The last known Sumatran rhinoceros in Malaysia died Saturday after a battle with cancer, leaving the species officially extinct in the country. There are now only an estimated 80 Sumatran rhinos left in the world, with the species labeled as "critically endangered," according to the World Wildlife Fund (WWF).

The rhino named Iman died of natural causes due to shock in her system, the Wildlife Department in eastern Sabah state on Borneo island told The Associated Press. She had been suffering from uterine tumors since she was taken into captivity in early 2014. She was reportedly 25 years old.

The rhino was cared for by the Borneo Rhino Alliance (BRA) and lived within the Tabin Wildlife Reserve in Sabah — a Malaysian state on the island of Borneo. The BRA posted a heartbreaking goodbye to their last rhino on Facebook.

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"You were also the sweetest soul, who brought so much joy and hope to all of us," wrote the BRA on Saturday."We are in so much pain right now, but we are thankful that you are no longer in pain. May we be as strong as you in our urgent fight to save your species. May we be as courageous as you to never give up."

Dear Iman, You are the 5th Sumatran rhino the world has lost in the past 5 years, and the very last rhino in Malaysia.... Posted by Borneo Rhino Alliance on Saturday, November 23, 2019

The death came just six months after the nation's last male Sumatran rhino died in May. A female rhino also died in captivity in 2017.

Attempts to breed the rhinos have been unsuccessful. Only two captive females have managed to reproduce in the last 15 years. However, state authorities have harvested their cells for potential reproduction.

Sumatran rhinos are the smallest of the five living species of rhinoceroses, according to the WWF. The animals' population has decreased dramatically as a result of habitat loss and poaching.