Sudan, the 45-year-old northern white rhinoceros and the last male of his subspecies, died Monday, according to wildlife conservation group WildAid.

After suffering from age-related illness and a series of infections, Sudan’s keepers at the Ol Pejeta Conservancy made the difficult decision to euthanize the animal. There are only two northern white rhinos left, a mother and daughter named Najin and Fatu, are aged and infertile, leaving only a slim chance that the subspecies can avoid extinction.

Conservationists have been desperately trying to preserve the northern white rhinos, a subspecies of white rhinoceros. The subspecies population has been declining rapidly over the last decade due to a rise in poaching, with 1,000 rhinos killed by poachers every year, according to WildAid. The southern white rhino, the other subspecies of white rhino, is down to 20,000.

The only hope for preserving the northern white rhino would be to take stored rhino semen and eggs from now-dead animals and try to achieve in vitro fertilization with a southern white rhino female, according to WildAid. But a successful rhino IVF treatment has not yet been achieved, and developing new IVF techniques for different species is not an easy task.

“We at Ol Pejeta are all saddened by Sudan’s death. He was an amazing rhino, 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,” said Ol Pejeta Conservancy CEO Richard Vigne in a press release. “One day, his demise will hopefully be seen as a seminal moment for conservationists worldwide.”

All species of rhinoceroses are currently threatened or endangered, with just 5,000 black rhinos, 3,500 Indian one-horned rhinos, about 100 Sumatran rhinos, and an estimated 60 Javan rhinos, according to WildAid. If the ivory trade and wildlife poaching isn’t dramatically curbed, Sudan’s death could simply mark the beginning of the end for this magnificent species.

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