On social media, the San Diego Zoo posted a heartfelt farewell to Satu, one of the complex's four orangutans. The monkey, according to reports, was adored by all of the staff and had been severely ill.

"The San Diego Zoo family is devastated to learn of the death of male orangutan Satu. The much-loved monkey was under veterinary treatment for a severe illness, with preliminary post-mortem tests indicating malignancy.

They also revealed that she recovered well from a recent medical checkup but that her condition deteriorated subsequently and that the staff's attempts to revive Satu were failed.

"Wildlife care professionals, wildlife health team, volunteers, and guests will be deeply missed by this fascinating primate and member of our family," they said in a Facebook post.

Satu, along with his contemporaries Indah, Aisha, and Karena, was born in 1995 and died at 26. He was one of four orangutans residing at the San Diego facility.

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