One of the last five Northern White Rhino left in the world has died.
Nabire, a 31-year-old female, died at the Dvur Kralove zoo in the Czech Republic on Monday evening of a ruptured cyst.
Her death leaves just three females and one male alive; one of them at the San Diego Zoo and three at the Ol Pejeta Conservancy reserve in Kenya.
The sub-species has been on the brink of extinction for years because of hunting and habitat loss.
"The pathological cyst inside the body of Nabire was huge. There was no way to treat it," said Jiří Hrubý, a rhino curator at the zoo.
Nabire was born at the Czech Zoo and was one of the last hopes for the animal. She was plagued with reproductive cysts, but conservationists had long hoped to harvest eggs from her healthy left ovary to use for in vitro fertilization (IVF).
One attempt was made to do this while Nabire was still alive. After her death the ovary was removed and taken to a specialised lab in Italy.
If it is possible at all, any IVF attempt will now almost certainly require the implantation of a Northern White Rhino embryo in the closely related Southern White Rhino, which are more numerous.
In 2009, four rhinos were moved from the Dvur Kralove Zoo to Kenya hoping that the natural environment there would help them breed, but the plan yielded no new births.