Zookeepers have announced the death of one of the last five northern white rhino left on Monday. The death of Nabiré, a 31-year-old female, means this incredibly rare species is now one step closer to extinction.

Authorities at the Dvůr Králové Zoo in the Czech Republic have confirmed that Nabiré died as a result of a ruptured cyst, which zookeepers say was too large to treat.

“It is a terrible loss. Nabiré was the kindest rhino ever bred in our zoo. It is not just that we were very fond of her. Her death is a symbol of the catastrophic decline of rhinos due to a senseless human greed. Her species is on the very brink of extinction,” said Přemysl Rabas, the director of the zoo, in a statement.

Nabiré was born in 1983 at the Czech Zoo and spent her entire life there as part of a breeding program. Though she was bred in captivity in hopes of saving her species, the large cysts in reproductive organs prevented her from conceiving naturally. Conservationists are now hoping that they can make an embryo by harvesting eggs from her left ovary, which appeared to be healthy. The tissue samples have been taken to a specialized laboratory in Italy.

“It is our moral obligation to try to save them. We are the only ones, perhaps with San Diego Zoo, who have enough of collected biological material to do so. We are aware that our chances are slim, but the hopes are still alive,” Rabas says.

In 1960, there were more than 2,000 northern white rhinos, according to the World Wide Fund for Nature (WWF). Poaching and habitat loss has decimated the population over the last few decades. The WWF describes their survival prospects as “bleak.” The other sub-species of white rhinos, the southern white rhino, almost went exctint 100 years ago, but the population is now relatively protected after successful conservation efforts.

The remaining northern white rhinos are an elderly female called Nola who lives in a zoo in San Diego, and an elderly male called Sudan and two females – Najin and her daughter Fatu – who currently reside in the Ol Pejeta reserve in Kenya. Despite numerous attempts by conservationists in 2006 and 2007, neither Najin nor Fatu have been able to get pregnant.