NAIROBI, Kenya -- 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 and the Dvůr Králové Zoo 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.

The white rhino had been part of an ambitious effort to save the subspecies from extinction with the help of the two surviving females. 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 CEO, Richard Vigne.

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Sudan was something of a celebrity, attracting thousands of visitors. Last year, he was listed as "The Most Eligible Bachelor in the World" on the Tinder dating app in a fundraising effort.

Sudan at the Ol Pejeta Conservancy in Laikipia, Kenya, in June 2017. Reuters

The last male northern white rhino had been born in Sudan, taken to a Czech zoo and then transferred to Kenya in 2009. Rangers caring for Sudan described him as gentle.

The rhino "significantly contributed to survival of his species as he sired two females," the conservancy said. "Additionally, his genetic material was collected yesterday and provides a hope for future attempts at reproduction of northern white rhinos through advanced cellular technologies."

"One day, his demise will hopefully be seen as a seminal moment for conservationists world wide," Vigne added.

Sudan's death "is a cruel symbol of human disregard for nature and it saddened everyone who knew him. But we should not give up," said Jan Stejskal, Director of International Projects at Dvůr Králové Zoo. "We must take advantage of the unique situation in which cellular technologies are utilized for conservation of critically endangered species. It may sound unbelievable, but thanks to the newly developed techniques even Sudan could still have an offspring. We will be happy for everyone who will help us in our joint effort."

Northern white rhinos once roamed parts of Chad, Sudan, Uganda, Congo and Central African Republic, and were particularly vulnerable because of the armed conflicts that have swept the region over decades.

Other rhinos, the southern white rhino and another species, the black rhino, are under heavy pressure from poachers who kill them for their horns to supply illegal markets in parts of Asia.

Roughly 20,000 southern white rhinos remain in Africa. Their numbers dipped below 100 around a century ago, but an intense effort initiated by South African conservationist Ian Player in the mid-20th century turned things around.