The zoo was the only place to breed northern white rhinos successfully in captivity, and Sudan fathered a daughter, Najin.
Together with Suni, another male northern white rhino, this family was returned to Africa in 2009.
They shared their enclosure with southern white rhinos, a subspecies that still survives in reasonable numbers in the wild.
In 2014, Suni died, leaving Sudan as the last male northern white rhino.
A male rhino has to fight a female first and win that fight before he is allowed to mate.
If there was no poaching, there would still be good wild populations of northern white rhinos.
In Berlin, scientists have managed to create an embryo using northern white rhino semen and southern white rhino eggs. »