Koko, a western lowland gorilla born on the Fourth of July in 1971 at the San Francisco Zoo, was 46 when she died in her sleep on June 12, the statement said. She was living in a preserve located in the Santa Cruz Mountains.
"Koko touched the lives of millions as an ambassador for all gorillas and an icon for inter-species communication and empathy," the statement said. "She was beloved and will be deeply missed. ... 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."
Koko's ability with sign language came about through the efforts of Stanford-educated psychologist and Gorilla Foundation founder Francine "Penny" Patterson. In 1972, Patterson began teaching her new student a system she called Gorilla Sign Language, the statement said.
Koko learned more than 1,000 signs and used her abilities to christen her Manx kitten companion All Ball and to mourn the loss of All Ball with the words "cat," "cry" and "have-sorry," followed by a pause, and then "unattention" and "visit me," according to an National Public Radio story broadcast this week. All Ball died after being struck by a car.
Her animal companions also included two male gorillas: Ndume and Michael. Michael died in April 2000 at the age of 27.
Koko once took a photograph of herself in a mirror and the photo was published on the cover of National Geographic magazine in 1978.
Among the celebrities who visited Koko and whose visits were captured on video were the actress Betty White and the comedian and actor Robin Williams, whose glasses she carefully removed and tried on. In a playful mood, she held hands briefly with Williams, tussled with him, invited him to tickle her, and laughed when he did.
In 2005, two former employees of the foundation sued their former employer, alleging sexual harassment and wrongful termination and claiming that they were routinely pressured to expose their breasts to Koko in order to bond with her. The court sustained the foundation's challenge to the claims and the case was resolved in November 2005.
The foundation is planning to honor Koko's legacy. Among the projects: conservation efforts in Africa, a great-ape sanctuary on Maui, and a sign-language app that features Koko "for the benefit of gorillas and children," the statement said.
