Koko the Gorilla — known for her ability to communicate with humans using over 2,000 hand signals — died Tuesday in her sleep in Woodside, California. She was 46.
"Koko touched the lives of millions as an ambassador for all gorillas and an icon for interspecies communication and empathy. She was beloved and will be deeply missed," The Gorilla Foundation said in a statement announcing her death.
Who is Koko the Gorilla?
Koko the Gorilla was born at the San Francisco Zoo in 1971. Animal psychologist Francine (Penny) Patterson, then studying for her PhD, convinced the zoo to lend her the then-infant Koko the Gorilla for research. She wanted to explore apes’ ability to learn human sign language.
The pair soon bonded like "mother and daughter," Patterson once said. "You just don't expect a gorilla to be that way," she said in a 2016 BBC documentary.
Koko the Gorilla with Robin Williams
Koko the Gorilla was a celebrity — and she attracted the attention from other human celebrities, like Flea from the Red Hot Chili Peppers. He gave her his bass during one visit and she attempted to play the instrument.
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Her most memorable visit was with Robin Williams in 2001. Williams fearlessly interacted with the large primate, playing and laughing with her. At one point Koko the Gorilla even pulled up his shirt to play with his chest.
She was devastated after his 2014 death.
"Robin’s ability to just 'hang out' with Koko, a gorilla, and in minutes become one of her closest friends, was extraordinary and unforgettable," Patterson wrote in a tribute post to Williams after he died by suicide.
Did Koko the Gorilla ever have a baby?
In 1975, the San Francisco Zoo — worried about the gorillas’ place on the endangered species list — demanded that Koko the Gorilla breed or be returned to the zoo. Another ape, Michael, was brought in and also taught sign language. However, their relationship was more like siblings than mating partners. Michael passed away in 2000.
Another gorilla, Ndume, was also brought in to make Koko a mother — something she expressed wanting by signing the word for baby.
"Ndume came to live with Koko when they were both teenagers (she selected him from a video), and hence was considered a much more likely mate," the organization wrote on its website. "Although Koko and Ndume do get along very well and spend lots of time together, Koko has still not initiated mating."
Koko the Gorilla never had a baby, though she was "mother" to many kittens throughout her life. Her first, named All-Ball, died in an accident.
Koko the Gorilla and sign language: The controversy
Patterson was adamant that Koko could interact with humans using sign language and expressed human-like emotions. She even turned away during a scene in her favorite movie because it scared her.
She also played practical jokes, once tying Patterson’s shoelaces together before signing the word for "chase."
Another primate expert, Herbert Terrace, dismissed Patterson’s work with Koko, claiming that she — and other primates like her — were only reacting to their human teachers. Terrace also added that Patterson refused to recognize it because she was an "overzealous mother who is very proud of her surrogate children and tends to project meanings onto those children that may not be apparent to another observer."
Patterson — who never married or had children of her own — was undeterred and cared for Koko the Gorilla like a daughter for the primate’s entire life.
"The foundation will continue to honor Koko's legacy and advance our mission with ongoing projects including conservation efforts in Africa, the great ape sanctuary on Maui, and a sign language application featuring Koko for the benefit of both gorillas and children,” the Foundation added in a statement.