Lulu died shortly after returning from the Zoo’s hospital, where she was being evaluated for a “myriad of conditions” and a possible cancerous mass located in her neck, officials said.

“She was an excellent and caring mother,” said Kyle Runzel, the San Francisco Zoo’s primate curator. “She was extremely gentle and protective, and was a true favorite among her caretakers, staff, and volunteers. We were so lucky to have her in our lives. She was quite a unique mandrill.”