Koko, the famous western lowland gorilla who communicated with humans through sign language, died in her sleep Tuesday. She was 46.
Throughout her life, Koko's abilities made headlines. After she began communicating with humans through American Sign Language, she was featured by National Geographic — and she took her own picture (in a mirror) for the magazine's cover.
That cover came out in 1978, seven years after Koko was chosen as an infant to work on a language research project with the psychologist Francine "Penny" Patterson. In 1985, the magazine profiled the affectionate relationship between the gorilla and her kitten: Koko and All Ball.
In 2001, Koko made a fast friend in comedian Robin Williams, trying on his glasses, showing him around and getting him to tickle her. Then they made faces at each other — and the gorilla seemed to recall seeing Williams in a movie. Years later, in 2014, Koko was one of many who mourned Williams' passing.