Hanabiko "Koko" (July 4, 1971 – June 19, 2018) was a female Western lowland gorilla, cared for by Penny Paterson. She was known for having learned a large number of hand signs from a modified version of American Sign Language (ASL). Koko was able to understand more than 1,000 signs of what Patterson calls "Gorilla Sign Language" (GSL). 