The world’s last surviving male northern white rhinoceros, Sudan, died Monday at the Ol Pejeta Conservancy (OPC) in Kenya, potentially dooming the species to extinction. The only known surviving members of the species are two females, Najin and Fatu, who are Sudan’s daughter and granddaughter respectively.

The animal was suffering from age-related issues that gave him skin wounds, and also caused degeneration of the bones and muscles. In the last 24 hours before his death, he was suffering greatly and couldn’t even stand, due to an infection in his right hind leg, leading his veterinary team to make the decision to euthanize him.

The species (there is still ongoing debate whether it is a distinct species or a subspecies of the white rhinoceros) is called Ceratotherium simum cottoni and is thought to have gone extinct in the wild over 10 years ago, even though it is still listed as critically endangered (possible extinct in the wild) in the International Union for Conservation of Nature’s Red List of Threatened Species, an entry that was last updated in 2011.

Sudan was used as a poster-boy by OPC during a fund-raising campaign it did last year with Tinder, in which the rhino was called “the most eligible bachelor in the world” and proceeds from which would go toward research on artificial reproductive techniques for the animals. Given his age and other complications, Sudan was unable to mate with either of the two females. And even if that had been successful, there were concerns about the species’ longevity due to inbreeding, and a narrowing gene pool.

Sudan Rhino Sudan, the last male northern white rhinoceros on Earth, died Monday. In this photograph, a warden guards Sudan at the Ol Pejeta Conservancy in Laikipia national park, Kenya, May 3, 2017. Photo: Reuters/Baz Ratner

Genetic material from Sudan was collected before he died, in the hope that medical breakthroughs of the future would allow using that to birth northern white rhinos. These techniques could involve individuals from the closely related species, the southern white rhinoceros (both of these are regarded by some taxonomists as subspecies of the white rhinoceros species), used as surrogates.

After being caught in the wild at the age of 3, Sudan spent much of his life in the Dvůr Králové Zoo in the Czech Republic, which also owns the surviving females of the species. All three animals (and another, who died in 2014) were moved to OPC in 2009 as part of a breeding program, in the hope that a more natural environment may induce the animals to procreate. All surviving northern white rhinos were watched by armed wardens round the clock.

“We on Ol Pejeta are all saddened by Sudan’s death. He was a great ambassador for his species and will be remembered for the work he did to raise awareness globally of the plight facing not only rhinos, but also the many thousands of other species facing extinction as a result of unsustainable human activity. One day, his demise will hopefully be seen as a seminal moment for conservationists world-wide,” Richard Vigne, CEO of the conservancy, said reacting to Sudan’s death.

Some other well-known names also expressed their disappointment.