By Magdalene Mukami

NANYUKI, Kenya

 Sudan, 40, cannot get any of his two female northern white rhinos pregnant. But that could soon mean the end of the entire species.

Weighing more than a ton and a half, the northern white rhino, commonly known as "northern whites," are on the brink of extinction.

"We have five left in the world," George Paul, chief veterinarian at Kenya's Ol Pejeta conservancy – home to three northern whites – told The Anadolu Agency.

"The animals are on life support; we may soon see them disappear from the face of the earth," he said.

Northern white rhinos are considered critically endangered and extinct in the wild, with the last five known animals being kept in captivity.

Ol Pejeta is home to three of them: 42-year-old Sudan, the world's only male northern white; 25-year-old Najin; and 28-year-old Fatu.

The two remaining northern whites can be found at the Dvůr Králové Zoo in the Czech Republic and San Diego Zoo's Safari Park in California.

A sixth northern white, Suni, died last year – under ambiguous circumstances – in her Ol Pejeta enclosure.

In an effort to discourage poaching, the conservancy has dehorned the three remaining rhinos.

"Dehorning is a way of minimizing the risk [of poaching]; it minimizes the risk to their lives," insisted Zachariah Mutai, an Ol Pejeta ranger.

He suggested that, like human fingernails, severed rhino horns eventually grew back.

Rhino poaching has recently been on the rise in Kenya.

Last year, Paul Muya, a spokesman for the Kenya Wildlife Authority, told AA that 19 rhinos had been killed by poachers in 2011, 30 the following year, and 59 in 2013.

Ranger Mutai noted that, ever since the northern whites were brought to the conservancy in 2009, they hadn't produced any viable offspring.

"Sudan is 42 years old and is still very active, but his legs are getting weak and he is unable to mount the females," he told AA.

Conservancy officials have gone so far as to try to mate the southern white rhino – another subspecies of the white rhinoceros – with the two female northern whites. Their efforts, however, were in vain.

In 2013, the International Union for Conservation of Nature estimated that there were some 20,400 southern white rhinos in Africa.

"We are trying, in any way possible, to see if they can do something – without success so far, but we are still hopeful," said Mutai.

He fears the extinction of the northern white is inevitable without the intervention of science.

Paul, the chief veterinarian, said that, despite the successful mating of the rhinos in recent years, there haven't been any conceptions.

"In the last health examination, we found that the animals were physiologically healthy," he told AA.

He noted that, while Fatu had a slightly degenerated uterus that may not be able to support a pregnancy, Najin had the ability to conceive.

According to Paul, the problem lies with Sudan, the male rhino.

"At 42, rhinos are considered really old, so the best we could do for him was to preserve biological samples," he said.

The expert noted that the conservancy's northern white management committee had called for exploring the possibility of assisted reproductive techniques.

"It's high time to consider the possibility of applying assisted reproductive tactics – though we may be too late," he told AA.

The assisted reproductive techniques stand for procedures such as artificial insemination.

George told me that they had tried all that but conception has never been achieved.

They are yet to try embryo transfer because of scientific limitations,  George said that he was optimistic that one day such methods will come of use to save other endangered species.