The Gorilla Foundation, founded in 1976, is a non-profit organization created by Ron Cohn and Dr. Francine "Penny" Patterson, dedicated to a research program in gorilla language. Koko, the "talking gorilla", is arguably the most famous gorilla in the world. She is said to understand more than 1,000 signs based on American Sign Language, and approximately 2,000 words of spoken English. Koko is one of the few non-humans known to keep pets. She has cared for several cats over the years. Ndume was selected by Koko from a group of videotapes shown to her by Patterson, who played several tapes showing male western gorillas. Despite these efforts, Koko and Ndume have not mated, and reportedly they are kept separated from each other.
The Gorilla Foundation keeps two gorillas (silverback Ndume):