Koko the gorilla, who learned sign language, has died at the age of 46 on Tuesday 19th June 2018. It was thought that Koko could understand more than 1,000 signs and around 2,000 English words.
Her favourite book was the Three Little Kittens which she asked Francine Penny Patterson the animal psychologist, carer and instructor to read repeatedly. It only made sense when Koko asked for a pet kitten which she named All Ball. Koko gained popularity when a book was released called Koko’s Kitten in 1985, which detailed her caring and grieving for the cat that was hit by a car.
The Gorilla Foundation said “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.”
I’ve personally been a fan of Koko since I was little and was upset to hear this loss. It amazed me how Koko could use sign language, a concept that was so foreign to me. I give my full respect to Penny and the team, for taking the time to teach Koko sign language. Koko's passing is a true loss and hopefully has raised awareness for endangered species.
Source
http://www.koko.org/gorilla-foundation-sad-announce-passing-our-beloved-koko
https://www.koko.org/books-kokos-kitten