The death of a 90-year-old rare female Yangtze giant soft shell turtle in a zoo in China means almost certain extinction for one of the world’s rarest species, according to the Associated Press. One of the remaining three male turtles lives at the Suzhou zoo, where the female died. The other two live in Vietnam. Zoologists collected the female turtle’s ovarian tissue for research. She had undergone a fifth attempt at artificial insemination shortly before she died, according to state-run People’s Daily. Associated Press reports that Chinese and foreign experts are investigating the cause of the endangered turtle’s death.