For years now, “Extinction Countdown” readers have followed the slow slide toward extinction of the northern white rhino (Ceratotherium simum cottoni). In 2014 we lost two members of the species, bringing the world population down to five. Now word comes that one more has died, leaving only four.

Nabiré, a 31-year-old female, passed away on July 27 at Dvůr Králové Zoo in the Czech Republic, where she has spent her entire life. She had been suffering for years from an untreatable cyst that the zoo recently drained. Even then it weighed an estimated 40 kilograms. She also had cysts in one of her ovaries and and could not give birth due to other abnormalities.

"It is a terrible loss,” zoo director Přemysl Rabas said on the Dvůr Králové Zoo web site. “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.”

Nabiré’s death leaves an elderly female at the San Diego Zoo, plus one male and two females at Ol Pejeta Conservancy in Kenya. All of them spent some if not most of their lives at Dvůr Králové, the only facility that ever managed to breed the species in captivity. Ol Pejeta has spent the past few years trying to breed its rhinos with no success.

Dvůr Králové says Nabiré’s loss is not the end. The zoo has collected her functional ovary and other genetic material and will preserve it all, in case future techniques could enable reproduction or even the resurrection of the species.

Northern white rhinos were hunted to the verge of extinction for their horns, which are valued in traditional Asian medicine. The last wild individuals were killed in Garamba National Park in the Democratic Republic of the Congo in 2006.

Photo: Hynek Glos/ Dvůr Králové Zoo

Previously in Extinction Countdown: