National

Koko, the gorilla famous for knowing sign language, dies in her sleep

The beloved gorilla Koko, famous for being fluent in sign language, passed away in her sleep Tuesday in Woodside, California. The western lowland gorilla was 46.

Koko was born at the San Francisco Zoo in 1971 and became the star of "Project Koko," an experiment by scientist Penny Patterson and Stanford University in 1974 to teach gorillas sign language in order to learn about their cognitive abilities.

"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, a non-profit created to buy Koko from the San Francisco zoo, said in a statement.

Koko knew over 1,000 signs and could understand about 2,000 English words, even modifying words to express new meanings about how she was feeling. Koko was also a painter, choosing her colors and paint brushes with care.

The gorilla was featured on the cover of National Geographic twice in her lifetime, once taking a picture of herself in a mirror and another time holding her pet kitten. After hearing the news that Robin Williams died, a friend of Koko's, the highly intelligent gorilla was somber all day.

"Koko’s capacity for language and empathy has opened the minds and hearts of millions," the foundation said in statement.