Koko, the Bay Area gorilla who knew sign language, dies at 46

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Koko the gorilla, who was born in the Bay Area and mastered sign language, has died. The Gorilla Foundation says Koko died in her sleep Tuesday morning of natural causes at the age of 46 in the Santa Cruz Mountains preserve where she lived.

VIDEO: The life of Koko, the Bay Area's beloved gorilla

"She was showing age-related ailments, slowing down, losing her appetite. Fortunately she passed away peacefully in her sleep," said Gary Stanley, Chief Operating Officer of The Gorilla Foundation.

Koko spent time with celebrities including Robin Williams and was world-famous for her ability to communicate with humans. 

The western lowland gorilla could sign more than 1,000 words.       

She was born at the San Francisco Zoo on July 4, 1971.

The next year, Dr. Penny Patterson started her world-renowned work with Koko teaching her sign language.

Patterson, who founded The Gorilla Foundation, in a video once said, "People ask me if I have any children and I say, 'No, I have 3 gorillas.'"

Stanley says Patterson was the one who broke the news to him about Koko's death.

"My main concern was for Penny. Is she okay? And she was okay," said Stanley.

The phone at his office in Redwood City has been ringing off the hook as people remember the groundbreaking gorilla.

Grieving caretakers there also posted "RIP KOKO" signs in the window.

While gorillas in the wild live to about 35, Stanley says gorillas in captivity live into their 50s.

"It's hit everyone really hard. We were expecting her to live a lot longer," said Stanley.

Since 1979, Koko has lived at a preserve in Woodside.

Outside Thursday, a hand-written note outside the facility read "RIP Koko: Hakuna Matada."

Koko had a companion gorilla Ndume. The Foundation says he signed "sad" and "I know" when he heard about Koko's death.

"The world has gained an insight into the mind of another species that shows us how much like us they are," said Stanley. 

That insight made Koko a media sensation which included covers on National Geographic and her own sign language app, which the foundation hopes will carry on her legacy.