June 21 (UPI) -- Koko, a gorilla who became famous for her ability to communicate in sign language, has died at the age of 46, the Gorilla Foundation said.
The western lowland gorilla died in her sleep Tuesday at the foundation's preserve in California's Sana Cruz mountains, the organization said in a statement.
Koko was born Hanabi-ko -- which mean "fireworks child" in Japanese -- on July 4, 1971, at the San Francisco Zoo. Just three years later, Dr. Francine "Penny" Patterson and Dr. Ronald Cohn moved Koko, a second gorilla named Michael and the project to Stanford University and went on to establish The Gorilla Foundation.
Patterson began working with Koko at a young age to teach her sign language.
The famous gorilla was twice featured on the cover of National Geographic -- first in 1978 with a photo Koko had taken of herself in the mirror and another seven years later with her pet All Ball, an abandoned cat she received one year as a birthday present.
"Koko's capacity for language and empathy has opened the minds and hearts of millions," the Foundation said in a statement. "Koko touched the lives of millions as an ambassador for all gorillas and an icon for interspecies communication and empathy."