The world's last male northern white rhino, Sudan, has died after "age-related complications," researchers announced Tuesday, saying he "stole the heart of many with his dignity and strength."

A statement from the Ol Pejeta Conservancy in Kenya said the 45-year-old rhino was euthanized on Monday after his condition "worsened significantly" and he was no longer able to stand. His muscles and bones had degenerated and his skin had extensive wounds, with a deep infection on his back right leg.

Euthanasia was "the best option, given the quality of his life had deteriorated to a point where it was unfair to him," chief conservation officer Samuel Mutisya told The Associated Press.

The rhino had been part of an ambitious effort to save the subspecies from extinction after decades of decimation by poachers,with the help of the two surviving females. One is his 27-year-old daughter, Najin, and the other is her 17-year-old daughter, Fatu.

His death won't have an impact on the efforts to save the subspecies, as the focus turns to in vitro fertilization techniques using stored semen from other dead rhinos, and eggs extracted from the two remaining females.

"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," said the conservancy's chief executive officer, Richard Vigne.

Sudan was something of a celebrity, attracting thousands of visitors. Last year he was listed as "The Most Eligible