Imam, the last Sumatran rhinoceros in Malaysia, died Saturday.

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The 25-year-old rhino, died of natural causes. She had uterine tumors that were discovered after she was rescued in 2014. She was in significant pain from growing pressure on her bladder from the tumors.

Still, her death came sooner than expected.

“Despite us knowing that this would happen sooner rather than later, we are so very saddened by this news,” said Sabah Environment Minister Christina Liew.

Her death comes six months after the death of Tam, the country’s only male rhino. The pair were supposed to mate, however because of his infertility and her cancer, they were unable.

Researchers saved genetic material from both the rhinos to use for future possible reproduction. Scientists in Malaysia have tried unsuccessfully since 2011 to breed the species through in-vitro fertilization, Reuters reported.

The Sumatra rhino is the smallest of the rhinoceros species and is the only rhino with two horns.

Due to poaching and deforestation, the dwindling Sumatran rhino population is estimated to be between 30 and 80, mostly living in isolated groups in the wild in Sumatra and Borneo.

The Associated Press contributed to this report.