sudan, the sole surviving male of the subspecies — and the armed rangers who guard him 24 hours a day.

Sudan lives in Kenya's 90,000-acre Ol Pejeta Conservancy, which is also home to two female northern white rhinos.

Forty armed rangers patrol the conservancy, and while the 40-year-old rhino isn't constantly surrounded by rangers, his security detail is never far from where he and the females roam.

"We try and let our rhinos be wild as much as possible without human interaction," Eldoie Sampere, the conservancy's marketing manager, told GrindTV.

Sudan has been fitted with a radio transmitter so he's easy to locate, and his horn has been removed as a further precaution.

In 1989, Namibia de-horned many of its rhinos in an attempt to deter poaching, and none of the animals were poached. According to Save The Rhino International, rhinos dehorned in certain Zimbabwe conservancies have a 29 percent higher chance of survival than horned ones.

female northern white rhino

Photo: Tony Karumba/Getty Images

Poaching the last of the species

Rhino horns are big money for poachers, often fetching $30,000 per pound.

Powdered rhino horn is prized in Asia because of ancient beliefs that it can cure everything from fevers and snakebites to seizures and cancer. However, rhino horns are mostly keratin, the same material that makes up human hair and fingernails.

From 1960 to 1980, the population of northern white rhinos plummeted from 2,000 to only 15 because of poaching, and by 2009, the last wild members of the subspecies had been killed. That year, four of the animals —Sudan, the two females and another breeding male — were brought to Ol Pejeta from a Czech zoo in hopes that living a more natural life would encourage breeding.

In 2012, female Najin and male Suni mated, but there was no pregnancy.

Then in October, Suni died of natural causes, and in December, 44-year-old Angalifu — the only breeding male of the subspecies left besides Sudan — passed away at the San Diego Zoo.

Now, only five northern white rhinos remain: the three at Ol Pejeta and two that live in zoos. However, all five are considered to be past their reproductive years, and scientists say there's a limited chance of any more of the subspecies being born.

northern white rhinos

Photo: Tony Karumba/Getty Images

What will become of the species?

Conservationists say it's possible one of the Ol Pejeta females could mate with an introduced southern white rhino, a closely related subspecies, to produce hybrid calves. However, scientists say this wouldn't be ideal as it would preserve only some of the northern white rhino's genetics.

The subspecies could also be brought back from the brink of extinction in a laboratory.

In February, the San Diego Zoo — which is home to a female northern white rhino — received a $110,000 donation to work on the genome sequencing of the northern and southern white rhinos.

San Diego's Frozen Zoo has genetic material from 12 northern white rhinos, including sperm and testicular tissue from the male that died in December. The zoo's long-term goal is to create an embryo that could be brought to term by a female southern white rhino.

For now though, Sudan will spend his days in Kenya surrounded by armed rangers while Ol Pejeta raises funds to keep its rangers safe on the job.

"With the rising demand for rhino horn and ivory, we face many poaching attempts and while we manage to counter a large number of these, we often risk our lives in our line of duty," Simon Irungu, an Ol Pejeta ranger, told World of Animals.

The conservancy has launched a GoFundMe campaign with hopes of raising about $110,000.

Related on MNN: