He spends his days surrounded 24/7 by armed guards.
At 42, he's the oldest northern white rhino to have lived in captivity and it shows. His left eye is nearly blind, his hind legs so weak he can't mount the remaining females. His sperm count is low, and the
His subspecies has spent generations evolving to their habitat - their mouths shaped to suit the local vegetation, their hides more resistant to specific parasites. But they could not prepare for man's wars. They lived in battle zones - Congo, the Central African Republic, Sudan - and were killed for horns that could be turned into cash and weapons (in SE Asian markets, rhino horn sells for around $71,000 per kilo!).
In the 1960s, northern whites were estimated at around 2000. When Sudan was captured at age 3, and taken to a Czech zoo, his kind were listed as 'endangered'. Conservationists believed they could still save them, but no one did anything. So they were wiped out in the wild, first in the Central African Republic, then in Sudan.
By 2003, there were less than two dozen left in the wilds of DRC's Garamba National Park. After the govt refused to move them to safety in Kenya, they too were poached. In 2008, northern white rhinos were declared extinct in the wild. Only those in captivity remained.
Other rhino subspecies have suffered the same fate: the western black rhino and a subspecies of Javan rhino in the wilds of Vietnam were declared extinct in 2011.
Scientists set the minimum requirement for a viable breeding population of a subspecies at around 2000. Right now, there are five. Two of the four remaining females are in a San Diego zoo, too old to mate.
The two other females are Sudan's own offspring. Yet, despite in-breeding being common among wild rhinos, his daughter Najin (25) and granddaughter Fatu (14) will no longer have him.
In an ironic situation created by human plunder and blunder, the best chance for survival now rests with human intervention. Conservationists are planning to create the world's first test-tube rhino, through in-vitro fertilisation of Najin or Fatu's eggs with sperm harvested from Sudan. The tiny embryo could then be implanted into a southern white rhino, a surrogate mother from a closely related subspecies.
It has never been done before. But it's the only choice left.