A gorilla who learned to communicate in sign language has died at the age of 46.

Western lowland gorilla Koko died at the Gorilla Foundation's preserve in California's Santa Cruz mountains on Tuesday.

Koko was born at the San Francisco Zoo and Francine Patterson began teaching the gorilla sign language that became part of a Stanford University project in 1974.

While at Stanford the project expanded to include a second western lowland gorilla, Michael. In 1979 Koko and The Gorilla Foundation moved to the Santa Cruz Mountains where Ndume joined them as a fellow ambassador for their species.

Koko appeared in many TV documentaries and twice in National Geographic. The magazine's 1978 cover featured a photo that the gorilla had taken in a mirror.

The second issue, in January of 1985, included the story of Koko and her kitten, All Ball. Following the article, the book Koko’s Kitten was published and continues to be used in elementary schools worldwide. Her impact has been profound and what she has taught us about the emotional capacity of gorillas and their cognitive abilities will continue to shape the world.

The Gorilla Foundation said it would continue to honor Koko’s legacy 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.